JPH07279057A - Durable polyvinyl alcohol fiber and method for producing the same - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a polyvinyl alcohol fiber having excellent wear resistance and flex fatigue resistance, and in particular, a polyvinyl alcohol fiber having such performance, and having high strength and high elastic modulus. . [Structure] A polyvinyl alcohol fiber obtained by coagulating a polyvinyl alcohol solution uniformly and further stretching at a high ratio is coated with a resin having excellent heat resistance and abrasion resistance, and then tensioned. Heat treatment is performed below, and an oil agent having a low friction coefficient between fibers, for example, a silicon-based or fluorine-based oil agent is applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for rubber reinforcing materials such as tires, belts, hoses, etc., which are repeatedly bent or rubbed for a long time, and general industrial materials such as fishing nets, ropes, tents and civil engineering sheets. The present invention relates to an excellent polyvinyl alcohol (hereinafter abbreviated as PVA) fiber and a method for producing the same.

[0002]

2. Description of the Related Art Conventional PVA fibers are superior to polyamide, polyester and polyacrylonitrile fibers in strength, elastic modulus, weather resistance, chemical resistance, adhesiveness, etc. We have pioneered unique uses.
Recently, attention has been focused on cement-reinforcing fibers (substitute for asbestos) and alkaline battery separators that take advantage of alkali resistance. However, when it is repeatedly used for a long time, there is a defect that the fibers are rubbed with each other and fusion occurs to easily deteriorate the performance. Further, when used as a tire cord, there is a problem that bending causes a kink, resulting in a decrease in strength. If such long-term fatigue resistance is improved, fibers with high added value can be expected as a rubber reinforcing material or a general industrial material.

A method for obtaining a PVA fiber having high strength and high elastic modulus is disclosed in JP-A-59-130314 and JP-A-61-161.
No. 289112 and Japanese Patent Application Laid-Open No. 2-74606, the high-strength, high-modulus fibers produced by these methods all have abrasion resistance and fatigue resistance during repeated use for a long time. It wasn't enough. On the other hand, an aromatic polyamide or polyester having poor adhesion to rubber is usually attached with an epoxy resin, heat-treated, and then heat-treated with a resorcin-formalin-rubber latex (RFL). Publication, JP-A-61
No. 146876, Japanese Patent Application Laid-Open No. 1-207480, and the like are all unsatisfactory in terms of rubber fatigue resistance. After that, in order to improve the rubber fatigue resistance of the aromatic polyamide, JP-A-6-25977 and JP-A-6-25978 disclose epoxy compound adhesion-heat treatment-RFL adhesion-heat treatment-twisted yarn-RFL adhesion-heat treatment. However, since the process is complicated and only the resin is attached before twisting, the strength of the twisted cord is low (the cord strength utilization rate is low), and the rubber resistance is further improved. It had a drawback that the degree of improvement in fatigue resistance was insufficient.

On the other hand, since PVA fiber has good adhesiveness to rubber, normally, twisted cord is only subjected to RFL treatment. In this case, a method of increasing the strength by applying tension before or after RFL treatment is disclosed in JP-A-63-162303 and JP-A-63.
-165548, JP-A-64-52842, JP-A-1-207435, and JP-A-2-216.
It is known from Japanese Patent No. 288, etc. However, in all of these, the RFL liquid does not easily penetrate into the inside of the twisted cord, so that the cord twisting portion rubs against or is fused to the repeated bending, and further promotes the growth of the kink band to improve fatigue. make worse. Further, a method of impregnating a PVA-based cord with liquid rubber before RFL treatment to improve fatigue resistance is also known in JP-A-63-66382 and JP-A-63-196778, but fatigue resistance is known. The degree of improvement was not sufficient, and the subsequent processability and the reduction in the strength utilization of the cord were caused, and it was difficult to obtain a cord having high strength and high elastic modulus.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the abrasion resistance and flex fatigue resistance of PVA type fibers.

[0006]

That is, the present invention provides a PV
The surface of the A-based fiber is coated with a resin of 0.5 to 10% by weight based on the fiber, and the F / F static friction coefficient is 0.
A PVA-based fiber to which 28 or less oil agent is added,
As a method for producing such a fiber, a PVA-based fiber is coated with a resin in an amount of 0.5 to 10% by weight based on the weight of the fiber, heat treated under a tension of 0.2 g / d or more, and then F
/ F relates to a method of applying an oil agent having a static friction coefficient of 0.28 or less.

The contents of the present invention will be described in more detail below. The PVA referred to in the present invention is a linear one having a viscosity average degree of polymerization of 1500 or more, a saponification degree of 98 mol% or more, and a low branching degree. The higher the degree of polymerization of PVA, the greater the number of tie molecules penetrating many crystals in the network structure, and it is easy to obtain a tie molecule with high strength and high elastic modulus that can withstand friction and bending fatigue. It is preferably 3000 or more, more preferably 6000 or more. If necessary, 5% by weight or less of a pigment, an antioxidant, an ultraviolet absorber, a crystallization inhibitor, a cross-linking agent, and a surfactant may be added to the PVA-based polymer. Further, those obtained by copolymerizing 5 mol% or less of a modifier are also included.

As a method for producing PVA-based fibers, a method of dissolving PVA in a solvent and then spinning and stretching it is used. Examples of the solvent for the PVA polymer include polyhydric alcohols such as glycerin, ethylene glycol, diethylene glycol, triethylene glycol, and 3-methylpentane-1,3,5-triol, and dimethyl sulfoxide (D
MSO), dimethylformamide, dimethylacetamide, N-methylpyrrolidone, 1.3 dimethyl 2-imidazolidinone, ethylenediamine, diethylenetriamine and water are used alone or as a mixture. Further, it is also possible to use a solution that dissolves the polymer, such as an aqueous solution of an inorganic salt such as zinc chloride, magnesium chloride, calcium rhodanide or lithium bromide. A polyhydric alcohol that gels upon cooling, a mixed solvent of them and water, dimethyl sulfoxide, dimethylformamide, a mixed solvent of them and water, and the like are preferable because spinning stability tends to occur.

As the spinning method, any generally used method such as a wet method, a dry method and a dry-wet method can be used without any problem. Among them, a dry-wet method is used to discharge a solution of a PVA-based polymer from a spinning nozzle and immediately immerse it in a low temperature alcohol such as methanol or ethanol or a mixed solution thereof with the solvent, or an aqueous solution containing an inorganic salt or an alkali. It is preferable that the method is followed by rapid cooling to obtain a homogeneous and transparent gel fiber. Also,
In order to prevent the cross-sectional deformation and sticking of the gel fiber and to break the fine crystals during spinning to improve the draw ratio, it is preferable to wet-draw at least 2 times, preferably at least 4 times while containing the solvent. Then, after removing almost all of the solvent with an extracting agent such as alcohols such as methanol and ethanol and acetone and water, the extracting agent is evaporated by drying.

The spun raw yarn obtained by the above method is subjected to dry heat drawing by a conventional method at a high temperature of 220 ° C. or more and a total draw ratio of 16 times or more. The total draw ratio is represented by the product of the wet draw ratio and the dry heat draw ratio, but when the total draw ratio is less than 16 times, P
The orientation of the VA molecular chain becomes insufficient, and it is difficult to obtain a high-strength, high-modulus fiber. If the dry heat stretching temperature is lower than 220 ° C, the draw ratio is lowered, the crystallization is insufficient, and the dimensional stability is insufficient. It should be noted that there is no problem even if the drawing is smoothly carried out at a high temperature, or if an oil agent, an antioxidant or the like is attached before the drawing in order to suppress color decomposition of PVA. By using such a method, the viscosity average degree of polymerization of 1500 to
PV with a tensile strength of 12 g / d or more and an initial elastic modulus of 200 g / d or more as a yarn from PVA in the range of 3000.
The A-based fiber is a yarn made of PVA having a viscosity average degree of polymerization of 3000 to 6000, and has a tensile strength of 15 g /
A PVA-based fiber having a d of at least 250 g / d and an initial elastic modulus of at least 250 g / d is used as a yarn from PVA having a viscosity average degree of polymerization of at least 6000 and has a tensile strength of 17 g / d or more and an initial elastic modulus of 300.
PVA-based fibers of g / d or more are obtained.

Next, in the present invention, in order to impart durability such as wear resistance, flex fatigue resistance, and anti-melting property when used for a long period of time, the obtained PVA type drawn yarn having high strength and high elastic modulus is obtained. It is necessary to coat 0.5 to 10% by weight of resin. Examples of the resin include thermosetting resins such as epoxy resin containing two or more epoxy groups in one molecule, polyurethane resin, melamine resin, phenol resin, unsaturated polyester resin, or acrylic resin, methacrylic resin, vinyl chloride. It is possible to use one or more kinds of resins, thermoplastic resins such as vinyl acetate resin, and further, rubber elastic materials such as ethylene-propylene copolymer, vinyl pyridine-based resin and styrene-butadiene copolymer. However,
It is not desirable that the material has low heat resistance and wear resistance.
A resin that withstands the above (that is, a resin that does not melt at 100 ° C. and that does not substantially thermally decompose) and that is hard to wear is preferable. What is formed, for example, an epoxy resin compound having two or more functional groups, an unsaturated polyester compound, an isocyanate resin compound, a methylolmelamine compound,
A vinylpyridine-based resin compound and a polyamide-based compound are more preferable. However, it is not preferable that the fibers themselves become too hard and the bending fatigue resistance, the strength and elongation, and the elastic modulus significantly decrease, and all the above-mentioned suitable resins satisfy this requirement.

If necessary, an acid, an alkali, a curing agent, a dispersant, etc. are mixed with the resin, and the surface of the fiber is coated with a liquid dissolved or emulsified in water or an organic solvent.
The coating method may be any of the roller touch method, the dip nip method, the gear pump oiling method, etc. If the amount of the resin adhered is less than 0.5% by weight based on the fiber, the effects of abrasion resistance and bending fatigue resistance are insufficient, and 1
When it exceeds 0% by weight, the strength and elastic modulus of the fiber are lowered or the PVA is easily decomposed, and the fiber becomes hard, and conversely wear resistance and flex fatigue resistance deteriorate. The preferable amount of adhesion is 1 to 5% by weight.

Next, after the resin is attached, heat treatment including drying is performed to react the resin with the fiber or form a resin film. In that case, it is preferable to treat under a tension of at least 0.2 g / d or more. If the tension is less than 0.2 g / d, the fiber is likely to contract, resulting in a decrease in strength and elastic modulus. Further, the occurrence of single yarn breakage due to high tension also leads to deterioration in performance, and it is preferably 0.5 to 1.5 g / d. As the heat treatment temperature, a temperature at which the resin is crosslinked or dried and solidified, that is, 100 ° C. or higher is adopted.

In the present invention, the coefficient of static friction between fibers measured by the method described below after resin adhesion-heat treatment is 0.28.
Apply the following oil agent. The purpose of this is to improve the process passability after that and to increase the strength utilization rate (ratio of the cord strength to the yarn strength) when creating twisted cords such as tire cords, ropes, fishing nets, etc. There is a thing. Therefore, the above effect cannot be expected when only the resin is used and there is no oil agent, or when an oil agent having a coefficient of static friction exceeding 0.28 is attached. Examples of the low-friction oil agent include casting oil-based agents, copolymers of polypropylene oxide and polyethylene oxide (PO / EO-based), fatty acid ester-based polyhydric alcohols, silicone-based, and fluorine-based agents. Deposition amount is 0.1 to fiber weight
It is preferably 1% by weight, and it is preferable to carry out under tension during drying after adhesion.

According to the present invention, it is possible to obtain a durable PVA-based fiber which maintains high strength and high elastic modulus and is excellent in abrasion resistance and bending fatigue resistance, and can be used for rubber materials such as tires, hoses and belts. It became suitable for general industrial materials such as ropes and fishing nets.

[0016]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the examples. Various physical properties in the examples were measured by the following methods. (1) Viscosity average degree of polymerization (PA) of PVA-based polymer According to JIS K-6726, the PVA-based polymer is dissolved in hot water to prepare a dilute aqueous solution, and the specific viscosity at 30 ° C is measured at 3 points. Obtain the intrinsic viscosity [η] from these values,
The viscosity average degree of polymerization was determined by PA = ([η] × 10 ⁴ /8.29) ^1.63 . (2) Fiber-to-fiber static friction coefficient (F / Fμs) Using a fiber to which an oil agent is applied in an amount of 1.0% by weight in solid content, J
Measured in accordance with IS L-1015. However, instead of the cylindrical sliver by staples, a bobbin with both brim needles and filaments wound in parallel in a drum shape was used.

(3) Adhesion amount of resin About 5 g of a sample was precisely weighed, and only the fiber was dissolved in hot water to calculate the residual weight, or only the resin was dissolved to obtain the weight decrease of the sample. . (4) Yarn Tensile Strength, Initial Elastic Modulus According to JIS-L1013, the yarn is pre-twisted 80 times / m and left at 20 ° C. and 65% RH for 24 hours.
Using a Grip for Instron TN-M type pneumatic cord at a test length of 20 cm, a pulling speed of 10 cm / min, and an initial load of 1/20 g / d in a standard condition of 20 ° C. and 65% RH, the cutting strength and elongation are increased. The degree was measured. Further 80 times / m
Making a 90 m long skein winding of twisted yarn under 1/20 g / d tension, and calculating the yarn denier by weight measurement,
The breaking strength was divided by denier to obtain the strength (g / ar). Also, 100% elongation from the initial gradient of the strength-elongation curve
The tenacity corresponding to was calculated | required, it was divided by this denier, and the initial elastic modulus was calculated | required. In each case, the average value of n = 10 was adopted. The high temperature performance was measured in a hot air oven at 100 ° C or 150 ° C in the same manner as at 20 ° C.

(5) Rubber Fatigue Resistance A resin-bonded PVA yarn of about 1500 dr was used for 31 t / 10.
31t / 10c after two twists in cmZ direction
A raw cord is prepared by twisting in the mS direction. Then RFL
(Resorcin, formalin, rubber emulsion) is attached to create a dip code. Next, two cord layers in which 20 cords are arranged on the compression side and the extension side are formed, and a rubber layer is arranged in the middle and outside thereof to form a sandwich-shaped width 25.4.
A rubber sheet having a size of mm × length 420 mm × thickness of about 8 mm is prepared, and then vulcanized at 150 ° C. for 45 minutes at 90 kg / cm ² to prepare a belt. The belt was bent 200,000 times at room temperature with a belt bending tester having a pulley diameter of 25 mm, the cord on the compression side was taken out from the belt, and the holding ratio was obtained from the cord strength before and after bending to evaluate rubber fatigue resistance. (6) Abrasion resistance (twisting abrasion) Approximately 1500 dr of resin-adhered PVA yarn at 80 t / mZ
After making a ring by twisting in the direction, twist was made in the S direction three times at the center of the ring, the yarns were worn up and down at room temperature, and the number of times of cutting was read.

Examples 1 and 2 and Comparative Example 1 PVA having a viscosity average degree of polymerization of 4000 (Example 1) and 8000 (Example 2) and a saponification degree of 99.5 mol%.
Were dissolved in dimethylsulfoxide (hereinafter abbreviated as DMSO) at 100 ° C. to have concentrations of 10% by weight and 7% by weight, respectively, and the obtained solutions were discharged from a nozzle of 500 holes, and methanol / DMSO = 7/3. Wet spinning was performed in a coagulation bath having a weight ratio of 5 ° C. 4 in a 40 ° C methanol bath
After the double-moisture stretching, almost all of the solvent was removed with methanol. The obtained spun raw yarn was 170, 2 in Example 1.
Dry hot drawing was performed in a hot air oven consisting of three sections of 00 ° C and 240 ° C so that the total draw ratio was 19 times. Example 2 is 1
Stretching was performed at 70, 200 ° C. and 250 ° C. at a total stretching ratio of 18.5 times. The drawn yarns were all 1500 d /
At 500f, the strength of Example 1 is 17.6 g / d, the elastic modulus is 350 g / d, and the strength of Example 2 is 20.3 g / d.
The elastic modulus was d and the elastic modulus was 380 g / d.

Then, 4% of glycerol polyglycidyl ether having 2-3 functional groups (epoxy groups) in the drawn yarn by dipping method, 0.03% of NaON for promoting crosslinking and 0.1% of dioctylsulfosuccinate Na salt as a dispersant. Aqueous solution containing is attached, and the tension is 0.8 g / d under 100
℃ dry-220 ℃ heat treatment was performed. The resin adhesion amount was 2.5% by weight in Example 1 and 2.1% by weight in Example 2.
Subsequently, 0.7% by weight of a silicon-based oil agent having a static friction coefficient of 0.21 (an aqueous dispersion of polydimethylsilicone) was deposited and dried at 100 ° C.

The strength of the resin-adhered yarn obtained in Example 1 was
The elastic modulus was 17.0 g / d, and the elastic modulus was 320 g / d. In Example 2, the strength was 19.4 g / d and the elastic modulus was 340 g / d, which were not significantly different from the performance before resin adhesion. Also, to evaluate the rubber fatigue resistance, 1500 d / 1 × 2,31 t / 10 cm raw cord was RFL-treated to make a dip, but the cord has a high utilization factor (ratio of cord strength to yarn strength).
Was as high as 85%. Further, the strength retention after bending the belt 200,000 times at room temperature, 25φ, was 71% in Example 1, and 80% in Example 2, which was excellent in bending fatigue, and a fiber with high added value as a tire cord. Became.
Further, the number of cuts due to twisting wear was 2,850 times in Example 1 and 3210 times in Example 2, and the wear resistance was also good.

As Comparative Example 1, the case where no epoxy resin was adhered was carried out in Example 1, but the strength and elastic modulus were slightly higher than those of Example 1, but the belt flexural strength retention rate was 52.
%, And the number of times of rubbing and rubbing was 1100 times, which proved to be inferior in bending fatigue resistance and wear resistance.

Example 3 and Comparative Example 2 Viscosity average degree of polymerization is 17,000 and saponification degree is 99.8 mol%.
PVA of DMS to a concentration of 5.5% by weight
It was dissolved in O at 110 ° C., and the resulting solution was discharged from a 200-hole nozzle, and methanol / DMSO = 7/3
Dry-wet spinning was performed in a coagulation bath at a weight ratio of 7 ° C. 40 ° C
Almost all of the solvent was removed with methanol after 4 times wet drawing in a methanol bath. The obtained spinning yarn is 170 ° C.
Dry heat drawing was performed in a radiation furnace at −255 ° C. so that the total draw ratio was 18.5 times. The drawn yarn obtained is 750d / 200f
The strength was 22.4 g / d and the elastic modulus was 490 g / d.
Next, the two drawn yarns were combined to make 1500 d / 400 f, and a 4% rubber emulsion, which is a copolymer of vinyl pyridine and styrene butadiene, was attached by a roller touch method, and dried at 100 ° C. under a tension of 1.2 g / d. Heat treatment was performed at ℃. The amount of rubber attached was 5.0% by weight. Then, 0.5% by weight of an oil agent of PO / EO copolymerization having a static friction coefficient of 0.24 [PO: EO = 25: 75 (molar ratio), aqueous solution of a random copolymer having a molecular weight of 10,000] was deposited 10
It was dried at 0 ° C.

The strength of the obtained resin-bonded yarn is 21.
The high level of 3 g / d and the elastic modulus of 440 g / d were maintained. Furthermore, the strong utilization rate of the dip code after RFL treatment was a high value of 82%. Further, the strength retention after bending of the belt was 73%, which was excellent in rubber fatigue resistance, and was unprecedented as a tire belt. Moreover, the twisting abrasion was as good as 2500 times, and a durable product was expected as an industrial material. On the other hand, as Comparative Example 3, a case where an oil agent having a low friction was not attached was carried out in Example 3, but the tension unevenness was large in the twisted yarn at the time of making the cord, and the cord strength utilization ratio was reduced to 68%. Further, rubber fatigue resistance and twist abrasion resistance are also shown in Example 3.
It was 20 to 30% worse than the above.

Example 4 Viscosity average degree of polymerization is 1700 and degree of saponification is 99.8 mol%.
Was dissolved in water to a concentration of 23%, and wet spinning was performed by a conventional method using Glauber's salt and an aqueous solution of caustic soda as a coagulating bath. The obtained spun raw yarn was drawn in a hot air oven at 180 to 200 to 235 ° C. so that the total draw ratio was 19 times. The strength of the obtained 1800d / 1000f drawn yarn is 15.1.
The g / d and elastic modulus were 320 g / d. Then, a DMF solution of 5% polyether polyurethane having good heat resistance and abrasion resistance was attached to the drawn yarn by a dip nip method, and 100 ° C. dry-150 ° C. heat treatment was applied under a tension of 0.5 g / d. The amount of the urethane resin attached was 3.2% by weight. Subsequently, 0.35% by weight of a water emulsion oil containing a mineral oil having a static wear coefficient of 0.25 (redwood viscosity: 150 seconds) and a dispersant (dioctyl sulfosuccinate) was deposited and dried at 100 ° C. The obtained resin-adhered yarn had a strength of 14.2 g / d and an elastic modulus of 300 g / d, and maintained high performance even with a low degree of polymerization PVA. Further, the belt had a strong retention rate of 60% in bending of the belt, which was rubber-fatigue resistance, and was highly wearable, and a durable PVA fiber was obtained.

[0026]

EFFECTS OF THE INVENTION According to the present invention, PVA-based fibers excellent in abrasion resistance and flex fatigue resistance are obtained, and further, the PVA-based fibers to which the finishing treatment of the present invention is applied are PVA-based fibers by the treatment.
The tensile strength and elastic modulus of the PVA-based fibers do not significantly decrease, and therefore the PVA-based fibers have high strength and
When a material having a high elastic modulus is used, it is possible to obtain a PVA-based fiber having a high strength and a high elastic modulus and further excellent in abrasion resistance and bending fatigue resistance. Rubber materials such as tires, belts, hoses, fishing nets,
Excellent as a fiber for industrial materials such as ropes, tents and civil engineering sheets.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidetsuna Kawachi 1 Kuraray Co., Ltd., 2045 Sakata, Kurashiki City, Okayama Prefecture

Claims (2)

[Claims] 1. A polyvinyl alcohol-based fiber whose surface is coated with a resin of 0.5 to 10% by weight based on the fiber, and which is further provided with an oil agent having an F / F static friction coefficient of 0.28 or less. Alcohol-based fiber. 2. A polyvinyl alcohol fiber is coated with a resin in an amount of 0.5 to 10% by weight based on the weight of the fiber, and 0.2
A method for producing a polyvinyl alcohol fiber, comprising applying an oil agent having an F / F static friction coefficient of 0.28 or less after heat treatment under a tension of g / d or more.