JPH01201519A - Production of polyethylene terephthalate based polyester fiber - Google Patents

Abstract

PURPOSE:To obtain the title fiber, having a high tenacity and elastic modulus and suitable as industrial materials, etc., by subjecting a highly oriented low crystalline polyester fiber, containing ethylene terephthalate as main constituent units and having specified birefringence ratio and specific gravity to dipping treatment in a specific organic solvent and drawing the resultant fiber. CONSTITUTION:A yarn 2 obtained by melting a polyester containing ethylene terephthalate units as main constituent units while heating, discharging and spinning the resultant melt through a spinneret 1 is oiled with an oiling device and taken off by take-off rollers 3 to provide a highly oriented low crystalline polyester fiber having a birefringence ratio (DELTAn) and specific gravity (SG) within the ranges expressed by formulas I and II. The obtained fiber is then subjected to dipping treatment in a solution bath containing an organic solvent (e.g. 95% aqueous solution of acetone) exhibiting 7.5-15.0 solubility parameter, subsequently or once treated to provide a state without containing the organic solvent and then drawn to afford the aimed fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing ethylene terephthalate polyester fibers, and more particularly to a method for drawing highly oriented low specific gravity polyester fibers.

The production method of the present invention is particularly suitable as a method for obtaining high-strength, high-modulus polyester fibers, and the fibers obtained by the method of the present invention are mainly used for industrial materials.

(Prior Art) Ethylene terephthalate polyester fibers are usually obtained industrially by melt-spinning a polymer having an intrinsic viscosity of less than 1.2 at a temperature above the melting point, followed by hot drawing and heat treatment.

The physical properties of the drawn yarn obtained by such conventional techniques are high strength filaments for industrial materials, with a breaking strength of 6 to 10 g/d,
The initial elastic modulus is 80 to 160 g/d, and substantially the highest level of physical property values that can be obtained industrially is a breaking strength of 9.5 g/d and an initial elastic modulus of 120 g/d.

On the other hand, as a method for improving physical properties, a method has long been considered in which highly oriented polyester fibers with low specific gravity and low crystallinity are first formed and then subjected to stretching heat treatment. According to the -210590 publication,
It is known that highly oriented, low specific gravity polyester fibers can be obtained by stretching with laser light, and that physical properties can be improved by heat treating highly oriented, low specific gravity polyester fibers.

In addition, it is reported in Kobunshi Proceedings (Vol. 142, PP 159) that highly oriented polyester fibers with low specific gravity can be obtained by drawing at a temperature below the glass transition temperature.
~166.1985).

Furthermore, according to JP-A-58-169513, regarding the production of high-speed spun amorphous polyethylene terephthalate yarn for texturing, the spun yarn is rapidly cooled in a liquid bath placed below the spinneret. It is known.

(Problems to be Solved by the Invention) In order to improve the physical properties of polyester fibers, when performing drawing heat treatment on polyester fibers with high orientation, low specific gravity, and low crystallinity, it is necessary to rapidly crystallize the polyester fibers by applying only a small amount of heat. There is a problem in that the stretchability is low and it is difficult to obtain sufficiently high physical properties.The main objective of the present invention is to solve this problem including the problems with the conventional method. It is an object of the present invention to provide an excellent stretching method for increasing the strength and modulus of oriented low-density polyester fibers.

(Means for Solving the Problems) That is, the present invention is a polyester having ethylene terephthalate units as a main constituent unit, and having a birefringence Δn and a specific gravity SG in the ranges shown by the following formulas (a) and (b). Highly oriented low crystalline polyester fibers in the range of 7.5 to 15.0
The ethylene terephthalate polyester fiber is immersed in a liquid bath containing an organic solvent having a solubility parameter of It is a manufacturing method.

△n≧55G −6,64−−−−−(a) Δn≧0
．． 100 ・・・・・・・・・－・・・・・・・・・・
(b) The polyester component forming the polyester fiber used in the present invention has ethylene terephthalate units as its main constituent unit, and is usually a polyester or homopolyester or a polyester mixture thereof containing 85 mol% or more of ethylene terephthalate units. It is. Copolymerization components other than terephthalic acid and ethylene glycol include isophthalic acid, 2,6-naphthalene dicarboxylic acid, adipic acid, sebacic acid, sheracic acid, diethylene glycol, propylene glycol, cyclohexane dimetatool, P-oxybenzoic acid, 3 Examples include 5-di(carbomethoxy)benzenesulfonic acid metal salts and derivatives thereof, but are not limited to the above specific examples.

The fiber used in the present invention has a relationship between birefringence Δn (parameter of orientation degree) and specific gravity SG (parameter of degree of crystallinity) that satisfies equation (a), and at the same time, the birefringence (80) satisfies equation (b).
It satisfies the formula.

If the formula (a) is not satisfied, the fiber has a degree of orientation, that is, Δn
The density increases more than the increase in density due to the improvement in molecular chain backing properties associated with the increase in , and in this case, oriented crystallization occurs.

The fibers used in the present invention, which have such a structure, have fewer crystallized parts when further drawn and heat treated to improve physical properties, so it is much easier to improve physical properties than ordinary oriented crystallized fibers. However, in the ordinary stretching heat treatment method, crystallization occurs before stretching occurs, making it impossible to achieve the intended effects of the present invention.

The birefringence index (Δn) of the fiber used in the present invention satisfies (b) 2, and preferably Δn is 100 x 10
-h~270X10 bow teal.

If Δn is lower than 100 I imagine that it will be stretched too much and fall through.

The lower limit of the preferred specific gravity (SC) of the fibers used in the present invention is 1.335. If it is lower than 1.335, voids are generated in the fiber, which significantly reduces the mechanical properties, so it is not preferable.Even if (SG) is within the appropriate range, it is preferable if voids are generated. do not have.

The fiber used in the present invention has high orientation quality as seen from such Δn and SG.

The present inventors investigated the most effective method for stretching polyester fibers having such high orientation quality, and as a result, they arrived at the present invention.

In the present invention, when drawing the highly oriented non-defective polyester fibers, the fibers are immersed in a liquid bath containing an organic solvent having a solubility parameter of 7.5 to 15.0.

The most important point is that this dipping treatment swells the fibers and increases their drawability.

The liquid bath used for the immersion treatment here needs to be a 2-volume liquid that is easily compatible with the ethylene terephthalate polyester.
．． It has been found that a solvent consisting of an organic solvent of 5 to 15.0% is easily compatible with 80% polyester fibers, but the mechanism is not yet well understood.

The solubility parameter of polyethylene terephthalate is
10.7, and the solubility parameters of the organic solvent that swells polyethylene terephthalate are 9.7 and 12.
There are two maxima of the swelling effect near 0. Therefore, the solubility parameter of the organic solvent is 9.5 or more, 12.5
The following are preferred, for example chlorobenzene (9,5
: Solubility parameters (enter only numerical values below), nitrobenzene (10,0), dichloromethane (9,7), nitromethane (12,30), acetone (10,0), dioxane (10,05), benzyl alcohol (11,97)
), dimethylformamide (12,1), etc. are typical examples, but the present invention is not limited thereto.

If the solubility parameter of the organic solvent is less than 7.5 or higher than 15.0, the swelling effect will decrease and the desired improvement in stretchability will not be achieved, which is not preferred.

The solubility parameter referred to here is a characteristic value of a liquid that is a measure of miscibility between liquids, and is J, 11.

It was proposed by the former 1debrand and is represented by δ. δ = where E is the molecular cohesive energy of the liquid and V is the molecular volume.
(E/V)" and is a material constant that depends only on temperature.

Further, the organic solvent used in the present invention is one that swells the undrawn yarn at a temperature lower than the glass transition temperature of the undrawn ethylene terephthalate polyester yarn, thereby lowering its glass transition temperature. Furthermore, to improve the dipping speed and swelling effect of the solution,
It is more preferable that the organic solvent is acetone, that the solution is an aqueous solution, and that the temperature of the solution is lower than the boiling point.

Moreover, among the ethylene terephthalate-based polyester fibers, polyethylene terephthalate fibers are most preferable because of the high breaking strength and initial elasticity that can be obtained.

Naturally, in view of the spirit of the present invention, it is most preferable to allow the solution to penetrate into the center of the fibers that have been subjected to the soaking treatment. Needless to say, in order to penetrate the solution into the center of the fiber, appropriate dipping time, dipping temperature, and chemical composition of the solution are required according to the birefringence Δn and specific gravity SG level of the fiber.

The dipping conditions required for the solution to penetrate into the core of the fiber can be determined by observing the treated fiber under an interference microscope.

FIG. 2 (a, b, c, d) shows the change behavior of interference fringes depending on the untreated system and the degree of immersion treatment, and it can be clearly seen that the solution penetrates as the treatment time increases.

In this way, the highly oriented non-quality polyester fibers subjected to the dip treatment are drawn at a stretching temperature of 100 to 350°C according to a conventional method.
, a stretching heat treatment is performed at a stretching ratio of 1.02 to 2.00 times, but during the stretching heat treatment, rather than performing heated roller stretching, a combination of a feed roller at room temperature, a heater installed between the rollers, and a draw roller is used. preferable.

In order to improve the physical properties, it is preferable to perform multi-stage stretching of two or more stages, followed by a relaxing treatment, and then wind up.

Next, a method for measuring physical property values used in the present invention will be explained.

<Method for measuring intrinsic viscosity (■)> In the present invention, the intrinsic viscosity (■) of ethylene terephthalate polyester is the intrinsic viscosity [η] measured at 30°C using a P-chlorophenol/tetrachloroethane-3/1 mixed solvent. is converted into the intrinsic viscosity IV of phenol/tetrachloroethane=60/40 using the following formula.

rV = 0.8325 X (η) +0. oos〈
Measuring method of fiber fineness〉 In a test room under standard conditions (temperature 20 ± 2°C, relative humidity 65 ± 2%), an autobibro type fineness measuring device manufactured by Saatchi ■ DENIERCOMPUT [! The fineness (denier, d) of single fibers was measured using R[1C-11B type.

However, the fiber measurement sample length was 50 mm.

<Measurement method of fiber strength> The tensile strength (strength) of fibers is determined according to JIS-L-1013 (1
In accordance with 7.5.1 of 981), in a test room under standard conditions, a constant speed extension type universal tensile tester TE manufactured by Toyo Baldwin ■ was used.
The tensile strength of single fibers was measured using NSILON UTM-III.

However, the measurement conditions were as follows: using a 5 kgf tensile load cell, pulling the sample at a gripping interval of 10c+a at a pulling speed of 10cm/min (extension speed of 100% of the gripping interval per minute), and a recording paper feed rate of 100cm/min. Measure the load (gf) when the material is cut, and calculate the tensile strength (gf) using the following formula.
/d) was calculated and defined as the strength (g/d).

The initial tensile resistance (initial tensile modulus) of the fiber is JIS-
The test was conducted using the same method as the above method for measuring fiber strength according to 7.5.1 of L-1013 (1981), and a load-elongation curve was drawn on the recording paper. From this figure, JIS-L-1
7 of 013 (1981). Calculate the initial tensile resistance (gf/d) using the initial tensile resistance calculation formula described in 1O,
It was defined as the initial tensile modulus (g/d).

Measuring method of specific gravity> Prepare a density gradient tube made of n-hebutane and carbon tetrachloride, place a sufficiently defoamed sample into the density gradient whose temperature is controlled to 30°C ± 0.1°C, and The sample position in the density gradient tube after being left for a while was read on the scale of the density gradient tube, and the value was converted into a specific gravity value from the density gradient tube scale - specific gravity calibration graph using a standard glass float, and measured at n = 4. As a general rule, read specific gravity values to four decimal places.

Measuring method of birefringence (Δn) A Nikon polarizing microscope Po1l type Lyc Perec compensator was used, and a spectral light source activation device (Toshiba 5LS-3-B type) was used as the light source (Na light source), 5
A sample cut at a 45″ angle to the fiber axis of ~6+wm length is placed on a glass slide with the cut side facing up.

Place the sample slide glass on the rotating stage, adjust the rotating stage so that the sample is at a 45° angle to the polarizer, insert the analyzer, set the dark field, and set the compensator to 30°. count the number of stripes (n pieces). Turn the compensator clockwise to measure the scale a1 of the compensator at the point where the sample first becomes darkest.Turn the compensator clockwise to measure the scale of the compensator at the point where the sample first becomes darkest. (read up to 1/10 scale), return the compensator to 30, remove the analyzer, measure the diameter d of the sample, and calculate the birefringence (80) based on the following formula (20 measurements) average value).

Δn=r'/d(1"Ni-Lapsion,=nλ.+
ε) λ. -589,8mμ 82542 compensator manual C/100
1 determined from 00 and i = (a-b) (: difference in compensator reading) (Example) An example is shown below, but it goes without saying that the present invention is not limited to this example. do not have.

Example 1 Polyethylene terephthalate having an intrinsic viscosity of TV 1.0 was spun at a temperature of 310''C, and 1.5 g/per single hole was spun from a spinneret having a spinneret hole diameter of 0.4 M and a spinneret number of 24 holes.
The sample was discharged at a discharge speed Vo of 11.4 m/min and taken up at a take-up speed Vw of 4200 m/min.

The spun yarn was introduced into a quench tube. 5 cr from the top of the quench tube
a is a state in which the flow is extremely slow due to the rectification mechanism;
H was set to 25 cm, and at the lower end of the quenching tube 25 cm downstream from the upper end, the fluid flow rate in the downstream direction was adjusted to 200 On+/min, and the quenching tube was installed at a position 36 cm directly below the spinneret. . The cooling fluid used at this time was water at room temperature (25°C).

The obtained thread has a Δn of 150 x 10-' and a specific gravity of 1.
It was 3528. The birefringence Δn distribution within the cross section of this yarn is such that Δn at the yarn surface is 15% higher than Δn at the yarn center.
It was larger by X 10-3.

Next, the yarn thus obtained was immersed in a 95% acetone aqueous solution at 22°C for 30 minutes, and then stretched under the stretching conditions shown in Table 1 below. The yarn quality of the obtained drawn yarn is shown in Table 1.

Example 2 Highly oriented low specific gravity yarn obtained in Example 1 (Δn: 150X1
0-', specific gravity: 1.3528), and was stretched under the same stretching conditions as in Example 1, except that the number of stretching, the number of heat setting, and the stretching ratio were changed in the stretching stage.

The yarn quality of the obtained drawn yarn is shown in Table 1.

Comparative Example 1 Highly oriented low specific gravity yarn obtained in Example 1 (△n: 150Xl
O-', specific gravity: 1.3528), and was stretched under the stretching conditions shown in Table 1 below without any acetone aqueous solution immersion treatment. The quality of the drawn yarn obtained is
Shown in the table.

Comparative Example 2 Highly oriented low specific gravity yarn obtained in Example 1 (Δn: 150X1
0-'', specific gravity: 1.3528), the number of stretching was adjusted at the stretching stage without immersion treatment in acetone aqueous solution.
Comparative Example 1 except that the number of heat fixing times and stretching ratio were changed
Stretching was carried out under the same stretching conditions.

The yarn quality of the obtained drawn yarn is shown in Table 1.

Table 1 (Effects of the Invention) The present invention is constructed as described above, and as is clear from the above specific examples, the method of the present invention has a better effect on the yarn obtained by drawing than the conventional method. It has excellent mechanical properties (breaking strength, initial elastic modulus, toughness characteristics), and has unprecedented
It is possible to provide a novel stretching method that makes it possible to increase the strength and modulus of highly oriented low specific gravity polyester fibers.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing an apparatus for producing highly oriented, low-crystalline polyester fibers used in the present invention. 2 and 2 are diagrams showing the results of interference microscopic observation of fibers before and after immersion treatment in an a-solvent solution bath according to the present invention. 1: Spinneret 2: Thread 3: Transaction roller 4: Oil agent application device Patent applicant Toyobo Co., Ltd. (Keyaki2I!1 abεl: Unprocessed system C: Processing stage):
Microentery d: End of treatment J

Claims (1)

[Claims] (1) Highly oriented low-crystalline polyester fibers that are polyester whose main constituent units are ethylene terephthalate units and whose birefringence Δn and specific gravity SG are within the ranges shown by the following formulas (a) and (b) are 7.5 Ethylene terephthalate characterized by being immersed in a liquid bath containing an organic solvent exhibiting a solubility parameter of ~15.0, then subsequently or once treated to a state substantially free of the organic solvent, and then stretched. Method for manufacturing polyester fibers. Δn≧5SG-6.64------------(a) Δn≧0.100---------(b)