|Title of Invention||
A COMPOSITE PART
|Abstract||The invention relates to a film with a top layer made of a moulding compound consisting essentially of the following components: (a) 3 to 50 wt.% of a polyamide selected from groups PA 11 and PA 12, and (b) 50 to 97 wt.% of a polyamide selected from groups PA1012 and PA 1212, the percentages relating to the total of components (a) and (b). The film is suitable for decorating mouldings that retain their gloss throughout their useful life.|
Polyamide blend film
The present invention relates to a foil which comprises a layer composed of a polyamide blend, and is suitable for decoration of moldings.
The current standard process for decoration of external areas on automobiles is painting. However, this procedure firstly generates high manufacturing costs, resulting from provision of specific plant and the operating cost associated therewith for the automobile producer, and secondly causes pollution of the environment. Pollution of the environment derives by way of example from solvent constituents released from the paints used, and also from accumulation of paint residues, which have to follow correct disposal routes.
Another factor is that painting has only limited suitability for decorating the surfaces of plastics components, which in recent years have become more popular in automobile construction, because of the saving in weight and cost.
The process of painting plastics components which are components of bodywork can, for example, be carried out on-line, the plastics part being subjected to a paint treatment identical with that for the metallic components. This leads to a uniform color, but is attended by high temperatures resulting from the cathodic electrodeposition method conventional here, and this makes the selection of material more difficult. In addition, identical adhesion of the paint formulation has to be ensured on very different substrates. If the process of painting the plastics parts is carried out in a separate step (known as off-line painting), comprising process conditions more advantageous for plastics, the problem of colormatching arises, meaning that the shade achieved on the metal has to be matched precisely. However, the differences in substrate and in the underlying paint formulation that can be used, and process conditions, make this very difficult to achieve. If there is a color difference prescribed via the design, a serious disadvantage that remains is provision of a second set of painting equipment for the plastics parts and the cost associated therewith, and additional time required for manufacture of the automobile also has to be considered. Direct use of the untreated, generally injection-molded plastics parts is aesthetically disadvantageous, because surface defects resulting from the process, such as weld lines, air inclusions, and also necessary reinforcing fillers, such as glass fibers, are clearly discernible here. This is intolerable in visible regions. Consequently,
improvement of surface quality has to be undertaken, for example in the context of a painting process, frequently requiring much work for pretreatment via polishing and application of relatively thick layers of a primer.
One proposed solution consists in the use of multilayered plastics foils, used to cover the components and then requiring no painting. The bond between substrate and decorating foil here can be achieved via a number of manufacturing processes. By way of example, the foil can be laminated to the substrate, or it is possible to select a process of reverse coating by an injection-molding process, in which the foil is placed in the injection mold during component production. The concept of a foil as carrier of decoration is also in line with a trend toward individualization of design elements on automobiles. Specifically, this trend leads to a wider range of models in the manufacturing process, but with a reduction in the number of respective components manufactured per series. The use of foils permits rapid, problem-free design change, and can therefore meet this challenge. An important factor here is that the foil complies with the standards demanded in the automobile industry with respect to surface properties (class A surface), solvent resistance, and appearance. These foils likewise have good capability for use in the design of interior surfaces in automobiles.
Decorative foils of this type are in principle known. EP 0 949 120 Al describes by way of example decorative foils with a transparent outer layer composed of polyurethane, polyacrylate, fluoropolymer, or mixtures composed of fluoropolymer and polyacrylate. WO 94/03337 and EP 0 285 071 A2 disclose similar decorative foils.
Another application sector for decorative foils is as a carrier of decoration, for example for topcoats of sports equipment, e.g. skis or snowboards, or of household items. Single-layer foils whose topsides or undersides have been printed are often used here. For example, the utility model DE 295 19 867 Ul describes a decorable foil composed of a copolyamide which is composed of the following monomer units: laurolactam, and also caprolactam and/or hexamethylenediamine/dicarboxylic acid. The article by M. Beyer and J. Lohmar, Kunststoffe 90 (2000) 1, pp. 98 - 101 gives examples of printable foils composed of PA12 molding compositions.
The property profile of polyamides, for example impact resistance and chemical resistance, very generally gives them, and in particular polyamides based on PA12 or PAH, good suitability for production of these decorative foils. Accordingly, the patent literature has descriptions of decorative foils or else protective foils which comprise an outer layer composed of a polyamide. Examples which may be mentioned here are the specifications JP60155239A, JP2003118055A, EP 1 302 309 A, EP 0 522 240 A, EP 0 694 377 A, EP 0 734 833 A, WO 9212008 A, and EP 0 568 988 A.
While high polarity of outer layers composed of polyamides with a high density of carboxamide groups gives them inadequate chemicals resistance and excessive water absorption, in practice it is found that use of polyamides which have a low density of carboxamide groups and which have been prepared from lactams or from the corresponding aminocarboxylic acids (AB polyamides) leads to formation of deposits on the surface of the foils under ambient conditions over the course of time, these deposits considerably reducing gloss and being unacceptable for this application. Improvement in transparency and in initial gloss would also be desirable. If, in contrast, polyamides composed of diamine and dicarboxylic acid (AABB polyamides) which have a low density of carboxamide groups are used, no deposits are formed, but here again an improvement in transparency and gloss would be advantageous.
It was therefore an object, for decorative purposes, to provide a foil which gives reduced deposit formation, and whose outer layer is sufficiently transparent, and which has high initial gloss.
This object is achieved via a foil whose outer layer is composed of a molding composition which is in essence composed of the following components:
a) from 3 to 50%, preferably from 4 to 49% by weight, particularly preferably from 5 to 47% by weight, and with particular preference from 10 to 45% by weight, of a polyamide, selected from the group of PA11 and PA12, and
b) from 50 to 97%, preferably from 51 to 96% by weight, particularly preferably from 53 to 95% by weight, and with particular preference from 55 to 90% by weight, of a polyamide, selected from the group of PA1012 and PA1212,
where the percentages are based on the entirety of components a) and b).
The polyamides used and their preparation are known. They are commercially available in a wide variety of marketed grades. According to the invention, the respective homopolyamides are mainly used, but it is also possible to use copolyamides based thereon and incorporating at most 20mol%, at most 15 mol%, at most 10mol%, or at most 5 mol%, of comonomers. Suitable comonomers are lactams, the corresponding aminocarboxylic acids, or the combination of diamine and dicarboxylic acid. Diamine and dicarboxylic acid are respectively counted individually in the calculation of the constitution.
Incorporation of comonomers leads to improved transparency and to higher gloss, but there is some impairment of resistance to chemicals and to environmental effects. The latter can be accepted if use of the comonomers is successful in giving better compatibility for example with respect to the following layer or with respect to the substrate, by bringing the constitution somewhat closer.
The molding composition is prepared from the individual components according to the prior art via mixing in the melt. It can also comprise the following other components:
a) nucleating agents, selected from nanoscale fillers and basic metal salts, metal oxides, or metal hydroxides; the amount added of the latter, in order to ensure the desired transparency, is at most that which can be dissolved in the melt by reaction with the carboxy end groups of the polyamides;
b) conventional auxiliaries and conventional additives, the amounts being those conventional for polyamide molding compositions, examples being stabilizers or lubricants,
c) colorants which do not significantly affect transparency,
d) fillers whose refractive index differs only to a very slight extent from that of the matrix,
or is precisely identical (isorefractive fillers), and also
e) other polymer components whose refractive index differs only very slightly from that of
the matrix or is precisely identical.
The amount of these other components present in the molding composition is preferably at most 30% by weight, at most 25% by weight, at most 20% by weight, at most 15% by weight, at most 10% by weight, or at most 5% by weight.
Surprisingly, if the molding composition comprises at most 50% by weight of the AB polyamide (PAl 1 or PA12), gloss is retained as for the pure AABB polyamides during service life, although this would not be expected in view of the mixing ratio of the polyamides. Apparently, as long as at least 50% by weight of the AABB polyamide is present, it inhibits diffusion of the substances that form deposits and are present in the AB polyamide, possibly cyclic oligomers. Another advantage here is that the mixture of the semicrystalline polyamides give blends which are semicrystalline, but sufficiently transparent. Transparency and initial gloss are above the level of the pure components, while resistance to chemicals and environmental effects is retained. Explicit mention may be made here of the combinations PA11/PA1012, PA11/PA1212, PA12/PA1012, and PA12/PA1212, but the AB component can moreover be, independently of one another, a mixture of PAH and PAl2, and the AABB component a mixture of PA1012 and PAl212.
The foil is a single- or multilayer foil. In the case of a multilayer structure, the nature and number of the other layers depend on the technical requirements of the application; the only decisive factor is that the outer layer is composed of the inventively used molding composition. By way of example, the following embodiments are possible:
1. The foil is a single-layer foil. In this case it is defined as composed only of the outer layer; decorative effects can be applied either to the topside or to the underside via printing, e.g. by means of thermal sublimation printing.
2. The foil comprises not only the'outer layer but also a lower color layer. The color layer can be a paint layer; however, as in the prior art it is preferably composed of a colored thermoplastics layer. The thermoplastic can by way of example be a mixture identical with or similar to that of the outer layer, one component thereof, or another polyamide, or another polymer, which either adheres directly to the outer layer or has been adhesive-bonded with the aid of a sufficiently transparent adhesion promoter (for example a polyolefin functionalized by carboxy or anhydride groups or by epoxy groups, a thermoplastic polyurethane, or a blend composed of the constituents of the layers to be bonded). Examples of colorants that may be used are organic dyes, inorganic or organic pigments, or metal flakes.
3. The foil comprises not only an outer layer and, if appropriate, a color layer, but also another layer which, as carrier layer, brings about sufficient mechanical strength and, if appropriate, also brings about coupling to the substrate.
4. The foil comprises not only the outer layer and, if appropriate, a color layer, but also a lower adhesion-promoter layer for coupling to the substrate. Examples of suitable adhesion promoters are a polyolefin functionalized by carboxy or anhydride groups or by epoxy groups, a thermoplastic polyurethane, a blend composed of the materials of the layer to be bonded and of the substrate, or one of the adhesion promoters disclosed in the German patent application No. 102004029217.5 of 16.06.2004.
5. The foil comprises not only the outer layer, and, if appropriate, a color layer and carrier layer, but also a lower adhesion-promoter layer for coupling to the substrate. The comments made under item 4 again apply to the adhesion promoter.
6. The foil, e.g. a foil in one of items 1 to 5, also comprises, if necessary, for example in the case of increased scratch-resistance requirements, a protective layer, such as a polyurethane-based clear lacquer, on the outer layer. A protective layer in the form of a lacquer can also have been modified as in the prior art in order to increase scratch resistance. Besides this, another possibility is to generate a protective layer by way of
vacuum deposition processes. The foil can, if appropriate, also comprise a peelable protective foil applied by lamination, which provides protection during transport or installation, and which is peeled away after production of the composite part.
In the case of embodiments 2 to 6, the transparent outer layer may first, like a monofoil, be printed from one side or from both sides and then be bonded in a second step to the other layers to give the multilayer foil. In multilayer foils, the transparent outer layer can be printed from above. The outer layer may also have transparent or opaque coloring.
In one preferred embodiment, the color layer and/or the carrier layer comprises a molding composition in particular of a polyetheramide or of a polyetheresteramide, and preferably of a polyetheramide or polyetheresteramide based on a linear aliphatic diamine having from 6 to 18, preferably from 6 to 12, carbon atoms, on a linear aliphatic, or an aromatic, dicarboxylic acid having from 6 to 18, preferably from 6 to 12, carbon atoms, and on a polyether having an average of more than 2.3 carbon atoms per oxygen atom and having a number-average molecular weight of from 200 to 2000 for the polyether blocks. The molding composition of this layer can comprise other blend components, e.g. polyacrylates or polyglutarimides having carboxy or anhydride groups or epoxy groups, a rubber containing functional groups, and/or a polyamide. Molding compositions of this type are prior art; by way of example, they are described in EP 1 329 481 A2 and DE-A 103 33 005, expressly incorporated herein by way of reference. In order to ensure good layer adhesion, it is advantageous here for the polyamide content of the polyamide elastomer to be composed of monomers which are identical with those used in one of the components of the outer layer. As an alternative to the polyamide elastomers, the color layer and/or the carrier layer can also comprise a conventional impact-modifying rubber alongside a polyamide. An advantage of these embodiments is that in many cases there is no need for any thermoforming of the foil as a separate step prior to reverse coating by an injection-molding method, because reverse coating by an injection-molding method also simultaneously subjects the foil to a forming process.
In one preferred embodiment, the thickness of the foil or multilayer foil with the inventive outer layer is from 0.02 to 1.2 mm, particularly preferably from 0.05 to 1 mm, very
particularly preferably from 0.1 to 0.8 mm, and with particular preference from 0.2 to 0.6 mm. If the material is a multilayer foil, the thickness of the inventive outer layer in one preferred embodiment is from 0.01 to 0.5 mm, particularly preferably from 0.02 to 0.3 mm, very particularly preferably from 0.04 to 0.2 mm, and with particular preference from 0.05 to 0.15 mm. The foil is produced by means of known methods, for example via extrusion, or in the case of multilayered systems via coextrusion or lamination. It can then, if appropriate, be subjected to a forming process.
In one embodiment, the foil is a decorative foil. For the purposes of the invention, decorative foils are foils which can be printed and/or comprise a color layer, and moreover are intended for bonding to a substrate in order to decorate its surface. The decoration can also be brought about by using a lamination process on visual surface defects, e.g. by hiding surface roughness deriving from fillers or from reinforcing materials.
Examples of methods of coherent bonding of the foil to the substrate are adhesive bonding, pressing, lamination, or coextrusion, or reverse coating by an injection-molding, foaming, or compression-molding method. In order to achieve better adhesion, the foil can by way of example be previously flame-treated or treated with a plasma. Prior to formation of the bond between foil and substrate, the foil can also be subjected to mechanical treatment or forming processes, e.g. via thermoforming or other processes. The surface can be structured via embossing, for example. The surface can also be pre-structured in the context of foil extrusion, for example using specifically designed rolls. The resultant composite part can then also be subjected to a forming process.
Examples of suitable substrates are molding compositions based on polyolefins, on polyamides, on polyesters, on polycarbonates, on ABS, on polystyrene, or on styrene copolymers.
In one preferred embodiment, the inventive foil is used as outer layer of a foil composite for the design or decoration of surfaces on and in automobiles and utility vehicles, the foil having been adhesive-bonded to a plastics substrate. The correspondingly designed component can be
of sheet-like structure, an example being a bodywork part, for example a roof module, wheel surround, engine cover, or door. Other possible embodiments are those in which the components produced are elongate, with or without curvature, for example cladding, e.g. the cladding on what are known as A columns of an automobile, or decorative and cover strips of any type. Another example is provided by protective cladding for door sills. Alongside applications in motor-vehicle exteriors, constituents of the interior can also be advantageously decorated via the inventive foils, in particular decorative elements such as strips and panels, because impact resistance and resistance to chemicals, such as cleaners, is also required in the interior.
In another preferred embodiment, the inventive foil is used as topcoat for snowboard-like equipment of any type, such as skis or snowboards.
The foil can moreover be used by way of example as a protective foil to counter soiling, UV radiation, effects of weathering, chemicals, or abrasion, or as a barrier foil on vehicles, in the household, on floors, on tunnels, on tents, and on buildings, or as a carrier of decorative effects, for example for topcoats of sports equipment, of boats, of aircraft, in the household, or on buildings.
The invention is illustrated below by way of example.
The PA12 used was a grade whose relative solution viscosity r|rei, determined to ISO 307, was 2.1 and whose crystallite melting point Tm, determined to ISO 11357, was 178°C.
The PA1012 used was a grade whose relative solution viscosity Tirei was 1.9 and whose crystallite melting point Tm was 191 °C.
The molding composition was prepared via mixing in the melt in a Werner + Pfleiderer ZSK M9/2 twin-screw extruder. The barrel temperature was 250°C, the rotation rate was 250 rpm, and the throughput was 10 kg/h. The melt was filtered at 25 /i.
Injection-molded plaques were produced on an Engel ES 600/150 injection molding machine. The melt temperature was 250°C, and the mold temperature was 80°C. Dimensions of the plaques produced were 130 mm x 130 mm x 1 mm.
Monofoils were produced by the calendering process on a Collin 168/400 multilayer foil calender at a processing temperature of 240°C. The thickness was 400 /zm.
Monofoils were produced by the calendering process on a Collin 168/400 multilayer foil calender at a processing temperature of 240 °C (outer layer) and 240 - 250°C (color layer). The thickness of the outer layer was 100 jam, and the thickness of the color layer was 400 /mi. The colorant layer used comprised a blend composed of 28.0% by weight of PA12 (r|rei = 2.1), 68.5% by weight of a polyetheresteramide having PA12 hard blocks (Mn = 7000) and having PTHF soft blocks (Mn = 1000), and 2.0% by weight of a stabilizer masterbatch, and also 1.5% by weight of color powder masterbatch, the color used being E70237.
Accelerated weathering was carried out on monofoils, using Q-UV/se accelerated-weathering equipment from Q-Panel with a cycle (Step 1: 55°C, exposure to light at 0.98 W/m2 at 340 nm, 4 h/Step 2: 45°C, water condensation in dark conditions, 4 h).
Injection-molded plaques were stored in a cabinet under controlled temperature and humidity conditions at 85°C and 99% relative humidity.
Gloss measurements were carried out on plaques and foils to DIN 67 530.
Transmittance was measured on foils of thickness 400 fim to ISO 13468-2.
Inventive examples 1-4 and comparative examples A - E: Tables 1 to 5 give constitutions and results.
What is claimed is:
1. A foil whose outer layer is composed of a molding composition which is in essence
composed of the following components:
a) from 3 to 50% by weight of a polyamide, selected from the group of PAl 1 and PA12, and
b) from 50 to 97% by weight of a polyamide, selected from the group of PA1012 and PA1212,
where the percentages are based on the entirety of components a) and b).
2. The foil as claimed in claim 1, which is composed only of that layer.
3. The foil as claimed in claim 1, which is composed of two or more layers.
4. The foil as claimed in claim 3, characterized in that
it comprises a color layer, a carrier layer, and/or an adhesion-promoter layer.
5. The foil as claimed in claim 4,
characterized in that
the color layer and/or the carrier layer comprises a polyamide elastomer or an impact-modifying rubber.
6. The foil as claimed in any of the preceding claims,
characterized in that
its thickness is from 0.02 to 1.2 mm.
7. The foil as claimed in any of claims 1 or 3 to 6,
characterized in that
the thickness of the outer layer is from 0.01 to 0.5 mm.
8. The foil as claimed in any of claims 1 to 7,
characterized in that
it is produced via extrusion, coextrusion, or lamination, and is then, if appropriate, formed.
9. The use of a molding composition which in essence is composed of the following
a) from 3 to 50% by weight of a polyamide, selected from the group of PA11 and PA12,
b) from 50 to 97% by weight of a polyamide, selected from the group of PA1012 and
where the percentages are based on the entirety of components a) and b),
for production of a foil as claimed in any of claims 1 to 8.
10. A composite part, composed of a foil as claimed in any of claims 1 to 8 and of a substrate.
11. The composite part as claimed in claim 10,
characterized in that
it is a bodywork part of a motor vehicle, a constituent of the motor-vehicle interior, a cladding, a decorative strip, a cover strip, a panel, or a decorative element.
12. The composite part as claimed in claim 10 or 11,
characterized in that
it is produced via adhesive-bonding, pressing, lamination, or coextrusion, or via reverse
|Indian Patent Application Number||3623/CHENP/2007|
|PG Journal Number||23/2012|
|Date of Filing||20-Aug-2007|
|Name of Patentee||EVONIK DEGUSSA GMBH|
|Applicant Address||BENNIGSENPLATZ 1, 40474 DUSSELDORF|
|PCT International Classification Number||C08L 77/02|
|PCT International Application Number||PCT/EP06/50038|
|PCT International Filing date||2006-01-04|