GB1600676A - Mixtures of rubber with graft copolymers - Google Patents

Description

(54) MIXTURES OF RUBBER WITH GRAFT COPOLYMERS (71) We, BAYER AKTIENGESELLSCHAFT, a body corporate organised under the Laws of Germany of 509 Leverkusen, Germany do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to rubber mixtures and more particularly relates to rubber mixtures wherein a graft polymer (B) is added to a rubber (A) in quantities of from 1 to 8t * by weight the monomers of (B) which are used for grafting being identical or compatible with the monomers of the rubber (A) used for mixing.

Mixtures of rubber with other rubbers or thermoplasts are known in many conceivable variations and are described in the relevant literature. See for example Rubber Chem.

Techn. 47 (3) 481-50. 1974 and Rubber Chem. Techn. 49 (1), 93-104 (1976).

Such mixtures are generally used to achieve a balanced ratio between processing properties, service properties and costs. As far as the service properties are concerned, this means for example that, in many cases, a specific type of rubber is regarded as unsuitable for a certain application, whereas another property of the same rubber is highly desirable.

Thus certain rubbers are blended with one another in order to additionally obtain desirable properties and to reduce undesirable properties.

Because of the well known serious incompatibility of polymers with one another, there are numerous limitations in the production of polymer mixtures, see for example, Kolloid-Zeitschrift u. Zeitschrift f. Polymere, Vol. 213, 1966, Lothar Bohn and J.

Macromol. Sci.-Revs. Macromol. Chem., C7 (2), 251-314 (1972).

As a result of incompatibilities, deteriorations generally occur in the technological properties of rubber-rubber mixtures (for example reduction of the tensile strength of mixtures of polybutadiene with polychloroprene or nitrile rubber) or rubber-thermoplast mixtures (for example reduction in the elongation at break of mixtures of polyethylene and natural rubber or polystyrene and polybutadiene). Considerable reductions in tensile strength and tear propagation resistance are also observed for example in the case of mixtures of thermoplastic styrene-butadiene three-block polymers with polybutadiene or polyethylene.

Generally, it may be said that, in the case of compatible polymers, the properties of the mixtures vary substantially linearly with their composition. This applies only, however, to compatible mixtures. Incompatible polymers can only be mixed with one another when important properties of the polymer to be modified are not too seriously affected.

It has now been found that rubber (A), preferably a diene or olefin rubber or their copolymers, can be mixed with other polymers when certain graft polymers (B) are used for mixing in quantities of from 1 to 80% by weight, the base of the graft polymer (B) being grafted with monomers which are identical or compatible with the monomers of the rubber (A) and which conveniently may be crosslinked together with the rubber (A) in the mixture. It is also possible to use different monomers for grafting. In this way, there is obtained a new type of rubber in which a regular, locally fixed distribution of graft polymer particles is present.

Accordingly, the present invention provides a rubber mixture comprising a rubber (A) in an amount of from 99 to 20% by weight and a graft copolymer (B) in an amount of from 1 to 80% by weight, said graft copolymer (B) having a particle size of from 0.1 to 2 urn and having been produced by polymerization of grafting base and grafting monomer in the presence of a radical initiator; said rubber (A) being selected from natural rubber, polybutadiene, polyisoprene, polychloroprene, butadiene-styrene copolymer, isoprenestyrene copolymer, butadiene-acrylonitrile copolymer, butadiene-isobutylene copolymer, isoprene-isobutylene copolymer, ethylene-propylene copolymer, polyisobutylene, ethylene-vinylacetate copolymer and acrylate rubbers; the graft base of said graft copolymer (B) being at least one member selected from polybutadiene, polyisoprene, polychloroprene, natural rubber, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, styrene-isoprene copolymer, polystyrene, styrene-acrylonitrile copolymer, ethylene-propylene copolymer, ethylene-propylene diene terpolymer, polyisobutylene, isobutylene-isoprene copolymer, polymethylacrylate, polyethylacrylate, polypropylacrylate, polybutylacrylate, polymethyl methacrylate, ethylene-vinylacetate copolymer, polycarbonate, polyethylene, polypropylene, polyvinylchloride and cellulose esters; and the grafting monomer of the graft copolymer (B) being identical to or compatible with the monomer of rubber (A) and being at least one monomer selected from butadiene, isoprene, chloroprene, isobutylene, butadiene/styrene, butadiene/acrylonitrile, isoprene/styrene, isoprene/isobutylene, methylacrylate, ethylacrylate, propylacrylate, butylacrylate, isoprene/butadiene, chloroprene/isoprene and isoprene/acrylonitrile.

The graft copolymer (B) is preferably produced from latex basis having a particle size of from 0.1 to 1.0 llm. The proportion of graft copolymer is preferably from 1 to 30%. The polymer chains on the graft monomer preferably have a molecular weight of from 2000 to 150,000, more preferably from 5000 to 150,000.

The graft copolymer (B) may be produced by grafting in benzene, toluene, xylene or mixtures thereof by means of radical initiators. Alternatively, it may be produced by grafting in one or more aliphatic solvents, such as hexane, pentane, cyclohexane or mixtures thereof, by means of radical initiators. It may also be produced by grafting in mixtures of aliphatic and aromatic solvents by means of radical initiators.

In contrast to all hitherto known rubber mixtures, it is possible with a rubber mixture of the present invention to establish a morphology of a multiphase rubber system which is largely independent of the mixing conditions (mixing rolls, internal mixer, solution).

Rubbers (A) suitable for mixing are, diene rubbers, such as natural rubber, polybutadiene, polyisoprene, polychloroprene, butadiene-styrene copolymers, isoprene-styrene copolymers, butadiene-acrylonitrile copolymers, butadiene-isobutylene copolymers, isoprene-isobutylene copolymers, and also rubbers such as ethylene-propylene copolymers, polyisobutylene, ethylene-vinylacetate copolymers or acrylate rubbers. It is preferred to use polybutadienes, polyisoprenes, butadiene-styrene copolymers butadiene-acrylonitrile copolymers, isoprene-isobutylene copolymers, ethylene-propylene copolymers and polychloroprenes.

Suitable graft bases for the graft polymer (B) are diene rubbers, such as polybutadiene, polyisoprene, polychloroprene or their copolymers, natural rubber, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, styrene-isoprene copolymers, polystyrene, styrene-acrylonitrile copolymers, ethylene-propylene copolymers, ethylenepropylenediene termonomers, polyisobutylene, isobutylene-isoprene copolymers, polyacrylates such as methyl, ethyl, propyl, butyl polyacrylates or polymethyl methacrylate, ethylene-vinylacetate copolymers, polycarbonates, polyethylene, polypropylene, polyvinyl chloride, and cellulose esters. Mixtures of these polymers may also be used as the graft base.

Suitable graft monomers for producing the graft monomers for producing the graft polymer (B) are butadiene isoprene, chloroprene, butadiene/styrene, butadiene/acrylonitrile, isoprene/styrene, isoprene/isobutylene, methyl, ethyl, propyl, butylacrylate, isoprenel butadiene, chloroprene/isoprene and isoprene/acrylonitrile. It is even possible to graft three or more monomers in the mixture to obtain better compatibility.

For the purposes of illustration, the following mixtures are mentioned by way of example: For mixing with polychloroprene as rubber (A), the following polymers may be grafted with chloroprene: polychloroprene, polybutadiene, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, styrene-isoprene copolymers, polystyrene, styreneacrylonitrile copolymers, and ethylene-propylene copolymers; the following polymers are preferably grafted with butadiene and/or isoprene for mixing with polybutadiene, as rubber (A): polystyrene, acrylonitrilebutadiene copolymers, polychloroprene, styreneacrylonitrile copolymers, and ethylene-propylene copolymers; the following polymers are preferably grafted with isoprene or butadiene and acrylonitrile for mixing with butadieneacrylonitrile copolymers as rubber (A): polybutadiene, polyisoprene or polystyrene or their copolymers, and ethylene-propylene copolymers; the following polymers are preferably grafted with isobutylene for mixing with polyisobutylene as rubber (A): polystyrene, styrene-acrylonitrile copolymers, and polychloroprene; the following polymers are prefer ably grafted with isoprene and/or butadiene and/or isobutylene or chloroprene with isoprene and/or butadiene and/or butadiene and/or isobutylene for mixing with ethylenepropylene copolymers as rubber (A): polystyrene, polybutadiene, polyethylene, polycarbonate and butadiene-acrylonitrile copolymers, and also styrene-acrylonitrile copolymers.

Different rubbers (A) may also be made miscible with one another by mixing in one or more graft copolymers. Naturally the examples given above only show some of the numerous possibilities of producing compatible mixtures.

The graft copolymers (B) which may consist of one or more different graft copolymers are added to the rubber (A) in quantities of from 1 to 80% by weight and preferably in quantities of from 5 to 30% by weight. The graft monomer of the graft polymer (B) may be used in a quantity of from 10 to 80% by weight, preferably in a quantity of from 30 to 60% by weight, based on the graft base.

The molecular weight of the chain of the graft branches may be of the order of from 5000 to 1,000,000 and preferably from 20,000 to 150,000 (as measured by the light scattering method).

The graft monomer may be crosslinked, but a low degree of crosslinking is preferred. The graft base may be crosslinked or uncrosslinked, although it is preferably crosslinked.

The graft polymer (B) has a particle size of from 0.1 to 2Fm, preferably of from 0.1 to 0.8 lam.

The graft polymers (B) may be produced by radical solution, or by bulk, suspension or emulsion polymerisation, irrespective of the initiator used, at temperatures of from -20%C to 1200C. It is preferred to adopt a process in which the graft polymer is obtained in a form in which it can be favourably mixed with the rubber (A). For example, in cases where a rubber (A) produced by solution polymerisation, such as for example cis-1,4-polybutadiene or an ethylene-propylene copolymer, is to be mixed with a graft polymer (B), the graft polymer (B) used will be a graft polymer which has been produced in a solution which is identical or miscible with the solvent used in the production of the rubber (A).

If for example a rubber (A) produced by emulsion polymerisation, such as an emulsion styrene-butadiene copolymer or polychloroprene or a butadiene-acrylonitrile copolymer, is to be mixed with a graft polymer (B), it is preferable to use an emulsion process for producing the graft polymer (B). Bases having an average particle size of from 0.05 to 1 Il, preferably from 0.1 to 0.4 Il, are used for the production of graft latices.

If it is desired to produce graft polymers (B) having a base which normally contains no double bonds, hydrogen atoms or heterogenous groups which are suitable for grafting, bases are synthesised by copolymerisation with certain comonomers suitable for graft polymerisation (for example styrene is copolymerised with isoprene or butadiene in quantities of from 5 to 20%).

A number of desirable technological properties can be obtained by suitable mixtures of rubber (A) and graft polymer (B). For example, the strength, moduli and processibility of polychloroprene rubbers can be improved accordingly by chloroprene-grafted polystyrene or styrene/acrylonitrile copolymer. By mixing chloroprene-grafted polybutadiene with polychloroprene, its low-temperature flexibility is increased. By mixing chloroprenegrafted butadiene/acrylonitrile copolymer with polychloroprene, its resistance to oil is improved. By mixing butadiene- or isoprene-grafted polystyrene with polybutadiene or ethylene-propylene rubbers, their strength and processibility are improved. By mixing isoprene- or butadiene/acrylonitrile-grafted butadiene or isoprene, the low-temperature flexibility of butadiene/acrylonitrile copolymers is increased; These examples may be continued ad infinitum and the above are by way of illustration only. The important factor in every case is that, by virtue of the grafting-induced compatibility of the graft copolymers with the rubbers, it is possible to obtain a controlled modification of certain technological properties without the characteristic properties of the base rubber (A) being undesirably infuenced to any significant extent.

The rubber (A) may be mixed with the graft polymer (B) in different ways: For example, it is possible to mix the corresponding latices at room temperature or at elevated temperature and then to coagulate the resulting mixtures by adding salts, acids or alcohols, or to precipitate the rubber mixture by low-temperature coagulation. It is also possible to mix the dissolved polymers (A) and (B) and to work up the solution by stripping, spray drying or precipitation, for example with alcohol. For the sake of completeness, reference is also made to the possibility of mixing latex with solution. Mixing may also be carried out mechanically on mixing rolls, in internal mixers or in screw extruders at temperatures in the range from 20 to 1200C.

Fillers, extenders and vulcanisation aids may also be incorporated during the mixing operations.

The mixtures of rubber (A) and graft polymer (B) may be vulcanised in the usual way in the presence of sulphur or peroxides.

The process according to the invention is illustrated by the following Examples: A. Production of graft polymers B. Production of graft polymer/rubber mixtures.

Ad A: The graft polymers used for mixing with rubber are produced in emulsion, suspension or solution by means of radical initiators.

Example A 1 1600 g of polybutadiene latex (solids content 54.4%, average particle size 0.4 la) and 1640 ml of desalted water are introduced into a 6 litre flask. The flask is then purged with nitrogen and its contents heated to 63-650C. After heating, a solution of 4.5 g of potassium persulphate in 200 ml of water is added.

At 63 to 650C, 540 g of chloroprene and a mixture of 375 g of water and 12 g of an emulsifier of the alkyl sulphonate tyPe are separately and simultaneously added dropwise over a period of 4 hours, followed by stirring for 4 to 6 hours at 63-650C.

After degassing, the latex is filtered and directly used for mixing tests with rubber latices or solutions.

Example A 2 1600 g of butadiene-acrylonitrile copolymer latex (38% of acrylonitrile, Defo hardness 1000, solids concentration 49.5%, particle size 0.2 la and 1640 ml of desalted.water are introduced into a 6 litre flask.

The flask is then purged with nitrogen and its contents heated to 63-65"C. After heating, a solution of 4.5 g of potassium persulphate in 200 m of desalted water is added.

At 63 to 650C, 540 g of chloroprene and a mixture of 375 g of water and 12 g of an emulsifier of the alkyl sulphonate type are simultaneously and separately added dropwise over a period of 4 hours, followed by stirring for 4to 6 hqurs at 63 to 65 Cj"After degassing, the latex is filtered.

Example A 3 2260 g of polychloroprene latex (solids concentration 35.2%, average particle size 0.2 ,u) and 1000 ml of desalted water are introduced into a 6 litre flask.

The flask is then purged with nitrogen and its contents heated to 63-650C. After heating, a solution of 4.5 g of potassium persulphate in 200 ml of water is added.

At 63 to 650C, 540 g of chloroprene and a mixture of 375 g of water and 12 g of an emulsifier of the alkyl sulphonate type are simultaneously and separately added dropwise over a period of 4 hours, followed by stirring for 4 to 6 hours, at 63 to 650C. After degassing, the latex is filtered.

Example A 4 1600 g of polybutadiene latex (solids content 54.4%, average particle size 0.4 ,u) and 1640 ml of desalted water are introduced into a 6 litre flask.

The flask is then purged with nitrogen and its contents heated to 63-650C. After heating, a solution of 4.5 g of potassium persulphate in 200 ml of water is added.

At 63-65"C, a mixture of 378 g of isoprene and 162 g of acrylonitrile together with 375 ml of water and 12 g of an emulsifier of the alkyl sulphonate type are simultaneously and separately added dropwise over a period of 4 hours, followed by stirring for 4 to 6 hours at 63-65"C. After degassing, the latex is filtered.

Example A 5 1600 g of a butadiene-acrylonitrile copolymer latex (33% of acrylonitrile, Defo hardness 1000, solids concentration 49.3%, average particle size 0.19 la) and 1640 ml of desalted water are introduced into a 6 litre flask.

The flask is then purged with nitrogen and its contents heated to 63-65"C. At 63-65"C, a mixture of 475 g of styrene and 65 g of acrylonitrile together with 375 ml of water and 12 g of an emulsifier of the alkyl sulphonate type are simultaneously and separately added dropwise over a period of 4 hours, followed by stirring for 4 to 6 hours at 63-65"C. After degassing, the latex is filtered.

Example A 6 1970 g of styrene-isoprene copolymer latex (10% of isoprene, solids content 40.8%, average particles size 0.15 la) and 1260 g of desalted water are initially introduced into a 6 litre flask.

The flask is then purged with nitrogen and its contents heated to 63-650C. At 63-65"C, 540 g of chloroprene and a mixture of 375 g of water and 12 g of an emulsifier of the alkyl sulphonate type are simultaneously and separately added dropwise over a period of 4 hours, followed by stirring for 4 to 6 hours at 63-650C. After degassing, the latex is filtered.

Example A 7 250 g of cis-1,4-polybutadiene ( = 240 mUg) is added to 4 litres of toluene, followed by stirring until a solution is formed. 200 g of chloroprene, 200 g of isoprene and 12 g of benzoyl peroxide are then added, followed by stirring for 18 hours at 60"C.

Example A 8 5.2 litres of n-hexane and 320 g of ethylene-propylene terpolymer (EN-type, Mooney ML 4-100 90, 12 C=C-double bonds per 1000 carbon atoms) are introduced into a 10 litre autoclave followed by stirring until the rubber has completely dissolved. 480 g of chloroprene and a solution of 15.2 g of dibenzoyl peroxide in 100 ml of benzene are then added, followed by stirring for 18 hours at 60"C.

Ad B: The rubber and graft polymer are mixed with each other in latex form, in solution or in solid form on mixing rolls or in an internal mixer. The latex mixtures and the solution are worked up in known manner by precipitation and stripping, respectively. Standard carbon black mixtures are initially produced from the graft polymer mixtures in accordance with ISO Specification 2475-1975 (E), after which mouldings are produced from the resulting mixtures and then pressvulcanised for 20, 40 and 60 minutes at a temperature of 1500C. The necessary test specimens are cut from the sheets obtained. Strength (F), elongation (D) and strain values (S; at 100/300% elongation) are tested on the Standard Test Ring I according to DIN 53 504, whilst Shore hardness A (H; at 20 and 70"C) is tested in accordance with DIN 53305 and resilience (E) in accordance with DIN 53512. The compression set is measured in accordance with DIN 53517. The crude graft polymer mixtures employed are used for measuring the polymer viscosity and the difference in viscosity between the one minute and the four minute value in a Mooney Tester at 1000C (M1-4) in accordance with DIN 53523 and Defo plasticity in accordance with former DIN 53514. The gel content is determined by centrifuging a toluene solution.

A selection of prepared and tested graft polymer mixtures (I-XX) is given and fully characterised in Tables la and lb. The test data of the vulcanisates are shown in Table II.

Example B 1 (Table la) Polymer mixtures of 90 (I) and 80 (II) parts by weight of a chloroprene homopolymer with 10 and 20 parts by weight, respectively, of a chloroprene-grafted polystyrene have a distinctly higher gel content and viscosity trend value, reflected in better processing properties, in comparison with the pure chloroprene homopolymer (V).

The products also show high strength, strength and hardness values in the vulcanisates.

Example B 2 (Table la) Polymer mixtures of 90 (III) and 80 (IV) parts by weight of a chloroprene homopolymer with 10 and 20 parts by weight, respectively, of a chloroprene-grafted butadieneacrylonitrile copolymer containing 38% of acrylonitrile also show a higher gel content and viscosity trend value and, hence, better processing properties by comparison with the pure chloroprene homopolymer (V). In the extrusion of strings, output is higher and the level of extrusion swelling lower.

After ageing in hot air (21 days/100 C), the increase in the hardness and strain values of the vulcanisates containing the polymers according to the invention is lower, i.e. they are more resistant to ageing. In addition, the vulcanisates containing the polymers according to the invention are much more resistant to ASTM oils, as shown by storage tests at 1000C.

Example B 3 (Table la) Polymer mixtures of 85 (VI) and 70 (VII) parts by weight of a chloroprene homopolymer with 15 and 30 parts by weight respectively, of a chloroprene-grafted polybutadiene also show a much higher gel content and a viscosity trend value and, hence, extremely good processing properties in comparison with the pure homopolymer (V).

The vulcanisates of the polymer mixtures show higher hardness, strain and elasticity values in comparison with the reference material.

Example B 4 (Table la) Polymer mixtures of 90 (VIII) and 80 (IX) parts by weight of a chloroprene homopolymer with 10 and 20 parts by weight, respectively, of a chloroprene-grafted styrene-isoprene copolymer show higher gel contents and viscosity trend values and, hence, better processing properties in comparison with the pure chloroprene homopolymer (V).

Example B 5 (Table la) In comparison with the ungrafted reference material (V), a polymer mixture of 80 parts by weight of a chloroprene homopolymer with 20 parts by weight of a chloroprene-grafted polychloroprene (X) also shows higher gel contents and viscosity trend values and, hence, better processing properties. Higher strain, hardness and elasticity values are obtained in the vulcanisate.

Example B 6 (Table la) In comparison with the ungrafted reference material (XIII), polymer mixtures of 90 (XI) and 80 (XII) parts by weight of a sulphur-modified polychloroprene with 10 and 20 parts by weight, respectively, of a chloroprene-grafted polybutadiene similarly to the products of the preceding Examples - show higher gel contents and viscosity trend values which enable rolled sheets to be rapidly formed. In the carbon black mixtures, the products are less inclined to become tacky on the rolls and promote more rapid vulcanisation which.leads to a higher crosslinking density with higher strain, hardness, elasticity and compression set values.

Example B 7 (Table la) The polymer mixture of 80 parts by weight of a chloroprene homopolymer with 20 parts by weight of a chloroprene-grafted butadiene-acrylonitrile copolymer containing 38% of acrylonitrile (IV b) shows a Mooney viscosity ML-4/100 C of 58 ME and a gel content of 16%.

In this respect, it is comparable with a so-called pre-crosslinked polychloroprene (IV a) which is obtained by mixing benzene-soluble homopolymers or copolymers of chloroprene with benzene-insoluble copolymers of chloroprene generally produced bv known methods, e.g. British Patent No. 1,158,970, using diesters, and which is used in particular to applications requiring good processing properties. However, for equivalent processing properties of IV b and IV a, the polymer mixture according to the invention produces higher strength values, better compression set and better ageing behaviour.

Example B 8 (Table lb) A polymer mixture of 90 (XIV) and 80 (XV) parts by weight of a chloroprene homopolymer with 10 and 20 parts by weight, respectively, of a chloroprene-grafted cis-1,4-polybutadiene has Mooney viscosities ML-4/100 C of 58 and 68, and gel contents of 8 and 20% respectively.

In the vulcanisates, the mixture shows excellent strengths and elongations, good low-temperature flexibility and a low compression set.

Example B 9 (Table lb) In comparison with the pure homopolymer (V), a polymer mixture of 80 parts by weight of a chloroprene homopolymer with 20 parts by weight of a chloroprene-grafted ethylene-propylene terpolymer (XVI) shows a higher gel content and viscosity trend value and, hence, extremely good processing properties. An increased resistance to ageing is obtained in the vulcanisates.

Example B 10 (Table lb) A polymer mixture of 85 (XVII) and 70 (XVIII) parts by weight of a nitrile rubber with 15 and 30 parts by weight, respectively, of an isoprene/acrylonitrile-grafted polybutadiene shows good strength and elongation values, increased low-temperature flexibility and reduced compression set.

Example B 11 (Table lb) A polymer mixture of 90 (XIX) and 80 (XX) parts by weight of a lithium polybutadiene with 10 and 20 parts by weight, respectively, of an isoprene-grafted polystyrene shows good strength and elongation values and a very considerable improvement in processibility over the pure polybutadiene.

TABLE 1a Mixtures I II II IV V VI VII Chloroprene homopolymer 90 80 90 80 100 85 70 Chloroprene-grafted polystyrene according to A 6 10 20 Chloroprene-grafted butadiene-acrylonitrile copolymer according to A 2 10 20 Chloroprene-grafted polybutadiene according to A 1 15 30 Raw material properties Gel content (%) 10.0 20.0 9.0 18.3 0.6 16.5 32.1 Mooney viscosity ML-4 (100 C) (ME) 61/10 70/13 58/10 62/10 71/2 69/8 82/14 Mixtures VII IX X XI XII XIII Chloroprene homopolymer 90 80 80 Chloroprene-grafted polybutadiene according to A1 10 20 Chloroprene-grafted polystyrene according to A 6 10 20 Chloroprene-grafted polychloroprene according to A 3 20 Sulphur-modified homopolychloroprene 90 80 100 Raw material properties Gel content (%) 9.7 19.3 21.8 10.7 21.3 0.4 Mooney viscosity ML-4 (100 C) (ME) 60/10 62/12 69.6 38/8 40/6 40/6 Defo plasticity 675 900 900 Mixtures IVa IVb Chloroprene homopolymer 80 Precrosslinked polychloroprene 100 Chloroprene-grafted butadiene-acrylonitrile copolymer according to A 2 20 Raw material properties Gel content (%) 15.9 16 Mooney viscosity ML-4 (100 C) (ME) 54 58 TABLE 1b Mixtures XIV XV XVI XVII XVIII XIX XX Chloroprene homopolymer 90 80 80 Chloroprene-grafted cis-1,4-polybutadiene according to A 7 10 20 Chloroprene-grafted ethylene-propylene terpolymer according to A 8 20 Isoprene/acrylonitrile-grafted polybutadiene according to A 4 15 30 Acrylonitrile-butadiene copolymer (38% of ACN, Defo hardness 1800) 85 70 Isoprene-grafted polystyrene (10% of isoprene in polystyrene MW 100,000) 10 20 Polybutadiene (Li-Br) (# 200 ML/G) 90 80 Raw material properties Mooney viscosity ML-4 (100 C) (ME) 58 68 120 108 115 50 60 Gel content (%) 8 20 25 20 35 9 18 TABLE 2: Vulcanisate properties Mixture S (MPa) E (%) M (100%) H Shore A El (%) Structure C.S. 70 /22" Brittlene (MPa) 20/70 C (N) 100 /170" point C I 18.2 340 3.2 69/65 50 146 23/31 II 17.6 300 4.4 76/68 43 164 34/35 III 17.5 370 2.3 64/62 51 134 11/32 -34 IV 17.0 370 2.4 65/62 59 116 12/31 -34 V 17.8 440 2.2 62/61 49 168 /27 -30 VI 15.0 330 2.5 65/64 56 104 11/29 VII 13.0 270 3.1 68/67 56 90 11/26 VIII 17.5 400 3.2 70/68 45 160 /27 -30 IX 17.3 310 4.3 76/67 42 140 - /28 -30 X 17.5 400 2.4 64/62 50 - /27 XI 17.2 540 2.0 64/63 48 18/ XII 15.0 460 2.3 66/63

Claims (17)

WHAT WE CLAIM IS:

1. A rubber mixture comprising a rubber (A) in an amount of from 99 to 20% by weight and a graft copolymer (B) in an amount of from 1 to 80% by weight, said graft copolymer (B) having a particle size of from 0.2 to 2 lam and having been produced by polymerization of grafting base and grafting monomer in the presence of a radical initiator; said rubber (A) being selected from natural rubber, polybutadiene, polyisoprene, polychloroprene, butadiene-styrene copolymer, isoprene-styrene copolymer, butadiene-acrylonitrile copolymer, butadiene-isobutylene copolymer, isoprene-isobutylene copolymer, ethylenepropylene copolymer, polyisobutylene, ethylene-vinylacetate copolymer and acrylate rubbers; the graft base of said graft copolymer (B) being at least one member selected from polybutadiene, polyisoprene, polychloroprene, natural rubber, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, styrene-isoprene copolymer, polystyrene, styreneacrylonitrile copolymer, ethylene-propylene copolymer, ethylene-propylene diene terpolymer, polyisobutylene, isobutylene-isoprene copolymer, polymethylacrylate, polyethylacrylate, polypropylacrylate, polybutylacrylate, polymethyl methacrylate, ethylenevinylacetate copolymer, polycarbonate, polyethylene, polypropylene, polyvinylchloride and cellulose esters; and the grafting monomer of the graft copolymer (B) being identical to or compatible with the monomer of rubber (A) and being at least one monomer selected from butadiene, isoprene, chloroprene, isobutylene, butadiene/styrene, butadiene/acrylonitrile, isoprene/styrene, isoprene/isobutylene, methylacrylate, ethylacrylate, propylacrylate, butylacrylate, isoprene/butadiene, chloroprene/isoprene and isoprene/acrylonitrile.

2. A rubber mixture as claimed in Claim 1, comprising 95 to 70% by weight of rubber (A) and 5 to 30% by weight of graft copolymer (B).

3. A rubber mixture as claimed in Claim 1 or 2, wherein the graft monomer of graft copolymer (B) is present in an amount of 10 to 80% by weight based on the graft base.

4. A rubber mixture as claimed in Claim 3, wherein the graft monomer of graft copolymer (B) is present in an amount of 30 to 60% by weight based on the graft base.

5. A rubber mixture as claimed in any of Claims 1 to 4, wherein the rubber (A) is selected from natural rubber, polybutadiene, polyisoprene, butadiene-styrene copolymer, butadiene-acrylonitrile copolymer, isoprene-isobutylene copolymer, ethylene-propylene copolymer and polychloroprene.

6. A rubber mixture as claimed in any of claims 1 to 5, wherein the rubber (A) is a butadiene-acrylonitrile copolymer.

7. A rubber mixture as claimed in any preceding claim, wherein the graft copolymer (B) is produced from latex bases having a particle size of from 0.1 to 1.0 la.

8. A rubber mixture as claimed in any preceding claim, wherein the proportion of graft copolymer is from 1 to 30%.

9. A rubber mixture as claimed in any preceding claim, wherein the graft base is crosslinked.

10. A rubber mixture as claimed in any preceding claim, wherein the polymer chains of the graft monomer have a molecular weight of from 2000 to 150,000.

11. A rubber mixture as claimed in Claim 10, wherein the polymer chains of the graft monomer have a molecular weight of from 5,000 to 150,000.

12. A rubber mixture as claimed in any of Claims 1 to 8, wherein the graft copolymer (B) is uncrosslinked.

13. A rubber mixture as claimed in any preceding claim, wherein the graft copolymer (B) is produced by grafting in benzene, toluene, xylene or mixtures thereof by means of radical initiators.

14. A rubber mixture as claimed in any of Claims 1 to 12, wherein the graft copolymer (B) is produced by grafting in one or more aliphatic solvents by means of radical initiators.

15. A rubber mixture as claimed in Claim 14, wherein the aliphatic solvent is hexane, pentane, cyclohexane, or mixtures thereof.

16. A rubber mixture as claimed in any of Claims 1 to 12, wherein the graft copolymer (B) is produced by grafting in mixtures of aliphatic and aromatic solvents by means of radical initiators.

17. A rubber mixture as claimed in Claim 1, substantially as herein described with particular reference to the Examples.