JPH0913226A - Short fiber for reinforcing rubber - Google Patents

Abstract

PURPOSE: To obtain the subject fiber having a sea-island state cross section, capable of being fibrillated with a mechanical shear force, high in adhesion to rubber matrices substantially without relating to the kinds of the rubbers, and good in dispersibility in the matrices. CONSTITUTION: A multicomponent fiber having a sea-island cross section and capable of being fibrillated with a mechanical shear force is cut in an aspect ratio good for dispersion to obtain the short fibers used for mixing and dispersing the short fibers in a rubbery polymer matrix. The sea-island cross-section fiber is preferably obtained e.g. by a method comprising dissolving (A) a polyvinyl alcohol polymer and (B) a water-insoluble polymer in an A/B weight ratio of 90/10 to 80/20 in a common solvent, and subsequently spinning the obtained solution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a fiber material suitable for reinforcing matrix rubber. Rubber reinforced by the fiber of the present invention can be used for various transmission belts, tires, hoses, gaskets, diamond flags, pistons. It can be used for caps, automobile exterior parts, etc.

[0002]

2. Description of the Related Art Rubber, resin, concrete, asphalt, and the like may be used alone, but since they have insufficient properties such as tensile strength / bending strength, modulus, and abrasion, they may be used depending on the application. So-called fiber reinforcement, in which inorganic short-cut fibers are added, mixed, and dispersed to reinforce them, is widely practiced. Reinforcing fibers at this time, the basic selection criterion is to have a higher strength, modulus, toughness than the matrix of rubber, resin, concrete, asphalt, etc. Adhesion between the matrices and uniform distribution of the fibers in the matrix are important. The conventional techniques for securing the adhesive force are roughly classified into 2
A method has been proposed.

The first method is to reduce the fineness or length of the short cut fibers to be used and increase the aspect ratio by dividing the fiber length by the fiber diameter to obtain a matrix contact area per strength of one fiber. It has an advantage in that it is cost effective, the reinforcing effect is not easily affected by the matrix and the fiber material, and there is little change in the adhesive strength with respect to the environment such as humidity. doing. However, this method has significant disadvantages. That is, when the aspect ratio is increased, the fibers are entangled with each other and it becomes impossible to uniformly disperse the fibers in the matrix.
It has only been applied to very limited applications, such as a slight improvement in reinforcement with a very small amount of fiber blending being satisfactory. The second method is to treat the fiber surface with resorcin-formaldehyde-latex treatment (RFL),
This is a method of chemically enhancing the adhesive force by subjecting it to treatment with isocyanate, epoxy resin, silane or the like. Currently, this method is widely used, but this chemical bonding treatment requires a relatively large cost, and there are cases where sufficient bonding strength cannot be obtained depending on the fiber and matrix.
Furthermore, the adhesive treatment method represented by RFL has a drawback that the adhesive force is significantly reduced due to water wetting.

On the other hand, the dispersion of the reinforcing fibers in the matrix varies depending on the type of the fiber or the matrix, but the quality is determined by the aspect ratio displayed by the value obtained by dividing the fiber length by the diameter. ~ 1000, more preferably 500 or less is required.

From the above, the ideal technique for fiber reinforcement does not affect the fiber material or the matrix material, has little difference in the reinforcing effect even when it is wet and dry, and enables this at a relatively low cost. Although it is a technique, as described above, the conventional technique is currently in practical use while having various drawbacks.

[0006]

SUMMARY OF THE INVENTION The present invention has solved the problems of the prior art. The gist of the present invention is to use a cut yarn having an aspect ratio within a range having good dispersibility, and particularly to form a rubber matrix. Providing a remarkable reinforcing effect in the case, the effect is almost independent of the rubber type, and furthermore, we propose a completely new reinforcing fiber that ensures a high degree of adhesion even if chemical bonding is omitted. Things.

[0007]

[Means for Solving the Problems] When the fibers are added / dispersed in a matrix, the present inventors carry out the above-described fiber shape having an aspect ratio with good dispersibility, and perform a nearly final processing such as a kneading / molding step. At the stage, by dispersing and thinning the fiber, both dispersion and adhesion are compatible, and because this adhesion method is based on physical wetting of the fiber to matrix, there is also a difference in physical properties due to water and the like. The present invention has been completed by finding that it can be an excellent reinforcing short fiber which is rare.

That is, the present invention is a fiber which is used by being mixed and dispersed in a matrix made of a rubber-like polymer in the form of a short fiber, the fiber being composed of at least two kinds of polymers, and the fiber cross section being a sea-island shape. In addition, the fiber is a rubber-reinforcing short fiber that is fibrillated by mechanical shear. And, preferably, such a sea-island cross-section fiber comprises a polyvinyl alcohol-based polymer (A) and a water-insoluble polymer (B), and A or B
One of them is an island component, the other is a sea component, and the A / B weight ratio is 90/10 to 20/80, which is a short fiber for rubber reinforcement.

The reinforcing short fibers of the present invention have a sea-island cross section, that is, at least one of the fiber-constituting polymers is a sea component and the other one or two or more are island components. It must be a multi-component fiber,
This is an essential condition in order to maintain a good aspect ratio with good dispersibility during fiber addition / dispersion, that is, a relatively low aspect ratio. is there. The fibers need to be divided and reduced in diameter when subjected to mechanical shearing force, in order to secure a fiber surface area for exhibiting a reinforcing effect. The average diameter after division and narrowing is preferably 5 μm or less, particularly preferably 0.03 to 3 μm, and 0.1 to 1.5 μm.
More preferably m.

If the average diameter after division / thinning exceeds 5 μm, the fiber surface area required for exerting the reinforcing effect is reduced, and as a result, the reinforcing becomes insufficient. The fiber for obtaining this divided diameter reduction must have a sea / island structure, and in particular, its polymer is composed of polyvinyl alcohol A and water-insoluble polymer B, one of which is an island component. However, it is more preferable that the other is a sea component because the adhesiveness to rubber is excellent. Furthermore, the polymer weight ratio A / B is 90/10 to 20/80, and
It is more preferable that the average thickness after division and diameter reduction is 0.03 to 3 μm, and further 0.1 to 1.5 μm.

As the water-soluble polymer, when the polymer (A) is a polyvinyl alcohol-based polymer, a solvent spinning method represented by a wet spinning method is used as a method for producing fibers, but the polymer (B) is used. As the polyvinyl alcohol-based polymer, a polymer that is soluble in a solvent can be obtained from the viewpoints of fiber division and thinning and high strength. Particularly, as a solvent, dimethyl sulfoxide (DM
When SO) is used, D as polymer (B)
It is preferable to use cellulose acetate and starch, which are soluble polymers in MSO. In the case of cellulose acetate, it may be saponified into cellulose after fiber formation. The water-insoluble polymer means a polymer that is not substantially dissolved even when the polymer is immersed in normal temperature water.
The polyvinyl alcohol-based polymer may be completely saponified, partially saponified, or copolymerized with another monomer.

The short fiber of the present invention is prepared by dissolving the sea component polymer and the island component polymer in a common solvent, wet spinning or dry spinning, and then wet drawing (there is no need to use in the case of dry spinning) and further drying. It is preferable to perform hot stretching. In order to increase the strength of the fiber and achieve better splitting and diameter reduction,
It is preferable to increase the draw ratio. As the thickness of the fiber,
It is in the range of 0.5 to 20 denier, more preferably 1 to 10 denier.

The type of matrix rubber that can be used in the fiber of the present invention is not limited at all, and for example, natural rubber (N
R), styrene-butadiene rubber (SBR), chloroprene rubber (CR), ethylene-propylene-diene rubber (EPDM) and the like can be used. Further, in addition to the present invention, it is also preferable to use an adhesive treatment such as RFL and isocyanate of the prior art in combination with the fiber before fibrillation in order not to reduce the effect of the present invention and to obtain higher adhesive strength. Furthermore, in the fiber of the present invention, the entire cross section of the yarn may be divided or reduced in diameter, or only the periphery thereof may be divided or reduced in diameter while leaving the trunk. Among them, the entanglement of the fibers is small, which is more preferable. In addition, when the shearing force is applied, the division and diameter reduction
It is more preferable that the fiber mainly occurs at a shear rate of × 10 ⁻⁵ sec ⁻¹ or more from the viewpoint of uniform dispersion of the fiber. If the fiber is divided by an extremely weak shearing force, the fiber may become entangled and dispersed depending on the processing method.

Next, an example of a method for producing a fiber reinforced product using the fiber of the present invention and having a rubber matrix will be described. First, the sea / island fiber of the present invention is cut into an aspect ratio of 30 to 1000 as in the prior art using a guillotine cutter or the like to obtain a shortcut fiber (short fiber). Next, a known rubber compound such as rubber, a vulcanizing agent, a vulcanization accelerator, a stabilizer, carbon, and a process oil and the above-mentioned short-cut yarn are weighed, kneaded with a banbury, and then with an open roll rubber kneading roll. After kneading, after this step, when a rubber sheet is obtained, it is processed into a product by a calender roll, or in the case of a molded product, by an injection or extrusion molding machine. The aspect ratio is a value obtained by dividing a fiber length by a diameter of a circle corresponding to a fiber cross-sectional area.

At this time, in the process of adjusting or injecting a rubber mastication roll, a roll gap of a calender, a rotation speed ratio, an extrusion molding machine process, a rubber discharge amount, a groove structure of an extrusion screw, a rotation speed or a gate to a mold part. By adjusting the gap and applying a shearing force at a shearing rate of 1 × 10 ⁻⁵ sec ⁻¹ or more in any step, the fiber is divided into small diameters, and a fiber-reinforced rubber product having good performance can be obtained. . 1x1
The division-reducing at a shear rate of less than 0 ^-5 sec ^-1 also occurs in a fiber production stage or a preparation process before production of rubber products such as a guillotine cutter process, which causes a problem in dispersion of fibers in rubber, which is not preferable. . Further, the short-cut fiber addition of the present invention is an open roll or the like after the bamber, or injection,
It is also preferable to carry out it in a subsequent step such as an extrusion molding machine step, from the viewpoint of preventing the dispersion deterioration due to the fiber entanglement due to the divided diameter reduction. Further, it is more preferable to form a so-called masterbatch in which the fiber of the present invention is highly filled in rubber and to add the masterbatch in a processing step such as the above-mentioned open roll, without reducing the effect of the present invention.

[0016]

The present invention will be described below with reference to examples. The average diameter of the fiber after splitting is determined by taking a micrograph of the fibrillated fiber, drawing an arbitrary straight line on the photograph, calculating the fiber width at the point where the fiber crosses the straight line, and calculating this value by 20. It is obtained by calculating the arithmetic mean.

Example 1 Polyvinyl alcohol having a degree of polymerization of 1750 and a degree of saponification of 99.9 mol% (hereinafter abbreviated as PVA) and a degree of polymerization of 180,
Cellulose acetate having a degree of acetylation of 55% (hereinafter abbreviated as CA) was weighed in a weight ratio shown in Table 1, dimethylsulfoxide (DMSO) was added, and the mixture was dissolved by stirring under a nitrogen stream at 80 ° C. for 10 hours to obtain a polymer concentration. A 25% by weight polymer solution was obtained. This solution was used as a spinning stock solution and was passed through a spinneret with 400 holes and a hole diameter of 0.10 mmφ to produce DMSO /
Dry / wet spinning in a solidification bath at a temperature of 10 ° C with a methanol weight ratio of 30/70, wet drawing of 3.0 times, DMS in the yarn
After extracting O with methanol, dry it with hot air at 80 ℃ and 225 ℃.
PVA with dry heat stretching at 0.8 times the maximum draw ratio
A blend fiber of 1200 denier / 400 f of / CA was obtained. Then, it is treated in 1N caustic soda for 30 minutes at 50 ° C. to saponify CA into cellulose, and further formaldehyde 30 g / l, sulfuric acid 200 g / l and mirabilite 1.
It was dipped in a 50 g / l bath at 70 ° C. for 30 minutes for acetalization. When the cross section of this fiber was observed with a transmission electron microscope, it was found to be sea / island shape. This fiber was cut into 2 mm using a guillotine cutter.

SBR / NR = 1/1 is used as a matrix and one of 7.5 inφ × 2 rolls is 11.5 m / m.
in, the other was kneaded with a rubber kneading roll at 80 ° C. at a rotation speed of 13.0 m / min and a roll gap of 10 mm,
10 parts by weight of this shortcut fiber was added to and mixed with the matrix, and then the kneaded product was treated with 6i at a temperature of 80 ° C.
The sheet was formed using an nφ inverted L-type calendar. In this calender roll, the top two rolls have a gap of 8 mm, the speed is 3.7 and 4.3 m / min, the gap between the top roll and the center roll is 3 mm, and the center roll speed is 4.7 m / mi.
n and gap 15m between the center roll and the bottom roller
m, the bottom roll speed was adjusted to 4.8 / min. The shear rate between the top roll and the center roller at this time was 2.7 × 10 ⁻⁴ sec ^{−1 based} on the above conditions. This sheet had a thickness of 2.5 mm, a part of which was taken out, the rubber was dissolved with benzene, only the fiber was taken out, and the degree of fiber division and diameter reduction was observed with a microscope. This sheet was placed in a mold and press-vulcanized under the conditions of 150 ° C. for 15 minutes to obtain a fiber-reinforced rubber sheet having a thickness of 2 mm.

About this fiber reinforced rubber sheet, 100
(Vertical) × 55 (width) × 2 mm (thickness), cut by a tensile tester at 20 ° C and a speed of 20 mm / min.
The strain curve was determined, and the tensile fracture surface was observed using a scanning microscope. On the other hand, as a current technology and a comparative example, a 1200 denier / 400f yarn of 100% PVA and this yarn were subjected to a known RFL bonding treatment (RFL adhesion ratio of 5%).
%), A fiber reinforced rubber sheet was prepared and evaluated in the same manner, and the results are shown in Table 1. In addition, the obtained fiber No. In Nos. 3 and 4, PVA constituted the sea component and CA constituted the island component, and the fiber No. In 5, PVA is an island component,
CA was the sea component. In addition, the fiber No. 1 to N
o. The total draw ratio of 5 (wet draw ratio x dry heat draw ratio) is
As described above, the maximum draw ratio is 0.8 times, but the specific total draw ratio is No. 1-3 are 13 times, No. 4 is 10 times, No. 5 is 7 times, and No. In No. 6, it was not possible to obtain a proper fiber because the wet drawing of 3 times could not be performed.

[0020]

[Table 1]

Note 1 ・ Average diameter after fiber division: The fiber obtained by dissolving and removing the rubber from uncured rubber sheet using benzine was observed under a microscope, and the fiber diameter obtained by dividing the fiber by the method described above was calculated. I asked.・ Fracture surface: Observe the yarn / rubber interface at the fracture surface after the tensile test and display as follows: ○: No thread loss, ×: Almost all yarns are missing

[0022]

The present invention relates to reinforcement of a matrix typified by rubber with a single fiber, and when a fiber is added to the matrix, the dispersion is carried out at an aspect ratio of 30 to 1000 with good dispersibility. Utilizing the shear force of the fiber to split and reduce the diameter of the fiber, its extremely large surface area
The matrix and the fibers are firmly adhered to each other, and good matrix reinforcement can be obtained. For this reason, the chemical bonding treatment for fibers such as RFL and isocyanate, which is performed in the prior art, may be omitted, and the adhesiveness has an advantage that it is not greatly affected by the type of rubber.
As described above, the present invention can provide an innovative fiber material for a fiber-reinforced matrix that ensures good fiber dispersibility in a matrix and excellent adhesive strength. In this case, since no special process or treatment is required, the cost is superior to that of the prior art.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location C08L 1/10 LAN C08L 1/10 LAN 21/00 LAY 21/00 LAY // C08L 29/04 LGS 29/04 LGS (72) Inventor Kiyoshi Kitagawa 1-1239 Umeda, Kita-ku, Osaka City Kuraray Co., Ltd. (72) Inventor Eiichi Sasakawa 1-1239 Umeda, Kita-ku, Osaka City Kuraray Co., Ltd.

Claims (2)

[Claims] 1. A fiber which is used by being mixed and dispersed in the form of a short fiber in a matrix made of a rubber-like polymer, wherein the fiber is made of at least two kinds of polymers, and the cross section of the fiber has a sea-island shape. Fibers are short fibers for rubber reinforcement that are fibrillated by mechanical shearing force. 2. Polyvinyl alcohol polymer (A)
And a water-insoluble polymer (B). Either A or B is an island component, the other is a sea component, and the weight ratio of A / B is 90.
The short fiber for rubber reinforcement according to claim 1, which is / 10 to 20/80.