|Title of Invention||
A PROCESS FOR THE PRODUCTION OF A MULTI-LAYER COMPOSITE
|Abstract||Multilayer composites are obtained with good quality, in particular with good layer thickness distributions and good wall thickness distributions, when using a molding composition which comprises the following components: a) 100 parts by weight of polyamide and b) from 0.005 to 10 parts by weight of a compound having at least two carbonate units for co extrusion with a molding composition based on a high-melting-point polymer whose crystallite melting point T m is at least 255°C and/or whose glass transition temperature Tg is at least 180°C.|
Use of a polyamide molding composition with high melt stiffness for coextrusion with a high-melting-point polymer
The present invention relates to the use of a polyamide molding composition with high melt stiffness for coextrusion with a molding composition based on a high-melting-point polymer. The invention also relates to a process for coextrusion of a multilayer composite from a polyamide molding composition with high melt stiffness and from a molding composition based on a high-melting-point polymer, and also relates to the multilayer composites produced therewith.
For the purposes of this invention, high-melting-point polymers are polymers which can be processed only at high temperatures. If the material is a semi crystalline polymer, the crystallite melting point Tm, measured by means of DSC to ISO 11357, is at least 270°C. In the case of an amorphous polymer, the glass transition temperature Tg5 likewise measured by means of DSC to ISO 11 357, is at least 190°C. Extrusion of both types of polymer at a speed sufficient for cost-effectiveness is possible only at temperatures around 300°C or there above.
When polyamides, such as PA 12, are coextruded with HT polymers of this type, various difficulties can arise due to the high extrusion temperatures and to the attendant markedly reduced stiffness of the polyamide melt. An excessive difference in melt viscosities leads to instabilities of the layer boundaries, to poor layer thickness distributions and poor wall thickness distributions, and to unsatisfactory overall quality of the extrudate.
For this reason, there have been previous developments in which the melting point of, for
example, ETFE (crystallite melting point Tm about 270°C; processing temperature from 300
to 340°C) has been reduced in order to achieve coextrudability with lower-melting-point
polymers, such as PA12. An example of a result of these developments is provided by soft
ETFE (e.g. Neoflon RP7000 from Daikin, Japan) whose crystallite melting point is about
255°C and whose recommended processing temperature is from 280 to 290°C, or the EFEP
type of polymer (e.g. Neoflon RP5000 from Daikin), whose crystallite melting point is about
195°C and whose processing temperature is from about 240 to 285°C. Within that processing
latitude, the stiffness of a melt of an extrusion molding composition based on PA12 is sufficient to achieve coextrudability with soft ETFE and, respectively, EFEP, to give sufficient quality. However, when ETFE is modified it has to be accepted that performance is impaired, for example barrier action with respect to fuels.
Our own studies have shown that it is also difficult to achieve coextrusion with other high-melting-point polymers, e.g. PPS, because of the problems described above.
The object underlying the invention consisted in eliminating the abovementioned disadvantages.
This object has been achieved via the use of a molding composition which comprises the following components:
a) 100 parts by weight of polyamide and
b) from 0.005 to 10 parts by weight of a compound having at least two carbonate units
for coextrusion with a molding composition based on a high-melting-point polymer whose crystallite melting point Tm is at least 270°C and/or whose glass transition temperature Tg is atleast 190°C.
WO 00/66650 discloses a polyamide molding composition of this type. That document describes the use of compounds having at least two carbonate units for modification of polyamides by condensation, permitting reliable and stable establishment of properties and
providing the possibility of undertaking repeated processing of the material modified by condensation, without resultant gelling or inhomogeneity. Brüggemann KG markets the product Brüggolen Ml251, which is an additive based on this principle for molecular weight adjustment of polyamides. Main applications are in the viscosity adjustment sector for recycled material composed of PA6 or PA66, this material being recycled in molding
compositions for extrusion. The additive Brüggolen Ml251 is a masterbatch of a low-viscosity polycarbonate, such as Lexan 141, in an acid-terminated PA6. A reaction between
the polycarbonate and the amino end groups present in the material to be modified by condensation is the cause of the increase in molecular weight.
A polyamide suitable for the purposes of the invention is based on lactams, on
aminocarboxylic acids, or on diamines and, respectively, dicarboxylic acids. It can moreover
contain units which have branching effect and which have been derived by way of example
from tricarboxylic acids, from triamines, or from polyethyleneimine. Examples of suitable
types, in each case in the form of homopolymer or in the form of copolymer are PA6, PA66,
PA610, PA66/6, and particularly PA612, PA1010, PA1012, PA1212, PA613, PA614,
PA1014, PAH, PA12 or a transparent polyamide. Examples of transparent polyamides that
can be used are:
the polyamide composed of terephthalic acid and of the isomer mixture composed of
2,2,4- and 2,4,4-trimethylhexamethylenediamine, the polyamide composed of isophthalic acid and 1,6-hexamethylenediamine,
the copolyamide composed of a mixture composed of terephthalic acid/isophthalic
acid and 1,6-hexamethylenediamine,
the copolyamide composed of isophthalic acid, 3,3 ‘-dimethyl-4,4’-diamino-
dicyclohexylmethane and laurolactam or caprolactam,
- the (co)polyamide composed of 1,12-dodecanedioic acid, 3,3’-dimethyl-4,4’-
diaminodicyclohexylmethane and, if desired, laurolactam or caprolactam,
the copolyamide composed of isophthalic acid, 4,4’-diaminodicyclohexylmethane
and laurolactam or caprolactam,
the polyamide composed of 1,12-dodecanedioic acid and 4,4’-diaminodicyclo- hexylmethane,
the copolyamide composed of a terephthalic acid/isophthalic acid mixture, 3,3’-
dimethyl-4,4’-diaminodicyclohexylmethane and laurolactam.
Other suitable materials are polyetheramides based on lactams, on aminocarboxylic acids, on 30 diamines, on dicarboxylic acids, and on polyetherdiamines, and/or on polyetherdiols.
The molecular weights Mn of the starting compounds are preferably greater than 5000, in particular greater than 8000. Polyamides used here are those whose end groups at least to some extent take the form of amino groups. By way of example, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% of the end groups take the
form of amino end groups. Preparation of polyamides with relatively high amino end group content is prior art, using diamines or polyamines as regulator. In the present case, when preparing the polyamide it is preferable to use an aliphatic, cycloaliphatic, or araliphatic diamine having from 4 to 44 carbon atoms as regulator. Examples of suitable diamines are hexamethylenediamine, decamethylenediamine, 2,2,4- or 2,4,4-
trimethylhexamethylenediamine, dodecamethylenediamine, 1,4-diaminocyclohexane, 1,4- or 1,3-dimethylaminocyclohexane, 4,4’-diaminodicyclohexylmethane, 4,4’-diamino-3,3’-dimethyldicyclohexylmethane, 4,4t-diaminodicyclohexylpropane, isophoronediamine, metaxylylidenediamine, or paraxylylidenediamine.
In another preferred embodiment, when the polyamide is prepared a polyamine is used as regulator and branching agents are used simultaneously. Examples here are diethylenetriamine, l,5-diamino-3-((3-aminoethyl)pentane, tris(2-aminoethyl)amine, N,N-bis(2-aminoethyl)-N’,N’-bis[2-[bis(2«aminoethyl)amino]ethyl]-1,2-ethanediamine, dendrimers, and also polyethyleneimines, particularly branched polyethyleneimines obtainable via
polymerization of aziridines (Houben-Weyl, Methoden der Organischen Chemie [Methods of organic chemistry], Volume E20, pages 1482-1487, Georg Thieme Verlag Stuttgart, Germany, 1987) and which generally have the following amino group distribution: from 25 to 46% of primary amino groups, from 30 to 45% of secondary amino groups, and
from 16 to 40% of tertiary amino groups.
In the inventive process, at least one compound having at least two carbonate units is used in a quantitative proportion of from 0.005 to 10% by weight, calculated in relation to the polyamide used. This ratio is preferably in the range from 0.01 to 5.0% by weight, particularly preferably in the range from 0.05 to 3% by weight. The term “carbonate” here means an ester of carbonic acid, in particular with phenols or with alcohols.
The compound having at least two carbonate units can be a low-molecular-weight, oligomeric, or polymeric compound. It can be composed entirely of carbonate units, or can have other units as well. These are preferably oligo- or polyamide, -ester, -ether, -etheresteramide, or -etheramide units. These compounds can be prepared via known oligo- or polymerizationprocesses and via polymer-analogous reactions.
In one preferred embodiment, the compound having at least two carbonate units is a polycarbonate, for example based on bisphenol A, or is a block copolymer that contains a polycarbonate block of that type.
WO 00/66650, which is expressly incorporated herein by way of reference, gives a detailed description of suitable compounds having at least two carbonate units, and also of suitable masterbatches.
If the compound used as additive having at least two carbonate units is fed in the form of a masterbatch, this permits more precise metering of the additive, because the amounts used are relatively large. It has moreover been found that use of a masterbatch achieves improved extrudate quality. The masterbatch preferably encompasses, as matrix material, the polyamide which is also modified by condensation in the inventive process, or a polyamide compatible
therewith, but is also possible that under the reaction conditions incompatible polyamides undergo partial linkage to the polyamide to be modified by condensation, the result being compatibilization. The molecular weight Mn of the polyamide used as matrix material in the masterbatch is preferably greater than 5000 and particularly greater than 8000. Preference is given here to those polyamides whose end groups mainly take the form of carboxylic acid
groups. By way of example, at least 80%, at least 90%, or at least 95% of the end groups take the form of acid groups.
The concentration of the compound having at least two carbonate units in the masterbatch is preferably from 0.15 to 50% by weight, particularly preferably from 0.2 to 25% by weight, and with particular preference from 0.3 to 15% by weight. This masterbatch is prepared in the conventional manner known to the person skilled in the art.
The invention can be used with polyamides which as a result of their preparation comprise at least 5 ppm of phosphorus in the form of an acidic compound. In this case, prior to the compounding process or during the compounding process from 0.001 to 10% by weight, based on the polyamide, of a salt of a weak acid is added to the polyamide molding composition. DE-A-103 37 707 discloses suitable salts, and is expressly incorporated herein by way of reference.
However, the invention is just as useful with polyamides which as a result of their preparation comprise less than 5 ppm of phosphorus or no phosphorus at all in the form of an acidic compound. In this case, it is possible but not essential to add an appropriate salt of a weak acid.
According to the invention, it is possible to use the conventional additives used in preparation of polyamide molding compositions. Illustrative examples of these are colorants, flame retardants, stabilizers, fillers, lubricants, mold-release agents, impact modifiers, plasticizers, crystallization accelerators, antistatic agents, processing aids, and also other polymers which are usually compounded with polyamides.
Examples of these additives are the following:
Colorants: titanium dioxide, white lead, zinc white, lithopones, antimony white, carbon black, iron oxide black, manganese black, cobalt black, antimony black, lead chromate, minium, zinc yellow, zinc green, cadmium red, cobalt blue, Prussian blue, ultramarine, manganese violet, cadmium yellow, Schweinfurter green, molybdate orange, molybdate red, chrome orange,
chrome red, iron oxide red, chromium oxide green, strontium yellow, molybdenum blue, chalk, ocher, umbra, green earth, burnt sienna, graphite, or soluble organic dyes.
Flame retardants: antimony trioxide, hexabromocyclododecane, tetrachloro- or
tetrabromobisphenol, halogenated phosphates, borates, chloroparaffms, and also red
phosphorus, and stannates, melamine cyanurate and its condensates, such as melam, melem,
melon, melamine compounds, such as melamine pyro- and polyphosphate, ammonium
polyphosphate, aluminum hydroxide, calcium hydroxide, and also organophosphorus compounds which contain no halogens, e.g. resorcinol diphenyl phosphate or phosphonic esters.
Stabilizers: metal salts, in particular copper salts and molybdenum salts, and also copper complexes, phosphites, sterically hindered phenols, secondary amines, UV absorbers, and HALS stabilizers.
Lubricants: M0S2, paraffins, fatty alcohols, and also fatty acid amides.
Mold-release agents and processing aids: waxes (montanates), montanic acid waxes, montanic ester waxes, polysiloxanes, polyvinyl alcohol, S1O2, calcium silicates, and also perfluoropolyethers.
Plasticizers: BBSA, POBO.
Impact modifiers: polybutadiene, EPM, EPDM, HDPE, acrylate rubber.
Antistatic agents: carbon black, carbon fibers, graphite fibrils, polyhydric alcohols, fatty acid esters, amines, amides, quaternary ammonium salts.
Other polymers: ABS, polypropylene.
The amounts that can be used of these additives are those which are conventional and known to the person skilled in the art.
The crystallite melting point Tm of the high-melting-point polymer is preferably in each case at least 255°C, 260°C, 265°C, 270°C, 275°C, 280°C, 285°C, 290°C, 295°C or 300°C, and/or its glass transition temperature is preferably in each case at least 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, 235°C, 240°C, or 245°C. This amount present in the molding composition based on this polymer is at least 50% by weight,
at least 55% by weight, at least 60% by weight, at least 65% by weight, at least 70% by weight, at least 75% by weight, or at least 80% by weight.
Examples of suitable high-melting-point polymers are:
- fluoropolymers, such as polytetrafluoroethylene (PTFE), tetrafluoroethylene- hexafluoropropene copolymers (FEP), or ethylene-tetrafluoroethylene copolymers (ETFE);
- polyamides and copolyamides, such as PA46, PA66, PA9T, PA12T, PA66/6T, PA6/6T, or PA6T/MPMDT (MPMD being 2-methylpentamethylenediamine);
-polyether ketones, such as PEEK, PEKK or PEK;
- liquid-crystalline polymers (LCP), such as liquid-crystalline polyesters;
-polyphenylene sulfide (PPS);
- polyether sulfones;
- polyetherimides, and also
- syndiotactic polystyrene.
If necessary, the layer adhesion between the polyamide molding composition and the molding composition based on the high-melting-point polymer can be achieved via use of a suitable adhesion promoter.
The molding composition composed of polyamide and of the compound having at least two carbonate units can be prepared in advance and be used in this form for the coextrusion process. In one preferred embodiment, however, this molding composition is prepared in situ during processing.
The invention accordingly also provides a process for production of a multilayer composite
a) a polyamide molding composition being provided,
b) a premix of the polyamide molding composition and from 0.005 to 10 parts by weight of the compound having at least two carbonate units, based on 100 parts by weight of
polyamide, being prepared,
c) the mixture being stored and/or transported, if desired, and
d) the mixture then being coextruded with the molding composition based on the high- melting-point polymer.
Surprisingly, it has been found that with this type of addition a significant increase in melt stiffness occurs during processing, while at the same time processing pressures are moderate and load on the motor is low. Despite high melt viscosity, therefore, high throughputs can be achieved in processing, with a resultant improvement in the cost-effectiveness of the production process.
In the process according to the claims, the compound having at least two carbonate units is added undiluted or in the form of a masterbatch only after the compounding process, but at the latest during processing. When processing is carried out, it is preferable that the polyamide to
be modified by condensation or the polyamide molding composition to be modified by condensation is mixed in the form of pellets with the pellets of the compound having at least two carbonate units or the appropriate masterbatch. However, it is also possible to prepare a mixture of pellets of the finished compounded polyamide molding composition with the compound having at least two carbonate units or with the masterbatch, and then to transport or
store this and then to process it. A corresponding process can also be carried out with powder mixtures, of course. A decisive factor is that the mixture is not melted until processing has begun. Thorough mixing of the melt during processing is to be recommended. However, in an equally successful method, the masterbatch can also be fed in the form of a melt stream with the aid of an auxiliary extruder into the melt of the polyamide molding composition to be
processed, and can then be incorporated by thorough mixing.
The invention also provides the multilayer composites produced using the polyamide molding composition of the claims or by the process of the claims. Examples of these multilayer composites are profiles, among which are flat profiles and hollow-chamber profiles, supply lines, such as service-station supply lines, vent lines, air intake pipes, tank filler necks, fuel lines, tank ventilation lines, crankcase-ventilation lines, coolant lines, brake-air lines,
hydraulic lines (clutch and brake), cable ducts, cable sheathing, flat films, blown films, sheets, storage tanks, bottles, or fuel tanks. These moldings and sheathing can be produced by way of example via coextrusion including sequential coextrusion or coextrusion blow molding, for example suction blow molding, 3 D blow molding, parison-insertion processes and parison- manipulation processes. These processes are prior art. It is also possible to produce the multilayer composite with the aid of what is known as the Conex process. This is a coextrusion process, the individual layers being applied to one another in a manner comparable with that in a winding process (WO 97/28949).
In one advantageous embodiment, an inventive multilayer pipe can be provided with two caps, for example those described in the utility model DE 20 2004 004 753 Ul. Glass- or aramid-fiber-containing tapes or rovings are then wound around the pipe. This gives a lightweight, reduced-permeation storage tank for gases and liquids.
Examples of suitable layer configurations in the inventive pipe, from the outside to the inside, are the following, PA representing the polyamide molding composition of the claims, HT representing the molding composition based on a high-melting-point polymer, and AP representing adhesion promoter:
PA/HT/HT (electrically conductive)
PA/HT/PA/PA (electrically conductive)
The electrical conductivity of the inner layer can be achieved as in the prior art by way of example via compounding to incorporate an effective amount of conductive carbon black, of graphite fibrils, or of other conductivity additives into the respective molding composition.
The invention will be explained by way of example below. The following materials were used in the experiments:
Amine-regulated PA12 having 50 meq/kg of NH2 groups and 9 meq/kg of COOH groups, ηrel
Acid-regulated PA12 having 8 meq/kg of NH2 groups and 50 meq/kg of COOH groups, ηrel
Brüggolen® M1251, a mixture composed of a low-viscosity polycarbonate and of acid-terminated PA6.
Ceasit® PC (calcium stearate).
The compositions stated in Table 1 were prepared in a Werner & Pfleiderer ZSK 30 twin-screw extruder.
Table 1: Preparation of compositions for further use
Comparative Example 1 and Inventive Examples 1 to 3:
The stiffness of the melt of the compositions stated in Table 2 was tested at 240°C and, respectively, 300°C, using an elongation rheometer.
Elongation rheometers can measure the extensibility of melts at constant draw-off rate or with constant or exponential acceleration of the drawn-off strand (M. H. Wagner, A. Bernat, V. Schulze, Kautschuk Gummi Kunststoffe, volume 50, No. 9/97; M. H. Wagner, V. Schulze, A. Gottfert, Polymer Engineering and Science, Mid-April 1996, Vol. 36, No. 7).
The equipment used here was a single-screw laboratory extruder from GÖttfert with max. ) 30 rpm and with downstream draw-off apparatus. The starting materials stated in Table 2 were processed in the extruder, starting from pellets or from a pellet mixture. The emergent strand was stretched to break-off by the draw-off apparatus at various speeds, the torque needed for this purpose being measured; from this the draw-off force was calculated. The results are shown in Table 2.
It is seen that according to the invention the melt stiffness obtained at 300°C is about the same as or indeed higher than for a conventional PA12 molding composition at the typical processing temperature of 240°C. The polyamide molding composition prepared according to the invention can therefore be used advantageously at temperatures in the region of 300°C and ) above for coextrusion with high-melting point polymers.
Table 2: Extension rheometer measurements
|Indian Patent Application Number||1152/CHE/2006|
|PG Journal Number||47/2013|
|Date of Filing||04-Jul-2006|
|Name of Patentee||EVONIK DEGUSSA GMBH|
|Applicant Address||RELLINGHAUSER STRASSE 1-11, 45128 ESSEN,|
|PCT International Classification Number||B29C47/00|
|PCT International Application Number||N/A|
|PCT International Filing date|