Moulding Compositions of Graft Polycarbonate and Graft Polymer Rubbers

This invention relates to thermoplastic moulding compositions comprising:

1. 70 - 20%, by weight, of graft polycarbonates in which the graft stock is a vinyl polymer with a molecular weight of from 10,000 to 100,000 which contains from 3 to 10 side chains attached by carbon, each side chain containing a hydroxyphenyl group, on which aromatic polycarbonate chains are condensed, and

2. 30 - 80%, by weight, of graft polymer rubbers obtained by polymerising a mixture of:

2.1. 50 - 90%, by weight, of styrene, .alpha.-methylstyrene, methyl methacrylate or mixtures thereof, and

2.2. 10 - 50%, by weight, of acrylonitrile, methacrylonitrile, methylmethacrylate or mixtures thereof on a diene or acrylate rubber.

Graft polycarbonates (1):

These products are already known in principle from German Offenlegungsschriften 1,950,982 and U.S. Pat. No. 3,687,895. To obtain these products, the graft stock is first produced. This is a copolymer preferably produced by the conventional method of radical initiated polymerisation from one or more ethylenically unsaturated compounds (in principle any compounds of this type) and one aromatic hydroxy compound which is copolymerisable by an olefinically unsaturated substituent.

The preferred ethylenically unsaturated compounds are aromatic vinyl compounds, e.g. styrene, .alpha.-methylstyrene, vinyl naphthalene; acrylic and methacrylic acid derivatives, e.g. their nitriles, (acrylonitrile, methacrylonitrile), and C.sub.1 - C.sub.6 alkyl esters (methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, hexyl acrylate, butyl methacrylate), and vinyl esters of aliphatic carboxylic acids (vinyl acetate, vinyl propionate).

Two of these monomers may be used together, e.g. styrene and acrylonitrile (preferably in weight ratios of from 90:10 to 50:50) or one monomer may be used alone, e.g. methylmethacrylate.

The preferred polymerisable aromatic hydroxy compounds are those which correspond to the following formula: ##SPC1##

Wherein

R = H, C.sub.1 -C.sub.4 alkyl;

R.sub.1 = H, Cl, Br, C.sub.1 -C.sub.4 alkyl, cycloalkyl, C.sub.1 -C.sub.4 alkoxy;

N = 0, 1, 2; ##SPC2##

Examples of suitable polymerisable aromatic hydroxy compounds include, e.g. p-isopropenylphenol and 2-(hydroxyphenyl)-2-(p-isopropenylphenyl)-propane.

In general, from 1 to 10, preferably from 2 to 5, mols of polymerisable aromatic hydroxyl compound are used per 100 mols of total monomers in the copolymerisation to obtain the graft stock. The copolymers obtained generally have a molecular weight (determined by osmosis), of from 10,000 to 40,000 and contain from 3 to 10 hydroxyl groups per molecule.

The graft stock is then reacted with aromatic dihydroxy compounds or mixtures thereof, preferably di-(hydroxyphenyl)alkanes, 2,2-di-(p-hydroxyphenyl)-propane (bisphenol A), tetrachlorobisphenol A or tetrabromobisphenol A, (halogenated bisphenol A yielding flame resistant products), and phosgene or other carbonic acid derivatives under conditions of polycarbonate formation. It is essential in this reaction that the reaction mixture should contain at least 1 mol of hydroxy compound and at least 1 mol of phosgene (or other carbonic acid derivative), per mol of OH groups in the graft stock so that all the OH groups in the stock will be grafted with polycarbonate. The reaction follows the known method of preparing polycarbonates and has already been described in principle in German Offenlegungsschriften 1,770,144 and 1,950,982.

Graft polymer rubbers (2):

These graft copolymers are also known (see British Pat. No. 794,400).

They are obtained, for example, by radical emulsion polymerisation of graft monomers (2.1) and (2.2) in the presence of a rubber latex. The following rubbers are particularly suitable for the purpose of this invention: polybutadiene, butadiene/styrene copolymers, butadiene/acrylate copolymers, and polyacrylates. The term "acrylate", as used herein denotes C.sub.1 - C.sub.6 alkyl esters of acrylic and methacrylic acid, e.g. ethyl acrylate, methyl methacrylate or butyl acrylate. The rubbers, particularly if they are copolymers, may also contain small quantities (up to approximately 10% by weight) of other monomers. These additional monomers used may inter alia be methacrylamide, methacrylamidomethylol ether, acrylic acid, divinylbenzene or ethylene glycol dimethacrylate, depending on the nature of the rubber. As a general rule, from 10 to 200 parts by weight of monomer are grafted on 100 parts by weight of rubber. Grafting is generally not complete so that only part of the monomers are graft polymerised on the rubber and a separate copolymer of these monomers is obtained as a second product. This is generally a resin-like material. If desired, only a part of the total monomers may be polymerised in the presence of the rubber and the remainder may be added as a separately polymerised resin. It is essential that the resulting mixture has a rubber content of from 5 to 40% by weight and that sufficient monomers are actually graft polymerised on the rubber to render the grafted rubber compatible with the resin.

Moulding compositions of the following components are particularly preferred:

10 - 100% by weight of a graft polymer of

10 - 90 parts by weight of a monomer mixture of

50 - 90% by weight styrene and

50 - 10% by weight acrylonitrile, on

90 - 10 parts by weight of polybutadiene, a copolymer of butadiene and acrylonitrile, (optionally containing small quantities of methacrylic acid and/or divinylbenzene), or polybutylacrylate, (optionally containing small quantities of methacrylamidomethylol ether) and

0 - 90% by weight of a resin-like copolymer of

50 - 90% by weight styrene and

50 - 10% by weight acrylonitrile.

The term "graft polymer rubber", as used herein, denotes not only the graft polymer proper but also mixtures of the graft polymer proper with copolymers which have either been prepared separately from the graft monomers or have been formed from them during the grafting reaction.

The moulding compositions according to the invention contain from 70 to 20% by weight of graft polycarbonate and from 30 to 80% by weight of graft polymer rubber. They may be obtained by the conventional method of mixing the two components, using mixing apparatus such as rubber mills, internal kneaders or double shaft extruders. The moulding compositions may also contain fillers, glass fibres, pigments and the conventional additives, e.g. stabilisers, flame-retarding agents, fluidizing agents or lubricants. They may be processed particularly easily by injection moulding for example, they are suitable for manufacturing moulded products such as parts of housings. They differ from similar mixtures which do not contain grafted polycarbonates by the exceptional ease with which they may be processed and, in particular, by their improved resistance to alkalies and to hot water.

The products are also improved in their dynamic characteristics.

a. Graft polycarbonates, having a relative viscosity of 1.304, prepared by grafting 90 parts, by weight, of an aromatic polycarbonate based on bisphenol A on 10 parts, by weight, of a copolymer consisting of 78 parts, by weight, styrene, 17 parts, by weight, acrylonitrile and 5 parts, by weight, isopropenylphenol;

b. graft polycarbonate, having a relative viscosity (.eta..sub.rel) = 1.28 prepared by grafting 80 parts, by weight, of an aromatic polycarbonate based on bisphenol A on 20 parts, by weight, of a copolymer consisting of 95 parts, by weight, methyl methacrylate and 5 parts, by weight, isopropenylphenol;

c. mixture of

1. 30 parts, by weight, of a graft polymer prepared by grafting 35 parts, by weight styrene and 15 parts, by weight, acrylonitrile on 50 parts, by weight, of a coarse textured polybutadiene, (according to the particulars given in German Auslegeschriften Nos. 1,247,665 and 1,269,360), in which the average particle diameter of the polybutadiene graft stock which is in the latex form is from 0.3 to 0.4.mu., and

2. 70 parts, by weight, of a copolymer of 70 parts, by weight, styrene and 30 parts, by weight acrylonitrile, which copolymer has an intrinsic viscosity of [.eta.] = 79.8, (determined in dimethylformamide at 20.degree. C);

d. mixture of

1. 18.75 parts, by weight, of graft polymer prepared by grafting 16 parts, by weight, styrene and 4 parts, by weight, acrylonitrile on 80 parts, by weight, of a finely divided polybutadiene in the latex form with an average particle diameter of from 0.05 to 0.1.mu., and

2. 81.25 parts, by weight, of a styrene/acrylonitrile copolymer, having a styrene/acrylonitrile ratio of 72:28 and an intrinsic viscosity of [.eta.] = 79.4 (determined in dimethylformamide at 20.degree. C);

e. mixture of

71 parts, by weight, of a copolymer of 80 parts, by weight, styrene and 20 parts, by weight, acrylonitrile, and 29 parts, by weight, of a copolymer of 60 parts, by weight, butadiene, 36 parts, by weight, acrylonitrile, 3 parts, by weight, methacrylic acid and 1 part, by weight, divinylbenzene;

f. mixture of

1. 40 parts, by weight, of a graft polymer prepared in emulsion by grafting 35 parts, by weight, styrene and 15 parts, by weight, acrylonitrile on 50 parts, by weight, of a copolymer of 96 parts, by weight, butyl acrylate and 4 parts, by weight, methacrylamide-N-methlolmethylether, and

2. 60 parts, by weight, of a copolymer of 70 parts, by weight, styrene and 30 parts, by weight, acrylonitrile, which copolymer has an intrinsic viscosity of [.eta.] = 80.1, (determined in dimethylformamide at 20.degree. C);

g. mixture of

1. 30 parts, by weight, of a graft polymer prepared in emulsion by grafting 40 parts, by weight, styrene and 20 parts, by weight, acrylonitrile on 40 parts, by weight, of a copolymer of 80 parts, by weight, butyl acrylate and 20 parts, by weight, of butadiene, and

2. 70 parts, by weight, of a styrene/acrylonitrile copolymer which has a styrene/acrylonitrile ratio of 70:30 and an intrinsic viscosity of [.eta.] = 79.0, (determined in dimethylformamide at 20.degree. C). Components (a) and (b) are homogenised with components (c) to (f) in a double shaft extruder at temperatures of from 240.degree. to 270.degree. C.

The composition and some of the mechanical properties are summarised in Table 1.