Title of Invention	PHOTOCHROMIC MOLDING COMPOSITIONS AND ARTICLES PRODUCED THEREFROM
Abstract	The invention discloses a polyamide molding composition comprising from 50 to 99% by weight of one or several transparent homopolyamides, one or several copolyamides, or a combination of one or several transparent homopolyamides and one or several copolyamides, selected from the group consisting of: MACM12, MACM14, MACM18, MACM12/PACM12, MACM14/PACM14, MACM18/PACM18, 12/MACMI; from 1 to 50% by weight of one or several further polymers whose glass transition temperature is below 0°C, selected from the group consisting of: MACM36, PACM36, polyamide-12 block copolymer with polyether soft segments, polyamide-12 block copolymer with polyester soft segments or a combination thereof from 0.001 to 2.0% by weight of at least one photochromic dye such as herein described; and also, optionally, further additives selected from the group consisting of: further dyes, stabilizers, processing aids, plasticizers, further polymers, functional additives, or a combination or mixture thereof, wherein the photochromic polyamide molding composition has a transmittance in the unexcited state of more than 80% in the wavelength range from 500 to 700 am if measured in the form of a thin plaque of a thickness of 2 mm, and with a haze of less than 5 if measured in the form of a thin plaque of a thickness of 2 mm. The invention is also for molded articles made with said composition.

Title of Invention

PHOTOCHROMIC MOLDING COMPOSITIONS AND ARTICLES PRODUCED THEREFROM

Abstract

The invention discloses a polyamide molding composition comprising from 50 to 99% by weight of one or several transparent homopolyamides, one or several copolyamides, or a combination of one or several transparent homopolyamides and one or several copolyamides, selected from the group consisting of: MACM12, MACM14, MACM18, MACM12/PACM12, MACM14/PACM14, MACM18/PACM18, 12/MACMI; from 1 to 50% by weight of one or several further polymers whose glass transition temperature is below 0°C, selected from the group consisting of: MACM36, PACM36, polyamide-12 block copolymer with polyether soft segments, polyamide-12 block copolymer with polyester soft segments or a combination thereof from 0.001 to 2.0% by weight of at least one photochromic dye such as herein described; and also, optionally, further additives selected from the group consisting of: further dyes, stabilizers, processing aids, plasticizers, further polymers, functional additives, or a combination or mixture thereof, wherein the photochromic polyamide molding composition has a transmittance in the unexcited state of more than 80% in the wavelength range from 500 to 700 am if measured in the form of a thin plaque of a thickness of 2 mm, and with a haze of less than 5 if measured in the form of a thin plaque of a thickness of 2 mm. The invention is also for molded articles made with said composition.

Full Text	TECHNICAL FIELD The present invention relates to photochromic molding compositions and to articles produced therefrom, e.g. ophthalmic lenses, and also to processes for production of such articles. These are preferably bulk-colored molding compositions, but coloring in a dip-coating bath or by way of another method of introducing/doping the photochromic dye is likewise possible. PRIOR ART Photochromic molding compositions are starting. materials used for production of photochromic articles, e.g. sunglass lenses which undergo reversible tinting on exposure to light, or similar articles. Photochromic means that the dye is converted to an excited state via exposure to light (UV or short-wave VIS) , the unexcited, thermodynamically state and the excited state here having different absorption spectra (cf. definition of Photochromie [Photochromicity] in: R6mpp Lexikon Chemie [Rompp's Chemical Encyclopedia], 10th edition, page 3303, Georg Thieme Verlag, Stuttgart) . The excited state generally has an intense color, whereas the initial form is colorless. The excited dye molecule returns to the unexcited state via. a thermal or radiation-induced reverse reaction. These dyes can be used to produce optical filters whose variability is light-induced, for example by introducing the dye into a plastics matrix (bulk coloring), or by applying a coating with dye onto glass or plastic, (cf., for example, J,F. Rabek in Mechanisms of Photophysical Processes and Photochemical Reactions in Polymers, chapter 10, pages 3 77 - 3 91, for incorporation of such dyes into polymeric matrices). An important application is provided by ophthalmic lenses, e.g. sunglass; lenses, which spontaneously darken when subject to insolation. A plurality of photochromic dyes and/or one or more inert dyes together with the photochromic dye are used in order to give these lenses the desired shade of color. If an. inert dye is used, the lens, even in the non-irradiated state, has an underlying tint or a color, and this reduces transmittance. A significant aspect of such applications is that the number of possible repeats of the reversible photochromic process has been maximized, and that the dye is not irreversibly removed from this cycle by environmental effects (e.g. oxygen) or side reactions (e.g. with the polymer matrix or with additives). A further precondition is that the "switching process" (excitation) and/or the thermal reverse reaction proceed(s) to practical completion within an acceptable period, rf this is not the case, tinting of the lens does not occur on exposure to light (no reduction in transmittance) , and/or the lens retains its tint for a long time after exposure to light. Both are undesired. Marketing of the first photpchromic plastic lenses began as early as 1980. However, numerous improvements in the dyes and in the polymeric matrices had to be achieved before the photochromic system achieved adequate lifetime and satisfactory spectral performance. Initially, 'such plastics lenses were practically entirely based on cast systems, e.g. allyl diglycol carbonate CR39, which is obtainable via polymerization of bisallyl carbonates. Later, lenses based on (meth) acrylates and on polycarbonates also became available, and recently an increasing number of lenses is produced thermoplastically, the materials often used here being thermoplastic polyurethanes (TPU). Some disclosures from the patent literature in the general context of photochromically doped plastics will be described below. There are intentionally no details given of the wide variety of descriptions of systems such as CR39 which are processed in a casting process with crosslinking to give lenses, since the present invention does not encompass such systems. JP-A-63 02783 7 describes a photochromic system in which a PET (polyethylene terephthalate) plastics matrix with which a plasticizer has been admixed (from 2 to 15% by weight) is doped with a photochromic dye. The intention of this selection of the matrix is that the long-term stability of such a layer be improved, under constant exposure to light and heat, and this layer can, for example, be applied to a nylon film. JP-A-01180536 likewise describes a photochromic material intended to be heat-resistant and weather- resistant. It is composed of a plastics matrix composed of a transparent plastic and of an additive which is a polymer having a defined proportion of monomers having hydroxyl groups, e.g. PVB (polyvinyl butyral) or polyvinyl acetate. A wide variety of possible systems is stated as transparent plastic, examples being PMMA, PC, transparent nylon, etc. JP-A-01024740 is like the two abovementioned specifications from the tinted vehicle windshields sector in describing a multilayer structure composed of two glass layers with an intermediate layer which comprises a photochromic material. A plurality of possibilities is stated as transparent material of this intermediate layer, inter alia vinyl resin, acrylic resin, polyester resin, and polyamide resin, Spirooxazines inter alia are mentioned as dyes, and a specific distribution of the dye is emphasized as advantageous. WO 01/49478 describes a photochromic lens which is composed of a PC substrate and of a photochromically doped coating composed of thermoplastic polyurethane (TPU) . This coating is applied to a PC preform in an. in-mold-coating process. BRIEF DESCRIPTION OF THE INVENTION The invention is therefore based inter alia on the object of providing a photochromic material improved in comparison with the materials of the prior art. A particular object is improvement of such materials based on polyamides. This object is achieved in particular by providing a photochromic polyamide molding composition which comprises a proportion by weight of from 50 to 99% by weight of at least one transparent homopolyamide and/or copolyamide, a proportion by weight of from 1 to 50% by weight of at least one further polymer whose glass transition temperature is below 80°C, and also a proportion by weight of from 0.001 to 2.0% by weight of at least one photochromic . dye. This material can. optionally comprise, inter alia, further dyes and/or additives. It is not necessary that photochromic dye has been previously admixed with this material, and it is also possible to use the mixture composed of polyamide and of other polymer with the properties, mentioned in relation to glass transition temperature as initial charge and to introduce the dye into the article, e.g. in a dip-coating bath, after or during production of an article (e.g. production of a lens in an injection-molding process). The further polymer preferably has at least one amorphous phase whose glass transition temperature is at most 80°C. If the further polymer is a block polymer having a soft segment, the glass transition temperature of the soft segment should be below 4 0°C, preferably below 25°C. The term used in this specification "transparent polyamides" is intended to mean polyamides or copolyamides or molding compositions formed therefrom, their light transmittance being at least 70% when the (co)polyamide (in pure form, i.e. without the further constituents stated above of the inventive molding composition) takes the form of a thin plaque (plate), thickness 2 mm. Light transmittance is measured here on a Perkin Elmer uv/vIs spectrometer in the range from 200 to 80 0 run, using round plaques measuring 70 x 2 mm. The transmittance value is stated for the wavelength range from 500 to 700 nm. The round plagues measuring 70 x 2 mm are produced for this purpose by way of example on an Arburg injection-molding machine in a polished mold, the cylinder temperature here being from. 200 to 340°C and mold temperature from 20 to 140°C. Examples of transparent polyamides that can be used for these purposes are polyamides and/or copolyamides as described in DE-A-102 24 947, or DE-A-101. 22. 188, CH-A-688 624 or EP=A-0 725 TOO", or a "mixture" thereof. In relation to transparent polyamides, the disclosure of these documents and the polyamide systems and copolyamide systems mentioned therein are expressly incorporated into this description. One of the advantages of the use of polyamides as main material is that, unlike materials such as CR39 or acrylate which have been used hitherto for production of ophthalmic lenses, these being materials which required traditional casting processes involving polymerization (crosslinking), transparent polyamides (amorphous or microcrystalline) can be processed in simple injection-molding processes with low cycle times, i.e. using low-cost mass production. The inventive polyamide molding composition is therefore also preferably not crosslinkable. It is preferable that the mixture is composed of a proportion by weight of from 70 to 99% by weight, particularly from 80 to 93% by weight, of the transparent homopolyamide and/or copolyamide and of a proportion by weight of from l to 3 0% by weight, particularly from 2 to 20% by weight, of at least one further polymer whose glass transition temperature is below SO or 40°C (i.e. without dye), and the mixture is at the same time likewise preferably in essence transparent in the above sense or no more than 10%, or preferably 5%, less transparent than in the above sense. For components whose optical specification is less demanding, or for components in which the photochromic processes are relevant only in reflection (for example decorative items), lower transparency and even slight haze are also possible. For components with a demanding optical specification, transmittance above 70%, preferably above 80%., in the wavelength range from 500 to 700 run (measured at a layer thickness of 2 mm) -is- preferred and/or haze less than 5 or even 3, and preferably less than 2 (ASTM 1003, layer thickness- 2 mm) . Addition of polyamide-12 (also called polyamide-12), in particular of low-viscosity PA12 (solution viscosity or relative viscosity ηrel - according to DIN EN ISO 307 in a 0.5 weight% solution in m-cresol at 20°C - from 1.5 to 2, preferably from 1.6 to 1.9} can improve haze and photochromic effect. Addition of polyamide-12 and/or polyamide oligomer moreover makes it possible to process the photochromic polyamide molding composition under milder conditions and to incorporate the photochromic dye into the thermoplastic molding composition under milder conditions, and it is therefore possible to inhibit substantially any degradation of the unstable photochromic dye during the extrusion and/or injection- molding process. An example of a suitable polyamide oligomer is a polyamide-12 oligomer, preferably with average molar mass of from 1500 to 25 0 0 g/mol,, particularly preferably having mainly non-condensable alkyl end groups. Various measures can be used to avoid gate marks. Addition of 10% by weight or more of a low-viscosity polyamide-12 can be effective in inhibiting formation of gate marks. Gate marks can likewise be avoided if the ratio of the solution viscosities of the transparent polyamide and of the polymer component whose glass transition temperature is below 80°C is smaller than 1.2, in particular smaller than 1.1. Haze, too, is reduced as the ratio of the solution viscosities of the two polymer components falls, for identical chemical constitution. Addition of polyamide- 12 oligomer makes processing easier overall, by virtue of lower melt viscosity and longer flow path. Although it has been possible for some years to prepare amorphous polyamides, too, in the purity required for optical applications, examples being polyamides of type MACM12 as described in DE-A-196 42 885, these being available from EMS CHEMIE, Switzerland, with trade name Grilamid TR 90, simple addition of a photochromic dye cannot give satisfactory photochromic results in the lenses produced from these pure systems. MACM here represents the compound whose ISO name is bis(4-amino-3-methylcyclohexyl)methane, which is commercially available as the C260 grade of Laromin (CAS No.. 6864-37-5) with trade name 3,3'-dimethyl-4,4'- diaminodicyclohexylmethane. The numeral 12 represents an aliphatic linear C12 dicarboxylic acid (DDA, dodecanedioc acid) , with which the diamine MACM has been polymerized. Surprisingly, it has been found that, contrary to previous experience to the effect that addition of photochromic dyes to transparent polyamides does not give satisfactory photochromic behavior, the inventive material gives, when processed to give photochromic articles, unexpectedly long-lived, i.e. frequently repeatable, reversible photochromic behavior. Furthermore, the preferred dyes are among the most stable photochromic systems. The switching process (excitation) moreover proceeds rapidly and the thermal reverse reaction likewise proceeds almost to completion within a reasonable period from seconds to at most a few minutes. Normally, only pure polyamide materials whose glass transition temperature is below. 100°C, i.e. not those present in the form of a mixture,, exhibit pronounced photochromic behavior, an example being MACM3 6 or PACM3 6, where PACM represents the compound whose ISO name is_his(4-aminGcyclGhexyl)methane, available as Dicykan grade (CAS Mo. 1761-71-3) with tradename 4,4'-diaminodicyclohexylmethane.. However, the defective mechanical or thermal properties of these materials generally make them unsuitable by way of example for ophthalmic lens applications. Addition of a further polymer to a transparent (co)polyamide alongside the dye is possible. However, these polymers and the resultant mixture (blend) are subject to stringent requirements, particularly for ophthalmic lens applications, and admixture normally results in haze in the blend. However, optical properties (transmittance, haze, Abbe number) of the mixtures (blends) should not be substantially below the level of the pure polyamides. The photochroraic process should have good kinetics (darkening and fading within period from seconds to a few minutes, preferably within from 20 to 60 seconds) and continue over a long lifetime. This is the case with the proposed materials and with the articles produced therefrom. As previously mentioned, these good properties of the bulk-colored articles also occur when the article is manufactured from the blend without dye and the dye is introduced after the initial molding of the article, e.g. in a dip-coating bath. The presence of the other polymer with low glass transition temperature alongside the transparent polyamide provides an environment for the photochromic dyes permitting the reversible changes of configuration and/or of conformation which mostly occur during excitation of the dyes and which are generally required for the color change. In one first preferred embodiment, the polyamide molding composition is one where the glass transition temperature of the further polymer is below 3 0°C, preferably below 25°C. This can give ideal photochromicity kinetics. Good values are obtained particularly when the glass transition temperature of the further polymer is below 0°C, preferably in the range from (-60) - (-20)°C. Another preferred embodiment with excellent kinetics is one wherein the further polymer is a polyamide based on cycloaliphatic diamines and aliphatic dicarboxylic acids having from 6 to 40 carbon atoms., particularly preferably having from 20 to 3 6 carbon atoms, the cycloaliphatic diamine preferably being MACM and/or PACM, and the entire polyamide particularly preferably being MACM3 6 and/or PACM3 6, and/or wherein the further polymer is a block copolymer having soft segments, where the glass transition temperature of the soft segments is preferably below 25°C. The further polymer can, for example, be a polyamide block copolymer having soft segments, preferably a polyamide-12 block copolymer, the soft segments here preferably being polyether soft segments and/or polyester soft segments and/or polysiloxane soft segments and/or polyolefin soft segments and/or polyacryiate soft segments. Preferred polyether segments are those based on the monomers ethylene oxide and/or propylene oxide and/or tetrahydrofuran. Possible other further polymers are also polyester elastomers having soft segments and TPU elastomers having soft segments, both of these being as previously described at an earlier stage above in connection with polyamide block polymers. It is also possible to use other further polymers, as long as they meet the glass- transition temperature conditions stated above, examples being acrylate polymers, methacrylate polymers (particularly preferably having long pendent groups), polycarbonate copolymers, styxene copolymers (preferably based on acrylonitrile, butadiene, acrylate, methacrylate), polyolefins, particularly grafted, ethylene copolymers (based on propene, butene, pentene, hexene, octene, decene, undecene, butadiene, styrene, acrylonitrile-, -isop-rene-, isobutylene, or being derivatives of (meth)acrylic acid, vinyl acetate, tetrafluoroethylene, vinylidene fluoride, hexafluoro- propene and 2-chlorobutadiene), polyisobueylene, polybutyl acrylate, and others. In one preferred embodiment, the transparent horaopolyamide and/or copolyamide is a polyamide based on cycloaliphatic diamines and on aliphatic dicarboxylic acids having from 6 to 3 6 carbon atoms, or is a mixture of such homopolyamides and/or copolyamides. Excellent transparency values with good photochromicity are obtained by way of example when the cycloaliphatic diamines are MACM and/or PACM and/or when the aliphatic dicarboxylic acid is an aliphatic dicarboxylic acid having 10, 12, or 18 carbon atoms. For example, the transparent polyamide can be a homopolyamide selected from the group of MACM12 (e.g. Grilamid TR 90, cf. text further below), MACM18, and/or is a copolyamide selected from the group of MACM12/PACM12, MACM18/PACM18. It is preferable that the refractive index of such systems is greater than or equal to 1.50, the Abbe number being greater than or equal to 40 and the density being smaller than or equal to 1.1 g/cm3. Another advantageous possibility is that the transparent homopolyamide and/or copolyamide is a polyamide based on aromatic dicarboxyic acids having from 8 to 13 carbon atoms or is a mixture of such homopolyamides and/or copolyamides, preferably based on lactams and/or aminocarboxylic acids, where the aromatic dicarboxylic acids are by way of example TPA (terephthalic acid) and/or IPA (iscphthalic acid) . The transparent homopolyamide and/or copolyamide can advantageously be a polyamide selected from the group of: 6I6T, TMDT, 6I/MACMI/MACMT, 6I/6T/MACMI, MACMI/MACM3 6, 61, lactam-containing polyamides, such as 12/PACMX, 12/MAGMI, 1-2-MACMT;6-/PACMT, 6/6I-6/IPDT, or a mixture thereof. The polyamides are designated pursuant to ISO 1874-1. Each I here represents isophthalic acid and each T here represents terephthalic acid, TMD represents trimethylhexamethylenediamine, IPD represents isophoronediamine. It is advantageous and possible that the transparent homopolyamide and/or copolyamide is a polyamide based on at least one dicarboxylic acid and on at least one diamine having an aromatic ring, preferably based on MXD (meta-xylylenediamine), where the dicarboxylic acid can be aromatic and/or aliphatic, the material preferably being 6I/MXDI. It is preferable that the refractive index of such systems and generally of the transparent homopolyamide and/or copolyamide is greater than or equal to 1.59, the Abbe number being greater than or equal to 25 and the density being smaller than or equal to 1.3 g/cm3. It is preferable that the solution viscosity or relative viscosity ηrel (according to DIN EN ISO 1528-1 or DIN EN ISO 307) is from 1.3 to 2.0, in particular from 1.40 to 1.85. The glass transition temperature Tg of the transparent homopolyamide and/or copolyamide is moreover normally above 9 0°C, preferably above 1100C, particularly preferably above 13 0°C. Another preferred embodiment is one wherein the photochromic dye is a dye which is reversibly excitable with DV or short-wave VIS, preferably being a dye based on spirooxazines. Excitable means that it can be excited to a state in which its absorption spectrum alters in such a way that absorption of visible light takes place, when the dye has been embedded in the matrix composed of polymer, i.e. in the inventive blend composed of transparent polyamide and of other polymer with the glass transition temperature stated above. The achievable filter effect can be adjusted widely in the visible region of the spectrum via the selection of the photochromic dyes and adjustment of the concentration. It is therefore possible to achieve a completely reversible reduction to 40% or even 10% of the original transmittance (generally from 80 to 92%) {in each case measured on a plaque of thickness 1 or 2 mm with parallel sides). Other possible dyes which can be incorporated as photochromic systems are described by way of example in Kirk-Othmer Encyclopedia of Chemical Technology vol. 6, "Chromogenic Materials, Photochromie", pages 587-605, John Wiley and Sons, Inc., or else in: Heins Durr, Henri Bouas-Laurent (eds.), Photochromism: Molecules and Systems, Elsevier 2003. These dyes are expressly incorporated into the present disclosure content for incorporating into the inventive blends, preference being given to the spirooxazines described in these publications. Other possible systems are particularly those described in DE-A-36 22 871, or described in WO 2005/030856, or described in EP-A-0 313 341. These dyes, too, are expressly incorporated herein by way of reference. The abovementioned additives optionally present can be inter alia stabilizers, such as UV stabilizers, heat- stabilizers, and free-radical scavengers, and/or can be processing aids, plasticizers, further polymers, or a combination or mixture thereof. The molding compositions can moreover include nano-scale fillers and/or nano-scale functional substances, examples being laminar minerals or metal oxides which increase the refractive index of ophthalmic lenses. The invention moreover provides an article free from haze with at least one region or layer composed of the polyamide molding composition stated above. It is preferable that this is a foil, an insert, a profile, a tube, a hollow body, or an optically variable filter or particularly preferably an optical lens, with particular preference an ophthalmic lens. The article, i.e. particularly the ophthalmic lens, preferably has a color gradient and/or has a photochromic coating, an antireflection coating, a scratch-resistant coating, an optical filter coating, a polarizing coating, an oxygen-barrier coating, or a combination of such coatings. In particular for high-specification optical applications, e.g. in the form of ophthalmic lenses, it has . proven advantageous for the glass transition temperature of an article composed of the polyamide molding composition to be above 90°C or 100°C, preferably above 130°C, particularly preferably above 150°C. The present invention moreover provides a process for production of an article as stated above, particularly preferably of an ophthalmic lens, which comprises molding a polyamide molding composition as stated above in an extrusion process, in an injection-molding process, or in an in-mold-coating process, to give the article, where the photochromic dye can be introduced in an advance and/or, if appropriate, in a downstream dip-bath-coating process and/or thermal transfer process (or in any other doping process) into the mixture composed of transparent polyamide and of further polymer. The photochromic article can also be a photochromic foil which can be applied to a substrate, preferably a conventional lens not photochromically modified, via lamination or adhesive bonding. Such a process for production of a bulk-colored article can by way of example comprise compounding the photochromic dye together with the transparent homopolyamide and/or copolyamide and with the further polymer, where the dye can, by way of example, be added in the form of a liquid concentrate to the polymer melt composed of transparent homopolyamide and/or copolyamide and further polymer with the aid of a metering pump and/or the dye in the form of a solid is applied to the other components in a mixing drum, and where, if appropriate, application aids can also be used. In another possible method, the dya and the further polymer are processed to give a masterbatch with high color concentration which is preferably up to 3 0%, and the reguired amount of this masterbatch is processed with the transparent polyamide and/or copolyamide in an extruder to give pellets or is converted directly into the finished molding in the injection-molding machine. The proposed polyamide molding composition can be used by way of example as constituent or coating of elements with spectral filter effect, e.g. in the form of spectacle lens, sun lens, corrective lens, or optical filter, or in the form of a switching assembly or optical signal processing, ski goggles, visor, safety spectacles, photorecording, display, optical data storage, or windows of buildings and of vehicles, etc. Secondly, it can also be used in connection with decorative elements or with structural elements, for example in the form of a spectacle frame, toy, or cover, particularly in the form of a mobile-telephone case, a part of electronic devices, a coating, particularly of packaging, of decorative items, of sports equipment, or of cladding, preferably in the automobile sector. In the case of the last applications it is sometimes sufficient to have photochromicity not in transmission but in reflection. Further embodiments are described in the dependent claims and are included in the description; METHODS. OF CARRYING OUT THE INVENTION Examples will be used below to illustrate the invention. The examples are intended to indicate how a polyamide molding composition can be prepared and, for example, processed to give a molding, but are not intended to be interpreted as restricting the protected subject matter defined in the annexed patent claims. Examples 1 to 13 and comparative examples (CE) 1 to 5: First, the polymer, mixtures, composed of transparent polyamide and of a block copolymer as further polymer, were prepared on a Collin Teach-Line ZK25T L/D - 18 twin-screw extruder. The barrel temperatures were from 200 to 280°C except in the feed zone, and the screw rotation rate was 120 to 250 rpm. The spirooxazine dyes (OP 14 BLUE, OP 19 RED) were applied with the aid of Tween. 20 (0.05% by weight) to the pellets of the transparent polyamides or to the polymer mixtures based on the transparent polyamides, in a mixing drum. These mixtures were then processed in an Arburg Allrounder 350-90-220D injection-molding machine to give plaques of dimensions 30x30xlmm, the cylinder temperatures being from 200 to 260°C and the mold temperature being from 2 0 to 60°C. The screw rotation rate was from 150 to 400 rpm. The constitutions of the photochromic polyamide molding compositions used in each of the inventive examples are collated in tables 1 and 2, and those of the comparative examples are collated in table 3. ) Irradiation time: 3 0 seconds The evaluation used- in the .tables .. for photochromic behavior, using the symbols --, -, o, +, and ++ is based on qualitative visual assessment, and this is based on the rapidity of coloring and of fading (kinetics) , and also on the depth of color achievable after irradiation. Optical filtering in spectacle lenses has two functions. Firstly, the intensity of light reaching the eye is reduced, and secondly dangerous UV radiation is kept away from the eye. since most photochromic dyes have intense absorption bands in the UV-A and UV-B region, even low concentrations of further UV absorbers (UV blockers), e.g. Tinuvin 326, are sufficient to achieve (inventive example 12) adequate UV-region absorption for spectacle lenses. In inventive example 12, therefore, even 0.05% by weight of Tinuvin 32S is sufficient to achieve a pronounced UV cutoff at 3 90 nm. ) Irradiation time: 30 seconds n.d.: not determined From table 3 it can be concluded that comparative examples CE3, CE4, and also CE5 show positive results with respect to photochromic properties, but the mechanical properties of the materials are unsuitable for the inventive applications. Articles or layers produced from molding compositions corresponding to CE3-CE5 are too soft, or have too little heat resistance for such applications. The optical measurements were carried out on Datacolor SF 600Plus color measurement equipment. An LED panel (10 x 8 diodes) with an emission maximum at about 415 nm (half-value width about 50 nm) was used for excitation of the dyes, applying a voltage of 27 V with a current of 0.05 ampere. This method was selected since the effect achieved by this irradiation was the same, with respect to the photochromic effect, as that occurring in January at the Applicant's location using natural insolation when the sky is cloudless. The spectral studies were carried out at a temperature of 20°C, and it is known that the kinetics of darkening and of fading are temperature dependent. The plagues were then placed, unirradiated, in the beam path of the flash lamp (transmittance measurement mode), and the absorption spectrum was measured from 400 to 700 nm. The plaque was then irradiated for 3 0 sec by means of the LED panel and the absorption spectrum was recorded immediately after removal of the radiation source. The absorption spectrum thus measured provides the maximum achievable darkening (color saturation) for the purposes of present considerations. However, because the reverse reaction of the dye to give its colorless form is sometimes very rapid, with resultant fading of the plaque, a maximum darkening thus determined is markedly below the genuine saturation achieved under irradiation, since up to 2 seconds can pass before the actual spectral measurement takes place. It is clear that the reverse reaction takes place most rapidly specifically in the state of maximum darkening, at which the highest concentration of excited dye molecules is present. In order to measure the rate of fading, the absorption spectrum was recorded at various times after removal of the radiation source. The transrnittanca values determined at various junctures at wavelength 600 nm are collated in tables 4 and 5 for inventive examples 3 to 9. The Airwear® T5G lens from ESSILOR, France serves as comparison. This lens is a plastic lens (thickness 2 mm) composed of polycarbonate. The lens is either colored by dip-bath coating or coated with a photochromic lacquer. The transmittance of this lens was determined at 580 nm, because of the characteristic positioning of the absorption bands. Markedly longer irradiation with the LED panel gave more marked darkening (saturation) than shown in the values of tables 1-3. By way of example, transmittance in inventive example 3 is reduced from 60% to 55% if the irradiation time is extended from 3 0 to 12 0 seconds. Table 4: Transmittance (%) at 600 nm measured on 30x30x1 mm plagues as a function of time (fading) ; plaques were previously irradiated for 3 0 seconds with the LED panel; "0 seconds" therefore represents the first measurement after the end of irradiation. An impression of the speed of return of the various test specimens to the colorless state Is given by the interval stated in tables 4 and 5 during which the darkening (transmittance in unexcited . state minus transmittance at color saturation) shows 80% reversion. It is interesting that this interval for the decrease in depth of color of the photochromic polyamide compositions can be controlled within a wide range via selection of the added polymer. Values of from 20 to 65 0 seconds are realized in the present inventive examples. Haze was determined at 23°C using a Haze-Gard Plus from Byk-Gardener to ASTM D1003 (illuminant C). The production process for the plaques of thickness 1 mm as stated in the tables above is not representative of particularly high-specification optical applications, since the molds used do not meet the requirements for such high-level applications. For comparison. taking the abovementioned inventive example 3 as a basis, i.e. the molding composition of inventive example 3, processing was again carried out to give a flat 2 mm plaque using a mold with better suitability for high-specification optical purposes (polished and under ideal injection-molding conditions). The following values were obtained here in the unirradiated state: transmittance = 89%, haze = 1.1. In other words, ideal manufacture of the moldings gives even higher transmittance and an even smaller haze value (in the unirradiated state). The glass transition temperature of the transparent polyamide used inter alia in inventive example 3 is 155°C. The glass transition temperature of the blend with 10% of PE 73 34 is 151°C. The marked improvement in the photochromic effect cannot therefore be explained here in the potentially obvious way solely via the macroscopic magnitude of the glass transition temperature, since this has been reduced by no more than 4°C by virtue of the mixture. Instead, the local segment freedom of movement at the location of the dye molecules must be significantly increased, in order to achieve the desired effect. The higher local freedom of movement or the reduced local viscosity is brought about via flexible main chain sections or flexible side chains of the further polymer. FE7334 is a polyesteramide based on polyamide-12 and dimer diol, described in EP 0955326 B1 (glass transition temperature Ts = -30°C) . FE7334 contains polyester segments based on dimer acid and dimer diol. GRILAMID TR 90: is a transparent, thermoplastically processable polyamide based on aliphatic and cycloaliphatic units. It corresponds to the systems proposed in EP 0 837 087, and is specifically in essence a homopolyamide of MA.CM12 type (where the numeral 12 represents dodecanedioic acid). GRILAMID ELY 60 is a polyetheramide, GRILAMID ELY 24 75 and 2694 are polyetheresteramides from EMS-CHEMIE AG, Switzerland (Tg = from -3 0 to -50°C). Tween 2 0 is a polyoxyethylene derivative of a fatty acid ester of sorbitan and is also termed Polysorbat 20, and is an application aid often used for various dyes. PEBAX 5533 and 7033 are polyamide-12 block copolymers having ether segments from ARKEMA, France (Tg - about -40°C). NCC® dyes OP 14 BLUE and OP 19 RED from New Prismatic Enterprise Co. , Ltd., Taiwan were used as photochromic dyes. Polyshine Blue I was also used as photochromic dye and is obtainable from Polychrom Co., Ltd. (Korea). Tinuvin 326, obtainable from CIBA SC AG, Switzerland, was also used as UV absorber: The relative viscosity (ηrel) was measured according to DIN EN ISO 307 in a 0.5 weight% solution in m-cresol at a temperature of 20°C. The glass transition temperature (Tg.) was determined according to ISO 11357-1/2; The differential scanning calorimetry (DSC) was carried out with a heating rate of 2 0K/min. The values are given for the onset. Further inventive examples: Further examples 14-21 are stated together with the properties determined in them in additional table 7: Key: PE7313, FE7314: polyesteramide based on polyamide-12 and dimer diol; FE7314 also contains polyester segments based on dimer acid and dimer diol. XE3680 is a heat/ov masterbatch based on polyamide-12. XE2828 is a polyamide-12 oligomer whose number average molar mass is about 2000 g/mol, having mainly non- condensable alkyl end groups. GRILAMID L16 is a low-viscosity polyamide-12. Results: Haze and photochromic effect are improved via addition of low-viscosity polyamide-12 (cf. inventive example 14 and inventive example 15). Furthermore, addition of polyamide-12 and polyamide oligomer permits processing of the photochromic polyamide molding composition under gentler conditions or incorporation of the photochromic dye into the thermoplastic molding composition under gentler conditions, thus permitting substantial inhibition of degradation of the unstable photochromic dye during the extrusion and/or injection-molding process. The gate marks (round plaque, 70 x 2 mm) markedly visible in inventive example 17 can be avoided by various measures. Addition of 10% by weight or more of a low-viscosity polyamide-12 is effective in inhibiting formation of gate marks. Gate marks can likewise be avoided if the ratio of solution viscosities of the transparent polyamide/copolyamide and of the polymer component whose glass transition temperature is below 80°C is smaller than 1.2, particularly smaller than 1.1 (see inventive example 20 compared with inventive example 19 and inventive example 18 compared with inventive example 17, and also inventive example 21). Haze, too, decreases for identical chemical constitution of the polymer components as the ratio of the solution viscosities of the two polymer components -falls. In inventive- example 19,with a ratio of 1.22 for the solution viscosities, the observed haze is 3,9, whereas in IE20 with a lower ratio of solution viscosities of 1.04, the result is markedly lower haze of 1.8. Although addition of polyamide-12 oligomer does not necessarily always inhibit formation of gate marks, it makes processing easier overall, by virtue of lower melt viscosity and longer flow path. We claim: 1. A polyamide molding composition comprising a proportion by weight of from 50 to 99% by weight of one or several transparent homopolyamides, one or several copolyamides, or a combination of one or several transparent homopolyamides and one or several copolyamides, selected from the group consisting of: MACM12, MACM14, MACM18, MACM12/PACM12, MACM14/PACM14, MACM18/PACM18, 12/MACMI; a proportion by weight of from 1 to 50% by weight of one or several further polymers whose glass transition temperature is below 0°C, selected from the group consisting of: MACM36, PACM36, polyamide-12. block copolymer with polyether soft segments, polyamide-12 block copolymer with polyester soft segments or a combination thereof; a proportion by weight of from 0.001 to 2.0% by weight of at least one photochromic dye such as herein described; and also, optionally, further additives selected from the group consisting of: further dyes, stabilizers, processing aids, plasticizers, further polymers, functional additives, or a combination or mixture thereof, wherein the photochromic polyamide molding composition has a transmittance in the unexcited state of more than 80% in the wavelength range from 500 to 700 nm if measured in the form of a thin plaque of a thickness of 2 mm, and with a haze of less than 5 if measured in the form of a thin plaque of a thickness of 2 mm. 2. The polyamide molding composition as claimed in claim 1, wherein the glass transition temperature of the further polymer is in the range from (-60) - (-20)°C. 3. The polyamide molding composition as claimed in any of the preceding claims, wherein the proportion by weight present of the transparent homopolyamide or copolyamide is from 70 to 99% by weight. 4. The polyamide molding composition as claimed in any of the preceding claims, wherein the proportion by weight present of the further polymer is from 1 to 30% by weight. 5. The polyamide molding composition as claimed in any of the preceding claims, wherein the solution viscosity (ηrel) of the transparent homopolyamide or copolyamide is from 1.3 to 2.0. 6. The polyamide molding composition as claimed in any of the preceding claims, wherein the photochromic dye is a dye which is reversibly excitable with UV or short-wave VIS. 7. The polyamide molding composition as claimed in any of the preceding claims, wherein within the additives the stabilizers are selected to be UV stabilizers, heat stabilizers, or free-radical scavengersor are a combination or mixture thereof. 8. The polyamide molding composition as claimed in any of the preceding claims, which comprises polyamide-12. 9. The polyamide molding composition as claimed in claim 8, wherein the solution viscosity (ηrel) of the low- viscosity polyamide-12 is from 1.5 to 2. 10. The polyamide molding composition as claimed in any of the preceding claims, which comprises a polyamide oligomer. 11. The polyamide molding composition as claimed in claim 10, wherein the polyamide oligomer is a polyamide-12 2. The polyamide molding composition as claimed in claim 1, wherein the glass transition temperature of the further polymer is in the range from (-60) - (-20)°C. 3. The polyamide molding composition as claimed in any of the preceding claims, wherein the proportion by weight present of the transparent homopolyamide or copolyamide is from 70 to 99% by weight. 4. The polyamide molding composition as claimed in any of the preceding claims, wherein the proportion by weight present of the further polymer is from 1 to 30% by weight. 5. The polyamide molding composition as claimed in any of the preceding claims, wherein the solution viscosity (ηrel) of the transparent homopolyamide or copolyamide is from 1.3 to 2.0. 6. The polyamide molding composition as claimed in any of the preceding claims, wherein the photochromic dye is a dye which is reversibly excitable with UV or short-wave VIS. 7. The polyamide molding composition as claimed in any of the preceding claims, wherein within the additives the stabilizers are selected to be UV stabilizers, heat stabilizers, or free-radical scavengersor are a combination or mixture thereof. 8. The polyamide molding composition as claimed in any of the preceding claims, which comprises polyamide-12. 9. The polyamide molding composition as claimed in claim 8, wherein the solution viscosity (ηrel) of the low- viscosity polyamide-12 is from 1.5 to 2. 10. The polyamide molding composition as claimed in any of the preceding claims, which comprises a polyamide oligomer. 11. The polyamide molding composition as claimed in claim 10, wherein the polyamide oligomer is a polyamide-12 oligomer whose average molar mass is from 1500 to 2500 g/mol. 12. The polyamide molding composition as claimed in any of the preceding claims, wherein the ratio of the solution viscosities (ηrel) of the transparent homopolyamide or copolyamide and of the further polymer whose glass transition temperature is below 0°C is smaller than 1.2. 13. A transparent article having at least one region or one layer composed of a polyamide molding composition as claimed in any of the preceding claims. 14. An article as claimed in the preceding claim for high- specification optical applications, whose haze is less than 3, for a thickness of the layer composed of the polyamide molding composition of 2 mm. 15. The article as claimed in claim 13 or 14, which is a foil, a profile, a tube, a hollow body, or an optically variable filter or an optical lens, ski goggles, visor, safety spectacles, photorecording, display, optical data storage, or windows of buildings and of vehicles, or is a decorative element or a structural element, a spectacle frame, toy, or cover, , , a part of electronic devices, a coating,. 16. The article as claimed in any of claims 13 to 15, which has a color gradient or has a photochromic coating, an antireflective coating, a scratch-resistant coating, an optical filter coating, a polarizing coating, an oxygen- barrier coating, or a combination of such coatings. 17. The article as claimed in any of claims 13 to 16, wherein the glass transition temperature of the region or the layer composed of the polyamide molding composition is above 90°C. 1.8. The process for production of an article as claimed in any of claims 13 to 17, which comprises molding a polyamide molding composition as claimed in any of claims 1 to 23 in an extrusion process, in an injection-molding process, or in an in-mold-coating process, to give the article, where the photochromic dye can, if appropriate, be introduced in a downstream immersion-bath process or thermal transfer process into the mixture composed of transparent polyamide and of further polymer, and where the photochromic article can also be a foil which can be applied to a substrate via lamination or adhesive bonding. 19. The process for production of a bulk-colored molding as claimed in claim 17, which comprises compounding the photochromic dye such as herein described in a proportion by weight of from 0.001 to 2.0% by weight such as herein described together with the transparent homopolyamide or copolyamide and with the further polymer, where the dye can be added in the form of a liquid concentrate to the polymer melt composed of transparent homopolyamide or copolyamide and further polymer with the aid of a metering pump, or the dye is applied in the form of solid to the other components in a drum mixer, and where use may also be made, if appropriate, of application aids. 20. The process for production of a bulk-colored molding, as claimed in claim 18, wherein the dye and the further polymer are processed to give a masterbatch with high color concentration which is up to 30%, and the required amount of this masterbatch is processed with the transparent polyamide or copolyamide in an extruder to give pellets or is converted directly into the finished molding in the injection-molding machine. 21. The polyamide molding composition as claimed in claim 1, wherein the proportion by weight present of the transparent homopolyamide or copolyamide is from 80 to 98% by weight. 22. The polyamide molding composition as claimed in claim 1, wherein the proportion by weight present of the further polymer is from 2 to 20% by weight. 23. The polyamide molding composition as claimed in any of the preceding claims, wherein the solution viscosity (ηrel) of the transparent homopolyamide or copolyamide is from-1.40 to 1.85, or its glass transition temperature Tg is above 90°C, or above 110°C, or above 130°C. 24. The polyamide molding composition as claimed in claim 1, wherein the photochromic dye is a dye which is reversibly excitable with UV or short-wave VIS, being a dye based on spirooxazines. 25. The polyamide molding composition as claimed in any of the preceding claims, wherein the functional additives are functional additives for influencing optical properties such as refractive index. 26. The polyamide molding composition as claimed in any of the preceding claims, which comprises low-viscosity polyamide-12. 27. The polyamide molding composition as claimed in claim 26, wherein the solution viscosity (ηrel) of the low- viscosity polyamide-12 is from 1.6 to 1.9. 28. The polyamide molding composition as claimed in claim 1, which comprises a polyamide-12 oligomer. 29. The polyamide molding composition as claimed in claim 28, wherein the polyamide oligomer is a polyamide-12 oligomer whose average molar mass is from 1500 to 2500 g/mol, having mainly non-condensable alkyl end groups. 30. The polyamide molding composition as claimed in claim 1, wherein the ratio of the solution viscosities (ηrel) of the transparent homopolyamide or copolyamide and of the further polymer whose glass transition temperature is below 0°C is smaller than 1.1. 31. A transparent, haze-free article having at least one region or one layer composed of a polyamide molding composition as claimed in any of the preceding claims. 32 The article as claimed in claim 13 or 14, which is an optical lens, an ophthalmic lens, an element with spectral filter action, a spectacle lens, sun lens, corrective lens optical filter in the form of a switching assembly or optical signal processing or is a decorative element or a structural element, in the form of a spectacle frame, toy, or cover in the form of a mobile-telephone case, a part of electronic devices, a coating of packaging, of decorative items, of sports equipment, or of cladding, in the automobile sector. 33.The article as claimed in any of claims 13 to 16 wherein the glass transition temperature of the region or the layer composed of the polyamide molding composition is above 130°C. ABSTRACT PHOTOCHROMIC MOLDING COMPOSITIONS AND ARTICLES PRODUCED THEREFROM The invention discloses a polyamide molding composition comprising from 50 to 99% by weight of one or several transparent homopolyamides, one or several copolyamides, or a combination of one or several transparent homopolyamides and one or several copolyamides, selected from the group consisting of: MACM12, MACM14, MACM18, MACM12/PACM12, MACM14/PACM14, MACM18/PACM18, 12/MACMI; from 1 to 50% by weight of one or several further polymers whose glass transition temperature is below 0°C, selected from the group consisting of: MACM36, PACM36, polyamide-12 block copolymer with polyether soft segments, polyamide-12 block copolymer with polyester soft segments or a combination thereof from 0.001 to 2.0% by weight of at least one photochromic dye such as herein described; and also, optionally, further additives selected from the group consisting of: further dyes, stabilizers, processing aids, plasticizers, further polymers, functional additives, or a combination or mixture thereof, wherein the photochromic polyamide molding composition has a transmittance in the unexcited state of more than 80% in the wavelength range from 500 to 700 am if measured in the form of a thin plaque of a thickness of 2 mm, and with a haze of less than 5 if measured in the form of a thin plaque of a thickness of 2 mm. The invention is also for molded articles made with said composition.

Full Text

TECHNICAL FIELD
The present invention relates to photochromic molding
compositions and to articles produced therefrom, e.g.
ophthalmic lenses, and also to processes for production
of such articles. These are preferably bulk-colored
molding compositions, but coloring in a dip-coating
bath or by way of another method of introducing/doping
the photochromic dye is likewise possible.
PRIOR ART
Photochromic molding compositions are starting.
materials used for production of photochromic articles,
e.g. sunglass lenses which undergo reversible tinting
on exposure to light, or similar articles.
Photochromic means that the dye is converted to an
excited state via exposure to light (UV or short-wave
VIS) , the unexcited, thermodynamically state and the
excited state here having different absorption spectra
(cf. definition of Photochromie [Photochromicity] in:
R6mpp Lexikon Chemie [Rompp's Chemical Encyclopedia],
10th edition, page 3303, Georg Thieme Verlag,
Stuttgart) . The excited state generally has an intense
color, whereas the initial form is colorless. The
excited dye molecule returns to the unexcited state via.
a thermal or radiation-induced reverse reaction.
These dyes can be used to produce optical filters whose
variability is light-induced, for example by
introducing the dye into a plastics matrix (bulk

coloring), or by applying a coating with dye onto glass
or plastic, (cf., for example, J,F. Rabek in Mechanisms
of Photophysical Processes and Photochemical Reactions
in Polymers, chapter 10, pages 3 77 - 3 91, for incorporation of such dyes into polymeric matrices).
An important application is provided by ophthalmic
lenses, e.g. sunglass; lenses, which spontaneously
darken when subject to insolation. A plurality of
photochromic dyes and/or one or more inert dyes
together with the photochromic dye are used in order to
give these lenses the desired shade of color. If an.
inert dye is used, the lens, even in the non-irradiated
state, has an underlying tint or a color, and this
reduces transmittance.
A significant aspect of such applications is that the
number of possible repeats of the reversible
photochromic process has been maximized, and that the
dye is not irreversibly removed from this cycle by
environmental effects (e.g. oxygen) or side reactions
(e.g. with the polymer matrix or with additives). A
further precondition is that the "switching process"
(excitation) and/or the thermal reverse reaction
proceed(s) to practical completion within an acceptable
period, rf this is not the case, tinting of the lens
does not occur on exposure to light (no reduction in
transmittance) , and/or the lens retains its tint for a
long time after exposure to light. Both are undesired.

Marketing of the first photpchromic plastic lenses
began as early as 1980. However, numerous improvements
in the dyes and in the polymeric matrices had to be
achieved before the photochromic system achieved
adequate lifetime and satisfactory spectral
performance. Initially, 'such plastics lenses were
practically entirely based on cast systems, e.g. allyl
diglycol carbonate CR39, which is obtainable via

polymerization of bisallyl carbonates. Later, lenses
based on (meth) acrylates and on polycarbonates also
became available, and recently an increasing number of
lenses is produced thermoplastically, the materials
often used here being thermoplastic polyurethanes
(TPU).
Some disclosures from the patent literature in the
general context of photochromically doped plastics will
be described below. There are intentionally no details
given of the wide variety of descriptions of systems
such as CR39 which are processed in a casting process
with crosslinking to give lenses, since the present
invention does not encompass such systems.
JP-A-63 02783 7 describes a photochromic system in which
a PET (polyethylene terephthalate) plastics matrix with
which a plasticizer has been admixed (from 2 to 15% by
weight) is doped with a photochromic dye. The intention
of this selection of the matrix is that the long-term
stability of such a layer be improved, under constant
exposure to light and heat, and this layer can, for
example, be applied to a nylon film.
JP-A-01180536 likewise describes a photochromic
material intended to be heat-resistant and weather-
resistant. It is composed of a plastics matrix composed
of a transparent plastic and of an additive which is a
polymer having a defined proportion of monomers having hydroxyl groups, e.g. PVB (polyvinyl butyral) or
polyvinyl acetate. A wide variety of possible systems
is stated as transparent plastic, examples being PMMA,
PC, transparent nylon, etc.
JP-A-01024740 is like the two abovementioned
specifications from the tinted vehicle windshields
sector in describing a multilayer structure composed of
two glass layers with an intermediate layer which

comprises a photochromic material. A plurality of
possibilities is stated as transparent material of this
intermediate layer, inter alia vinyl resin, acrylic
resin, polyester resin, and polyamide resin,
Spirooxazines inter alia are mentioned as dyes, and a
specific distribution of the dye is emphasized as
advantageous.
WO 01/49478 describes a photochromic lens which is
composed of a PC substrate and of a photochromically
doped coating composed of thermoplastic polyurethane
(TPU) . This coating is applied to a PC preform in an.
in-mold-coating process.
BRIEF DESCRIPTION OF THE INVENTION
The invention is therefore based inter alia on the
object of providing a photochromic material improved in
comparison with the materials of the prior art. A
particular object is improvement of such materials
based on polyamides.
This object is achieved in particular by providing a
photochromic polyamide molding composition which
comprises a proportion by weight of from 50 to 99% by
weight of at least one transparent homopolyamide and/or
copolyamide, a proportion by weight of from 1 to 50% by
weight of at least one further polymer whose glass
transition temperature is below 80°C, and also a
proportion by weight of from 0.001 to 2.0% by weight of
at least one photochromic . dye. This material can.
optionally comprise, inter alia, further dyes and/or
additives. It is not necessary that photochromic dye
has been previously admixed with this material, and it
is also possible to use the mixture composed of
polyamide and of other polymer with the properties,
mentioned in relation to glass transition temperature
as initial charge and to introduce the dye into the

article, e.g. in a dip-coating bath, after or during
production of an article (e.g. production of a lens in
an injection-molding process).
The further polymer preferably has at least one
amorphous phase whose glass transition temperature is
at most 80°C. If the further polymer is a block polymer
having a soft segment, the glass transition temperature
of the soft segment should be below 4 0°C, preferably
below 25°C.
The term used in this specification "transparent
polyamides" is intended to mean polyamides or
copolyamides or molding compositions formed therefrom,
their light transmittance being at least 70% when the
(co)polyamide (in pure form, i.e. without the further
constituents stated above of the inventive molding
composition) takes the form of a thin plaque (plate),
thickness 2 mm. Light transmittance is measured here on
a Perkin Elmer uv/vIs spectrometer in the range from
200 to 80 0 run, using round plaques measuring 70 x 2 mm.
The transmittance value is stated for the wavelength
range from 500 to 700 nm. The round plagues measuring
70 x 2 mm are produced for this purpose by way of
example on an Arburg injection-molding machine in a
polished mold, the cylinder temperature here being from.
200 to 340°C and mold temperature from 20 to 140°C.
Examples of transparent polyamides that can be used for
these purposes are polyamides and/or copolyamides as
described in DE-A-102 24 947, or DE-A-101. 22. 188,
CH-A-688 624 or EP=A-0 725 TOO", or a "mixture" thereof.
In relation to transparent polyamides, the disclosure
of these documents and the polyamide systems and
copolyamide systems mentioned therein are expressly
incorporated into this description.

One of the advantages of the use of polyamides as main
material is that, unlike materials such as CR39 or
acrylate which have been used hitherto for production
of ophthalmic lenses, these being materials which
required traditional casting processes involving
polymerization (crosslinking), transparent polyamides
(amorphous or microcrystalline) can be processed in
simple injection-molding processes with low cycle
times, i.e. using low-cost mass production. The
inventive polyamide molding composition is therefore
also preferably not crosslinkable.
It is preferable that the mixture is composed of a
proportion by weight of from 70 to 99% by weight,
particularly from 80 to 93% by weight, of the
transparent homopolyamide and/or copolyamide and of a
proportion by weight of from l to 3 0% by weight,
particularly from 2 to 20% by weight, of at least one
further polymer whose glass transition temperature is
below SO or 40°C (i.e. without dye), and the mixture is
at the same time likewise preferably in essence
transparent in the above sense or no more than 10%, or
preferably 5%, less transparent than in the above
sense. For components whose optical specification is
less demanding, or for components in which the
photochromic processes are relevant only in reflection
(for example decorative items), lower transparency and
even slight haze are also possible. For components with
a demanding optical specification, transmittance above
70%, preferably above 80%., in the wavelength range from
500 to 700 run (measured at a layer thickness of 2 mm) -is- preferred and/or haze less than 5 or even 3, and
preferably less than 2 (ASTM 1003, layer thickness-
2 mm) .
Addition of polyamide-12 (also called polyamide-12), in
particular of low-viscosity PA12 (solution viscosity or
relative viscosity ηrel - according to DIN EN ISO 307 in

a 0.5 weight% solution in m-cresol at 20°C - from 1.5
to 2, preferably from 1.6 to 1.9} can improve haze and
photochromic effect.
Addition of polyamide-12 and/or polyamide oligomer
moreover makes it possible to process the photochromic
polyamide molding composition under milder conditions
and to incorporate the photochromic dye into the
thermoplastic molding composition under milder
conditions, and it is therefore possible to inhibit
substantially any degradation of the unstable
photochromic dye during the extrusion and/or injection-
molding process. An example of a suitable polyamide
oligomer is a polyamide-12 oligomer, preferably with
average molar mass of from 1500 to 25 0 0 g/mol,,
particularly preferably having mainly non-condensable
alkyl end groups.
Various measures can be used to avoid gate marks.
Addition of 10% by weight or more of a low-viscosity
polyamide-12 can be effective in inhibiting formation
of gate marks. Gate marks can likewise be avoided if
the ratio of the solution viscosities of the
transparent polyamide and of the polymer component
whose glass transition temperature is below 80°C is
smaller than 1.2, in particular smaller than 1.1. Haze,
too, is reduced as the ratio of the solution
viscosities of the two polymer components falls, for
identical chemical constitution. Addition of polyamide-
12 oligomer makes processing easier overall, by virtue
of lower melt viscosity and longer flow path.
Although it has been possible for some years to prepare
amorphous polyamides, too, in the purity required for
optical applications, examples being polyamides of type
MACM12 as described in DE-A-196 42 885, these being
available from EMS CHEMIE, Switzerland, with trade name
Grilamid TR 90, simple addition of a photochromic dye

cannot give satisfactory photochromic results in the
lenses produced from these pure systems.
MACM here represents the compound whose ISO name is
bis(4-amino-3-methylcyclohexyl)methane, which is
commercially available as the C260 grade of Laromin
(CAS No.. 6864-37-5) with trade name 3,3'-dimethyl-4,4'-
diaminodicyclohexylmethane. The numeral 12 represents
an aliphatic linear C12 dicarboxylic acid (DDA,
dodecanedioc acid) , with which the diamine MACM has
been polymerized.
Surprisingly, it has been found that, contrary to
previous experience to the effect that addition of
photochromic dyes to transparent polyamides does not
give satisfactory photochromic behavior, the inventive
material gives, when processed to give photochromic
articles, unexpectedly long-lived, i.e. frequently
repeatable, reversible photochromic behavior.
Furthermore, the preferred dyes are among the most
stable photochromic systems. The switching process
(excitation) moreover proceeds rapidly and the thermal
reverse reaction likewise proceeds almost to completion
within a reasonable period from seconds to at most a
few minutes.
Normally, only pure polyamide materials whose glass
transition temperature is below. 100°C, i.e. not those
present in the form of a mixture,, exhibit pronounced
photochromic behavior, an example being MACM3 6 or
PACM3 6, where PACM represents the compound whose ISO
name is_his(4-aminGcyclGhexyl)methane, available as
Dicykan grade (CAS Mo. 1761-71-3) with tradename
4,4'-diaminodicyclohexylmethane.. However, the defective
mechanical or thermal properties of these materials
generally make them unsuitable by way of example for
ophthalmic lens applications. Addition of a further
polymer to a transparent (co)polyamide alongside the

dye is possible. However, these polymers and the
resultant mixture (blend) are subject to stringent
requirements, particularly for ophthalmic lens
applications, and admixture normally results in haze in
the blend. However, optical properties (transmittance,
haze, Abbe number) of the mixtures (blends) should not
be substantially below the level of the pure
polyamides. The photochroraic process should have good
kinetics (darkening and fading within period from
seconds to a few minutes, preferably within from 20 to
60 seconds) and continue over a long lifetime. This is
the case with the proposed materials and with the
articles produced therefrom. As previously mentioned,
these good properties of the bulk-colored articles also
occur when the article is manufactured from the blend
without dye and the dye is introduced after the initial
molding of the article, e.g. in a dip-coating bath. The
presence of the other polymer with low glass transition
temperature alongside the transparent polyamide
provides an environment for the photochromic dyes
permitting the reversible changes of configuration
and/or of conformation which mostly occur during
excitation of the dyes and which are generally required
for the color change.
In one first preferred embodiment, the polyamide
molding composition is one where the glass transition
temperature of the further polymer is below 3 0°C,
preferably below 25°C. This can give ideal
photochromicity kinetics. Good values are obtained
particularly when the glass transition temperature of
the further polymer is below 0°C, preferably in the
range from (-60) - (-20)°C.
Another preferred embodiment with excellent kinetics is
one wherein the further polymer is a polyamide based on
cycloaliphatic diamines and aliphatic dicarboxylic
acids having from 6 to 40 carbon atoms., particularly

preferably having from 20 to 3 6 carbon atoms, the
cycloaliphatic diamine preferably being MACM and/or
PACM, and the entire polyamide particularly preferably
being MACM3 6 and/or PACM3 6, and/or wherein the further
polymer is a block copolymer having soft segments,
where the glass transition temperature of the soft
segments is preferably below 25°C. The further polymer
can, for example, be a polyamide block copolymer having
soft segments, preferably a polyamide-12 block
copolymer, the soft segments here preferably being
polyether soft segments and/or polyester soft segments
and/or polysiloxane soft segments and/or polyolefin
soft segments and/or polyacryiate soft segments.
Preferred polyether segments are those based on the
monomers ethylene oxide and/or propylene oxide and/or
tetrahydrofuran.
Possible other further polymers are also polyester
elastomers having soft segments and TPU elastomers
having soft segments, both of these being as previously
described at an earlier stage above in connection with
polyamide block polymers. It is also possible to use
other further polymers, as long as they meet the glass-
transition temperature conditions stated above,
examples being acrylate polymers, methacrylate polymers
(particularly preferably having long pendent groups),
polycarbonate copolymers, styxene copolymers
(preferably based on acrylonitrile, butadiene,
acrylate, methacrylate), polyolefins, particularly
grafted, ethylene copolymers (based on propene, butene,
pentene, hexene, octene, decene, undecene, butadiene,
styrene, acrylonitrile-, -isop-rene-, isobutylene, or being
derivatives of (meth)acrylic acid, vinyl acetate,
tetrafluoroethylene, vinylidene fluoride, hexafluoro-
propene and 2-chlorobutadiene), polyisobueylene,
polybutyl acrylate, and others.
In one preferred embodiment, the transparent

horaopolyamide and/or copolyamide is a polyamide based
on cycloaliphatic diamines and on aliphatic
dicarboxylic acids having from 6 to 3 6 carbon atoms, or
is a mixture of such homopolyamides and/or
copolyamides. Excellent transparency values with good
photochromicity are obtained by way of example when the
cycloaliphatic diamines are MACM and/or PACM and/or
when the aliphatic dicarboxylic acid is an aliphatic
dicarboxylic acid having 10, 12, or 18 carbon atoms.
For example, the transparent polyamide can be a
homopolyamide selected from the group of MACM12 (e.g.
Grilamid TR 90, cf. text further below), MACM18, and/or
is a copolyamide selected from the group of
MACM12/PACM12, MACM18/PACM18. It is preferable that the
refractive index of such systems is greater than or
equal to 1.50, the Abbe number being greater than or
equal to 40 and the density being smaller than or equal
to 1.1 g/cm3.
Another advantageous possibility is that the
transparent homopolyamide and/or copolyamide is a
polyamide based on aromatic dicarboxyic acids having
from 8 to 13 carbon atoms or is a mixture of such
homopolyamides and/or copolyamides, preferably based on
lactams and/or aminocarboxylic acids, where the
aromatic dicarboxylic acids are by way of example TPA
(terephthalic acid) and/or IPA (iscphthalic acid) . The
transparent homopolyamide and/or copolyamide can
advantageously be a polyamide selected from the group
of: 6I6T, TMDT, 6I/MACMI/MACMT, 6I/6T/MACMI,
MACMI/MACM3 6, 61, lactam-containing polyamides, such as
12/PACMX, 12/MAGMI, 1-2-MACMT;6-/PACMT, 6/6I-6/IPDT, or a
mixture thereof. The polyamides are designated pursuant
to ISO 1874-1. Each I here represents isophthalic acid
and each T here represents terephthalic acid, TMD
represents trimethylhexamethylenediamine, IPD
represents isophoronediamine.

It is advantageous and possible that the transparent
homopolyamide and/or copolyamide is a polyamide based
on at least one dicarboxylic acid and on at least one
diamine having an aromatic ring, preferably based on
MXD (meta-xylylenediamine), where the dicarboxylic acid
can be aromatic and/or aliphatic, the material
preferably being 6I/MXDI.
It is preferable that the refractive index of such
systems and generally of the transparent homopolyamide
and/or copolyamide is greater than or equal to 1.59,
the Abbe number being greater than or equal to 25 and
the density being smaller than or equal to 1.3 g/cm3.
It is preferable that the solution viscosity or
relative viscosity ηrel (according to DIN EN ISO 1528-1
or DIN EN ISO 307) is from 1.3 to 2.0, in particular
from 1.40 to 1.85. The glass transition temperature Tg
of the transparent homopolyamide and/or copolyamide is
moreover normally above 9 0°C, preferably above 1100C,
particularly preferably above 13 0°C.
Another preferred embodiment is one wherein the
photochromic dye is a dye which is reversibly excitable
with DV or short-wave VIS, preferably being a dye based
on spirooxazines. Excitable means that it can be
excited to a state in which its absorption spectrum
alters in such a way that absorption of visible light
takes place, when the dye has been embedded in the
matrix composed of polymer, i.e. in the inventive blend
composed of transparent polyamide and of other polymer
with the glass transition temperature stated above. The
achievable filter effect can be adjusted widely in the
visible region of the spectrum via the selection of the
photochromic dyes and adjustment of the concentration.
It is therefore possible to achieve a completely
reversible reduction to 40% or even 10% of the original
transmittance (generally from 80 to 92%) {in each case
measured on a plaque of thickness 1 or 2 mm with

parallel sides).
Other possible dyes which can be incorporated as
photochromic systems are described by way of example in
Kirk-Othmer Encyclopedia of Chemical Technology vol. 6,
"Chromogenic Materials, Photochromie", pages 587-605,
John Wiley and Sons, Inc., or else in: Heins Durr,
Henri Bouas-Laurent (eds.), Photochromism: Molecules
and Systems, Elsevier 2003. These dyes are expressly
incorporated into the present disclosure content for
incorporating into the inventive blends, preference
being given to the spirooxazines described in these
publications. Other possible systems are particularly
those described in DE-A-36 22 871, or described in
WO 2005/030856, or described in EP-A-0 313 341. These
dyes, too, are expressly incorporated herein by way of
reference.
The abovementioned additives optionally present can be
inter alia stabilizers, such as UV stabilizers, heat-
stabilizers, and free-radical scavengers, and/or can be processing aids, plasticizers, further polymers, or a
combination or mixture thereof. The molding
compositions can moreover include nano-scale fillers
and/or nano-scale functional substances, examples being
laminar minerals or metal oxides which increase the
refractive index of ophthalmic lenses.
The invention moreover provides an article free from
haze with at least one region or layer composed of the
polyamide molding composition stated above. It is
preferable that this is a foil, an insert, a profile, a
tube, a hollow body, or an optically variable filter or
particularly preferably an optical lens, with
particular preference an ophthalmic lens.
The article, i.e. particularly the ophthalmic lens,
preferably has a color gradient and/or has a

photochromic coating, an antireflection coating, a
scratch-resistant coating, an optical filter coating, a
polarizing coating, an oxygen-barrier coating, or a
combination of such coatings.
In particular for high-specification optical
applications, e.g. in the form of ophthalmic lenses, it
has . proven advantageous for the glass transition
temperature of an article composed of the polyamide
molding composition to be above 90°C or 100°C,
preferably above 130°C, particularly preferably above
150°C.
The present invention moreover provides a process for
production of an article as stated above, particularly
preferably of an ophthalmic lens, which comprises
molding a polyamide molding composition as stated above
in an extrusion process, in an injection-molding
process, or in an in-mold-coating process, to give the
article, where the photochromic dye can be introduced
in an advance and/or, if appropriate, in a downstream
dip-bath-coating process and/or thermal transfer
process (or in any other doping process) into the
mixture composed of transparent polyamide and of
further polymer. The photochromic article can also be a
photochromic foil which can be applied to a substrate,
preferably a conventional lens not photochromically
modified, via lamination or adhesive bonding.
Such a process for production of a bulk-colored article
can by way of example comprise compounding the
photochromic dye together with the transparent
homopolyamide and/or copolyamide and with the further
polymer, where the dye can, by way of example, be added
in the form of a liquid concentrate to the polymer melt
composed of transparent homopolyamide and/or
copolyamide and further polymer with the aid of a
metering pump and/or the dye in the form of a solid is

applied to the other components in a mixing drum, and
where, if appropriate, application aids can also be
used. In another possible method, the dya and the
further polymer are processed to give a masterbatch
with high color concentration which is preferably up to
3 0%, and the reguired amount of this masterbatch is
processed with the transparent polyamide and/or
copolyamide in an extruder to give pellets or is
converted directly into the finished molding in the
injection-molding machine.
The proposed polyamide molding composition can be used
by way of example as constituent or coating of elements
with spectral filter effect, e.g. in the form of
spectacle lens, sun lens, corrective lens, or optical
filter, or in the form of a switching assembly or
optical signal processing, ski goggles, visor, safety
spectacles, photorecording, display, optical data
storage, or windows of buildings and of vehicles, etc.
Secondly, it can also be used in connection with
decorative elements or with structural elements, for
example in the form of a spectacle frame, toy, or
cover, particularly in the form of a mobile-telephone
case, a part of electronic devices, a coating,
particularly of packaging, of decorative items, of
sports equipment, or of cladding, preferably in the
automobile sector. In the case of the last applications
it is sometimes sufficient to have photochromicity not
in transmission but in reflection.
Further embodiments are described in the dependent claims and are included in the description;
METHODS. OF CARRYING OUT THE INVENTION
Examples will be used below to illustrate the
invention. The examples are intended to indicate how a
polyamide molding composition can be prepared and, for

example, processed to give a molding, but are not
intended to be interpreted as restricting the protected
subject matter defined in the annexed patent claims.
Examples 1 to 13 and comparative examples (CE) 1 to 5:
First, the polymer, mixtures, composed of transparent
polyamide and of a block copolymer as further polymer,
were prepared on a Collin Teach-Line ZK25T L/D - 18
twin-screw extruder. The barrel temperatures were from
200 to 280°C except in the feed zone, and the screw
rotation rate was 120 to 250 rpm.
The spirooxazine dyes (OP 14 BLUE, OP 19 RED) were
applied with the aid of Tween. 20 (0.05% by weight) to
the pellets of the transparent polyamides or to the
polymer mixtures based on the transparent polyamides,
in a mixing drum. These mixtures were then processed in
an Arburg Allrounder 350-90-220D injection-molding
machine to give plaques of dimensions 30x30xlmm,
the cylinder temperatures being from 200 to 260°C and
the mold temperature being from 2 0 to 60°C. The screw
rotation rate was from 150 to 400 rpm.
The constitutions of the photochromic polyamide molding
compositions used in each of the inventive examples are
collated in tables 1 and 2, and those of the
comparative examples are collated in table 3.

*) Irradiation time: 3 0 seconds
The evaluation used- in the .tables .. for photochromic
behavior, using the symbols --, -, o, +, and ++ is
based on qualitative visual assessment, and this is
based on the rapidity of coloring and of fading
(kinetics) , and also on the depth of color achievable
after irradiation.
Optical filtering in spectacle lenses has two
functions. Firstly, the intensity of light reaching the
eye is reduced, and secondly dangerous UV radiation is
kept away from the eye. since most photochromic dyes
have intense absorption bands in the UV-A and UV-B
region, even low concentrations of further UV absorbers
(UV blockers), e.g. Tinuvin 326, are sufficient to
achieve (inventive example 12) adequate UV-region
absorption for spectacle lenses. In inventive
example 12, therefore, even 0.05% by weight of
Tinuvin 32S is sufficient to achieve a pronounced UV
cutoff at 3 90 nm.

*) Irradiation time: 30 seconds
n.d.: not determined
From table 3 it can be concluded that comparative
examples CE3, CE4, and also CE5 show positive results
with respect to photochromic properties, but the
mechanical properties of the materials are unsuitable
for the inventive applications. Articles or layers
produced from molding compositions corresponding to
CE3-CE5 are too soft, or have too little heat
resistance for such applications.
The optical measurements were carried out on
Datacolor SF 600Plus color measurement equipment. An
LED panel (10 x 8 diodes) with an emission maximum at
about 415 nm (half-value width about 50 nm) was used
for excitation of the dyes, applying a voltage of 27 V
with a current of 0.05 ampere. This method was selected
since the effect achieved by this irradiation was the
same, with respect to the photochromic effect, as that
occurring in January at the Applicant's location using
natural insolation when the sky is cloudless. The
spectral studies were carried out at a temperature of
20°C, and it is known that the kinetics of darkening
and of fading are temperature dependent.
The plagues were then placed, unirradiated, in the beam
path of the flash lamp (transmittance measurement
mode), and the absorption spectrum was measured from
400 to 700 nm. The plaque was then irradiated for
3 0 sec by means of the LED panel and the absorption
spectrum was recorded immediately after removal of the
radiation source. The absorption spectrum thus measured
provides the maximum achievable darkening (color

saturation) for the purposes of present considerations.
However, because the reverse reaction of the dye to
give its colorless form is sometimes very rapid, with
resultant fading of the plaque, a maximum darkening
thus determined is markedly below the genuine
saturation achieved under irradiation, since up to
2 seconds can pass before the actual spectral
measurement takes place. It is clear that the reverse
reaction takes place most rapidly specifically in the
state of maximum darkening, at which the highest
concentration of excited dye molecules is present.
In order to measure the rate of fading, the absorption
spectrum was recorded at various times after removal of
the radiation source. The transrnittanca values
determined at various junctures at wavelength 600 nm
are collated in tables 4 and 5 for inventive examples 3
to 9. The Airwear® T5G lens from ESSILOR, France serves
as comparison. This lens is a plastic lens (thickness
2 mm) composed of polycarbonate. The lens is either
colored by dip-bath coating or coated with a
photochromic lacquer. The transmittance of this lens
was determined at 580 nm, because of the characteristic
positioning of the absorption bands.
Markedly longer irradiation with the LED panel gave
more marked darkening (saturation) than shown in the
values of tables 1-3. By way of example, transmittance
in inventive example 3 is reduced from 60% to 55% if
the irradiation time is extended from 3 0 to
12 0 seconds.
Table 4: Transmittance (%) at 600 nm measured on
30x30x1 mm plagues as a function of time (fading) ;
plaques were previously irradiated for 3 0 seconds with
the LED panel; "0 seconds" therefore represents the
first measurement after the end of irradiation.

An impression of the speed of return of the various
test specimens to the colorless state Is given by the
interval stated in tables 4 and 5 during which the
darkening (transmittance in unexcited . state minus
transmittance at color saturation) shows 80% reversion.
It is interesting that this interval for the decrease
in depth of color of the photochromic polyamide
compositions can be controlled within a wide range via

selection of the added polymer. Values of from 20 to
65 0 seconds are realized in the present inventive
examples.
Haze was determined at 23°C using a Haze-Gard Plus from
Byk-Gardener to ASTM D1003 (illuminant C).
The production process for the plaques of thickness
1 mm as stated in the tables above is not
representative of particularly high-specification
optical applications, since the molds used do not meet
the requirements for such high-level applications. For
comparison. taking the abovementioned inventive
example 3 as a basis, i.e. the molding composition of
inventive example 3, processing was again carried out
to give a flat 2 mm plaque using a mold with better
suitability for high-specification optical purposes
(polished and under ideal injection-molding
conditions). The following values were obtained here in
the unirradiated state: transmittance = 89%,
haze = 1.1. In other words, ideal manufacture of the
moldings gives even higher transmittance and an even
smaller haze value (in the unirradiated state).
The glass transition temperature of the transparent
polyamide used inter alia in inventive example 3 is
155°C. The glass transition temperature of the blend
with 10% of PE 73 34 is 151°C. The marked improvement in
the photochromic effect cannot therefore be explained
here in the potentially obvious way solely via the
macroscopic magnitude of the glass transition
temperature, since this has been reduced by no more
than 4°C by virtue of the mixture. Instead, the local segment freedom of movement at the location of the dye
molecules must be significantly increased, in order to
achieve the desired effect. The higher local freedom of
movement or the reduced local viscosity is brought
about via flexible main chain sections or flexible side

chains of the further polymer.

FE7334 is a polyesteramide based on polyamide-12 and
dimer diol, described in EP 0955326 B1 (glass
transition temperature Ts = -30°C) . FE7334 contains

polyester segments based on dimer acid and dimer diol.
GRILAMID TR 90: is a transparent, thermoplastically
processable polyamide based on aliphatic and
cycloaliphatic units. It corresponds to the systems
proposed in EP 0 837 087, and is specifically in
essence a homopolyamide of MA.CM12 type (where the
numeral 12 represents dodecanedioic acid).
GRILAMID ELY 60 is a polyetheramide, GRILAMID ELY 24 75
and 2694 are polyetheresteramides from EMS-CHEMIE AG,
Switzerland (Tg = from -3 0 to -50°C).
Tween 2 0 is a polyoxyethylene derivative of a fatty
acid ester of sorbitan and is also termed
Polysorbat 20, and is an application aid often used for
various dyes.
PEBAX 5533 and 7033 are polyamide-12 block copolymers
having ether segments from ARKEMA, France (Tg - about
-40°C).
NCC® dyes OP 14 BLUE and OP 19 RED from New Prismatic
Enterprise Co. , Ltd., Taiwan were used as photochromic
dyes.
Polyshine Blue I was also used as photochromic dye and
is obtainable from Polychrom Co., Ltd. (Korea).
Tinuvin 326, obtainable from CIBA SC AG, Switzerland,
was also used as UV absorber:

The relative viscosity (ηrel) was measured according to
DIN EN ISO 307 in a 0.5 weight% solution in m-cresol at
a temperature of 20°C.
The glass transition temperature (Tg.) was determined
according to ISO 11357-1/2;
The differential scanning calorimetry (DSC) was carried
out with a heating rate of 2 0K/min. The values are
given for the onset.
Further inventive examples:
Further examples 14-21 are stated together with the
properties determined in them in additional table 7:

Key:
PE7313, FE7314: polyesteramide based on polyamide-12
and dimer diol; FE7314 also contains polyester segments
based on dimer acid and dimer diol.
XE3680 is a heat/ov masterbatch based on polyamide-12.
XE2828 is a polyamide-12 oligomer whose number average
molar mass is about 2000 g/mol, having mainly non-
condensable alkyl end groups.
GRILAMID L16 is a low-viscosity polyamide-12.
Results:

Haze and photochromic effect are improved via addition
of low-viscosity polyamide-12 (cf. inventive example 14
and inventive example 15).
Furthermore, addition of polyamide-12 and polyamide
oligomer permits processing of the photochromic
polyamide molding composition under gentler conditions
or incorporation of the photochromic dye into the
thermoplastic molding composition under gentler
conditions, thus permitting substantial inhibition of
degradation of the unstable photochromic dye during the
extrusion and/or injection-molding process.
The gate marks (round plaque, 70 x 2 mm) markedly
visible in inventive example 17 can be avoided by
various measures. Addition of 10% by weight or more of
a low-viscosity polyamide-12 is effective in inhibiting
formation of gate marks.
Gate marks can likewise be avoided if the ratio of
solution viscosities of the transparent
polyamide/copolyamide and of the polymer component
whose glass transition temperature is below 80°C is
smaller than 1.2, particularly smaller than 1.1 (see
inventive example 20 compared with inventive example 19
and inventive example 18 compared with inventive
example 17, and also inventive example 21).
Haze, too, decreases for identical chemical
constitution of the polymer components as the ratio of
the solution viscosities of the two polymer components
-falls. In inventive- example 19,with a ratio of 1.22
for the solution viscosities, the observed haze is 3,9,
whereas in IE20 with a lower ratio of solution
viscosities of 1.04, the result is markedly lower haze
of 1.8.
Although addition of polyamide-12 oligomer does not

necessarily always inhibit formation of gate marks, it
makes processing easier overall, by virtue of lower
melt viscosity and longer flow path.

We claim:
1. A polyamide molding composition comprising
a proportion by weight of from 50 to 99% by weight of
one or several transparent homopolyamides, one or
several copolyamides, or a combination of one or
several transparent homopolyamides and one or several
copolyamides, selected from the group consisting of:
MACM12, MACM14, MACM18, MACM12/PACM12, MACM14/PACM14,
MACM18/PACM18, 12/MACMI;
a proportion by weight of from 1 to 50% by weight of
one or several further polymers whose glass transition
temperature is below 0°C, selected from the group
consisting of: MACM36, PACM36, polyamide-12. block
copolymer with polyether soft segments, polyamide-12
block copolymer with polyester soft segments or a
combination thereof;
a proportion by weight of from 0.001 to 2.0% by weight
of at least one photochromic dye such as herein
described;
and also, optionally,
further additives selected from the group consisting
of: further dyes, stabilizers, processing aids,
plasticizers, further polymers, functional additives,
or a combination or mixture thereof,
wherein the photochromic polyamide molding composition
has a transmittance in the unexcited state of more than
80% in the wavelength range from 500 to 700 nm if
measured in the form of a thin plaque of a thickness of
2 mm, and with a haze of less than 5 if measured in the
form of a thin plaque of a thickness of 2 mm.

2. The polyamide molding composition as claimed in
claim 1, wherein the glass transition temperature of the
further polymer is in the range from (-60) - (-20)°C.
3. The polyamide molding composition as claimed in any of the preceding claims, wherein the proportion by weight
present of the transparent homopolyamide or copolyamide is
from 70 to 99% by weight.
4. The polyamide molding composition as claimed in any of
the preceding claims, wherein the proportion by weight
present of the further polymer is from 1 to 30% by weight.
5. The polyamide molding composition as claimed in any of
the preceding claims, wherein the solution viscosity (ηrel) of
the transparent homopolyamide or copolyamide is from 1.3 to
2.0.
6. The polyamide molding composition as claimed in any of
the preceding claims, wherein the photochromic dye is a dye
which is reversibly excitable with UV or short-wave VIS.
7. The polyamide molding composition as claimed in any of
the preceding claims, wherein within the additives the
stabilizers are selected to be UV stabilizers, heat
stabilizers, or free-radical scavengersor are a combination
or mixture thereof.
8. The polyamide molding composition as claimed in any of
the preceding claims, which comprises polyamide-12.
9. The polyamide molding composition as claimed in
claim 8, wherein the solution viscosity (ηrel) of the low-
viscosity polyamide-12 is from 1.5 to 2.
10. The polyamide molding composition as claimed in any of
the preceding claims, which comprises a polyamide oligomer.
11. The polyamide molding composition as claimed in
claim 10, wherein the polyamide oligomer is a polyamide-12

2. The polyamide molding composition as claimed in
claim 1, wherein the glass transition temperature of the
further polymer is in the range from (-60) - (-20)°C.
3. The polyamide molding composition as claimed in any of
the preceding claims, wherein the proportion by weight
present of the transparent homopolyamide or copolyamide is
from 70 to 99% by weight.
4. The polyamide molding composition as claimed in any of
the preceding claims, wherein the proportion by weight
present of the further polymer is from 1 to 30% by weight.
5. The polyamide molding composition as claimed in any of
the preceding claims, wherein the solution viscosity (ηrel) of
the transparent homopolyamide or copolyamide is from 1.3 to
2.0.
6. The polyamide molding composition as claimed in any of
the preceding claims, wherein the photochromic dye is a dye
which is reversibly excitable with UV or short-wave VIS.
7. The polyamide molding composition as claimed in any of
the preceding claims, wherein within the additives the
stabilizers are selected to be UV stabilizers, heat
stabilizers, or free-radical scavengersor are a combination
or mixture thereof.
8. The polyamide molding composition as claimed in any of
the preceding claims, which comprises polyamide-12.
9. The polyamide molding composition as claimed in
claim 8, wherein the solution viscosity (ηrel) of the low-
viscosity polyamide-12 is from 1.5 to 2.
10. The polyamide molding composition as claimed in any of
the preceding claims, which comprises a polyamide oligomer.
11. The polyamide molding composition as claimed in
claim 10, wherein the polyamide oligomer is a polyamide-12

oligomer whose average molar mass is from 1500 to 2500 g/mol.
12. The polyamide molding composition as claimed in any of the preceding claims, wherein the ratio of the solution
viscosities (ηrel) of the transparent homopolyamide or
copolyamide and of the further polymer whose glass transition temperature is below 0°C is smaller than 1.2.
13. A transparent article having at least one region or one
layer composed of a polyamide molding composition as claimed
in any of the preceding claims.
14. An article as claimed in the preceding claim for high- specification optical applications, whose haze is less than
3, for a thickness of the layer composed of the polyamide
molding composition of 2 mm.
15. The article as claimed in claim 13 or 14, which is a
foil, a profile, a tube, a hollow body, or an optically
variable filter or an optical lens, ski goggles, visor,
safety spectacles, photorecording, display, optical data
storage, or windows of buildings and of vehicles, or is a
decorative element or a structural element, a spectacle
frame, toy, or cover, , , a part of electronic devices, a
coating,.
16. The article as claimed in any of claims 13 to 15, which
has a color gradient or has a photochromic coating, an
antireflective coating, a scratch-resistant coating, an
optical filter coating, a polarizing coating, an oxygen-
barrier coating, or a combination of such coatings.
17. The article as claimed in any of claims 13 to 16,
wherein the glass transition temperature of the region or
the layer composed of the polyamide molding composition is
above 90°C.
1.8. The process for production of an article as claimed in
any of claims 13 to 17, which comprises molding a polyamide

molding composition as claimed in any of claims 1 to 23 in
an extrusion process, in an injection-molding process, or in
an in-mold-coating process, to give the article, where the
photochromic dye can, if appropriate, be introduced in a
downstream immersion-bath process or thermal transfer
process into the mixture composed of transparent polyamide
and of further polymer, and where the photochromic article
can also be a foil which can be applied to a substrate via
lamination or adhesive bonding.
19. The process for production of a bulk-colored molding as
claimed in claim 17, which comprises compounding the
photochromic dye such as herein described in a proportion by
weight of from 0.001 to 2.0% by weight such as herein
described together with the transparent homopolyamide or
copolyamide and with the further polymer, where the dye can
be added in the form of a liquid concentrate to the polymer
melt composed of transparent homopolyamide or copolyamide
and further polymer with the aid of a metering pump, or the
dye is applied in the form of solid to the other components
in a drum mixer, and where use may also be made, if
appropriate, of application aids.
20. The process for production of a bulk-colored molding,
as claimed in claim 18, wherein the dye and the further
polymer are processed to give a masterbatch with high color
concentration which is up to 30%, and the required amount of
this masterbatch is processed with the transparent polyamide
or copolyamide in an extruder to give pellets or is
converted directly into the finished molding in the
injection-molding machine.
21. The polyamide molding composition as claimed in claim
1, wherein the proportion by weight present of the
transparent homopolyamide or copolyamide is from 80 to 98%
by weight.
22. The polyamide molding composition as claimed in claim
1, wherein the proportion by weight present of the further
polymer is from 2 to 20% by weight.

23. The polyamide molding composition as claimed in any of
the preceding claims, wherein the solution viscosity (ηrel) of
the transparent homopolyamide or copolyamide is from-1.40 to
1.85, or its glass transition temperature Tg is above 90°C,
or above 110°C, or above 130°C.
24. The polyamide molding composition as claimed in claim
1, wherein the photochromic dye is a dye which is reversibly
excitable with UV or short-wave VIS, being a dye based on
spirooxazines.
25. The polyamide molding composition as claimed in any of
the preceding claims, wherein the functional additives are
functional additives for influencing optical properties such
as refractive index.
26. The polyamide molding composition as claimed in any of
the preceding claims, which comprises low-viscosity
polyamide-12.
27. The polyamide molding composition as claimed in
claim 26, wherein the solution viscosity (ηrel) of the low-
viscosity polyamide-12 is from 1.6 to 1.9.
28. The polyamide molding composition as claimed in claim
1, which comprises a polyamide-12 oligomer.
29. The polyamide molding composition as claimed in
claim 28, wherein the polyamide oligomer is a polyamide-12
oligomer whose average molar mass is from 1500 to
2500 g/mol, having mainly non-condensable alkyl end groups.
30. The polyamide molding composition as claimed in claim
1, wherein the ratio of the solution viscosities (ηrel) of the
transparent homopolyamide or copolyamide and of the further
polymer whose glass transition temperature is below 0°C is
smaller than 1.1.
31. A transparent, haze-free article having at least one
region or one layer composed of a polyamide molding

composition as claimed in any of the preceding claims.
32 The article as claimed in claim 13 or 14, which is an
optical lens, an ophthalmic lens, an element with spectral
filter action, a spectacle lens, sun lens, corrective lens
optical filter in the form of a switching assembly or
optical signal processing or is a decorative element or a
structural element, in the form of a spectacle frame, toy,
or cover in the form of a mobile-telephone case, a part of
electronic devices, a coating of packaging, of decorative
items, of sports equipment, or of cladding, in the
automobile sector.
33.The article as claimed in any of claims 13 to 16
wherein the glass transition temperature of the region or
the layer composed of the polyamide molding composition is
above 130°C.

ABSTRACT

PHOTOCHROMIC MOLDING COMPOSITIONS
AND ARTICLES PRODUCED THEREFROM
The invention discloses a polyamide molding composition comprising from 50 to 99% by
weight of one or several transparent homopolyamides, one or several copolyamides, or a
combination of one or several transparent homopolyamides and one or several
copolyamides, selected from the group consisting of: MACM12, MACM14, MACM18,
MACM12/PACM12, MACM14/PACM14, MACM18/PACM18, 12/MACMI; from 1 to
50% by weight of one or several further polymers whose glass transition temperature is
below 0°C, selected from the group consisting of: MACM36, PACM36, polyamide-12
block copolymer with polyether soft segments, polyamide-12 block copolymer with
polyester soft segments or a combination thereof from 0.001 to 2.0% by weight of at least
one photochromic dye such as herein described; and also, optionally, further additives
selected from the group consisting of: further dyes, stabilizers, processing aids,
plasticizers, further polymers, functional additives, or a combination or mixture thereof,
wherein the photochromic polyamide molding composition has a transmittance in the
unexcited state of more than 80% in the wavelength range from 500 to 700 am if measured
in the form of a thin plaque of a thickness of 2 mm, and with a haze of less than 5 if
measured in the form of a thin plaque of a thickness of 2 mm.
The invention is also for molded articles made with said composition.

PHOTOCHROMIC MOLDING COMPOSITIONS AND ARTICLES PRODUCED THEREFROM

Documents:

Inventors:

PCT Conventions: