JPH032184B2 - - Google Patents

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 action 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 manufacturing and processing steps of synthetic rubber. For example, styrenated phenol, 2,6-di-
t-Butyl-4-methylphenol, n-octadecyl-β-(3,5-di-t-butyl-4-hydroxyphenyl) propionate, pentaerythritol-tetrakis [β-(3,5-di-t
-Butyl-4-hydroxyphenyl)propionate] or other phenolic antioxidants may be used alone, or these phenolic antioxidants may be combined with phosphorus oxidants such as tris(nonylphenyl)phosphite or distearylpentaerythritol diphosphite. Methods are known in which the antioxidant is used in combination with an antioxidant, or the above-mentioned phenolic antioxidant is used in combination with a sulfur-based antioxidant such as dilaurylthiodipropionate or distearylthiodipropionate. However, these methods are still not fully satisfactory in terms of thermal and oxidative stability, thermal discoloration resistance, evaporation resistance, etc. As a result of various studies aimed at solving these problems, the present inventors have found that by blending a specific phenol compound and a specific sulfur compound into synthetic rubber, we can overcome the conventional combination technology of antioxidants. It has been found that a surprising and unexpected synergistic effect can be obtained, and more surprisingly, it has been found that the present invention has extremely superior thermal and oxidative stability and extremely excellent heat discoloration resistance compared to the conventional technology. I've reached it. That is, the present invention provides synthetic rubber with tris[2-
(2-Methyl-4-t-butyl-5-hydroxyphenyl)acetyloxy]ethyl isocyanurate [compound ()] and general formula (In the formula, R represents an alkyl group having 4 to 20 carbon atoms.) A sulfur-based compound [compound ()] represented by
():()=2:1 to 20 (weight ratio) A stabilized synthetic rubber composition is provided. In the sulfur-based compound represented by the above general formula used in the present invention, the substituent R represents an alkyl group having 4 to 20 carbon atoms, but is preferably an alkyl group having 6 to 18 carbon atoms in terms of thermal and oxidative stability. In particular, an alkyl group having 12 carbon atoms is most preferred. Examples of such sulfur-based compounds include pentaerythritol-tetrakis (β-hexylthiopropionate) and pentaerythritol-tetrakis (β-hexylthiopropionate).
dodecylthiopropionate), pentaerythritol-tetrakis (β-octadecylthiopropionate), and the like. In the synthetic rubber composition of the present invention, the total amount of compound () and compound () added is usually 0.1 to 2 parts by weight, preferably 0.3 to 1.5 parts by weight, based on 100 parts by weight of synthetic rubber. Also, the compound ()
The weight ratio of compound (2) to compound (2) is usually 1 to 20, particularly preferably 2 to 10. In the present invention, the compound () and the compound () can be added to the synthetic rubber by a conventional method, for example, by preparing an emulsion in advance and adding it to the synthetic rubber latex, or by dissolving it in a suitable organic solvent in advance and then adding it to the synthetic rubber latex. A method of adding polymerized synthetic rubber to rubber cement can be used, and there are no particular restrictions. The synthetic rubber stabilized by the present invention includes:
Solution polymerized polybutadiene rubber, solution polymerized polyisoprene rubber, solution polymerized styrene-butadiene copolymer rubber, ethylene-propylene ternary copolymer rubber, isoprene-isobutylene copolymer rubber, emulsion polymerized styrene-butadiene copolymer rubber, emulsified Examples include polymerized acrylonitrile-butadiene copolymer rubber, and are particularly effective for solution-polymerized polybutadiene rubber, solution-polymerized polyisoprene rubber, and solution-polymerized styrene-butadiene rubber. 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 Tris [2-(2-methyl-4-t-butyl-
Synthesis of 5-hydroxyphenyl)acetyloxy]ethyl isocyanurate 2-methyl-4-t-
Butyl-5-hydroxyphenylacetic acid 76.6g, tris(2-hydroxyethyl)isocyanurate
30.0 g of toluene, 0.9 g of toluene, and 3.0 g of p-toluenesulfonic acid were charged and heated under reflux in a nitrogen stream for about 10 hours, and the water produced by the reaction was removed from the system by azeotropic distillation. After the reaction is complete, the mixture is neutralized with an aqueous solution of sodium carbonate, washed with water, dehydrated, and then toluene is distilled off under reduced pressure to obtain pale yellow tris[2-(2-methyl-4-t-butyl-5-hydroxyphenate). enyl)acetyloxy]ethyl isocyanurate 93g (yield
93%). This product was recrystallized from n-heptane to obtain white crystals with a mp of 84-86°C. Elemental analysis value (as C ₄₈ H ₆₃ N ₃ O ₁₂ ) C (%) H (%) N (%) Calculated value 66.0 7.3 4.8 Measured value 66.3 7.5 4.7 ¹ H-NMR CDCl ₃ δ (ppm) 1.62 (9H, s), 2.16 (3H, s), 3.48 (2H,
s), 4.20 (2H, m), 4.27 (2H, m), 5.86 (1H,
s), 6.49 (1H, s), 6.97 (1H, s) Example 1 Solution-polymerized polybutadiene rubber containing no antioxidant (rubber obtained by extracting the antioxidant from JSR BR-01 with acetone was used) The test compounds shown in Table 1 were roll-kneaded and used as test rubbers, and tests were conducted on thermal and oxidation stability and heat discoloration resistance. The results are shown in Table-1. The thermal and oxidation stability of the sample rubber is 100%.
The gel content (toluene insoluble content) was measured every 15 hours after heat aging in a gear oven at °C, and the evaluation was based on the time it took for the gel content to reach 10% by weight (referred to as Gel IP). In addition, heat discoloration resistance was evaluated by rubber hue after heat aging in a gear oven at 100°C for 15 hours, 60 hours, and 120 hours. In addition, the symbols of the test compounds in the table indicate the following compounds. Tris[2-(2-methyl-4-t-
Butyl-5-hydroxyphenyl)acetyloxy]ethyl isocyanurate -1 Pentaerythritol-tetrakis (β-hexylthiopropionate) -2 Pentaerythritol-tetrakis (β-dodecylthiopropionate) AO-12,6-di -t-butyl-4-methylphenol AO-2n-octadecyl-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate AO-3pentaerythritol-tetrakis [β-(3,5- Di-t-butyl-4
-Hydroxyphenyl)propionate] AO-4 Dilaurylthiodipropionate AO-5 Tris(nonylphenyl)phosphite

【table】

[Table] Example 2 The materials shown in Table 2 were added to a 5% by weight toluene solution of solution-polymerized polyisoprene rubber containing no antioxidant (rubber obtained by extracting the antioxidant from JSR IR-2200 with acetone). The test compound (the meaning of the symbol is the same as that described in Example 1) was added, stirred to make a homogeneous solution, and the toluene was removed. I conducted a test. The results are shown in Table-2. Thermal and oxidation stability of the test rubber was measured at 70°C.
After heat aging in a gear oven for 7 days, the plasticity was measured using a Wallace Rapid Plastimometer, and the plasticity retention rate (PRI) was determined and evaluated using the following formula. PRI (%) = Plasticity after heat aging / Plasticity before heat aging x 1
00 Heat discoloration resistance was evaluated by the rubber hue after heat aging for 7 days in a gear oven at 70°C.

【table】

【table】

Claims (1)

[Scope of Claims] 1 Tris [2-(2-methyl-4-
t-Butyl-5-hydroxyphenyl)acetyloxy]ethyl isocyanurate [compound ()]
and general formula (In the formula, R represents an alkyl group having 4 to 20 carbon atoms.) A sulfur-based compound [compound ()] represented by
1. A stabilized synthetic rubber composition characterized by having a ratio of ():()=2:1 to 20 (weight ratio).