JPH10176081A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition reduced in migration, lowered in the dependence of viscosity on temperature and improved in the processability when vulcanizing. SOLUTION: This composition is obtained by compounding 100 pts.wt. rubber with (1) <=50 pts.wt. polydimethylsiloxane containing co-vulcanizable sulfur or (2) <=50 pts.wt. silanol-ended polydimethylsiloxane, <=10 pts.wt. co-vulcanizable sulfur-containing silane coupling agent and <=10 pts.wt. silanol condensation catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition which has no migration (migration) of a plasticizer or the like, has a low modulus, and has improved processability.

[0002]

2. Description of the Related Art Plasticizers are generally used in products made of many rubber compositions. However, these plasticizers migrate with the passage of time, and therefore have a problem that the performance of the products changes over time. Was. To solve such a problem, it is conventionally known to add a liquid IR or BR, but such a substance migrates considerably without being necessarily co-crosslinked. Further, since these are polymers, they have high temperature dependence of viscosity and are not preferable as plasticizers.

[0003]

Therefore, in the present invention,
By compounding a rubber with a silicone that has a low temperature dependence of viscosity and incorporating a co-vulcanizable functional group into the rubber, it gives a soft rubber cured product that does not migrate and is low in temperature, and also has good processability when unvulcanized. It is an object of the present invention to provide a rubber composition in which is further improved.

[0004]

According to the present invention, a rubber 1 is provided.
There is provided a rubber composition comprising 50 parts by weight or less of polydimethylsiloxane containing sulfur which can be co-vulcanized with respect to 00 parts by weight.

Further, according to the present invention, silanol-terminated polydimethylsiloxane is added to 100 parts by weight of rubber.
0 parts by weight or less, 10 parts by weight or less of a co-vulcanizable sulfur-containing silane coupling agent, and 1 part of a silanol condensation catalyst.
There is provided a rubber composition blended in an amount of 0 part by weight or less.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration, operation and effect of the present invention will be described below. The co-vulcanizable sulfur-containing polydimethylsiloxane used in the first invention of the present application is a polydimethylsiloxane having an SH group or a polysulfide group in its molecule, and is represented by the following general formula: Are effectively used.

[0007]

Embedded image Or

Embedded image (Wherein, R ¹ represents a divalent hydrocarbon group, R ² represents a methyl group or an ethyl group, and n represents 10 to 1000
Wherein x is 2 to 6 and R ³ represents a hydrocarbon group or a hydrocarbon group containing sulfur, oxygen and nitrogen atoms. )

Specifically, a compound represented by the following formula:

Embedded image

Embedded image Alternatively, a commercially available mercapto-modified silicone (for example, X-22-167B, X-2 manufactured by Shin-Etsu Chemical Co., Ltd.)
2-980).

The polydimethylsiloxane used in the first invention of the present application is synthesized by reacting a silanol-terminated silicone with various silane coupling agents using divalent tin as a catalyst.

The silane coupling agent is represented by the following formula:

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Embedded image Can be exemplified.

The compounding amount of the polydimethylsiloxane used in the first invention of the present application is 50 parts by weight or less, preferably 5 to 30 parts by weight based on 100 parts by weight of rubber. If the blending amount of the polydimethylsiloxane is too small, the desired effect cannot be obtained, while if it is too large, there is a problem in performance as a rubber, which is not preferable.

The silanol-terminated polydimethylsiloxane used in the second invention of the present application is a polydimethylsiloxane represented by the following formula:

Embedded image However, as the co-vulcanizable sulfur-containing silane coupling agent, the above-described sulfur-containing silane coupling agent is used,
Further, as the silanol condensation catalyst, a titanium chelate catalyst, a divalent tin compound, an amine catalyst, and the like, specifically,
Titanium acetyl acetate, tin octylate, laurylamine are used.

The amount of the silanol-terminated polydimethylsiloxane used in the second invention of the present application is 50 parts by weight or less, preferably 5 to 5 parts by weight, per 100 parts by weight of rubber.
30 parts by weight, and the compounding amount of the co-vulcanizable sulfur-containing silane coupling agent is 1 to 100 parts by weight of rubber.
0 parts by weight or less, preferably 8 parts by weight or less, most preferably 1 to 8 parts by weight, and the compounding amount of the silanol condensation catalyst is 10 parts by weight or less, preferably 0.1 part by weight with respect to 100 parts by weight of rubber. 1 to 5 parts by weight. Since the reaction products of these three components have a required effect on the rubber composition, the amount of the silanol-terminated polydimethylsiloxane is first set to a predetermined amount, and the other two components are added. It is preferred that the amounts of the components are stoichiometrically determined so that there is no excess or deficiency.

The respective components in the second invention of the present application are separately added and kneaded during kneading of the rubber composition. These components are kneaded and reacted in another mixer in advance, and this is added to the rubber composition. A method of adding and kneading to the mixture may be employed.

The rubber component blended in the rubber composition according to the present invention is a crosslinkable rubber component alone or as a mixture of two or more. As the crosslinkable rubber, any rubber can be used. For example, natural rubber (NR), various butadiene rubbers (BR), various styrene-butadiene copolymer rubbers (SBR), polyisoprene rubber (IR), Butyl rubber (IIR), acrylonitrilobutadiene rubber,
Chloroprene rubber, ethylene-isoprene copolymer rubber, ethylene-propylene-diene copolymer rubber, styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber, chlorosulfonated Polyethylene, acrylic rubber, epichlorohydrin rubber, polysulfide rubber, silicone rubber, fluorine rubber, urethane rubber, and the like can be used. When a blend is used, the blend ratio is not particularly limited.

According to the present invention, the rubber composition is compounded with any carbon black and / or silica that is usually compounded in the rubber composition. Further, the rubber composition according to the present invention further includes a normal vulcanizing or crosslinking agent, a vulcanizing or crosslinking accelerator, various oils, an antioxidant, a filler, a plasticizer,
Various additives that are generally compounded for softeners and other general rubbers can be compounded. Such a compound is kneaded and vulcanized into a composition by a general method, and vulcanized or crosslinked. Can be used for The amounts of these additives may be conventional general amounts as long as they do not contradict the purpose of the present invention.

[0017]

EXAMPLES The present invention will be described in more detail below with reference to standard examples, examples and comparative examples, but it goes without saying that the technical scope of the present invention is not limited to these examples.

The polysiloxanes 1 and 2 used in the following examples were synthesized by the following general method. Polysiloxane 1 (SH single-ended silicone) 400 g of silanol-terminated dimethylpolysiloxane (shown by the following formula (I)) was dried under reduced pressure at 90 ° C. for 2 hours, and 0.4 g of a 10% dioctyltin solution was added. 4 g of mercaptopropyltrimethoxysilane and 4 g of vinyltrimethoxysilane were added.
The reaction was carried out for 2 hours while removing methanol under reduced pressure. Thereafter, unreacted γ-mercaptopropyltrimethoxysilane and vinyltrimethoxysilane were removed at 120 ° C. under reduced pressure. The deduced structure of this compound is as follows:

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[0019]

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Polysiloxane 2 (SH double-ended silicone)
B) Silanol-terminated dimethylpolysiloxane (I) 4
After drying under reduced pressure at 90 ° C. for 2 hours, 0.4 g of a 10% dioctyltin solution was added, and then 9 g of γ-mercaptopropyltrimethoxysilane was added. Allowed to react for hours. Thereafter, unreacted γ-mercaptopropyltrimethoxysilane was removed at 120 ° C. under reduced pressure. The deduced structure of this compound is as follows:

[0021]

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The following commercially available products were used as the other components in the following standard examples, examples and comparative examples. Natural rubber: SIR-20 SBR: Nipol 1502 (Nihon Zeon) Carbon black: Seest KH (Tokai Carbon) Silica: Nipsil AQ (Nihon Silica) Silane coupling agent: Si69 (Dexa) (chemical name:
Bis- [3- (triethoxysilyl) -propyl] tetrasulfide) Antioxidant 6C: N-phenyl-N '-(1,3-dimethylbutyl) -P-phenylenediamine Vulcanization accelerator CZ: N-cyclohexyl -2-benzothiazylsulfenamide vulcanization accelerator DPG: diphenylguanidine

Preparation of Sample The vulcanization accelerator and components other than sulfur were kneaded in a 1.8 liter hermetic mixer for 3 to 5 minutes, and the vulcanization accelerator was added to the masterbatch released when the temperature reached 165 ± 5 ° C. And sulfur were kneaded with an 8-inch open roll to obtain a rubber composition. The unvulcanized physical property "Mooney viscosity" of the obtained rubber composition was measured. Next, this composition was press-vulcanized in a 15 × 15 × 0.2 cm mold at 160 ° C. for 20 minutes to prepare a target test piece (rubber sheet), and the vulcanization property “extractable acetone” , “300% modulus”, and “JIS hardness: room temperature and −20 ° C.”.

The test methods for the unvulcanized properties and vulcanized properties of the compositions obtained in the respective examples are as follows. Acetone extraction amount of vulcanized rubber 0.5 g of rubber was subjected to Soxhlet extraction for 8 hours using n-hexane as an extraction solvent. Unvulcanized properties 1) Mooney viscosity: 10 based on JIS K 6300
It was measured at 0 ° C. Vulcanization properties 1) 300% modulus: measured according to JIS K6251 (dumbbell-shaped No. 3). 2) JIS hardness (room temperature and -20 ° C): JIS K
Measured according to 6253.

Standard Examples 1 to 6, Examples 1 to 10 and Comparison
Examples 1 to 8 These examples illustrate the use of (1) polysiloxane 1 or polysiloxane 2 for each rubber of the NR, SBR and NR / SBR series.
1 shows the evaluation results of a rubber composition containing (1) and a rubber composition containing (2) a silane coupling agent, an OH-terminated silicone, and a catalyst 1. For each example, their formulations and results are shown in Table I.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

[0030]

[Table 5]

[0031]

[Table 6]

[0032]

[Table 7]

The following can be understood from Table I. In the rubber composition of Example 1 in which a predetermined amount of the silane coupling agent, the OH-terminated silicone and the catalyst 1 were blended with the rubber composition of the standard example 1 (NR rubber composition), the migration was extremely small (acetone The extraction amount is small), the processability in the unvulcanized state is good (the Mooney viscosity is remarkably reduced), and the vulcanized properties (300% modulus, JIS)
(Hardness: room temperature and −20 ° C.). On the other hand, in the case of Comparative Examples 1 and 2 in which the above-mentioned compounding components were not added, since a softening agent such as aromatic process oil or low molecular weight butadiene rubber was added, the processability and vulcanization during the unvulcanization were added. It can be seen that the sulfate properties are excellent but the migration is high.

Further, a predetermined amount of the silane coupling agent and O were added to the rubber composition (NR rubber composition) of Standard Example 2.
Example 2 in which H-terminal silicone and catalyst 1 were blended, and Examples 3 to 6 in which polysiloxane 1 or 2 was blended
In the case of No. 3, the migration is extremely small, the workability in the unvulcanized state is good, and the vulcanized properties are also excellent. On the other hand, in the case of Comparative Example 3 in which the above-mentioned compounding components were not added, since the aromatic process oil (softening agent) was added, the processability and the vulcanized physical properties when unvulcanized were excellent. However, it turns out that migration is high.

In addition, the rubber compositions of Standard Examples 3 and 4 (S
In the case of Examples 7 and 8 in which a predetermined amount of a silane coupling agent, an OH-terminated silicone and a catalyst 1 were blended with respect to the BR rubber composition), the migration was extremely small, and the processing before unvulcanization was performed. The properties are good, and the vulcanization properties are also excellent. For these,
In the case of Comparative Examples 4 and 5 in which the above-mentioned components were not added, since the aromatic process oil (softening agent) was added, the processability and the vulcanization properties in the unvulcanized state were excellent. It turns out that Great is high.

Further, the rubber compositions of Standard Examples 5 and 6 (N
In the case of Examples 9 to 11 in which a predetermined amount of a silane coupling agent, an OH-terminated silicone and a catalyst 1 were blended with respect to the R + SBR rubber composition), the migration was extremely small, and the unvulcanized processing was performed. The properties are good, and the vulcanization properties are also excellent. In contrast, Comparative Examples 6, 7 and 8 in which the above-mentioned components were not added
Is excellent in processability and vulcanization properties when it is not vulcanized due to the addition of aromatic process oil or low molecular weight butadiene rubber (both softeners), but high migration I understand.

[0037]

As described above, according to the present invention,
By mixing a silicone with a low temperature dependency of viscosity into which a functional group capable of co-vulcanization is introduced into rubber, a soft rubber cured product is obtained without migration, and even at low temperatures. A rubber composition having improved processability can be obtained. Therefore, the rubber composition of the present invention is extremely useful as a rubber composition for various tires, a rubber composition for various hoses, and the like.

Claims (2)

[Claims] 1. A rubber composition comprising 100 parts by weight of rubber and 50 parts by weight or less of polydimethylsiloxane containing covulcanizable sulfur. 2. 100 parts by weight of rubber, 50 parts by weight or less of silanol-terminated polydimethylsiloxane, 10 parts by weight or less of a co-vulcanizable sulfur-containing silane coupling agent, and 10 parts by weight or less of a silanol condensation catalyst. A rubber composition that is compounded.