JPS63301245A - Rubber composition - Google Patents

Abstract

PURPOSE:To obtain a rubber composition improved in mechanical properties and capable of being variously colored, by mixing a rubber with a mica powder specified in weight-average flake diameter and weight-average aspect ratio. CONSTITUTION:A rubber composition containing a rubber and a mica powder of a weight-average flake diameter <=100mu and a weight-average aspect ratio of 10-70, wherein the mixing ratio of said mica powder is 10-100pts.wt. per 100pts.wt. rubber. It is desirable that this rubber composition contains an organosilane compound, the so-called silane coupling agent. As said mica powder used, muscovite can be particularly desirably used since the obtained rubber composition has a high degree of freedom of coloration. It is desirable that the rubber used is modified with carboxyl groups.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a white compounded rubber composition used for industrial parts, industrial parts, automobile parts, etc. More specifically, it relates to a white compounded rubber composition containing mica powder and rubber as essential components and having excellent properties such as modulus, unvulcanized tensile strength, dimensional accuracy, weather resistance, vibration absorption, and gas barrier properties. Taking advantage of these characteristics, the composition of the present invention is preferably used in fields that require both performance such as modulus, dimensional accuracy, weather resistance, vibration absorption, and coloring.

[Conventional technology]

Anhydrous and hydrated silicic acid, calcium silicate, clay, calcium carbonate, talc, and the like are used as reinforcing fillers in white or colored rubber compositions, so-called white compounded rubber compositions. However, white compounded rubber compositions using these fillers have a problem in that they have poorer mechanical properties than rubber compositions containing carbon black. On the other hand, rubber compositions containing carbon black have excellent mechanical properties, but are black in color and have no flexibility in coloring.

[Problem that the invention seeks to solve]

The purpose of the present invention is to obtain a rubber composition that has excellent mechanical properties and can be colored in various colors. It means improving the modulus (hereinafter abbreviated as M), hardness, and strength by <300% without causing any significant adverse effects.

[Means for solving problems]

However, as a result of intensive studies by the present inventors to improve the above-mentioned problems, we found that coloring is possible and the mechanical properties are excellent by blending mica powder with a specified shape and blending ratio into rubber. The present inventors have discovered that a rubber composition can be obtained, and have completed the present invention.

As will be explained in detail in the examples below, the rubber composition of the present invention not only allows coloring and has excellent mechanical properties, but also has good tensile strength and dimensional accuracy during processing. It also has good vibration absorption properties, weather resistance, and gas barrier properties during use.
It has a number of favorable characteristics.

The type of mica powder used in the present invention is not particularly limited, and can be appropriately selected from muscovite, phlogopite, sericite, biotite, soda mica, synthetic mica, etc. Muscovite is particularly preferably used in the sense that the resulting rubber composition has a high degree of freedom in coloring.

The average flake diameter of the mica powder used in the present invention must be 100 u- or less, but
701JII, preferably 10-501Im
A rubber composition using mica powder with a zero weight average flake diameter of more than 1001I is more preferably
On the other hand, there is no particular restriction on the lower limit of the weight average flake diameter of mica powder, but in general, as the weight average flake diameter becomes smaller, Due to the fact that the weight average aspect ratio becomes small and the production of such mica powder requires a large amount of energy for crushing, the actual weight average flake diameter of mica powder is The lower limit of is about 5II-.

The weight average aspect ratio of the mica powder used in the present invention must be 10 or more and 70 or less, and 15
A rubber composition containing mica powder having a weight average aspect ratio of less than 10, which is preferably 70 or less, has good mechanical properties, particularly M3°. Since the improvement effect of
cannot be used.

Moreover, if it exceeds 70, crosstalk becomes difficult, which is not preferable.

The weight average flake diameter of the mica powder used in the present invention is determined by classifying the mica powder using a sieve or microsieve with various openings, and classifying the results by Rosin-Rammla.
The opening of the sieve or microsieve through which 50% by weight of the total weight of the mica powder subjected to measurement passes through, plotted on the r diagram! ,. This is the value calculated from equation (1) or (2) using In other words, the weight average flake diameter l of mica powder is: 1=/″r1. (When measured with a sieve) (1) 1
= 1. . (In the case of measurement using a microsieve) It is determined by (2). Here, the part of the mica powder with a large particle size is classified by a sieve, and the part with a fine particle size is classified by a microsieve.

On the other hand, the weight average aspect ratio α of the mica powder in the present invention is a value calculated using equation (3) from the weight average flake diameter ρ and the weight average flake thickness d measured by the following method.

α=l/d (3) The weight average flake thickness d of the mica powder in equation (3) is the water surface single particle film property (C, E, Capes and R, C, Cole
man, Ind, Eng, C1ean, Funda
This is a value calculated from equation (4) using the occupied area S of the flakes on the water surface, which is measured by M. M., 12.124 (1973)).

Here, W is the weight of the mica powder used for measurement, ρ is the specific gravity of mica, and (1-ε) is the occupancy rate when the mica powder is in the closest packed state on the water surface, which is generally 0 for mica powder. ．．
9 is used in the calculation.

In the case of the rubber composition of the present invention, the blending ratio of mica powder to 100 parts by weight of rubber needs to be 10 to 100 parts by weight. A composition containing less than 10 parts by weight of mica powder is M. . The improvement effect on mechanical properties, including , is unsatisfactory. On the other hand, when the blending ratio of mica powder exceeds 100% by weight, M of the resulting rubber composition. Although the value of 0 is extremely high, it causes problems such as poor workability and extremely low elongation.

There are no particular restrictions on the type of rubber used in the present invention, including natural rubber, synthetic polyisoprene rubber (IR), etc.
, styrene-butadiene rubber (SBR), polybutadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), ethylene-propylene rubber (EPDM), silicone rubber, urethane rubber, etc. depending on the application. It can be selected and used as appropriate. When mica powder is blended into these various rubbers, it is natural that the mechanical properties thereof will differ significantly depending on the type of rubber used. When a currently commonly used white filler is blended, a mica powder-blended rubber composition can be obtained which has extremely excellent mechanical properties and processability as described above.

The rubber used in the present invention is preferably modified with a carboxyl group. Examples of modification with a carboxyl group include maleic acid, fumaric acid, itaconic acid, citraconic acid, acrylic acid, methacrylic acid, crotonic acid, and incrotonic acid. , mesaconic acid, angelic acid, maleic anhydride, itaconic anhydride, citraconic anhydride, etc. Among these, particularly preferred are maleic anhydride and acrylic acid.

Modification of rubber with these compounds may be carried out by copolymerizing the rubber by coexisting these compounds during polymerization of the rubber, or by polymerizing the rubber in the presence or absence of a solvent.
Carboxyl-modified rubber, in which active sites may be generated in the rubber using a radical generator and these compounds may be reacted with the active sites, has a content of 0.1 to 5% by weight, preferably 0.2 to 3% by weight. It is desirable that the carboxyl-modified rubber used in the present invention contains a sufficient amount of the above-mentioned compound to provide carboxyl groups, and the carboxyl-modified rubber used in the present invention does not necessarily have to be entirely modified with carboxyl groups. It may be used by blending with unmodified rubber.

The rubber composition of the present invention preferably contains an organic silane compound, a so-called silane coupling agent. The silane coupling agent has the general formula (X)n Si
It is represented by (Y)m, and Y is generally an alkoxy group.

There is no particular restriction on X of the silane coupling agent used in the present invention, but it is a group containing an amino group, an epoxy group, a vinyl group, a mercapto group, etc., and n+m=4. In the rubber composition of the present invention, preferably n=1 and m=3, examples include γ-aminopropyltriethoxysilane, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, γ-ureidopropyl Triethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, vinyl-tris(β-
Particularly preferred are methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, and analogs thereof. These silane coupling agents may be attached to the mica surface in advance and the silane coupling agent-treated mica powder may be kneaded with the rubber, or they may be directly added during kneading of the rubber and mica powder. The silane coupling agent used in the composition improves the mechanical properties of the rubber composition, particularly M. . It has a remarkable effect on improving residual strain and residual strain.

The rubber composition of the present invention can be obtained by mixing various other compounding agents as necessary using a conventional mixer.

The compounding agents used in the present invention include sulfur or sulfur-donating compounds, vulcanization aids, sulfur vulcanization systems such as vulcanization accelerators, organic peracid compound vulcanization systems, plasticizers, softeners, processing aids, aging Compounding materials such as inhibitors and coloring agents that are commonly used in the rubber industry can be used, and the type and amount thereof are appropriately selected depending on the intended use.

In addition, there is no problem in using white fillers such as silica, calcium carbonate, talc, calcium silicate, etc. in addition to mica powder as necessary.

The rubber composition in the present invention can be colored. . Utilizing its features of excellent mechanical performance such as hardness and hardness, as well as excellent vibration absorption, weather resistance, and dimensional accuracy of molded products, we are able to manufacture products such as safety bumpers, brake parts, various tires, various hoses, etc. Interior refining related parts,
It is used in various applications such as automobile parts such as boots and belts, industrial parts such as rolls, ships such as fenders, marine hoses, marine related materials, parts for oil wells, and shoe soles for footwear.

〔Example〕

EXAMPLES Hereinafter, the composition of the present invention will be explained in more detail with reference to Examples, but these Examples are not intended to limit the present invention in any way.

Example 1 Polyisoprene rubber (Kuraray Kuraprene IR-10>
1 part by weight of 100 parts by weight, 50 parts by weight of muscovite powder with a weight average flake diameter of 151.1 m and an aspect ratio of 25, 3 parts by weight of sulfur, 5 parts by weight of zinc white, and a vulcanization accelerator (Tuxela NS>1
The rubber composition containing the parts by weight was kept at about 50°C6.
It was prepared by kneading it for about 20 minutes using an inch-diameter oven roll. The kneading properties were good. Immediately after taking out the Sea 1~-shaped kneaded material from the roll, measure its length (Lo), and then measure the length after leaving it at room temperature for 24 hours (L +), L ,bird,
Mill shrinkage was calculated from equation (5) using

The vulcanization rate was determined using a JSR type curelastometer.
Evaluation was made based on the time required for the shear modulus of the rubber composition to reach 90% of the value at the completion of vulcanization at a temperature of 45°C.

The sheet-like rubber composition was then vulcanized by heating in a hot press at 145° C. for 30 minutes to obtain a test piece with a thickness of 2 iv. The obtained test piece was white with a slight yellowish tinge.

A dumbbell No. 3 type test piece prepared by punching out the test piece was subjected to a tensile test at room temperature (23°C) at a deformation rate of 5QOmm/min, and the modulus was 300% (M2°).

), breaking strength T, ), and breaking elongation (E, ) were calculated.

Further, hardness H3) was measured using a spring-type device specified in JISK 6301.

Weather resistance was evaluated by exposing the test pieces outdoors for six months in the summer and visually evaluating the surface condition of the test pieces.

The above measurement results are summarized in Table 1. Satisfactory values were obtained for all evaluated performances.

Comparative Examples 1 to 3 Example 1 except that calcium carbonate (Comparative Example 1), silica (Comparative Example 2), and clay (Comparative Example 3), which are currently used as white fillers for rubber, were used instead of muscovite. The experiment was conducted using exactly the same composition and conditions as in the case of . In the experiment, Akadama manufactured by Shiraishi Kogyo Co., Ltd. was used as the calcium carbonate, Tokusil U manufactured by Tokuyama Soda Co., Ltd. was used as the silica, and Silcalite manufactured by Takehara Chemical Co., Ltd. was used as the clay. As shown in Table 1, the results showed that the mill shrinkage was larger than that of the composition of Example 1, and M
,. . , T6. The composition was also poor in HIl and weather resistance.

4 Shimomuneguchi Table 1 Example 2 The muscovite powder used in Example 1 was
．． Table 2 shows the results of an experiment conducted under exactly the same composition and conditions as in Example 1, except for surface treatment with 5% γ-aminopropyltriethoxysilane. . . The vulcanization rate increased dramatically as well.

Example 3 Out of 100 parts of the rubber component, 95 parts were the same polyisoprene rubber as in Example 1, and the remaining 5 parts were carboxyl-modified liquid polyisoprene rubber (Kuraray's Kuraprene L).
Table 2 shows the results of an experiment conducted under exactly the same composition and conditions as in Example 1, except for using I R410). . has risen even more dramatically.

Example 4 The silane-treated muscovite powder used in Example 2 and the polyisoprene rubber and carboxyl-modified liquid polyisoprene rubber used in Example 3 were used, and the other compositions and conditions were exactly the same as in Example 1. The results of the experiment are shown in Table 2. In particular, a composition with extremely excellent performance was obtained for M 3 o6.

Below is a blank table 2 Example 5.6 Comparative Example 4.5 The weight average flake diameter and weight average aspect ratio of the muscovite powder used were 150p++ and 65, respectively (Comparative Example 4)
, 7011 m, 50 (Example 5), 1011 wheels, 15 (
Example 6), 511 m, 5 (Comparative Example 5) The results of an experiment conducted under the same composition and conditions as in Example 1 are shown in Table 3. If it becomes too much, E3 and T3 will become low (Comparative Example 4)
, On the other hand, if the flake diameter and aspect ratio of mica powder become too small, M. . is the same as in the case of clay (Comparative Example 3), and both are unsatisfactory.

Table 3 Examples 7 to 9 Comparative Examples 6 to 8 Using the muscovite powder used in Example 1 and the calcium carbonate used in Comparative Example 1, 0.5% by weight of the weight of these fillers was added during roll kneading. The experiment was conducted under exactly the same composition and conditions as in Example 1, except for adding γ-aminobrobyltriethoxysilane and changing the blending ratio of these fillers as shown in Table 4. The results are shown in Table 4.

In the region where the blending ratio of mica powder is low (Comparative Example 7), M, compared to Comparative Example 6 in which no mica powder is added. . , T is unsatisfactory, and on the other hand, when the mica powder content is increased to 120 parts by weight, the roll processability deteriorates so much that a uniform rubber composition cannot be obtained (Comparative Example 8).

4 Lower margin table 4 Examples 10 to 13 Weight average flake diameter is 40 - weight average aspect ratio 3
Using 0.0 phlogopite powder, 0.5% by weight of vinyl-tris(β-methoxyethoxy)silane (Example 10) and γ-glycidoxypropyltrimethoxysilane (Example 10) based on the weight of the phlogopite powder were used during roll kneading. 11), β-mercaptopropyltrilinoxysilane (Example 12), γ-aminopropyltriethoxysilane (Example 13), and 3 parts by weight of titanium oxide pigment. The experiment was conducted under exactly the same composition conditions as in the case. The experimental results are summarized in Table 5, and all the compositions had excellent performance. Furthermore, the composition before adding the titanium oxide pigment was colored brown, but the addition of titanium oxide changed the hue of the composition to a good white color.

Margin table below 5 Example 14 Comparative Examples 9 to 11 Styrene-butadiene rubber (SBFt150
Example 14 The same fruit @(Example 14) as in Example 1 was used except that
), Same experiment as Comparative Example 1 (Comparative Example 9), Same experiment as Comparative Example 2 (Comparative Example 10), Same experiment as Comparative Example 3 (Comparative Example 11)
I did it. However, the blending rate of sulfur is 2.5 parts by weight,
The first test was conducted at 145°C for 40 minutes.

The results are summarized in Table 6, and the composition of Example 14 was
It has superior mechanical properties compared to the compositions of Comparative Examples 9 to 11.

Table 6 Examples 15 to 17 Example 2 except that SBR1502 was used as the rubber
The same experiment as in Example 15 (Example 15), the same experiment as in Example 3 (Example 16), and the same experiment as in Example 4 (Example 17) were conducted. The carboxyl-modified rubber used in Examples 16 and 17 is the same carboxyl-modified liquid polyisoprene rubber as in Example 3.4. The experimental results are summarized in Table 7, and all have excellent mechanical properties.

Table 7 Example 18 Natural rubber (100 parts by weight of SMR-L, weight average flake diameter of 25 II m, weight aspect ratio of 50 muscovite powder)
Weight, γ-aminopropyltriethoxysilane 0.3
parts by weight, 5 parts by weight of zinc white, 1 stearic acid.

5 parts by weight Antioxidant 2 parts by weight Plasticizer 2 parts by weight Sulfur 2 parts
A rubber composition was prepared by blending parts by weight.

As shown in Table 8, the mechanical properties were good.

Example 19 Ethylene-propylene rubber (EPDM+Roy
alene502) 100 parts by weight, 50 parts by weight of muscovite powder with a weight average flake diameter of 251u+ and a weight average aspect ratio of 20, 40 parts by weight of naphthenic oil, 5 parts by weight of zinc white, 1 part by weight of stearic acid, and 1.5 parts by weight of sulfur. A rubber composition containing 2 parts by weight of anti-aging agent and 0.4 parts by weight of vinyl-tris-(β-methoxy ethoxy) silane was prepared. The mechanical properties of the composition are as shown in Table 8. was in good condition.

Example 20 100 parts by weight of acrylonitrile-butadiene rubber (NBR: Hiker 1052) was added with a weight average flake diameter of 25
1 m, 50 heavy parts of muscovite powder with a weight average aspect ratio of 20, dioctyl phthalate (DOP>10 parts by weight, zinc white 5 parts by weight, sulfur 0.2 parts by weight, γ-mercatobrobyltrimethoxysilane 0. A rubber composition containing 4 parts by weight was prepared.As shown in Table 8, the mechanical properties of the composition were good.

Table 8 [Effects of the Invention] According to the present invention, a rubber composition that can be colored and has extremely improved modulus, hardness, and strength by 300% without impairing tensile elongation, compressive residual strain, etc. is provided. be done.

Claims (1)

[Scope of Claims] 1) Contains rubber and mica powder with a weight average flake diameter of 100 μm or less and a weight average aspect ratio of 10 to 70 as essential components, and the blending ratio of the mica powder is based on 100 parts by weight of rubber. and 10 to 100 parts by weight of the rubber composition. 2) The rubber composition according to claim 1, which contains a silane coupling agent in addition to the rubber and mica powder. 3) The rubber composition according to claim 1 or 2, wherein the mica powder used is muscovite. 4) The rubber composition according to claims 1 to 3, wherein the rubber used is modified with a carboxyl group.