JP2003003324A - Method for producing polyester fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester fiber having high strength, high elastic modulus and low shrinkage by compatibilizing high strength, high elastic modulus and low shrinkage which are unattainable by conventional polyester fiber. SOLUTION: The polyester fiber is produced by extruding a molten polyester from a spinneret, taking up the extruded fiber at a speed of 1,500-4,000 m/min and drawing the fiber in or after the treatment with a supercritical fluid or a fluid similar to the supercritical fluid at 20-100 deg.C under a pressure of 7-25 MPa.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester fiber suitable for industrial materials and a method for producing the same, and more particularly to a polyester fiber having high strength, high elastic modulus and low shrinkage and a method for producing the fiber. It is provided.

[0002]

2. Description of the Related Art A polyester high-strength yarn represented by a polyester tire cord is an organic fiber having an excellent balance in physical properties and cost, and is widely and widely used as a fiber for industrial materials. Among them, automobile tires, particularly passenger car tires, are required to be lightweight in order to improve the ride comfort and steering stability during high-speed traveling, and to save fuel consumption, because the tire structure is becoming more radial.
As a fiber for reinforcing a tire, a fiber having high strength, high elastic modulus and low shrinkage is strongly demanded. Further, when used for a large tire, improvement in fatigue resistance is required.

In order to meet such market demands, for example, Japanese Patent Publication No. 58-4089 and Japanese Patent Publication No. 63-528.
A polyester fiber having excellent dimensional stability and a high elastic modulus has been proposed by obtaining a highly oriented undrawn yarn by high tension by high speed spinning as seen in Japanese Patent Laid-Open Publication No. JP-A No. 2003-242242 and drawing it. Further, Japanese Patent Publication No. 1-276164 discloses a spinning speed of 2
There has been proposed a method for obtaining an excellent high elastic modulus and low shrinkage ratio fiber by drawing a highly oriented undrawn yarn having a birefringence Δn of 0.113 of 2,000 to 5,500 m / min. There is.

As described above, it is known that a polyester fiber having a higher elastic modulus and a lower shrinkage can be obtained by spinning at a higher speed, but at the same time, the strength of the fiber is lowered, which is not preferable as a fiber for industrial materials. . It is considered that the cause of this decrease in strength is yarn unevenness between single yarns or within single yarns due to high-speed spinning, and in particular, the defect structure due to the orientation or structural difference between the yarn surface portion and the central portion within the single yarn. Is believed to be the main cause.

[0005]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a low shrinkage, high elastic modulus polyester fiber having sufficient strength and a method for producing the same.

[0006]

That is, according to the present invention, after polyester is melted and discharged from a spinneret, 1500 to 400
This is achieved by drawing at a drawing speed of 0 m / min and then stretching during or after treatment with a supercritical fluid or a similar fluid. Specifically, the birefringence Δn of the polyester fiber after being taken out is 0.8 or more, and the method for producing a polyester fiber as described above. The main component of a supercritical fluid or a fluid similar thereto is carbon dioxide, wherein the method for producing a polyester fiber as described above. The method for producing a polyester fiber as described above, wherein the treatment temperature with the supercritical fluid or a fluid similar thereto is 20 ° C. or higher and 100 ° C. or lower. Processing pressure of supercritical fluid or similar fluid is 7MP
The method for producing a polyester fiber as described above, which is a or more and 25 MPa or less. The method for producing a polyester fiber as described above, wherein the treatment time T with the supercritical fluid or a fluid similar thereto is within the range of the following relational expression. 0.3 × D <T <1.5 × D T: Processing time (minutes)
D: Single yarn fineness (dtex) draw ratio is 2 to 5 times, The method for producing polyester fiber as described above, wherein

The present invention will be described in detail below. The polyester in the present invention is a polyester having terephthalic acid as a main acid component and at least one glycol, preferably at least one alkylene glycol selected from ethylene glycol, trimethylene glycol and tetramethylene glycol as a main glycol component. And Further, it may be a polyester in which a part of the terephthalic acid component is replaced with other difunctional carboxylic acid component, and / or a part of the glycol component is replaced with the above-mentioned glycol or other diol component other than the main component. It may be polyester. Examples of the bifunctional carboxylic acid other than terephthalic acid used here include isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, β-
Examples thereof include aromatic, aliphatic and alicyclic bifunctional carboxylic acids such as hydroxyethoxybenzoic acid, p-oxybenzoic acid, adipic acid, sebacic acid and 1,4-cyclohexanedicarboxylic acid. Examples of the diol component other than the glycol include cyclohexane-1,4
Examples thereof include aliphatic, alicyclic and aromatic diol compounds such as dimethanol, neopentyl glycol bisphenol A and bisphenol S, and polyoxyalkylene glycol. Further, polycarboxylic acids such as trimellitic acid and pyromellitic acid, polyols such as glycerin, trimethylolpropane and pentaerythritol, and 5 in the range where the polyester is substantially linear.
A monomer having a trifunctional or higher functional ester-forming group such as hydroxyisophthalic acid or 3,5-dihydroxybenzoic acid can be used.

In the present invention, the polyester fiber composed of the above dicarboxylic acid component and diol component is
It is particularly preferable that 80 mol% or more of the repeating units are ethylene terephthalate units.

Further, a small amount of any other polymer, an antioxidant, an antistatic agent, a dye improving agent, a dye, a pigment, a matting agent, an optical brightening agent, inert fine particles and the like are added to the polyester. The agent may be contained. In particular, when adding inert fine particles, either the external precipitation method or the internal precipitation method can be adopted.

As a method of obtaining such polyester,
It is not necessary to employ special polymerization conditions, and the reaction product of a dicarboxylic acid and / or its ester-forming derivative and a glycol can be polycondensed to be synthesized by any method adopted for producing a polyester. it can.

In the production of the polyester fiber of the present invention, conventional spinning conditions can be adopted, but the spinning speed is 150.
0 to 4000 m / min, preferably 2000 to 4000 m
Spinned at a speed of 1 / min. Even with the modified polyester of the present invention at a spinning speed of 1500 m / min or less, under ordinary spinning conditions, sufficient spinning stress for promoting oriented crystallization during spinning cannot be imparted. It is possible to induce oriented crystallization even at a spinning speed of 1500 m / min or less by increasing the degree of polymerization of the polymer and increasing the melt viscosity, but the cost of solid phase polymerization increases and the productivity is low. It is expensive and impractical.

Spinning at a speed of 4000 m / min or more is preferable in view of theoretical productivity, but the problems that must be solved engineeringly, such as the control of the accompanying flow that occurs during spinning, become large, and spinning Unless the device is modified, yarn breakage during spinning occurs frequently, which is not preferable.

As described above, the fibers that are drawn at a high speed and have a high orientation generally have a structural difference in the yarn cross-sectional direction, and the skin, that is, the fiber outer layer side, has a high degree of orientation and is crystallized.
The core, that is, the inner layer portion has a low degree of orientation.

In the present invention, the supercritical fluid means a fluid at a temperature and pressure exceeding the critical temperature and the critical pressure. This state is a state in which it cannot be said that it belongs to either the gas phase or the liquid phase, and has the same degree of mobility as that of gas, although the density is about the same as that of liquid. Therefore, the supercritical fluid has the advantage that it permeates even the details of the fiber structure and plasticizes the polyester.

The permeation of the supercritical fluid and the plasticization by it have the effect of permeating even into the inside of the polyester crystal and plasticizing the crystal itself unlike the conventional plasticization by a plasticizer or the like. Further, the polyester treated with this supercritical fluid retains its structure to some extent and retains its plasticized state even after the treatment. The carbon dioxide has a critical temperature of 31.1 ° C. and a critical pressure of 7.2 MPa.

The fluid similar to the supercritical fluid in the present invention is a fluid having the effect of plasticizing the polyester as described above, and specifically refers to a fluid in a subcritical state. The fluid in the subcritical state refers to a fluid having a critical temperature or a critical pressure or higher, and particularly a fluid having a critical pressure or higher in the present invention. Since the fluid in the high pressure state penetrates into the details of the fiber structure and plasticizes the polyester as in the supercritical state, it has the same effect as in the supercritical state in the present invention.

As described above, carbon dioxide in the supercritical or subcritical state has the effect of plasticizing the polymer, and when treated for a short time so that the supercritical or subcritical fluid does not penetrate into the interior, the orientation of the fiber outer layer Since only this is relaxed, the orientation difference between the outer layer and the inner layer of the yarn is reduced, the draw ratio is dramatically improved, and a polyester fiber having high strength, high elastic modulus, and low shrinkage can be obtained.

Carbon dioxide is preferred as the main component of the supercritical or subcritical fluid in the present invention. Carbon dioxide enters a supercritical state from a relatively low temperature and a low pressure, is easy to handle as a supercritical fluid, and is basically inert, so that it does not react with the polyester being processed, and thus is easy to process.

The treatment temperature of the polyester fiber with the supercritical or subcritical fluid in the present invention is 20 ° C. or higher and 10
It is 0 ° C. or lower, more preferably 20 ° C. or higher and 80 ° C. or lower. This is because if the treatment temperature is too low, the fiber outer layer cannot be relaxed, and if the treatment temperature is high, crystallization of the fiber inner layer is induced, leading to a reduction in the draw ratio.

The processing pressure is preferably 7 MPa or more and 25 M
Pa or less, more preferably 15 MPa or more and 20 MPa or less. If the treatment pressure is too low, the outer layer cannot be relaxed, which is not preferable. From the viewpoint of promoting the relaxation of the outer layer, it is preferable that the treatment pressure is high, but from the viewpoint of the capacity of the apparatus or the cost, a pressure of 25 MPa or more is not practical because it is difficult to manufacture.

The processing time T is preferably within the range of the following relational expression. 0.3 × D <T <1.5 × D T: Treatment time (minutes) D: Single yarn fineness (dtex) If the treated face is short, the relaxation of the outer layer does not proceed sufficiently, which is not preferable. If it is too long, the influence of supercritical carbon dioxide extends to the inner layer, the inner layer is further relaxed or crystallized, and the draw ratio decreases, which is not preferable. The time required for the supercritical fluid or a similar fluid to reach the inner layer naturally depends on the fineness of the single yarn, and if it is within the range of the above formula, it is possible to prevent the penetration to the inner layer and promote the relaxation of the exterior portion.

In the present invention, stretching is performed according to a standard method during or after the treatment of the polyester fiber with the supercritical or subcritical fluid. The stretching method is not particularly limited, and for example, hot roller stretching, steam jet stretching, pin stretching and the like can be used for stretching.

The stretching temperature is preferably above the glass transition point of the polyester and below the melting point of -20 ° C. Below the glass transition point, the strength decreases due to thread unevenness, and the melting point is -20 ° C.
The above causes the yarn to be fused, which causes a decrease in strength.

The stretching ratio depends on the orientation of the polyester fiber before treatment with carbon dioxide in the supercritical or subcritical state, but is preferably 1.2 times or more and 5 times or less. If the stretching ratio is low, sufficient strength is not exhibited and the object of the present invention cannot be achieved. If the draw ratio is high, yarn breakage will occur frequently, causing not only fluff but also a decrease in strength.

[0025]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. The evaluation methods of various properties were according to the following methods. Intrinsic viscosity: The polymer was dissolved in a mixed solvent of parachlorophenol / tetrachloroethane = 3/1 at a concentration of 0.4 g / dl, and 30
It was measured at ° C.

Strength / elongation: According to the definition of JIS-L1017, 24 in a room temperature and humidity controlled at 20 ° C. and 65% RH.
After leaving for a period of time, a tensile strength tester, a breaking elongation,
The initial elastic modulus was obtained.

Dry heat shrinkage: Take a sample in a skein shape, and
After leaving it in the temperature control room at ℃ and 65% RH for more than 24 hours,
A sample with a length of l0 measured under a load equivalent to 0.1 g / d of the sample was placed in an oven at 160 ° C in a tensionless state for 3 hours.
After leaving it for 0 minutes, it was taken out from the oven, left for 4 hours in the temperature control room, and again calculated from the length l1 measured by applying the above load. Dry heat shrinkage = {(l0-l1) / l0} × 100 (%)

Birefringence Δn: Measured by a Berek compensator method using a polarizing microscope.

(Example 1) 100 terephthalic acid was added to a reactor.
Take 250 parts by mole, ethylene glycol 200 parts by mole, antimony trioxide 0.025 parts by mole, and triethylamine 0.3 parts by mole as a stabilizer at an internal pressure of 2.5 kg / c.
The dehydration reaction was performed for 150 minutes at m2. Then, the temperature was gradually raised and the pressure was reduced to carry out a polycondensation reaction at 275 ° C. and 0.1 mmHg up to a predetermined torque. After the reaction is completed, the polymer is made into chips by a conventional method, and further 230 ° C, 0.01 mmHg
Solid phase polymerization was performed under vacuum to obtain a polyester chip having an intrinsic viscosity of 1.0. This was spun and wound at a spinning temperature of 310 ° C. and a winding speed of 4000 m / min. The obtained fiber had Δn = 0.110 single yarn fineness of 10 dtex. The obtained fiber was treated with supercritical carbon dioxide at a temperature of 40 ° C. and a pressure of 20 MPa for 10 minutes and then stretched 3 times at a heater temperature of 120 ° C. with a slit heater. Stretched yarn has a strength of 10c
N / dtex, initial elastic modulus 140 cN / dtex, dry heat shrinkage 2.8
%, And the polyester fiber had high strength, high elastic modulus, and low shrinkage. (Comparative Example 1) A polymer was obtained in the same manner as in Example 1 and, after spinning in the same manner, a heater temperature of 1 was obtained using a slit heater.
The film was stretched 1.7 times at 20 ° C. The obtained fiber had a strength of 6.5 cN / dtex, an initial elastic modulus of 140 cN / dtex and a dry heat shrinkage of 2.8%, and although it had a high elastic modulus and low shrinkage, it was inferior in strength.

[0030]

[Effects of the Invention] High strength, high elastic modulus, and low shrinkage, which were not compatible with conventional polyester fibers, are achieved.
We are now able to provide polyester fibers with excellent elasticity and low shrinkage.

Claims (7)

[Claims] 1. A polyester characterized in that after the polyester is melted and discharged from a spinneret, the polyester is drawn at a drawing speed of 1500 to 4000 m / min, and then stretched when or after being treated with a supercritical fluid or a similar fluid. Fiber manufacturing method. 2. The method for producing a polyester fiber according to claim 1, wherein the birefringence Δn of the polyester fiber after being taken out is 0.8 or more. 3. The method for producing a polyester fiber according to claim 1, wherein the main component of the supercritical fluid or a fluid similar thereto is carbon dioxide. 4. The method for producing a polyester fiber according to claim 1, wherein the treatment temperature with the supercritical fluid or a fluid similar thereto is 20 ° C. or higher and 100 ° C. or lower. 5. The method for producing a polyester fiber according to claim 1, wherein the treatment pressure of the supercritical fluid or a fluid similar thereto is 7 MPa or more and 25 MPa or less. 6. The method for producing a polyester fiber according to claim 1, wherein the treatment time T with the supercritical fluid or a fluid similar thereto is within the range of the following relational expression. 0.3 × D <T <1.5 × D T: Processing time (min) D: Single yarn fineness (dtex) 7. The method for producing a polyester fiber according to claim 1, wherein the draw ratio is 2 to 5 times.