NO126663B - - Google Patents

Description

Vulcanized elastomers obtained from essentially amorphous polymers and from copolymers of α-olefins as well as methods for producing such elastomers.

The present invention relates to elastomers obtained from polyolefins, in particular from

copolymers of α-olefins and ethylene,

as well as method for the production of

such elastomers.

In previous patents belonging to the patent holder, it has been shown that vulcanized

rubber species can be produced from polymers obtained essentially from

olefins with the general formula CH2 =

CHR (in which R denotes an alkyl group) as well as from copolymers thereof

olefins with each other and with ethylene.

These patents are particularly described

methods for the production of rubber species from said products after chlorosulfonation thereof. In this way can

where functional groups are introduced into the polymer chains and these groups remain

the subsequent vulcanization is able to

form cross-linked bonds with basic

substances such as metal oxides or diamines.

In the relevant previous patents, transfer of polymers that have

characteristics of amorphous, viscous materials

to vulcanized elastomers, takes place essentially in two consecutive operations, namely chlorosulfonation and vulcanization. To perform the former operation

in such a way that end products are included

good technological characteristics at reasonable costs is not very easy. This operation must in general

is carried out with polymers that are dissolved

in solvents consisting of halogenated, organic compounds in relatively low concentrations (a few percent). This method entails various problems, in particular the problems of obtaining chlorosulfonated polymers that are free of solvents and of recovering the significant quantities of solvents that have been used. Furthermore, the chlorosulphonation conditions, in particular the temperature, must be carefully controlled, as otherwise a strong degradation of the polymers can occur and this degradation results in the mechanical and elastic properties of the final product, i.e. the elastomer, deteriorating. The use of metal oxides, especially lead oxide, for vulcanization of the chlorosulfonated product, on the other hand, causes an increase in the elastic hysteresis and consequently a deterioration of the elastomers' most important properties.

Chlorosulfonation is a chemical reaction that requires the use of aggressive and corrosive chemicals such as chlorine, sulfur dioxide, sulfuryl chloride, as well as the use of special equipment. This treatment cannot easily be carried out by normal consumers of raw rubber for the manufacture of final products. Consequently, manufacturers of saturated copolymers could not sell such products as they are to their customers, but had to carry out the chemical treatment themselves to transfer the copolymers to products that can be vulcanized directly.

In other patents belonging to the patent holder, the possibility of producing elastomers from slightly unsaturated copolymers obtained by copolymerizing olefins with the general formula CH2 = CHR and ethylene with small amounts of dienes or acetylene monomers is shown. Such copolymers can be vulcanized with sulfur or with compounds that release sulfur using mixtures containing vulcanization accelerators of the fast-acting or very fast-acting type. The mechanical and elastic properties of the elastomers thus obtained after vulcanization are good when the copolymer used as starting material has a sufficiently regular distribution of the double bonds in each individual macromolecule and all macromolecules contain approximately the same number of double bonds. The more irregular the distribution of the unsaturated bonds, the worse the properties of the elastomers obtained. Elastomers obtained from such copolymers therefore in some cases have poor elastic properties, e.g. values for permanent fixation ("permanent set") in the event of a breach of 100% and higher.

It has now been found that substantially amorphous, linear, saturated polymers of aliphatic olefins of the general formula CH2 = CHR and substantially amorphous copolymers of the same olefins with each other and with ethylene obtained by methods according to one or more of the patent holder's previous patents , namely by low-pressure processes based on the use of catalysts containing bonds between metals and organic compounds and which contain a large number of tertiary carbon atoms, can be vulcanized directly into products with valuable elastomeric properties by grafting onto the polymer chain organic compounds containing functional acidic groups.

More precisely stated, it has been found that with linear α-olefin polymers or copolymers of the aforementioned types it is possible to form cross-linked bonds between the different polymer chains, i.e. to achieve vulcanization by a reaction of the radical type. In particular, vulcanization of polymers containing monomeric units derived from α-olefins can be achieved by using organic compounds whose molecules contain double bonds and functional acidic groups and which are capable of reacting with said polymers or copolymers in the presence of radical-type initiators.

It has further been found that it is advantageous for the compounds to be grafted onto the polymer chains to contain a double bond which is conjugated in relation to the double bonds in one or more of the groups.

In order to obtain a substantial number of grafting sites using relatively small amounts of the compound to be grafted, it is advantageous to use a compound such as maleic acid or maleic anhydride which shows a moderate tendency to polymerize and to give polymers with very high molecular weight and which also easily undergo chain transfer processes.

It is known that maleic anhydride and other compounds of the aforementioned type can be used to vulcanize polymers with a high degree of unsaturation (containing at least 50% copolymerized diene). This is described e.g. in the U.S. Patents Nos. 2,662,874, 2,724,707, etc. (H. P. Brown). According to these patents, maleic anhydride is used in the presence of initiators of the radical type and zinc oxide for the vulcanization of highly unsaturated rubber species. It is stated in these patents that large amounts of benzoyl peroxide and maleic anhydride are generally used.

The vulcanization process is explained by Brown on the assumption that maleic anhydride binds to the double bonds present in the polymer chains, whereby rings of 4 carbon atoms are formed which are bound to (CO)20 groups which are acidic in nature and capable of forming salts with zinc oxide , whereby cross-linked bonds are formed and the product is vulcanized. The necessity of using zinc oxide to obtain vulcanized products is thus clearly stated in the aforementioned patents.

In contrast, it is not previously known that saturated organic polymers can be vulcanized using compounds of the aforementioned type. It has now been found that organic compounds of the type mentioned above, containing double bonds, can also be grafted onto saturated polymer chains and that for such grafting it is appropriate that tertiary carbon atoms especially of the type

in which the hydrogen atom on the tertiary carbon atom is very mobile, is

present in the saturated polymer chains. IN

in this case it is not necessary for the chain to contain double bonds. However, the presence of small amounts of double bonds in the chain is not harmful, but is

not necessary.

The method according to the invention

thus allowing vulcanization not only of

saturated polymers, but also of unsaturated polymers which contain a very small number of double bonds and which

not easily vulcanized by means of

the usual methods which are based on the application of sulphur.

When applying the methods which

forms the object of the present invention, it is therefore possible to vulcanize

also copolymers which essentially

contains α-olefins and only a small number

double bonds and which are obtained by

methods according to the patent holder

previous patents, and thereby few elastomers

with good mechanical and elastic properties.

None of the reaction mechanisms that

is proposed as an explanation for the typical

processes consisting in the addition of maleic anhydride can explain the vulcanization process which is an object of the present invention. Among such reaction mechanisms is Diels-Alder addition

to conjugated double bonds, addition

to unsaturated polymers with the resulting formation of cyclic groups, as stated in the above-mentioned Brown's patents, copolymerization with substances containing double bonds such as e.g. takes place during the production of polyester resins and substitutional addition of methylene groups in the a-position in relation to the double bond. Said vulcanization process can therefore only be explained by assuming reaction mechanisms that are completely different from those mentioned above.

Since the vulcanization can take place with products that do not contain double bonds but contain tertiary carbon atoms, the process can be explained by the following reaction taking place when maleic anhydride is used as the compound to be grafted and which contains a double bond:

a) the formation of a radical on poly-

In this scheme, R" denotes a radical which

writes itself from the initiator.

b) The radical formed according to the above reaction nucleus (1) can react with one mole of maleic anhydride according to the reaction scheme:

This creates a new, free radical. 1,2-substituted ethylene compounds (eg

This new radical can react with derivatives of maleic acid or of crotonic acid, additional molecules of maleic anhydride, etc.) and that other reactions of radicals in a manner similar to that in the reaction vessel preferably take place, e.g. maet (2) indicated. Such reactions take place as follows: more easily with compounds that differ c) Radicals formed according to reactions from maleic anhydride such as vinyl or scheme (2) can together with radicals form vinylidene compounds (e.g. acrylates that are bound to other chains form or methacrylates). cross-links by a mutual de- It must be assumed that propagation of polarizing reactions of the lymerisate chain type is less likely with d) or termination of the radical chains by dismutation may take place after the following reaction kernels: or a termination of the growing radical chains by combination with a free radical: or chain transfer to atoms or radicals that write from another polymer chain:

At the same time, others may take place

reactions such as reactions between different radicals which in some cases can also

contribute to the vulcanization. By simple addition of initiators that deliver freely

radicals, e.g. by mixing benzoyl peroxide with the polymer, finds formation

of cross-links take place to a certain extent.

Table 1 below lists the most important properties of vulcanized products obtained by mixing an ethylene-propylene-sampblymerisate with 1% benzoyl peroxide and with different amounts of maleic anhydride indicated in the table.

Table 1.

Maleic acid- Final Break- Fixation at Soluble in Swelling conditions anhydride % tensile strength elongation 200% for- benzene at at equilibrium of poly- kg/cm<2> % elongation 35° C (1)

merisat % %

0 23 700 30 50 9 4 35 490 20 35 6 8 52 450 15 28 5

(1) (See P. Flory: "Principles of polymer chemistry, p. 579).

It appears from the data listed in table 1

it is clear that the presence of maleic anhydride allows to obtain a good vulcanization. This can be explained by reactions according to the above schemes (2) and (7). The elastomeric ones

which are obtained with mixtures containing zinc oxide in addition to maleic anhydride can be vulcanized even better than those obtained in the absence of zinc oxide and this can be explained by assuming that the zinc oxide forms salt bonds between the different chains as it reacts with the anhydride groups which may be bound to the chains according to reactions ( 4), (5), (6) and (7) in the above forms.

This result is only achieved with compounds that contain at least one double bond that is capable of reacting in a radical-type reaction, as well as free carbonic acid groups or anhydride groups. Table 2 below shows the mechanical properties of products made from an ethylene-propylene copolymer with a molecular weight of 165,000 and containing 47 mole percent propylene, using maleic acid, in comparison with products made using methyl maleate or succinic acid instead for maleic acid:

Vulcanization at 160° C for 30 minutes

Instead of maleic acid or maleic anhydride, you can use other unsaturated compounds containing acidic groups such as e.g. fumaric acid, acrylic acid, methacrylic acid, ethacrylic acid, vinylacrylic acid, itaconic acid, methyl-itaconic acid, aconitic acid, methyl-aconitic acid, crotonic acid, α-methyl-oretonic acid, cinnamic acid, 2,4-dihydroxycinnamic acid, citraconic anhydride.

When using certain of these compounds such as e.g. acrylic acid, which is easily polymerized, chains containing a relatively high number of monomeric units can be grafted onto the copolymer. One must therefore use a relatively large amount of monomers to achieve the same degree of vulcanization. The most important properties of elastomers obtained from ethylene-propylene copolymer with a molecular weight of around 340,000 by <1> grafting of various unsaturated compounds and vulcanization are listed in table 3 below. Per 100 parts by weight of copolymer, 2 parts by weight were used here benzoyl peroxide and 20 parts by weight zinc oxide. The unsaturated compound was added to the mixture in the proportion necessary to obtain 0.15 carboxyl equivalents per 100 g copolymer. The vulcanization was carried out at 160° C. for 30 minutes.

Initiators of the radical type which are advantageous in the present process include compounds such as benzoyl peroxide, chlorobenzoyl peroxide, cumyl peroxide, lauryl peroxide, the peroxides of methyl ethyl ketone and of cyclohexanone, t-butyl peroxide, t-butyl perbenzoate, ku -men-, tetralin-, decalin-, t-butyl hydro-peroxides, azo-bis-isobutyrnitrile. It is obvious that the vulcanization temperature and the vulcanization duration must be chosen with a view to the type of initiator used, taking into account that the different initiators deliver free radicals at different rates.

Among the connections that are in good condition

to form salt bridges between the various polymer chains, together with the acidic functional groups, are metal oxides and hydroxides, glycols, diamines, etc. Among the metal oxides that are particularly suitable are oxides and hydroxides of zinc, calcium, cadmium, magnesium, lead and so on. Table 4 below shows properties of products obtained from an ethylene-propylene copolymer with a molecular weight of around 340,000 using 2 parts benzoyl peroxide, 9 parts maleic acid and 0.25 mol metal oxide or metal hydroxide per 100 parts copolymer. The vulcanization was carried out at 160° C. for 30 minutes.

As mentioned above, vulcanization of polymers containing α-olefins can be carried out by mixing the polymer, e.g. in a roller mixer of the type generally used for the treatment of rubber species, with the various constituents of the mixture. It is advantageous to first bring the polymer into the mixer and process this until a homogeneous and flexible plate is obtained, after which the initiator and the unsaturated compound are added to the plate and the mixing is continued until a completely homogeneous mixture of the polymer and the added substances.

Finally, if necessary, the substance which is able to form salt bridges (e.g. zinc oxide) can be added, if desired also reinforcing fillers, dyes, etc. The vulcanization is then carried out in a press or autoclave at high temperatures, e.g. temperatures between 120 and 180° C, as the exact temperature will depend on the nature of the mixture's components and in particular on the type of initiator used.

The mixture of the polymer with the initiator of the radical type and the compound to be grafted can also be carried out using other methods. Thus, e.g. good homogenization is achieved by working in the presence of solvents, especially benzene, which dissolve the various components of the mixture. Thus, a solution in benzene of an ethylene-propylene copolymer can be used directly as this is obtained during the polymerization, but after removal of the products from the cleavage of the catalyst. The solution of benzoyl peroxide and maleic anhydride is then added at temperatures which are not higher than 80°C and which are preferably between 40 and 60°C.

The product thus obtained can be separated from the solvent by evaporating the latter, preferably in a vacuum. The product obtained can then be vulcanized as described.

The method according to the present invention can also be carried out in another way which is preferable from certain points of view. As the initial mixture constitutes a system with several components, when the method is carried out as described above, the possibility of grafting the unsaturated compounds onto the polymer chains can be significantly reduced by the influence of other reactions that take place during the mixing and vulcanisation, such as e.g. formation of salts between the unsaturated compounds that have functional acidic groups and the basic substance, reactions between the initiator of the radical type and the unsaturated compounds, cleavage of the polymer which leads to its breakdown, etc. Such reactions can significantly reduce the yield of grafted polymer calculated on the unsaturated compounds that are added to the mixture and can lead to the formation of compounds that act as inert fillers or diluents, whereby the mechanical and elastic properties of the end product deteriorate.

It has also been observed that the addition of carbon black, antioxidants, peptizing agents and radical inhibitors to the starting mixtures generally leads to the formation of elastomers with relatively poor mechanical and elastic properties. This is probably due to the fact that additives as mentioned tend to block the free radicals that are present in the polymer chains, whereby they counteract both the grafting of the unsaturated compounds onto the polymer chains and the formation of cross-links when connecting two free radicals. It is also known that such additives favor cleavage reactions rather than the formation of cross-links and can thus produce a breakdown of the polymer.

In order to obtain elastomers with better elastic properties and greater durability, it is therefore preferred to carry out the method in two or more separate steps, namely so that the grafting of the unsaturated compound with functional, acidic groups onto the α-olefin copolymer or polymerizate takes place first and then successively the formation of cross-links by means of polyfunctional basic substances such as oxides of polyvalent metals, glycols, diamines, etc.

In more detail, when the polymer or copolymer is first mixed with the initiator of the radical type and the unsaturated compound and the resulting mixture are heated to high temperatures, preferably in the absence of oxygen, a graft polymer will be obtained which in some cases may also contain large amounts of gel. The duration of the heat treatment and the temperature to be used are mainly dependent on the amount and type of initiator used. These conditions can be chosen so that the initiator is practically completely cleaved after the heat treatment, whereby the largest possible number of grafted functional groups is obtained. The grafting polymer is then suitably processed in a roller mixer to plasticize and homogenise it and finally the desired amount of basic substance is added. The resulting mixture is then vulcanized, whereby elastomers with very good elastic properties and aging properties are obtained.

Table 5 below compares the mechanical properties of an ethylene-propylene copolymer after the first step (treatment with benzoyl peroxide and maleic acid) and after the second step (vulcanization with zinc oxide).

In this way, good elastomers can be obtained by vulcanizing the polymers with quantities of initiators of the radical type and of unsaturated compounds with functional acidic groups which are considerably smaller than the quantities which must be used when the method is carried out in only one step.

Table 6 below lists the most important properties for a product obtained from an ethylene-propylene copolymer (with 69 mole percent propylene) by

the one-step method using 2 parts dibenzoyl peroxide, 9 parts maleic acid and 20 parts zinc oxide per 100 parts polymer, in comparison with equivalent properties of a product obtained from the same copolymer by the two-stage method using 1 part dibenzoyl peroxide, 3 parts maleic acid, 1.5 parts antioxidant (2,2-methylene-bis-4 -methyl-tert.-butylphenol) and 10 parts zinc oxide per 100 parts copolymer.

It can be seen from Table 6 that the addition of antioxidants to the graft polymer does not prevent the subsequent formation of cross-links with zinc oxide. The elastomers can therefore be effectively protected against the influence of oxygen and their resistance to degradation caused by atmospheric influences can be increased in general.

It has also been found that the addition of significant amounts (1 to 20%) of saturated organic acids such as stearic acid, oxalic acid, phthalic acid, etc. to the graft polymers prior to the addition of zinc oxide, causes an improvement in the mechanical and elastic properties of the vulcanized elastomers. Table 7 below lists the most important mechanical and elastic properties of a product obtained from an ethylene-propylene copolymer (with 60 mole percent propylene) by vulcanization according to the two-stage method using 10 parts of zinc oxide and different amounts of stearic acid (the copolymer was previously inoculated with 3 parts maleic acid in the presence of 1 part dibenzoyl peroxide).

The two-step method offers further advantages. Thus, the first heat treatment in which the grafting is achieved can be prolonged until a complete cleavage of the initiator takes place. In this way, the presence of the initiator in the finished elastomer must be avoided.

The presence of such substances is particularly harmful to the product's aging properties. Furthermore, carbon black can be added in the quantities normally used in articles for mass production (e.g. tires for vehicle wheels) without reducing the mechanical and elastic properties of the elastomers.

When working according to the two-stage method, the vulcanization is mainly achieved by the formation of ionic cross-links from carbon atom to carbon atom. This is due to linking of radicals and therefore carbon black and other reinforcing fillers can fully exert their effects without hindering the vulcanization. The addition of such fillers improves to a remarkable extent the resistance to rubbing and scouring as well as the elastic modulus and the final tensile strength and generally improves the resistance to oxidation and degradation caused by the influence of light and substances in the atmosphere. In particular, carbon black also improves the mechanical properties at higher temperatures.

In the two-step method, grafting of the unsaturated compound onto the polymer chains can be achieved by mixing the radical-type initiator with the unsaturated compound in the usual roller mixers for rubber with subsequent heat treatment in an oven or press at high temperatures, from 100-250°C. it is preferred to carry out this heat treatment in the absence of oxygen to avoid degradation of the polymer.

Also in the two-step method, the inoculation can be carried out in solution using e.g. the solution of ethylene-propylene copolymer obtained directly during the polymerization. The initiator and the unsaturated compound are then added to the solution whereupon the mixture is heated to high temperatures until the graft polymer is obtained. The product can be recovered by coagulation or evaporation under reduced pressure. The vulcanization can then be carried out as described above.

The vulcanized rubber species according to the invention show very good elastomers

properties that can be varied within a large area by varying: 1) the polymer used as starting material, when using copolymers, especially their composition. 2) the quantity ratio (2 to 20%) and

the type of compound being instilled.

3) the quantity ratio (0.2 to 2%) and

the type of initiator.

4) the proportion (generally between 1 and 50%) of the substance capable of forming salt bridges (e.g. zinc oxide).

When elastomers are produced from e.g. linear, essentially amorphous ethylene-propylene copolymers obtained e.g. by methods according to the patent holder's previous patents, the values for ultimate tensile strength, elastic modulus and compliance with impact increase by increasing the ethylene content when the above stated conditions (2) and (3) are kept constant.

When using increasing amounts of substances capable of forming salt bridges, the properties of the vulcanized products generally vary so that elastomers are obtained with higher values for ultimate tensile strength, elastic modulus and yielding to impact when other conditions are held constant. By mixing 100 parts of an ethylene-propylene copolymer with 2 parts benzoyl peroxide, 7 parts maleic anhydride and various amounts of zinc oxide, after vulcanization at 160°C for 45 minutes, the results listed in table 8 below are obtained.

When finely dispersed metal oxides are used as agents capable of forming salt bridges, an increase in surface hardness and an improvement in resistance to rubbing and scouring is achieved.

When metal oxides are not added to the mixture, the obtained vulcanized pro- | duc transparent what can be t interesting for many applications. Furthermore, the presence of free acidic groups facilitates the adhesion of the products to metal surfaces and they can then be particularly suitable for coating such surfaces.

The saturated or substantially saturated elastomers obtained by the previously described method show, in comparison with strongly unsaturated rubbers, the advantage of a better resistance to oxidation and to the effects of the climate.

Furthermore, the elastomers obtained by the method according to the invention from ethylene-propylene copolymers and which contain from 25 to 80% by weight of ethylene, have a stretch-elongation curve similar to such curves for amorphous products which are able to crystallize upon stretching. It is therefore possible to obtain rubber species which, although they show a low initial modulus, reach high elongations at high loads (see Fig. 3, curve II in the attached drawing). When you e.g. proceeds as indicated in example 13 below, a product is obtained which has a modulus at 100% elongation which is lower than 0.2 kg/cm<2>, an elongation at break of around 500% and a final tensile strength of 1.2 kg/mm2.

In the following, some embodiments of the invention are described as examples.

Example 1:

100 parts of an ethylene-propylene copolymer containing 58 mole percent propylene and with a molecular weight of around 190,000 are brought into a mixer with two rollers and mixed at a temperature of 60° C until a homogeneous foil is obtained. Then, 2 parts of benzoyl peroxide are added over the course of 15 minutes. The mixture is then continued at a lower temperature, namely around 30° C for a further 15 minutes, with 7 parts of maleic anhydride and zinc oxide being added in varying proportions as indicated in the table below. The mixing is then continued until the mass is homogeneous. The product obtained is vulcanized in a press with parallel plates at 160° C for 45 minutes. Samples are taken from the vulcanized foil in accordance with ASTM Specification D412/51 T for examination of tensile strength as well as samples for other physical and chemical examinations. The rebound is determined with a Pirelli device of the Goodyear-Healey "rebound pendulum" type. The swelling ratio is determined using benzene as solvent at 35° C. for 90 hours.

Example 2:

100 parts of an ethylene-propylene copolymer containing 70 mole percent propylene and with a molecular weight of around 130,000 are thus mixed as indicated in example 1 for 20 minutes at 60° C with 2 parts benzoyl peroxide and 9 parts maleic acid and then for 15 minutes at 30° C with 20 parts zinc oxide.

After vulcanization in a press at 160° C for 30 minutes, a vulcanized product with the following properties is obtained:

The shape of the stretch-elongation curve is indicated in fig. 1 in the attached drawing.

Example 3:

100 parts of an ethylene-propylene copolymer with a molecular weight of about 350,000 are mixed for 20 minutes at 60° C. with 3.2 parts of tert. butyl perbenzoate and 9 parts maleic acid. Then 20 parts of zinc oxide are added over the course of 15 minutes at 30° C. After vulcanization in a press at 130° C for 30 minutes, a product with the following properties is obtained:

Example 4:

100 parts of the ethylene-propylene-sam polymer that was used in example 1, is treated in a roller mixer with 3 parts chlorobenzoyl peroxide (Lucidol) and 5 parts maleic anhydride at 60° C. After curing in a press at 160° C for 20 minutes, a product with the following properties is obtained:

Example 5:

A solution is prepared in benzene of an ethylene-propylene copolymer which used in example 1, with a concentration of 50 gr per litres. The solution is kept at 50° C in a nitrogen atmosphere and 10 parts of benzoyl peroxide and 8.3 parts of maleic anhydride are added per 100 parts copolymer, with stirring. The solution thus obtained is stirred for 6 hours, after which the solvent is completely removed by evaporation in a vacuum at 50° C. The product thus obtained is mixed and homogenized in a roller mixer with zinc oxide at 30° C, after which it is matured in a press at 130° C in 45 minutes. By varying the proportion of zinc oxide, the results listed in the table below are obtained.

The fact that the addition of zinc oxide causes an increase instead of a decrease in the rebound shows that zinc oxide actively participates in the vulcanization as it forms cross-links between the chains.

Example 6:

A solution in benzene of the ethylene-propylene copolymer used in example 1 is added 10 parts benzoyl peroxide and 20 parts maleic acid per 100 parts copolymer. The solution is stirred for about 6 hours at 60° C., after which the solvent is removed by evaporation in a vacuum. The resulting mixture is completed, homogenized in a roller mixer, after which it is vulcanized at 60° C. for 20 minutes. You get a product with the following properties:

Example 7:

A solution in benzene of an ethylene-propylene-isoprene copolymer with an iodine number of 23 at a concentration of 40 g/litre and which is kept at 50° C, 8.3 parts maleic anhydride and 10 parts benzoyl peroxide are added per 100 parts by weight copolymer. The solution is stirred for 10 hours, after which the solvent is evaporated under reduced pressure at around 40° C. The copolymer thus treated is mixed for a few minutes at 30° C with 2.5% by weight zinc oxide in a laboratory roller mixer. This mixture is successively vulcanized in a press at 160° C for 45 minutes under a pressure of about 50 kg/cm<2>. The tensile tests give the following results:

Example 8:

To a solution in benzene of an ethylene-propylene-isoprene copolymer with an iodine number of 7 in a concentration of 50 g/litre and which is kept at 50° C, 8.3 parts of maleic anhydride and 10 parts of benzoyl peroxide are added per 100 parts by weight copolymer. After 10 hours, the solvent is evaporated under reduced pressure at about 40° C. A portion of the carefully dried product is homogenized by passing it through a laboratory roller mixer for 3 minutes at 30° C. After vulcanization in a press at 160° C in 45 minutes you get a product with the following properties:

The remaining part of the product is mixed at 30° C for 5 minutes with 2.5% by weight zinc oxide in a roller mixer, after which it is vulcanized in a press at 160° C for 45 minutes. The vulcanized product shows the following mechanical properties:

Example 9:

To a solution in benzene of an ethylene-propylene-isoprene copolymer with an iodine number of 5 in a concentration of 60 g/litre and which is kept at 50° C, 8.3 parts of maleic anhydride and 10 parts of benzoyl peroxide are added per 100 parts copolymer. After 10 hours, the solvent is evaporated in a vacuum at 40° C. A portion of the product is mixed with 2% by weight zinc oxide and vulcanized at 160° C for 20 minutes. The vulcanized product shows the following mechanical properties:

The remaining part of the product is homogenized in the roller mixer and vulcanized in a press at 160° C for 20 minutes. The vulcanized product shows the following mechanical properties:

Example 10:

The starting point is a solution in benzene with a concentration of 30 g/litre of an ethylene-propylene-acetylene copolymer which contains around 0.5% acetylene and is kept at 50° C. To the solution are added 8.3 parts maleic anhydride and 10 parts benzoyl peroxide per . 100 parts by weight copolymer. After 20 hours, the solvent is evaporated under reduced pressure at 40° C. The product is mixed with 2.5% zinc oxide and vulcanized in a press at 160° C for 20 minutes. The vulcanized product shows the following properties:

Example 11:

100 parts of an ethylene-propylene copolymer with a molecular weight of around 340,000 are mixed as indicated in examples 2 and 3 with 2 parts benzoyl peroxide, 10 parts acrylic acid and 20 parts zinc oxide. The mixture is vulcanized in a press at 160°C for 30 minutes. You get a product with the following properties:

Example 12:

10 parts of an ethylene-propylene copolymer as used in example 1 are treated for about 10 minutes in a roller mixer at 60° C with 3 parts of benzoyl peroxide, 20 parts of a mixture of the same copolymer with maleic anhydride containing 42% maleic anhydride. 10 parts of zinc oxide are then added and the mixing operation is continued until a homogeneous plate is obtained. After vulcanization in a press at 160° C, products with the following properties are obtained:

The stretch-elongation curves for these products are shown in fig. 2 in the attached drawing where curve I refers to ripening time 30 minutes and curve II to ripening time 45 minutes.

Example 13:

100 parts of an ethylene-propylene compound

polymer as used in example 1, is treated in a roller mixer at 60° C with 3 parts benzoyl peroxide and then with 8 parts maleic acid and finally with zinc oxide. The product obtained is vulcanized in a press at 160° C for 45 minutes.

You get products with the following properties:

The stretch-elongation curves for these products are shown in fig. 3 in the attached drawing where curve I refers to the product with 5 parts zinc oxide and curve II to the product with 10 parts zinc oxide per 100 parts copolymer.

Example 14:

100 parts of a propylene copolymer as used in example 11 are mixed in the same way with 2 parts of benzoyl peroxide, 9 parts of maleic acid and 10 parts of magnesium oxide. The mixture is vulcanized at 160° C for 1 30 minutes, whereby a product with the following properties is obtained: Final tensile strength kg/cm<2> 132

Elongation at break % 433 Modulus at 100%, kg/cm<2> 24

Rebound at 18° C, % 72 Hardness (international degrees) 59

Example 15:

100 parts of an ethylene-propylene copolymer containing 70 mole percent propylene and with a molecular weight of about 130,000 are introduced into a roller mixer with 2 rollers which is kept at 60° C, together with 2 parts of benzoyl peroxide. The mixture is mixed for 10 minutes, after which 10 parts of maleic acid are added and the mixture is continued for a further time

about 10 minutes. The mixture thus obtained is heated in a press with parallel plates at 160° C for 30 minutes under a pressure of 50 kg/cm<2>.

Half of the product thus obtained is further processed at room temperature for 5 minutes in a roller mixer with 2 rollers until a plastic and homogeneous plate is obtained. 1.5% by weight antioxidant (2,2-methylene-bis-4-methyl-6-tert.butylphenol) and 10% by weight zinc oxide are added to this plate for 5 minutes. The mixture thus obtained is vulcanized in a press at 160° C. for 30 minutes under a pressure of 70 kg/cm<2>.

The other half of the product obtained after the first treatment is mixed in a press at room temperature for 15 minutes in a roller mixer with 2 rollers with 1.5% by weight antioxidant, 10% by weight MPC carbon black and 10% by weight zinc oxide. The product is then vulcanized in a press for 30 minutes at 160° C under a pressure of 70 kg/cm<2>.

From the two vulcanized foils obtained in the manner indicated above, samples are taken for tensile testing using hollow mandrels, as specified in ASTM D412-51T. The tests are carried out with a separation speed for the grippers of 50 mm/minute and at a temperature of 18°C.

The result is the following:

Example 16:

100 parts by weight of an ethylene-propylene copolymer as used in example 15 are mixed for 20 minutes at 60° C. with 1 part by weight of benzoyl peroxide and 3 parts of maleic acid. The mixture is heated in a press for 30 minutes to 160° C under a pressure of 50 kg/cm<2>. The product thus obtained is fed back into the mixer at room temperature and 1.5 parts by weight of antioxidant and 10 parts by weight of zinc oxide are added here.

The mixture is then vulcanized in a press at 160° C for 45 minutes under a pressure of 70 kg/cm<2>. In tensile tests carried out at 18° C, the elastomer thus obtained shows the following properties: Final tensile strength kg/cm<2> 100

Elongation at break % 780 Modulus at 300 % kg/cm<2> 25

Example 17:

100 parts by weight of an ethylene-propylene copolymer containing 60% polypropylene and with a molecular weight of around 150,000 are mixed for 20 minutes at 60° C with 1 part benzoyl peroxide and 3 parts maleic acid. The product is then processed in a press at 160° C for 30 minutes under a pressure of 50 kg/cm<2>.

The product thus obtained is further processed in a mixer whose rollers are kept at around 60° C, with 1.5 parts antioxidant, 6 parts stearic acid, 10 parts zinc oxide and various amounts of MPC carbon black. Mixing is carried out for around 20 minutes, the product is then homogeneous. The vulcanization is carried out at 160° C for 45 minutes under a pressure of 70 kg/cm<2>. With varying amounts of carbon black, the properties of the vulcanized product vary as follows:

Example 18:

100 parts of an ethylene-propylene copolymer with 45 mole percent propylene and a molecular weight of around 200,000 are mixed for 20 minutes at 60° C with 1 part by weight of benzoyl peroxide and 3 parts by weight of maleic acid. The mixture is heated in a press at 160° C for 30 minutes under a pressure of 50 kg/cm<2>. The product thus obtained is further processed for 45 minutes in a mixer whose roller is kept at 60° C., with 1.5 parts by weight of antioxidant, 11.5 parts by weight of stearic acid and 10 parts by weight of zinc oxide. The vulcanization is carried out at 160° C for 45 minutes under a pressure of 70 kg/cm<2>.

In tensile tests, the following results are obtained:

Example 19:

100 parts of an ethylene-propylene copolymer with a molecular weight of 344,000 are mixed for 20 minutes at a temperature of 60° C with 3 parts of maleic acid. The temperature is brought down to 20° C and 0.6 parts tert. butyl peroxide is added. Mixing is then continued for 5 minutes. The material is then heated in a press at 200° C and at a pressure of 70 kg/cm<2> for 30 minutes. The product thus obtained is mixed for 50 minutes at 60° C with 0.5 parts antioxidant, 6 parts stearic acid, 45 parts

MPC carbon black and 5 parts zinc oxide. The vulcanization is carried out at 160° C for 45 minutes.

The product thus obtained gives the following results when tested at room temperature: Ultimate tensile strength kg/cm<2> 281

Elongation at break % 480 Modulus at 100% elongation

kg/cm<2> 31.4

Modulus at 300% elongation

kg/cm2 138

Hardness (international degrees) 76.5 Rebound % 61

Claims (21)

1. Vulcanizable elastomers, characterized in that they essentially consist of polymeric substances selected from linear, essentially amorphous polymers and copolymers essentially containing monomeric units derived from α-olefins with the general formula CH:> = CHR (in which R denotes a lower alkyl group), grafted with a compound which in its molecule contains at least one double bond between carbon atoms and one or more functional carboxylic acid groups, which compound is capable of reacting with said polymeric substance in the presence of an activator which acts with a radical mechanism, such as, for example, an organic peroxide or hydroperoxide. 2. Elastomers as stated in claim 1, characterized in that they essentially consist of an essentially amorphous polymeric substance selected from linear polymers of propylene, butene-1 and copolymers of said olefins with each other and with ethylene, in combination with a compound which in its molecule contains at least one double bond between carbon atoms and one or more functional acid groups, which compound is capable of reacting with said polymeric substance in the presence of an activator which acts with a radical mechanism during polymerization. 3. Elastomers as stated in claim 2, characterized in that they essentially consist of an essentially amorphous polymeric substance selected from linear copolymers of propylene and/or butene-1 with ethylene and a conjugated diolefin having at least one vinyl -double bond, in combination with a compound which in its molecule contains at least one double bond between carbon atoms and one or more functional acidic groups, which compound during polymerization is able to react with said polymeric substance in the presence of an activator that works with a radical mechanism. 4. Elastomers as stated in claim 1, characterized in that they essentially consist of a substance selected from the linear, essentially amorphous copolymers of propylene and/or butene-1 with ethylene and acetylene, in combination with a compound which in its molecule contains at least one double bond between carbon atoms and one or more functional acidic groups which, during polymerization, are capable of reacting with said polymeric substance in the presence of an activator that acts with a radical mechanism. 5. Elastomers according to any of the preceding claims, characterized in that more than 10% of the carbon atoms in the linear, essentially amorphous polymers or copolymers are tertiary carbon atoms. 6. Elastomers according to any of the preceding claims, characterized in that one of the substituting groups on the tertiary carbon atoms is methyl groups. 7. Elastomers according to any of the preceding claims, characterized in that the compound which is combined with the polymeric substance contains a double bond in a conjugated position in relation to the double bonds in one or more of the groups -C = 0 O 8. Elastomers as stated in claim 2 and which are obtained from copolymers of propylene and/or butene-1 with ethylene, characterized in that they contain more than 25% by weight of ethylene. 9. Elastomers as stated in claim 2, obtained from propylene/ethylene copolymers, characterized in that they contain from 25 to 80 percent by weight of ethylene. 10. Elastomers as stated in claim 3, characterized in that they are obtained from copolymers containing from 0.5 to 20 percent by weight of a diolefin such as isoprene or butadiene. 11. Elastomers as stated in claim 3, characterized in that they are obtained from copolymers containing more than 25% by weight of ethylene. 12. Elastomers as stated in claim 3, characterized in that they are obtained from copolymers containing from 25 to 80 percent by weight of ethylene. 13. Elastomers as stated in claim 4, characterized in that they are obtained from copolymers containing 0.5 to 10 percent by weight of acetylene. 14. Elastomers as stated in claim 4, characterized in that they are obtained from copolymers containing more than 25% by weight of ethylene. 15. Elastomers as stated in claim 4, characterized in that they are obtained from copolymers containing from 25 to 30 percent by weight of ethylene. 16. Elastomers according to any one of the preceding claims, characterized in that the compound which during the polymerization is combined with the polymeric substance is maleic anhydride, maleic acid, fumaric acid, acrylic acid or methacrylic acid amide. 17. Elastomers according to any of the preceding claims, characterized in that they contain polyfunctional substances fer that is able to form salts with the acidic groups. 18. Elastomers as stated in claim 17, characterized in that the substance capable of forming salts with the acidic groups is a metal oxide. 19. Elastomers according to claim 18, characterized in that the metal oxide is an oxide of zinc, magnesium or lead. 20. Elastomers as specified in claim 17, characterized in that the substance which is capable of forming salts with the acidic groups is a polyvalent, organic compound, 21. Elastomers according to claim 20, characterized in that the polyvalent organic compound is a diamine or a glycol.