RU2455320C2 - Method of modifying rubber - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to the technology of industrial rubber articles, particularly methods for bulk modification of rubber in order to slow down ageing processes taking place in rubber and industrial rubber articles during prolonged storage and use. The method of modifying ethylene propylene-based rubber involves adding a modifying additive into a rubber mixture and vulcanising. The modifying additive used is modified rubber crumbs of the following composition, pts.wt: rubber SKEPT 40-100, sulphur 2, zinc oxide 5, thiuram D 0.75, altax 0.5, dithiodimorpholine 1.5, stearin 1, triethanolamine 2, aerosil A-175 30, technical rubber K-354 2, antiageing agent carbamate BNI 8 340. The modified rubber crumb is obtained by crushing the vulcanised rubber from the rubber mixture and then added in amount of 20-40 pts.wt per 100 pts.wt rubber.

EFFECT: invention increases heat-resistance of rubber when exposed to air and high temperatures.

5 tbl, 1 ex

Description

The invention relates to the technology of rubber products, in particular to methods for bulk modification of rubbers in order to slow down the aging processes that occur during long-term storage and use in rubbers and rubber products.

A known method of volumetric modification of rubber (Koshelev F.F., Kornev A.E., Bukanov AM General technology of rubber. - M .: Chemistry, 1978, p.203-226) in order to slow down the aging process, which consists in the composition of the rubber mixture is administered by antioxidants. As antioxidants by a known method, it is proposed to use low molecular weight compounds of the following classes: primary aromatic amines, secondary aromatic amines, secondary aromatic diamines, condensation products of primary and secondary amines with aldehydes or ketones, substituted monophenols, substituted bisphenols, phosphoric acid esters, dithiocarbates and nickel.

The disadvantage of this method is the low solubility of the proposed antioxidants in non-polar rubbers, which leads to the fading of antioxidants from rubbers and rubber products during long-term storage and to a decrease in their concentration in volume, and as a result, a decrease in the efficiency of volumetric modification while slowing down the aging process during the operation of rubbers and rubber products. In addition, the antioxidants proposed in the known method slow down the vulcanization of rubber compounds by peroxides, and sometimes completely suppress it, which makes it difficult to use the known method of volume modification for rubbers containing a peroxide vulcanization group.

A known rubber mixture and method of its modification (Isakovich VN and others. Stabilization of rubbers based on SKEP-40 with modified amine stabilizers // Rubber and Rubber, 1986, No. 7, p. 4-6) containing products as a modifying additive condensation of diaphen NN with sulfur monochloride of the following composition, parts by weight:

Rubber SKEP-40 one hundred Sulfur 0.4 Zinc oxide 3.0 Cumyl Peroxide 3.0 Carbon black P-803 fifty Condensation product HH diaphene with sulfur monochloride 2.0

The disadvantage of this method is the lack of resistance of rubber to thermo-oxidative aging in air at high temperatures, which complicates its use for the manufacture of rubbers and rubber products, long-term operation at high temperatures.

A known method of producing a rubber mixture (RF patent No. 2383562, IPC C08J 11/04, C08J 3/20, C08L 17/00, B02C 17/08, C08L 9/02, 03/10/2010) using rubber crumb from tire waste and production rubber products, which consists in the fact that the pre-treated rubber crumb is introduced into the composition of the rubber composition.

The disadvantage of this method is the lack of resistance of rubber to thermo-oxidative aging, which makes it difficult to use it for the manufacture of heat-resistant rubbers and rubber products that are used for a long time at elevated temperatures.

The closest in technical essence and the problem to be solved is a rubber mixture and a method for its volume modification (RF patent No. 2036941, IPC C08L 23/16, C08K 13/02, 06/09/1995) containing magnesium oxide and a thermal stabilizer as a modifying additive, which represents is an oligomeric condensation product of melamine with sulfur monochloride, of the following composition, parts by weight:

Rubber SKEP-40 one hundred Sulfur 0.3-0.4 Zinc oxide 3.0-6.0 Magnesium oxide 7.0-15.0 Peroximon F-40 5.0-7.0 Carbon black P-803 60-90 Oligomeric Condensation Product melamine with sulfur monochloride 0.8-1.5

The disadvantage of this method of rubber modification is the low solubility of the proposed antioxidant in rubber, which makes it difficult to introduce into the rubber an increased dosage of the antioxidant necessary for rubbers and rubber products operating at high critical temperatures, that is, temperatures close to the temperature of destruction of the elastomeric matrix.

Thus, the known methods do not allow modification of rubbers in a wide range of dosages of antioxidants for rubbers and rubber products operating at high temperatures (in practice, the upper limit of the dosage of antioxidants does not exceed 2-4 parts by weight per 100 parts by weight of rubber), which reduces their consumer and operational qualities.

The reason that impedes the achievement of the required technical result when using known methods of rubber modification is the low solubility of the proposed modifying additives (antioxidants) in non-polar rubbers, on the basis of which rubbers and general-purpose rubber products are generally made and designed for operation at elevated temperatures.

In this regard, an important task is the development of a new method of rubber modification, which would significantly expand the dosage range of antioxidants and ensure that the antioxidant is retained in the volume of the material, thereby preventing it from fading from rubbers and rubber products and increasing the service life of finished products. Moreover, the proposed method of rubber modification should not suppress the vulcanization of rubber compounds with peroxides, which are widely used for the manufacture of heat-resistant rubbers.

The technical result of the proposed method is the ability to increase the heat resistance of rubbers under the influence of air and elevated temperatures, estimated by the aging coefficients in tensile strength and elongation at break.

The technical result is achieved by the fact that for the modification of rubbers based on ethylene propylene rubber, including the introduction of a modifying additive into the rubber composition and subsequent vulcanization, the previously obtained modified rubber crumb in an amount of 20-40 parts by weight is used as a modifying additive. per 100 parts by weight rubber of the following composition, parts by weight:

Rubber SKEPT-40 one hundred Sulfur 2.0 Zinc oxide 5,0 Tiuram D 0.75 Altax 0.5 Dithiodimorpholine 1,5 Stearin 1,0 Triethanolamine 2.0 Aerosil A-175 thirty Carbon black K-354 2.0 Antioxidant BNI carbamate 8-340

In the proposed method, the antioxidant in the composition of the rubber mixture is not introduced in the traditional way. In the manufacture of a base rubber composition, an antioxidant is administered as part of a previously prepared modified rubber crumb. Thus, the proposed method allows you to enter into the composition of the rubber compound a sufficiently large amount of antioxidant to increase heat resistance and increase the service life of products based on it. During long-term storage or operation of rubbers and rubber products, the antioxidant migrates from pre-modified crumb rubber to the volume of the rubber product. Thus, firstly, the volume of the rubber product is saturated with an antioxidant (modifying additive). Secondly, as the antioxidant is consumed during storage or operation of the rubber product, the concentration of the antioxidant (modifying additive) in the volume is restored due to the migration of a new portion of the antioxidant from pre-modified rubber crumbs; modified rubber crumb acts as microcontainers filled with antioxidant (modifying additive). Thirdly, by regulating the filling of the modified rubber crumb with an antioxidant, it is possible to compensate for the increased consumption of the antioxidant during aging of rubber under conditions of exposure to air and elevated temperatures, and thereby increase the time of guaranteed performance of rubbers and rubber products.

In the proposed method, the following components are used.

Rubbers - SKEPT-40 ethylene-propylene diene rubber containing dicyclopentadiene dicyclopentadiene (TU 2294-022-05766801-2002), SKEP-40 ethylene-propylene rubber (TU 2294-022-05766801-2002) as a diene copolymer.

The vulcanizing agents are sulfur (GOST 127-76), dithiodimorpholine (TU 2478-033-05807983-2002), peroximon F-40 (import).

Thiuram D (TU 6-14-943-79) and Altax (TU 6-14-851-86) are used as vulcanization accelerators.

As vulcanization activators, zinc oxide (GOST 202-84), stearin (GOST 6484-96) and triethanolamine (TU 6-09-2448-91) are used.

Fillers - carbon black P-803 (GOST 7885-86), carbon black K-354 (GOST 7885-86), Aerosil A-175 (GOST 14922-77).

As the base rubber mixture for the manufacture of modified rubber crumb, the rubber mixture according to TU 40-461-806-54-96 “Heat-resistant rubber mixture” is used.

Nickel dibutyl dithiocarbamate - BNI carbamate (TU 6-22-4850-5-92) is used as a modifying additive.

Samples are tested according to GOST 270-75 “Rubber. Method for determination of tensile strength properties ", GOST 265-77" Rubber. Test methods for short-term static compression ", GOST 9.024-74" Unified system of protection against corrosion and aging. Rubber. Test methods for resistance to thermal aging. "

Rubber crumb, filled with antioxidant, receive the following method. The manufacture of the rubber compound is carried out on rollers, for example, type LB 450 225/225. The mixing process on the rollers at the stage of preparing the rubber for mixing (dissolution) and the introduction of the ingredients is carried out for a period of at least 20 minutes. The vulcanization of the rubber mixture is carried out at a temperature of 150 ° C for 60 minutes. Then the resulting vulcanizate is crushed into rubber crumb on crushing rollers, for example, type DR 800 490/610. Then the resulting rubber crumb is used as a modifying additive.

The invention is illustrated by the following examples.

Example 1. Prepare rubber mixtures in accordance with table 1. The mixture of rubber ingredients is produced on rollers LB 450 225/225. The input mode of the ingredients is presented in table.2. Then, rubber plates 2.0 ± 0.5 mm thick are vulcanized from the prepared rubber compounds. The vulcanization of the rubber mixture is carried out at a temperature of 150 ° C for 60 minutes. The resulting rubber plates are crushed into rubber crumb on crushing rollers DR 800 490/610.

Since the rubbers obtained in example 1 are processed into rubber crumb and perform the function of a modifying additive, the physical, mechanical and other indicators for them were not determined.

Table 1 Composition of rubber crumb. Names of components, parts by weight Modifier additive code BNI-1 BNI-2 BNI-3 BNI-4 BNI-5 Rubber SKEPT-40 one hundred one hundred one hundred one hundred one hundred Sulfur 2.0 2.0 2.0 2.0 2.0 Zinc oxide 5,0 5,0 5,0 5,0 5,0 Tiuram D 0.75 0.75 0.75 0.75 0.75 Altax 0.5 0.5 0.5 0.5 0.5 Dithiodimorpholine 1,5 1,5 1,5 1,5 1,5 Stearin 1,0 1,0 1,0 1,0 1,0 Triethanolamine 2.0 2.0 2.0 2.0 2.0 Aerosil A-175 thirty thirty thirty thirty thirty Carbon black K-354 2.0 2.0 2.0 2.0 2.0 Antioxidant BNI carbamate 8 16 52 78 340

table 2 The mode of preparation of the rubber mixture according to example 1 Technological operation Operation start time after the first boot, min Loading and dissolving rubber 0 Download zinc oxide, stearin 5 Loading of aerosil, carbon black, BNI carbamate, triethanolamine 8 Loading of sulfur, altax, dithiodimorpholine, tiuram eighteen Rubber compound removal twenty

The rubber mixtures according to examples 2-7, the compositions of which are given in table 3, are prepared analogously to example 1 (the mode of input of the ingredients is presented in table 4). Physico-mechanical properties of the prototype and rubbers modified by the proposed method according to examples 2-7 are shown in table 5.

As can be seen from the data presented, the rubbers modified by the proposed method, firstly, surpass the prototype in terms of a set of physicomechanical indicators (conditional tensile strength exceeds the known rubber by 35%, and the elongation at break is 100- higher than that of the known rubber 290%). Secondly, the heat resistance of rubber according to examples 2-6, estimated by the aging coefficients in tensile strength and elongation at break, is not inferior to known rubber or exceeds it by 1.15 times. Thirdly, the proposed modification method improves the heat resistance of rubbers when exposed to air from 150 ° C to 200 ° C. The control rubber mixture (example 7) was modified in the traditional way. As the data of example 7 show, the antioxidant introduced by the known method, firstly, inhibits peroxide vulcanization, which is reflected in the low physical and mechanical characteristics of rubber and high residual deformation after rupture (exceeds the value of this indicator in the prototype and rubbers in examples 2 -6 to 30 times). Secondly, there is a fading of the modifier on the surface of the samples obtained according to example 7, and the absence of fading of the modifier in samples modified by the proposed method (examples 2-6).

Thus, the above information indicates the fulfillment of the following set of conditions when using the claimed invention:

the method embodying the claimed invention in its implementation, allows you to modify the rubber;

Table 3 The composition of the rubber compounds by examples Names of components, parts by weight 2 3 four 5 6 7 (counter) Rubber SKEP-40 one hundred one hundred one hundred one hundred one hundred one hundred Sulfur 0.35 0.35 0.35 0.35 0.35 0.35 Zinc oxide 4,5 4,5 4,5 4,5 4,5 4,5 Peroximon F-40 6.0 6.0 6.0 6.0 6.0 6.0 Carbon black P-803 75 75 75 75 75 75 Rubber crumb BNI-1 40 - - - - - Rubber crumb BNI-2 - twenty - - - - Rubber crumb BNI-3 - - thirty - - - Rubber crumb BNI-4 - - - 40 - - Rubber crumb BNI-5 - - - - twenty - Antioxidant BNI carbamate - - - - - 2.0

Table 4 The mode of preparation of rubber compounds according to examples 2-7 Technological operation Operation start time after the first boot, min Loading and dissolving rubber 0 Loading of zinc oxide, sulfur, peroximon 5 Download modifying additive or carbamate BNI 8 Carbon black loading 10 Rubber compound removal fifteen

Table 5 Modified Rubber Properties Names of indicators Prototype (US Pat. RF No. 2036941) by examples 2 3 four 5 6 7 (counter) Conditional tensile strength, MPa 10.9 10,4 13.7 16.3 11.1 14.7 4.6 Elongation at break,% 190 390 395 740 670 615 840 Residual strain after rupture,% 2 four 8 33 34 21 60 Shore A hardness, conv. units 81 62 75 65 63 72 45 Air aging at 150 ° C for 240 hours, aging coefficient: by conditional strength 0.96 0.94 0.96 0.98 1.05 1,1 0.95 relative elongation 1.05 0.90 0.92 1.01 1,03 1,2 0.91 Air aging at 200 ° C for 24 hours, aging coefficient: by conditional strength collapsed 0.1 0.1 0.12 0.14 0.18 0.1 relative elongation 0.34 0.39 0.33 0.28 0.52 0.30 The content of BNI carbamate per 100 wt.h. rubber 2.0 2.0 8.0 14.0 14.0 2.0 Modifier fading (“+” - yes, “-” - no) - - - - - +

The claimed invention allows to increase the heat resistance of rubbers when exposed to air and elevated temperatures, estimated by the aging coefficients in tensile strength and elongation at break;

for the claimed invention, in the form described in the independent clause of the claims below, the possibility of its implementation using the means and methods described above or known prior to the priority date is confirmed;

means that embody the claimed invention in its implementation, is able to ensure the achievement of the perceived by the applicant technical result.

Therefore, the claimed invention meets the requirement of "industrial applicability" under applicable law.

Claims (1)

A method of modifying rubbers based on ethylene-propylene rubber, comprising introducing a modifying additive into the composition of the rubber composition and subsequent vulcanization, characterized in that as the modifying additive using the previously obtained modified rubber crumb in an amount of 20-40 wt.h. per 100 parts by weight rubber of the following composition, parts by weight:
rubber SKEPT-40 one hundred sulfur 2 zinc oxide 5 tiuram D 0.75 altax 0.5 dithiodimorpholine 1,5 stearin one triethanolamine 2 Aerosil A-175 thirty carbon black K-354 2 BNI carbamate antioxidant 8-340