JPS6335844A - Tire cord composed of polyvinyl alcohol fiber improved in flexural hardness - Google Patents

Abstract

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

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is a pneumatic tire that has excellent strength, elastic modulus, and fatigue resistance, and has excellent handling stability during high-speed running, reduced fuel consumption, durability, and quality. Polyvinyl alcohol (hereinafter abbreviated as PVA)-based tire cord (hereinafter referred to as PVA-based tire cord) with excellent reproducibility, especially the excellent high strength and high elastic modulus physical properties of fibers made of PVA-based polymer with a high degree of polymerization. This invention relates to a tire cord with improved strength and bending hardness as reflected in the physical properties of the tire cord.

(Prior Art) There are three types of pneumatic tires depending on the direction or arrangement of the cords: bias tires, radial tires, and belted bias tires.There are two types of pneumatic tires: radial tires with a hoop effect on the belt part and belted bias tires. It is said that this tire provides good handling stability for cars.

With the development of motorization, the reinforcing materials for the belt part of the radial tires and belted bias tires mentioned above are required to have high strength, high modulus of elasticity, dimensional stability, impact resistance, adhesion, high compressive modulus, and low growth properties. , high stiffness, etc. are required, but it is more advantageous that the specific gravity of the reinforcing material is small and the price is low.

In recent years, the construction of expressways has progressed, and belted bias tires and radial tires, which have good handling stability, have become popular.
Among these, radial tires that use steel fibers for their belt members are attracting attention due to their excellent handling stability. However, because this radial tire places too much emphasis on the design of handling stability, it tends to directly pick up unevenness on the road surface.
There are some dislikes for sacrificing ride comfort and livability, and there is also a lot of noise when driving. In other words, tires with good handling performance that are reinforced with steel fiber cords have a hard ground contact area that easily picks up unevenness on the road surface, so a car equipped with such tires will be able to handle bumps and bumps easily. It is known that when a vehicle is driven on a road surface, it vibrates violently, deteriorating ride comfort and livability. This steel fiber cord is inherently more prone to rust than organic fiber materials.
The inherent drawbacks are that the durability is not sufficient and the specific gravity is high, making the tire itself heavy and fuel consumption high.

Under these current circumstances, instead of using only steel fiber cord as a belt member, aramid i! ,! Attempts are known to use steel fibers (eg, DuPont's "KeVlar") in combination with steel fibers.

However, due to the high price of the aramid fibers used in combination and the difficulties in designing and manufacturing tires associated with the combination, it is limited to special tire applications and has not yet become fully widespread.

On the other hand, PVA-based fibers have been used for tire cords for a long time, but due to their inherently inferior bending hardness, they could not be used as reinforcing materials for the carcass of radial tires. . As an attempt to improve the bending hardness of this PVA system II,
Publication No. 1 proposes a method for specifying conditions such as ply-twisting and ply-twisting of PVA fiber cords used as belt members. It was not possible to greatly improve the inherent bending hardness defect of PVA-based fibers.

Moreover, the conventional PVA fiber was
As described in Publication No. 58, in the case of a cord made by twisting three yarns of 1200 denier (d), the cutting strength is approximately 30K (1, that is, tensile strength is 7.5 (1/d)
However, compared to the aramid fibers mentioned above, it was significantly inferior in terms of mechanical strength.

Under these circumstances, Japanese Patent Application Laid-Open No. 59-130314 discloses a method in which a spinning solution in which a PVA-based polymer with an extremely high degree of polymerization with a molecular weight of 500,000 or more is dissolved is maintained at a high temperature and introduced into a cooling bath through a spinneret hole. After gelling the discharged yarn into a rubbery state, a spinning method in which the solvent in the obtained rubbery gel yarn is extracted and removed to form fibers, that is, a gel spinning method, is used to obtain a strength of 10 g/ It is disclosed that a high-strength, high-modulus PVA fiber having an elastic modulus of 2()OfJ/d or more can be obtained.

However, the PVA-based fiber disclosed herein is
PV with a molecular weight of 500,000, which is difficult to produce and obtain industrially.
In fact, in the production of the PVA-based polymer disclosed in this known example, -4
A special polymerization method is used in which ultraviolet rays are irradiated for a long time (approximately 100 hours) at a low temperature of 0°C. Also,
The fibers disclosed in this prior art are monofilament yarns, not the multifilament yarns for which tire cords are made. Therefore, in the case of gel spinning, although it is easy to produce monofilaments, it is difficult to produce multifilament yarns, which require avoiding inter-filament binding, and therefore, the high-strength PVA obtained by this method It was not possible to use the fibers as they were as tire cord yarns.

The present inventors focused on PVA fibers, which are not heavy or rusty like steel fiber cords, and are not expensive like aramid fibers, and compared them with conventional PVA fibers to find out their characteristics as tire cords. has previously proposed a significantly improved PVA-based fiber and a tire cord made of the PVA-based fiber.

However, the present inventors have found that when such high strength, high modulus PVA yarn fibers are used as tire cords, the characteristics of tire cords, such as bending hardness, are not necessarily sufficient. Therefore, we have conducted extensive research and discovered the present invention.

(Problems to be Solved by the Invention) An object of the present invention is to solve the special requirements for a tire cord having excellent handling stability at high speeds and good durability, especially as a tire cord for a carcass member of a radial tire. PVA with high strength, high modulus, excellent fatigue resistance, and substantially satisfies the properties required for tire cords, such as high modulus, dimensional stability, heat resistance, low heat generation, low growth, and adhesive properties.
To provide a PVAM tie A7 cord using multifilament yarn as a reinforcing material, especially a tire cord having improved bending hardness in which the excellent fiber properties of fibers obtained from high polymerization degree PVA are reflected in the cord properties. be. Another object is to provide a new tire cord that can be used not only for carcass members of radial tires and belted bias tires but also for belt members, which satisfies the above-mentioned required properties of tire cords, and further Another objective is to provide a pneumatic tire that improves tire uniformity and provides superior vehicle ride comfort and handling stability.

(Means for Solving the Problems) The object of the present invention is to achieve the invention described in the claims, that is, a PVA-based polymer having a degree of polymerization of at least 2000, and having a tensile strength of 15 g/d or more. Strength and 250g/d
This can be achieved by a tire cord that is made of a multifilament yarn with no fusion between single fibers and has an initial modulus of elasticity of above, and whose bending hardness (Sb) is within the range of 10 to 80q. can.

That is, in the /N invention, by increasing the degree of polymerization of the PVA polymer constituting the PVA multifilament yarn as much as possible, it is possible to increase the mechanical strength of the resulting multifilament. An increase in the degree of polymerization of a PVA-based polymer sharply decreases the spinnability, filamentability, and especially drawability of the polymer, and also causes fusion between single fibers. However, by employing specific means described below, it is possible to substantially prevent this fusion between single fibers and to produce a highly drawn PVA multifilament with high strength and high elastic modulus. However, the degree of polymerization of the PVA polymer constituting the PVA multifilament yarn of the present invention is at least 200.
0. It is preferably within the range of 2,500 to 5,700, more preferably 3,000 to 5,000; if the degree of polymerization is too small, the mechanical properties such as strength and elastic modulus of the resulting fibers will deteriorate.
In particular, it becomes difficult to improve the physical properties such as fatigue resistance and heat resistance required for tire cords, and PVA-based polymers with an excessively high degree of polymerization are difficult to obtain commercially, and special polymer manufacturing methods are required. This is undesirable because it increases the manufacturing cost of the multifilament yarn and reduces fiber forming properties such as spinnability and drawability.

A PVA multifilament yarn made of a PVA polymer having a degree of polymerization of 2,000 or more has a tensile strength of 15 (1/d or more, preferably 17C1/d or more, more preferably 18 (1/d or more) and an initial The elastic modulus is 2
50 (1/d or more, preferably 3201 J/d or more, more preferably 350 g/d or more, and because it has such characteristics of high strength and high elastic modulus, it has a reinforcing effect on tires. This makes it possible to reduce the amount of fiber used or the number of plies used in the tire, which reduces the amount of tire deformation and improves recovery from deformation, which reduces the weight of the tire itself and reduces fuel consumption. It can be made into a less expensive tire, and its usefulness as a reinforcing material for radial-tied A7 tabbed bias tires, which require high-speed stability, durability, and wear resistance, can be greatly improved. .

In the tire cord of the present invention, which is made of a PVA-based polymer having such a degree of polymerization and a PVA-based multifilament yarn having the above-mentioned excellent mechanical properties, the bending hardness thereof is 10 to 80 g, preferably 20 to 60 g. It is important that the

In other words, when the bending hardness of the cord is less than 10g, the shape retention of the cord's woven sag is poor, and the cord is easily disturbed when embedded in rubber, which is undesirable.On the other hand, when it exceeds 80g, the cord is is undesirable because it is too rigid, resulting in poor handling during the process and a decrease in the fatigue resistance of the cord.

One embodiment of a specific means for producing a cord made of a PVA-based multifilament yarn having a bending hardness within the above range is a tire cord raw yarn obtained by adding a finishing oil to the PVA-based multifilament yarn, that is, the PVA-based multifilament yarn. Before the multifilament yarn is coded by plying, adhesive treatment, etc., it is under tension, specifically,
Within the temperature range of 160-270°C, preferably 180-250°C, 0.1-3.0 g/d, preferably 0°3-3.
A method of heat treatment for 0.3 to 30 seconds, preferably 1.0 to 10 seconds under a tension of 2.0 g/d can be mentioned.

For the tension heat treatment, a heating tube, heating roll, hot plate, heating liquid, fluidized bed, etc. can be used.

Through such tension heat treatment, the single fibers constituting the PVA multifilament yarn are aligned in a close-packed arrangement within the cross section of the yarn, and this arrangement structure twists and bonds the yarn. When applying an adhesive, it suppresses penetration of the adhesive into the cord, and the bending hardness is 1.
It is thought that it gives the cord a soft performance of 0 to 80q. In general, the tension heat treatment has the effect of stabilizing the structure of the PVA fibers constituting the PVA-based mardifficerament yarn and improving the fatigue resistance of the cord.

Note that applying a finishing oil in the range of 1.2 to 4.0% by weight to the PVA multifilament yarn in advance improves the bending hardness of the twisted cord by subjecting the PVA multifilament yarn to tension heat treatment. It is effective in keeping the thickness within the above range and improving the fatigue resistance of the cord.

The finishing oil used here may contain general ingredients used in fiber manufacturing such as lubricating ingredients, emulsifying ingredients, antistatic ingredients, etc., but the Preferably, it is an oil agent that reduces the thread-system friction coefficient.

From this point of view, the finishing oil applied to the present invention includes silicone-based lubricating components such as organopolysiloxanes represented by higher fatty acid esters, higher alcohol sulfuric esters, dimethylpolysiloxane, and polyalkylene glycol-modified silicones. Oils, fluorine-based oils such as fluorocarbons, polyester-based oils such as linear polyesters and polyester waxes, and preferably silicone-based oils, fluorine-based oils, and polyester-based oils are preferred.

Further, examples of emulsifying components include hydrogenated castor oil, ethylene oxide adducts of stethylamine, and various natural and petroleum-based emulsifying components.

The tire cord made of the above-mentioned PVA multifilament yarn of the present invention has a tensile strength of 8.5 g/d or more, a medium elongation (MDE) of 0.5 to 2.2%, and a dry heat shrinkage rate. (ΔS) is preferably 0.2 to 2.0%.

In other words, if the tensile strength is lower than 8.5 (J/d), it is undesirable because the reinforcing effect on the tire is small. In view of the number of twists of the raw cord, it is preferable that the cord has a tensile strength of at least 11 (J/d) or more.

When using the tire cord of the present invention as a belt reinforcing material, MDE is 0.5% to 1.2%, preferably 0.
．． It is preferably within the range of 8 to 1.2%, and when used as a carcass reinforcing material, it is preferably within the range of 1.0% to 1.9%, preferably 1.2 to 1.7%. . M
If DE is less than 0.5%, the toughness as a tire cord will be poor and the bending hardness will be significantly reduced; 2.
If it exceeds 2%, it is not preferable because the effect of suppressing tire deformation under load decreases.

Further, when the tire cord of the present invention is used as a belt reinforcing material, ΔS is preferably within the range of 0.2% to 1.4%, preferably 0.5% to 162%, and the carcass reinforcing material When used with (), 0.4% to 2.0%,
It is preferably within the range of 0.8% to 1.7%. If ΔS is smaller than 0.2%, it will be difficult to absorb the minute slack of the embedded cord during tire molding, and if it is larger than 2.0%, the cord will undergo a large amount of heat shrinkage during tire molding. As a result, the amount of deformation of the tire cord (under a certain load) in the tire after tire molding increases, reducing the running stability of a radial tire, or causing the tire cord to shrink. However, this is not preferable because it lowers the molding stability of the tire and increases the defective rate.

The tire cord of the present invention having such cord characteristics has a twist coefficient of 500 to 2,500, preferably 900 to 2,500.
It has the feature that it can be set appropriately within the range of 2100 depending on the purpose of use.

Naturally, there is a certain relationship between the twist coefficient, mechanical properties, and fatigue resistance of tire cords, and as the twist coefficient increases, fatigue resistance improves, but the strength, modulus, etc. of the cord Mechanical properties tend to decrease. Also,
The properties required of a tire cord differ depending on the part of the tire where the cord is applied, that is, the reinforced part of the tire.For example, when used as a belt member, mechanical properties, mechanical properties, In particular, there is a strong requirement to improve the modulus, and in the case of carcass members, on the contrary, the requirement to improve the fatigue resistance is more severe than the mechanical properties.

From this point of view, for reinforcing the carcass part, 15
00-2500. Preferably, the twist coefficient is selected within the range of 1,600 to 2,100, and for belt reinforcement, it is 500 to 1,500. Preferably, it is selected within the range of 900 to 1400. That is, in the case of reinforcing the belt part, if the twist coefficient is less than 500,
If it exceeds 1,500, the medium elongation (MDE) of the cord increases, and the high modulus, which is a characteristic required for a belt member, decreases, which is not preferable. On the other hand, in the case of reinforcing the carcass part, if the twist coefficient is smaller than 1500, it will not satisfy the level of fatigue resistance required for the carcass member, and if it is larger than 2500, the cord's medium elongation (MDE) will not be satisfied. ) becomes large and the high modulus property decreases, which is not preferable.

The tire cord of the present invention exhibits excellent cord characteristics no matter which twist coefficient required for the carcass member and belt member is applied. Further, the fineness of the single fibers constituting the PVA multifilament yarn is preferably within the range of 0.5 to 5 denier (d). If the fineness is smaller than 0.56, the multifilament yarn will be damaged during high-order processing such as heating, making it easier to generate fluff, and the strength will decrease, which is not preferable, and if the fineness is larger than 5d, This is not preferable because the multifilament yarn becomes stiff and its flexibility decreases, resulting in a decrease in high-order processability such as the above-mentioned heating and a decrease in the fatigue resistance of the cord.

Next, the high polymerization degree PVA constituting the tire cord of the present invention
A specific embodiment of the method for producing a high strength, high elastic modulus fiber consisting of the following will be described.

First, a PVA-based polymer with a degree of polymerization of at least 2000 is mixed with organic solvents such as dimethyl sulfoxide (DMSO), glycerin, ethylene diamine, ethylene glycol, diethylene triamine, and phenol, water, and inorganic salts such as zinc chloride, rhodan soda, calcium chloride, and aluminum chloride. A solution having a PVA-based polymer concentration of 5 to 25% is prepared by dissolving it in various solvents such as an aqueous solution or a mixed solution thereof.

The obtained solution is extruded as a spinning dope from a multi-hole spinneret having a plurality of holes, usually 20 holes or more, preferably 50 to 5,000 holes. In order to produce multifilament yarns, it is possible to effectively prevent fusion between single fibers during the production process, and it is necessary to draw the yarn until long-period images are no longer observed by the small-angle X-ray scattering method described below. It is necessary to adopt a spinning method that allows for

An example of such a spinning method is a method in which a dry/wet spinning stock solution is once discharged into an inert atmosphere such as air, and then introduced into a coagulation bath to complete coagulation. This method is also industrially advantageous.

Coagulants for completing the pseudo-solidification of the coagulated yarn formed by this wet spinning method include alcohols such as methanol, ethanol, butanol, acetone, benzene, toluene, etc., or one or more of these and DMSO. Examples include mixed solutions with saturated inorganic salts, saturated inorganic salt aqueous solutions, and caustic soda aqueous solutions, but alcohols such as methanol and ethanol, and acetone are preferred.

In addition, although the distance between the spinneret and the coagulation bath liquid level (inert gas atmosphere) is not particularly limited, if it is too short,
For example, if it is smaller than 3 mm, the characteristics of dry/wet spinning will not be fully exhibited, making it impossible to form a dense multifilament yarn, and the spinning stability will decrease, and if it is too long, for example, If the diameter becomes too large, it becomes difficult for the flow of the spinning dope extruded from the spinneret to run stably, and slight yarn shaking may cause the spinning dope flows to come into contact with each other and cause fusion. It is better to set

The obtained coagulated yarn is stretched in a wet state in one or multiple stages, and is usually stretched 2 to 5 times and then dried. It is best to blow turbulent gas inside the fibers to spread out the individual fibers and dry while photographing. By applying an oil treatment to the multifilament yarn before drying with this turbulent gas, it is possible to more effectively prevent sticking and fusion between the single yarns. Further, after drying, a method such as spraying turbulent gas onto the yarn may be applied to remove the fusion between the single fibers remaining in the yarn.

The dry multifilament yarn thus obtained can be heated by heating tubes, heating rolls, heating plates, heating pins, heating liquids,
Hot stretching is performed by applying a heating means such as a fluidized bed. The stretching temperature is lower than the melting point (approximately 250°C) of the PVA-based polymer, but preferably a temperature as close to the melting point as possible, for example within a temperature range of 160 to 250°C.

In addition, the final overall stretching ratio by these hot stretching is
It is preferable to stretch the multifilament yarn by at least 10 times, preferably 12 times or more, until no long-period image is observed in the multifilament yarn by small-angle X-ray scattering measurement.

The PVA-based multifilament yarn constituting the tire cord of the present invention has a structural characteristic as a fiber structure that it does not have a long-period image in the meridian direction in small-angle X-ray scattering measurements. The fact that it does not have a long circumference clear image in the meridian direction means that the orientation of the polymer chains constituting the PVA multifilament yarn in the fiber axis direction is extremely high, and the density difference between the crystalline portion and the amorphous portion is small. It means having a high fiber structure. In fact, such structural characteristics of the PVA multifilament yarn are reflected in the shrinkage rate of the PVA multifilament yarn and the deformation caused by heating when a heated tire cord is embedded in rubber and vulcanized. Both the shrinkage rate and the heating deformation of the cord of the PVA-based multifilament yarn are extremely small. Therefore, the obtained tire cord has a high modulus of elasticity and excellent fatigue resistance due to the integrity and stability of the fiber structure, which suppresses deformation of the tire sidewall and is useful as a carcass reinforcement material. It satisfies the characteristics required for tire cords, such as improved fatigue resistance.

PVA is made of PVA-based polymer with such a high degree of polymerization and has excellent mechanical strength as shown by high strength and high modulus of elasticity.
The means for making a tire cord from a multifilament yarn will be described in detail below.

First, the PVA-based multifilament yarn is heated by a known twisting machine and means so that it has a twist coefficient within the above range suitable for the purpose of use as a tire cord,
The resulting twisted cord is coated with resorcinol formalin latex (hereinafter referred to as
Depping processing is performed using various known adhesives such as RFL) and epoxy resin.

An example of a typical adhesive composition is RF resorcinol (100%): 18.5 g formalin (37%): 27.0 g Na0t ((10
%): 6.1 (1 water: 240.3
gR FL VP Latex (“N1pol” 2518FS manufactured by Zeon Corporation) 4
23, 3 (1 Wed 280.9Cl block SC2
0% RF/L ratio 1/6 RF aging: 25℃ x 6 hours RFL aging, 25℃ In order to increase the strength, it is preferable to increase the TSC of the adhesive (20% or more) to reduce the penetration into the inside of the f?FL cord.

From this point of view, it is preferable to increase the concentration of the RFL and reduce the amount of RFL attached to the cord as much as possible, for example, usually 10% or less, preferably 8% or less.

The cord treated with adhesive in this way is then dried and heat treated, but the treatment method and conditions are as follows:
60-240 seconds, preferably 90-180 seconds in a drying zone at a temperature range of 60°C, preferably 110-150°C;
Dry under a stretch of 0-3%, preferably 0-2%,
Then 160-240°C, preferably 170-220°C
In the heat treatment zone (hot zone) with a temperature range of 0 to 4
%, preferably under a stretch of 1-3% (15000
/2 under a tension of 1-6Kg, preferably 1.5-4Kg) for 20-60 seconds, preferably 30-50 seconds, and finally at 160-240℃, preferably 170-22
1% to 1% in the normal zone at 0°C, preferably 12 to 1%
0% stretch (in the case of 1500D/2, each cord is heated under a tension of 1 to 5 Kq, preferably 1 to 3 Kg for >20 to 60 seconds, preferably 30 to 50 seconds). It is better.

The cord (i.e., after being subjected to adhesive treatment, drying, heat treatment, etc.) through such processing steps.

It has been found that the lower the bending rigidity of the processed cord, the greater the strength of the cord.

Therefore, before winding the cord processed through the above process, for example, in the case of 1500[)/2, the cord is softened under the conditions of an angle of 90 and a tension of 250 g.
It is preferable to reduce the bending rigidity of the treated cord, improve the process passability and handling properties of the cord, and increase the strength of the cord.

Hereinafter, the effects of the present invention will be specifically explained using Examples.

In addition, in the present invention, yarn characteristics, cord characteristics, GY1-bu fatigue life, and X-ray small-angle scattering measurement method were measured by the following methods.

Yarn properties: tensile strength, residual elongation, initial elastic modulus are JIS-
The measurement was performed according to the measurement method specified in L-10i7. In addition, in this measurement method, the sample is taken in a skein shape, and 2
After leaving it for 24 hours in a temperature and humidity controlled room at 0°C and 65% RH, it was twisted 8 times per 10C [11]. Co., Ltd.) with a sample length of 25 cm and a pulling speed of 30 cm/min.The chuck used was an air jaw for cords.

Cord characteristics: (a) Definition of twist coefficient: It is a value defined by the following formula.

Twist coefficient = number of twists (twists/10Cm”) ×J (Fineness of yarn) X (Number of twists) (b) Tensile strength: Measured under the same conditions as the yarn properties.

(c) Dry heat shrinkage rate ΔS: Take the sample in a skein shape, 20℃,
After leaving the sample in a temperature/humidity-controlled room at 65% RH for 24 hours, a load corresponding to 0.1 g/d of the sample was applied to the sample and the length 1 of the sample was measured. The sample measured in 1 was left untensioned in an oven at 180°C for 30 minutes, then taken out of the oven and left in the above temperature/humidity control room for 4 hours, and then again subjected to the above load of 0.1 g/d. The length 11 was measured, and ΔS was measured from the values of 1 and 11 according to the following formula.

Δ5=(l-11>/Ix100(%) (d) Intermediate elongation MDE: In the load-elongation curve obtained when measuring tensile strength, read the elongation under the following constant load,
This value was defined as the intermediate elongation.

If the yarn fineness is 1 soo denier (D), the elongation under a load of 8.75K (l) when two yarns are twisted together.

If the yarn fineness and number of twists are different, correct as follows.

1000[), in the case of two strands twisted together: elongation at 4.5Kg.

10000. In the case of 3 strands: Elongation at 6.75Kq.

In the case of 1800D, two strands twisted together: 8. Elongation at IKtJ.

(e) Bending hardness: Figure 1 shows an example of a cross-sectional view of the device used for measurement. In the figure, 1 is the code of the measurement sample,
2 is a support rod for hooking the cord, 3 is the diameter o, ao
mm wire, 4 is a load cell connected to the support rod 2,
5 is a tension member of the tensile testing machine.

In the figure, a cord 1 with a length of 20 mm is hooked on support rods 2 with an interval of 5 mm (inner dimension), and the bending hardness when a tension member 5 of a tensile tester is hooked on the cord 1 and bent is measured. It was measured and expressed as Durham ((1)).

(to) Glue the crab processing cord to a 1cm square rubber block (
The rubber vulcanization conditions were 153℃, 20 minutes) to
Measured by the so-called "H test", the unit is K (1/
It was expressed in cm.

GY tube fatigue life: Measured according to JIS-L-1017, 1321 (Method A).

However, the angle of the tube was 90 degrees.

X-ray small-angle scattering measurement method: The known Kiessinq Camera
The measurement was performed according to the method used in a). The following conditions were adopted as the measuring device and measurement conditions.

R1J-200 type X-ray generator manufactured by Rigaku Denki Co., Ltd. was used.

CuKa a-ray (using Ni filter), output crab 50KV
-150mA, using 0.3n+mφ collimator,
Transmission method, camera radius: 400 mm, exposure time: 90 minutes, film: Kodak no screen type.

Opening degree: When cutting a multifilament yarn to 50 mm and dividing the filaments, it is the ratio of single fibers that can be divided without damage such as cutting or fibril cracking.
Judgment was made according to the following criteria. The multifilament yarn of the present invention that is substantially free of fusion and adhesion between single fibers means that the following V standard is 90% or more.

○: 90% Δ, 70 to 89%
) 12 wt% dimethyl sulfoxide (DMSO) in PVA
) solution was prepared and this solution was used as a spinning stock solution.

This spinning stock solution was placed in a coagulation bath with a hole diameter of 0 mm installed 6 mm above the surface of the coagulation bath.
．． Dry/wet spinning was carried out through a spinneret with a diameter of 0.8 mm and 750 holes into a methyl alcohol coagulation solution containing 10% by weight of DMSO. The obtained coagulated yarn (multifilament yarn) was washed in a methanol bath to remove DMSO, and then stretched 4 times in a methanol bath and dried.

Subsequently, the fibers are opened by turbulent gas, and the opened multifilament yarn is stretched 5.1 times in a dry heat tube heated to 240°C, and an oil agent is applied and wound to obtain the indicated fineness (D). 1500. Number of filaments is 750, opening degree is 9
It is a multifilament yarn with substantially no fusion of 0% or more, has physical properties of tensile strength of 17.0 g/d, tensile modulus of elasticity of 350 a/d, and has long-period properties as measured by small-angle X-ray scattering measurement. A raw yarn for tire cord that does not show images was obtained.

Subsequently, the tire cord yarn was treated in a dry heat tube heated to 245° C. for 10 seconds under a tension of 0.5 Q per denier, that is, 750 g per yarn. 33 per 10cm of first twist of the obtained heat-treated yarn
Two yarns are twisted together at a rate of 33 times per 10 cm of ply twist.
It was made into a raw code.

Next, this raw cord was coated with an RFL adhesive using a computer treater manufactured by Ritter, dried, and subjected to tension heat treatment to produce a treated cord.

Here, the drying conditions are 150°C for 120 seconds, constant length, tension heat treatment, heat treatment zone at 200°C for 30 seconds, stretch rate 3.5%, normal zone at 200°C for 30 seconds, relaxation rate 0.5%. did.

For comparison, in Example 1, a treated cord was created by twisting the yarn for tire cord without subjecting it to tension heat treatment, and then subjecting it to the above-mentioned twisting and dipping. This is shown as Comparative Example 1 in Table 1.

From the data in Table 1, the cord of Example 1 has lower strength and fatigue resistance (GY fatigue life) than the treated cord of Comparative Example 1, which was not subjected to tension heat treatment before twisting. Excellent and adhesive attachment to the cord @
Although the amount was slightly lower than that of the cord of Comparative Example 1, there was no problem with adhesion to rubber.

Examples 2 and 3, Comparative Examples 2 and 3 In Example 1, treated cords were made using raw yarn for tire cords obtained by tension heat treatment under the conditions shown in Table 1, which are different from those in Example 1. We created the code and evaluated its code characteristics.

However, the twisting yarn and dipping conditions were the same as in Example 1. The results are shown in Table 1.

(Hereinafter, blank space) Table 1 Example 4 Completely saponified type with a degree of polymerization of 4600 (degree of saponification 99.8%)
(above) 10% dimethyl sulfoxide (DM) of PVA
SO> solution was prepared, and this solution was used as a spinning stock solution for dry/wet spinning in the same manner as in Example 1. The obtained coagulated yarn (multifilament yarn) was washed in a methanol bath and D
After removing MSO, it was stretched 4 times in a methanol bath,
Dry. After drying, the multifilament yarn opened by turbulence was drawn 5.3 times in a duplex heated to 240°C, coated with an oil agent having the same composition as in Example 1, and wound up to give the indicated fineness ( D > 1500 [)
, the number of filaments is 750, the opening degree is 90% or more, there is virtually no fusion, and the tensile strength is 18.5 g/d.
A multifilament yarn having physical properties with a tensile modulus of 410 g/d and showing no long-period pattern by small-angle X-ray scattering measurement was obtained.

The obtained multifilament yarn was heated in a dry heat tube heated to 245°C to apply a tension of 0.8 (J/denier) and heat-treated for 5 seconds. The yarn was used as a yarn, and two strands were twisted together at a rate of 22 times per 10 cm of first twist and 22 times per iocm of second twist to obtain a raw cord.

Next, this raw cord was coated with an RFL adhesive using a computer processor manufactured by Ritter, dried, and subjected to tension heat treatment to produce a treated cord.

Here, the drying conditions are 150°C for 120 seconds, constant length, tension heat treatment, heat treatment zone at 200°C for 30 seconds, stretch rate 1.5%, normal zone at 200°C for 30 seconds, relaxation rate 0.5%. did.

The obtained tire cord exhibits physical properties such as significantly higher strength and intermediate elongation than conventional PVA tire cords, and as shown in the data below, it has extremely excellent performance as a belt member for radial tires. It was found that it had.

Twist coefficient: 1180 Tensile strength: 13,8 (j/d ΔS: 1.2% MDE: 0.9% Cord bending hardness: 51g Adhesive crab 16.2 g/cm GY fatigue life: 26m1n.

[Brief explanation of drawings]

Figure 1 shows one of the devices used to measure the bending hardness of cords.
It is a sectional view showing an example. 1: Cord of the measurement sample 2: Support rod for hooking the cord 3: Wire with a diameter of approximately 0.80 mm

Claims (2)

[Claims] (1) A multifilament yarn made of a polyvinyl alcohol polymer having a degree of polymerization of at least 2000 and having a tensile strength of 15 g/d or more and an initial elastic modulus of 250 g/d or more and substantially free from inter-fiber fusion. The bending hardness (S
A tire cord made of polyvinyl alcohol fibers having improved bending hardness and having b) in the range of 10 to 80 g. (2) In claim 1, the tire cord comprises at least 300 multifilament yarns.
A tire cord made of a polyvinyl alcohol-based fiber having improved bending hardness, which is made of a polyvinyl alcohol-based polymer having a degree of polymerization of 0, and having a tensile strength of 17 g/d or more and an initial elastic modulus of 320 g/d or more.