JP7600685B2 - Polyester fiber - Google Patents

Description

The present invention relates to a polyester composition and a polyester fiber.

Polyesters, particularly polyethylene terephthalate, are widely used in textile applications.
In particular, in the case of fibers for formal wear, it is known that the color development can be improved by roughening the fiber surface in order to reduce the amount of light reflected from the surface and improve black color development.

In addition, as a method for roughening the fiber surface, adding particles to a polyester composition has been proposed. For example, Patent Document 1 proposes a polyester composition in which the interparticle distance is 0.2 to 0.7 μm and particles of 50 to 200 μm are present within the surface. Patent Document 2 proposes a polyester fiber containing 0.4 to 5 weight percent silica particles with an average primary particle diameter of 0.02 to 0.1 μm. Patent Document 3 proposes a polyester composition containing 10 ppm to 75 ppm of a phosphorus compound, 1 to 20 ppm of a titanium compound, and 0.5 to 3.0% silica particles with an average secondary particle diameter of 20 to 100 nm.

Japanese Patent Publication No. 55-107512 Japanese Patent Application Publication No. 2011-207928 Japanese Patent Application Publication No. 2013-189521

However, the fibers or compositions described in these documents are amorphous bodies formed by agglomeration of particles, and therefore have problems in that the spinnability, such as the increase in filtration pressure during spinning, cannot keep up with the recent trend toward more sophisticated fibers (thinner fibers), and the color development, particularly black color development, is poor.

Therefore, the present invention provides a polyester composition having excellent spinnability and excellent black coloring properties, and a polyester fiber having excellent black coloring properties.

The object of the present invention is to achieve the above object by any one of the following (1) to (3).
(1) A polyester composition containing 0.5 to 3.0% by weight of silica particles having an average primary particle size of 0.15 to 0.30 μm and a relative standard deviation of particle size of 0.40 or less, and having a methoxy group content of 10 ppm or less.
(2) A polyester fiber made of the polyester composition according to (1) above, which contains 0.5 to 3.0% by weight of silica particles having an average primary particle size of 0.15 to 0.30 μm and a relative standard deviation of particle size of 0.40 or less, and the number of silica particles on the fiber surface, the center-to-center distance between adjacent silica particles being within a range of less than twice the average primary particle size, is 4 or less per ¹⁰ μm2.
(3) The polyester fiber according to (2) above, wherein the coefficient of friction of the running yarn is 0.35 or less in the yarn-to-matte finish and 0.7 or less in the yarn-to-mirror finish.

The polyester composition of the present invention combines good spinnability and black coloring properties, making it possible to provide fibers that are particularly suitable for use in black formal wear.

The present invention will be described in detail below.
The polyester composition of the present invention contains 0.5 to 3.0% by weight of silica particles having an average primary particle size of 0.15 to 0.30 μm and a relative standard deviation of particle size of 0.40 or less, and the methoxy group content of the polyester is 10 ppm or less.

The polyester composition of the present invention is a polyester whose main components are an aromatic dicarboxylic acid and a diol.

The aromatic dicarboxylic acid used in the present invention is preferably at least 95 mol% aromatic dicarboxylic acid, and more preferably terephthalic acid.

In addition, other dicarboxylic acids may be included as copolymerization components within the scope of the invention, so long as the effects of the invention are not impaired. Specific examples include known dicarboxylic acids such as isophthalic acid, isophthalic acid-5-sulfonate, naphthalene 2,6-dicarboxylic acid, bisphenol dicarboxylic acid, adipic acid, succinic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, and 1,12-dodecanedicarboxylic acid.

It is preferable that the diol used in the present invention is linear alkylene glycol, with 80 mol% or more of the diol being linear alkylene glycol. Specific examples of linear alkylene glycol include ethylene glycol, 1,3-propanediol, and 1,4-butanediol. These may be used alone or in combination of two or more types.

In addition, other diols can be used in combination as copolymerization components within the scope of the present invention that does not impair the effects of the present invention. Specific examples include diethylene glycol, hexanediol, cyclohexanedimethanol, diethylene glycol bisphenol A ethylene oxide adduct, and polyethylene glycol.

The polyester composition of the present invention may also contain matting agents such as titanium dioxide, fine particles such as agglomerated alumina, antioxidants such as hindered phenol derivatives, and other coloring pigments.

The polyester composition of the present invention contains silica particles as described above. The silica particles in the present invention are particles mainly composed of silicon oxide.
The silica particles contained in the polyester composition of the present invention have an average primary particle diameter of 0.15 to 0.30 μm. If the average primary particle diameter is greater than 0.30 μm, the surface of the fiber obtained from the polyester composition may be insufficiently roughened, resulting in poor color development. If the average primary particle diameter is less than 0.15 μm, the silica particles may be prone to aggregation, resulting in poor spinnability. If the average primary particle diameter is within the above range, both color development and spinnability can be achieved, and if the average primary particle diameter is 0.15 to 0.20 μm, the color development and spinnability are further improved, which is preferable.

The silica particles contained in the polyester composition of the present invention have the above-mentioned average primary particle size and a relative standard deviation of particle size of not more than 0.40. Here, the relative standard deviation is defined by the following formula:
Relative standard deviation = standard deviation of particle size σ / average primary particle size D (μm)

If the relative standard deviation exceeds 0.40, the number of silica particles that can contribute to color development on the fiber surface will be reduced, resulting in poor color development, and the fiber surface will become too rough, making it difficult to obtain good spinnability. The relative standard deviation is preferably 0.35 or less, and more preferably 0.30 or less.

The average primary particle size and relative standard deviation of silica particles can be determined by exposing the particles by subjecting the surface of the polyester composition to low-temperature plasma ashing treatment to a depth of 0.3 μm using a plasma reactor, and processing images of 5,000 or more particles taken using a scanning electron microscope using an image analyzer.

The polyester composition of the present invention also contains 0.5 to 3.0% by weight of silica particles. If the content of silica particles is less than 0.5% by weight, the surface of the fiber obtained from the polyester composition may be insufficiently roughened, resulting in poor color development. If the content of silica particles exceeds 3.0% by weight, the silica particles may be prone to aggregation, resulting in poor spinnability. If the content of silica particles is within the above range, both color development and spinnability can be achieved, and if the content is 1.0 to 2.0% by weight, the color development and spinnability are better, which is preferable.

The method for producing the silica particles used in the present invention is not particularly limited, but a wet method is preferably used. Silica particles can be obtained by a hydrolysis method using, for example, sodium silicate or alkoxysilane as a starting material. From the viewpoint of dispersibility of silica particles and suppression of generation of coarse particles, silica particles obtained using sodium silicate as a starting material are preferred.

The polyester composition of the present invention can be produced by a conventionally known method, for example, by a direct polymerization method. The polyester composition of the present invention contains a polymer.

The amount of methoxy groups in the polyester composition of the present invention is 10 ppm or less. In order to reduce the amount of methoxy groups in the polyester composition to 10 ppm or less, it is preferable to produce the polyester composition by a direct polymerization method in which aromatic dicarboxylic acids, diols, and other copolymerization components are directly reacted. When the amount of methoxy groups in the polyester composition is 10 ppm or less, the color development is good. The reason why the color development is good when the amount of methoxy groups in the polyester composition is 10 ppm or less is unclear, but it is presumed that this is because there is a tendency for the amount of diethylene glycol (DEG) and carboxyl terminal groups (COOH terminal groups) to increase when there are fewer methoxy groups, which allows the dye to be seated.

In the method for producing polyester fibers from the polyester composition of the present invention, the polyester composition is pre-dried in hot air or under reduced pressure as necessary, and then fed to a spinning machine and spun from a spinneret. In order to prevent deterioration of the polyester composition due to heat, the residence time of the polyester composition in the spinning machine is preferably as short as possible, and is usually within 20 minutes. The spinning temperature may be 250 to 300°C.

The spun yarn is cooled and solidified with cold air, then an oil agent is applied, and the yarn is taken up by a take-up roll that controls the spinning speed. The undrawn yarn taken up by the take-up roll is usually drawn continuously, but it may also be drawn in a separate process after being wound up. The spinning speed may be about 300 to 3000 m/min, preferably 500 to 2500 m/min. The obtained yarn is false-twisted while applying heat as necessary to obtain a polyester textured yarn, which can then be used to produce a knitted fabric using a circular knitting machine.

In the polyester fiber of the present invention, the number of silica particles on the fiber surface in which the center-to-center distance between adjacent silica particles is less than twice the average primary particle size is 4 or less per 10 μm ^2. When the number of silica particles on the fiber surface in which the center-to-center distance between adjacent silica particles is less than twice the average primary particle size is 4 or less per 10 μm ² , spinning operability and black coloring are improved.

In order to make the number of silica particles on the fiber surface with a center-to-center distance less than twice the average primary particle size 4 or less per 10 ^μm2 , for example, the following method can be used. First, the silica particles are diluted with a diol, which is a constituent component of the polyester, to 5% by weight or less to form a slurry. Then, between the end of the esterification reaction and the start of the polycondensation reaction, a diol component is added so that the molar ratio of aromatic dicarboxylic acid to diol in the polyester composition after the addition of the silica particles is 2.2 or more, and then the slurried silica particles are added.

The polyester fiber of the present invention also contains 0.5 to 3.0% by weight of silica particles having an average primary particle size of 0.15 to 0.30 μm and a relative standard deviation of particle size of 0.40 or less. When the average primary particle size is in the above range, the fiber surface is sufficiently roughened, improving color development and providing excellent spinnability. The average primary particle size is preferably 0.15 to 0.20 μm.

The polyester fiber of the present invention is preferable if the coefficient of friction of the running yarn is 0.35 or less for the yarn-to-pear finish and 0.7 or less for the yarn-to-mirror finish, since this reduces guide wear when constructing the yarn path.

In addition, the fibers made of the polyester composition of the present invention can be subjected to a weight reduction treatment by a known method. Examples of the weight reduction treatment method include plasma treatment, laser treatment, and alkali weight reduction treatment. From the viewpoint of the texture and dyeability of the resulting fiber, alkali weight reduction treatment is preferred.

The present invention will be described in more detail below with reference to examples. The physical properties in the examples were measured by the following methods.

(1) Average primary particle size, standard deviation, and relative standard deviation The surface of the polyester composition was subjected to plasma low-temperature ashing treatment to a depth of 0.3 μm to expose the particles using a plasma reactor PR300 manufactured by Yamato Scientific Co., Ltd. Images of 5,000 or more particles taken with a scanning electron microscope (SEM, Regulus 8100 type scanning electron microscope: manufactured by Hitachi, Ltd.) were processed with an image analyzer (Image-Pro: manufactured by Nippon Roper Co., Ltd.) to determine the number volume average particle size (average primary particle size), standard deviation, and relative standard deviation.
In the case of polyester fibers, after removing the oil, the fiber surface was subjected to low-temperature plasma ashing treatment in the same manner as for the polyester composition to expose the particles, and the particles were then treated with a scanning microscope and image analyzer in the same manner as for the polyester composition.

(2) Silica particle content (wt%) in polyester composition
6 g of the polyester composition was melted and molded into a plate, and its strength was measured by fluorescent X-ray analysis using an X-ray fluorescence analyzer (PRIMUS II, manufactured by Rigaku Corporation). The metal content was determined as the silica particle content using a calibration curve previously prepared using samples with known contents.
In the case of polyester fibers, after removing the oil, the measurement was carried out by fluorescent X-ray analysis in the same manner as in the case of the polyester composition.

(3) Amount of Methoxy Groups in Polyester Composition 10 ml of hydrazine was added to 20 g of polyester and subjected to alkaline decomposition at 100° C. for 40 minutes. The amount of methanol was determined by gas chromatography, and the amount was expressed as equivalents/10 ⁶ g of polyester.
In the case of polyester fibers, after removing the oil, the fibers were decomposed with an alkali in the same manner as in the case of the polyester composition, and the content of the oil was measured by gas chromatography.

(4) Friction coefficient The friction coefficient of the running yarn was measured with a μMETER manufactured by INTEC and calculated from the tension. The targets were 0.35 or less for the yarn-to-pear finish and 0.70 or less for the yarn-to-mirror finish, and the yarn was evaluated in three stages: A: both the pear finish and the mirror finish were below the target value, so it passed; B: either the pear finish or the mirror finish was below the target value, so it passed; C: both the pear finish and the mirror finish exceeded the target value, so it failed.

(5) Spinning operability Based on the number of times that yarn breakage occurred during spinning, the operation was evaluated on a four-level scale: A: Excellent (less than 1 time/t), B: Excellent (1 time/t or more and less than 2 times/t), C: Good (2 times/t or more and less than 3 times/t), and D: Poor (3 times/t or more).

(6) Black coloring The polyester fibers of the Examples and Comparative Examples were tubularly knitted and treated so that the alkali weight loss rate was 20%. The knitted fabric was dyed with a 15% owf aqueous dispersion of Dianix Black BG-FS (a disperse dye manufactured by Mitsubishi Chemical Corporation) as the dye, in a bath ratio of 1:30 at 130°C for 60 minutes. The L value was measured three times with a colorimeter (CM-3700D manufactured by Minolta Co., Ltd.) to calculate the average value, and the L value was evaluated in four stages: A: 12.0 or less, B: more than 12.0 and 13.0 or less, C: more than 13.0 and 14.0 or less, and D: more than 14.0.

Example 1
A slurry (calculated molar ratio 1.15) consisting of 300 parts by weight of terephthalic acid and 129 parts by weight of ethylene glycol was continuously supplied to an esterification reaction tank equipped with a distillation tower over a period of 3 hours while maintaining the temperature of the reaction tank at 240 to 245° C., and the reaction was carried out while distilling off water from the upper part of the distillation tower. The amount of water distilled off was 64 parts by weight, and the calculated esterification reaction rate of terephthalic acid was 98%.
Of the resulting reaction mixture, 43% (volume) was transferred to a polymerization reaction tank while being filtered through a 10 micron filter.

After that, 22 parts by weight of ethylene glycol was added to the composition transferred to the polymerization reaction tank, followed immediately by the addition of 0.044 parts by weight of antimony trioxide and 0.16 parts by weight of magnesium acetate. The temperature of the composition was raised to 250°C over about 10 minutes. Then, 22 parts by weight of ethylene glycol was added, followed immediately by the addition of 0.060 parts by weight of trimethyl phosphate. The temperature of the composition was raised to 250°C again over about 10 minutes, after which 22 parts by weight of ethylene glycol was added, and the temperature of the composition was raised to 250°C again over about 10 minutes. After that, a silica slurry (silica particle concentration 5% by weight) consisting of 7.5 parts by weight of silica particles with an average primary particle size of 0.17 μm and a relative standard deviation of particle size of 0.30 and 142 parts by weight of ethylene glycol was divided into three equal parts (volume) and added in three separate portions. In each addition, if the temperature in the system was 225°C or lower, the addition was interrupted, and the system was left on standby until the temperature in the system exceeded 225°C. After each addition, the system was left to stand by until the temperature reached 245° C. or higher (the molar ratio of aromatic dicarboxylic acid to diol was 3.0).

After the addition of the silica slurry was completed, the polymerization reaction tank was heated to 290°C over 90 minutes and simultaneously reduced in pressure to 60 Pa over 60 minutes, and the polycondensation reaction was carried out until the intrinsic viscosity of the polyester composition, previously determined from the stirring load power, reached 0.66.
This polyester composition was dried at 160° C. for 7 hours, spun at a spinning temperature of 290° C. and a spinning speed of 1500 m/min, and then stretched at a draw ratio of 2.81.

The obtained polyester fiber had a methoxy group content of 5 ppm, a silica particle content of 1.5 wt%, an average primary particle size of 0.17 μm, a relative standard deviation of the particle size of 0.30, and the number of silica particles having a center-to-center distance less than twice the average primary particle size was 0 per ¹⁰ μm2. The spinning operability, yarn friction coefficient, and black coloring of the fiber were extremely good.

Example 2
A polyester fiber was obtained in the same manner as in Example 1, except that the average primary particle size of the silica particles was 0.15 μm. The spinning operability, yarn friction coefficient, and black coloring were extremely good.

Example 3
A polyester fiber was obtained in the same manner as in Example 1, except that the average primary particle size of the silica particles was 0.20 μm. The spinning operability, yarn friction coefficient, and black coloring were extremely good.

Example 4
A polyester fiber was obtained in the same manner as in Example 1, except that the average primary particle size of the silica particles was 0.30 μm. The spinning operability and the yarn friction coefficient were extremely good. The black coloring was at a usable level.

Example 5
A polyester fiber was obtained in the same manner as in Example 1, except that the relative standard deviation of the particle size of the silica particles was 0.40. The spinning operability, the yarn friction coefficient, and the black coloring property were extremely good.

Example 6
Except for changing the content of silica particles in the polyester fiber to 1.0% by weight, a polyester fiber was obtained in the same manner as in Example 1. The spinning operability, yarn friction coefficient, and black coloring were extremely good.

(Example 7)
Except for changing the content of silica particles in the polyester fiber to 2.0% by weight, a polyester fiber was obtained in the same manner as in Example 1. The spinning operability, yarn friction coefficient, and black coloring were extremely good.

(Example 8)
A polyester fiber was obtained in the same manner as in Example 1, except that the content of silica particles in the polyester fiber was 0.5% by weight. The spinning operability and black coloring were very good. The yarn-mirror surface friction coefficient was at a usable level.

(Example 9)
A polyester fiber was obtained in the same manner as in Example 1, except that the content of silica particles in the polyester fiber was 3.0% by weight. The black coloring was very good. The spinning operability and the yarn-mirror friction coefficient were at a usable level.

(Example 10)
After the ester exchange reaction of dimethyl terephthalate and ethylene glycol, the same silica particles as in Example 1 were added, and a polycondensation reaction was carried out in the same manner as in Example 1 to produce a polyester composition (B) (methoxy group content: 20 ppm).
To the polyester composition (60 parts by weight) produced in Example 1, 30 parts by weight of the polyester composition (B) was added, and the mixture was spun and drawn in the same manner as in Example 1 to obtain a polyester fiber having a methoxy group content of 10 ppm. The spinning operability, yarn friction coefficient, and black coloring were extremely good.

Example 11
Polyester fibers were obtained in the same manner as in Example 1, except that the molar ratio of ethylene glycol to terephthalic acid when the silica particles were added was 2.2.
The number of silica particles in the obtained polyester fiber, in which the center-to-center distance was less than twice the average primary particle size, was 4 per ¹⁰ μm2. The spinning operability was also excellent. The yarn-matte friction coefficient and black coloring were at usable levels.

The results of Examples 1 to 11 are summarized in Table 1.

(Comparative Example 1)
Except for the fact that the average primary particle size of the silica particles was 0.12 μm, polyester fibers were obtained in the same manner as in Example 1. A large number of aggregates of the silica particles in the obtained polyester fibers were confirmed, and the dispersibility was poor, resulting in poor spinning operability.

(Comparative Example 2)
Except for the fact that the average primary particle size of the silica particles was 0.33 μm, polyester fibers were obtained in the same manner as in Example 1. The obtained polyester fibers had poor black coloring properties.

(Comparative Example 3)
A polyester fiber was obtained in the same manner as in Example 1, except that the silica particles had a relative standard deviation of particle size of 0.44. The spinning operability and black color development of the obtained polyester fiber were poor.

(Comparative Example 4)
A polyester fiber was obtained in the same manner as in Example 1, except that the content of the silica particles in the polyester fiber was 0.3% by weight. The obtained polyester fiber had poor black coloring properties.

(Comparative Example 5)
A polyester fiber was obtained in the same manner as in Example 1, except that the content of the silica particles in the polyester fiber was 3.3% by weight. The obtained polyester fiber had poor spinning operability.

(Comparative Example 6)
350 parts by weight of dimethyl terephthalate and 223 parts by weight of ethylene glycol were charged into an ester exchange reaction tank equipped with a rectification column and dissolved at 140° C., after which 0.044 parts by weight of antimony trioxide and 0.16 parts by weight of magnesium acetate were added, and the temperature of the reaction tank was raised from 140° C. to 230° C. over three hours. An ester exchange reaction was carried out while distilling off the generated methanol, and then 0.060 parts by weight of trimethyl phosphate was added.
23 parts by weight of ethylene glycol was added to the composition transferred to the polymerization reaction tank (molar ratio 2.2), and a silica slurry (silica particle concentration 5% by weight) consisting of 5.3 parts by weight of silica particles having an average primary particle size of 0.17 μm and a relative standard deviation of particle size of 0.30 and 142 parts by weight of ethylene glycol was divided into three equal parts (by volume) and added in three separate portions.
After the addition of the silica slurry was completed, the polymerization reaction tank was heated to 290°C over 90 minutes and simultaneously reduced in pressure to 60 Pa over 60 minutes, and the polycondensation reaction was carried out until the intrinsic viscosity of the polyester composition, previously determined from the stirring load power, reached 0.66.
The resulting polyester composition was spun and stretched in the same manner as in Example 1.
The amount of methoxy groups in the obtained polyester fiber was 12 ppm, and the black coloring property was poor.

(Comparative Example 7)
Polyester fibers were obtained in the same manner as in Example 1, except that the concentration of the silica particles to be added was 7% by weight and 66 parts by weight of the diol was distilled off before the addition of the silica particles (the molar ratio of the aromatic dicarboxylic acid to the diol after the addition of the silica particles was 2.0).
The number of silica particles on the surface of the obtained polyester fiber in which the center-to-center distance was less than twice the average primary particle size was 10 per 10 μm ² , and both the spinning operability and black coloring were poor.

The results of Comparative Examples 1 to 7 are summarized in Table 2.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2019-157115) filed on August 29, 2019, the entirety of which is incorporated by reference.

Claims (2)

A polyester fiber made of a polyester composition containing 0.5 to 3.0% by weight of silica particles having an average primary particle size of 0.15 to 0.30 μm and a relative standard deviation of particle size of 0.40 or less, and having a methoxy group of the polyester of 10 ppm or less ,
A polyester fiber containing 0.5 to 3.0% by weight of silica particles having an average primary particle size of 0.15 to 0.30 μm and a relative standard deviation of particle size of 0.40 or less, and having 4 or less silica particles ^per 10 μm2, the center-to-center distance between adjacent silica particles being within a range of less than twice the average primary particle size on the fiber surface.
The method for measuring the average primary particle size and the relative standard deviation of the particle size of the silica particles is as follows.
Using a plasma reactor, the surface of the polyester fiber from which the oil agent has been removed is subjected to low-temperature plasma ashing treatment to a depth of 0.3 μm to expose the particles, and images of 5,000 or more particles taken with a scanning electron microscope are processed with an image analyzer to determine the number volume average particle size (average primary particle size), standard deviation, and relative standard deviation defined by the following formula.
Relative standard deviation = standard deviation of particle size / average primary particle size (μm) 2. The polyester fiber according to claim 1 , wherein the coefficient of friction of a running yarn is 0.35 or less in a yarn-matte finish and 0.7 or less in a yarn-mirror finish.