JPH03220368A - Treatment of aromatic polyamide fiber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for treating aromatic polyamide fibers with improved adhesion to rubber. In particular, the present invention has a high adhesive strength, an improved rubber coverage on aromatic polyamide fibers when the aromatic polyamide fibers are peeled from a rubber composite molded product, and is flexible and has excellent fatigue resistance. The present invention relates to a processing method for providing aromatic polyamide fibers.

<Prior art> Aromatic polyamide fibers generally have high tensile strength and elastic modulus, as well as excellent dimensional stability and heat resistance, so they are used in tires, conduction belts, belts, hoses, etc. that are used under harsh conditions. Suitable as a reinforcement material for rubber products. However, aromatic polyamide fibers are inert due to their molecular structure and are highly crystalline, so they have poor adhesion to rubber and are usually used as an adhesive between aliphatic polyamide fibers and rubber. If resorcinol formalin latte sox (RFL) is used as it is, it has the disadvantage that it cannot form strong adhesion to rubber. Therefore, many proposals have been made in an attempt to improve the adhesiveness between aromatic polyamide fibers and rubber. For example, a method of adhering aromatic polyamide fibers to rubber by subjecting them to epoxy treatment, heat treatment, RFL treatment, and heat treatment (Japanese Patent Publication No. 39-10514);
A method in which aromatic polyamide fibers are treated with a treatment liquid consisting of an epoxy compound and rubber latex, followed by RFL treatment and heat treatment (Japanese Patent Publication No. 37467/1983), a method in which aromatic polyamide fibers are subjected to low-temperature plasma treatment, A method for treating aromatic polyamide fibers for rubber reinforcement, which is characterized by treating with a mixture of a resorcinol-formaldehyde initial condensate and rubber latex (Japanese Unexamined Patent Application Publication No. 1988-1981), the surface of the aromatic polyamide fibers is depressurized. The treated fibers are then treated with a resorcinol-formaldehyde initial condensate and a rubber latte...
A method for adhering aromatic polyamide fibers and rubber, characterized by adhesion treatment with an adhesive composition consisting of
JP-A No. 60-250036), etc.

However, aromatic polyamide fibers treated with these conventional methods have a low adhesion rate of rubber to the fiber material when the fiber material is peeled from a rubber composite molded product, and the adhesiveness between the aromatic polyamide fiber material and rubber is poor. This has been a major hindrance to the use of aromatic polyamide fibers for rubber reinforcement because of the problem that sufficient adhesive strength cannot be obtained.

<Object of the invention> The present invention was made against the background of the above circumstances,
The purpose of the present invention is to improve adhesion to rubber and fatigue resistance by subjecting the surface of aromatic polyamide fibers to low-temperature plasma treatment and then treating them with a treatment agent containing a blocked polyisocyanate compound and resorcinol, formalin, and rubber latex. It's about forcing.

<Synopsis of the invention> That is, the present invention is characterized in that (1) aromatic polyamide fibers are treated with a treatment agent containing a low-temperature plasma-treated fiber, a pro-sodium polyisocyanate compound, and resorcinol, formalin, and rubber latex. Processing method for aromatic polyamide fibers.

2. The method for treating aromatic polyamide fibers according to claim 1, wherein the amount of the blocked polyisocyanate compound contained in the i2+ m matrix is 0.5 to 30% by weight based on the resorcinol formalin rubber latex.

(3) The blocked polyisocyanate compound has the general formula % (R is an organic residue selected from the group consisting of aromatic, aliphatic, and araliphatic, X is a blocking agent residue liberated by heat treatment, n The method for treating aromatic polyamide fibers according to claim 1 or 2, wherein the compound is a compound represented by the following formula (integer of 2 or more).

The aromatic polyamide fiber in the present invention means a fiber made of a polymer in which repeating units having an aromatic ring account for at least 80% or more of the total fiber.

For example, fibers made of a polymer or copolymer of one or more repeating units represented by the following general formula can be mentioned.

Here, R1 and R2 may be the same or different and are a hydrogen atom or an alkyl group having 5 or less carbon atoms.

Examples of the alkyl group having 5 or less carbon atoms include a methyl group, ethyl group, propyl group, butyl group, and pentyl group, but preferably a hydrogen atom. Further, as Ar, -C=-Y-O- can be exemplified. In addition, -X- is -03--N
It is a group derived from -, preferably -0N-, and more preferably 10-.

Y- is -0- O2 H2 represents an alkyl group having 5 or less carbon atoms. )-〇0-. Ar' represents an aromatic ring. Examples of aromatic rings include 1,4-phinidine group, ■, 3-phenylene group, 4,4
'-biphenylene group, ■, 5-naphthylene group, 2.6-
Examples include a naphthylene group and a 2.5-pyridylene group, but a 1.4-phenylene group is preferably selected.

Aromatic rings include, for example, halogen groups (e.g. chlorine, bromine, fluorine), lower alkyl groups (methyl group, ethyl group, isopropyl group, n-propyl group), lower alkoxy groups (methoxy group, ethoxy group), cyano group, It may contain an acetyl group, a nitro group, etc. as a substituent.

Typical examples of fibers made of these polymers or copolymers include polyparaaminobenzamide, polyparaphenylene terephthalamide, polyparaaminobenzhydrazide terephthalamide, polyterephthalic acid hydrazide, polymetaphenylene isophthalamide, etc. Examples include fibers made of copolymers of

The treatment of the present invention can be carried out by forming the aromatic polyamide fiber into any form such as yarn, cord, fabric (sudare), etc. For example, the yarn may be subjected to low-temperature plasma treatment, then made into a cord or woven fabric, and then treated with a treatment agent, or the cord form may be subjected to low-temperature plasma treatment, and then the woven fabric is treated with a treatment agent. . However, the most preferable method is to perform low-temperature plasma treatment immediately before treatment with the treatment agent.2 In other words, the surface of the aromatic polyamide fiber activated by low-temperature plasma treatment is not contaminated in the subsequent process.
In addition, a great effect can be obtained by treating with a treatment agent while the activation changes over time are slight.

In the present invention, low-temperature plasma processing refers to processing using audio wave, high frequency, or microwave energy in various gas atmospheres and under reduced pressure conditions of 10-5 to 10 Torr.
This refers to a treatment for activating the surface by creating an ionized state and exposing the aromatic polyamide fibers to an ionized state. More specifically, non-polymerizable argon, helium, neon, nitrogen, oxygen, air, ammonia, carbon oxide, carbon dioxide, hydrogen, sulfur dioxide gas, nitrogen oxide, formaldehyde,
Examples include hydrogen chloride, and examples of polymerizable gas include methane,
Examples include ethane and tetrafluoromethane. Examples of the vaporized gas include carbon tetrachloride, water, methylamine, aqueous ammonia, and water vapor. These gases can be used alone or as a mixture of two or more types. The gas pressure during low temperature plasma treatment is 1O-5
A range of Torr to 10 Torr is preferred. If the gas pressure exceeds IQ Torr, the temperature rise during plasma treatment will significantly alter the surface of the aromatic polyamide fiber, which may impair the treatment effect, which is not preferable. On the other hand, 1
If the gas pressure is less than 0-' Torr, a stable plasma state cannot be obtained, making it difficult to perform normal processing. Further, there is no particular restriction on the structure of the electrode for generating low-temperature plasma, and various shapes such as rod, flat, ring, etc. can be used. There are also internal electrode types in which the electrodes are installed inside the processing tank, external electrode types in which the electrodes are installed outside the processing tank, and further types such as the one-coupled type and the inductively coupled type. Based on the results of previous studies, the reason why low-temperature plasma treatment of aromatic polyamide fiber improves its adhesion to rubber is thought to be as follows.

First, by subjecting aromatic polyamide fibers to low-temperature plasma treatment, hydrophilic groups are generated on the fiber surface, which improves the wettability to water-based treatment agents such as RFL and % physical agents. It is presumed that this is because it has become possible to attach it to This improves the resistance to distortion between the fibers and the treatment agent layer due to the heat applied during the vulcanization process with rubber, and also allows the external stress applied after molding to pass through the rubber layer, allowing the treatment agent and fibers to This is thought to be due to the fact that the stress is evenly distributed without being concentrated on the adhesive defect area.

The generation of hydrophilic groups on the surface of aromatic polyamide fibers means that
It can be estimated from the fact that the ratio of the polar force component to the dispersion component of the surface tension, calculated from the contact angle of water, formamide, methylene iodide, etc. with the fiber using the extended Fowkes equation, is increased compared to the untreated fiber. Furthermore, as a result of analysis by ESCA, Ois/Cis, N
This is evident by the increasing ratio of is/Cis, especially Ois/'Cis. The second presumed reason for the improvement in adhesive strength is thought to be the effect of plasma etching. The effect of etching varies depending on conditions such as the seed layer of the fiber, the distance of the fiber from the electrode, the type of gas, the gas pressure, the discharge output, and the fiber tension during treatment, but the plasma treatment can cause the fiber surface to become splattered or tattered. , unevenness called a seashore structure appears in the direction perpendicular to the fiber axis.

It is thought that this increases the contact area between the treatment agent and the fibers and improves the apparent adhesive strength due to the anchor effect. The third is Wea by plasma treatment.
Removal of k boundary layer can be considered. It is thought that the plasma treatment can sputter and scrape off the weakly bonded layer on the fiber surface, or form a crosslinked layer on the fiber surface to strengthen the surface layer. This can prevent adhesive failure on the fiber surface layer,
3 out of 5 that seems to be able to improve adhesive strength
This is thought to be the reason why plasma treatment of aromatic polyamide fibers can improve their adhesion to rubber, but as a result of plasma treatment, even if surface etching and surface crosslinking are not observed, the adhesion strength is significantly improved. This suggests that the first probable cause has a large effect.

The probable cause of the improvement in fatigue resistance in rubber by treating aromatic polyamide fibers with a treatment agent containing RFL after plasma treatment is the uniform adhesion of the treatment agent by plasma treatment and the increase in the amount of treatment agent into the fiber bundle. It is presumed that this lick improves the permeability of the treatment agent.

It is thought that due to the uniform adhesion of the treatment agent, external stress is uniformly propagated to the fibers through the rubber layer and the treatment agent layer, so that stress is not concentrated on a certain part of the fibers. Furthermore, the plasma treatment allows the treatment agent to penetrate into the fiber bundle and coat the surface of each single fiber. Aromatic polyamide fibers tend to fibrillate when fishing on a boat, and as the fibers become fibrillated and wear away due to friction between the fibers, their strength decreases. However, due to plasma treatment, as mentioned above, the single fiber surface inside the fiber bundle is also coated with the treatment agent.
It is thought that abrasion on the fiber surface can be prevented and fatigue resistance in the rubber can be improved. However, when aromatic polyamide fibers are treated with the above-mentioned plasma-treated fibers or a simple RFL treatment agent, the adhesion performance between the fibers and rubber is insufficient and cannot be put to practical use. As a result of intensive investigation into various combinations of plasma treatment and adhesives, we found that by treating plasma-treated aromatic polyamide fibers with an RFL treatment agent containing blocked polyisocyanate, the adhesion to rubber was dramatically improved. Find ways to improve.

The reason for this is not clear, but the active polyisocyanate compound, whose block components are liberated by heating, reacts with the 10H groups, -COOH groups, etc. on the surface of the aromatic polyamide fibers generated by plasma treatment, and becomes strong. It is presumed that this is to combine.

The processing agent used in the method of the present invention is a composition containing resorcinol/formalin/rubber latex and a blocked polyisocyanate compound, and the resorcinol/formalin/rubber latex used here is usually called RFL. The molar ratio of resorcinol and formaldehyde is 0.1 to 1:8, preferably 1:0.5.
The ratio is preferably 1:1 to 1:5, more preferably 1:1 to 1:4.

Examples of rubber latex include natural rubber latex,
There are styrene-butadiene copolymer latex, vinylpyridine-styrene-butadiene terpolymer latex, nitrile rubber latex, chloroprene rubber latex, etc., and these can be used alone or in combination. Among these, vinylpyridine, styrene, butadiene,
The best performance is shown when terpolymer latex is used alone or in combination in half or more.

The blending ratio of resorcinol/formalin and rubber latex depends on the addition ratio of blocked polyisocyanate, but the solid content weight ratio is 1=1 to 1:15, preferably 1:3.
The ratio is preferably in the range of 1:12 to 1:12.

If the proportion of rubber latex is too low, the treated aromatic polyamide fiber material will become hard and have poor fatigue resistance.
On the other hand, if the amount is too large, satisfactory adhesive strength and rubber adhesion rate cannot be obtained.

The blocked polyisocyanate compound is added in an amount of 0.5 to 30% by weight, preferably 1.0 to 20% by weight, based on the RFL. If the amount of the blocked polyisocyanate compound added is too small, good adhesive strength and rubber adhesion rate cannot be obtained. On the other hand, if the amount added is too large, the viscosity of the treatment bath increases significantly, making it difficult to process the fiber material, and in addition, the adhesive strength and rubber adhesion rate reach saturation, making it necessary to increase the amount of the blocked polyisocyanate compound added. However, there is a disadvantage that the effect is not improved and the cost increases, and furthermore, the treated fiber material becomes extremely hard and its strength decreases.

A blocked polyisocyanate compound is an addition compound of a polyisocyanate compound and a blocking agent, and when heated, the blocking component is liberated to produce an active polyisocyanate compound. isocyanate,
Polyisocyanates such as metaphenylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, bommethylene polyphenyl isocyanate, triphenylmethane triisocyanate, or compounds having two or more active hydrogen atoms such as trimethylolpropane and pentaerythritol with these polyisocyanates Examples include terminal NCO group-containing polyalkylene glycol adduct polyisocyanates obtained by reacting NCO,·'OH>1 in a molar ratio. In particular, aromatic polyisocyanates such as tolylene diisocyanate, metaxylene diisocyanate, diphenylmethane diisocyanate, and polymethylene polyphenylisocyanate are preferred because they exhibit excellent performance.

Examples of blocking agents include phenols such as phenol, thiophenol, cresol, and resorcinol;
Tertiary alcohols such as t-butanol and pentanol, aromatic secondary amines such as diphenylamine and xylidine, imides such as phthalic acid imide, lactams such as caprolactam and valerolactam, acetoxime, methyl ethyl There are oxime bodies such as getone oxime and cyclohexane oxime, and acidic sodium sulfite. As the blocked polyisocyanate compound, the above compounds are used, but in particular, the general formula % (R is an organic residue selected from the group consisting of aromatic, araliphatic, and aliphatic, and X is a heat-treated It is preferable to use a blocked polyisocyanate compound in which a blocking agent residue is liberated by n = an integer of 2 or more.

<Effects of the Invention> Fibers treated by the method of the present invention have improved adhesion to rubber and fatigue resistance in rubber compared to conventional methods.

<Examples> The present invention will be specifically described below with reference to Examples. In the Examples, the cord peeling adhesive strength, T adhesive strength, and strong retention rate are values determined as follows.

- Cord Peel Adhesive Strength Treatment Indicates the adhesive strength between the cord and rubber. Five cords were buried near the surface layer of the rubber sheet and heated to 150°C under pressure.
The force required to peel off the five cords from the rubber sheet at a speed of 200 mm/min was increased to
It is displayed in 15 lines.

・T adhesive strength indicates the adhesive strength between the cord and rubber. The cord was embedded in a rubber block and heated to 150℃ under pressure for 30 minutes.
Vulcanize for 20 minutes, then remove the cord from the rubber block for 200 minutes.
It is pulled out at a speed of mm/min, and the force required for pulling out is expressed in kg/cm.

・Strength retention is a measure of fatigue resistance, using a Gutdrich disc tester to set the cord to a rotating disc Iwama with an elongation of 6%.
This is the amount of strength remaining after 3.5 million repetitions of 18% compression fatigue, expressed as a percentage.

Examples 1 to 5 Fully aromatic polyamide fibers include: 25 mol% of heterophenylenediamine, 50 mol% of terephthalic acid chloride, 3
, 1500 denier 100 obtained by wet spinning a polymer consisting of 25 mol% of 4'-diamino-diphenyl ether.
After obtaining a multifilament with 0 filaments, the two multifilaments were then twisted at 40×40T/10 cm to obtain a cord with 3000 denier/2000 filaments. The code thus obtained is placed in a vacuum device at 13
．． The treatment was carried out continuously in a low-temperature plasma processing apparatus equipped with a 56 MHz high-frequency glow discharge electrode and a cord feeding and winding device. After reducing the pressure inside the vacuum device to 0.05 Torr, Ar, Ch, N2゜N N3,
CF a gas was introduced and the pressure was increased to 1. It was set to QTorr. In this state, a plasma state with an output of 100 W was created using a high frequency of 13.56 MHz. After the plasma state became stable, a winding device, which had been adjusted in advance so that the plasma treatment time would be 1 minute, was operated to perform plasma treatment.

The cord that has been plasma treated as described above is immersed in the treatment agent shown in Table 1 using a computer treater (C, A, manufactured by Ritzler, Tire cord treatment machine) at 150°C for 2 minutes. It was dried and then heat treated at 240°C for 1 minute. A solid content of 6.5% by weight of the treatment agent was attached to the treated aromatic polyamide fiber. Regarding the obtained cord, the cord peeling adhesive strength, T adhesive strength, and strength retention rate were measured.

The results are shown in Table 2.

Comparative Example 1 Cord peel adhesion strength, T
Adhesive strength and strength retention were measured.

The results are shown in Table 2.

The plasma processing gas is q, resorcinol, formalin,
Cord peel adhesion, T-adhesion, and strength retention were measured for treated cords obtained in the same manner as in Example 1, except that the amount of blocked polyisocyanate compound relative to the rubber latex was varied. The result is the third
Shown in the table.

Comparative Example 4 A tire cord made of the same wholly aromatic polyamide fiber as in Example 1 was immersed in the first treatment agent of the epoxy compound shown in Table 4, then dried at 150°C for 2 minutes, and then dried at 240°C.
The sample was heat-treated for 1 minute. This was further immersed in the second treatment agent shown in Table 5, dried at 150°C for 2 minutes, and then dried at 24°C.
Heat treatment was performed at 0°C for 1 minute. The thus obtained wholly aromatic polyamide cord had a solid content of 2.1% by weight of the first treatment agent and 3.2% by weight of the second treatment agent. Table 3 shows the evaluation results of the obtained processing codes.

Examples 6 to 8, Comparative Examples 2 to 3 Table 1 Phenol block of isocyanate, 25% aqueous dispersion *1 *3 Resorcinol/formalin treated condensate Initial condensate of resorcin/formalin reacted with acidic catalyst 40% acetone solution: Hole o2518FS Nippon Zeon Co., Ltd., vinylpyridine-styrene-butadiene terpolymer latex 40% water emulsion Hiren■MP DuPont Co., Ltd., cord treated with 4,4'-diphenylmethane di plasma gas It also shows higher adhesion and strong retention compared to cords that are not plasma treated.

Table 3 shows an improvement compared to the two-bath treated cord.

*4 BI'RFL The amount of blocked polyisocyanate compound expressed in weight percent relative to resorcinol/formalin/rubber latex. If the amount of blocked polyisocyanate added is too small or too large, adhesiveness and fatigue properties will decrease. do.

In addition, after plasma treatment, the adhesion strength and fatigue rate of the cord treated with RFL containing an appropriate amount of blocked polyisocyanate compound, 4 Table 5: Epoxy compound of phenol/formalin resin condensate manufactured by Ciba Geigy ■

Claims (3)

[Claims] (1) After low-temperature plasma treatment of aromatic polyamide fiber, blocked polyisocyanate compound and resorcinol.
A method for processing aromatic polyamide fibers, the method comprising processing with a processing agent containing formalin and rubber latex. (2) The method for treating aromatic polyamide fibers according to (1), wherein the amount of the blocked polyisocyanate compound contained in the treatment agent is 0.5 to 30% by weight based on the resorcinol/formalin/rubber latex. (3) The blocked polyisocyanate compound has the general formula R(NHCOX)_n (R is an organic residue selected from the group consisting of aromatic, aliphatic, and araliphatic, and X is a blocking agent liberated by heat treatment) The method for treating aromatic polyamide fibers according to claim 1 or 2, which is a compound represented by a residue (n is an integer of 2 or more).