JPS5871934A - Stabilized synthetic rubber composition - Google Patents

Abstract

PURPOSE:To obtain titled composition of outstanding heat discoloration resistance, provided with thermal and oxidative stability, by incorporating a synthetic rubber with a specific phenolic compound. CONSTITUTION:The objective composition can be obtained by incorporating (A) 100pts.wt. of a synthetic rubber (e.g., a polybutadiene rubber manufactured by solution polymerization) with (B) pref. 0.3-1.5pts.wt. by a phenolic compound of formulaI(n=2-9; m=0 or 1; A is a group of formula II; R is 1-4C alkyl). The compound (B) (m=0) can be prepared, for example, by the reaction between a phenol of formula III and 3,3'-thiodipropionic acid (lower alkyl ester).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to synthetic rubber compositions having excellent thermal and oxidative stability.

Synthetic rubber deteriorates due to the effects of heat and oxygen during manufacturing, storage, processing, or use, and its physical properties may deteriorate significantly with phenomena such as discoloration, softening, gelation, changes in Mooney viscosity, or odor. well known.

In order to prevent such a phenomenon, various phenol-based, phosphorus-based, sulfur-based, and other antioxidants have been added singly or in combination during the production and processing steps of synthetic rubber.

For example, styrenated phenol, 2,6-di-t-butyl-
4-methylphenol, n-octadecyl-β-(8,
5-di-t-butyl-4-hydrodiphenyl) flobionate, pentaerythritol-tetrakis [β-(
Phenolic antioxidants such as 8,6-di-t-butyl-4-hy10xyphenyl) flobionate are used alone, or these phenolic antioxidants and tris(
(nonylphenyl) phosphite, distearylpentaerythritol diphosphite, etc., or the above phenolic antioxidants and sulfur such as dilaurylthiodipropionate, dilaurylthiodipropionate, etc. A method of using a combination of antioxidants and other antioxidants is known. However, these methods are still not fully satisfactory in terms of thermal and oxidative stability, heat discoloration resistance, evaporation resistance, etc. 6 The present inventors have conducted various studies to solve these problems, and have developed a specific method. The present inventors have discovered that by blending a phenolic compound into a synthetic rubber, the rubber has extremely superior heat and oxidation stability and excellent thermal discoloration resistance compared to conventional techniques, and has thus arrived at the present invention.

That is, the present invention has the following formula: m = general formula fI) A -178-(-CH2)n〒S-A (1) (wherein, n represents an integer from 2 to 9 and -m is 0 or 1. represents (3) od o-C-CH,, CH2-A, where R represents an alkyl group having 1 to 4 carbon atoms. The purpose of the present invention is to provide a synthetic rubber composition in which the

In the above general formula fI) compound used in the present invention,
R represents an alkyl group having 1 to 4 carbon atoms, and from the viewpoint of performance as a monoxidant, a methyl group and an ethyl group are preferable, and a methyl group is particularly preferable. Further, n represents an integer of 2 to 9, but preferably 8 to 6 in terms of performance as an antioxidant.

Representative examples of the phenolic compound represented by the general formula (I') used in the present invention are shown in Table-1.

Table 1 [However, [7, R, m and n correspond to the above general formula (I)] ] (5) (4) Such a phenolic compound represented by the general formula (Il) is represented by the general formula (i[) (wherein -R is phenols and 8.8
It can be produced by reacting '-thiodipropionic acid, its lower alkyl ester, or its acid chloride 1 by a known method.

In addition, when m = l in the general formula ([), the phenolic compound is a phenol monoacrylate represented by the general formula (■) ft R (wherein -R has the same meaning as above) and the following (6). It can be produced by reacting with a dithiol represented by the general formula (EV) H8SCH2'YETSH (Iv) (wherein n has the same meaning as above) by a known method.

The synthetic rubber composition of the present invention has the general formula (I
), the amount of which is blended is usually 0.1 to 2 parts by weight, preferably 0.8 to 1.5 parts by weight per 100 parts by weight of synthetic rubber.
There is a weight section.

Enol-based compounds of the general formula (denoted by T>) can be added to synthetic rubber using the usual methods, such as preparing an emulsion in advance and adding it to synthetic rubber latex, or dissolving it in an appropriate organic solvent in advance. The above method of adding solution polymerized synthetic rubber to rubber cement is used, and there are no particular limitations.

Synthetic rubbers stabilized by the present invention include solution polymerized polybutadiene rubber-solution polymerized polyisoprene rubber, solution polymerized methi-1-butadiene copolymer rubber, ethylene-propylene terpolymer rubber, and isoprene-polymerized rubber. There are isobutylene copolymer rubber, emulsion polymerization styrene-butadiene copolymer rubber, emulsion polymerization acrylonitrile-butadiene copolymer rubber, etc.In particular, solution polymerization polyphtadiene rubber, solution polymerization polyisoprene rubber, solution polymerization styrene rubber, etc. This invention is effective for -butadiene copolymer rubber, etc.6 Next, the present invention will be explained in detail with reference to Reference Examples and Examples, but the present invention is not limited thereto.

Reference Example 1 (Synthesis of Compound I-1) In an 800-day flask, 4.28 f of 3,3'-thiodipropionic acid and 50 g of toluene were added. and thionyl chloride11.
After the completion of the 6 reactions, the excess thionyl chloride and toluene were distilled off under reduced pressure.

The produced 3,8'-thiodipropionic acid dichloride and 1.62 t of 2,2'-methylenebis(6-t-butyl-4-methylphenol) were dissolved in 501 toluene and kept at -10°C. Triethylamine 4.9
A toluene solution of No. 1 was added dropwise over 2 hours. After completion of the dropwise addition, triethylamine hydrochloride is filtered and the solvent is distilled off under reduced pressure to obtain a crude product 16.8F. This is recrystallized from nut, n-hexane using silica gel chromatography to obtain Compound I-1 as white crystals with a melting point of 101.5 to 108.0°C.

Elemental analysis C52H7006S (calculated value in 1 C near 5.8 coefficient (75,9), H: 8.7 coefficient (8,6) S:
Section 8.8 (8,9) Reference Example 2 (Synthesis of Compound I-5) 2.2'-methylenebis(6-
t--/thi-4-methylphenol) monoacrylate 7,98 F, 1,6-hexanedithiol 1.50
t and 50 liters of ethanol (9) were charged, and the air in the container was replaced with nitrogen. Add 0.17% of 284 sodium methoxide methanol solution to this.
was added, and the temperature was raised to allow the reaction to reflux F for about 8 hours. After the reaction is completed, the mixture is cooled to 80° C., 50 liters of chloroform is added, neutralized with dilute hydrochloric acid, washed with water, dehydrated, and then chloroform is distilled off. 2Qf of n-hexane was added to the residue and recrystallized to give white crystal compound I-5 with a melting point of 121-122°C.
．． 7f (yield: 8°) was obtained.

Elemental analysis C58H8206S2 Calculated value C within 0:
74.084 (74,16), H:8.9([
(8,80) S: 6.87 Excellent (6,88> Example 1 Solution polymerized polybutadiene rubber containing no antioxidant (
Rubber obtained by extracting the antioxidant from JEIRBR-Ql with acetone was used.The test compound was roll-kneaded in JEIRBR-Ql and tested for thermal and oxidative stability and thermal discoloration resistance.

(10) The results are shown in Table-2.

Thermal and oxidative stability was determined by heat aging the test rubber in a gear oven at 100°C, measuring the gel content (toluene insoluble content) every 15 hours, and calculating the time required for the gel content to reach l Q wt4 ( Ge1I, P.

).

In addition, heat discoloration resistance is 15% in a gear oven at 100°C.
The rubber hue after heat aging for 60 hours and 120 hours was evaluated. In the table, AO-1 to AO-7 indicate the following compounds.

AO-1 Styrenated phenol AO-2 2,6-di-tert-butyl-4-methylphenol AO-3n-octadecyl-β-(8゜5-di-butyl-4-hydroxyphenyl)furopionate AO-4 Penta Erythritol-tetrakis [β-(8
,5-di-t-butyl-4-hydroxyphenyl)propionate] AQ-5 Tris(nonylphenyl)phosphite AO-6 Distearylpentaerythritol diphosphite A O-7 Dilaurylthione propionate Table 2 (1) Addition amount (PHR) and test results (13) Table-2 (3) Addition-! t(PHR) and test results (15) (14) Example 2 Solution polymerized polyisoprene rubber containing no antioxidant (
M) A test compound was added to a 5% toluene solution using a rubber obtained by extracting the antioxidant from JSR Engineering R-2200 using acetonol, and after stirring to make a homogeneous solution, the toluene was removed, and the test rubber was used. , thermal and oxidative stability, and thermal discoloration resistance were tested.

The results are shown in Table-3.

Thermal and oxidative stability was determined by heat aging the sample rubber in a 70C gear oven for 7 days, measuring the plasticity using a Wallace Labid plastimometer, and calculating the plasticity retention rate (PH1) using the following formula. It was evaluated.

Further, heat discoloration resistance was evaluated by the rubber hue after heat aging for 7 days in a gear oven at -70°C.

(16) Table-3 (1) Addition amount (PHR) and test results

Claims (1)

[Claims] A stabilized synthetic rubber composition A (-S (-CH2 = field S -A (In the formula, n represents an integer of 2 to 9, m is O or 1, A represents] 1 R , where R represents an alkyl group having 1 to 4 carbon atoms.)