CS235193B1 - Stabilization composition for vulcanizates - Google Patents

Description

The invention relates to a stabilizing composition for vulcanizates of natural and / or synthetic rubbers comprising α-methylbenzyldiphenylamine, n-methylbenzylphenol, 2-mercaptobenzimidazole.

The need for high thermo-oxidative stability of vulcanizates from natural and / or synthetic rubbers, while maintaining their lightfastness, is currently being addressed by the use of antidegradants, in particular from the phenol group. More nuclear phenol derivatives are most effective. However, despite the high stabilizing activity of these compounds, their use is limited by limited availability. A more viable way to achieve improved thermo-oxidative stability of the vulcanizates and thus product durability is to utilize the synergistic effect of some stabilizer mixtures. For example, Cs. AO 165 480 is a protected combination of aralkylphenol and 2-mercaptobenzimidazole.

In addition, good workability and solid shelf life are required from the additive, as the current requirements for work hygiene and trouble-free product handling are increasing.

The aforementioned claims are based on a stabilizing composition for the vulcanizates of natural and / or synthetic sulfonates based on N-methylbenzylphenol and 2-mercaptobenzimidazole according to the invention.

The stabilizing composition comprises 30 to 65 wt. N-methylbenzyldiphenylamine of formula I.

(ll) in which:

R is hydrogen or α-methylbenzyl and n is an integer of 1 to 3 and 15 to 40% 15 to 35% ihmot. of α-methylbenzylphenol of formula II.

(II) wherein n is an integer of 1 to 3 and 15 to 40% by weight of the composition; 2-mercaptobenzimidazole of formula III

It has also been found that the stabilizing composition can be treated with a suitable inert filler (e.g. hydrated silica) containing 40 to 70% by weight of the composition. of the active substance.

Furthermore, it has been found that the stabilizer mixture so treated can be added to the rubber mixture in an amount of 0.5 to 5.0 wt. preferably 1.0 to 3.0 wt. parts per 100 wt. d ..Ίοv rubber.

The stabilizing composition is used in conjunction with conventional vulcanization accelerators, such as guanidines, thiazoles, thiuranes, ditocarbamates, thiourea derivatives, and the like.

The use of the stabilizing composition of the invention has many advantages. As a solid and, moreover, in a non-dusting treatment, semi-automatic or fully automatic weighing can be used to prepare the raw rubber mixtures, which substantially improves the hygiene of the working environment.

Since the stabilizing composition of the present invention exhibits higher antioxidant effects than the binary combination used earlier and substantially higher than the components alone, vulcanizates with increased resistance to thermo-oxidative aging are obtained by its application.

From a practical point of view, it is possible to prepare a mixed stabilizer, together with an inert carrier, in powder form and in a non-dusting treatment, which is substantially more effective than the binary combination or bisphenols mentioned above.

The stabilizer composition alone, optionally with an additional antidegradent, is formulated into the rubber mixture by conventional processing procedures as other additives.

The properties of the raw mixtures and vulcanizates have been observed and evaluated by conventional tests used in rubber and rubber technology.

The following examples illustrate the invention.

Example 1

Natural rubber vulcanizate according to the following recipe:

natural rubber, species SMR-L 100 wt. light mineral filler 60 wt. sour. titanium 10 wt. sour. zinc 10 wt. stearic acid 1 wt. sulfur 2.5 wt. N-cyclohexyl-2-Benzothiazol sulphenamide 0.5 wt.

parts by parts parts by parts parts by parts and each containing 2.0 parts by weight of antidegradant was prepared by pressing to the optimum at 145 ° C.

The vulcanization characteristics of the raw mixtures, which were monitored according to the MONSANTO methodology at 145 ° C, were not affected by the addition of the stabilizer composition.

The aging of the vulcanizates was monitored on the basis of a change in the basic physical-mechanical properties, such as modulus 300 ° / o, tensile strength, elongation, etc., after aging in hot air at 90 ° C by the tube aging method according to GEER. 62 15 21) for 1, 3, 5 days.

The results obtained are summarized in the table in the form of the dependence of the change in strength versus aging time (tensile strength is a critical factor in the aging of natural rubber - it changes most during aging). Stabilization system (parts by weight per 100 parts by weight of rubber

a-metylbenzyldifenylamín 1.2 2-mercaptobenzimidazole 0.8 a-metylbenzyldifenylamín 1.0 2-mercaptobenzimidazole 1.0 2-mercaptobenzimidazole 2.0 α-methylbenzyl diphenylamine 2.0 a-metylbenzyldifenylamín 0.8 2-mercaptobenzimidazole 0.6 a-metylbenzylfenol 0.6 a-metylbenzyldifenylamín 0.6 2-mekraptobenzimidazol 0.8 a-metylbenzylfenol 0.6 a-metylbenzyldifenylamín 1.2 2-mercaptobenzimidazole 0.4 a-metylbenzylfenol 0.4

Efficiency of stabilization systems, expressed as tensile strength after aging at 90 ° C

Para- Stabilization system meter - 1 234567

Table no. 1 residual strength after aging (%)

1 day 55 84 86 3 days 21 70 72 5 days 10 52 52

The stabilizing system comprising the stabilizing compositions according to the invention is at the same time the most effective as it also represents the economically disadvantageous combination of the individual components.

A practical use of the above results is a mixed stabilizer in powder form and a non-dusting treatment, prepared on the basis of a combination of stabilizers according to the formulas (Ij to (III)), introduced at the beginning:

37.5% by weight of α-methylbenzyldiphenylamine

12.5% by weight of N-mercaptobenzimidazole

12.5% by weight of α-methylbenzylphenol

37.5% hydrated acid. silica

80 83 85 84 90 61 53 74 70 76 38 29 56 47 58

Example 2

The stabilizing composition shown at the end of Example 1, consisting of a composition of the invention, added at a concentration of 1.5 parts by weight to the formulation of Example 1, protects the vulcanizate more effectively than a binary combination antidegradant stabilizer and is equal to bisenenol.

Stabilization system

8. 2,2‘-methylene-bis (4-methyl, 6-tert-butylphenol)

9. A mixed stabilizer consisting of 49 weight percent aralkylated phenol, 21 weight percent 2-mercaptobenzimidazole with 30 weight percent inert acid. silica

10. A stabilizing composition, the composition of which is given at the end of Example 1

Table no. 2

Physical-mechanical properties of vulcanizates after aging, GEER 90 ° C

parameter

Stabilization system

9 10

residual strength (° / o) 1 day 55 3 days 21 5 days 10 dynamic fatigue by de Mattia (ke) 29.5 after aging for 7 days 70 ° C / kc 18.1

92 77 91 89 46 84 65 40 67 52.5 46.3 61.4 27.6 24.7 47.2

A vulcanizate containing the said stabilizing agent. the composition, with the degree of coloration acquired after exposure to a UV source, radiation does not distinguish from the degree of coloration of the unprotected vulcanizate, while at the same time preventing the formation of a "crazing effect".

Example 3

Chloroprene rubber vulcanizate according to the recipe:

mass, parts

chloroprene rubber, type WRT 100 magnesium oxide 4 zinc oxide 5 titanium dioxide 10 kaolin 90 paraffin 3 diethylene thiourea 1.0 2,2 dibenztiazoldisulfid 0.5

3 19 and containing in each case 2.5 parts by weight of a stabilizer, was prepared by pressing to the optimum at 160 ° C.

Stabilization system used

11. 4,4‘-Thiobis (6-tert-butyl, 3-methylphenol)

12. Mixed stabilizer consisting of 49% by weight of aralkylated phenol, 21% by weight of 2-mercaptobenzimidazole and 30% by weight of inert acid. silica

13. A composition according to the invention at the end of Example 1

Table no. 3

Properties of vulcanizates containing barbecue stabilized systems

Parameter Stabilization system - 11 12 13 residual elongation (%) exposure 120 ° C

1 day 39 82 80 87 3 days 10 69 56 78 5 days 7 43 35 73 dyn. stage fatigue de Mattia 3.2 7.5 9.9 16.8 7 days (70 ° C / kcj 2.9 4.5 4.4 11.3

The vulcanizate containing the subject weakly does not differ from the degree of coloring of the unprotected composition, with the degree of coloring of the vulcanizate.

Claims (2)

SUBJECT We claim: Compressing composition for vulcanizates of natural and / or synthetic rubbers based on .alpha.-methylbenzylphenol and 2-mercaptobenzimidazole, characterized in that it contains 30 to 65% by weight of .alpha.-methylbenzyldiphenylamine of the formula I CH - <O I CH, n II) L-3 (II) wherein n is an integer of 1 to 3, and 15 to 40% by weight of 2-mercaptobenzimidazole of formula III wherein n is an integer of 1 or 2 and R is hydrogen or α-methylbenzyl, 15 to 35% by weight of α-methylbenzylphenol of formula II C ~ SH Severography, n. p., plant 7, Most