JPH0337247A - Acrylic fiber-reinforced rubber composition - Google Patents

Abstract

PURPOSE:To prepare an acrylic fiber-reinforced rubber compsn. excellent in the strengths and resistance to heat and oil by mixing a rubber with a specific acrylic fiber and specifying the dissolution rate of the acrylic fiber in a solvent. CONSTITUTION:A composite is made up of a rubber (e.g. acrylonitrile-butadiene copolymer rubber) and an acrylic fiber (e.g. polyacrylonitrile) comprising a polymer contg. at least 90% acrylonitrile. The fiber is selected in such a way that its dissolution rate in a solvent satisfies relations X1/X2<=0.05 and 0.05<=X2<=0.4 wherein X1 is an extraction ratio (wt. ratio of after to before extraction) of 30 chips made of the composite, 1mm thick, 1cm long and 1cm wide, after immersion in 200ml of dimethylformamide for 1hr at 20 deg.C and X2 is the ratio at 80 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an acrylic fiber reinforced rubber composition having excellent strength, heat resistance and oil resistance.

(Problems to be solved by the prior art and the invention) It is well known that rubber is used in a wide range of industrial fields, but by increasing its tensile strength, its application can be further expanded, such as in packing materials. It is already well known that it can be used for friction materials such as, high pressure hoses, etc. For such purposes, reinforced rubber in which rubber is reinforced with fibers has been reported. For example, fibers made of polyvarnish, vinylon, nylon, and aromatic polyamide are known as reinforcing fibers. However, each of these fibers has drawbacks, and requires the addition of various technologies to put them into practical use. For example, polyester fiber,
Nylon fibers and aromatic polyamide fibers generally have problems in adhesion to rubber, so techniques for improving adhesion have been described, for example, in Japanese Patent Publication No. 1-17494. Furthermore, vinylon fibers have low heat resistance, so their uses are extremely limited.

For this purpose, for example, Japanese Patent Application Laid-Open No. 57-1063
No. 2 and Japanese Unexamined Patent Publication No. 58-103539 disclose techniques for reinforcing diene thread rubber with micro-mimam. However, in order to produce a reinforcing effect in these methods, the glass transition temperature of the amorphous part must be below 30°C or above 120°C, and the melting point of the crystalline part must be 160°C.
This is the above, and it is necessary to add ultrafine special fibers with an average short fiber length of α8 to 30 μm and an average short fiber diameter of 0.02 to G, 8 μm. Specific examples of polymers constituting micro organic fibers include isotactic polypropylene, poly-4-methyl-1-pentene, polyvinylidene fluoride, polyvinylidene chloride, and polyp-tert.
-butylstyrene, poly-p-chlorostyrene, d+)
s) Chlorostyrene, poly-α-methylstyrene, poly-p-phenylstyrene, poly〇-hinylbenzyl alcohol, poly-1J-p-vinylbenzyl alcohol, polyhinylnaphthalene, polyoxymethylene, poly-bisphenol A carbonate , 1.4 poly-2,3 dimethylbutadiene, etc. are only exemplified.

On the other hand, according to the research conducted by the present inventors, acrylonitrile fibers have extremely amphoteric surface properties, as estimated from their molecular structure, and therefore have good adhesion to the rubber matrix. It was found that it is very suitable as Ia1a for rubber reinforcement. However, conventional acrylonitrile fibers have a drawback in that they have low tensile strength and are hardly effective in improving the tensile strength of rubber M. Furthermore, although acrylonitrile-based fibers are generally said to have excellent thermal stability, they cannot be used under extremely harsh conditions such as cross-firing conditions for actually dispersing them in rubber or vulcanization. The stability of these fibers cannot be said to be sufficient, and improvements in thermal stability and oxidation stability at high temperatures are desired. The acrylonitrile content for reinforcing the housing rubber is particularly important for improving strength, heat resistance, and oxidation resistance.

It was found that it is necessary to have a high tensile strength of the fibers.
This is achieved in particular by drawing as highly as possible during the spinning process, which results in a high degree of crystalline distribution. In this case, it was found that highly crystallographic orientation simultaneously improves heat resistance, especially oxidation stability, which was a truly unexpected effect.

Another feature of such acrylonitrile fibers is that they have excellent solvent resistance; for example, they are no longer soluble in solvents that can dissolve not only unoriented acrylonitrile polymers but also fibers used in conventional clothing. It turned out to be extremely difficult. It can be seen that the rubber composition according to the present invention not only has excellent tensile strength but also excellent solvent resistance.

(Means for Solving the Problems) The gist of the present invention is that the content of rubber and acrylonitrile is 90%
A composite made of acrylic fibers made of a polymer of 4 or more, with a thickness of 1cm and a length of 1α.
When 30 pieces of chips with a width of 1 inch were immersed in dimethylformamide (DM?) at 20°C for 1 hour, the weight of the extract was t.
/An acrylic fiber-reinforced rubber composition that satisfies the following, where xl is the extraction rate defined by the chip weight, and x2 is the extraction rate when 30 pieces of similar chips are immersed in DMIP at 80°C and 200- for 1 hour. It's in things.

X I / In order to achieve this, it is desirable that the acrylonitrile content be 90 or more, and if it is less than that, the effect cannot be sufficiently obtained.

A feature of the present invention is that whether or not the desired physical properties of the rubber composition can be obtained is determined by the dissolution rate of the acrylic fiber contained in the rubber composition in the solvent. The fact that the dissolution rate is low is itself one of the physical properties of the target rubber composition.Furthermore, the dissolution rate reflects the degree of orientation of the acrylic fibers a, and therefore It is an indicator of oxidation resistance, which is a physical property. Furthermore, as already mentioned, the degree of orientation corresponds to the tensile strength of the fibers. If the dissolution rate of the acrylic fibers in the solvent in the rubber composition is within a certain limited range, the rubber composition will have the desired extremely excellent physical properties.

The dissolution rate of acrylic fibers is as follows: 30 pieces of chips made of the rubber composition of the present invention with a thickness of 1-1, a length of 1-1, and a width of 1 bar are
When immersed in DMF at ℃ for 1 hour, the extraction rate defined as extraction axis load 11/chip iii
Each extraction rate is expressed when xl is the extraction rate when a 0 piece is immersed in DMF at 80° C. and 200° C. for 1 hour.

In other words, in xl, the portion with a low degree of orientation is extracted preferentially, whereas in case of X, all the acrylic fibers present in the composition are extracted regardless of the degree of orientation. , Xs / If this value is smaller than Q, 05, the thermal and chemical stability of the composition will be low.

Also, X! represents the total amount of acrylic fibers in the composition, and in order to obtain high tensile strength of the rubber composition, which is the first objective of the present invention, X must be 105 or more (L4 or less). be.

X! However, if i is less than [LO5], the amount of fiber is insufficient; conversely, if it is more than α4, it is difficult to uniformly disperse the fibers, and the tensile strength of the composition is rather reduced, which is not preferable.

The acrylic fibers used in the rubber composition of the present invention may be so-called long fibers or short fibers, and may be in the form of fibers, one-dimensional structure such as spun yarn or twisted yarn, or may be a two-dimensional structure such as a woven fabric, a knitted fabric, or a non-woven fabric made using these materials, or a three-dimensional structure such as felt.

The form of the acrylic fiber a is not particularly limited, but may be selected from a fineness of approximately α1d to 30ti. Total amount of acrylic fibers (when used dispersed in the form of short fibers, the length of the short fibers is 0.1 to 10w5 short lJl!m and the fineness is [
It is preferable that the aspect ratio is in the range of 10 to 1000.If the short fiber length is less than (LIW), it will be difficult to effectively reinforce the rubber composition.
If the length exceeds 5 m, the dispersibility of the acrylic fibers in the rubber composition will deteriorate, which is not preferable.

In addition, if the fineness of the short fibers is less than 0.1 (1), the dispersibility of the acrylic fiber will decrease, and if it exceeds 10 (1), the effective surface area of the acrylic fiber will be relatively reduced, making it impossible to obtain a sufficient reinforcing effect. .

Furthermore, if the aspect ratio is less than 10, the tensile strength of the acrylic fiber-reinforced rubber composition will not be sufficiently high, while if it exceeds 1000, the dispersibility of the acrylic fibers in the rubber composition will decrease, which is not desirable.

The acrylic fibers used in the present invention can be obtained, for example, by dissolving an acrylonitrile polymer in a suitable solvent and then using wet, wet-dry or dry spinning methods. It is necessary to use H11ia, and in this way, acrylic fibers, such as acrylonitrile polymers with a weight average molecular weight of 200,000 or more, are used as raw materials and subjected to a high degree of stretching of 10 times or more in the spinning step. Manufactured by A polymerization method suitable for this purpose is disclosed in Japanese Patent Application Laid-Open No. 59-19170.
No. 4, JP-A-61-12704, JP-A-61-142
06, etc., and the spinning techniques disclosed are JP-A-60-139809, JP-A-60-139810, JP-A-61-119708, and JP-A-61-1197.
No. 10, Japanese Unexamined Patent Publication No. 62-57910, and other publications.

Further, the rubber used in the present invention is not particularly limited, and includes natural rubber, synthetic polyisoprene rubber, butyl rubber, halogenated butyl rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer. rubber, ethylene-propylene-diene copolymer rubber, etc./l.

In the present invention, carbon black may also be blended at the same time. The acrylic fiber-reinforced rubber M4 compound of the present invention may further contain compounding agents such as a vulcanizing agent, a promoter, a filler such as silica, and a softening agent within the range of usual compounding amounts.

The acrylic fiber-reinforced rubber composition of the present invention is vulcanized and extruded or injection molded into the desired form according to a conventional method.

(Example) Hereinafter, the present invention will be explained in detail based on examples.

Examples 1-3. Comparative Examples 1 to 3 The acrylic fibers in the table are polyacrylonitrile having a weight average molecular weight of 700,000 obtained by the method described in JP-A No. 61-14206.
The spinning method described in the publication was followed. However, by appropriately changing the draw ratio applied to the final stage of drawing, the total draw ratio was changed, and various acrylic fibers were manufactured.

The fibers were cut into short fibers with a fineness of 2d and a length of 5m, and rubber, carbon black, and additives were mixed in the compounding ratio shown in Table 1, and kneaded in a Banbury mixer at 160°C for 20 minutes, and then 160 tl: Extrude with diameter 5wm, length 8
■It was cut into strands. Add this further to J-engine 8
In order to sample dumbbell specimens according to the test method described in K6301, they were extruded into sheets at 160°C. The physical properties and shape of the short fibers subjected to the test and the tensile test of the obtained rubber 7) are shown in Table J.
Make 60 pieces of chips with 1 convergence, and heat 30 of them at 20°C.
The remaining 30 chips were immersed in DMF at 80°C for 1 hour to measure xl, and the remaining 30 chips were immersed in DMP at 80°C for 1 hour to measure xl.

The results are shown in Table 2.

The heat resistance in the table is expressed by placing a dumbbell test piece similar to that used in the tensile strength measurement in a dryer at 120° C. and expressing the time at which the tensile strength retention rate at this time becomes 504.

On the other hand, for the chemical resistance in the table, dumbbell test pieces similar to those used for tensile strength measurements were measured using AES K6301.
It was expressed as the tensile strength retention rate when immersed at 40°C for 22 hours.

The polyester fiber of the comparative example was tested as a fiber for general clothing and materials.

Table 2 (Effects of the invention) The acrylic fiber-reinforced rubber composition according to the present invention can be easily produced by a simple process, and its manufacturing process power (significantly In addition to being simplified, the acrylic fiber reinforced rubber composition force (
It has high tensile strength, heat resistance, and oil resistance, and is suitable as a raw material for various rubber products such as hoses, packing, vibration-proofing materials, and sealing materials, so it has great industrial benefits.

Claims (1)

[Scope of Claims] A chip 30 having a thickness of 1 mm, a length of 1 cm, and a width of 1 cm made of an acrylic fiber made of a polymer containing rubber and acrylonitrile of 90% or more, the composite being made of the composite. Place the pieces in dimethylformamide at 20°C.
When soaked for a time, the extraction rate defined as extract weight/chip weight is
An acrylic fiber-reinforced rubber composition that satisfies the following, where the extraction rate when immersed in 0 ml of dimethylformamide for 1 hour is defined as X_2. X_1/X_2≦0.05 0.05≦X_2≦0.4