JP2005194668A - Rubber-reinforcing polybenzazole dipped cord and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber-reinforcing polybenzazole dipped cord in which the adhesive force between polybenzazole short fiber and rubber is increased dispersability with the rubber and can sufficiently develop the intrinsically excellent properties of a polybenzazole fiber as a short fiber for reinforcing rubber. <P>SOLUTION: Continuous fiber bundles of substantially untwisted polybenzazole fiber are dipped in the first treatment solution mainly comprising an epoxy compound bearing two or more epoxy groups in a monomer molecule and blocked isocyanate solution having thermal dissociation point of 100 to 200°C, then dried, heat-treated and then dipped in the second treatment solution including resorcin-formaldehyde-rubber latex (RFL) mixed solution, then dried, heat-treated and cut, whereby rubber-reinforcing polybenzazole dipped cords are obtained that have good adhesion to rubber and shows good dispersion into the rubber. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rubber-reinforced polybenzazole dip cord and a method for producing the same. The rubber-reinforced polybenzazole dip cord produced by the method of the present invention is used as a rubber reinforcing fiber for tires, belts, vibration-proof rubbers and the like.

Conventionally, in order to improve the mechanical properties and wear resistance of tires, belts, vibration-proof rubbers, etc., it has been studied to add and reinforce short fibers such as nylon, polyester, and aramid in rubber. Of these short fibers, polybenzazole short fibers are excellent in mechanical properties, heat resistance and wear resistance, and thus are expected as short fibers for rubber reinforcement. However, polybenzazole short fibers are relatively inactive on the surface and therefore have insufficient adhesion to rubber. In addition, the dispersibility when blended with rubber was poor, and there was a problem that the excellent properties of the fiber were not sufficiently exhibited due to the generation of fiber balls in which short fibers were entangled with each other.
A polybenzazole twisted yarn cord that is lightweight and has excellent fatigue resistance is also known (see, for example, Patent Document 1).
JP-A-6-294036

  The present invention has been made against the background of the above circumstances, and increases the adhesive force with rubber by activating the surface of each single fiber of a polybenzazole fiber bundle that is not substantially twisted. Along with this, we provide a polybenzazole dip cord for rubber reinforcement that can improve the dispersibility of polybenzazole short fibers in rubber and fully demonstrate the original properties of polybenzazole fibers as a short fiber for rubber reinforcement. There is to do.

That is, the present invention has the following configuration.
1. A polybenzazole for reinforcing rubber having a ratio of bundle width L to fineness D (L / D ^0.5 ) of 28 or more and a substantially non-twisted polybenzazole fiber bundle to which a treatment liquid is applied Zole dip code.
2. The treatment liquid is mainly composed of an epoxy compound having two or more epoxy groups in one monomer molecule as a first treatment liquid and a blocked isocyanate aqueous solution, and resorcin, formaldehyde, rubber latex (RFL) as a second treatment liquid. The rubber-reinforced polybenzazole dip cord as described in the above item 1, which is a mixed solution.
3. 2. The polybenzazole dip cord for rubber reinforcement as described in 1 above, wherein the blocked isocyanate is water-soluble and the thermal dissociation temperature of the blocking agent component is 100 ° C. to 200 ° C.
4). 2. The rubber-reinforced polybenzazole dip cord according to claim 1, wherein the polybenzazole fiber contains an organic pigment that dissolves in a mineral acid having a thermal decomposition temperature of 200 ° C. or higher.
5). The rubber-reinforced polybenzazole dip cord according to the first aspect, which is cut.
6). A substantially untwisted polybenzazole continuous fiber bundle is impregnated in a first treatment liquid mainly composed of an epoxy compound having two or more epoxy groups in one monomer molecule and a blocked isocyanate aqueous solution, followed by drying and heat treatment. And then impregnating a second treatment solution containing a resorcin / formaldehyde / rubber latex (RFL) mixed solution, drying, heat-treating, and then cutting the rubber-reinforced polybenzazole dip cord.

  The present invention improves the adhesive force between polybenzazole short fibers and rubber, has good dispersibility with rubber, and sufficiently exhibits the original properties of polybenzazole fibers as a short fiber for rubber reinforcement. Since a polybenzazole dip cord for rubber reinforcement can be easily produced industrially, it is useful as a rubber reinforcing fiber for tires, belts, anti-vibration rubbers and the like.

Hereinafter, the present invention will be described in detail.
That is, in the present invention, the polybenzazole continuous fiber bundle is impregnated in a first treatment liquid containing an epoxy compound, dried and heat-treated, and then impregnated in a second treatment liquid containing a resorcin / formaldehyde / rubber latex (RFL) mixed solution. It is characterized by cutting after drying, heat treatment, and the bundle width L [μm] and the fineness D [dtex] of the polybenzazole fiber bundle that has been subjected to the adhesion treatment before cutting and is not substantially twisted The ratio of the square root (L / D ^0.5 ) is 28 or more.
That is, when a polybenzazole continuous fiber bundle is treated with an adhesive, the fiber bundle is kept as flat as possible and the specific surface area is increased, so that the treatment agent is uniformly applied to each single fiber constituting the fiber bundle. It has been found that the dispersion can be uniformly dispersed when dispersed in the rubber while maintaining sufficient adhesive strength with the rubber. As a result, it is possible to obtain rubber-reinforcing polybenzazole short fibers that can sufficiently exhibit the inherent mechanical properties, heat resistance, and wear resistance of the polybenzazole fibers.

 In the present invention, the polybenzazole fiber (PBZ) refers to polybenzoxazole (PBO) homopolymer, polybenzothiazole (PBT) homopolymer, random, sequential or block copolymer of PBO and PBT.

  As the epoxy compound used in the present invention, a known epoxy compound can be used as long as it has two or more epoxy groups in the molecule. For example, reaction products of polyhydric alcohols such as glycerol, pentaerythritol, sorbitol, ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol and halogen-containing epoxides such as epichlorohydrin, resorcin, bis (4-hydroxyphenyl) Reaction product of polyhydric phenols such as dimethylmethane, phenol / formaldehyde resin, resorcin / formaldehyde resin and the above halogen-containing epoxides, bis (3,4-epoxy-6-methyl-dicyclohexylmethyl) adipate, 3,4 -The polyepoxide compound etc. which are obtained by oxidizing unsaturated bond parts, such as an epoxy cyclohexene epoxide, are mentioned. Among them, sorbitol polyglycidyl ether, diglycerol polyglycidyl ether, and glycerol polyglycidyl ether are preferable.

  Although the component of the blocked isocyanate used in the present invention is not particularly limited, polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and hexamethylene isocyanate as the isocyanate component, phenols, alcohols, oximes, lactams as the blocking agent component, etc. As the hydrophilic component for water-solubilization, a carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, a hydroxyl group, an amide group, or the like is applied.

  Latex or the like can be appropriately added to the first treatment liquid used in the present invention.

  The adhesion amount of the first treatment liquid is 0.3 to 5 wt%, preferably 0.5 to 3 wt% on a solid basis after drying with respect to the polybenzazole continuous fiber bundle. If the amount of adhesion is small, sufficient adhesion cannot be obtained, and if the amount of adhesion is too large, the second treatment liquid adheres only to the periphery of the fiber bundle and cannot adhere to the inner single fiber, dispersibility and adhesion with rubber. The nature will decline.

  After the first treatment liquid is attached to the polybenzazole fiber under the above conditions, it is dried at 100 to 150 ° C. and then heat-treated at 160 to 260 ° C., preferably 240 to 260 ° C.

  The polybenzazole continuous fiber bundle treated with the first treatment liquid is then treated with an RFL liquid that is widely used as an adhesive between fibers and rubber. The RFL liquid used in the present invention is an initial condensate (RF) obtained by reacting resorcin (R) and formalin (F) in the presence of an acid or alkali catalyst, styrene / butadiene copolymer latex, and carboxyl group-containing S / B copolymer latex, acrylonitrile / butadiene copolymer latex, polychloroprene latex, polybutadiene latex, mixed water dispersion with one or more latexes (L) such as natural rubber latex, R / F (Molar ratio) is preferably in the range of 1 / 0.5 to 1/4, and RF / L (solid content ratio) is preferably in the range of 5/95 to 50/60. Furthermore, adhesiveness is further improved by adding an epoxy compound, blocked isocyanate, etc. suitably to a 2nd process liquid.

  The application method of the RFL liquid can be applied by the same method as the first treatment liquid. The amount of the RFL solution applied to the polybenzazole fiber is 2 to 15 wt%, preferably 4 to 10 wt%. If the amount of adhesion is too small, the adhesion will be poor, and if it is too large, stickiness will become severe and workability will be deteriorated, resulting in a decrease in productivity and a decrease in quality. The treated polybenzazole fiber is dried at 100 to 150 ° C. and heat-treated at a temperature of 160 to 260 ° C., preferably 230 to 260 ° C.

  In order to attach the first treatment agent and the second treatment agent to the polybenzazole fiber bundle which is not substantially twisted, any method such as application by a roller, application by spraying from a nozzle, or immersion in a solution is adopted. can do. In order to control the amount of solid content attached to the fiber bundle, means such as squeezing with a pressure roller, scraping with a scraper, blowing by air blowing, suction, hitting with a beater, etc. may be used.

The first treatment agent, when the continuous fiber bundle imparted with the second treatment agent drying and heat treatment, 0.1~5.0kg / cm ² using a roller, preferably at a pressure of 0.5~2.0kg / cm ² By processing while pressing, it is possible to dry and heat-treat with the treatment agent uniformly attached without disturbing the alignment of the single fibers in the fiber bundle.

As a result of diligent examination of the state of dispersion in rubber, the ratio of the bundle width L to the fineness D (L / D ^0.5 ) of the polybenzazole fiber bundle that has undergone the adhesive treatment before cutting and is not twisted is 28 or more. It has been found that the dispersibility with rubber is remarkably improved by controlling to a maximum, and the reinforcing effect by the polybenzazole fiber can be exhibited to the maximum. In order to make the ratio (L / D ^0.5 ) of the bundle width L and the fineness D of the polybenzazole fiber bundle substantially untwisted to 28 or more, the adhesive reaches a viscosity at which the single fiber is fixed by heat treatment. Previously, in the case of polybenzazole fibers, it has been found that by applying a tension of less than 2 cN / dtex, a flat state can be maintained without disturbing the alignment of the single fibers. From the viewpoint of process passability, it is preferably 0.1 cN / dtex or more, and more preferably, the applied tension is 0.2 cN / dtex or more and 1 cN / dtex or less.

 The cut length of the polybenzazole continuous fiber bundle treated as described above is preferably cut into a range of 0.3 to 10.0 mm. 0.5 to 6.0 mm is particularly desirable. If the thickness is less than 0.3 mm, the reinforcing effect is insufficient, and if it is 10.0 mm or more, fibers are entangled with each other, resulting in a fiber ball or the like.

  The polybenzazole short fibers obtained in this way have good dispersibility in rubber and good adhesion to rubber. It can be demonstrated.

  As the organic pigment having a high heat resistance of 200 ° C. or higher and dissolved in a mineral acid in the present invention, any organic pigment that is added to the polymer during the polymerization or in the polymer dope and remains in the fiber after spinning may be used. Specific examples include insoluble azo pigments, condensed azo pigments, dye lakes, isoindolinones, isoindolines, dioxazines, perinones and / or perylenes, phthalocyanines, quinacridones, and the like. Among them, those having —N═ and / or NH— group in the molecule are preferable, and perinone and / or perylenes, phthalocyanines, and quinacridones are more preferable.

Perinones and / or perylenes include bisbenzimidazo [2,1-b: 2 ′, 1′-i] benzo [lmn] [3,8] phenanthroline-8,17-dione, bisbenzimidazo [2, 1-b: 1 ′, 2′-j] benzo [lmn] [3,8] phenanthroline-6,9-dione, 2,9-bis (p-methoxybenzyl) anthra [2,1,9-def: 6,5,10-d'e'f '] diisoquinoline-1,3,8,10 (2H, 9H) -tetron, 2,9-bis (p-ethoxybenzyl) anthra [2,1,9-def: 6,5,10-d'e'f '] diisoquinoline-1,3,8,10 (2H, 9H) -tetron, 2,9-bis (3,5-dimethylbenzyl) anthra [2,1,9- def: 6,5,10-d'e'f '] diisoquinoline-1,3,8 , 10 (2H, 9H) -tetron, 2,9-bis (p-methoxyphenyl) anthra [2,1,9-def: 6,5,10-d'e'f '] diisoquinoline-1,3,8 , 10 (2H, 9H) -tetron, 2,9-bis (p-ethoxyphenyl) anthra [2,1,9-def: 6,5,10-d'e'f '] diisoquinoline-1,3,8 , 10 (2H, 9H) -tetron, 2,9-bis (3,5-dimethylphenyl) anthra [2,1,9-def: 6,5,10-d'e'f '] diisoquinoline-1,3 , 8,10 (2H, 9H) -tetron, 2,9-dimethylanthra [2,1,9-def: 6,5,10-d'e'f '] diisoquinoline-1,3,8,10 (2H , 9H) -Tetron, 2,9-bis (4-phenylazophenyl) anthra [2,1, -def: 6,5,10-d'e'f '] Jiisokinorin 1,3,8,10 (2H, 9H) - Tetron, 8,16- pin lance range on the like.
There may be a combination of one or more compounds of these perinones.

As for the phthalocyanines, the presence or absence of a metal coordinated at the center and the atomic species are not limited as long as it has a phthalocyanine skeleton. Specific examples of these compounds include 29H, 31H-phthalocyaninate (2-)-N29, N30, N31, N32 copper, 29H, 31H-phthalocyaninate (2-)-N29, N30, N31, N32 iron, 29H, 31H-phthalocyaninate-N29, N30, N31, N32 cobalt, 29H, 31H-phthalocyaninate (2-)-N29, N30, N31, N32 copper, oxo (29H, 31H-phthalate Russian titanate (2-)-N29, N30, N31, N32), (SP-5-12) titanium and the like. These phthalocyanine skeletons may have one or more substituents such as a halogen atom, a methyl group, and a methoxy group.
There may be a combination of one or more compounds of these phthalocyanines.

As quinacridones, 5,12-dihydro-2,9-dimethylquino [2,3-b] acridine-7,14-dione, 5,12-dihydroquino [2,3-b] acridine-7,14-dione, 5, Examples include 12-dihydro-2,9-dichloroquino [2,3-b] acridine-7,14-dione, 5,12-dihydro-2,9-dibromoquino [2,3-b] acridine-7,14-dione, and the like.
There may be a combination of one or more compounds of these quinacridones.

Also, two or more compounds of perylenes, perinones, phthalocyanines and quinacridones can be used in combination.
Of course, the technical contents of the present invention are not limited to these.

  The method for containing these organic compounds in the yarn is not particularly limited, and can be contained in any stage of polymerization of polybenzazole or in the stage of polymer dope at the end of polymerization. For example, a method of adding an organic pigment at the same time as the raw material of polybenzazole, a method of adding the organic pigment at a stepwise or arbitrary temperature rising rate and reacting at any time, and a reaction at the end of the polymerization reaction A method of adding to the system and stirring and mixing is preferable.

Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited by the following examples, but may be implemented with appropriate modifications within a range that can meet the gist of the preceding and following descriptions. Of course, it is also possible and they are all included in the technical scope of the present invention.
<Tensile strength, elongation at break>
In order to examine the reinforcing effect of rubber reinforced by dispersing short fibers, a No. 3 dumbbell-shaped test piece was measured at 500 mm / min. According to JIS-K6301. The tensile strength and elongation at break were measured.
<Dispersibility evaluation>
After blending short fibers in unvulcanized rubber mainly composed of SBR rubber that does not contain carbon black, kneading with a pressure kneader for 5 minutes, sandwiching it in a transparent acrylic plate, about 1mm in thickness with a press It was. This was visually evaluated to evaluate dispersibility.

(Examples 1-3, Comparative Examples 1-2)
Polybenzazole fiber 3270 dtex was used as the supply fiber, and each of the two dip treatments was performed to obtain a dip-treated continuous fiber bundle. As the first stage dip treatment, dip in a mixture of an aqueous dispersion of sorbitol / polyglycidyl ether and an aqueous polyurethane prepolymer block (30% solids, approximately 5 functional groups), then 120 ° C. × 1 minute Drying and heat treatment at 240 ° C. for 1 minute were performed. As the second-stage dip treatment, immersion in an RFL solution was performed, followed by drying at 120 ° C. for 1 minute and heat treatment at 240 ° C. for 1 minute. The dip-treated continuous fiber bundle thus obtained was cut into 3 mm with a guillotine cutter.
(Example 4, Comparative Example 3)
Polybenzazole fiber 3270 dtex was used as the supply fiber, and each of the two dip treatments was performed to obtain a dip-treated continuous fiber bundle. As the first-stage dip treatment, it was immersed in an aqueous dispersion of sorbitol / polyglycidyl / ether, then dried at 120 ° C. for 1 minute, and then heat-treated at 240 ° C. for 1 minute. As the second-stage dip treatment, immersion in an RFL solution was performed, followed by drying at 120 ° C. for 1 minute and heat treatment at 240 ° C. for 1 minute. The dip-treated continuous fiber bundle thus obtained was cut into 3 mm with a guillotine cutter.
At that time, the dip treatment conditions were variously changed as shown in Table 1.

  The obtained short fibers were mixed with 5 wt% of short fibers in an unvulcanized rubber mainly composed of SBR rubber, and kneaded for 5 minutes by a pressure kneader. Sheeting was performed so that the thickness was 1.8 mm, and press vulcanization (140 ° C. × 40 minutes) was performed to produce a rubber sheet.

  Table 2 shows the properties of the short fiber reinforced rubber and the dispersibility of the short fibers in the rubber. In the comparative example, the dispersibility is poor and the reinforcing effect is not sufficient, whereas in the examples, the dispersibility is good and the reinforcing effect is exhibited.

  The polybenzazole dip cord according to the present invention improves the adhesive force between the polybenzazole short fibers and the rubber, has good dispersibility with the rubber, and has excellent properties inherent to the polybenzazole fibers as a short fiber for rubber reinforcement. Therefore, it is useful as a rubber reinforcing fiber for tires, belts, anti-vibration rubbers and the like.

Claims (6)

A polybenzazole for reinforcing rubber having a ratio of bundle width L to fineness D (L / D ^0.5 ) of 28 or more and a substantially non-twisted polybenzazole fiber bundle to which a treatment liquid is applied Zole dip code.   The treatment liquid is mainly composed of an epoxy compound having two or more epoxy groups in one monomer molecule as a first treatment liquid and a blocked isocyanate aqueous solution, and resorcin, formaldehyde, rubber latex (RFL) as a second treatment liquid. 2. The polybenzazole dip cord for reinforcing rubber according to claim 1, which is a mixed solution.   The polybenzazole dip cord for rubber reinforcement according to claim 1, wherein the blocked isocyanate is water-soluble, and the thermal dissociation temperature of the blocking agent component is 100 ° C to 200 ° C.   2. The polybenzazole dip cord for rubber reinforcement according to claim 1, wherein the polybenzazole fiber contains an organic pigment dissolved in a mineral acid having a thermal decomposition temperature of 200 ° C. or higher. The polybenzazole dip cord for rubber reinforcement according to claim 1, which is cut.   A substantially untwisted polybenzazole continuous fiber bundle is impregnated in a first treatment liquid mainly composed of an epoxy compound having two or more epoxy groups in one monomer molecule and a blocked isocyanate aqueous solution, followed by drying and heat treatment. And then impregnating a second treatment solution containing a resorcin / formaldehyde / rubber latex (RFL) mixed solution, drying, heat-treating, and then cutting the rubber-reinforced polybenzazole dip cord.