DE1290716B - Vulcanization of mixtures of rubber and polyethylene - Google Patents

Description

Often one has tried to use lower proportions of both polyethylene incorporating natural as well as synthetic rubber in order to respect the rubber its processing properties, especially in terms of compressibility and ozone resistance to improve. However, these attempts on the whole have not been successful because Polyethylene with rubber under normal circumstances not or only to a very small extent Mixing ratios is compatible.

Conversely, attempts were also made to incorporate lesser amounts of polyethylene Modifying proportions of rubber, but these attempts have also met with little success had.

It is known that certain diaralkyl peroxides of the general formula where Rl is an aryl group, R6 is hydrogen or an alkyl or aryl group and R2, R3, R4 and R5 are hydrogen and alkyl groups with less than 4 carbon atoms, are very effective vulcanizing agents for both natural and synthetic rubber. It is also known that the same peroxides are effective crosslinking agents for polyethylene and copolymers of ethylene and propylene.

It was surprising, however, that it unlike other vulcanizing agents enable the simultaneous vulcanization of rubber and polyethylene.

According to the invention, a method for vulcanizing mixtures of first natural rubber or a synthetic rubber-like polymer of a conjugated diolefin or chloroprene and second polyethylene in a mixing ratio of 1:20 to 20: 1, characterized in that the components of the mixture at a temperature above the crystalline melting point of the polyethylene and then mixed at a temperature below 135 "C with a peroxide of the formula where Rl is an aryl group, R6 is hydrogen or an aryl or alkyl group, R2, R3, R4 and R5 are hydrogen or alkyl radicals with less than 4 carbon atoms, mixed and the resulting mixture vulcanized in the usual way.

Accordingly, rubber and polyethylene are first at one temperature mixed above the crystalline melting point of the polyethylene. After mixing The peroxide is incorporated into the two substances. Do not need any special Precautions are taken other than avoiding excessive temperature and too long a time which scorches, d. H. premature vulcanization during of mixing. The risk of burning can be kept to a minimum by mixing in the peroxide in a maximum of 12 minutes at 135.degree or performed at any milder time and temperature combination will. Finally, the mixture is deformed at an elevated temperature, whichever is higher but also cannot be higher than the mixing temperature until mixed vulcanization is effected. The temperature during mixing is one of the most important Features of the invention because proper colloidization at a lower temperature of rubber and polyethylene does not take place and a real mixed vulcanization cannot be done. The heating of the mixture is of such a duration that that the products produced become almost transparent during stretching and thus prove that the mixed vulcanization of rubber and polyethylene has been effected.

Synthetic rubbery ones useful in the practice of the invention Polymers include, for example, polymerization products of butadiene and its Derivatives and homologues such as methylbutadiene, dimethylbutadiene, isoprene, pentadiene and chloroprene. The definition also includes rubbery interpolymers of conjugated diolefins with other unsaturated organic compounds, such as Styrene, acrylonitrile, isobutylene.

According to the invention, a mixed vulcanizate of polyethylene and the rubber formed by first these two substances together with one smaller proportion of a peroxide of the formula I are mixed.

The relative amounts of polymer, rubber and peroxide are wide Boundaries changeable.

The ratio of rubber to polymer can be approximately from about 70: 1 to 1:20 to either a rubber modified with the polymer or to obtain a rubber modified polymer as desired. The amount of peroxide is also subject to fluctuations, the amount of peroxide generally being between Will be 0.1 to 10 ° o of the total weight of rubber and polymer. the best amount is usually 0.4 to 7.5 () / on the same basis.

The mixed vulcanization of rubber and polyethylene is thereby causes the mixture of polymer, rubber and peroxide at an increased Temperature forms, preferably between about 130 to 190 'C, but better between 150 to 180 C. The best heating time is often between 2 to 100 minutes.

In the following examples, the term »more crystalline Melting point «the temperature which is reduced by the disappearance of the birefringence a polarizing microscope.

Unless otherwise stated, parts and percentages relate to on weight.

Example 1 The constituents parts of the butadiene-styrene copolymer .... 200 polyethylene (high pressure type density at 25 ° = 0.915 to 0.920, more crystalline Melting point = 110 to 115 "C) .. 98 diphenylguanidine ...... .. .... 2 bis (a, a-dimethylbenzyl) peroxide 6 6 Light plasticizer oil *) 18 clay .................... 50.4 Precipitated calcium silicate .. 145 magnesia. ....... ..... 20 *) Trade name Circo: »Chemical Trade Names and Commercial Synonyms ", Haynes D. Van Nostrand Co., Inc. (1951), p. 74 mixed together on a two-roll mill, first the rubber and the polyethylene blended at a temperature of 1270C and then the rest of the ingredients in the order given after lowering the temperature on the mill was added to about 32 to 43 ° C.

After the mixture became homogeneous on the mill, it became taken out as a sheet about 6 mm thick, and parts thereof were taken out in a Mold of 80 x 160 x 6 mm vulcanized for 20 and 40 minutes at 145 ° C.

Both mixed vulcanizates were translucent.

Example 2 A master batch consisting of the following components Part No. 1 smoked sheets natural rubber .. 300 high density polyethylene (density at 25 ° = 0.945, crystalline melting point = 130 to 135 ° C) ......... 75 2,2'-methylene-bis- (4-ethyl-6-tert-butylphenol) ........ .......... 3 was made on a two-roll mill at a temperature of 74-C by adding the Components made in the order shown. The stock approach was then split in half and grind the first half (A) for 5 minutes at 154- C, removed from the mill, the rollers cooled to 74 ° C and then returned to the mill. There are then 2.5 parts of bis (a, l-dimethylbenzyl) peroxide for this portion of the stock batch added, which is incorporated by grinding for three more minutes became.

The second half of this stock batch (B) was kept at 74 ° C during Grind for 5 minutes. Then 2.5 parts of bis (aa-dimethylbenzyl) peroxide were added and grinding continued for three more minutes.

The mixtures produced in this way were then vulcanized in a mold measuring 160 x 160 x 1.8 mm for two different times at 154-C. module Vulcanization time (kg / cm2) Tensile strength Elongation Bashor Shore A2 hardness mixture elasticity (Minutes) 100% 200% 300% 400% (kg / cm2) (%) A 0 200 340 470 45 390 39 51 15 250 440 650 1000 184 600 50 53 30 270 470 700 1060 170 535 52 54 B 0 - - - - - 180 10 48 15 200 400 640 940 82 410 39 52 30 220 440 650 1000 107 460 45 54 The data show that poor results are obtained when the blending of rubber and polyethylene is carried out at a temperature below the crystalline melting point of the polyethylene.

Example 3 Two mixtures of the following ingredients: Mixture 1 Mixture 2 Palcerepe natural rubber 50 parts 250 parts High pressure polyethylene as in example 1 l 450 parts 250 parts Bis- (a, a-dimethylbenzyl) - peroxide ........ 7.5 parts 7.5 parts were mixed on a roller mill, the ingredients being added in the order given. Both mixtures were milled at a temperature of 121-132LC, but since the second mixture was sticky at the mill temperature, the mill was cooled to 82 ° C before the mixture was removed from the mill.

Each mixture was poured into a 25.4 x 115 x 1.2 mm mold during 45 Vulcanized minutes at 149 ° C.

The vulcanizates obtained showed the effect of mixed vulcanization, because they were almost see-through after stretching.

Example 4 500 parts of Palcerepe natural rubber were mixed with 7.5 parts Bis (a, a-dimethylbenzyl) peroxide ground on a two-roll mill at 66 to 79 ° C.

Portions of this mixture were then mixed with specific amounts of the mixture 2 of Example 3 further mixed. Five mixtures with contents of 5, 10, 15, 20 and 25% polyethylene based on the total weight of polyethylene and Rubber. Samples of each mixture were then placed in for 30 minutes at 149 ° C vulcanized into a shape of 25.4 x 115 x 1.2 mm. Every mixture had the property becoming more see-through as you stretch.

Example 5 A master batch of the following composition parts butyl rubber ..... ........ 200 polyethylene as in example 1 ........ 20 semi-reinforcing furnace carbon black 160 160 zinc oxide ........ ..... ..... 10 red lead (Pb304) ..... 20 quinone dioxime .... 4 sulfur. ........ ..... 4 was manufactured by first using polyethylene at a Grind the temperature of 121tC and then the rubber while lowering the temperature was added to about 74 ° C. The rest of the ingredients were also used in the latter Temperature added in the order given. The stock approach was then divided into four equal parts, and to three of these parts became a certain amount of bis (a, a-dimethylbenzyl) peroxide with grinding at a temperature of 74 «C added. In this way four mixtures were obtained which were 0, 0.25, Contained 0.5 and 1 part of peroxide per 50 parts of butyl rubber.

Portions of these mixtures were applied for 7.5, 15, 30 and 60 minutes 166 C vulcanized in a shape of 25.4 x 115 x 1.2 mm. Any shaped pattern was mixed vulcanized due to its properties.

Example 6 The procedure of Example 3 was followed with the modification repeats that the polyethylene by the same amount of a rubbery Copolymer of ethylene and propylene (50:50 molar ratio) replaced and the grinding temperature was reduced to about 80 C. Excellent mixed vulcanizates were obtained, which had the property of becoming almost translucent when stretched.

Example 7 The procedure in Example 3 was followed with the modification repeats that the bis (a, a-dimethylbenzyl) peroxide is replaced by each of the following Peroxide was replaced in the production of five other mixtures: Methyl- (a, a-dimethylbenzyl0-peroxide, Bis- (a, a-dimethyl-p-tert-butylbenzyl) -peroxide, bis- (a, a-dimethyl-p-isopropylbenzyl) -peroxide, Bis (a, a-dimethyl-p-methylbenzyl) peroxide, bis (a-isopropylbenzyl) peroxide, benzyl (a, a-dimethyl-p-isopropylbenzyl) peroxide.

The properties of the mixed vulcanizates obtained were the obtained according to Example 3 similarly.

Claims (1)

Claim: Process for vulcanizing mixtures of first natural rubber or a synthetic rubber-like polymer of a conjugated diolefin or chloroprene and second polyethylene in a mixing ratio of 1:20 to 20: 1, characterized in that the components of the mixture are at a temperature above the crystalline melting point of the Polyethylene mixed and then at a temperature below 135 C with a peroxide of the formula where R, an aryl group, R (, hydrogen or an aryl or alkyl group. R2, R3, R4 and R, hydrogen or alkyl radicals with less than 4 carbon atoms are mixed and the resulting mixture vulcanized in the usual way.