CS262145B1 - Vulcanizable rubber compound - Google Patents

Abstract

Vulcanizable rubber mixture based on ethylene-propylene terpolymer, butyl rubber and diene rubbers or their combinations, further containing fillers, lubricants, stabilizers, vulcanization additives and accelerators, or other additives, which as a modifying component contains per 100 parts by weight of rubber 3 to 30 parts by weight of a mixture of higher molecular weight hydrocarbons formed as a by-product during stereospecific polymerization of polypropylene, which contains 4 to 17% by weight of stereoblocks, 79 to 95.8% of isotactic portions. Technical rubber products modified with the product achieve higher utility parameters, especially in resistance to swelling in mineral oils. Mixing of mixtures and other technological operations of mixtures modified with this product are less energy-intensive.

Description

The invention relates to a rubber mixture based on ethylene-propylene terpolymer, butyl rubber, diene rubbers or their combinations modified with higher molecular hydrocarbons formed as a by-product during stereospecific polymerization of polypropylene, suitable for the production of technical rubber products characterized by higher resistance to swelling in mineral oils.

In technical practice, technical rubber products are sometimes exposed to the impact effects of mineral oils and greases. These include products that are not directly intended for mineral oil environments, such as various types of seals, waterproofing films, hoses, etc. However, in the event of accidental contact with mineral oils, e.g. oil leakage from a hydraulic system, grease splashes, etc., the rubber material swells at the point of contact and, with continued exposure, it breaks down and loses its function.

These are mainly products made on the basis of rubbers - ethylene-propylene terpolymer, butyl rubber, SBR, polyisoprene or natural rubber, which are not intended directly for the environment of mineral oils and in which the use of special rubbers, such as chloroprene, NBR or thiokol, would be uneconomical, especially in terms of the fact that special rubbers are imported from areas with unfavorable foreign exchange rates. In some cases, especially in the case of butadiene-styrene rubbers, the resistance of vulcanizates to swelling in oils can be increased by modification using reactive phenol-formaldehyde resins. The disadvantage of the above procedure is an increase in the hardness of the vulcanizate, which may be undesirable in some cases, a decrease in the processing safety of the mixture against vulcanization, and phenol-formaldehyde resins are expensive.

The above-mentioned shortcomings are eliminated by the subject of the invention, which is a vulcanizable rubber mixture based on ethylene-propylene terpolymer, butyl rubber and diene rubbers or their combinations, further containing fillers, lubricants, stabilizers, vulcanization additives and accelerators, or other additives, characterized in that as a modification component it contains per 100 parts by weight of rubber 3 to 30 parts by weight of a mixture of higher molecular weight hydrocarbons formed as a by-product during stereospecific polymerization of polypropylene, which contains 4 to 17 wt. %/o stereoblocks, 79 to 95.8 wt. %/o atactic portions and 0.2 to 3 wt. % isotactic portions.

The principle of the invention is vulcanizable rubber mixtures, especially based on ethylene-propylene terpolymer, butyl rubber, diene rubbers containing fillers, plasticizers and other rubber additives modified with a mixture of high molecular weight hydrocarbons of a precisely defined composition formed as a by-product during stereospecific polymerization of polypropylene. It has been found that the product improves the resistance to swelling in mineral oils and especially to thermal aging of vulcanizates also based on butadiene-acrylonitrile rubber.

The decisive influence on the resistance of rubber mixtures to the effects of mineral oils is the content of isotactic portions and stereoblocks in the product used. It has been found that when the content of stereoblocks is lower than 4 wt. % and the content of isotactic portions is less than 0.2 wt. % in the product, the ability of the vulcanizate to resist the effects of mineral oils and aggressive chemicals decreases significantly.

At a stereoblock content of over 17 wt. % and isotactic fractions of over 4 wt. %, the resistance of vulcanizates to mineral oils no longer increases significantly, but the processability of rubber mixtures and the tackiness of the finished product deteriorate. At a high content of isotactic fractions above the specified limits in the mixture, these fractions are present in the product as undispersed particles forming their own phase, the product is inhomogeneous, and the rubbers then show lower resistance to swelling in mineral oils and significantly lower physical and mechanical properties.

' Stereoblocks are understood to mean the part of the product 'that cannot be dissolved in organic solvents, e.g. n-heptane at room temperature, dissolving only at temperatures above '100 °C.

' Isotactic polypropylene as part of the product has a crystalline structure, a high softening point, is characterized by high resistance to aggressive agents even at high temperatures, this property is due to the regular spatial arrangement of the methyl group along the main chain. The product with a defined composition can act simultaneously in rubber mixtures as a polymer plasticizer, reduces the viscosity of rubber mixtures, and mixing rubber mixtures is less energy-intensive. The product improves the ready-to-wear adhesion and processing properties of mixtures, e.g. injectability, extrusion, etc. The content of atactic components in the product and the molecular weight have an influence on the above-mentioned properties of the mixture. From a technical point of view, types with a molecular weight of 16,000 to 50,000 are suitable. However, a higher content of atactic components above the above-mentioned content of the invention causes a sharp decrease in the mechanical properties of the vulcanizates. In products with a higher content of isotactic components according to the invention, the mechanical properties of the vulcanizates can be increased by adding them to rubber mixtures, or alternatively, a part of the rubber, plasticizers or resins in the mixtures can be replaced while maintaining the basic properties of the rubber.

' By selecting the type of product and combining (all components of the rubber mixture) rubbers can be prepared according to the requirement, e.g. characterized

'with higher strength and structural strength than- 'mass parts more modulus, hardness, etc. The optimal dosage ' «thylene-propylene 'forging the product into· rubber mixture ie ' terpolymer 100 ‘it is necessary to determine experimentally for each case ' zinc oxide 5 tally with regard to the resulting required ' stearic acid 1 'properties of vulcanizate. Subject invention ¹ soot 70 ‘can be used in the production of products with higher ¹ mineral oil 25 ‘technical and economic parameters, such as ' coumarone resin 3 'e.g. hoses, waterproofing membranes sealants ¹ kaolin 120 elements etc. The above, and others application ' 2-mercapto-benzothiazole 0.5 ‘cannot be considered as a limitation of the scope of the invention- ¹ diethyl dithiocarbomidate to. ' zinc 1.5 sulfur 2 'Example 1 • The mixture was mixed in a larger quantity The EPDM-based rubber compound was and divided into 3 parts by weight. Into two mixed a mixture of the following composition parts of the mixture were mixed 30 parts by weight the number of molecular hydrocarbons in the following- composition. The third part consists of basic mixture 1 without the addition of a modifying component. Mixture 1 2 3 eosphere of stereoblocks 17 2.9 — content of isotactic fractions 3 0.1 — content of atactic moieties 80 97 — Dosing of modifying additives it is stated- at a temperature of 150 °C, from samples rubbers were -hundreds- measured in parts by weight per 100 parts by weight updated basic physical-mechanical values- parts of rubber component in the mixture. Samples notes and rubber resistance values determined rubber compounds were vulcanized 30 against swelling in mineral oils. Mixture No. 1 No. 2 No. 3 tensile strength, MPa 10.2 6.2 9.6 elasticity, % 480 420 310 hardness, Sh A 70 63 72 elasticity, % 28 26 33 structural strength Graves without a notch, - N . mm' ¹ 33.9 26.8 29.2 swelling 70 h, 23 °C min. oil ASTM 1, %wt. 4.2 8.6 6.5 ASTM 2, %wt. 5.3 12.8 7.9 ASTM 3, %wt. 19.5 32.3 27.3

In the examples given, a higher effect of the modifying component according to the invention (mixture no. 1j.) can be observed.

Example 2. In recipes No. 2 and 3, part of the rubber and mineral oil was replaced with a higher molecular weight butyl rubber mixture in combination with EP-cyclic hydrocarbons.

DM was mixed with a mixture of the following s,lo- ¹ β 2 1 4 S

No. 1 parts by weight No. 2 parts by weight No. 3 parts by weight ethylene-propylene ter- polymer 60 50 50 butyl rubber 40 30 30 zinc oxide 5 5 5 stearic acid 1 1 1 silicon dioxide 20 20 20 titanium dioxide 15 15 15 kaolin 100 100 100 mineral oil 10 6 6 2-mercaptobenzothiazole 2 2 2 tetramethylthiuram disulfide 1.5 1.5 1.5 sulfur 1.5 1.5 1.5 high molecular weight hydrocarbons according to specification A — 24 — according to specification B — — 24 Composition of higher molecular weight Species. A Species B hydrocarbons stereoblock content 10 0.5 content of isotactic fractions 2 3.5 atactic moiety content 88 96

Samples of rubber mixtures were vulcanized for 30 minutes at a temperature of 150 °C, basic physical and mechanical values were determined from the samples, and the values of rubber resistance to swelling in mineral oils were determined.

Mixture No. 1 No. 2 No. 3 tensile strength, MPa 6.2 7.6 5.1 elasticity, % 750 680 710 hardness, Sbore A 52 54 50 elasticity, % 22 20 19 structural strength Graves without a notch, N. mm ^-1 25.5 26.7 25.8 swelling 70 h, 23 °C min. oil ASTM 1, w/w wt. 7.9 6.8 12.2 ASTM 2, %wt. 8.9 7.2 18.6 ASTM 3, %wt. 28.5 21.3 39.1

In the examples given, a higher effect of the modifying component according to the invention (mixture No. 2) can be observed.

Example 3

A mixture of the following composition was mixed from a rubber mixture based on a combination of polyisoprene rubber and butadiene-styrene rubber.

parts by weight polyisoprene rubber 30 butadiene-styrene rubber 70 carbon black 70 polyvinyl chloride 8 mineral oil 5 stearic acid 1 phenyl-^-naphthylamine 1 rosin 1 zinc oxide 7

N-cyclohexyl-2-benzthiazyl sulfenamide 1.5 sulfur 2.1

The mixture was mixed in a larger quantity and divided into 3 parts by weight. Into two parts of higher molecular hydrocarbons in the following composition, the third part is the basic mixture without the addition of modifying components. The mixtures were vulcanized for 20 minutes at a temperature of 150 °C, the values of resistance to swelling in oils and basic mechanical values were determined from the samples.

Mixture 1 No. 1 2 n, 2 3 No. 3 stereoblock content 8 20 _ content of isotactic ipods 0.3 5 — atactic moiety content 91.7 75 — tensile strength, MPa 11.9 9.8 12.6 elasticity, % 430 390 490 hardness, Shore A 66 65 68 elasticity 28 28 30 structural strength Crescent without 'notch, N .mm' ¹ 98.3 96.6 102.6 swelling 188 h, 23 °C min. oil ASTM 1, %wt. 64 67 76.1 ASTM 2, %wt. 22 23 26.0 ASTM 3, %wt. 78 80 90.6

The examples given can be observe higher effect of the modifying component of the finding (mixture no. 1). according to the -phenylenediamine 1,8 tetramethylthiuram disulfide 3.2 Example 4 N-cyclohexyl-2-benzthiaz;yl sulfenamide 1,3 From a rubber compound based on butadiene- N-cyclohexylthiophthalimide 0.3 -acrylonitrile rubber was mixed sulfur 0.4 a mixture of the following composition: 'mass parts -The mixture was mixed in a larger quantity and divided into three parts by weight. Into two butadiene acrylonitrile parts of the mixture were mixed with 22 parts by weight rubber 100 the number of molecular hydrocarbons in the following- soot 100 composition, the third part is the basic mixture calcium carbonate 11 without the addition of a modifying ingredient. dibutyl phthalate 21 The mixtures were vulcanized for 20’ at a temperature stearic acid 1.8 150 °C, the basic parameters were determined from the samples zinc oxide 10 mechanical values and values after thermal phenyl-/?-naphthylamine N-isopropyl-N-phenyl-p- 1.8 aging in hot air. Mixture 1 2 3 stereoblock content 15 3.8 — content of isotactic fractions 0.2 0.1 - atactic moiety content 84.8 96.1 — Mixture No. 1 No. 2 No. 3 tensile strength, MPa 1.1.8 9.6 11.2 elasticity, % 235 210 220 hardness. Sh A 67 68 69 elasticity, % 38 38 38 elasticity, % 5 5 5

Change in mechanical properties of rubbers after aging in hot air for 70 h at temperatures of 70 °C and 1Ό0 °C, the change is given in %.

Mixture No. 1 No. 2 No. 3

70°C 100°C 70°C 100°C 70°C 100°C tensile strength — 5.6 +21.3 - 7.8 +33.9 — 6.9 +36.8 tenderness —18.6 —28.4 —23.4 —40.1 —22.7 —39.2 hardness + 7.0 +17.6 + 8.9 +22.9 + 8.6 +22.4

In the examples given, a higher effect of the modifying component according to the invention (mixture No. 1) can be observed.

Claims (1)

Vulcanizable rubber composition based on ethylene-propylene tierpolymer, butyl rubber and diene rubbers or combinations thereof, further comprising fillers, lubricants, stabilizers, vulcanizing additives and accelerators, or other additives characterized by containing as modifying component INVENTION per 100 wt. 3 to 30 wt. parts of a higher molecular weight hydrocarbon mixture formed as a by-product of the stereo-specific polymerization of polypropylene containing 4 to 17 wt. % Of stereoblocks, 79 to 95.8 wt. % atactic fractions and 0.2 to 3 wt. % isotactic proportions.