JPS61141738A - Bonding of fiber with rubber - Google Patents

Abstract

PURPOSE:To obtain a structure in which fiber is strongly bonded with rubber and which is excellent in fatigue resistance, etc., by treating the surface of an aromatic polyamide fiber with a low-temperature plasma gas in vacuum and treating this fiber with a specified adhesive composition. CONSTITUTION:An aromatic polyamide fiber having amide bonds and aromatic groups in the molecule, such as poly(p-phenylene terephthalamide) is previously passed through a vacuum zone of 10<-3>-10Torr and surface-treated with a low-temperature plasma generated by excitation by an audiowave, high-frequency wave or microwave generator in an atmosphere of a nonpolymerizable gas, polymerizable gas, vaporized gas or a mixture thereof. The treated fiber is treated with an adhesive composition obtained by dissolving resinous matter, obtained by reacting a phenol with an aldehyde in a solvent such as water in the presence of an alkali metal hydroxide catalyst such as NaOH, in a dilute aqueous NH4OH solution in the presence of a free aldehyde and mixing the obtained solution with a rubber latex. After the applied adhesive composition is cured by heating, this fiber is bonded with unvulcanized rubber and heated under applied pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for improving the adhesion between aromatic polyamide fibers and rubber. - After adhesive treatment with an adhesive composition consisting of an aldehyde pre-shrinkage product and rubber latex (hereinafter referred to as PFL) or an adhesive composition based on this composition, and further heat curing, the unprocessed This invention relates to a method for improving adhesion by vulcanizing in contact with sulfurized rubber and thus firmly adhering to the rubber.

When aromatic polyamide fibers and rubber are bonded by the method of the present invention, the adhesive properties are significantly improved compared to those obtained by conventional bonding methods, and the physical properties of the fibers are not degraded, and the adhesive layer is flexible. Significant improvements in flexibility and fatigue resistance can be expected.

Therefore, the method of the present invention is applied to industrial products such as tires, conveyor belts, hoses, rubber crawlers, etc., and is particularly effectively applied to tires and belts that require high performance. Or poly-
Aromatic polyamides, such as roof unilene terephthalamide, have superior heat resistance and chemical resistance compared to aliphatic polyamides, as well as high elastic modulus and high strength properties, so they have good dimensional stability. .

Therefore, it is used in many fields as a structural material by combining it with materials such as thermoplastic resin, thermosetting resin, or rubber. In particular, it is suitable as a reinforcing member for tires because it has the same level of strength as steel cord, is lightweight, and is flexible.

However, aromatic polyamide fibers having the above characteristics still have the following drawbacks.

In other words, it has heat resistance and high strength properties, so it can be used for things that require those properties, but it lacks flexibility and
It is weak against bending and fatigue, and lacks adhesion to other materials (and rubber. For example, when used as a reinforcing material for tires, it consists of a resorcinol-formaldehyde initial compound and rubber latex, which has been widely used in the past. For the application of adhesive (hereinafter this mixture is referred to as RFL), 6-nylon,
Compared to aliphatic polyamide fibers such as 6,6-nylon, aromatic polyamide fibers are inferior in adhesion to rubber and fatigue resistance.

For this reason, two-bath bonding methods have been developed.

For example, the adhesion between aromatic polyamide fibers and rubber can be achieved using the following formulation, water and
850210
% NaOH aqueous solution 10 F 5% dioctyl sodium sulfosuccinate aqueous solution 2 tl 92-pyrrolidone 1 t 107 Diglycidyl ether of glycerol Adhesion treatment with 201000 f adhesive treatment liquid (for undercoat), then adhere with Sara K RFL adhesive (for top coat) A method is being taken.

In addition, improvements in adhesion are mainly related to undercoat adhesives, and many are looking forward to adhesives with a high epoxy group content. However, as the epoxy group content increases, the adhesive layer naturally becomes harder, the treated fiber cord becomes more rigid, and its flexibility, fatigue resistance, etc. tend to decrease.

Purpose of the Invention The purpose of the present invention is to eliminate the drawbacks of adhesion between aromatic polyamide fibers and rubber and the drawbacks of aliphatic polyamide fibers. By treating the fibers with PFL or an adhesive composition mainly composed of PFL, the adhesion to rubber and the fatigue resistance of the finished structure are improved.

Structure of the Invention The present invention is directed to poly-p-phenylene terephthalamide, poly-m-phenylene/terephthalamide, or poly-p-benzamide, which have an amide bond and an aromatic group in the molecule and are called aromatic polyamides. The aromatic polyamide fibers to be heated are heated by audio waves, high frequencies, or microwaves in an atmosphere of non-polymerizable gas, polymerizable gas, or heated vaporized gas alone or in a mixed gas atmosphere through a reduced pressure area of 10-3 to 10 Torr. After surface treatment with excited low-temperature plasma, immersion treatment in an aqueous solution mainly consisting of adhesive (PFL), which is a mixture of phenol-aldehyde initial condensate and rubber latex,
This method further improves the adhesion to rubber by heating and curing it.

More specifically, by subjecting aromatic polynamide fibers to low-temperature plasma treatment, hydrophilic groups are imparted to the fiber surface or the sputtering effect significantly improves the compatibility with aqueous adhesives such as PFL. By doing so, the adhesive not only adheres to the fiber surface but also quickly impregnates the inside of the fiber bundle with IEFL and the like, embedding between the filaments, thereby preventing bending failure.

In addition, aromatic polyamide fibers treated with low-temperature plasma treatment and adhesive treatment were found to have lower physical properties such as strength and elongation than those without this optical surface treatment, as well as those treated with ozone treatment, acid treatment, or ultraviolet ray treatment. Not only is there no improvement, but there is even a tendency for it to improve. As a result of these effects, the rate of decline in physical properties of aromatic polyamide fibers after being integrated with rubber after bending fatigue is significantly improved.

As the low-temperature plasma gas used in the low-temperature plasma treatment of twisted aromatic polyamide fiber cords, non-polymerizable gases, polymerizable gases, or heated vaporized gases can be used alone or in combination as described above, such as helium,
Hydrogen, argon, oxygen, nitrogen, air, chlorine, ammonia, -carbon oxide, carbon dioxide, sulfur dioxide, -nitrogen oxide,
Formaldehyde, hydrogen chloride, etc., and gases that vaporize under reduced pressure include carbon tetrachloride, chlorogenated hydrocarbons (
Trichlene, etc.), formaldehyde water, water, methylamine, ammonia water, water vapor, etc. are preferably introduced, and after adjusting the pressure reduction area to 1 tJ-' -10 Torr, it is heated by an audio wave, high frequency or microwave generator. ”-A low-temperature bladder is generated with an output of IQ kW, and the surface is treated by irradiating it for 1 to 103 seconds in that atmosphere.

In order to carry out the plus process continuously, it is necessary to have a closed-type device that incorporates a fiber cord unwinding and winding device in a vacuum container, or an external unwinding and winding device, and a crimping roller or a small-diameter cord. A semi-closed type device using so-called differential pumping is used, which gradually creates a reduced pressure atmosphere using a sealing material having holes.

As the components of the adhesive used in the method of the present invention, a phenolic compound is first mixed with an aldehyde and sodium hydroxide.
The reaction is carried out in a solution such as water in the presence of an alkali metal hydroxide such as potassium hydroxide, and then an acidic substance such as an organic acid such as acetic acid or hydrochloric acid or an inorganic acid is added to form a resin. An adhesive is used in which the resin is precipitated and separated, and then the separated resin is dissolved in an aqueous solution of ammonium hydroxide in the absence of free aldehydes, and rubber latex is added.

The term phenols referred to here is a general term that includes monohydric phenols and polyhydric phenols. That is, monohydric phenols include phenol, cresol, ethylphenol, xylenol, and other phenols and alkylphenols. Examples of polyhydric phenols include resorcinol, hydroquinone, phloroglucinol, orcinol, talesorcinol, m-xylosinol, and the like.

The phenols most preferably used in the present invention are phenol itself belonging to monohydric phenols, m-cresol, and p-cresol. Among them, phenol is most preferred.

On the other hand, aldehydes generally refer to compounds having an aldehyde group and having reactivity with phenols, and include furfural, acrolein, etc., but formaldehyde is most preferably used in the present invention.

In the present invention, the temperature when phenols and aldehydes are reacted in the presence of an alkali metal hydroxide is preferably in the range of 30°C to 100°C under normal pressure, and most preferably in the range of 70°C to 95°C. Between is preferable. The reaction time is appropriately determined depending on the temperature, amount of catalyst, etc.

For example, in the case of a reaction source [8 tJ°C, it is desirable to determine the amount of catalyst so that the reaction time lasts about 1 to 3 hours.

The content of the alkali metal hydroxide used in the catalyst is suitably between 0.01 mol and 0.2 mol, preferably between 0.05 mol and 0.15 mol, per 1 mol of the phenol.

The reaction between phenols and aldehydes is carried out under the above-mentioned conditions, and in this case, the amount of aldehydes relative to the phenols is important; t) mol or more, preferably 4.0 mol or more, 10
The appropriate amount is less than mol.

The degree of progress of this reaction can be determined by changes in the average molecular weight and molecular weight distribution curve. The average molecular weight of the composite is between 200 and 2500, preferably between 500 and 15
It is desirable to react so that the value is between 00 and 00. however,
Even if it deviates slightly from this range, it will not have much effect on the adhesive performance, but it is better to keep the upper and lower limits of the molecular weight distribution within this range.

Next, after the reaction is completed, the produced resin can be precipitated by dropping an organic acid such as acetic acid or an inorganic acid such as hydrochloric acid, or by introducing the reactant into the acid and neutralizing it.

A resinous material useful for adhesion can be obtained by filtering the precipitate, washing it with water, and drying it in air or under reduced pressure. In this case, a similar resinous material can be quickly obtained by dissolving the precipitate in a low-boiling point organic solvent such as acetone in a wet state before drying and then evaporating and drying under reduced pressure.

Next, the resinous material can be easily dissolved by dissolving it in a dilute aqueous solution of ammonium hydroxide. When the molecular weight of the resin material is large, the amount of ammonium hydroxide may be increased.

Next, rubber latex is mixed with this solution to prepare an adhesive solution. The rubber latex used in the present invention includes natural rubber latex and various synthetic rubber latexes.

In particular, vinylpyridine styrene tadiene terpolymer latex, styrene butadiene copolymer latex, polybutadiene latex, etc. are used. Polychloroprene latex, acrylonitrile-butadiene acrylate copolymer latex, acrylonitrile-butadiene acrylate terpolymer latex, acrylonitrile-alkyl methacrylate butadiene terpolymer latex, ingleninobutylene copolymer latex, ethylene propylene copolymer latex, ethylene propylene non-polymer latex Co-yoke/terpolymer latex etc. can also be used. The above-mentioned rubber latexes can be used alone or in a mixture of two or more kinds, and these can be arbitrarily changed depending on the type of rubber to be adhered.

In this case, the mixing ratio of the phenol-aldehyde initial condensate is 5 to 30% by weight based on the total solid content.
It is preferable that the rubber latex has a weight of 95 to 70 layers.

As detailed above, the method of the present invention involves subjecting an aromatic polyamide fiber cord to low-temperature plasma treatment, subjecting the treated fibers to a PFL adhesive adhesive treatment, heating and curing the cord, bonding this with unvulcanized rubber, heating, This is a method of adhering fibers and rubber, in which a composite with excellent adhesion performance is obtained by vulcanizing a rubber composition under pressure.

The method of the present invention is used in industrial products such as tires, conveyor belts, hoses, and rubber crawlers, and is particularly effectively applied to tires and belts that require high performance.

The adhesive liquid comprising a phenol-aldehyde initial condensate and rubber latex used in the present invention was obtained by the method described below.

Phenols include phenol, m-cresol, m
-Methoxyphenol and m-chlorophenol were used. Each phenol 1. 5.0 mol of 37% formaldehyde aqueous solution and 0.1 mol of caustic soda per U mol
The mixture was reacted at 80° C. for 1.5 hours with stirring in a Kolben equipped with a reflux condenser. After cooling this liquid,
Neutralize with 6N vinegar to remove the contents. After collecting this with a centrifuge, it was dissolved in acetone, evaporated to dryness under reduced pressure in a rotary evaporator at 50°C, and pulverized to obtain a powdery resinous substance.

40 parts of each resinous material thus obtained was dissolved in dilute ammonia water prepared by diluting 50 parts of 28% ammonia water with 550 parts of water. A 40% vinylpyridine-styrene-butadiene terpolymer latex was added to this liquid.

The adhesive solution obtained as described above was used for the following contact.

Adhesives A, B, C and D were obtained.

Adhesive A (phenol-formaldehyde initial condensate/vinylpyridine-styrene-butadiene terpolymer latex,) i Adhesive B (m-cresol-formaldehyde initial condensate/vinylpyridine-styrene-butadiene terpolymer latex) Adhesive C (m -Methoxyphenol-formaldehyde initial condensate/vinylpyridine-styrene-butadiene terpolymer latex) Adhesive D (m-chlorophenol-formaldehyde initial condensate/vinylpyridine-styrene-butadiene terpolymer latex) Examples are given below. The present invention will now be described in detail.

Example 1 A device capable of differential pumping, equipped with a microwave generator and a plasma processing chamber for treating plasma generated by the device, and capable of continuously moving fibers was equipped with a poly-barber. Multifilament cord (150
UD/2, 3Usx3UZ), while continuously moving the pressure in the plasma processing area to 0.1 Torr or less with each differential pump, and in that state, air 1
．． Helium, N2, o2, Ar, Co, CO2
, SO2, No, etc. are introduced from the inlet, the pressure in the plasma processing area is adjusted to 1 Torr, and in that state, the output I is generated by a microwave generator with a frequency of 2.45 GHz.
Each gas plasma was generated using KW, and the speed was adjusted so that the fiber cord passed through the plasma generation area in 20 seconds and 120 seconds, and plasma treatment was performed.

The fiber cord subjected to the plasma treatment as described above was immersed in adhesive A using a Ritzler treatment machine as a fiber adhesion processing device, then dried at a temperature of 140°C for 30 seconds, and then dried at a temperature of 240°C for 60 minutes. A bonded cord was obtained by heat treatment for seconds.

Each fiber cord treated as described above was stretched to a length of 20 U and placed in a mold with a depth of 2 m, and the unvulcanized rubber compound listed in Table 1 below, which was lined with reinforcing cloth, was placed on top of it. Joined, heated and pressurized for 20 minutes at a temperature of 160°C, and vulcanized.
The cord was peeled off from the vulcanized rubber at a tensile speed of 3001 minutes, and the peel adhesion between the rubber and the cord was measured. The results were as shown in Table 2.

Table 1 Table 2 (Microwave-generated plasma) For comparison, a fiber cord that was not subjected to plasma treatment was subjected to adhesive treatment with adhesive A to provide a comparative example. For the comparative example, the peel adhesion between the rubber and the cord was measured using the method described above, and the results are also shown in Table 2.

From the results shown in Table 2, it was clear that the adhesive strength of the release liquid was excellent in adhering the aromatic polyamide fiber cord and rubber by the method of the present invention.

Example 2 A frequency of 13.56 MH was applied to the continuous processing equipment used in Example 1.
A device for generating a high frequency wave of z was installed, and the various gases used in Example 1 were subjected to plasma treatment as described below.

The pressure in the plasma processing area is lower than U, 1 Torr,
Introduce various gases from the gas inlet and adjust the pressure to 1. OTorr
With the plasma adjusted to
Plasma treatment was performed for 0 seconds. Thereafter, adhesive and vulcanization were applied in the same manner as in Example 1 to obtain an adhesive-treated cord.

The peel adhesion between the rubber and the cord was measured for the obtained adhesive-treated cord in the same manner as in Example 1. The results are shown in Table 3.

Table 3 (High frequency generated plasma) Example 3 The continuous processing equipment used in Example 1 was equipped with a frequency of 13.5 (iM
A device for generating high frequency waves of Hz was installed, and high frequency plasma treatment was performed as described below.

That is, the pressure in the plasma processing zone is Q, l tor
r or less, various gases such as oxygen, argon, and air are introduced from the gas inlet, and the pressure is adjusted to l, Q torr, and a high frequency device generates plasma with an output of L (JU W), and it is applied to the fiber cord for 120 seconds. After that, adhesives B, C and D were treated in the same manner as in Example 1.
The peel adhesion between the rubber and the cord was measured using a method of adhesion treatment, followed by vulcanization treatment. The results were as shown in Table 4.

As a comparative example, non-plasma-treated cords were bonded using each adhesive, and their peel adhesion strength was measured in the same manner. The results are shown in Table 4.4 High Frequency Plasma Example 4 The treated cords obtained in Examples 2 and 3 that were subjected to plasma treatment for 20 seconds were subjected to fatigue resistance tests based on strength and elongation measurements and belt bending test methods. I did it.

Fifty treated cords were placed in parallel in the length direction of a mold with a length of 50e, a width of 5mm, and a depth of 1mm, joined with the unvulcanized rubber composition listed in Table 1, and heated at a temperature of 160°C. Heat for 20 minutes,
Pressure was applied to perform vulcanization.

The test piece obtained by the above method was subjected to bending fatigue 500,000 times using a belt bending tester under conditions of a pulley diameter of 32φ and a load of 125 kF. The strength and elongation of the cord taken out from the test piece was measured using a fiber cord tensile testing device at a tensile rate of 300 fm/min, and compared with the strength and elongation before initial fatigue application.

The results obtained are as shown in Table 5.

Table 5 As shown in the examples above, when aromatic polyamide fiber cords were subjected to various plasma treatments and treated with an adhesive mainly composed of PFL, the adhesion to rubber and bending properties were improved.

Reference Example: An aromatic polyamide fiber cord was immersed in an epoxy compound adhesive having the composition shown in Table 6, and then heat treated at a temperature of 240°C for 60 seconds, followed by an RFL adhesive having the composition shown in Table 5. and then soaked at 240℃ for 6 hours.
The adhesive strength and physical properties of the fiber cord were measured based on Examples 1 and 4 after heat treatment for υ seconds, and the results are as follows.

Peeling adhesive strength 1.0 kB/Initial strength 50 ky Elongation 4.9% Strength retention after fatigue 31% Table 6 Patent applicant Brideston Chemical Co., Ltd. Attorney, Patent attorney 1) Written amendment for legal proceedings (voluntary) Showa January 25, 1960

Claims (4)

[Claims] (1) The surface of the aromatic polyamide fiber is treated in a low-temperature plasma gas atmosphere under reduced pressure, and then the treated fiber is adhesively treated with an adhesive composition consisting of an initial condensate of phenols and aldehydes and rubber latex. A method for adhering aromatic polyamide fibers and rubber. (2) The adhesive composition reacts aldehydes with phenols using an alkali metal hydroxide as a catalyst, and then neutralizes with an acid and separates the resin-like product, which is free of free aldehydes. The method according to claim (1), characterized in that it is obtained by dissolving in dilute aqueous ammonia and further mixing with rubber latex. (3) The low-temperature plasma gas is a non-polymerizable gas, a polymerizable gas,
The method according to claim (1), which is a single or mixed gas of and heated vaporization gas. (4) The method according to claim (1), wherein the low-temperature plasma is excited by an audio wave, high frequency, or microwave generator.