RU2236423C1 - Curable rubber compound - Google Patents

Abstract

FIELD: rubber industry.

SUBSTANCE: rubber compound is prepared from unsaturated rubber, vulcanization substance, filler, and other ingredients. Rubber compound is further supplemented by 0.5 to 5.0 wt parts (per 100 wt parts rubber) of antiaging agent composed of liquid alloy of antiaging agents prepared at 70-90^оС at following proportions of components, wt parts: N-isopropyl-N-phenyl-p-phenylenediamine 35-40, N,N'-diphenyl-p-phenylenediamine 10-24, 2-mercaptobenzothiazole 6-10, ε-caprolactam 35-40, and powder carrier in amount 50-85 wt parts per 15-50 wt parts of alloy of antiaging agents.

EFFECT: increased heat-oxidative resistance of rubbers.

6 tbl, 6 ex

Description

The invention relates to the production of a vulcanizable rubber composition, the vulcanizates based on which have increased resistance to thermo-oxidative aging. The invention can be used in the tire and rubber industry to obtain vulcanizates with long-term resistance to thermo-oxidative aging.

Known vulcanizable rubber compounds based on unsaturated rubbers stabilized by N-isopropyl-N-phenyl-n-phenylenediamine (Koshelev F.F. et al. General technology of rubber, ed. "Chemistry", M., 1968, p.174).

The disadvantage of rubber mixtures using N-isopropyl-N-phenyl-n-phenylenediamine as a stabilizer is the short protection of the vulcanizates based on them from thermooxidative aging, since the stabilizer is characterized by unproductive consumption due to high diffusion activity, which leads to evaporation and leaching from the surface of the vulcanizates (Rubber and rubber No. 2, 2001, p. 26-31).

Rubber mixtures are also known in which a complex antioxidant, obtained by mixing smectin clay with a mixture of a quaternary amine, a polar solvent and an antiozonant, is introduced as a rubber additive to inhibit ozonation. An expanded organic derivative of clay and a quaternary amine is obtained with which the antiozonant is bound in a complex compound (US Patent No. 4,532,285, MKI C 08 K 009/04, 07/30/85).

The disadvantage of the invention is the use of a solvent, the use of which complicates the technological scheme for producing a complex antioxidant, since it is necessary to purify the resulting product from the solvent and recover the latter. All this leads to additional economic costs and is environmentally unsafe.

A known rubber mixture containing powdered stabilizers (Rubber and rubber No. 2, 1985, p. 7-8), obtained by mixing liquid and resin-like stabilizers of the phenolic type (agidol 20, agidol 123) with a solid-phase carrier (colloidal silicas, kaolin, chalk).

The disadvantage of such rubber compounds is the low stabilizing activity of the powder stabilizers in protecting the rubber from thermo-oxidative aging. This is a consequence of the fact that phenolic type antioxidants are inferior to amine type antioxidants in their protective effect.

Closest to the claimed vulcanizable rubber compound may be rubber compounds containing amine type liquid antioxidants, for example N-alkyl-N-phenylenediamine-1,4 (diaphen FA) (“Chemical additives to polymers” Handbook edited by IP Maslova , “Chemistry”, 1981, p.26-27).

However, in this case too, rubber mixtures cannot provide effective protection to their vulcanizates, since their stabilizers participate in protection by only one mechanism - the breakdown of the oxidation chain, without ensuring the possibility of the breakdown of polymer hydroperoxides (there is no preemptive protection mechanism).

Obtaining a vulcanizable rubber composition containing an antioxidant providing a high level of thermo-oxidative stability of vulcanizates is the problem to which this invention is directed.

The technical result is to increase the thermal oxidative stability of vulcanizates.

The technical result is achieved by using in the composition of the vulcanizable rubber composition based on unsaturated rubbers a composite antioxidant in an amount of 0.5-5 wt.h. per 100 parts by weight rubber, consisting of a liquid alloy of antioxidants obtained at a temperature of 70-90 ° C in the following ratio of components, wt.h .:

N-isopropyl-N-phenyl-N-phenylenediamine 35.00 - 40.00

N, N’-diphenyl-N-phenylenediamine 10.00 - 24.00

2-mercaptobenzthiazole 6.00 - 10.00

ε-caprolactam 35.00 - 40.00

and a powdered carrier, and the ratio of the alloy of antioxidants and the powdered carrier is, wt.h .:

Antioxidant Alloy 15.00 - 50.00

Powdered carrier 50.00 - 85.00

Mineral, synthetic fillers, for example, colloidal silicic acids (BS-100, BS-120), kaolin, chalk can be used as a carrier.

Vulcanizates based on the proposed vulcanizable rubber composition containing a composite antioxidant, which consists of an antioxidant alloy acting according to the chain breaking mechanism and preventing the growth of the oxidation chain, as well as a carrier on the surface of which the antioxidant alloy is adsorbed, do not undergo thermal oxidative aging for a long time. Vulcanizates based on the proposed rubber mixture containing a composite antioxidant are effectively protected from thermal oxidative aging not only due to the synergistic action of antioxidants, but also have long-term protection due to adsorption on the surface of the carrier alloys of antioxidants, reducing their diffusion to the surface of the vulcanizates, resulting in reduced unproductive antioxidant consumption.

When the content of the ingredients of the composite antioxidant is selected, the alloys under normal conditions are viscous liquids (Brookfield viscosity at 25 ° C not more than 3000 cPs), which allows the alloys to be deposited on a carrier in the absence of solvents.

The use of the proposed dosage method of N-isopropyl-N phenyl-n-phenylenediamine (diaphen AF) in a ratio of less than 35.00 wt.h. the product is less effective in protecting against thermo-oxidative aging. When the content of diafen AF more than 40.00 wt.h. alloys under normal conditions are in the solid state. In this case, preliminary melting of these alloys is required during deposition on carriers, which leads to an increase in the cost of the product without increasing its efficiency.

An increase in the dosage of N, N’-diphenyl-n-phenylenediamine (diaphen FF) in the alloy over 24.00 wt.h. leads to a decrease in the content of diaphen AF and / or captax, which reduces the effectiveness of the protective effect of the composite antioxidant; or a decrease in the content of ε-caprolactam, which leads to the production of hard alloys. The content of FF diaphen is less than 10.00 wt.h. in the composition of the antioxidant alloy leads to an increase in the cost of the product by increasing the dosage of more expensive products that make up the alloy.

2-mercaptobenzthiazole (captax) is a stabilizer of the prophylactic type and forms synergistic systems with derivatives of n-phenylenediamines. The use of Captax in a dosage exceeding 10.00 parts by weight results in a change in the ratio of the components of the alloy, as a result of which the alloys are solid. The use of 2-mercaptobenzthialol in a dosage of less than 6.00 wt.h. the antioxidant alloy will not have a synergistic effect due to the too small dosage of the preventive type antioxidant.

The content of ε-caprolactam in the dosage range of 35.00-40.00 wt.h. provides alloys of antioxidants in the form of viscous liquids.

Powdered carriers are characterized by different adsorption capacity, therefore, for each type of carrier, the optimal dosages in the composition of the composite antioxidant are determined. So, when using colloidal silicic acid (BS-100, BS-120) as a carrier, the content of 50.00-60.00 wt.h. is optimal. as part of a composite antioxidant. This is justified by the fact that with a larger dosage of filler, dusting of the resulting product is observed, as well as a decrease in the protective effect of the composite antioxidant. At a lower dosage of colloidal silicic acid, the resulting substance is a viscous pasty product.

When using kaolin as a carrier, the optimum content in the composition of the composite antioxidant is 70.00 parts by weight. Increasing the dosage of the carrier leads to a decrease in the protective effect. Lowering the dosage of the carrier results in pasty formulations.

When used as a carrier of chalk, the content of 85.00 parts by weight is effective. Increasing the dosage of the carrier reduces the effectiveness of the composite antioxidant as a whole, using a carrier in a smaller amount results in viscous pasty products.

Composite antioxidant receive in two stages according to the scheme:

- obtaining an alloy of antioxidants is carried out in a heated reactor equipped with a mechanical stirrer of the anchor type. The ingredients of the antioxidant alloy are loaded into the reactor, melted at a temperature of 70-90 ° C and mixed until a homogeneous mixture is obtained.

- the alloy of antioxidants, a powdery carrier are loaded into the mixer (glue mixer) and mixed at a temperature of 20-90 ° C until a homogeneous powdery mass is obtained for 30-40 minutes. Product unloading is carried out in a receiving tank.

The rubber composition according to the invention contains unsaturated rubber, vulcanizing agents, a composite antioxidant and other additives.

As rubbers unsaturated rubbers can be used: natural, polyisoprene, nitrile butadiene, etc., as well as combinations thereof. Vulcanizing agents, accelerators and vulcanization activators are selected from the group: sulfur, thiurams, polysulfide accelerators, dithiocarbamates, thiazoles, sulfenamides, guanidines, as well as organic peroxides.

In addition, plasticizers, fillers, pore-forming substances, dyes and other additives can be introduced into the rubber composition.

Example 1. On the rollers in the usual way prepare a rubber mixture, the composition of which is given in table 1, 2, 3 (composition 3). As an antioxidant, a composite antioxidant is used, 100 g of which are prepared as follows: 17.50 g of N-isopropyl-N-phenyl-n-phenylenediamine are loaded into a stirred reactor at a temperature of 70-90 ° C; 12.00 g of N, N’-diphenyl-n-phenylenediamine; 17.50 g of ε-caprolactam; 3.00 g of 2-mercaptobenzthiazole, mixing is carried out until a homogeneous mixture is obtained. Then gradually, for example, over 3 minutes, 50.00 g of colloidal silicic acid (BS-100 or BS-120) are added, constantly stirring. The ratio of the alloy of antioxidants - powder carrier is 50% -50%. After the loading of colloidal silicic acid is completed, the composite mixture in the reactor is continued to mix for 30-40 minutes. The resulting composite antioxidant is discharged into a receiving container, then introduced into the rubber mixture at the dosage indicated in the rubber compounding.

According to the proposed example receive a rubber mixture containing a powdery composite antioxidant.

Example 2. Analogously to example 1, with the difference that 10.50 g of N-isopropyl-N-phenyl-n-phenylenediamine are charged into the reactor; 7.20 g of N, N’-diphenyl-n-phenylenediamine; 10.50 g of ε-caprolactam; 1.80 g of 2-mercaptobenzial, and 70.00 g of kaolin is charged as a carrier. The ratio of the alloy of antioxidants - powder carrier is 30% -70%. The composition of the rubber mixture is given in table 1, 2, 3 (composition 4).

Example 3. Analogously to example 1, with the difference that 5.25 g of N-isopropyl-N-phenyl-n-phenylenediamine are charged into the reactor; 3.60 g of N, N’-diphenyl-n-phenylenediamine; 5.25 g of ε-caprolactam, 0.90 g of 2-mercaptobenzial, and 85.00 g of chalk is loaded as a carrier. The ratio of the alloy of antioxidants - powder carrier is 15% -85%. The composition of the rubber mixture is given in table 1, 2, 3 (composition 5).

Example 4. Analogously to example 1, with the difference that 20.00 g of N-isopropyl-N-phenyl-n-phenylenediamine are charged into the reactor; 5.00 g of N, N’-diphenyl-n-phenylenediamine; 20.00 g of ε-caprolactam; 5.00 g of 2-mercaptobenzial. The ratio of the alloy of antioxidants - powder carrier is 50% -50%. The composition of the rubber mixture is given in table 1, 2, 3 (composition 6).

Example 5. Analogously to example 2, with the difference that 12.00 g of N-isopropyl-N-phenyl-n-phenylenediamine, 3.00 g of N, N’-diphenyl-N-phenylenediamine are charged into the reactor; 12.00 g of ε-caprolactam; 3.00 g of 2-mercaptobenzthial. The ratio of the antioxidant alloy of the powdered carrier is 30% -70%. The composition of the rubber mixture is given in table 1, 2, 3 (composition 7).

Example 6. Analogously to example 3, with the difference that 6.00 g of N-isopropyl-N-phenyl-n-phenylenediamine are loaded into the reactor; 1.50 g of N, N’-diphenyl-n-phenylenediamine; 6.00 g of ε-caprolactam; 1.50 g of 2-mercaptobenzial. The ratio of the antioxidant alloy of the powdered carrier is 30% -70%. The composition of the rubber mixture is given in table 1, 2, 3 (composition 8).

For comparison, rubber mixtures were prepared containing the traditionally used antioxidant diafen FP (composition 1 in Tables 1, 2, 3), as well as diafen FA (prototype) deposited on a carrier (white carbon black BS-100), deposition was carried out according to a known deposition technique (Rubber and rubber No. 2, 1985, pp. 7-8) (composition 2 in Tables 1, 2, 3).

Known and proposed rubber compounds are prepared according to the standard mode, vulcanized in a press with electric heating at a temperature of 143 ° C in optimum.

From the results of physical and mechanical tests given in Table 4, it follows that rubber compounds containing a composite antioxidant to a lesser extent lose strength properties in the process of thermo-oxidative aging than rubber compounds containing FA diaphene or FA diaphene (prototype) deposited on a carrier.

So in vulcanizates containing composite antioxidants (example 1-6), there is no drop in conditional strength at the first stages of thermo-oxidative aging (48 h), i.e. the change in the indicator in this case is 0%, while in vulcanizates containing FA as a antioxidant (prototype) deposited on a carrier, the drop in conditional strength under the same conditions of thermo-oxidative aging is 4%. At further stages of thermo-oxidative aging (76-92 h), a smaller drop in the conditional strength index in the presence of a composite antioxidant is also observed, ranging from 5 to 17%, and for vulcanizates containing FA diaphene deposited on a carrier (prototype), the conditional strength index decreases 15 to 25%.

Volcanizates based on isoprene rubber containing a composite antioxidant are also less susceptible to thermooxidative aging than vulcanizates containing an antioxidant according to the prototype or the traditionally used diafen FP, as shown in the data presented in Table 5

Vulcanizates based on nitrile butadiene rubber are subjected to structuring during thermooxidative aging; their ineffective protection leads to a decrease in elongation. The proposed composite antioxidants to a greater extent protect nitrile rubbers from oxidizing factors, which, as follows from the data presented in table 6, is expressed in a longer preservation of relative elongation.

The use of a composite antioxidant in the vulcanizable rubber composition provides the vulcanizates with long-term protection against thermo-oxidative aging.

Claims (1)

Vulcanizable rubber mixture, including unsaturated rubber and antioxidant, characterized in that as the antioxidant use a composite antioxidant in an amount of 0.5-5 wt.h. per 100 parts by weight rubber, consisting of a liquid alloy of antioxidants obtained at a temperature of 70-90 ° C, in the following ratio of components, parts by weight: N-Isopropyl-N-phenyl-n-phenylenediamine 35.00-40.00 N, N'-Diphenyl-n-phenylenediamine 10.00-24.00 2-Mercaptobenzthiazole 6.00-10.00 ε-caprolactam 35.00-40.00 and a powdered carrier, and the ratio of the alloy of antioxidants and powdered carrier is, wt.h .: Antioxidant Alloy 15.00-50.00 Powdered carrier 50.00-85.00