JPH08109581A - Production of aramide short fiber for reinforcing rubber - Google Patents

Abstract

PURPOSE: To obtain aramide short fibers enhanced in adhesivity to rubbers, capable of sufficiently exhibiting the original characteristics of the aramide fibers as the short fibers for reinforcing the rubbers, and used for reinforcing the rubbers. CONSTITUTION: The characteristics of this method for producing aramide short fibers for reinforcing rubbers comprise treating an aramide filament bundle with the first treating agent containing a polyepoxide compound, thermally treating the treated aramide filament bundle, treating the thermally treated bundle with the second treating agent containing a resorcinol-formalin-rubber latex (RFL), thermally treating the treated bundle, irradiating the bundle with 1-20 UV pulse laser light having a wavelength of 150-248 under a fluence condition of 10-150mJ/cm<2> as a pulse energy, and subsequently cutting the treated aramide filament bundle into the short fibers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to aramid short fibers for rubber reinforcement. The rubber reinforced with the aramid short fibers for rubber reinforcement of the present invention is used for a rubber belt for transportation and the like.

[0002]

2. Description of the Related Art Heretofore, in order to improve the mechanical properties of rubber belts and the like, it has been considered to mix and reinforce vulcanizable rubber with short fibers such as cellulose, vinylon, nylon and polyester. Among these short fibers, aramid short fibers are widely used as rubber-reinforcing short fibers because they are excellent in mechanical properties, fatigue resistance, heat resistance and chemical properties. However, since the aramid short fiber has a relatively inert surface, it has a low adhesive force with rubber and has poor dispersibility when compounded in rubber, and the excellent properties of the fiber are not sufficiently exhibited.

Generally, in order to improve the adhesion between aramid fiber and rubber, a method of activating the fiber surface and then treating with resorcin-formalin rubber latex (RFL) has been tried. For example, a method of performing RFL treatment after epoxy treatment or isocyanate treatment can be mentioned.
In general, such short fibers have a smooth surface and insufficient adhesion to rubber, so that the interface between rubber and short fibers is easily broken by a relatively low shearing force. Therefore, in the present situation, when the aramid short fibers are compounded with rubber, the excellent properties of the aramid fibers, particularly the mechanical properties, are not fully utilized. Further, even if it is pulled or bent, the interface is likely to be broken and the fatigue resistance is low. Therefore, depending on the application, reinforcing short fibers may rather shorten the life of the product.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to form a fine shape on the surface of an aramid fiber coated with an adhesive by an adhesive treatment so that a rubber is obtained. It is an object of the present invention to provide an aramid short fiber for reinforcing a rubber capable of enhancing the adhesive strength of, and sufficiently exhibiting the original excellent properties of the aramid fiber as a short fiber for reinforcing a rubber.

[0005]

That is, according to the present invention, "(Claim 1) A long aramid fiber bundle is treated with a first treatment agent containing a polyepoxide compound, heat treated, and then a second treatment containing resorcin-formalin rubber latex (RFL). Treatment with an agent, heat treatment, and then irradiation with ultraviolet pulsed laser light having a wavelength of 150 to 248 nm as pulse energy for 1 to 20 pulses under the condition of fluence of 10 to 150 mJ / cm ² , and then cut into short fibers. A method for producing aramid short fibers for rubber reinforcement, characterized in that

Aramid fibers are para-aramid fibers,
It is a meta-aramid fiber or a fiber made of a copolymer of each. Examples of the aromatic ring include a 1,4-phenylene group, a 1,3-phenylene group, a 4,4′-biphenylene group, a 1,5-naphthylene group, a 2,6-naphthylene group, and a 2,5-pyridylene group. I can mention,
Preferred is a 1,4-phenylene group. The aromatic ring is
For example, halogen group (eg chlorine, bromine, fluorine), lower alkyl group (methyl group, ethyl group, isopropyl group,
An n-propyl group), a lower alkoxy group (methoxy group, ethoxy group), a cyano group, an acetyl group, a nitro group and the like may be contained as a substituent. As a specific example, polyparaphenylene terephthalamide (manufactured by DuPont,
Kevlar, etc.), polymetaphenylene isophthalamide (manufactured by Teijin Limited, Conex, etc.), polyparaaminobenzamide, poly-3,4'-oxydiphenylene terephthalamide / polyparaphenylene terephthalamide copolymer (Teijin Ltd.) Manufactured by Technora, etc.), and fibers made of polyparaaminobenzhydrazide terephthalamito and the like.

The polyepoxide compound used in the first treating agent of the present invention is a compound containing 0.2 g equivalent or more of at least two epoxy groups in one molecule per 100 g of the compound, such as ethylene glycol, glycerol,
Reaction products of polyhydric alcohols such as sorbitol, pentaerythritol, and polyethylene glycol with halogen-containing epoxides such as epichlorohydrin, resorcin bis (4-hydroxyphenyl) dimethylmethane, phenol formaldehyde resin, resorcin
A reaction product of a polyhydric phenol such as formaldehyde resin and the halogen-containing epoxide, a polyepoxide compound obtained by oxidizing an unsaturated compound with peracetic acid or hydrogen peroxide, and the like. 4-epoxycyclohexene epoxide, 3,4-epoxycyclohexene methyl-3,4-epoxycyclohexene carboxylate, bis (3,4-epoxy-6-methyl-cyclohexylmethyl) adipate and the like can be mentioned. Of these, a reaction product of a polyhydric alcohol and epichlorohydrin, that is, a polyglycidyl ether compound of a polyhydric alcohol is preferable because it exhibits excellent performance. Such a polyepoxide compound is usually used as an emulsion. In order to prepare an emulsion or solution, for example, such a polyepoxide compound as it is, or one obtained by dissolving it in a small amount of solvent as necessary, a known emulsifier, for example, sodium alkylbenzenesulfonate, dioctylsulfosuccinate sodium salt, nonylphenol is used. Emulsify or dissolve using an ethylene oxide adduct or the like.

The first treating agent may contain a blocked polyisocyanate compound and a rubber latex. The blocked polyisocyanate compound used in the first treatment agent is an addition compound of a polyisocyanate compound and a blocking agent, and the heating causes the blocking component to be liberated to generate an active polyisocyanate compound. Examples of the polyisocyanate compound include triresin isocyanate, metaphenylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, triphenylmethane triisocyanate, and the like, or these polyisocyanates and two active hydrogen atoms. A terminal isocyanate group-containing polyalkylene obtained by reacting a compound having the above, for example, trimethylolpropane, pentaerythritol, etc., in a molar ratio in which the ratio of isocyanate group (-NCO) and hydroxyl group (-OH) exceeds 1. Examples thereof include glycol adduct polyisocyanate. In particular, aromatic polyisocyanates such as triresin isocyanate, diphenylmethane diisocyanate and polymethylene polyphenyl isocyanate are preferable because they exhibit excellent performance.

Examples of the blocking agent include phenols such as phenol, thiophenol, cresol and resorcinol, aromatic secondary amines such as diphenylamine and xylidine, phthalimides, caprolactam,
Examples include lactams such as valerolactam, oximes such as acetoxime, methyl ethyl ketone oxime and cyclohexane oxime, and acidic sodium sulfite.

Examples of the rubber latex used as the first treatment agent include natural rubber latex, styrene-butadiene copolymer latex, vinylpyridine-styrene-butadiene-terpolymer latex, nitrile rubber latex, chloroprene rubber latex, and the like.
These are used alone or in combination depending on the type of reinforcing rubber.

The second treating agent of the present invention is a composition containing resorcin / formalin / rubber latex, and the resorcin / formalin / rubber latex used here is usually called RFL. Any known formulation may be used. Examples of the rubber latex include natural rubber latex, styrene / butadiene / copolymer latex, vinylpyridine / styrene /
Butadiene terpolymer, chloroprene rubber latex, and the like are available, and these are used alone or in combination.

In order to adhere the first treatment agent and the second treatment agent to the aramid fiber bundle, any method such as application by a roller, application by spraying from a nozzle or immersion in a solution can be adopted. In order to control the amount of solids deposited on the fiber bundle, means such as squeezing with a pressure roller, scraping with a scraper, blowing with air, suction, and beating with a beater are used.

The amount of solids deposited on the aramid fiber is the first
The treating agent composition is 0.1 to 10% by weight, preferably 1 to 5% by weight, and the second treating agent composition is 0.5 to 1% by weight.
0% by weight, preferably 1-5% by weight. An aramid fiber bundle whose surface has been coated with an adhesive by an adhesive treatment, and before or after cutting 150 to 24 before or after cutting
Fluence of 10 to 150 mJ / cm ² with pulse energy of ultraviolet pulsed laser light having a wavelength of 8 nm
Irradiate 1 to 20 pulses under the conditions of. The ultraviolet laser light referred to in the present invention has a wavelength of 150 to 248 nm. In addition to lasers such as KrF and ArF, higher harmonic laser light such as copper vapor laser and YAG laser can be used. Particularly desirable is a KrF laser having a wavelength of 248 nm, Ar having a wavelength of 193 nm.
It is an F laser. There is no particular limitation on the laser light irradiation method. Irradiation may be carried out in air, in an inert gas, under pressure or in vacuum. The temperature during irradiation is preferably in the range of room temperature to 100 ° C. Irradiation fluence and the number of irradiation shots are important as irradiation conditions.
The irradiation fluence is usually desirably in the range of 10 to 500 mJ / cm ² pulse.

[0014]

EFFECTS OF THE INVENTION After the aramid long fiber bundle is subjected to an adhesive treatment and an adhesive is applied to the fiber surface, before or after cutting or before or after cutting, ultraviolet pulsed laser light having a wavelength of 150 to 248 nm is used as pulse energy for fluence. Irradiation with 1 to 20 pulses under the condition of 10 to 150 mJ / cm ² makes it possible to form a fine structure on the surface of the aramid short fiber and improve the adhesiveness to rubber. The fine structure of the short fiber surface has an anchoring effect and enhances the adhesiveness with rubber, and as a result, the excellent characteristics inherent to the aramid fiber as a short fiber for rubber reinforcement are fully exerted, and a mechanically excellent reinforcing effect. Express.

The present invention will be specifically described below with reference to examples. In the examples, the stress at yield point, elongation at break, and flex fatigue resistance are values determined as follows.

<Tensile Strength at Yield Point, Elongation at Break> This shows the reinforcing effect and elongation of rubber reinforced with short fibers. JIS
-Measure No.3 dumbbell-shaped test piece 500m according to K6301
m / min. The value obtained by dividing the load at the yield point when cutting at the tensile speed of 1 by the cross-sectional area of the test piece is the tensile strength at the yield point, and the elongation between the marked lines at the time of cutting is the breaking elongation.

<Bending Fatigue Life> This is one standard for judging the fatigue property of rubber reinforced with short fibers. Here, a Dematia flexural fatigue tester manufactured by Toyo Seiki Co., Ltd. was used to bend No. 3 dumbbell-shaped test piece by 25% at a cycle of 5 hz, and the number of cracks was displayed.

[0018]

Examples 1 to 3 and Comparative Examples 1 to 4 Para type aramid fibers (trade name: Technora, manufactured by Teijin Ltd.) were used for 10,000 to 9
The supply fibers were prepared by aligning the denier with a thickness of 100,000 denier. The adhesive was prepared as follows.

3.0 g of Denacol EX-611 (manufactured by Nagase & Co., Ltd., sorbitol polyglycidyl ether)
To the above, 2.5 g of Neocol SW-30 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., 30% aqueous solution of dioctyl sulfosuccinate sodium salt) is added and uniformly dissolved. This is added to 736.6 g of water with stirring to uniformly dissolve each agent in water. Then, 48 g of S-3 (manufactured by Meisei Chemical Industry Co., Ltd., 25% by weight water emulsion of lactam blocked isocyanate) was added and further stirred, and Nipol 2518GL (manufactured by Nippon Zeon Co., Ltd., vinylpyridine / styrene / butadiene terpolymer) was added. 40.5
209.9 g of water emulsion (weight%) is added and uniformly dissolved.
The obtained mixed liquid is used as the first treatment agent.

Also, 4.4 g of a 10% aqueous sodium hydroxide solution,
12.8 g of 28% aqueous ammonia solution was added to 143.6 g of water, and 17.7 g of a resorcinol / formalin initial condensate Sumikanol 700S (Sumitomo Chemical Co., Ltd., 65% aqueous solution) was added to the aqueous solution obtained by stirring well. Stir well to disperse. Next, Nipol 2518GL (Nippon Zeon Co., Ltd., vinyl pyridine / styrene / butadiene terpolymer water emulsion) 259.8 g and Nipol LX-112 (Nippon Zeon Co., Ltd., styrene / butadiene copolymer 40.5 water emulsion) 111 .4
g is diluted with 345.7 g of water. The above resorcinol-formalin initial condensation dispersion is slowly added to this diluted solution by stirring, and 13.7 g of formalin (37% aqueous solution) is further added and uniformly mixed. Next, 90.9 g of DM-6011 (manufactured by Meisei Chemical Co., Inc., diphenylmethane diisocyanate methyl ethyl ketoxime block 33% water dispersion liquid) was added to and mixed with this mixed liquid, and the obtained mixed liquid was used as a second treatment agent. .

The supplied fiber is dipped in the first treatment agent and heated to 130 ° C.
And then heat-treated at 240 ° C., further immersed in the second treatment agent in the same manner as described above, dried and heat-treated to obtain a fiber bundle to which an adhesive is applied by surface treatment. . An excimer laser generator (LP120cci) manufactured by Lambda Physics Co., Ltd. was used for the fiber bundle, KrF (oscillation wavelength 248 nm) was used, the repeating wave number was 1 HZ, and the fluence was 10 to 150 mJ / cm ^2.
And the pulse width was 20 ns at the full width at half maximum, and the fiber bundle surface was directly irradiated uniformly. Next, the fiber bundle irradiated with the excimer laser is cut into a predetermined fiber length with a guillotine cutter to obtain a rubber-reinforcing short fiber. This is assumed to be with excimer laser irradiation. As a comparative example, the fiber bundle to which the adhesive is applied by the surface treatment is not irradiated with the excimer laser, and the short fiber for rubber reinforcement obtained by cutting into a predetermined fiber length is not irradiated with the excimer laser. The obtained short fiber,
Short fibers were mixed in an amount of 5 or 10% by weight into natural rubber or rubber containing styrene butadiene as a main component, and kneaded using an MS pressure type kneader (DS3-10 MHHS, manufactured by Moriyama Seisakusho Co., Ltd.). A sheet was taken out to an appropriate thickness so that the short fibers were oriented, a rubber sheet was made by press vulcanization, and a sample was cut out in the orientation direction of the short fibers and used for performance evaluation. Examples 1 to 3 of the present invention, Comparative Examples 1 to 4
Table 1 shows the characteristics and bending fatigue resistance of the short fiber reinforced rubber.

[0022]

[Table 1]

Comparative Examples 1 to 3 are compared with Examples 1 to 3,
Low tensile strength at yield and short bending fatigue life. Comparative Example 4
Since the adhesion amount of the first treatment agent is low, the tensile strength at the yield point is low, and the yield point of the tensile strength disappears after bending fatigue 100,000 times, so that the reinforcing effect of the short fiber is lost.

Claims (1)

[Claims] 1. A long aramid fiber bundle is treated with a first treating agent containing a polyepoxide compound, heat treated, and then a second containing resorcin-formalin rubber latex (RFL).
Treated with treating agent, heat treated, then 150-248n
Production of aramid staple fiber for rubber reinforcement, which comprises irradiating 1 to 20 pulses of ultraviolet pulse laser light having a wavelength of m as pulse energy under the condition of fluence of 10 to 150 mJ / cm ² , and then cutting into short fibers. Method.