HK1062572A - Multi-layer product containing polycarbonate - Google Patents

Description

Multilayer product containing polycarbonate

Technical Field

The present invention relates to multilayer products and more particularly to such products containing polycarbonate.

Background

Bisphenol A based homopolycarbonates have the disadvantage of an insufficient chemical resistance and are therefore unsuitable for some applications. This is also the case with many other polycarbonates based on dihydroxy compounds other than bisphenol A.

Copolycarbonates containing structural units derived from 4, 4' -dihydroxydiphenylene (DOD) (so-called DOD copolycarbonates, also known as DOD-CoPC) have higher chemical resistance than bisphenol A homopolycarbonate. However, these DOD-CoPCs cannot be used in some applications because they are more expensive than bisphenol A homopolycarbonates and because they are inferior to bisphenol A homopolycarbonates with respect to other properties.

Sheets with good chemical resistance are known. They are produced, for example, from polyethylene terephthalate (PET) or copolyesters such as PETG or polymethyl methacrylate (PMMA). These polymers have significantly lower notched impact values than bisphenol a based homopolycarbonates and are therefore not suitable for all applications.

The use of bisphenol a based homopolycarbonates for sheets where chemical resistance is desired is known. In these cases, a chemical resistant coating is applied to the polycarbonate or laminated with a film made of a chemical resistant material.

It is known to use blends of bisphenol a homopolycarbonate with other polymers to increase chemical resistance. In many cases, these blends have the disadvantage of being opaque or at least showing significant blurring. The transparent polycarbonate blends exhibit significantly lower notched impact values than bisphenol A homopolycarbonate.

Further prior art relating to multilayer products is outlined below.

EP-A0110221 discloses sheets consisting of two layers of polycarbonate, one of the layers containing at least 3% by weight of UV absorber. These sheets may be produced by co-extrusion.

EP-A0320632 discloses moldings composed of two layers of thermoplastics, preferably polycarbonate, one of the layers containing a specially substituted benzotriazole as UV absorber. The production of these moldings by coextrusion is also disclosed.

EP-A0247480 discloses multilayer sheets comprising a layer of a branched polycarbonate containing a specially substituted benzotriazole as UV absorber. The production of these sheets by co-extrusion is also disclosed.

EP-A0500496 discloses polymer compositions with special triazines for stabilization against UV light and their use as outer layers in multilayer systems. Examples of polymers include polycarbonates, polyesters, polyamides, polyacetals, polyphenylene ethers and polyphenylene sulfides.

EP-A0825226 discloses compositions consisting of polycarbonate, substituted aryl phosphites and substituted triazines. Also disclosed are multilayer sheets wherein one layer is comprised of the recited compositions.

JP-A02028239 discloses films composed of polyvinylidene fluoride and polymethacrylates. A disadvantage of this film is that polyvinylidene fluoride is more expensive than polycarbonate.

JP-A11323255 discloses siloxane coatings containing perfluoroalkyl additives, which can be applied to polycarbonates to improve their chemical resistance.

US-a6011124 discloses polymer mixtures (blends) consisting of polyesters and polycarbonates. The mixture has better chemical resistance than polycarbonate, but has lower notched impact resistance.

EP-A0544407, U.S. Pat. No. 5,324,324,073 and U.S. Pat. No. 5,826 disclose copolycarbonates based on bisphenol 4, 4' -dihydroxydiphenyl and 2, 2-bis- (4-hydroxyphenyl) propane. EP-A0544407, U.S. Pat. No. 5,324,073,826 and U.S. Pat. No. 5,826 further disclose that these copolycarbonates are fuel-resistant, heat-resistant and flame-retardant, and that the mechanical properties and transparency of these copolycarbonates are comparable to those of known polycarbonates.

Disclosure of Invention

A multi-layer product including a coextruded layer and a substrate layer is disclosed. The coextruded layer contains a copolycarbonate derived from a repeat unit having the following structural formula (I) and a repeat unit having the following structural formula (II):

wherein R is¹-R⁴As defined in the following,

wherein R is⁵-R⁸And X is as defined below. The substrate layer comprises polycarbonate and is characterized in that its chemical resistance is lower than the chemical resistance of the copolycarbonate. The product is characterized by an improved resistance to chemical attack. Uses of the product and a method of producing the product are also disclosed.

It is an object of the present invention to provide products which exhibit better chemical resistance than products prepared from bisphenol A homopolycarbonate.

This object is achieved by a multilayer product comprising a first and a second layer, wherein the first layer comprises a polymer having a molecular weight of from 0.1 to 46 mol%, preferably from 11 to 34 mol%, and in particular 26-Copolycarbonates of 34 mol% of one or more recurring units of the formula (I) and 99.9 to 54 mol%, preferably 89 to 66 mol% and in particular 74 to 66 mol% of one or more recurring units of the formula (II):

wherein R is¹-R⁴Independently of one another, H, C₁-C₄Alkyl, phenyl, substituted phenyl or halogen,wherein R is⁵-R⁸Independently of one another are H, CH₃Cl or Br, X is C₁-C₅Alkylene radical, C₂-C₅Alkylene (alkylene), C₅-C₆Cycloalkylene, or C₅-C₁₀A cycloalkylidene group, and wherein the total amount of repeating units according to structural formula (I) and structural formula (II) is 100 mol%, and wherein the second layer comprises a polycarbonate having a lower chemical resistance than the copolycarbonate of the first layer.

Preferably R¹-R⁴Independently of one another, H, C₁-C₄Alkyl or halogen and especially preferably all are the same, most especially all represent H or tert-butyl.

Particularly preferred copolycarbonates comprise from 34 to 26 mol%, in particular from 33 to 27 mol%, in particular from 32 to 28 mol%, most particularly from 31 to 29 mol% and most particularly 30 mol% of structural units derived from monomers of the formula (I), in each case supplemented by a complementary amount of units derived from monomers of the formula (II).

Preferred repeating units of formula (I) are derived from 4, 4 '-dihydroxybiphenyl (DOD) and 4, 4' -dihydroxy-3, 3 ', 5, 5' -tetra (tert-butyl) biphenyl.

Preferred repeating units of formula (II) are derived from 2, 2-bis- (4-hydroxyphenyl) propane, 1, 1-bis- (4-hydroxyphenyl) -3, 3, 5-trimethylcyclohexane and 1, 3-bis- [2- (4-hydroxyphenyl) -2-propyl ] benzene, 1, 1-bis- (4-hydroxyphenyl) -1-phenylethane, 1, 1-bis- (4-hydroxyphenyl) cyclohexane, especially 2, 2-bis- (4-hydroxyphenyl) propane (bisphenol A).

One repeat unit of formula (I) (forming a binary copolycarbonate) and several repeat units of formula (I) may be used.

Likewise, one repeat unit of formula (II) (forming a binary copolycarbonate) and several repeat units of formula (II) may be used.

Copolycarbonates in which the repeat unit of formula (I) is derived from 4, 4' -dihydroxybiphenyl (DOD) and in which the repeat unit of formula (II) is derived from bisphenol A are particularly preferred.

The first layer preferably has a thickness of from 1 to 1000. mu.m, in particular from 10 to 500. mu.m, more in particular from 10 to 200. mu.m, in particular from 15 to 60 μm.

The second layer may contain, in addition to other polycarbonates, a small amount, preferably less than 10 wt%, of the copolymer contained in the first layer.

The multilayer product is provided by the present invention.

The invention also provides a process for producing the multilayer product by coextrusion.

The invention also provides products containing the multilayer product. The products containing the multilayer product are preferably selected from glazing panels, protective panels, greenhouses, balconies, carports, bus stops, advertisements, shop windows, partitions, check-out booths, viewing panels (viewing panels), displays, roofs and films.

The glazing may be, for example, a glazing for an automobile or a greenhouse or a petrol station or a laboratory or chemical plant.

The protection plate may be, for example, a protection plate in a laboratory.

The protective plates can be used, for example, as a casing of the machine, protecting them from damage by flying parts that can become loose. These protective plates are used, for example, as a substitute for steel hoods.

The viewing plate may be, for example, a viewing plate in the case of a calculator or display. The illustrated viewing panels can be used, for example, in the food industry.

The definition of the amount of repeating units in the copolycarbonates according to the invention used according to the invention is shown below. The amount of n mol% refers to the amount of n mol% relative to the total amount of all repeating units present in the copolycarbonate. If the amount is 100 mol%, no other repeating unit is present.

The multilayer product according to the invention has many advantages including chemical resistance, high (notched) impact resistance and high heat resistance. In addition, it can be produced simply and inexpensively: the starting materials are light and readily available and are relatively inexpensive. Furthermore, the multilayer product according to the invention is characterized by little or no adverse change to the conventional positive properties of polycarbonate, including its good optical properties.

The multilayer product according to the invention can be produced by coextrusion. This brings advantages compared to products produced by coating. For example, there is no solvent evaporation during coextrusion, as occurs with coating methods.

In addition, coating introduces foreign polymers into the coated product. This means, for example, that the product is no longer a separate plastic for recycling. Coextrusion does not suffer from this disadvantage.

Also, the coating cannot be stored for a long time. Coextrusion does not suffer from this disadvantage.

In addition, the coating requires a complicated technique. For example, in some cases they require explosion-proof equipment, recycling of the solvent and therefore a large investment in equipment. Coextrusion does not suffer from this disadvantage.

The multilayer product according to the invention offers a number of advantages compared to products produced by lamination, since it can be produced by co-extrusion.

With lamination, the film must first be produced in a separate step. Coextrusion does not suffer from this disadvantage.

Furthermore, coextrusion is simple and the necessary expertise is readily available. Lamination is more difficult because the film can blister or warp.

Furthermore, sheets up to 2.2m in width can be easily produced by co-extrusion. In contrast, laminating films are mostly obtained only with a maximum width of 1.6 m.

Detailed Description

A preferred embodiment of the present invention is a multilayer product, wherein the recurring units of the formula (I) are derived from 4, 4' -dihydroxybiphenyl (DOD), and wherein the recurring units of the formula (II) are derived from 2, 2-bis- (4-hydroxyphenyl) propane, and wherein the amount of recurring units of the formula (I) in the copolycarbonate is from 26 to 34 mol%, and wherein the amount of recurring units of the formula (II) in the copolycarbonate is from 74 to 66 mol%, and wherein the total amount of recurring units according to the formula (I) and the formula (II) is 100 mol%.

Preferred multilayer products according to the invention are those in which one layer additionally contains from 1 to 20% by weight of a UV absorber. The UV absorber is preferably chosen from Tinuvin^ 360，Tinuvin^1577 and Uvinul^3030. They have the following structural formula: tinuvin^ 360 Tinuvin^ 1577 Univul^ 3030

The other layer preferably contains 0 to 1 wt% of a UV absorber. It may be the same or different UV absorber.

Preferred multilayer products according to the invention are selected from the group consisting of sheets, tubes, profiles and films.

The sheet material may in particular be a solid sheet material, in particular flat or corrugated. They may also be multi-layer wall sheets, which may in particular be flat or corrugated.

A multi-wall sheet is a sheet in which two outer layers are interconnected by rails, so that cavities are formed in the sheet. The double-walled sheet has two outer layers and a rail between them. The triple-walled sheet additionally has a third inner sheet which is parallel to the two outer sheets. Such a multi-layer wall sheet is described, for example, in EP-A0110238. Where they are referred to as multi-layer hollow cavity plastic sheets. EP-A0774551 also discloses multilayer wall sheets. Figure 1 of EP-a0774551 shows a three-layer wall sheet. EP-A0054856 and EP-A0741215 also disclose multilayer wall sheets. EP-A0110238, EP-A0054856, EP-A0741215 and EP-A0774551 are incorporated by reference in the present patent application.

The multi-wall sheet may be a double-wall sheet, a triple-wall sheet, a quadruple-wall sheet, or the like. The multi-wall sheet material can also have various profiles. Furthermore, the multilayer wall sheet may also be a corrugated multilayer wall sheet.

A preferred embodiment of the invention is a two-layer sheet or film comprising a first and a second layer as defined above.

A further preferred embodiment of the invention is a three-layer sheet or film, comprising one layer as intermediate layer, which is constructed as the second layer defined above, and two layers as outer layers, both of which are constructed as the first layer defined above. The multilayer product according to the invention may for example have the following structure: a)

DOD-Co-PC (with or without UV absorber)
	Other PCs (with or without UV absorbers)

b)

DOD-Co-PC (with or without UV absorber)
	Other PCs (with or without UV absorbers)
DOD-Co-PC (with or without UV absorber)

c)

DOD-Co-PC (with or without UV absorber)
	Other PCs (with 0-1% UV absorber)
Other PCs (with 0.1-20% UV absorber)

In a particular embodiment, the multilayer product is transparent.

The copolycarbonates according to the invention may be produced by known methods. The necessary monomers are known. Monomers and in some cases copolycarbonates are commercially available.

4, 4' -dihydroxybiphenyl can be produced by various known methods.

It can be reacted with OH through diphenyldisulfonic acid^-Transesterification of the ions or production by hydrolysis of dibromobiphenyl or by the methods disclosed in EP-A0432782. JP-A05097740, JP-A0415235 and JP-A03038538 also disclose processes for the production of 4, 4' -dihydroxybiphenyl.

The copolycarbonates most particularly preferably consist of 34 to 26 mol%, in particular 33 to 27 mol%, more particularly 32 to 28 mol%, most particularly 31 to 29 mol% and most particularly 30 mol% of recurring units of the formula (I), in each case supplemented with a complementary amount of recurring units of the formula (II).

Preferred repeating units of formula (I) are derived from 4, 4 '-dihydroxybiphenyl (DOD) and 4, 4' -dihydroxy-3, 3 ', 5, 5' -tetra (tert-butyl) biphenyl.

Preferred repeating units of formula (II) are derived from 2, 2-bis- (4-hydroxyphenyl) propane, 1, 1-bis- (4-hydroxyphenyl) -3, 3, 5-trimethylcyclohexane and 1, 3-bis- [2- (4-hydroxyphenyl) -2-propyl ] benzene, 1, 1-bis- (4-hydroxyphenyl) -1-phenylethane, 1, 1-bis- (4-hydroxyphenyl) cyclohexane, especially 2, 2-bis- (4-hydroxyphenyl) propane (bisphenol a).

One compound of formula (I) (forming a binary copolycarbonate) and several compounds of formula (I) may be used.

Likewise, one compound of formula (II) (forming a binary copolycarbonate) and several compounds of formula (II) may be used.

The educts of the formulae (I) and (II) may of course contain impurities resulting from the synthesis. However, high purity is desirable, which is the target that should be sought, and therefore these educts are used in the highest possible purity.

Hereinafter, the first layer of the multilayer product according to the invention is also referred to as coextruded layer. The second layer is also referred to as the base layer.

Both the coextruded layer and the substrate layer may contain additives, especially UV absorbers and thermal stabilizers.

The UV absorber or mixtures thereof are preferably present in the coextruded layer in a concentration of from 0 to 20% by weight. 0.1 to 20% by weight is preferred, particularly preferably 2 to 10% by weight, most particularly preferably 3 to 8% by weight. If two or more such layers are present, the amount of UV absorber present in the layers may vary.

Examples of UV absorbers which can be used according to the invention are described below.

a) Benzotriazole derivatives according to formula (III)Biology:

in the structural formula (III), R and X are the same or different and represent H or an alkyl or alkylaryl group.

The following are preferred:

Tinuvin^329 wherein X is 1, 1, 3, 3-tetramethylbutyl and R is H

Tinuvin^350, wherein X ═ tert-butyl and R ═ 2-butyl

Tinuvin^234, wherein X ═ R ═ 1, 1-dimethyl-1-phenyl,

b) dimeric benzotriazoles according to structural formula (IV):

wherein R is¹And R²Independently represent H, halogen, C₁-C₁₀Alkyl radical, C₅-C₁₀Cycloalkyl radical, C₇-C₁₃Aralkyl radical, C₆-C₁₄Aryl, -OR⁵Or- (CO) -O-R⁵Wherein R is⁵H or C₁-C₄An alkyl group, a carboxyl group,

and R³And R⁴Independently represent H, C₁-C₄Alkyl radical, C₅-C₆Cycloalkyl, benzyl or C₆-C₁₄An aryl group, a heteroaryl group,

and m represents 1, 2 or 3 and n is 1, 2, 3 or 4.

The following are preferred:

Tinuvin^360, wherein R¹＝R³＝R⁴＝H，n＝4，R²1, 1, 3, 3-tetramethylbutyl and m-1.

b1) A dimeric benzotriazole derivative according to structural formula (y):

wherein the bridging group represents

R¹、R²M and n have the meanings listed for (IV), p is an integer from 0 to 3, q is an integer from 1 to 10,

y is equal to-CH₂-CH₂-，-(CH₂)₃-，-(CH₂)₄-，-(CH₂)₅-，-(CH₂)₆-, or CH (CH)₃)-CH₂-，

And R³And R⁴Have the meanings listed for the structural formula (II).

The following are preferred:

Tinuvin^840, wherein R¹＝H，n＝4，R²T-butyl, m 1, R²Attached in ortho-position to the OH group, R³＝R⁴＝H，p＝2，Y＝-(CH₂)₅-，q＝1。

c) A triazine derivative according to structural formula (VI):

wherein R in the formula (VI)¹、R²、R³、R⁴Independently is H or alkyl or aryl, or CN or halogen, and X is alkyl.

The following are preferred:

Tinuvin^1577 wherein R¹＝R²＝R³＝R⁴H, X-hexyl,

Cyasorb^UV-1164, wherein R¹＝R²＝R³＝R⁴Methyl, X-octyl,

d) a triazine derivative having the structural formula (VIa):

wherein

R¹Is represented by C₁-C₁₇An alkyl group, a carboxyl group,

R²represents H or C₁-C₄Alkyl or aryl, and

n is equal to 0-20.

e) A diaryl cyanoacrylate having the structural formula (VII):

wherein R is¹-R⁴⁰Independently represents H, alkyl, CN or halogen.

Uvinul^3030 wherein R is¹-R⁴⁰H is preferred.

f) A diaryl cyanoacrylate having the structural formula (VIII):

wherein R is C₂-C₁₀Alkyl or aryl.

Wherein R ═ C₂H₅Uvinul of^3035, and wherein R ═ CH₂CH(C₂H₅)C₄H₉Uvinul of^3039 is preferred.

Some of these UV absorbers are commercially available.

In addition to the UV stabilizers, the coextruded layers and the substrate layer may also contain other conventional processing aids, especially release agents and flow control agents, as well as conventional stabilizers in polycarbonate, especially heat stabilizers, as well as dyes and optical brighteners and inorganic pigments.

Particularly suitable are P-containing heat stabilizers such as phosphines, phosphites and phosphonites. Particularly suitable are, for example, triphenylphosphine, diphenylalkyl phosphites, phenyldialkyl phosphites, tris (nonylphenyl) phosphite, trilauryl phosphite, trioctadecyl phosphite, distearylpentaerythritol diphosphite, tris (2, 4-di-tert-butylphenyl) phosphite, diisodecyl pentaerythritol diphosphite, bis (2, 4-di-tert-butylphenyl) pentaerythritol diphosphite, bis (2, 6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, diisodecyl pentaerythritol oxide diphosphite, bis (2, 4-di-tert-butyl-6-methylphenyl) pentaerythritol diphosphite, bis (2, 4, 6-tris (tert-butylphenyl)) pentaerythritol diphosphite, tristearyl sorbitol triphosphite, tetrakis (2, 4-di-tert-butylphenyl) -4, 4' -biphenylene diphosphonite, 6-isooctyloxy-2, 4, 8, 10-tetra-tert-butyl-12H-dibenzo [ d, g ] -1, 3, 2-dioxaphosphosine, 6-fluoro-2, 4, 8, 10-tetra-tert-butyl-12-methyl-dibenzo [ d, g ] -1, 3, 2-dioxaphosphosine, bis- (2, 4-di-tert-butyl-6-methylphenyl) methyl phosphite, bis- (2, 4-di-tert-butyl-6-methylphenyl) ethyl phosphite, 6-fluoro-2, 4, 8, 10-tetra-tert-butyl-12-methyldiphenyl [ d, g ] -1, 3, 2-dioxaphosphorine, 2, 2 ', 2 "-nitrilo [ triethyltris- (3, 3 ', 5, 5 ' -tetra-tert-butyl-1, 1 ' -biphenyl-2, 2 ' -diyl) phosphonite ], 2-ethylhexyl- (3, 3 ', 5, 5 ' -tetra-tert-butyl-1, 1 ' -biphenyl-2, 2 ' -diyl) phosphonite, 5-butyl-5-ethyl-2- (2, 4, 6-tri-tert-butylphenoxy) -1, 3, 2-dioxaphosphorine. A single compound or a mixture thereof may be used.

Tris (2, 4-di-tert-butylphenyl) phosphite (Irgafos)^168, Ciba-Geigy), triphenylphosphine or (2, 4, 6-tri-tert-butylphenyl) - (2-butyl-2-ethylpropane-1, 3-diyl) phosphite (Ultranox 641)^GE Specialty Chemical) is particularly preferred.

Other examples of suitable phosphites and phosphonites are:

the polycarbonates used for the second layer of the multilayer product of the invention are all polycarbonates having a lower chemical resistance than the copolycarbonates of the coextruded layer.

They include homopolycarbonates, copolycarbonates and thermoplastic polyester carbonates, preferably having an average molecular weight M of from 18,000 to 40,000, more preferably from 26,000 to 36,000 and in particular from 28,000 to 35,000_WDetermined by measuring the relative solution viscosity in dichloromethane or in a mixture of the same weight of phenol/o-dichlorobenzene and calibrating with light scattering.

As a method for producing Polycarbonates, reference may be made, as examples, to "Schnell, Chemistry and Physics of Polycarbonates, Polymer Reviews, Vol.9, Interscience Publishers, New York, London, Sydney 1964", and "D.C.PREVORSEK, B.T.DEBONA and Y.KESTEN, Corporation research Center, Allied Chemical Corporation, Motorwn, New Jersey 07960, 'Synthesis of Polymer (ester) carbonate readers', Journal of Polymer Science, Polymer Science edition, Vol.19, 75-90 (1980)", and "D.Freetag, U.G.G., P.R.M. handbell, N.G. Nobel, N.1992, Vol.19, 75-90 (1980)" and "D.Freetag, U.G.S.G, P.R.M. lake, cell research, cell AG, cell 19, cell pages 11, cell research, cell pages 11, cell III.

The production of the polycarbonates is preferably carried out by the interfacial polycondensation process or the melt transesterification process, which is described below using the interfacial polycondensation process as an example.

Preferred starting compounds are bisphenols of the general formula HO-Z-OH, wherein Z is a divalent organic radical having 6 to 30 carbon atoms and containing one or more aromatic groups.

Examples of such compounds are bisphenols belonging to the classes of the dihydroxybiphenyls, the bis (hydroxyphenyl) alkanes, the 1, 2-indane bisphenols, the bis (hydroxyphenyl) ethers, the bis (hydroxyphenyl) sulfones, the bis (hydroxyphenyl) ketones and the alpha, alpha' -bis (hydroxyphenyl) diisopropylbenzenes.

Particularly preferred diphenols belonging to the group of compounds listed above are bisphenol A, tetraalkylbisphenol A, 4, 4- (M-phenylenediisopropyl) diphenol (bisphenol M), 4, 4- (p-phenylenediisopropyl) diphenol, 1, 1-bis- (4-hydroxyphenyl) -3, 3, 5-trimethylcyclohexane (BP-TMC) and optionally mixtures thereof.

The bisphenol compounds used according to the invention are preferably reacted with carbonic acid compounds, in particular phosgene, or, in the case of the melt transesterification process, diphenyl carbonate or dimethyl carbonate.

The polyester carbonates are preferably obtained by reacting the bisphenols listed above, at least one aromatic dicarboxylic acid and optionally carbonic acid equivalents. Examples of suitable aromatic dicarboxylic acids are phthalic acid, terephthalic acid, isophthalic acid, 3, 3 '-or 4, 4' -biphenyldicarboxylic acid and benzophenonedicarboxylic acid. A portion, up to 80 mol%, preferably from 20 to 50 mol%, of the carbonate groups in the polycarbonate may be replaced by aromatic dicarboxylic acid ester groups.

Examples of inert organic solvents used in the interfacial polycondensation process are dichloromethane, various dichloroethane and chloropropane compounds, tetrachloromethane, trichloromethane, chlorobenzene and chlorotoluene; chlorobenzene or dichloromethane or mixtures of dichloromethane and chlorobenzene are preferably used.

The interfacial polycondensation reaction can be accelerated by catalysts such as tertiary amines, especially N-alkylpiperidines or onium salts. Tributylamine, triethylamine and N-ethylpiperidine are preferably used. In the melt transesterification process, the catalysts listed in DE-A4238123 are preferably used.

Polycarbonates can be deliberately branched in a controlled manner by using small amounts of branching agents. Some suitable branching agents are: phloroglucinol, 4, 6-dimethyl-2, 4, 6-tris- (4-hydroxyphenyl) heptene-2; 4, 6-dimethyl-2, 4, 6-tris- (4-hydroxyphenyl) heptane; 1, 3, 5-tris- (4-hydroxyphenyl) benzene; 1, 1, 1-tris- (4-hydroxyphenyl) ethane; tris- (4-hydroxyphenyl) phenylmethane; 2, 2-bis- [4, 4-bis- (4-hydroxyphenyl) cyclohexyl ] propane; 2, 4-bis- (4-hydroxyphenylisopropyl) phenol; 2, 6-bis- (2-hydroxy-5' -methylbenzyl) -4-methylphenol; 2- (4-hydroxyphenyl) -2- (2, 4-dihydroxyphenyl) propane; hexa- (4- (4-hydroxyphenylisopropyl) phenyl) ortho-phthalate; tetrakis- (4-hydroxyphenyl) methane; tetrakis- (4- (4-hydroxyphenylisopropyl) phenoxy) methane; α, α', α "-tris- (4-hydroxyphenyl) -1, 3, 5-triisopropylbenzene; 2, 4-dihydroxybenzoic acid; 1, 3, 5-trimellitic acid; cyanuric chloride; 3, 3-bis- (3-methyl-4-hydroxyphenyl) -2-oxo-2, 3-indoline; 1, 4-bis- (4', 4 "-dihydroxytriphenyl) methyl) benzene and in particular: 1, 1, 1-tris- (4-hydroxyphenyl) ethane and bis- (3-methyl-4-hydroxyphenyl) -2-oxo-2, 3-indoline.

0.05 to 2 mol%, relative to the diphenols used, of branching agents or mixtures of branching agents which may be introduced may be added together with the diphenols, but may also be added at a later stage of the synthesis.

Phenols, such as phenol, alkylphenols, such as cresol and 4-tert-butylphenol, chlorophenol, bromophenol, cumylphenol or mixtures thereof are preferably used as chain terminators in amounts of from 1 to 20 mol%, preferably from 2 to 10 mol%, per mol of bisphenol. Phenol, 4-tert-butylphenol or cumylphenol is preferred.

Chain terminators and branching agents may be added to the synthesis either separately or together with the bisphenols. A process for the production of polycarbonates by the melt transesterification process is described, for example, in DE-A4238123.

Preferred polycarbonates according to the invention for the second layer of the multilayer product according to the invention are homopolycarbonates based on bisphenol A, homopolycarbonates based on 1, 1-bis- (4-hydroxyphenyl) -3, 3, 5-trimethylcyclohexane and copolycarbonates based on the two monomers bisphenol A and 1, 1-bis- (4-hydroxyphenyl) -3, 3, 5-trimethylcyclohexane.

Homopolycarbonates based on bisphenol A are particularly preferred.

The polycarbonate may contain a stabilizer. Suitable stabilizers are, for example, stabilizers containing phosphines, phosphites or silicon and other compounds described in EP-A0500496. Triphenyl phosphite, diphenyl alkyl phosphites, phenyl dialkyl phosphites, tris (nonylphenyl) phosphite, tetrakis- (2, 4-di-tert. -butylphenyl) -4, 4' -biphenylene diphosphonite and triaryl phosphites may be mentioned as examples. Triphenylphosphine and tris- (2, 4-di-tert-butylphenyl) phosphite are particularly preferred.

These stabilizers may be present in all layers of the multilayer product according to the invention. In other words, they are contained both in the so-called base layer and in the so-called coextruded layer. Different additives or additive concentrations may be present in each layer.

The multilayer product according to the invention may also comprise from 0.01 to 0.5% by weight of esters or partial esters of monohydric to hexahydric alcohols, in particular glycerol, pentaerythritol or Guerbet alcohols.

Monohydric alcohols are, for example, stearyl alcohol, palmityl alcohol and guerbet alcohol.

An example of a dihydric alcohol is ethylene glycol.

An example of a trihydric alcohol is glycerol.

Examples of tetrahydric alcohols are pentaerythritol and mesoerythritol.

Examples of pentahydric alcohols are arabitol, ribitol and xylitol.

Examples of hexahydroxy alcohols are mannitol, glucitol (sorbitol) and dulcitol.

The esters are preferably saturated aliphatic C₁₀-C₃₆Monocarboxylic acids and optionally hydroxymonocarboxylic acids, preferably saturated aliphatic C₁₄-C₃₂Mono-, di-, tri-, tetra-, penta-and hexa-esters of monocarboxylic acids and optionally hydroxymonocarboxylic acids or mixtures thereof, especially random mixtures.

Commercially available fatty acid esters, in particular of pentaerythritol and glycerol, may contain < 60% of various partial esters due to the production process.

Saturated aliphatic monocarboxylic acids having 10 to 36C atoms are, for example, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, hydroxystearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid and octacosanoic acid.

Preferred saturated aliphatic monocarboxylic acids having 14 to 22C atoms are, for example, myristic acid, palmitic acid, stearic acid, hydroxystearic acid, arachidic acid and behenic acid.

Saturated aliphatic monocarboxylic acids such as hexadecanoic acid, stearic acid and hydroxystearic acid are particularly preferred.

Saturated aliphatic C₁₀-C₃₆The carboxylic acids and fatty acid esters per se are known from the literature or can be produced by methods known from the literature. Examples of pentaerythritol fatty acid esters are those of the above-mentioned particularly preferred monocarboxylic acids.

Esters of pentaerythritol and glycerol with stearic acid and palmitic acid are particularly preferred.

Esters of Guerbet alcohols and glycerol with stearic acid and palmitic acid and optionally hydroxystearic acid are also particularly preferred.

These esters may be present in both the substrate layer and the coextruded layer. Different additives or concentrations may be present in each layer.

The multilayer product according to the invention may contain an antistatic agent.

Examples of antistatic agents are cationic compounds, such as quaternary ammonium, phosphonium or sulfonium salts, anionic compounds, such as alkylsulfonates in the form of alkali metal salts or alkaline earth metal salts, alkylsulfates, alkylphosphates, carboxylates, nonionic compounds, such as polyethylene glycol esters, polyethylene glycol ethers, fatty acid esters, ethoxylated fatty amines. Preferred antistatic agents are nonionic compounds.

These antistatic agents may be present in both the substrate layer and the coextruded layer. Different additives or concentrations may be present in each layer. They are preferably used in coextruded layers.

The multilayer products according to the invention may contain organic dyes, inorganic color pigments, fluorescent dyes and especially preferably optical brighteners.

These colorants may be present in both the base layer and the coextruded layer. Different additives or concentrations may be present in each layer. All moulding compositions for producing the multilayer products according to the invention, their raw materials and solvents can be contaminated with the corresponding impurities which occur as a result of the production and storage conditions, with the aim of working with the purest possible starting materials.

The individual components can be mixed in a known manner, continuously and simultaneously, and also at room temperature and elevated temperature.

The additives, in particular the UV absorbers and the other abovementioned additives, are preferably incorporated into the molding compositions according to the invention in a known manner by mixing the polymer granules with the additives at temperatures of from about 200 to 330 ℃ in conventional apparatus such as internal mixers, single-screw extruders and twin-shaft extruders, for example by melt compounding or melt extrusion, or by mixing the polymer solution with a solution of the additives and subsequently evaporating the solvent in a known manner. The content of additives in the molding composition can vary within wide limits and is controlled by the desired properties of the molding composition. The total content of additives in the molding composition is preferably up to about 20% by weight, preferably from 0.2 to 12% by weight, relative to the weight of the molding composition.

It is also possible, for example, to prepare the coating by reacting a solution of the UV absorber and optionally further additives mentioned above with the plastic in a suitable organic solvent, for example CH₂Cl₂A solution of halogenated alkane, halogenated aromatic compound, chlorobenzene and xylene to introduce the UV absorber into the molding composition. The substance mixture is then preferably passed through in a known mannerExtrusion for homogenization; the solution mixture is preferably removed in a known manner by evaporation of the solvent, followed by extrusion, e.g. compounding.

As shown in the examples, the use of the coextrusion molding compositions according to the invention offers significant advantages for polycarbonate molding compositions which have an inadequate chemical resistance as base material.

The multilayer products according to the invention can be processed, for example, by thermoforming or by surface treatment, such as the application of scratch-resistant coatings, water-spreading layers and the like, and also the products produced by these methods are provided by the invention.

Co-extrusion per se is known from the literature (see, for example, EP-A0110221 and EP-A0110238). In this case, the process is preferably performed as follows. The extruder was connected to a coextrusion joint to form the core and outer layers. The joint is designed in such a way that the melt forming the outer layer adheres as a thin layer to the melt of the core. The multilayer melt strand produced in this way is then transferred in the desired form (multilayer wall sheet or solid sheet) to an adjacent die. The melt is then cooled by calendering (solid sheet) or vacuum forming (multi-wall sheet) under controlled conditions by known methods and then cut to length. Optionally, a conditioning oven may be connected after the setting stage to relieve stress. Instead of a joint being attached before the die, the die itself can also be designed in such a way that the melt is pooled.

The invention is further illustrated by the following non-limiting examples. The examples according to the invention only describe preferred embodiments of the invention.

Examples

The material referred to hereinafter as DOD-CoPC is a polycarbonate derived from 30 mol% dihydroxybiphenyl (DOD) and 70 mol% bisphenol A (MVR7.1) produced by an interfacial polycondensation process. The chain terminator is 4-tert-butylphenol.

The products according to the invention were prepared and their properties were evaluated. The substrate layer was in each case composed of a material at 300 deg.CAnd 1.2kg of Makrolon having a Melt Flow Rate (MFR) under load (measured according to ISO 1133) of 6.5g/10min^3103 (UV-protected linear homopolycarbonate based on bisphenol A, product of Bayer AG, Lerverkusen, Germany) with a thickness of 4 mm.

The composition of the coextruded layers is shown below:

example a-Makrolon 3100 (product of bayer ag (MFR ═ 6.5g/10min), based on homopolycarbonate of linear bisphenol a).

Example B-Makrolon 3100 and 0.25 wt% Tinuvin 329

Example C-DOD-CoPC

Example D-DOD-CoPC and 0.25 wt% Tinuvin 329.

The thickness of each coextruded layer is about 50 μm,

*Tinuvin^329 is 2- (2-hydroxy-5-tert-octylphenyl) benzotriazole, a product of Ciba Spezialitatenchemie, Lampertheim, Germany.

The following describes a machine and an apparatus for producing a multilayer solid sheet.

The device comprises the following components:

screw with length 33D and diameter 60mm and main extruder with aeration

Coextrusion adapter (feeder head system)

Coextruder for applying an external layer having a screw of length 25D and diameter 30mm

Special sheet extrusion dies with a width of 350mm

Calendering device

-roller conveyor belt

-an accessing device

-revolving knife (saw)

-a stockpiling table.

The polycarbonate granules forming the base material were fed to the feed hopper of the main extruder and the coextrusion material was fed to the feed hopper of the coextruder. In each case, the material is melted and conveyed in a corresponding plasticizing system (cylinder/screw). The two material melts were combined together in a coextrusion joint and formed a composite after exiting the die and cooling in a calender. Another device is used to transport, size cut and stack the coextruded sheets.

The test pieces were tested for resistance to various chemicals found in the home by the following tests:

a double-sided tape (5mm wide) was attached to a sheet of 110 mm. times.35 mm. times.4 mm to make a 4.5 cm. times.2.5 cm interval. After spreading onto an outer fiber strain template ("No. 99"; outer fiber strain 2%, 4mm sheet according to DIN 53449 Part 3), a piece of cotton cloth of 3cm x 1cm soaked in test medium was placed in the center of the section and covered with aluminum foil. Since the sheet is wider than the template, the onset and progression of cracking can be easily discovered from behind.

The table below indicates that the sheets according to the invention (C and D) have better resistance to the chemicals found in the household than the comparative sheets a and B.

A comparison of tests with premium fuels shows that the sheets according to the invention surprisingly show a higher resistance to household chemicals than to fuels.

	Time of exposure	Sheet material A	Sheet material B	Sheet C	Sheet material D
						With high-quality fuel1)Tests carried out	20min	A large amount of severe cracking	A large amount of severe cracking	A large amount of severe cracking	A large amount of severe cracking
By using skin-care cream2)Tests carried out	30min	Fine cracking	Fine cracking	Without cracking	Without cracking
						By cold-pressing olive oil3)Tests carried out	2h	Some severe cracking	Some severe cracking	Without cracking	Without cracking
With flavourings4)Tests carried out	2h	Fracture of	Fracture of	Several deepCracking of	Several deep cracks

1) Premium fuel from Shell

2) KG from Physioderm GmbH & Co

3) The manufacturer: oleificio R.M.S.P.A.Lucca, Italy (trade name of TIP)

4) Jil Sander Woman III (containing water, ethanol and essential oils, among others).

Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

Claims (8)

1. A multilayer product comprising a coextruded layer and a substrate layer, wherein the coextruded layer comprises a copolycarbonate derived from 0.1 to 46 mole percent of one or more repeat units of formula (I) and 99.9 to 54 mole percent of one or more repeat units of formula (II):wherein R is¹-R⁴Independently represent H, C₁-C₄Alkyl, phenyl, substituted phenyl or halogen,

wherein R is⁵-R⁸Independently represent H, CH₃Cl or Br, X is C₁-C₅Alkylene radical, C₂-C₅Alkylene radical, C₅-C₆Cycloalkylene, or C₅-C₁₀A cycloalkylidene group, wherein the total amount of repeating units according to structural formula (I) and structural formula (II) is 100 mol%, and wherein the substrate layer comprises a polycarbonate characterized in that its chemical resistance is lower than the copolycarbonate.

2. The product according to claim 1, wherein formula (I) represents 4, 4' -dihydroxybiphenyl (DOD) and formula (II) represents 2, 2-bis- (4-hydroxyphenyl) propane, and wherein the amount of recurring units of formula (I) is 26 to 34 mol% and the amount of recurring units of formula (II) is 74 to 66 mol%.

3. The product according to claim 1, wherein the substrate layer comprises a polycarbonate selected from the group consisting of homopolycarbonates based on bisphenol a, homopolycarbonates based on 1, 1-bis- (4-hydroxyphenyl) -3, 3, 5-trimethylcyclohexane and copolycarbonates based on bisphenol a and 1, 1-bis- (4-hydroxyphenyl) -3, 3, 5-trimethylcyclohexane.

4. The product according to claim 1, wherein the substrate layer comprises a homopolycarbonate based on bisphenol a.

5. A product according to claim 1 in a form selected from the group consisting of sheet, pipe, profile and film.

6. The product according to claim 1, wherein the coextruded layer additionally contains 0.1 to 20% by weight of a UV absorber.

7. The product according to claim 6, wherein the UV absorber conforms to a formula selected from the group consisting of:

8. method for producing a product according to any of claims 1 to 7, comprising co-extruding the co-extruded layer and the substrate layer.