JP2023026195A - Polyester-based splittable composite fiber, woven/knitted fabric and method for manufacturing woven/knitted fabric - Google Patents

Abstract

To provide a polyester-based splittable composite fiber that is a splittable composite fiber at least partially using a recycled polyester resin containing a recycled polyester raw material at a high ratio which has a mechanical characteristic value equivalent to the case using only a virgin polyester resin.SOLUTION: A polyester-based splittable composite fiber is a composite fiber that has a polyester resin A of a hardly alkali-soluble polyester component and a polyester resin B of an easily alkali-soluble component, in which the polyester resin A is divided into a plurality of pieces by the polyester resin B in a cross-sectional shape of the fiber, wherein the polyester resin A is a recycled polyester resin containing 80 mass% or more of a component derived from a recycled polyester raw material, and in the recycled polyester resin, when the total amount of the total glycol component is 100 mol%, a content of diethylene glycol is 4 mol% or less, and carboxyl terminal group concentration is 40 eq./t or less.SELECTED DRAWING: Figure 1

Description

The present invention is a composite fiber partially using a recycled polyester resin containing a component derived from a recycled polyester raw material including unused polyester generated in the process of manufacturing used polyester products and polyester products, which is easily alkalized. The present invention relates to a polyester-based splittable conjugate fiber in which an alkali-hardly soluble component is split into a plurality of pieces by an elutable component. Furthermore, the present invention relates to a woven or knitted fabric containing fibers made of the recycled polyester resin.

Polyethylene terephthalate (hereinafter sometimes abbreviated as PET) has a high melting point, chemical resistance, and is relatively inexpensive, so it is widely used for molded articles such as fibers, films, and PET bottles.
These polyester products inevitably generate scraps during the manufacturing and processing stages, and are often disposed of after use. is short. On the other hand, if it is not incinerated, it will remain semi-permanently because it will not rot and decompose.
In recent years, plastic containers discarded as garbage have flowed into the ocean via rivers, and microplastics that have been finely crushed by the action of waves and tidal currents accumulate in the bodies of marine organisms and accumulate in the food chain, contributing to the ecology of marine organisms. The fact that plastics have an adverse effect on systems and that plastics are a major cause of marine pollution have been viewed as problems, and there is a worldwide movement to reduce the amount of plastics used and switch to biodegradable plastics.

From the viewpoint of reducing the amount of such plastic products used and from the viewpoint of environmental problems, various recycling methods for reusing resources have been carried out. As for polyester products, a method of recycling polyester waste generated in the manufacturing process and a method of recovering and reusing as a raw material a product that has been discarded once on the market is being studied.
Especially in recent years, with regard to textile products, eco-marked products that are certified by achieving a certain recycling rate have become widespread.

Various methods have been proposed for recycling recycled polyester raw materials. For example, a method of adding methanol to PET waste to decompose it into dimethylene terephthalate (hereinafter sometimes referred to as "DMT") and ethylene glycol (hereinafter sometimes referred to as "EG") (Patent Document 1 ), a method in which EG is added to PET waste to depolymerize it, and then methanol is added to recover DMT (Patent Document 2); A method (Patent Document 3) and the like have been proposed.

In addition, problems that arise when recycling PET bottles that have once been made into products include additives added to the polyester resin, and caps (aluminum, polypropylene, polyethylene) and inner plugs attached to the bottle body. and liners (polypropylene, polyethylene), labels (paper, polystyrene and other resins, inks), adhesives, printing inks, etc.
As a pretreatment for the recycling process, first, collected PET bottles are passed through a vibrating sieve to remove sand, metals, and the like. After that, the PET bottles are washed, the colored bottles are separated, and then coarsely pulverized. Labels and the like are then removed by air separation. Further, the pieces of PET bottles are finely pulverized, except for the pieces of aluminum derived from the cap and the like. Components such as adhesives, proteins and molds are removed by high-temperature alkaline washing, and different components such as polypropylene and polyethylene are separated by specific gravity.

However, even through these steps, it was particularly difficult to completely separate non-polyester resins such as polypropylene, polyethylene and polystyrene as described above. Therefore, even if the recycled polyester resin is obtained by the recycling method described in Patent Documents 1 to 3 as described above, the foreign matter derived from the non-polyester resin cannot be sufficiently removed, and the amount of foreign matter mixed in cannot be sufficiently reduced. However, it was not possible to obtain a product having the same quality as the virgin polyester resin. Moreover, the methods of Patent Documents 1 to 3 require a large amount of cost for installation, operation, maintenance, etc. of the recovery apparatus, and there is room for improvement in terms of practicality.

Further, the invention described in Patent Document 4 describes a method in which polyester waste is depolymerized with ethylene glycol, filtered through a filter having an average mesh size of 10 to 50 μm, and then subjected to a repolymerization reaction. It is also shown that the resulting recycled polyester resin has a small amount of foreign matter mixed in and is excellent in workability during processing. However, even in this method, the above-described non-polyester resin-derived foreign matter cannot be sufficiently removed, and the amount of foreign matter mixed in cannot be sufficiently reduced.
In this way, not only various inorganic substances but also foreign substances derived from non-polyester resins can be sufficiently removed, and various products can be obtained in the same manner as virgin polyester resins, and high-quality products can be obtained. A recycled polyester resin that can be used has not yet been obtained.

In particular, when a polyester resin is melt-spun to obtain a fiber, the amount of contaminants mixed therein and thermal stability greatly affect productivity. The more complicated the cross-sectional shape of the fiber and the finer the fineness, the greater the influence of these factors, which causes problems such as difficulty in production and deterioration in mechanical properties of the resulting fiber.

Furthermore, due to the growing awareness of environmental issues, there is a growing demand for recycled polyester resins that use a high percentage of recycled raw materials. Recycled polyester resins with a recycled raw material usage rate of 80% or more, and further with a recycled raw material usage rate of 100%, have a remarkable problem of contamination with foreign matter as described above, and are also inferior in thermal stability. As a matter of course, it has been more difficult to obtain a splittable conjugate fiber having a complicated cross-sectional shape by melt spinning.

Japanese Patent Publication No. 42-8855 JP-A-48-62732 JP-A-60-248646 JP 2005-171138 A

The present invention solves the above problems, a) used polyester products and b) non-employed polyester resin generated in the process of manufacturing polyester products, at least one component derived from recycled polyester raw materials is reduced to 80% by mass. A polyester-based splittable conjugate fiber at least partially using a recycled polyester resin containing the above, which has mechanical properties equivalent to those obtained when only a virgin polyester resin is used, and which can be obtained with high productivity. It is intended to provide a composite fiber.

The present inventors arrived at the present invention as a result of intensive studies in order to solve the above problems.
That is, the gist of the present invention is the following (1) to (3).
(1) Composite fiber having a polyester resin A as a poorly soluble alkali component and a polyester resin B as a readily alkaline soluble component, wherein the polyester resin A is divided into a plurality of pieces by the polyester resin B in the cross-sectional shape of the fiber. wherein the polyester resin A contains 80% by mass or more of a component derived from at least one recycled polyester raw material of a) used polyester products and b) unadopted polyester resins generated in the process of manufacturing polyester products. The recycled polyester resin (polyester resin A) has a diethylene glycol content of 4 mol% or less when the total amount of all glycol components is 100 mol%, and a carboxyl terminal group concentration of is 40 equivalents/t or less.
(2) Recycled polyester resin containing 80% by mass or more of a component derived from at least one recycled polyester raw material of a) used polyester products and b) unadopted polyester resin generated in the process of manufacturing polyester products ( A woven or knitted fabric containing fibers made of a polyester resin A), wherein the polyester resin A has a diethylene glycol content of 4 mol% or less when the total amount of all glycol components is 100 mol%, and a carboxyl terminal A woven or knitted fabric, characterized in that the base concentration is 40 equivalent/t or less, and the single filament fineness of the fibers made of the polyester resin A is 1.0 dtex or less.
(3) A method for producing a woven or knitted fabric according to (2), comprising a step of weaving or knitting the polyester splittable conjugate fiber according to (1) to obtain a gray fabric, and subjecting the gray fabric to an alkali weight reduction treatment. and a step of splitting the portion of the polyester resin A by eluting the polyester resin B.

In the polyester-based splittable conjugate fiber of the present invention (hereinafter sometimes referred to as the conjugate fiber of the present invention), the recycled polyester resin used as the polyester resin A, which is the hardly soluble alkali component, has a small amount of foreign matter mixed in and has a carboxyl terminal Since the base concentration and diethylene glycol content satisfy specific ranges, in the process of obtaining fibers by melt spinning, long-term continuous operation is possible even with complex cross-sectional shapes, and products can be obtained with high productivity. be able to. Furthermore, the composite fiber of the present invention has mechanical properties equivalent to those using virgin polyester resin, and can be suitably used in various fields and applications such as various clothing and industrial fields.
Since the woven or knitted fabric of the present invention contains fine fineness fibers made of the recycled polyester resin, it has mechanical properties equivalent to those using virgin polyester resin, and is excellent in flexibility and denseness. It becomes a thing.

1 is a schematic diagram showing one embodiment of a cross section of the composite fiber (single fiber) of the present invention. FIG.

The present invention will be described in detail below.
The conjugate fiber of the present invention contains polyester resin A, which is a poorly soluble alkali component, and polyester resin B, which is a highly alkaline soluble component.

The polyester resin A, which is a hardly alkali-soluble component of the present invention, contains 80% of at least one component derived from a recycled polyester raw material of a) used polyester products and b) unadopted polyester generated in the process of manufacturing polyester products. It is a recycled polyester resin containing more than mass %.
Examples of the used polyester products of a) above include, for example, polyester molded articles (including fibers) that have been put on the market once and collected after use. Typical examples include containers or packaging materials such as PET bottles.
Unused polyester generated in the process of manufacturing polyester products in b) above is polyester that has not been commercialized. , waste generated during molding, processing, etc.;
The above a) and b) are not limited in their form, etc., and may be pelletized by further processing such as pulverization and cutting as necessary, or may be melted and pelletized. good.
In addition, the recycled polyester raw materials of a) and b) may be either crystalline or amorphous. Therefore, for example, pellets of amorphous polyester waste not subjected to heat treatment, crystalline pellets subjected to heat treatment, mixtures of crystalline pellets and amorphous pellets, and the like can be used. In the present invention, it is preferable to use a crystalline recycled polyester raw material for the purpose of preventing fusion between pellets, particularly during charging into a can or depolymerization reaction. Therefore, it is possible to preferably use a material obtained by crystallizing the above material a) or b) by heat treatment (crystallized pellets, etc.).

In addition, the properties of the recycled polyester raw materials of a) and b) are not limited, and may be in the form of a) and b), or cut pieces obtained by further processing such as cutting and crushing. , pulverized products (powder) and the like, as well as solid forms such as compacts (such as pellets) formed by molding these. More specific examples include pellets obtained by cooling and cutting melted polyester scraps, cut pieces obtained by finely cutting polyester molded articles such as PET bottles, and the like. In addition, it may be in the form of a liquid obtained by dispersing or dissolving the above cut pieces, pulverized material (powder), etc. in a solvent. When these raw materials are used to produce polyester products, they can be melted at a temperature higher than their melting point and put into a can as a melt, if necessary.

The recycled polyester resin in the present invention is a recycled polyester resin having a high usage rate of recycled polyester raw materials. The recycled polyester resin in the present invention contains 80 mass % or more of the component derived from the recycled polyester raw material, which is at least one of the above a) and b), preferably 85 mass % or more. The recycled polyester resin in the present invention can be obtained by the production method of the present invention, which will be described later, but it is also possible to easily obtain a recycled polyester resin that is 100% derived from recycled polyester raw materials, that is, made only from recycled raw materials. is possible.

The recycled polyester resin in the present invention has the following characteristic values (a) and (b), and preferably has the characteristic value (c).
(a) When the total amount of all glycol components is 100 mol%, the content of diethylene glycol is 4 mol% or less (b) The carboxyl terminal group concentration is 40 equivalents/t or less (c) Average pressure rise measured by a pressure tester Velocity of 0.6 MPa/h or less A recycled polyester resin having these characteristic values can be obtained by a method for producing a recycled polyester resin, which will be described later.

First, as the characteristic value of (a), the recycled polyester resin in the present invention has a diethylene glycol content of 4 mol% or less, especially 3.5 mol% or less, when the total amount of all glycol components is 100 mol%. is preferably In particular, in the recycled polyester resin obtained by the production method of the present invention, ethylene glycol is used as one of raw materials, and diethylene glycol may be generated as a by-product at that time. Recycled polyester resin has a small amount of diethylene glycol as a by-product, and by setting the content of diethylene glycol to 4 mol% or less, the amorphous part is reduced, and it has excellent performance in thermal stability. there is For this reason, melt spinning can be performed with good workability equivalent to virgin polyester, and a complex cross-sectional shape in which polyester resin A is divided into a plurality of pieces by polyester resin B as shown in FIG. 1 described later can be produced. can be obtained. In addition, it is possible to obtain a conjugate fiber excellent in mechanical properties such as strength and elongation.
The lower limit of the diethylene glycol content can be, for example, about 0.5 mol %, but is not limited to this.

In the recycled polyester resin in the present invention, when the total amount of all glycol components constituting the polyester is 100 mol%, ethylene glycol is preferably 80 mol% or more of the total glycol components, especially 85 mol% or more. Preferably. If the ethylene glycol content is less than 80 mol %, the obtained polyester resin tends to be inferior in crystallinity and heat resistance.
Further, in the recycled polyester resin of the present invention, terephthalic acid preferably accounts for 80 mol % or more when the total amount of all acid components constituting the polyester is 100 mol %. That is, terephthalic acid is the main component as the acid component. The proportion of terephthalic acid in the acid component is 80 mol % or more, and the proportion of terephthalic acid is preferably 90 mol %. If the proportion of terephthalic acid is less than 80 mol %, the crystallinity of the resin composition tends to be lowered and the resin composition tends to become amorphous, which is not preferable.

Examples of diol components other than ethylene glycol and diethylene glycol among all the glycol components in the recycled polyester resin include cyclohexanedimethanol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6 -Hexanediol, dimer diol, ethylene oxide adduct of bisphenol S, ethylene oxide adduct of bisphenol A, and the like can be used.

Acid components other than terephthalic acid in the recycled polyester resin include isophthalic acid, phthalic acid, 5-sodium sulfoisophthalic acid, phthalic anhydride, naphthalenedicarboxylic acid, adipic acid, sebacic acid, dimer acid, and the like. Two or more types may be used in combination, and ester-forming derivatives of these acids may also be used.

The resin of the present invention is not particularly limited in kind, but among them, it is preferable to use polyethylene terephthalate (PET) as a main component.
In particular, in the method for producing a recycled polyester resin described later, PET, which is a polycondensate of ethylene glycol and terephthalic acid, can usually be obtained, but the recycled polyester raw material contains components other than ethylene glycol and terephthalic acid. In some cases, a polyester resin obtained by copolymerizing these components may be produced by a polycondensation reaction. For this reason, the recycled polyester resin may be copolymerized with the above-mentioned components as an acid component or a glycol component, in addition to PET, which is the main component. Two or more of these components may be contained.

The recycled polyester resin in the present invention has a carboxyl terminal group concentration of 40 equivalents/t or less, preferably 30 equivalents/t or less, and more preferably 25 equivalents/t or less, as the characteristic value of (b). is preferred.
The recycled polyester resin in the present invention has a carboxyl terminal group concentration of 40 equivalents / t or less, so that it has excellent performance in thermal stability. can be done. Therefore, it is possible to obtain a conjugate fiber having a complicated cross-sectional shape in which the polyester resin A is divided into a plurality of pieces by the polyester resin B as shown in FIG. 1 which will be described later. In addition, it is possible to obtain a conjugate fiber excellent in mechanical properties such as strength and elongation. The lower limit of the carboxyl terminal group concentration can be, for example, about 5 equivalents/t, but is not limited to this.

When the content of diethylene glycol in the polyester resin A of the present invention exceeds 4 mol%, or when the carboxyl terminal group concentration exceeds 40 equivalents/t, the crystallinity and thermal stability of the polyester resin A deteriorate. Therefore, it is not possible to obtain a conjugate fiber having a complicated cross-sectional shape in which the polyester resin A is divided into a plurality of pieces by the polyester resin B by melt spinning with good workability. That is, the polyester resin A cannot have a cross-sectional shape with uniform individual shapes and sizes as shown in FIG. For this reason, fibers made of the polyester resin A obtained by subjecting the polyester resin B to alkali weight reduction treatment from such composite fibers have variations in shape and size.

Although the limiting viscosity of the recycled polyester resin in the present invention is not particularly limited, it is usually preferably about 0.44 to 0.80. In addition, the intrinsic viscosity (IV) is measured at a temperature of 20° C. using an equal mass mixture of phenol and ethane tetrachloride as a solvent.

As the characteristic value (c) of the recycled polyester resin in the present invention, the average pressurization rate measured by the following method is preferably 0.6 MPa / h or less, preferably 0.5 MPa / h or less, Among them, it is preferably 0.4 MPa/h or less. The average pressurization rate in the present invention is an index of the amount of foreign substances derived from various inorganic substances and foreign substances derived from non-polyester resins. is shown. The lower limit of the average pressure increase rate can be set to, for example, about 0.01 MPa/h, but is not limited to this.

The method for measuring the average pressurization rate uses a pressurization tester including an extruder and a pressure sensor, and a stainless steel filter (nominal size mesh: 1400 mesh, weave: twill weave, vertical mesh: 165 mesh) at the tip of the extruder , horizontal mesh: 1400 mesh, vertical wire diameter: 0.07 mm, horizontal wire diameter: 0.04 mm, filtration particle size: 12 μm), the polyester resin is melted at 300 ° C. in an extruder, and the discharge amount from the filter As the pressure value applied to the filter when the melt is extruded at 29.0 g / min, the pressure value at the start of extrusion is defined as the “initial pressure value (MPa)”, and the pressure value at the time of continuous extrusion for 12 hours. When the pressure value is the "final pressure value (MPa)", the average pressure increase rate is calculated by the following formula A based on those pressure values.
Average pressure increase rate (MPa/h) = (final pressure value - initial pressure value) / 12) ... A)

By adopting the production method described later, the recycled polyester resin in the present invention can reduce the amount of foreign substances derived from various inorganic substances and foreign substances derived from non-polyester resins. It is possible to reduce the average pressure increase rate measured by a pressure increase tester to 0.6 MPa/h or less. Therefore, the number of times of yarn breakage during melt spinning can be reduced, and melt spinning can be performed in the same manner as when using virgin polyester resin, producing fibers with excellent mechanical properties such as strength and elongation. It is also possible to The lower limit of the average pressure increase rate can be set to, for example, about 0.01 MPa/h, but is not limited to this.

As the extruder, filter and the like used in the above measurements, known or commercially available ones can be used as appropriate as long as they satisfy the stipulations of the present invention.

In the present invention, if necessary, a reinforcing material may be added to the filter as long as it does not substantially affect the measurement results. In the above measurement method, extremely high pressure is applied to the filter, so the filter alone may be deformed or damaged. In such cases, it is preferable to support the filter with stiffeners. A mesh-like metal member or the like can be used as the reinforcing material. More specifically, a metal filter having a strength that prevents deformation of the filter and having a coarse mesh that does not substantially affect the measurement results can be suitably used as the reinforcing material. Then, such a reinforcing material can be used by laminating it on the downstream side of the filter.

The recycled polyester resin in the present invention may contain a polycondensation catalyst and various additives added depending on the application.
First, as the polycondensation catalyst, at least one of germanium compounds, antimony compounds, titanium compounds, cobalt compounds, zinc compounds, tin compounds and the like can be used, although not limited thereto. Among them, it is particularly preferable to use at least one of a germanium compound and an antimony compound. When the transparency of the resulting recycled polyester resin is important, it is preferable to use a germanium compound. As the above compounds, oxides such as germanium, antimony, titanium and cobalt, inorganic acid salts, organic acid salts, halides and sulfides can be used.

The amount of the polycondensation catalyst used is not particularly limited, but for example, it is preferably 5×10 ⁻⁵ mol/unit or more per 1 mol of the acid component of the polyester resin to be produced, and among them, 6×10 ⁻⁵ mol/unit. It is more preferable to set it to unit or more. The upper limit of the amount used can be, for example, about 1×10 ⁻³ mol/unit, but is not limited to this.

The polycondensation catalyst contained in the recycled polyester raw material may also act as a catalyst during the polycondensation reaction, so when adding the polycondensation catalyst in the polycondensation process, the polycondensation catalyst contained in the recycled polyester raw material It is preferable to consider the type of catalyst and its content.

Various additives added depending on the application include fatty acid esters that can adjust the melt viscosity, hindered phenolic antioxidants, phosphorus compounds that can suppress thermal decomposition of the resin, and improve the appearance of the resin. and a titanium compound that improves the whiteness of the resin, a crystal nucleating agent that improves the crystallinity of the resin, and the like.

Examples of fatty acid esters include beeswax (a mixture containing myricyl palmitate as a main component), stearyl stearate, behenyl behenate, stearyl behenate, glycerin monopalmitate, glycerin monostearate, glycerin distearate, glycerin tri Stearate, pentaerythritol monopalmitate, pentaerythritol monostearate, pentaerythritol distearate, pentaerythritol tristearate, pentaerythritol tetrastearate, dipentaerythritol hexastearate and the like. Among these, glycerin monostearate, pentaerythritol tetrastearate, and dipentaerythritol hexastearate are preferred. These can be used alone or in combination of two or more.

Examples of hindered phenol antioxidants include 2,6-di-t-butyl-4-methylphenol, n-octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl ) propionate, tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, 4 , 4′-butylidenebis-(3-methyl-6-t-butylphenol), triethylene glycol-bis[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate], 3,9-bis {2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1′-dimethylethyl}-2,4,8,10-tetraoxaspiro[5,5 ] undecane and the like are used, but tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane is preferred from the viewpoint of effect and cost. These can be used alone or in combination of two or more.

Phosphorus compounds such as phosphorous acid, phosphoric acid, trimethyl phosphite, triphenyl phosphite, tridecyl phosphite, trimethyl phosphate, triethyl phosphate, tridecyl phosphate, and triphenyl phosphate are used as the phosphorus compound. be able to. These can be used alone or in combination of two or more.

Examples of color tone modifiers include cobalt compounds such as cobalt acetate, manganese compounds such as manganese acetate, dyes (blue, purple, and red), and copper phthalocyanine compounds. Among them, cobalt acetate and dyes are preferable from the viewpoint of polycondensation catalytic activity, physical properties of the resulting polyester resin, and cost.

In addition, it is preferable to contain a blue dye and/or a red dye or a purple dye because the color tone becomes good.

Specific examples of dyes in COLOR INDEX GENERIC NAME include blue dyes such as SOLVENT BLUE 104, SOLVENT BLUE 122, and SOLVENT BLUE 45, SOLVENT RED 111, SOLVENT RED 179, SOLVENT RED 195, SOLVENT RED 135, and PIG. red dyes such as RED 263 and VAT RED 41; and purple dyes such as DESPERSE VIOLET 26, SOLVENT VIOLET 13, SOLVENT VIOLET 37 and SOLVENT VIOLET 49. Among them, SOLVENT BLUE 104, SOLVENT BLUE 45, SOLVENT RED 179, SOLVENT RED 195, SOLVENT RED 135, and SOLVENT which do not contain halogen, which tends to cause equipment corrosion, have relatively good heat resistance at high temperatures, and have excellent color development. VIOLET 49 is preferred. These can be used alone or in combination of two or more.

Titanium oxide is preferably used as the titanium compound. Titanium oxide is generally used as a delustering agent or white pigment for polyester resin, but by adding an appropriate amount of titanium oxide to recycled polyester resin, the whiteness of the fiber is improved. It is preferable in that a woven or knitted fabric with a good color tone can be obtained. The amount of titanium oxide to be added is preferably 0.05 to 5 parts by mass with respect to 100 parts by mass of the polyester resin.

Crystal nucleating agents include carbon black, calcium carbonate, synthetic silicic acid and silicates, zinc oxide, high-site clay, kaolin, basic magnesium carbonate, mica, talc, quartz powder, diatomaceous earth, dolomite powder, and titanium oxide. , zinc oxide, antimony oxide, barium sulfate, calcium sulfate, alumina, calcium silicate, boron nitride, etc.; compounds and the like. Among them, mica, talc, and high molecular weight organic compounds are preferred. These can be used alone or in combination of two or more.

It is preferable to use polyethylene terephthalate (PET) mainly composed of ethylene terephthalate units for the polyester resin B, which is the readily alkali-soluble component of the present invention, in terms of alkali solubility, splittability, spinnability, and the like. In polyester resin B, it is preferable to copolymerize an aromatic dicarboxylic acid component having a sulfonic acid group with a dicarboxylic acid component in order to increase the dissolution rate due to the alkali weight reduction treatment. As the aromatic dicarboxylic acid component containing a sulfonate group, 5-sodium sulfoisophthalic acid is suitable. The amount of copolymerization is appropriately selected depending on the difference in alkali dissolution rate between polyester resin A and polyester resin B. It is suitable in terms of spinning operability and cost.

Furthermore, those copolymerized with polyalkylene glycol having an average molecular weight of 1,000 to 10,000 are preferred. Polyalkylene glycol has the effect of accelerating the dissolution rate by severing the molecular chains of the polyester and increasing the surface area by generating voids on the surface by quickly dissolving in the polyester with an alkali. . The copolymerization amount of polyalkylene glycol in the polyester is preferably 1 to 20% by mass.

A modifier (eg, matting agent, stabilizer, flame retardant, or coloring agent) may be added to the above polyester resin A and polyester resin B within a range that does not impair the effects of the present invention. In addition, various function-imparting components (e.g., cationic dye dyeable component or heat-shrinkable component) may be copolymerized or mixed and contained.

In the conjugate fiber of the present invention, polyester resin A, which is a poorly soluble alkali component, is divided into a plurality of polyester resin B, which is a highly soluble alkaline component, in the cross-sectional shape of the fiber. The conjugate fiber of the present invention is split by dissolving all or part of the polyester resin B when subjected to alkali weight reduction treatment.

Next, the arrangement of the polyester resin A and the polyester resin B in the composite fiber of the present invention will be explained. In the composite fiber of the present invention, the polyester resin A is divided into a plurality of pieces by the polyester resin B in a cross-sectional shape obtained by cutting the constituting single fiber perpendicularly to the longitudinal direction. FIGS. 1(a) to 1(d) are schematic diagrams showing embodiments of cross-sectional shapes of single fibers of such conjugate fibers. In the drawings, 1 is polyester resin A, 2 is polyester resin B, and 3 is polyester resin B. It is a hollow part.
In FIG. 1(a), a hollow portion 3 is provided near the center of the fiber, and 20 flat segments made of the polyester resin A are radially arranged around the hollow portion.
(b) shows eight substantially triangular segments made of polyester resin A arranged radially.
In (c), 19 round segments made of polyester resin A are arranged in an array.
(d) is obtained by arranging 10 flat segments made of polyester resin A radially.

In the conjugate fiber of the present invention, each segment is easily peeled off in the alkali weight reduction treatment and subsequent steps, and the degree of division is high. As shown in FIG. is present independently without contact with other segments.

The number of segments of the polyester resin A in the conjugated fiber of the present invention is not particularly limited, but considering the spinnability and the ease of making a spinneret, etc., and considering the productivity of ultrafine fibers, it should be 2 to 60 segments. 4 to 30 segments are preferred. The shape of the segment is not particularly limited, and as shown in FIG. The ultrafine fibers made of can be of various shapes.

In other words, the conjugate fiber of the present invention is divided by the alkali weight reduction treatment, and when the alkali weight reduction treatment is performed, the polyester resin B is eluted and each segment of the polyester resin A becomes an ultrafine fiber. Obtainable.

The volume composite ratio of polyester resin A and polyester resin B should be 60/40 to 95/5 in consideration of the single yarn fineness of the composite fiber, the number of divisions, the single yarn fineness of the ultrafine fiber after the division treatment, etc. is preferred, and 75/25 to 85/15 is particularly preferred. Within this range, polyester resin A can be easily divided by alkali weight reduction treatment, and the amount of polyester resin B eluted with an alkaline solution is small, which is economical. In addition, since the looseness of the structure of the fabric obtained after the alkali weight reduction treatment is small, and the occurrence of dislocation of the structure can be suppressed, it is possible to obtain a high-density fabric with excellent texture.

The ultrafine fibers made of the polyester resin A obtained after such splitting must have a single filament fineness of 1.0 dtex or less, preferably 0.5 dtex or less, and more preferably 0.2 dtex or less. is more preferable. If the ultrafine fibers are 0.5 dtex or less, the obtained fiber structure is excellent in flexibility and density, and is suitable for polishing performance and cleaning performance. Considering the spinnability and the ease of manufacturing a spinneret, the fineness of single yarn is preferably 0.01 dtex or more.

The composite fiber of the present invention may be either highly oriented undrawn yarn (POY) or drawn yarn (FDY).
The single filament fineness of the composite fiber of the present invention is not particularly limited, but considering the number of segments of the polyester resin A as described above and the single filament fineness of the ultrafine fibers obtained after splitting, it is 1 to 5.0 dtex. It is preferable to
The conjugate fiber of the present invention may be either multifilament or monofilament, but is preferably multifilament, and preferably has a total fineness of 40 to 130 dtex.

Since the composite fiber of the present invention uses, as the polyester resin A, a recycled polyester resin that satisfies the above-described characteristic values, it can have performance equivalent to that of the virgin polyester resin. Therefore, in the case of POY, the strength of the composite fiber of the present invention is preferably 2.0 cN/dtex or more, more preferably 2.4 cN/dtex or more. In the case of FDY, it is preferably 3.0 cN/dtex or more, more preferably 3.5 cN/dtex or more. In the case of POY, the elongation of the composite fiber of the present invention is preferably 90 to 140%, more preferably 100 to 130%. In the case of FDY, it is preferably 25-55%, more preferably 30-50%. By satisfying the above strength and elongation, it is possible to obtain a woven or knitted fabric with good workability without yarn breakage during weaving or knitting.

Next, the woven or knitted fabric of the present invention is a woven or knitted fabric containing at least a portion of the fibers made of the polyester resin A described above.
The content of the polyester resin A fibers contained in the woven or knitted fabric of the present invention is preferably 25% by mass or more, and more preferably 35% by mass or more. As fibers that can be used as fibers other than the fibers made of the polyester resin A, polyester fibers are preferable, and fibers having the same fineness as the composite fibers of the present invention or those having fine fineness can be used. In addition, those having high shrinkability can also be used.

Further, the woven or knitted fabric of the present invention is obtained by subjecting a woven or knitted fabric obtained by weaving or knitting using the conjugated fiber of the present invention in part to an alkaline weight reduction treatment, and polyester resin B in the conjugated fiber of the present invention. can be obtained by eluting and splitting the polyester resin A portion. Details of the manufacturing method will be described later.

The texture of the woven or knitted fabric of the present invention is not particularly limited. Woven fabrics include woven fabrics, twill weaves, satin weaves, dobby weaves, and double weaves. In the knitted fabric of the present invention, the texture of the knitted fabric is also not particularly limited, and examples thereof include circular knitting such as jersey, smooth, milling, and picket, and warp knitting such as single tricot and half tricot.

Next, a method for producing polyester resin A, which is a recycled polyester resin, will be described. In the production method of the present invention, it is important to perform the steps (1) to (4) in order.
(1) Ethylene glycol is added to the raw material so that the molar ratio of all glycol components/total acid components is 1.08 to 1.40, and depolymerization is performed under heat treatment conditions of 220 to 285°C. , a step of obtaining a depolymer having a melt viscosity of 10 to 1500 mPa s,
(2) a step of passing the depolymer through a filter having a filtration particle size of 10 to 25 μm and collecting the filtrate;
(3) adding a polycondensation catalyst to the filtrate and kneading to obtain a reaction product;

First, in the depolymerization step (1), ethylene glycol is added to the recycled polyester raw material so that the molar ratio of all glycol components/total acid components is 1.08 to 1.40, and heat treatment is performed at 220 to 285 ° C. By carrying out depolymerization under these conditions, a depolymer having a melt viscosity of 10 to 1500 mPa·s is obtained.
In the method for producing a recycled polyester resin in the present invention, the melt viscosity of the depolymer is a value measured at the heat treatment temperature during depolymerization, and is measured using a VISCO METER DV2T type melt viscometer manufactured by Brookfield. It is.

Ethylene glycol added to the recycled polyester raw material can be obtained by a known method or commercially available.

The amount of ethylene glycol added is preferably 1 to 20% by mass, more preferably 2 to 10% by mass, based on 100% by mass of the recycled polyester raw material.
If the amount of ethylene glycol to be added is less than the above range, blocking between the recycled polyester raw materials tends to occur when the recycled polyester raw materials are added, which is not preferable because the stirrer is subjected to an excessive load.

In the step (1), when the ethylene glycol and the recycled polyester raw material are added, the total glycol component/total acid component molar ratio is 1.08 to 1.40 while stirring, and the C. to obtain a depolymer having a melt viscosity of 10 to 1500 mPa.s.
This step is important in the production method of the present invention. That is, in the present invention, the recycled polyester raw material is depolymerized in the presence of ethylene glycol. Ethylene glycol and recycled polyester raw materials are added so as to have a pH of 1.08 to 1.40, and depolymerization is carried out.

In addition, when the content of the component derived from the recycled polyester raw material in the recycled polyester resin obtained by the production method of the present invention is less than 100% by mass and is 80% by mass or more, in the step (1), ethylene In addition to the glycol and recycled polyester raw material, ethylene terephthalate oligomers may be added for depolymerization. Also when adding the ethylene terephthalate oligomer, it is necessary to adjust the molar ratio of all glycol components/total acid components to 1.08 to 1.40.

As the ethylene terephthalate oligomer, for example, an esterification reaction product of ethylene glycol and terephthalic acid can be suitably used. The number average degree of polymerization of the ethylene terephthalate oligomer is not limited, but can be, for example, about 2-20.

In step (1), it is important to set the melt viscosity of the depolymer obtained by performing the above depolymerization to 10 to 1500 mPa·s.
By performing depolymerization by adjusting the molar ratio of all glycol components / all acid components and obtaining a depolymer with a melt viscosity of 10 to 1500 mPa s, not only various inorganic substances contained in recycled polyester raw materials, but also non- Since foreign substances derived from the polyester resin are deposited efficiently, these foreign substances can be completely filtered in the step (2).

Then, in the step (3) of adding and kneading the polycondensation catalyst and various additives added according to the application, it is possible to uniformly knead without aggregating the polycondensation catalyst and various additives. .
As a result, in the polycondensation reaction of the step (4), the characteristic values of the present invention are that the diethylene glycol content (copolymerization amount) and the carboxyl terminal group concentration are not more than a specific amount, and the amount of foreign matter mixed in. It is possible to obtain a recycled polyester resin with less

In the step (1) of the present invention, it is desirable that the depolymerization reaction described above decomposes the recycled polyester raw material into oligomers having about 5 to 20 repeating units without decomposing them into monomers.

If the molar ratio of the total glycol component/total acid component during the depolymerization reaction is outside the above range, the resulting recycled polyester resin will have at least one of the carboxyl terminal group concentration and the diethylene glycol content specified in the present invention. is not satisfied, and the average boosting speed is high. This is because, when the molar ratio of all glycol components/total acid components during the depolymerization reaction is outside the above range, precipitation of various inorganic substances in the recycled polyester raw material and foreign matters derived from non-polyester resins is efficiently carried out. Therefore, in the step (2), these foreign substances cannot be completely filtered out, and the foreign substances precipitate after the polycondensation reaction in the step (4), resulting in a recycled polyester resin with a high average pressurization rate. .

In addition, in the defusion reaction step (1), if the melt viscosity of the resulting depolymer is less than 10 mPa·s, the viscosity becomes too low, and liquid leakage occurs from the pipe and the filter connection portion during filtering of foreign matter. It is easy to filter, the filtration efficiency is poor, foreign matter cannot be filtered sufficiently, and productivity deteriorates. On the other hand, if the melt viscosity of the depolymer exceeds 1500 mPa s, the viscosity becomes too high, which increases the load on the stirring blade during the depolymerization reaction, and also increases the pressure when filtering foreign matter, resulting in production. sexuality worsens.

In the production method of the present invention, the reactor used in the step (1) has no particular problem with the capacity and shape of the stirring blades of a commonly used esterification reactor. In order to proceed, it is preferable to have a structure in which a distillation column is provided side by side so as not to distill ethylene glycol out of the system.
When the recycled polyester raw material is added, it is preferably stirred under normal pressure, and more preferably after purging with a small amount of inert gas (generally nitrogen gas is used).

In addition, when performing a depolymerization reaction using an ester reactor, a method of performing the depolymerization reaction by adding the recycled polyester raw material and ethylene glycol in multiple times, or a method of adding the recycled polyester raw material to the ethylene glycol. It is preferable to employ a method of adding little by little.

When performing the depolymerization reaction, a melt extruder may be used instead of the ester reactor. In the method using a melt extruder, the polymer is sealed in the extruder and extruded, so there is no contact with air (especially oxygen), so there is no oxidative decomposition of the polymer, resulting in color deterioration and an increase in carboxyl end groups. The problem of viscosity reduction of the molten polymer associated with this does not occur. Moreover, if a melt extruder is used, the reaction can be carried out under all pressure conditions such as normal pressure, increased pressure, and reduced pressure.
The melt extruder may be either a single-screw extruder or a twin-screw extruder, but it is preferable to use a twin-screw extruder because the above advantages can be easily obtained.

Furthermore, when using a melt extruder in step (1), the depolymerization reaction proceeds inside the extruder by supplying ethylene glycol to the inside of the extruder. When supplying the recycled polyester raw material, adding ethylene glycol and passing it through a melt extruder makes it easier to lower the viscosity, and discharge from the tip nozzle becomes smooth. Also, the melting temperature of the melt extruder (the temperature of the depolymerization reaction) can be lowered by changing the pressure conditions to lower the viscosity.

The melt viscosity of the depolymerized product can be adjusted within the range of the present invention by appropriately adjusting the heat treatment temperature, heat treatment time, pressure, etc. during depolymerization.

The reaction temperature during the depolymerization performed in step (1) is preferably carried out by setting the internal temperature of the reactor or melt extruder in the range of 220 to 285 ° C., especially the internal temperature in the range of 245 to 280 ° C. is more preferable. If the reaction temperature during depolymerization is less than 220°C, a long heat treatment is required to reduce the melt viscosity of the depolymerized product to 1500 mPa s or less, resulting in poor workability and the resulting recycled polyester resin. color tone deteriorates, and the content of diethylene glycol and the concentration of carboxyl end groups increase.
On the other hand, when the reaction temperature exceeds 285° C., the melt viscosity of the depolymerized product becomes too low, and the diethylene glycol content and carboxyl terminal group concentration of the resulting recycled polyester resin become high.
The reaction time at the time of depolymerization (reaction time after the completion of the addition of the recycled polyester raw material) is preferably within 4 hours, and within 2 hours from the viewpoint of suppressing the amount of by-product diethylene glycol and suppressing the deterioration of the color tone of the polyester. is more preferable.

In the step (2), the depolymerized product obtained by the depolymerization reaction in the step (1) is passed through a filter having a filtration particle size of 10 to 25 μm to filter out foreign matters. As described above, by performing a depolymerization reaction under the conditions of the step (1) and obtaining a depolymer having a melt viscosity within a specific range, even if the amount of recycled polyester raw material used is large, these raw materials Not only various inorganic substances abundantly contained in the resin, but also foreign substances derived from non-polyester resins are deposited efficiently. Therefore, by passing through a filter having a filtration particle size of 10 to 25 μm, the precipitated foreign matter can be completely caught by the filter, and a filtrate containing a small amount of foreign matter can be obtained.
If a filter with a filtration particle size of more than 25 μm is used, foreign matter in the depolymerized product cannot be sufficiently removed, and the resulting regenerated polyester resin contains a large amount of foreign matter. For this reason, when spinning is performed using such a resin, pressure rise in the nozzle pack and yarn breakage occur. On the other hand, when a filter having a filtration particle size of less than 10 μm is used, clogging due to foreign matter is likely to occur, and the filter life is shortened, which is disadvantageous in terms of cost and also deteriorates operability.

In addition, as the filter that can be used in the step (2) of the production method of the present invention, there is no particular problem with general filters, but examples thereof include screen changer filters, leaf disk filters, candle-type sintered filters, and the like.

Then, in step (3) of the production method of the present invention, the polycondensation catalyst as described above is added to the filtrate obtained through step (2) above, and the mixture is kneaded to obtain a reaction product. In the step (3), it is preferable to add additives according to various uses together with the polycondensation catalyst and knead the mixture. In addition, the above-mentioned additive can be used for the additive added according to various uses.
The temperature at which kneading is performed in step (3) is preferably within the range of plus or minus 10° C. of the temperature at which polycondensation reaction is performed in step (4).

Next, as the step (4), the reaction product obtained in the step (3) is subjected to a polycondensation reaction in a polycondensation reactor at a temperature of 260° C. or higher and a reduced pressure of 1.0 hPa or lower.
If the polycondensation reaction temperature is less than 260° C. or the pressure during the polycondensation reaction exceeds 1.0 hPa, the polycondensation reaction time will be long, resulting in poor productivity or slow progress of the polycondensation reaction. , the recycled polyester resin cannot be obtained.
More preferably, the polycondensation reaction temperature is 270° C. or higher. However, if the polycondensation reaction temperature is too high, the polymer will be colored due to thermal decomposition, and the color tone will deteriorate, and the amount of terminal groups (COOH) will increase due to thermal decomposition. , 285° C. or lower. The intrinsic viscosity of the recycled polyester resin (prepolymer) obtained here is preferably 0.44 to 0.80.

Next, a method for producing the composite fiber of the present invention will be described.
The following is an embodiment of the manufacturing method when the conjugate fiber of the present invention is FDY, and melt spinning can be performed using an ordinary conjugate spinning apparatus. In the melt composite spinning of FDY of the present invention, the polyester resin B is spun from the spinneret so that the polyester resin A is split. Specifically, polyester resin A and polyester resin B are prepared, melted separately, and flowed through separate pipes into the nozzle pack. The polymer that has flowed into the pack is joined by a spinneret, compounded into split fiber type, orange type, islands-in-the-sea type, etc., by a known technique, and discharged from the spinneret. At this time, it is appropriate to perform spinning under the conditions of a spinning temperature of 280-295° C. and a spinning speed of 3000-3600 m/min. After spinning, the polymer extruded from the spinneret is cooled and solidified, and after applying an oil solution, it is drawn and heat-treated at a drawing temperature of 70 to 90°C, a draw ratio of 1 to 2 times, and a heat treatment temperature of 140 to 170°C. , the composite fiber (FDY) of the present invention is obtained.

Next, the method for producing the woven or knitted fabric of the present invention will be described.
The woven or knitted fabric of the present invention can be obtained, for example, by subjecting a raw fabric obtained through steps such as weaving and knitting partially using the composite fiber of the present invention obtained by the above-described manufacturing method to alkali weight reduction treatment. can get.
The alkali weight reduction treatment may be performed by a conventionally known method. In the case of splittable conjugate fibers as shown in FIG. 1(a), the amount of dissolution and removal by an alkaline solution, that is, the amount of weight loss is preferably about 15 to 30% by mass, more preferably about 20 to 25% by mass. preferable. If the weight loss rate is less than 15% by mass, splitting of the splittable conjugate fiber is not sufficiently performed, and a woven or knitted fabric with a good touch tends to be obtained. On the other hand, when the weight loss rate exceeds 30% by mass, although splitting is performed well, the ultrafine fibers are slightly dissolved, and the strength of the resulting woven or knitted fabric tends to decrease.
The treatment conditions by alkali dissolution are the methods generally practiced in weight reduction processing of polyester fiber structures. can be done. More preferably 1.0% to 3.0%, particularly preferably 1.0% to 2.0%. The treatment temperature is preferably 85°C to 100°C, more preferably 90°C to 98°C.

EXAMPLES The present invention will be described in more detail below with reference to examples. The measurement and evaluation methods for various characteristic values in the examples are as follows.
(a) Melt Viscosity of Depolymer The depolymer obtained in the production step (1) is measured using a Brookfield VISCO METER DV2T melt viscometer, and the torque detected by the torque sensor inside the viscometer is 20±5%, and measured at the same processing temperature during depolymerization.
(b) Intrinsic viscosity The intrinsic viscosity is measured at a temperature of 20°C using the obtained recycled polyester resin and an equal mass mixture of phenol and ethane tetrachloride as a solvent.
(c) Composition of polyester resin The obtained recycled polyester resin is dissolved in a mixed solvent having a volume ratio of deuterated trifluoroacetic acid and deuterated chloroform of 1/11, and JNM-ECZ400R/S1 manufactured by JEOL Ltd. 1H-NMR was measured with a type NMR apparatus, and from the integrated intensity of the proton peak of each component in the obtained chart, the type and content of the copolymer component were determined.

(d) Carboxyl Terminal Group Concentration Dissolve 0.1 g of the obtained recycled polyester resin in 10 ml of benzyl alcohol, add 10 ml of chloroform to this solution, and titrate with a 1/10 N potassium hydroxide benzyl alcohol solution. rice field.
(e) Average pressurization rate measured by pressurization tester The obtained recycled polyester resin is melted at 300 ° C. in an extruder, and a stainless steel twilled woven filter (nominal size mesh: 1400 mesh, weave: twill weave, vertical mesh: 165 mesh, horizontal mesh: 1400 mesh, vertical wire diameter: 0.07 mm, horizontal wire diameter: 0.04 mm, filtration particle size: 12 μm, viscous drag coefficient (m ⁻¹ ) : 2.60 × 10 ⁷ , inertial resistance coefficient: 5.14 × 10, manufactured by Kamijo Seiki Co., Ltd.), and a reinforcing material (stainless steel plain weave wire mesh (nominal size mesh: 40 mesh, Weaving method: plain weave, wire diameter: 0.21 mm (manufactured by Kamijo Seiki Co., Ltd.) After laminating, the polymer discharge rate is set to 29.0 g / min, and the filter pressure is increased using a pressurization tester; "Measured using a detector. The pressure rise test using the pressure test machine was performed continuously for 12 hours, and the initial pressure value (MPa) when starting the pressure rise test (5 to 5 after the polyester resin started passing through the filter The initial pressure is the minimum value of the pressure for 10 minutes.) and the final pressure value (MPa) after 12 hours, the average pressure increase rate was calculated by the following formula.
Average pressure rise rate (MPa/h) = (final pressure value - initial pressure value)/12

(e) Strength of Splittable Composite Fiber According to JIS L-1013, using Autograph DSS-500 manufactured by Shimadzu Corporation, the strength was measured at a gripping distance of 25 cm and a pulling speed of 30 cm.
(f) Elongation of Splittable Composite Fiber Measured according to JIS L-1013 using Autograph DSS-500 manufactured by Shimadzu Corporation at a gripping distance of 25 cm and a pulling speed of 30 cm.
(g) Single filament fineness (dtex) of splittable conjugate fiber
Measured according to JIS L-1013 8.3.1B method.

(h) Spinnability When obtaining POY, the state of yarn breakage during melt spinning was evaluated in the following 3 stages according to the number of yarn breakages per spindle when melt spinning was performed continuously for 24 hours. bottom.
Good: The number of yarn breakages was 0.
Δ: The number of yarn breakage was 1 to 2 times.
x: The number of yarn breakages was 3 or more.
(i) Stretchability The state of thread breakage during stretching of POY was evaluated in the following three stages according to the number of breaks (total number of times) when stretching was performed continuously for 10 hours with 100 spindles.
Good: The number of cuts was 0 to 1.
Δ: The number of cuts was 2 to 4.
x: The number of cuts was 5 or more.
(j) Raised feel of fabric (raised feel, coat)
The tactile sensation of the obtained woven fabric was evaluated for the napped feeling according to the following criteria.
◯: The feeling of nap is good.
Δ: Feeling of nap is normal.
x: Insufficient nap feeling.
(k) Soft feel of woven fabric The soft feel of the obtained woven fabric was evaluated according to the following criteria.
◯: The texture is soft.
Δ: The texture is normal.
x: The texture is hard.

Recycled polyester resin (1)
23.1 parts by mass of a recycled polyester raw material (recycled PET flakes made from used products) was charged into an esterification reactor, and then 2.6 parts by mass of ethylene glycol was added while the stirrer of the esterification reactor was being rotated. . 34.6 parts by mass of recycled polyester raw material (recycled PET flakes made from used products) was added to the esterification reactor (hereinafter referred to as "ES can") over about 30 minutes from the point where the internal temperature drop stopped. After adding a fixed amount, 3.9 parts by mass of ethylene glycol was additionally added.
At this time, the recycled polyester raw material was added so that the molar ratio of all glycol components/all acid components (hereinafter sometimes referred to as "G/A") was 1.35.
Thereafter, a depolymerization reaction was carried out under heat treatment conditions of 270°C for 1 hour to obtain a depolymerized product having a melt viscosity of 60 mPa·s at 270°C.
A candle filter with an opening of 20 μm was set between the esterification reactor and the polycondensation reactor, and the obtained depolymerized product was pressure-fed to the polycondensation reactor (hereinafter referred to as a PC can). At this time, the filtrate was collected by passing the depolymerized product through the filter.
In the PC can, the filtrate was added with 1.0×10 ⁻⁴ mol/unit of antimony trioxide as a polycondensation catalyst, 0.2×10 ⁻⁴ mol/unit of cobalt acetate as a color tone adjusting agent, and 0.23 mass of titanium dioxide. and kneaded at a temperature of 270° C. to obtain a reaction product.
Next, the PC can was evacuated and after 60 minutes, a polycondensation reaction was carried out at a final pressure of 0.5 hPa and a temperature of 280° C. for 2.0 hours to obtain a recycled polyester resin (1) (intrinsic viscosity: 0.69). .

Recycled polyester resin (2) to (4)
Except for changing the amount of ethylene glycol, recycled polyester raw material, ethylene terephthalate oligomer added during the depolymerization reaction, G/A, the heat treatment temperature during the depolymerization reaction, and the melt viscosity to those shown in Table 1, the recycled polyester resin was used. A depolymerization reaction was carried out in the same manner as in (1).
In addition, a recycled polyester resin was produced in the same manner as the recycled polyester resin (1) except that the filtration particle size of the filter in the step of collecting the filtrate and the heat treatment temperature in the polycondensation reaction step were changed to those shown in Table 1.

Virgin polyester resin A slurry of terephthalic acid (TPA) and ethylene glycol (EG) (TPA/EG molar ratio = 1/1.6) was supplied to an esterification reactor and reacted at a temperature of 250°C and a pressure of 50 hPa. , an ethylene terephthalate oligomer (number average degree of polymerization: 5) having an esterification reaction rate of 95% was obtained.
100.0 parts by mass of an ethylene terephthalate oligomer was charged in a PC can, 1.0×10 ⁻⁴ mol/unit of antimony trioxide as a polymerization catalyst, and EG slurry of titanium dioxide were added to a concentration of 0.20% by mass. 60 minutes later, polycondensation reaction was carried out at a final pressure of 0.5 hPa and a temperature of 275° C. for 3 hours to obtain a virgin polyester resin (intrinsic viscosity of 0.69).

Table 1 shows the characteristic values of the recycled polyester resins (1) to (4) and the virgin polyester resin.

As is clear from Table 1, the recycled polyester resins (1) and (2) obtained by sequentially performing the steps (1) to (4) described above have a carboxyl terminal group content and a diethylene glycol content of the present invention. It was within the prescribed range, and the average pressurization rate was also low.
On the other hand, the recycled polyester resin (3) had a low G/A during the depolymerization reaction in the step (1) described above, and thus had a high carboxyl terminal group concentration and a high average pressurization rate.
The regenerated polyester resin (4) had a high G/A during the depolymerization reaction in step (1) described above, so that the content of diethylene glycol was high and the average pressurization rate was also high.

Example 1
Recycled polyester resin (1) as polyester resin A, 2.5 mol% of 5-sodium sulfoisophthalic acid (SIP-Na) as polyester resin B, and 12.0% by mass of polyethylene glycol (PEG) having an average molecular weight of 8000. Copolymerized PET having an intrinsic viscosity of 0.72 was used, the composite mass ratio of polyester resin A / B was 81.2 / 18.8, the spinning temperature was 288 ° C., the discharge rate was 36 g / min, and polyester resin B was polyester. Resin A was spun using a composite spinning apparatus equipped with a spinneret with 48 spinholes designed to split into eight. The spun yarn was cooled, oiled, and wound at a speed of 3100 m/min to obtain POY of 120 dtex/48 filaments. Next, this POY was drawn by a factor of 1.56 through a heating roller at 84° C. and heat-treated on a heat plate at 153° C. to obtain a splittable conjugate fiber (FDY) of 75 dtex/48 filaments. The resulting splittable conjugate fiber had a strength of 3.55 cN/dtex and an elongation of 36.8%, and the cross-sectional shape of each single fiber was as shown in FIG. 1(b).
The resulting splittable conjugate fiber was subjected to false twisting using a commercially available false twisting machine at a processing temperature of 175 ° C. and a false twist number of 3000 times / m. A plain weave with a warp of 145 strands/2.54 cm and a weft of 95 strands/2.54 cm was woven. The resulting plain woven fabric is subjected to alkali weight reduction treatment in the dyeing process under the conditions of caustic soda 20 g/L, bath ratio 1:30, and temperature 98° C., thereby dissolving and removing the polyester resin B from the splittable conjugate fibers in the woven fabric. Then, the polyester resin A was split into ultrafine fibers. Thereafter, a conventional finishing process was carried out to obtain a woven fabric.

Example 2
A 75 dtex/48 filament composite fiber of the present invention was obtained in the same manner as in Example 1 except that the recycled polyester resin (2) was used as the polyester resin A. Further, a woven fabric was obtained by performing weaving and alkali weight reduction treatment in the same manner as in Example 1.

Comparative example 1
Polyester-based splittable conjugate fibers of 75 dtex/48 filaments were obtained in the same manner as in Example 1, except that the recycled polyester resin (3) was used as the polyester resin A. Further, a woven fabric was obtained by performing weaving and alkali weight reduction treatment in the same manner as in Example 1.

Comparative example 2
Polyester-based splittable conjugate fibers of 75 dtex/48 filaments were obtained in the same manner as in Example 1, except that the recycled polyester resin (4) was used as the polyester resin A. Further, a woven fabric was obtained by performing weaving and alkali weight reduction treatment in the same manner as in Example 1.

Reference example 1
A polyester-based splittable conjugate fiber of 78 dtex/48 filaments was obtained in the same manner as in Example 1, except that a virgin polyester resin was used as the polyester resin A. Further, a woven fabric was obtained by performing weaving and alkali weight reduction treatment in the same manner as in Example 1.

表２から明らかなように、実施例１、２で得られたポリエステル系分割型複合繊維は、図１の（ｂ）に示すようなポリエステル樹脂Ａがポリエステル樹脂Ｂにより複数個に分割されている複雑な断面形状の複合繊維を紡糸性よく得ることができた。また、糸質物性もバージンポリエステル樹脂を用いたものと遜色がなく、実用上問題のない繊維を得ることができた。また、実施例１、２で得られたアルカリ減量処理後の織物の風合いも、アルカリ減量処理して得られたポリエステル樹脂Ａからなる繊維の形状や大きさが揃っていたため、立毛感、ソフト感ともにバージンポリエステル樹脂を用いたものと遜色がないものであった。
一方、比較例１で得られたポリエステル系分割型複合繊維は、用いた再生ポリエステル樹脂のカルボキシル末端基濃度が高かったため、紡糸性が悪く、複合繊維の断面形状は、ポリエステル樹脂Ａが図１の（ｂ）に示すような個々の形状や大きさが揃った断面形状のものとすることができなかった。また、糸質物性も低強度・低伸度のものとなった。また、得られたアルカリ減量処理後の織物の風合いは、アルカリ減量処理して得られたポリエステル樹脂Ａからなる繊維の形状や大きさにばらつきが生じたため、立毛感に劣るものであった。
比較例２で得られたポリエステル系分割型複合繊維は、用いた再生ポリエステル繊維のジエチレングリコールの含有量が高かったため、延伸性に劣る結果となり、複合繊維の断面形状は、ポリエステル樹脂Ａが図１の（ｂ）に示すような個々の形状や大きさが揃った断面形状のものとすることができなかった。また、得られたアルカリ減量処理後の織物の風合いは、アルカリ減量処理して得られたポリエステル樹脂Ａからなる繊維の形状や大きさにばらつきが生じたため、ソフト感に劣るものであった。

As is clear from Table 2, in the polyester splittable conjugate fibers obtained in Examples 1 and 2, polyester resin A is split into a plurality of pieces by polyester resin B as shown in FIG. Composite fibers with a complex cross-sectional shape could be obtained with good spinnability. In addition, the physical properties of the yarn were comparable to those using virgin polyester resin, and a practically acceptable fiber could be obtained. In addition, the texture of the fabrics obtained in Examples 1 and 2 after the alkali weight reduction treatment was uniform because the shape and size of the fibers made of the polyester resin A obtained by the alkali weight reduction treatment were uniform. Both were comparable to those using virgin polyester resin.
On the other hand, the polyester-based splittable conjugate fiber obtained in Comparative Example 1 had poor spinnability because the recycled polyester resin used had a high carboxyl terminal group concentration. As shown in (b), it was not possible to obtain a cross-sectional shape with uniform individual shapes and sizes. In addition, the filamentous physical properties were low strength and low elongation. In addition, the texture of the resulting fabric after the alkali weight reduction treatment was inferior in nap feeling due to variations in the shape and size of the fibers composed of the polyester resin A obtained by the alkali weight reduction treatment.
The polyester-based splittable conjugate fiber obtained in Comparative Example 2 had a high content of diethylene glycol in the recycled polyester fiber used, resulting in poor drawability. As shown in (b), it was not possible to obtain a cross-sectional shape with uniform individual shapes and sizes. In addition, the texture of the resulting fabric after the alkali weight reduction treatment was inferior in softness due to variations in the shape and size of the fibers composed of the polyester resin A obtained by the alkali weight reduction treatment.

1 polyester resin A
2 Polyester resin B
3 Hollow part

Claims (3)

A conjugate fiber having a polyester resin A that is a difficult alkali-eluting component and a polyester resin B that is a readily alkali-eluting component, wherein the polyester resin A is divided into a plurality of pieces by the polyester resin B in the cross-sectional shape of the fiber, , The polyester resin A contains 80% by mass or more of a component derived from at least one recycled polyester raw material of a) used polyester products and b) unused polyester resins generated in the process of manufacturing polyester products. The recycled polyester resin (polyester resin A) has a diethylene glycol content of 4 mol% or less and a carboxyl terminal group concentration of 40 equivalents when the total amount of all glycol components is 100 mol%. /t or less. Recycled polyester resin (polyester resin A ), wherein the polyester resin A has a diethylene glycol content of 4 mol% or less when the total amount of all glycol components is 100 mol%, and a carboxyl terminal group concentration of A woven or knitted fabric characterized by having an equivalent weight of 40 equivalents/t or less and a single filament fineness of fibers made of the polyester resin A of 1.0 dtex or less. The method for manufacturing the woven or knitted fabric according to claim 2,
a step of weaving or knitting the polyester-based splittable conjugate fiber according to claim 1 to obtain a gray fabric;
A method for producing a woven or knitted fabric, comprising a step of subjecting the raw fabric to an alkali weight reduction treatment to elute the polyester resin B, thereby splitting the polyester resin A portion.

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