JPH11335403A - Production of rubber product and rubber composition therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a rubber product having high reinforcing effect in high workability by forming silica in a non-crosslinked rubber by a specific method and crosslinking the non-crosslinked rubber. SOLUTION: A non-crosslinked rubber is swollen by immersing in a reinforcing liquid containing an aikoxysilane compound. The swollen non-crosslinked rubber is immersed in water containing a catalyst (preferably n-butylamine) to form a polycondensation product of the hydrolyzate of the alkoxysilane compound in the swollen non-crosslinked rubber and a crosslinking agent (preferably sulfur) is added to the rubber to effect the crosslinking. The alkoxysilane compound is preferably a compound of formula (at least three of R<1> 1 to R<4> are each an alkoxy and the remaining group is H or a univalent organic group), especially tetraethoxysilane (all of R<1> to R<4> are ethoxy groups). The polycondensation product in the non-crosslinked rubber has an average particle diameter of preferably 2-8 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a rubber product reinforced by utilizing a sol-gel reaction and a rubber composition used for the method.

[0002]

2. Description of the Related Art Conventionally, as a method of reinforcing a rubber product, a filler such as carbon black or silica has been mixed into rubber. The method of mixing
Generally, a method (kneading method) of mechanically kneading the rubber before crosslinking by using a Banbury mixer, a kneader, a roll, or the like to knead the filler and the filler is generally used.

[0003]

However, when a large amount of a white filler such as silica is blended to enhance the reinforcing effect, the kneading processability is poor, the kneading takes time, and the uncrosslinked material is not used. For example, the Mooney viscosity of a rubber composition containing a rubber, a filler, and a cross-linking agent is increased, thereby causing a problem that molding processability is poor. In addition, by blending a large amount, it is difficult for the white filler to be uniformly dispersed in the rubber product,
There is a problem that a reinforcing effect cannot be expected as compared with the case where carbon black or the like is filled. These problems are particularly noticeable when silica is used as the filler. It is considered that this is because a large number of hydroxyl groups are present on the silica surface, so that the silica has a strong cohesive force and the affinity with the rubber is low. Therefore, there is a demand for the development of a new technology capable of obtaining a rubber product having a high reinforcing effect without deteriorating workability even if silica is highly filled.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a production method capable of obtaining a rubber product having a high reinforcing effect with good workability and a rubber composition used therefor.

[0005]

In order to achieve the above object, the present invention provides an uncrosslinked rubber, and swells the uncrosslinked rubber by dipping it in a reinforcing agent solution containing an alkoxysilane compound. A method for producing a rubber product in which a swelled uncrosslinked rubber is immersed in catalyst water to form a polycondensate of a hydrolyzate of an alkoxysilane compound in the swelled uncrosslinked rubber, and then a crosslinking agent is added to perform crosslinking, is a first method. Make a summary.

Further, a second aspect of the present invention is a rubber composition mainly comprising an uncrosslinked rubber in which a polycondensate of a hydrolyzate of an alkoxysilane compound is dispersed, and a crosslinking agent.

The present inventors have conducted a series of studies in order to develop a production method capable of obtaining a rubber product having a high reinforcing effect with good workability. In the process, attention was paid to a sol-gel method in which an alkoxysilane compound was used as a starting material, and this was hydrolyzed and polycondensed. That is, in the kneading method, it is known that the reinforcing effect is higher as the filling amount of the white filler such as silica is larger, and that the reinforcing effect is higher as the particle size of the white filler such as silica is smaller. When the particle size is small, it is difficult to uniformly disperse the particles and to uniformly disperse the particles. Therefore, instead of mechanically kneading a white filler such as silica previously generated, silica is generated inside the rubber product. I remembered that. Therefore, a method was first studied in which the crosslinked rubber product was immersed in a solution containing an alkoxysilane compound, water and a catalyst to allow the alkoxysilane compound to penetrate and generate silica inside the rubber product. Although this method has the advantage that a rubber product having a high reinforcing effect can be obtained with good workability, silica is generated inside the rubber product whose shape is already determined, so that the warpage and deformation of the rubber product due to volume increase It was found that this method was not suitable for those requiring dimensional accuracy. Therefore, it was recalled that silica was formed by adding water and a catalyst while kneading an uncrosslinked rubber and an alkoxysilane compound, not after crosslinking. In this method, since silica is generated during kneading, there is an advantage that the dimensional accuracy of the obtained rubber product does not deteriorate, but a catalyst having a low boiling point may volatilize due to frictional heat at the time of kneading. I figured it out. Thus, the present inventors have conceived of producing silica inside an uncrosslinked rubber before kneading, instead of producing silica after crosslinking or during kneading, and using this to produce a rubber product. That is, the uncrosslinked rubber is immersed in a reinforcing agent solution containing an alkoxysilane compound to swell, and then the swollen uncrosslinked rubber is immersed in catalyst water to weigh the hydrolyzate of the alkoxysilane compound in the swollen uncrosslinked rubber. If a condensate is formed and then a crosslinking agent is added to cause crosslinking, there is no risk of dimensional accuracy being deteriorated or the catalyst being volatilized, and an increase in Mooney viscosity of the rubber composition is suppressed, and reinforcement is performed. The inventors have found that a highly effective rubber product can be obtained, and have reached the present invention. The reason why the Mooney viscosity does not increase is not necessarily clear, but according to the inventors' presumption, it is considered that the silica oligomer generated during the polycondensation reaction acts as a plasticizer.

In particular, it has been found that the use of the alkoxysilane compound represented by the general formula (1) is particularly preferable as a material for reinforcing rubber products.

In addition, a rubber composition containing a crosslinking agent as a main component and an uncrosslinked rubber in which a polycondensate of a hydrolyzate of an alkoxysilane compound is dispersed, can produce a rubber product having a high reinforcing effect. It has been found that the rubber composition is particularly preferable.

[0010] In the present invention, the term "main component" means:
50% by weight or more, preferably 7% by weight, based on the whole rubber composition
It means that it is contained in an amount of 0% by weight or more, optimally 90% by weight or more.

[0011]

Next, an embodiment of the present invention will be described.

In the present invention, an uncrosslinked rubber, a reinforcing agent solution containing an alkoxysilane compound, catalyst water, and a crosslinking agent are used.

The uncrosslinked rubber is not particularly limited, and natural rubber (NR), isoprene rubber (I
R), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber (CR), fluorine rubber (FKM), butyl rubber (IIR), ethylene-propylene copolymer Polymerized rubber (EPM), ethylene-propylene-diene terpolymer rubber (EPDM), hydrogenated nitrile rubber (hydrogenated NBR), silicone rubber, epichlorohydrin rubber (CO, ECO), polysulfide rubber (T),
Urethane rubber (U) and the like. These may be used alone or in combination of two or more.

The reinforcing liquid used together with the uncrosslinked rubber may be a solvent-free type or a type containing an organic solvent as long as it contains an alkoxysilane compound as a silica monomer. It may be something. Since both can swell the uncrosslinked rubber, the alkoxysilane compound can penetrate into the uncrosslinked rubber.

The alkoxysilane compound is not particularly limited, but a compound represented by the following general formula (1) is preferably used. The alkoxysilane compound used in the present invention is, if at least two of the four monovalent substituents bonded to the silicon atom are alkoxy groups,
Although a polycondensate of a hydrolyzate can be produced by a sol-gel reaction, those represented by the above general formula (1) are preferable from the viewpoint of producing a rubber product having a higher reinforcing effect.

[0016]

Embedded image

The alkoxy group in the general formula (1) is preferably an alkoxy group having 1 to 6 carbon atoms.
Methoxy group, ethoxy group, normal propoxy group, isopropoxy group, normal butoxy group, isobutoxy group,
Examples thereof include a sec-butoxy group, a tert-butoxy group, a pentyloxy group, and a hexyloxy group.

The monovalent organic group is other than an alkoxy group and includes an alkyl group, an aryl group, an aralkyl group and the like.

The most suitable alkoxysilane compound is tetraalkoxysilane in which all of R ^{1 to} R ⁴ are alkoxy groups. This is because when all are alkoxy groups, the structure of the polycondensate of the hydrolyzate becomes dense.

The tetraalkoxysilane is not particularly limited, but includes tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, tetraphenoxysilane and the like. Among them, from the viewpoints of ease of handling during production, reactivity with water, and the like, particularly R ¹
Wherein each of R ⁴ to R ⁴ is an ethoxy group;
The preferred is tetraethoxysilane (TEOS).

[0021]

Embedded image

A constituent material other than the above-mentioned alkoxysilane compound, which is used for a type containing an organic solvent.
Examples of the organic solvent include, but are not particularly limited to, tetrahydrofuran, cyclohexane, isobutyl acetate, methyl isopropyl ketone, butyl acetate, carbon tetrachloride, ethylbenzene, p-xylene, methyl ethyl ketone, and toluene. These may be used alone or in combination of two or more. In the case of a reinforcing agent liquid containing an organic solvent, it is prepared by blending and mixing an alkoxysilane compound (A) and an organic solvent (B). This mixing ratio is A / B in volume ratio.
= 100/0 to 10/90. More preferably, A / B = 100/0 to 70/3
0. In addition, A / B = 100/0 means that it is a non-solvent type containing only an alkoxysilane compound and not containing an organic solvent.

The catalyst water used together with the uncrosslinked rubber and the reinforcing agent liquid is prepared by mixing water and a catalyst.

The water is not particularly limited, and conventionally known water is used. The amount of water used is not particularly limited as long as the hydrolysis reaction of the alkoxysilane compound can be started, and a small amount may be used.

The catalyst is not particularly limited as long as it can promote the sol-gel reaction, and examples thereof include basic catalysts such as ethylenediamine, ammonia, n-butylamine, cetylamine and triethylamine, and acidic catalysts such as hydrochloric acid. Can be Above all, n-butylamine is preferable in that the sol-gel reaction can be performed more favorably. The amount of the catalyst to be used is preferably about 0.01 to 1 times by mole fraction with respect to the alkoxysilane compound.

The cross-linking agent used for cross-linking the uncross-linked rubber is not particularly limited, and any conventionally known cross-linking agent may be used. Examples thereof include sulfur and peroxide, with sulfur being preferred.

In addition to the above crosslinking agents, conventionally known rubber compounding agents may be added. As a rubber compounding agent, a crosslinking accelerator,
Crosslinking accelerator, crosslinking retarder, filler, softener, plasticizer,
Processing aids, anti-aging agents, silane coupling agents, and the like.

Next, the method for producing the rubber product of the present invention is carried out using the above-mentioned materials, for example, as follows. That is, first, an uncrosslinked rubber formed into a sheet having a thickness of about 0.5 to 2 mm is prepared. The method of forming the sheet is not particularly limited, and it can be performed using a conventionally known device such as a calendar. Then, the obtained sheet-like uncrosslinked rubber is immersed in the above-mentioned reinforcing agent solution for a predetermined time [for example, room temperature (25 ° C.) × 48 hours] to produce a swollen uncrosslinked rubber in which the alkoxysilane compound has penetrated. Thereafter, the swollen uncrosslinked rubber is taken out of the reinforcing agent liquid, and excess reinforcing agent liquid is removed. Next, the swollen uncrosslinked rubber is immersed in catalyst water for a predetermined time [for example, at room temperature (25
° C) x 280 hours]. As a result, the catalyst water permeates into the swollen uncrosslinked rubber, and the alkoxysilane compound present therein is hydrolyzed with the permeation, and the hydrolyzate is polycondensed to form a polycondensate (in-situ sol-gel reaction). (In situ Sol-Gel reaction)]. The polycondensate includes silica and a silica oligomer represented by the following general formula (3).

[0029]

Embedded image

Then, if necessary, a treatment such as air drying or vacuum drying is performed to remove unreacted alkoxysilane compounds and the like. Thus, an uncrosslinked rubber in which a polycondensate of a hydrolyzate of an alkoxysilane compound is dispersed can be obtained.

The average particle size of the polycondensate in the uncrosslinked rubber is preferably set to 30 nm or less. Preferably, it is in the range of 1-20 nm, optimally 2-8 nm. Normally, rubber products are filled with a large amount of filler, and a higher reinforcing effect is obtained as the particle size is smaller, so in the present invention, if the average particle size of the polycondensate is set within the above range, This is because it becomes a high-strength rubber product.

Next, an uncrosslinked rubber in which the above-mentioned polycondensate is dispersed and a rubber compounding agent containing a crosslinking agent are blended at an appropriate ratio to prepare a rubber composition. Then, using this rubber composition, a rubber product can be produced by, for example, heat crosslinking according to a conventionally known method.

According to this production method, a rubber composition containing a crosslinking agent together with an uncrosslinked rubber in which a polycondensate of a hydrolyzate of an alkoxysilane compound is dispersed in advance is used. The rise in viscosity is suppressed,
A rubber product can be manufactured with good workability. In addition, since a polycondensate of a hydrolyzate of an alkoxysilane compound is not generated in a dynamic state like kneading, but is statically generated in an uncrosslinked rubber, a catalyst having a low boiling point may be volatilized. There is no fear. The rubber product thus obtained has a reinforcing effect that cannot be obtained by mechanical kneading since the polycondensate is uniformly dispersed therein. When the compound represented by the general formula (1) is used as the alkoxysilane compound, the interaction between the rubber and the polycondensate becomes strong, and the hysteresis loss is reduced. The reason for this is that a silica network (a kind of cross-linked structure between cross-linked rubber and polycondensate) inside the rubber product
Is formed.

Next, examples will be described together with comparative examples.

[0035]

EXAMPLE First, 400 g of uncrosslinked NR (RSS # 3)
Was prepared and formed into an uncrosslinked rubber sheet having a thickness of about 1 mm using two rolls. Then, it was immersed in a reinforcing agent solution consisting of only TEOS at room temperature (25 ° C.) for 48 hours to produce a swollen uncrosslinked rubber sheet. After immersion,
The swollen uncrosslinked rubber sheet was taken out of the reinforcing agent liquid and excess TEOS was removed. Then, the swelled uncrosslinked rubber is immersed in catalyst water prepared so that the molar fraction thereof becomes 0.05 times by mole fraction at room temperature (25 ° C.) for 280 hours. The alkoxysilane compound was hydrolyzed and polycondensed inside the rubber sheet to form a polycondensate. Thus, an uncrosslinked rubber sheet (NR Sol-Gel M / B) in which the polycondensate was dispersed was produced.
The content of the polycondensate in this uncrosslinked rubber sheet was calculated from the result of ash content measurement by thermogravimetric analysis (TGA), and the result is shown in Table 2 below.

Next, the obtained uncrosslinked rubber sheet and the respective materials shown in Table 1 below were blended at the ratio shown in the same table, and kneaded with an open roll to prepare a rubber composition. The Mooney viscosity and scorch time of this rubber composition were measured, and the results are shown in Table 2 below.

Then, the above rubber composition was heated at 150 ° C. × 2
Press-crosslinking was performed for 0 minutes to produce a rubber product. For this rubber product, the stress at 50% elongation (M ₅₀ ), the stress at 100% elongation (M ₁₀₀ ),
Stress at the time of 00% elongation (M ₂₀₀ ), normal state physical properties (T _B ,
E _B , H _S ) and specific gravity (SG) were measured, and the results are shown in Table 2 below.

[0038] [M _50, M _100, M _200] JIS K 6
It measured according to 301.

[Normal physical properties] Measured according to JIS K6301. T _B: strength at break E _B: elongation at break H _S: hardness

[0040]

Comparative Example Each of the materials shown in Table 1 below was blended in the ratio shown in the same table to prepare a rubber composition. For this rubber composition, the Mooney viscosity and scorch time were measured in the same manner as in Example 1, and the results are shown in Table 2 below.

Then, the above rubber composition was heated at 150 ° C. × 2
Press-crosslinking was performed for 0 minutes to produce a rubber product. This
About 50% elongation of the rubber product of
Long time stress (M₅₀), Stress at 100% elongation
(M₁₀₀), Stress at 200% elongation (M ₂₀₀), Normal
Sex (T_B, E_B, H_S), Specific gravity (SG)
The results are shown in Table 2 below.

[0042]

[Table 1]

[0043]

[Table 2]

From the results shown in Table 2 above, the Mooney viscosity of the rubber composition of the example product was much lower than that of the rubber composition of the comparative product filled with substantially the same amount of filler. Also,
The rubber product of the example product has almost the same physical properties such as elongation at break, hardness, and specific gravity as the rubber product of the comparative example product, but has a strength at break, a stress at 50% elongation, and a 100% elongation. Stress and stress at 200% elongation were large. In particular, the greater the elongation, the greater the stress.

[0045]

As described above, according to the present invention, an uncrosslinked rubber is prepared, the uncrosslinked rubber is immersed in a reinforcing agent liquid containing an alkoxysilane compound to swell, and then the swollen uncrosslinked rubber is converted into a catalyst. Immersed in water to form a polycondensate of the hydrolyzate of the alkoxysilane compound in the swollen uncrosslinked rubber,
This is a method for producing a rubber product which is then crosslinked by adding a crosslinking agent. Therefore, the Mooney viscosity of the rubber composition containing the uncrosslinked rubber in which the polycondensate is dispersed and a crosslinking agent as main components does not increase, and a rubber product can be manufactured with good workability. The rubber product thus obtained has a high reinforcing effect because the polycondensate is uniformly dispersed and can be highly filled.

In particular, when an alkoxysilane compound represented by the general formula (1) is used, a rubber product having a higher reinforcing effect can be obtained.

Therefore, the rubber product obtained by the present invention is suitably used for so-called bright rubber applications such as vibration-proof rubber, rubber jars, conveyor belts and oil fences.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinji Iio 3600, Gezu, Kita-gaiyama, Komaki-shi, Aichi Prefecture Inside of Tokai Rubber Industries Co., Ltd. Address: Tokai Rubber Industries Co., Ltd. (72) Inventor: Shinsuke Koyamauchi, Omaki, Kochi City, Aichi Prefecture 3600 3600 Tokai Rubber Industries Co., Ltd.

Claims (3)

[Claims] An uncrosslinked rubber is prepared, the uncrosslinked rubber is immersed in a reinforcing agent solution containing an alkoxysilane compound to swell, and then the swelled uncrosslinked rubber is immersed in catalyst water to swell the uncrosslinked rubber. A method for producing a rubber product, comprising: forming a polycondensate of a hydrolyzate of an alkoxysilane compound in the solution, followed by adding a crosslinking agent to perform crosslinking. 2. The method for producing a rubber product according to claim 1, wherein the alkoxysilane compound is represented by the following general formula (1). Embedded image 3. A rubber composition comprising, as main components, an uncrosslinked rubber in which a polycondensate of a hydrolyzate of an alkoxysilane compound is dispersed, and a crosslinking agent.