JPH06207338A - Polyvinyl alcohol cord and its production - Google Patents

Abstract

PURPOSE:To provide a dip cord of a polyvinyl alcohol fiber having high strength and elastic modulus, durable to repeated bending and extremely suitable as a reinforcing material for a formed rubber article such as tire, oil brake hose, radiator hose, fire hose, conveyor belt and V belt. CONSTITUTION:A polyvinyl alcohol fiber yarn having a polymerization degree of >=8,000 is subjected to twisting, RFL treatment and drying and the obtained cord containing RFL liquid sufficiently impregnated to the core part is heat- treated under high tension to obtain the objective dip cord having a strength of >=15g/d, an intermediate elongation of <=1.5% at 2.25g/d and a strength retention of >=60% by a high-strain belt bending fatigue test at 100 deg.C after 10,000 bendings.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a tire, an oil brake hose, a radiator hose, a fire hose, a conveyor belt, a V-belt, which is repeatedly bent at high temperature for a long time.
The present invention relates to a polyvinyl alcohol (hereinafter abbreviated as PVA) -based cord having high strength and high elastic modulus and excellent in fatigue resistance suitable for a reinforcing material for fiber reinforced rubber products such as timing belts, 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, adhesion, weather resistance, chemical resistance, etc. Has pioneered its own unique uses. In particular, if a PVA cord with improved performance such as strength, elastic modulus, and rubber fatigue resistance is developed as a rubber reinforcing material,
A rubber material is expected to satisfy safety, durability, and light weight under severe conditions.

The cord used for rubber reinforcement has resorcinol / formaldehyde / latex (hereinafter referred to as RFL) added to its surface in order to improve the adhesiveness with rubber (hereinafter, this added cord is dipped). A method for obtaining such a dip cord for a tire or a belt is disclosed in JP-A-64-52842, JP-A-1-207435, JP-A-2-84587, and JP-A-2-216288. Japanese Patent Laid-Open No. 2-249
No. 705, etc. However, in these methods, the PVA-based polymer has a degree of polymerization of 5000 or less.
RFL liquid is attached to the twisted cord of the fiber consisting of
Dry at 0 ° C. for 120 seconds with a tension of 0.1 g / d, and
C. × 30 to 40 seconds 1 g / d tension or 0.5 to 3.5
After heat treatment by% elongation, 200 ° C × 30-40
The dip cord strength was as low as about 12 g / d by the method of performing normalizing by a tension of 0.5 g / d or shrinkage of 0 to 0.5% for 2 seconds. Further, when the number of twists is reduced, the strength and elastic modulus are increased, but the rubber fatigue property is deteriorated, and it is not possible to obtain the one which satisfies both the properties of the strength / elastic modulus and fatigue resistance at the same time. Furthermore, the twisted cord is RF
A method of preliminarily heat setting under tension to increase the strength before the L treatment is also disclosed in JP-A-63-162303 and JP-A-63.
Although it is known from Japanese Patent Laid-Open No. 165548, the RFL liquid is difficult to penetrate into the inside of the cord, so that the cord is hard and the rubber fatigue resistance is not sufficiently satisfactory.

On the other hand, a method for obtaining a high-strength, high-modulus fiber using a PVA-based polymer having a high degree of polymerization is disclosed in JP-A-59-1303.
No. 14, JP-A No. 61-289112, JP-A No. 62-85013, etc.
Fibers having a g / d and an elastic modulus of 550 to 650 g / d are described. The inventors of the present invention created a dip cord using the high-strength, high-modulus fiber by the above-mentioned known method, and although the strength and the elastic modulus are certainly increased, the rubber fatigue resistance is not satisfied yet, It was found that the strength and elastic modulus become insufficient when the fatigue property is improved by increasing the number.

[0005]

Based on the above background, the inventors of the present invention have earnestly studied how to increase cord strength and elastic modulus and improve rubber fatigue resistance.
In order to improve the strength and elastic modulus, fibers made of a high degree of polymerization PVA-based polymer are used, and means for reducing tension during twisting to reduce fiber damage, and heat treatment tension after RFL attachment to increase twist shrinkage and twist unevenness It has been found that the means to do is effective.
To improve rubber fatigue resistance, the tension during twisting or RFL attachment is reduced to allow the RFL liquid to penetrate into the inside of the cord to soften the cord and reduce kink (buckling) during bending and abrasion between single yarns. Further, it was discovered that it is effective to use a high degree of polymerization PVA-based polymer and increase the number of tie molecules penetrating between the crystals to strengthen the fibrils, which led to the present invention.

That is, an object of the present invention is to provide a dip cord made of PVA fiber having high strength and high elastic modulus and excellent in rubber fatigue resistance, which is added as a rubber reinforcing material for tires, belts, hoses and the like. It provides high-value code.

[0007]

That is, according to the present invention, a PVA-based fiber having a viscosity average degree of polymerization of 8,000 or more is added to 0.01
Twisted under a low tension of 0.08 g / d, and 0.
RFL deposition was carried out under a low tension of 05 to 0.15 g / d, and drying was carried out under a low tension of 0.07 to 0.2 g / d, so that the RFL was allowed to penetrate into the inside of the cord, and then 0 By heat treatment under a high tension of 0.5 to 1.5 g / d, the intermediate elongation at a strength of 15 g / d or more and 2.25 g / d is 1.5% or less, and 100 ° C in high strain belt bending fatigue. A PVA type dip cord having a high strain retention of 60% or more after 10,000 times, which is particularly excellent in rubber fatigue resistance, is obtained.

The contents of the present invention will be described in more detail below. The PVA-based polymer referred to in the present invention is one having a viscosity average degree of polymerization of 8,000 or more, particularly preferably a straight chain having a degree of saponification of 98 mol% or more and a low degree of branching.
The higher the degree of polymerization of the PVA-based polymer, the greater the number of tie molecules penetrating many crystals in the network structure, and the higher the strength, the higher the elastic modulus, the higher the fatigue resistance, the easier it is.
It is 50,000 or more, more preferably 15,000 or more. If necessary, 5% by weight or less of a pigment, an antioxidant, an ultraviolet absorber, a crystallization inhibitor, a cross-linking agent, a surfactant, etc. may be added to the PVA polymer. The PVA-based polymer referred to in the present invention also includes a copolymer obtained by copolymerizing 5 mol% or less of a modifier.

The PVA-based fiber used in the present invention is prepared by dissolving such a PVA-based polymer in a solvent to prepare a wet type, a dry-wet type,
It can be obtained by spinning, stretching and heat-treating by any of dry spinning methods. As a solvent for the PVA-based polymer,
Glycerin, ethylene glycol, diethylene glycol, triethylene glycol, 3-methylpentane-
Polyhydric alcohols such as 1,3,5-triol, dimethyl sulfoxide (DMSO), dimethylformamide,
Dimethylacetamide, N-methylpyrrolidone, 1,3
-Dimethyl-2-imidazolidinone, ethylenediamine, diethylenetriamine, water and the like are used alone or in combination. 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, a dry method or the like can be used without any problem.
Among them, a dry-wet method is used to discharge a solution of a PVA polymer from a spinning nozzle and immediately immerse it in a low temperature alcohol such as methanol or ethanol or a mixed solution of them and the solvent, or an aqueous solution containing an inorganic salt or an alkali. Preferred is a method of rapid cooling to obtain a homogeneous and transparent gel fiber. Further, 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, an oil agent is applied and the extracting agent is evaporated by drying. As a result, a spun raw yarn is obtained.

The obtained spun raw yarn is subjected to dry heat drawing by a conventional method at a high temperature of 240 ° C. or more so that the total draw ratio (product of the above wet draw ratio and dry heat draw ratio) is 16 times or more. After that, an oil agent is applied if necessary. Next, a raw cord is produced by twisting with the number of twists suitable for the application. For example, with a tire cord for a radial tire belt part, 1500d / 1 × 2 is 2
50 to 350 t / m, or 1500 d / 1 x 3 for 2
00-300 t / m, 1 for carcass tire code
350-550t / m at 500d / 1x2, 150 at 1500d / 1x2 for oil brake hose reinforcement cord
A ply twist of ˜250 t / m or the like is used.

Usually, twisting is performed by a ring twisting machine, but in this case, the twisting tension needs to be 0.01 to 0.08 g / d. If the twisting tension is less than 0.01 g / d,
Untwisting causes the strength and elastic modulus of the raw cord, and eventually the dip cord, to decrease, and when it exceeds 0.08 g / d, there is little twisting and shrinkage, and the strength utilization factor of the cord improves, resulting in strength and elastic modulus. Is improved, but the fibers are easily damaged (particularly PVA-based fibers are easily crushed by the lateral pressure of the traveler), and the twisted strands make it difficult for the RFL liquid to enter the cord and reduce rubber fatigue resistance, which is not desirable. . The twisting tension is applicable to both lower twisting and upper twisting, and is preferably 0.02 to 0.06 g / d.

In the twisted raw cord thus obtained,
RFL liquid is attached to improve adhesion with rubber,
Dry-heat treatment is applied. Typical examples of the RFL liquid composition are shown in Table 1 and Table 3 described later, but the present invention is not limited to these. In this RFL processing,
In order to permeate the RFL liquid to the inside of the cord, a high concentration of R
It is advisable to use a FL solution and attach it under a low tension of 0.05 to 0.15 g / d. RFL concentration is 15 to 30% by weight,
It is preferably 18 to 25% by weight, and the RFL adhesion rate to the cord is 7 to 20% by weight, preferably 9 to 15% by weight. If the attachment rate exceeds 20% by weight, a large amount of alkali is added to accelerate the condensation reaction between resorcin and formalin, and the PVA fiber is decomposed during heat treatment, resulting in a decrease in strength. On the other hand, if the adhesion rate is less than 7% by weight, the adhesive force with rubber will be insufficient and the fatigue resistance will not be improved. Also, the tension when RFL is attached is 0.05 g / d
If it is less than the above range, it is difficult to reduce twist unevenness and twist and the strength and elastic modulus are not improved. On the other hand, if 0.15 g / d is exceeded, RF
It is difficult for the L liquid to permeate into the inside of the cord, the cord is hard, and kink bands and abrasion occur frequently to reduce the rubber fatigue resistance.

In the present invention, the drying after the RFL deposition is also performed by the above R
For the same reason as the tension condition at the time of FL attachment, 0.07 to 0.
It is carried out under a low tension of 2 g / d, preferably 0.08 to
It is 0.15 g / d. The temperature is 80 to 150 ° C., and rapid heating at 150 ° C. or higher causes decomposition of PVA due to alkali or water in the RFL liquid and sticking of fibers, which easily causes deterioration of mechanical performance. Further, if the temperature is lower than 80 ° C., it takes a long time to dry, and it is uneconomical in terms of equipment to leave it for a long time for drying with a specific tension applied.

Next, heat treatment is carried out at a high temperature in order to complete the reaction of RFL and to fix the fiber, and in this case, 0.5 to
A high tension of 1.5 g / d is suitable, and more preferably 0.8 to 1.2 g / d. If the tension is less than 0.5 g / d, it is difficult to obtain the cord strength and the intermediate elongation (elastic modulus) referred to in the present invention because the twist unevenness and the twist shrinkage are insufficiently corrected. If it exceeds 1.5 g / d, single yarn breakage or deformation of the fiber cross section occurs, and the cord becomes hard, and the high strain rubber fatigue resistance referred to in the present invention deteriorates. The heat treatment temperature is preferably 150 to 220 ° C. At low temperatures, the adhesiveness to rubber decreases, and when it is too high, the rubber fatigue resistance decreases due to decomposition of PVA and cord curing.

PV after RFL treatment obtained according to the invention
A type dip cord has a strength of 15 g / d or more and 2.2.
High strength and high elastic modulus with an intermediate elongation of 1.5% or less at 5 g / d, and a high strain retention rate after bending 10,000 times at 10,000 ° C in a belt with a pulley diameter of 20φ and a large strain rate.
With the above, it is excellent in rubber fatigue resistance, and tires, hoses,
High-performance PVA suitable as a reinforcing material for molded rubber products such as belts
It was a system code.

[0017]

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. The physical property values specified in the present invention are measured by the following methods. (1) Viscosity average degree of polymerization (Pa) of PVA-based polymer According to JIS K-6726, it was calculated from the measured value of the intrinsic viscosity [η] of a 30 ° C aqueous solution by the following formula. Pa = ([η] × 10 ⁴ /8.29) ^1.63

(2) Yarn Tensile Strength, Initial Elastic Modulus In accordance with JIS L-1013, a pre-humidified yarn was insured at a test length of 20 cm with an initial load of 0.1 g / d and a tensile speed of 50% / min. The breaking strength and elongation and the initial elastic modulus were determined by using Ron 4301. Denier was measured gravimetrically.

(3) Tensile strength of dip cord In accordance with JIS-L1017, the sample was tested at 20 ° C. and 65% RH.
After being left in the temperature control room for 24 hours, the test length is 20 cm and the pulling speed is 10
cm / min Initial load 1/20 g / d Instron TM-M
The cutting strength was measured with a mold and a grip for an air cord. On the other hand, the original yarn before twisting is twisted 80 times / m in advance and left at 20 ° C. and 65% RH for 24 hours.
A 90 m long skein roll is made under 0 g / d strength and the yarn denier is calculated from the weight measurement. Next, the cord denier was defined as the number of yarn denier × the number of cords, and the cord breaking strength was divided by the cord denier to give the cord tensile strength.

(4) Intermediate Elongation of Dip Cord In the strength-elongation curve obtained when measuring the tensile strength, the elongation at a strength of 2.25 g / d is represented, which means the tensile elastic modulus of the cord.

(5) RFL Solution and Adhesion Rate The DIP cord was treated with concentrated HCl to dissolve the PVA fiber, and the RFL solution adhesion rate was calculated from the weight of the undissolved material.

(6) Adhesive force A force required to pull out the dip cord from the rubber block. The dip cord is sandwiched between rubber sheets having a thickness of 5 mm and vulcanized by a die having an embedded length of 10 cm. The vulcanization conditions are 150 ° C. × 45 minutes and a gauge pressure of 90 kg / cm ² . The dip cord was pulled out from the rubber block obtained after vulcanization and used as the adhesive strength.

(7) Rubber fatigue resistance 20 dip cords are arranged on 0.7 mm thick raw rubber to form a cord layer, and a 2.4 mm thick cover rubber is placed on the cord layer to form a three-layer structure on the compression side. Create. The same three-layer structure was made separately for the extension side, and these two three-layer structures were used.
Layer the structure so that the raw rubber layer is on the inside and the thickness is 0.
Insert a 7 mm cushion rubber in the middle and stack them so that they consist of 7 layers, sandwiched width 7 cm x length 42
15 cm after forming a rectangular sheet with a thickness of about 8 mm
It is vulcanized at 0 ° C. for 45 minutes at a gauge pressure of 90 kg / cm ² . Next, the rectangular belt was vertically divided into two parts, and the belt was subjected to compression fatigue with a belt bending tester with a pulley diameter of 20 mm at 100 ° C. × 10,000 times, and then the cord on the compression side was taken out from the rubber, and the cord strength before and after bending was strengthened. The retention rate was calculated from

Examples 1 and Comparative Examples 1 and 2 PVA having a viscosity average degree of polymerization of 17,000 and a saponification degree of 99.8 mol% was added to dimethyl sulfoxide at 100 ° C. to a concentration of 5.2% by weight. It was dissolved and dry-wet spinning was performed in a coagulation bath at a methanol / dimethyl sulfoxide = 7/3 weight ratio of 5 ° C. Further, the film was wet-stretched 4 times in a 40 ° C. methanol bath, and then almost all the solvent was removed with methanol.
It was dried at 0 ° C. The obtained spun raw yarn was heated at 180 ° C. for 20
Dry hot drawing was performed in a hot air oven consisting of three sections at 0 ° C and 250 ° C so that the total draw ratio was 19.5 times. The obtained yarn had a high strength of 22 g / d at 1500 d / 400 f.

Next, using the yarn, with a ring twister, the twist number is 31.5 t / 10 cm, and the tension is 0.05 g / d.
Was twisted in the Z direction, and the two twisted yarns were further combined and twisted in the S direction at a twist number of 31.5 t / 10 cm and a tension of 0.03 g / d to produce a raw cord. The raw cord swelled due to the low-strength twisted yarn, and the twisting was 13%.
Next, using the RFL solution shown in Table 1, the RFL solution was attached to the raw cord by the dipping method, and the tension at that time was 0.0.
The RFL solution was permeated to the inside of the cord at 8 g / d. Subsequently, it was dried in a hot air oven with a tension of 0.12 g / d and 100 ° C. for 1 minute and then subjected to hot air treatment with a tension of 0.8 g / d and 200 ° C. for 1 minute to prepare a dip cord. The high tension heat treatment reduced twist shrinkage and uneven twist. The obtained dip code is soft because it has RFL inside.
The L deposition amount was 9.2% by weight. Further, the dip cord has an intermediate elongation of 0.85% at a strength of 17.2 g / d and 2.25 g / d, which is a cord having a high strength and a high elastic modulus not seen in the past, which is sufficient as a rubber reinforcing material. It was possible to reduce the weight. The adhesive strength of the cord to rubber is 2.
I was fully satisfied with 9 kg / book. Furthermore, after putting the cord on the compression side and producing a rubber belt, the strength retention after bending the belt at 100 ° C. × 10,000 times was examined using a pulley with a diameter of 20 mm, and it showed 71%, showing that it was a truck, bus or high-speed passenger car. It was a high value-added product suitable for the tire cord of the belt part of the tire.

[0026]

[Table 1]

Comparative Example 1 was the same as Example 1 except that the twisting tension was 0.1 g / d and the drying tension was 0.25 g / d.
Although it is raised to the above, RFL does not enter inside the cord,
The RFL adhesion rate was as low as 6.7% by weight, and the cord was hard. The strength of the obtained dip code is 16.8.
g / d, the intermediate elongation was 0.88%, which was not much different from that of Example 1,
Although high performance was exhibited, the strength retention of belt flexing dropped to 54%.

Further, as a comparative example 2, a Kevlar made of aramid fiber was used, and the same twisting yarn as in Example 1 was applied at 1500 d / 1000 f, and then the epoxy liquid shown in Table 3 was adhered thereto, and the epoxy solution shown in Table 3 was applied at 150 ° C. for 1 minute and the tension was 0. 1g / d dry and 240
After heat treatment at a temperature of 1 minute and a tension of 0.3 g / d, the RFL treatment shown in Table 1 was performed as in Example 1. Kevlar is a product to which the epoxy solution shown in Table 2 has been previously applied, because the RFL treatment is not sufficient to improve the adhesiveness to rubber. The obtained dip code is soft,
High strength of 17.3 g / d and intermediate elongation of 0.7%,
Although it showed a high elastic modulus, the high strength retention was as low as 38% due to the high flexion of the belt, probably because it was easily fibrillated or because the rubber adhesion was a little low at 2.2 kg / piece.

[0029]

[Table 2]

Example 2 PVA having a viscosity average degree of polymerization of 23,000 was dissolved in glycerin at 190 ° C. to a concentration of 4.5% by weight. Next, after dry-wet spinning in a coagulation bath of methanol / glycerin = 8/2 and -10 ° C, dry heat drawing was performed using a hot air oven at 170 ° C and 258 ° C so that the total draw ratio was 18.5 times. It was The obtained drawn yarn was a high-performance fiber having a strength of 22.8 g / d at 1200 d / 400 f and an elastic modulus of 580 g / d. Then, using a ring twister, the drawn yarn was combined with the lower twist of 45 t / 10 cm and the two lower twisted yarns, and the upper twist of 45 t / 10 cm was further applied. The twisting yarn tensions at this time were 0.05 g / d and 0.07 g / d, respectively. Next, using the RFL solution shown in Table 3, the tension was 0.11.
After applying RFL at g / d, tension is 0.15 g /
d, drying at 100 ° C. for 1 minute, tension of 1.2 g / d,
A heat treatment was performed at 200 ° C. for 1 minute to produce a dip code. The RFL attachment rate of the obtained dip code is 1
It is 2.7%, and the strength is 16. despite the high twist number.
The tensile strength was 4 g / d and the intermediate elongation was 1.0%, showing high strength and high elastic modulus. Adhesive strength with rubber is 3.7 kg / piece, and the strength retention after bending a high strain belt is as high as 92%, and it is a cord for carcass member of a lightweight tire that can withstand rough roads and heavy environment. It has a high strength and a high fatigue resistance that have never existed before.

[0031]

[Table 3]

Example 3 PVA having a viscosity average degree of polymerization of 8,800 was dissolved in dimethyl sulfoxide at 100 ° C., and wet spinning was carried out in a coagulation bath at 15 ° C. and methanol / dimethyl sulfoxide = 7/3. After that, dry heat drawing was performed in a radiation furnace at 170 ° C. and −245 ° C. so that the total draw ratio was 17 times, and 1500 d / 600
A drawn yarn with f and strength of 20.6 g / d was obtained. Using the drawn yarn, 1500 d / 1 × 2 yarns and 20 × 20 t / 10 cm of lower twist and upper twist were applied and wound at each tension of 0.02 g / d. Then, after dipping in the RFL liquid of Table 2, 120 ° C. drying and 210 ° C. heat treatment were performed. The tension at that time is 0.09 each
g / d, 0.12 g / d, 0.8 g / d, RFL
The adhered amount was 11.5% and the rubber adhesive strength was 3.4 kg / piece. The obtained dip strength was 15.5 g / d, the intermediate elongation was 1.1%, and the strength retention after bending of the high strain belt was as high as 67% despite the low number of twists. It became suitable as a cord for reinforcing hoses.

[0033]

EFFECTS OF THE INVENTION According to the present invention, a rubber molded article having high strength and high elastic modulus and capable of withstanding repeated bending, such as a tire, an oil brake hose, a radiator hose, a fire hose, a conveyor belt, and a V-belt, is reinforced. A PVA-based fiber dip cord extremely suitable as a material can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoru Kobayashi 1621 Sakata, Kurashiki City, Okayama Prefecture Kuraray Co., Ltd. (72) Tetsuo Nishizaki 1-2-1, Kaigan-dori, Okayama City Kuraray Co., Ltd.

Claims (2)

[Claims] 1. A cord made of polyvinyl alcohol fiber having a viscosity average degree of polymerization of 8,000 or more and having resorcin / formaldehyde / latex added thereto, and having a strength of 15 g / d or more and 2.25 g / d. The polyvinyl alcohol-based cord having an intermediate elongation of 1.5% or less and a strength retention of 60% or more after 100 ° C. × 10,000 cycles in high strain belt bending fatigue. 2. When twisting a polyvinyl alcohol-based stretched fiber having a viscosity average degree of polymerization of 8,000 or more and then treating with a resorcinol-formaldehyde-latex liquid, the twisting tension is 0.01 to 0.08 g / d. And the tension when adhering to the resorcin / formaldehyde / latex liquid is 0.05 to 0.15 g / d, and the tension when drying is 0.0
It is characterized in that after it is adjusted to 7 to 0.2 g / d, it is heat-treated under a tension of 0.5 to 1.5 g / d so that the attachment rate of resorcin / formaldehyde / latex to the fiber is 7 to 20% by weight. Method for producing polyvinyl alcohol cord.