Polyester composite fiber and woven or knitted fabric containing the polyester composite fiber

Abstract

To provide a polyester composite fiber that is a side-by-side type composite fiber at least partially using a recycled polyester resin containing a recycled polyester raw material at a high ratio, and has the same color tone and crisp as that when using a virgin polyester resin.SOLUTION: A polyester resin composite fiber characterized in that two kinds of polyester resins different in intrinsic viscosity are composited side-by-side with each other, at least one of the two kinds of polyester resins is a recycled polyester resin containing 40 mass% or larger of the recycled polyester raw material, when a total amount of the total glycol component is set to 100 mol%, the content of the diethylene glycol is 4 mol% or smaller, and the carboxyl terminal group concentration is 30 equivalent / t or smaller in the recycled polyester resin.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fiber in which two polyester resins having different limiting viscosities are combined side by side with each other, and a recycled polyester resin using a recycled polyester raw material derived from used polyester products, polyester resins, and scraps generated in the process of manufacturing products, etc. is used for at least one type of polyester resin.

Background Art

[0002] Polyethylene terephthalate (PET) has a high melting point, chemical resistance, and relatively low cost, and is therefore widely used in molded products such as fibers, films, and PET bottles. In the manufacturing and processing stages of these polyester products, the generation of scraps cannot be avoided, and they are often discarded after use. However, when incinerated, high heat is generated, which causes significant damage to the incinerator and shortens its lifespan. On the other hand, if not incinerated, they do not decompose by putrefaction and thus remain semi-permanently. In recent years, among polyester products that have been used once, plastic containers discarded as garbage have flowed into the ocean via rivers, and microplastics finely crushed by the action of waves and tides have accumulated in the bodies of marine organisms, concentrated in the food chain, and had an adverse impact on the ecosystem of marine organisms. It is regarded as a problem that plastic is a major cause of marine pollution, and movements to reduce the usage amount and switch to biodegradable plastics are occurring worldwide.

[0003] From the perspective of reducing the usage amount of such plastic products and from the perspective of environmental problems, recycling to reuse resources is being carried out in various ways. Regarding polyester products, methods of recycling polyester scraps generated in the manufacturing process and methods of collecting products that have once been on the market and discarded and reusing them as raw materials are being studied. In particular, in recent years, for fiber products, products with an eco-label certified by achieving a certain recycling rate have become widespread.

[0004] As a method of recycling using polyester scraps generated in the manufacturing process or recovered used products as recycled polyester raw materials, various methods have been proposed. For example, a method of adding methanol to PET scraps to decompose them into dimethylene terephthalate (hereinafter referred to as DMT) and ethylene glycol (hereinafter referred to as EG) (see Patent Document 1), and a method of adding EG to PET scraps for depolymerization and then adding methanol to recover DMT (see Patent Document 2) have been proposed. However, these methods involve high costs for the installation, operation, and maintenance of the recovery equipment and are not practical.

[0005] Furthermore, a method has been proposed in which PET scraps are depolymerized with EG to obtain oligomers and these are used in a polycondensation reaction (see Patent Document 3). However, the PET obtained by such a method contains many foreign substances derived from PET scraps, so there is a problem that the pressure increase rate of the filtration filter in the spinning and film-forming processes is fast, continuous long-term operation is not possible, and the processing operability is very poor.

[0006] Also, when recycling once-produced PET bottles and the like, problems include additives added to the polyester resin and items attached to the bottle body, such as caps (aluminum, polypropylene, polyethylene), inner plugs and liners (polypropylene, polyethylene), labels (paper, resins such as polystyrene, ink), adhesives, printing ink, etc. As a pretreatment for the recycling process, first, the recovered PET bottles are shaken through a sieve to remove sand, metal, etc. Then, the PET bottles are washed, the colored bottles are separated, and rough crushing is performed. Next, labels and the like are removed by air separation. Further, the PET bottle pieces are finely crushed after removing aluminum pieces derived from caps and the like. High-temperature alkaline washing is used to remove components such as adhesives, proteins, and mold, and different components such as polypropylene and polyethylene are separated by specific gravity. However, even after these steps, it has been particularly difficult to separate non-polyester resins such as polypropylene, polyethylene, and polystyrene from PET resin as described above. Therefore, even if a recycled polyester resin is obtained by the recycling methods described in Patent Documents 1 to 3 as described above, foreign substances derived from non-polyester resins cannot be sufficiently removed, and the amount of foreign substances mixed in cannot be sufficiently reduced, and it has not been possible to obtain a product having the same quality as virgin polyester resin.

[0007] The invention described in Patent Document 4 describes a method in which polyester scraps are depolymerized with ethylene glycol, filtered through a filter having an average pore size of 10 to 50 μm, and then subjected to a repolymerization reaction. And it has been shown that the obtained recycled polyester resin has a low rate of increase in filtration pressure, that is, a small amount of foreign substances mixed in. However, even in this method, foreign substances derived from non-polyester resins as described above cannot be sufficiently removed, and the amount of foreign substances mixed in cannot be sufficiently reduced. Thus, a recycled polyester resin that can sufficiently remove not only various inorganic substances but also foreign substances derived from non-polyester resins, and can obtain various products similar to virgin polyester resin and can obtain high-quality products has not yet been obtained.

[0008] When using recycled polyester resin for polyester fibers for clothing, attempts have been made to use it for various composite fibers and the like, but there has been a problem that color tones and characteristic values peculiar to composite fibers cannot be expressed compared to the case of using virgin polyester resin. Among them, for side-by-side type fibers as composite fibers, the influence of the quality of recycled polyester resin becomes large. Therefore, a side-by-side type composite fiber that uses at least a part of a recycled polyester resin using recycled polyester raw material and is excellent in color tone and crimp ratio has not yet been obtained.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0010] The present invention solves the above problems and provides a side-by-side type composite fiber using, at least in part, a recycled polyester resin containing a high proportion of recycled polyester raw materials derived from used polyester products, polyester resin, and scraps generated in the process of manufacturing products, and having the same color tone and crimp ratio as those obtained when using virgin polyester resin.

Means for Solving the Problems

[0011] As a result of intensive studies to solve the above problems, the present inventors have arrived at the present invention. That is, the gist of the present invention is as follows (1) to (3). (1) A fiber in which two polyester resins having different intrinsic viscosities are composited in a side-by-side type, and at least the high-viscosity-side polyester resin of the two polyester resins is a recycled polyester resin containing 40% by mass or more of a recycled polyester raw material obtained through a depolymerization and repolymerization process. When the total amount of all glycol components is 100 mol%, the recycled polyester resin has a diethylene glycol content of 4 mol% or less and a carboxyl end group concentration of 29.8 equivalents / t or less and the average pressure increase rate is 0.6 MPa / h or less (however, the average pressure increase rate is a value calculated by the following procedure: Using a pressure increase tester including an extruder and a pressure sensor, a stainless steel filter (nominal mesh size: 1400 mesh, weave pattern: twill fold weave, longitudinal mesh: 165 mesh, transverse mesh: 1400 mesh, longitudinal wire diameter: 0.07 mm, transverse wire diameter: 0.04 mm, filtration particle size: 12 μm) is set at the tip of the extruder, the polyester resin is melted at 300 °C in the extruder, and when the melt is extruded at a discharge rate of 29.0 g / min from the filter, taking the pressure value applied to the filter at that time as the pressure value at the start of extrusion as the "initial pressure value (MPa)", and the pressure value at the time when extrusion is continuously carried out for 12 hours thereafter as the "final pressure value (MPa)", the average pressure increase rate is calculated by the following calculation formula A based on these pressure values: Average pressure increase rate (MPa / h) = (Final pressure value - Initial pressure value) / 12 ··· A) A polyester composite fiber characterized by the above. (2) The polyester composite fiber according to (1), wherein both of the two types of polyester resins are recycled polyester resins. (3) A woven or knitted fabric containing the polyester composite fiber according to (1) or (2).

Advantages of the Invention

[0012] The polyester composite fiber of the present invention uses a recycled polyester resin for at least one of the polyester resins, which has a low amount of foreign matter mixed in and satisfies specific ranges for the carboxyl end group concentration and the content of diethylene glycol. Therefore, it has properties equivalent to those of virgin polyester resin and is excellent in thermal stability. For this reason, in the process of obtaining fibers by melt spinning, long-term continuous operation becomes possible, and products can be obtained with high productivity. Furthermore, since the polyester composite fiber of the present invention has the same color tone and crimp ratio as those using virgin polyester resin, the woven or knitted fabric using the polyester composite fiber of the present invention can be used for various clothing applications.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0014] Hereinafter, the present invention will be described in detail. The polyester composite fiber of the present invention is a fiber in which two types of polyester resins having different intrinsic viscosities are combined side by side with each other, and at least one of the two types of polyester resins is a recycled polyester resin containing 40% by mass or more of a recycled polyester raw material. The recycled polyester resin in the present invention contains 40% by mass or more of a recycled polyester raw material, and preferably contains 50% by mass or more.

[0015] If the content of the recycled polyester raw material is less than 40% by mass, the purpose of considering environmental problems cannot be achieved. Regarding the upper limit of the content of the recycled polyester raw material, although it is not particularly limited, according to the method for producing the recycled polyester resin described later, it is possible to easily obtain a recycled polyester resin with a recycled polyester raw material content of 40 to 80% by mass.

[0016] In addition, the recycled polyester resin in the present invention is preferably mainly composed of PET, and the content of PET in the recycled polyester resin is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0017] That is, in the method for producing the recycled polyester resin, PET, which is a polycondensate of ethylene glycol and terephthalic acid, can be obtained. However, when components other than ethylene glycol and terephthalic acid are present in the recycled polyester raw material, a polyester resin other than PET may be obtained by a polycondensation reaction. Therefore, as the recycled polyester resin of the present invention, in addition to the main PET, PET copolymerized with the components shown below as the acid component or glycol component may be contained.

[0018] Examples of the acid component include isophthalic acid, phthalic acid, phthalic anhydride, naphthalenedicarboxylic acid, adipic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, dodecanedioic acid, dimer acid, and furthermore trimellitic anhydride, trimellitic acid, pyromellitic acid, 1,4-cyclohexanedicarboxylic acid, sebacic acid, dimer acid, sodium 5-sulfoisophthalate, etc. Examples of the glycol component include neopentyl glycol, 1,4-butanediol, 1,2-propylene glycol, 1,5-pentanediol, 1,3-propanediol, 1,6-hexamethylene diol, diethylene glycol, 1,4-cyclohexanedimethanol, dimer diol, butylethylpropanediol, (2-methyl-1,3-propanediol, trimethylolpropane, glycerin, pentaerythritol, ethylene oxide adducts of bisphenol A or bisphenol S, etc. These components may be contained in two or more kinds.

[0019] The recycled polyester resin in the present invention contains components derived from at least one recycled polyester raw material of a) used polyester products and b) unadopted polyester generated in the process of manufacturing polyester products.

[0020] Examples of the used polyester products of a) above include polyester molded articles (including fibers) that have once been on the market and are recovered after use. Representative examples thereof include containers or packaging materials such as PET bottles. The unadopted polyester generated in the process of manufacturing the polyester products of b) above is polyester that has not reached productization. Examples thereof include resin pellets that do not meet the standards, materials that become unnecessary during molding, fragments cut during molding, scraps (polyester scraps) generated during molding, processing, etc., cuttings of transitional products generated during brand change, cuttings of prototypes and defective products, etc.

[0021] The above (a) and (b) are not limited in their forms, etc., and may be pelletized by further performing processing such as pulverization and cutting as necessary, or may be melted and pelletized. The above (a) and (b) may be used alone or a mixture of both may be used.

[0022] In addition, as the recycled polyester raw materials of the above (a) and (b), either crystalline or amorphous ones may be used. Therefore, for example, pellets of amorphous polyester scraps that have not been heat-treated, crystalline pellets that have been heat-treated, mixtures of crystalline pellets and amorphous pellets, etc. can be used. In the present invention, it is particularly preferable to use a crystalline recycled polyester raw material for the purpose of preventing fusion between pellets during charging into the can or during the depolymerization reaction. Therefore, those obtained by crystallizing the materials of the above (a) or (b) by heat treatment (such as crystallized pellets) can be preferably used.

[0023] In addition, the properties of the recycled polyester raw materials of the above (a) and (b) are not limited, and they may remain in the forms of the above (a) and (b), or in addition to cut pieces, pulverized materials (powders), etc. obtained by further processing such as cutting and pulverization, solid forms such as molded bodies (pellets, etc.) formed by molding these can be mentioned. More specifically, pellets obtained by cooling and cutting a melt of polyester scraps, cut pieces obtained by finely cutting a polyester molded product such as a PET bottle, etc. are exemplified. In addition, it may be in the form of a liquid (dispersion or solution) obtained by dispersing or dissolving the above-mentioned cut pieces, pulverized materials (powders), etc. in a solvent. When manufacturing a polyester product using these raw materials, these can be melted at a temperature equal to or higher than their melting point and charged into the can as a melt as necessary.

[0024] The recycled polyester resin in the present invention preferably has the characteristic values of (a) and (b) shown below and preferably has the characteristic value of (c). (a) The carboxyl end group concentration is 30 equivalents / t or less (b) When the total amount of all glycol components is 100 mol%, the content of diethylene glycol is 4 mol% or less (c) The average pressure increase rate measured by a pressure increase tester is 0.6 MPa / h or less. The recycled polyester resin having these characteristic values can be obtained by the method for producing a recycled polyester resin described below.

[0025] First, as the characteristic value of (a) in the recycled polyester resin of the present invention, the carboxyl terminal group concentration is 30 eq / t or less, preferably 25 eq / t or less, and more preferably 20 eq / t or less. The recycled polyester resin of the present invention has excellent heat resistance because the carboxyl terminal group concentration is 30 eq / t or less. Therefore, the viscosity does not decrease during melt extrusion, and the crimping performance caused by the viscosity difference between the two types of polyester resins is fully exhibited. When the carboxyl terminal group concentration exceeds 30 eq / t, the viscosity decreases during melt extrusion, and the crimping performance decreases because the viscosity difference between the two types of polyester resins becomes small.

[0026] As the characteristic value of (b) in the recycled polyester resin of the present invention, when the total amount of all glycol components is 100 mol%, the content of diethylene glycol is 4 mol% or less, preferably 3.5 mol% or less. The recycled polyester resin of the present invention has a small amount of diethylene glycol produced as a by-product, and has excellent heat resistance and thermal stability because the content of diethylene glycol is 4 mol% or less. Therefore, as described above, the viscosity does not decrease during melt extrusion, and the crimping performance caused by the viscosity difference between the two types of polyester resins is fully exhibited. When the content of diethylene glycol exceeds 4 mol%, the viscosity decreases during melt extrusion, and the crimping performance decreases because the viscosity difference between the two types of polyester resins becomes small. In addition, when a recycled polyester resin having a diethylene glycol content exceeding 4 mol% is used as the polyester resin on the low viscosity side, the shrinking force of the resin itself becomes stronger, and the shrinkage difference from the polyester resin on the high viscosity side becomes small, so the crimping performance decreases.

[0027] 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. Therefore, it is possible to make the average pressure increase rate measured by a pressure increase tester, which is the characteristic value of (c), 0.6 MPa / h or less. Among them, the average pressure increase rate measured by a pressure increase tester, which is the characteristic value of (c), is preferably 0.5 MPa / h or less, and more preferably 0.4 MPa / h or less. Since the recycled polyester resin in the present invention has the characteristic value of (c), the number of yarn breaks during melt spinning can be reduced, and the polyester composite fiber of the present invention can be obtained with high productivity in the same manner as when using virgin polyester resin. Further, even if the polyester composite fiber of the present invention has a single fiber fineness of 1.0 dtex or less, it can be manufactured. Note that the lower limit value of the average pressure increase rate can be, for example, about 0.01 MPa / h, but is not limited thereto.

[0028] The method for measuring the average pressure increase rate uses a pressure increase tester including an extruder and a pressure sensor. The filter is set at the tip of the extruder, and the polyester resin is melted at 300 °C in the extruder. When the melt is extruded at a discharge rate of 29.0 g / min from the filter, taking the pressure value applied to the filter as the "initial pressure value (MPa)" at the start of extrusion and the pressure value at the time when extrusion is continuously carried out for 12 hours as the "final pressure value (MPa)", the average pressure increase rate is calculated by the following calculation formula A based on these pressure values: Average pressure increase rate (MPa / h) = (Final pressure value - Initial pressure value) / 12) ··· A) It is by such a method.

[0029] For the extruder, filter, etc. used in the above measurement, as long as the regulations of the present invention are satisfied, known or commercially available ones can also be appropriately used.

[0030] In the present invention, if necessary, within a range that does not substantially affect the measurement results as shown in the test examples described later, a reinforcing material may be added to the filter. In the above measurement method, since an extremely high pressure is applied to the filter, the filter alone may be deformed or damaged. In such a case, it is preferable to support the filter with a reinforcing material. As the reinforcing material, a mesh-like metal member or the like can be used. More specifically, a metal filter having a strength capable of preventing deformation of the filter and a coarse mesh that does not substantially affect the measurement results can be preferably used as the reinforcing material. And such a reinforcing material can be used by laminating it on the downstream side of the above filter.

[0031] Next, the manufacturing method of the recycled polyester resin in the present invention will be described. In the manufacturing method, it is important to perform the steps shown in (1) to (5) in order. (1) Add a slurry of ethylene glycol and terephthalic acid to obtain an ethylene terephthalate oligomer. (2) Add ethylene glycol to the oligomer obtained in (1). (3) While stirring under normal pressure, add a recycled polyester raw material to the oligomer added with ethylene glycol obtained in (2) so that the molar ratio of the total glycol component / total acid component is 1.08 to 1.35, and perform depolymerization under heat treatment conditions of 245 to 280 °C. (4) Pass the depolymerized product obtained in (3) through a metal filter with a filtration particle size of 10 to 25 μm to filter foreign matters. (5) Add a polymerization catalyst to the depolymerized product after filtering foreign matters obtained in (4), and perform a polycondensation reaction under reduced pressure at a temperature of 260 °C or higher and 1.0 hPa or lower.

[0032] First, in the step (1), as a pre-step of depolymerizing the recycled polyester raw material, a slurry of ethylene glycol and terephthalic acid is added to obtain an esterification product (ethylene terephthalate oligomer). The amount of the ethylene terephthalate oligomer is preferably 0.20 to 0.80% by mass, more preferably 0.30 to 0.70% by mass, in 100% by mass of the finally obtained recycled polyester resin. When the amount of the ethylene terephthalate oligomer is less than the above, when the recycled polyester raw material is charged in the step (3), the recycled polyester raw materials are likely to cause blocking, and an excessive load is applied to the stirrer, which is not preferable. On the other hand, when the amount of the ethylene terephthalate oligomer is more than the above range, there is no particular problem in the depolymerization reaction, but the recycling rate of the finally obtained recycled polyester resin becomes low, which is not preferable.

[0033] In the step (2), ethylene glycol is added to the ethylene terephthalate oligomer obtained in (1). The addition amount of ethylene glycol at this time is preferably 5 to 15% by mass, more preferably 10 to 15% by mass, based on 100% by mass of the ethylene terephthalate oligomer in order to sufficiently progress the depolymerization reaction in the step (3). When the addition amount of ethylene glycol exceeds 15% by mass, the ethylene terephthalate oligomer is likely to solidify in the reactor, and the subsequent reaction may not be able to continue, which is not preferable. When adding ethylene glycol to the ethylene terephthalate oligomer, for the purpose of preventing the oligomer from solidifying, it is preferable to make the temperature of the content uniform while rotating the stirrer and then add it.

[0034] In the step (3), the recycled polyester raw material is charged into the oligomer added with ethylene glycol obtained in (2) while stirring. At this time, it is charged so that the molar ratio of the total glycol component / total acid component becomes 1.08 to 1.35, and depolymerization is carried out under heat treatment conditions of 245 to 280°C. In the method for producing recycled polyester resin, this step is important. That is, in the conventional method using recycled polyester raw materials, depolymerization is carried out using only recycled polyester raw materials. However, in the present invention, depolymerization of the recycled polyester raw material is carried out in the presence of ethylene terephthalate oligomer and ethylene glycol, and all components of the oligomer, ethylene glycol, and recycled polyester raw material are used to make the molar ratio of total glycol components / total acid components 1.08 to 1.35, and then the recycled polyester raw material is charged and depolymerized. The molar ratio of total glycol components / total acid components is preferably 1.10 to 1.33, and more preferably 1.12 to 1.30.

[0035] By performing the steps (1) to (3) as described above, precipitation of not only various inorganic substances but also foreign substances derived from non-polyester resins is efficiently carried out. Therefore, in the step (4), these foreign substances can be filtered out without omission. And in the polycondensation reaction of the step (5), as characteristic values of the recycled polyester resin of the present invention, a recycled polyester resin having a content of diethylene glycol and a carboxyl terminal group concentration of a specific amount or less and a small amount of foreign substances mixed therein can be obtained. In addition, in the production method of the present invention, it is desirable that the recycled polyester raw material is decomposed not to monomers but to oligomers having about 5 to 20 repeating units by the above depolymerization reaction. By controlling in this way, precipitation of not only various inorganic substances but also foreign substances derived from non-polyester resins is efficiently carried out, and as a result, more foreign substances can be removed.

[0036] When the molar ratio of the total glycol components to the total acid components during the depolymerization reaction is outside the above range, the resulting recycled polyester resin fails to satisfy at least one of the carboxyl terminal group concentration and the content of diethylene glycol as defined in the present invention, and also has a high average pressure increase rate. This is because when the molar ratio of the total glycol components to the total acid components during the depolymerization reaction is outside the above range, precipitation of various inorganic substances and foreign substances derived from non-polyester resins does not occur efficiently. Therefore, in the step (4), these foreign substances cannot be filtered out completely, and foreign substances precipitate after the polycondensation reaction in the step (5). As a result, it is considered that a recycled polyester resin with a high average pressure increase rate is obtained.

[0037] The reaction temperature during depolymerization carried out in the step (3) is preferably set by setting the internal temperature of the reactor in the range of 245 to 280°C, and more preferably in the range of 255 to 280°C. When the reaction temperature during depolymerization is less than 245°C, the reactants solidify, the operability deteriorates, and even if a recycled polyester resin is obtained, the content of diethylene glycol and the carboxyl terminal group concentration become too high. When the reaction temperature exceeds 280°C, the content of diethylene glycol and the carboxyl terminal group concentration of the resulting recycled polyester resin become too high. Also, the reaction time of depolymerization (the reaction time after the completion of the input of the recycled polyester raw material) is preferably within 4 hours, and more preferably within 2 hours from the viewpoint of suppressing the by-product amount of diethylene glycol and suppressing the deterioration of the color tone of the polyester.

[0038] In the step (4), the depolymerized product obtained by the depolymerization reaction in the step (3) is passed through a metal filter with a filtration particle size of 10 to 25 μm to filter out foreign substances. As described above, by carrying out the depolymerization reaction under the conditions of the step (3), precipitation of not only various inorganic substances but also foreign substances derived from non-polyester resins occurs efficiently. Therefore, by passing through a metal filter with a filtration particle size of 10 to 25 μm, the precipitated foreign substances can be filtered out, and a depolymerized product with a small amount of foreign substance contamination can be obtained.

[0039] When using a metal filter with a filtration particle size larger than 25 μm, foreign substances in the polymer cannot be sufficiently removed, and the amount of foreign substances in the resulting recycled polyester resin increases. Therefore, when spinning using such a resin, pressure increase in the nozzle pack and yarn cutting occur. On the other hand, when using a metal filter with a filtration particle size smaller than 10 μm, clogging due to foreign substances is likely to occur, and the filter life becomes short, which is disadvantageous in terms of cost and also deteriorates the operability.

[0040] In addition, as the metal filter that can be used in the step (4) of the present invention, there is no particular problem with general ones, and examples include a screen changer type filter, a leaf disk filter, and a candle type sintered filter.

[0041] And in the method for producing a recycled polyester resin, a polymerization catalyst is added to the depolymerized product after foreign substance filtration obtained through the above step (4), and a polycondensation reaction is carried out under reduced pressure at a temperature of 260 °C or higher and 1.0 hPa or lower. As the polymerization catalyst, for example, one or more of germanium, antimony, titanium, and cobalt compounds can be used, but preferably a germanium or antimony compound is used. Further, when emphasizing the transparency of the resulting recycled polyester resin, it is preferable to use a germanium compound. Examples of the compounds of germanium or antimony include their oxides, inorganic acid salts, organic acid salts, halides, sulfides, etc. These polycondensation catalysts are 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 or more is more preferable. In addition, since the polymerization catalyst contained in the recycled polyester raw material may also act as a catalyst during the polycondensation reaction, when adding the polymerization catalyst in the step (4), it is preferable to consider the amount and type of the polymerization catalyst contained in the recycled polyester raw material.

[0042] Also, during the polycondensation reaction, a fatty acid ester, a hindered phenol antioxidant, or a phosphorus compound can be added together with the above polymerization catalyst to carry out the polycondensation reaction.

[0043] Then, in the polycondensation reaction tank, the polycondensation reaction is carried out under a reduced pressure of 260°C or higher and 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 prolonged, resulting in poor productivity. The polycondensation reaction temperature is more preferably 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. Also, since the amount of end groups (COOH) will increase due to thermal decomposition, in the present invention, the upper limit of the polycondensation reaction temperature is preferably 285°C or lower.

[0044] The intrinsic viscosity of the recycled polyester resin obtained by the above polycondensation reaction is preferably 0.44 to 0.80. In addition, the recycled polyester resin can also be used for molding applications by increasing its degree of polymerization through a solid-phase polymerization reaction process. In this case, the intrinsic viscosity of the obtained recycled polyester resin is preferably 0.80 to 1.25.

[0045] In the recycled polyester resin of the present invention, various additives other than the above-mentioned polymerization catalysts, antioxidants, phosphorus compounds, etc. may be contained as long as the effects are not impaired. As various additives, as a color inhibitor, for example, phosphorus compounds such as phosphorous acid, phosphoric acid, trimethyl phosphite, triphenyl phosphite, tridecyl phosphite, trimethyl phosphate, tridecyl phosphate, triphenyl phosphate, etc. can be used. These phosphorus compounds can be used alone or in combination of two or more. Also, additives such as cobalt compounds such as cobalt acetate, manganese compounds such as manganese acetate, anthraquinone-based dye compounds, copper phthalocyanine-based compounds, etc. may be contained to suppress the coloring due to thermal decomposition of the polyester resin.

[0046] The polyester composite fiber of the present invention is obtained by side-by-side composite of two types of polyester resins having different limiting viscosities, and crimps are developed by performing heat treatment such as dyeing treatment. The polyester composite fiber of the present invention uses the above-mentioned recycled polyester resin for at least one of two types of polyester resins having different limiting viscosities. Among them, it is preferable to use recycled polyester resins for both types of polyester resins because it is highly considerate of the environment.

[0047] When using the recycled polyester resin for only one type of polyester resin, it is preferable to use the recycled polyester resin for the polyester resin on the high-viscosity side. This is because when the polyester composite fiber of the present invention exhibits crimps, the polyester resin on the high-viscosity side is arranged inside the composite fiber, and the exposure to the fiber surface is reduced.

[0048] When the polyester composite fiber of the present invention side-by-side composites two types of polyester resins having different limiting viscosities, the joint surface of the two types of polyester resins may be either linearly and almost equally joined or joined with a curved joint surface.

[0049] As the two types of polyester resins having different limiting viscosities, the limiting viscosity of the polyester resin on the high-viscosity side is preferably 0.60 to 0.80, and the limiting viscosity of the polyester resin on the low-viscosity side is preferably 0.40 to 0.58. Also, considering the developability of crimps after heat treatment, the difference in the limiting viscosities of the polyester resin on the high-viscosity side and the polyester resin on the low-viscosity side is preferably 0.10 to 0.30. Also, the mass ratio of the polyester resin on the high-viscosity side to the polyester resin on the low-viscosity side is preferably 30 / 70 to 70 / 30.

[0050] In the polyester composite fiber of the present invention, when using a polyester resin (virgin polyester resin) different from the recycled polyester resin, it is preferable to use PET. In addition, PET copolymerized with at least one component of isophthalic acid, sodium 5-sulfoisophthalate, bisphenol A or 2,2-bis{4-(β-hydroxy)phenyl}propane, or polybutylene terephthalate can also be used.

[0051] The woven or knitted fabric of the present invention contains the polyester composite fiber of the present invention. In the woven or knitted fabric of the present invention, the content of the polyester composite fiber of the present invention is preferably 30% by mass or more, and particularly preferably 50% by mass or more, and even more preferably 70% or more. The woven fabric of the present invention can have various weaves, but it is preferable to use the polyester composite fiber of the present invention as the warp and weft yarns to form plain weave, twill, double weave, etc. The knitted fabric of the present invention can have various stitches, but it is preferable to use the polyester composite fiber of the present invention as the main constituent fiber to form single knit (jersey), double knit (smooth, ponch, tack reversible), tricot, etc.

Examples

[0052] Next, the present invention will be specifically described using examples. The measurement and evaluation methods of various characteristic values in the examples are as follows. (a) Intrinsic viscosity It is measured at a temperature of 20°C using an equal-mass mixture of phenol and tetrachloroethane as the solvent. (b) Composition of polyester resin It is dissolved in a mixed solvent with a volume ratio of deuterated hexafluoroisopropanol to deuterated chloroform of 1 / 20, and 1H-NMR is measured using a JEOL LA-400 type NMR apparatus. The type and content of the copolymerized components are determined from the integral intensities of the proton peaks of each component in the obtained chart. (c) Carboxyl end group concentration 0.1 g of the obtained recycled polyester resin was dissolved in 10 ml of benzyl alcohol. After adding 10 ml of chloroform to this solution, it was titrated with a 1 / 10 normal potassium hydroxide benzyl alcohol solution to determine it.

[0053] (d) Average pressure increase rate measured by a pressure increase tester The obtained recycled polyester resin was melted at 300 °C in an extruder. As a filter at the tip of the extruder, a stainless steel twill weave 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 resistance coefficient (m-1): 2.60×107, inertial resistance coefficient: 5.14×10, manufactured by Jotetsu Seiki Co., Ltd.) was set. Further, a reinforcing material (a stainless steel plain weave wire mesh (nominal size mesh: 40 mesh, weave: plain weave, wire diameter: 0.21 mm, manufactured by Jotetsu Seiki Co., Ltd.)) was laminated on the back (downstream side). Then, with the polymer discharge rate set to 29.0 g / min, the filter pressure was measured using a pressure increase tester; "MES-Y44D type" detector manufactured by Asahi Gauge Co., Ltd. The pressure increase test using the above pressure increase tester was continuously carried out for 12 hours. From the initial pressure value (MPa) at the start of the pressure increase test (the minimum value of the pressure between 5 and 10 minutes after the polyester resin starts to pass through the filter is taken as the initial pressure.) and the final pressure value (MPa) at the time when 12 hours have elapsed, the average pressure increase rate is calculated by the following calculation formula. Average pressure increase rate (MPa / h) = (Final pressure value - Initial pressure value) / 12

[0054] (e) Spinnability When obtaining undrawn yarns, the situation of yarn breakage during melt spinning was evaluated in three levels as follows based on the number of yarn breakages per spindle when melt spinning was continuously carried out for 24 hours. ○ ·· The number of yarn breakages was 0 times. △ ·· The number of yarn breakages was 1 to 2 times. × ·· The number of yarn breakages was 3 times or more. (f) Drawability The situation of thread breakage when stretching the non-stretched thread was evaluated in three levels as follows based on the number of cutting times (total number) of 100 bobbins when stretching continuously for 10 hours. ○·· The number of cutting times was 0 to 1 time. △·· The number of cutting times was 2 to 4 times. ×·· The number of cutting times was 5 times or more. (g) Crimp ratio The obtained polyester conjugate fiber was wound 10 times with a measuring machine, then left for 30 minutes with a load of 1 / 6800 (cN / dtex) applied, and then placed in boiling water for 30 minutes while maintaining this state to make the crimp apparent and obtain a crimped conjugate fiber. After that, it was air-dried for 30 minutes, a load of 1 / 570 (cN / dtex) was applied, and the length (a) was measured. Next, after removing the load of 1 / 570 (cN / dtex), a load of 1 / 23 (cN / dtex) was applied and its length (b) was measured, and the crimp ratio was obtained by the following formula. Crimp ratio (%) = 〔(b - a) / b〕×100 (h) Color tone b value For the obtained knitted fabric, the b value was measured using a color difference meter (Color Difference Meter CR-300 manufactured by Minolta Camera Co., Ltd.). Note that the smaller the b value, the bluer it is, and the larger the b value, the yellower it is.

[0055] [Manufacture of recycled polyester resin] Recycled polyester resin (1) 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 under the conditions of a temperature of 250°C and a pressure of 50 hPa to obtain an ethylene terephthalate oligomer (number average degree of polymerization: 5) with an esterification reaction rate of 95%. Charge 45.0 parts by mass of ethylene terephthalate oligomer into the esterification reactor. Subsequently, with the stirrer of the esterification reactor running, add 10.0 parts by mass of ethylene glycol. From the point where the internal temperature drop of the esterification reactor (hereinafter referred to as the ES tank) bottoms out, quantitatively charge 55.0 parts by mass of recycled polyester raw material (pellets of polyester scraps generated in the process of manufacturing polyester resin) through a rotary valve over about 2 h. At this time, the recycled polyester raw material was charged so that the molar ratio of the total glycol component to the total acid component (hereinafter sometimes referred to as G / A) was 1.20. Subsequently, a depolymerization reaction was carried out for 1 h under heat treatment conditions of 270 °C. Then, the obtained depolymerized product was pumped to the polycondensation reactor (hereinafter referred to as the PC tank) after setting a candle filter with an aperture of 20 μm between the esterification reactor and the polycondensation reactor. Then, 1.0×10-4 mol / unit of antimony trioxide and a TiO2 EG slurry were added so that the content was 0.20% by mass as a polymerization catalyst. The pressure in the PC tank was reduced, and a melt polymerization reaction was carried out at a final pressure of 0.5 hPa and a temperature of 275 °C for 4 h after 60 min to obtain recycled polyester resin (1) (intrinsic viscosity 0.64).

[0056] Recycled polyester resin (2) In the same manner as recycled polyester resin (1), an ethylene terephthalate oligomer with an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained. Charge 30.0 parts by mass of ethylene terephthalate oligomer into the ES tank. Subsequently, with the stirrer of the ES tank running, add 7.0 parts by mass of ethylene glycol. From the point where the internal temperature drop of the ES tank bottoms out, quantitatively charge 70.0 parts by mass of recycled polyester raw material (the same as recycled polyester resin (1)) through a rotary valve over about 2 h. At this time, the recycled polyester raw material was charged so that the molar ratio of the total glycol component / total acid component was 1.10. Then, a depolymerization reaction was carried out for 1 hour under heat treatment conditions of 270 °C. And, after setting a candle filter with an opening of 20 μm between the ES can and the PC can and pumping the obtained depolymerized product to the PC can, antimony trioxide was added as a polymerization catalyst at 1.0×10 -4 mol / unit, and the PC can was depressurized. After 60 minutes, a melt polymerization reaction was carried out at a final pressure of 0.8 hPa and a temperature of 275 °C for 5 hours to obtain a recycled polyester resin (2) (intrinsic viscosity 0.65).

[0057] Recycled polyester resin (3) In the same manner as in the recycled polyester resin (1), an ethylene terephthalate oligomer with an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained. 30.0 parts by mass of the ethylene terephthalate oligomer was charged into the ES can, and then 2.5 parts by mass of ethylene glycol was added with the stirrer of the ES can rotating. From the point where the internal temperature drop of the ES can bottomed out, 70.0 parts by mass of the recycled polyester was quantitatively added through a rotary valve over about 2 hours. At this time, the recycled polyester raw material (the same as the recycled polyester resin (1)) was charged so that the molar ratio of the total glycol component / total acid component was 1.06. Then, a depolymerization reaction was carried out for 1 hour under heat treatment conditions of 270 °C. And, after setting a candle filter with an opening of 20 μm between the ES can and the PC can and pumping the obtained depolymerized product to the PC can, antimony trioxide was added as a polymerization catalyst at 1.0×10 -4 mol / unit, cobalt acetate was added at 0.5×10 -4 mol / unit, and an EG slurry of titanium dioxide was added to be 0.40% by mass. The PC can was depressurized, and after 60 minutes, a melt polymerization reaction was carried out at a final pressure of 0.4 hPa and a temperature of 275 °C for 4 hours to obtain a recycled polyester resin (3) (intrinsic viscosity 0.64).

[0058] Recycled polyester resin (4) In the same manner as the recycled polyester resin (1), an ethylene terephthalate oligomer with an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained. 50.0 parts by mass of the ethylene terephthalate oligomer was charged into an ES can, and then 19.0 parts by mass of ethylene glycol was added with the stirrer of the ES can rotating. From the time when the internal temperature drop of the ES can bottomed out, 50.0 parts by mass of the recycled polyester was quantitatively added through a rotary valve over about 2 h. At this time, the recycled polyester raw material (the same as the recycled polyester resin (1)) was added so that the molar ratio of the total glycol component / total acid component was 1.36. Thereafter, a depolymerization reaction was carried out for 1 hour under heat treatment conditions of 270 °C. Then, the obtained depolymerized product was pumped to a PC can after setting a candle filter with an aperture of 20 μm between the ES can and the PC can, and then antimony trioxide was used as a polymerization catalyst at 1.0×10 -4 mol / unit, cobalt acetate at 0.5×10 -4 mol / unit, and an EG slurry of titanium dioxide was added to be 0.40% by mass. The pressure in the PC can was reduced, and a melt polymerization reaction was carried out at a final pressure of 0.4 hPa and a temperature of 275 °C for 4 hours after 60 minutes to obtain a recycled polyester resin (4) (limiting viscosity 0.64).

[0059] Recycled polyester resin (5) It was carried out in the same manner as the recycled polyester resin (1) except that the melt polymerization reaction time was changed to 3 hours, and a recycled polyester resin (5) (limiting viscosity 0.46) was obtained.

[0060] Virgin polyester resin (1) 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 under conditions of a temperature of 250 °C and a pressure of 50 hPa to obtain an ethylene terephthalate oligomer with an esterification reaction rate of 95% (number average degree of polymerization: 5). Charge 100.0 parts by mass of ethylene terephthalate oligomer into a PC can, add 1.0×10-4 mol / unit of antimony trioxide as a polymerization catalyst and 0.20% by mass of a titanium dioxide EG slurry, reduce the pressure in the PC can, and carry out a melt polymerization reaction at a final pressure of 0.5 hPa and a temperature of 275°C for 3 hours after 60 minutes to obtain virgin polyester resin (1) (intrinsic viscosity 0.46).

[0061] Example 1 Using recycled polyester resin (1) on the high viscosity side and virgin polyester resin (1) on the low viscosity side, supply them in equal volumes to a composite spinning type melt extruder. Melt at a spinning temperature of 285°C, merge both components at the back of a spinneret having 24 spinning holes, and spin them as a side-by-side type (S / S) composite fiber. Cool the spun yarn with an air stream and apply an oil agent by passing it through an oiling device (oil agent supply device). Wind up this yarn at a spinning speed of 3300 m / min to obtain a 167 dtex / 24f side-by-side type composite fiber (semi-undeformed yarn). Next, stretch the obtained side-by-side type composite fiber (semi-undeformed yarn) 1.53 times through a 90°C hot roller using a conventional stretching machine, and further perform heat treatment with a 170°C heat plate and wind up to obtain a 110 dtex / 24f polyester composite fiber. Using a double-sided circular knitting machine (JIL-7 type, 30″×18G) manufactured by Fukuhara Seiki Co., Ltd., feed the obtained polyester composite fiber to all yarn feed ports in the knitting structure shown in Figure 1, knit with a knitting length of 1 loop in the green state of 3.4 mm, and then perform a normal dyeing process for polyester to obtain a stretch knitted fabric.

[0062] Example 2 Melt spinning and stretching were carried out in the same manner as in Example 1 except that recycled polyester resin (2) was used on the high viscosity side to obtain a polyester composite fiber. Then, a stretch knitted fabric was obtained in the same manner as in Example 1.

[0063] Example 3 Melt spinning and stretching were carried out in the same manner as in Example 1 except that recycled polyester resin (5) was used on the low viscosity side to obtain a polyester composite fiber. Then, a stretch knitted fabric was obtained in the same manner as in Example 1.

[0064] Example 4 Using a double-sided circular knitting machine (JIL-7 type, 30″×18G) manufactured by Fukuhara Seiki Co., Ltd., with the knitting structure shown in Fig. 2, at the yarn feed port F1, the polyester composite fiber obtained in Example 1 and 44 dtex of polyurethane fiber were supplied by adding yarn knitting so that the polyurethane fiber was on the inside. At the yarn feed ports F2, F3, and F4, the polyester composite fiber obtained in Example 1 was supplied, and after knitting with a knitting length of 5.4 mm for one loop on the knitting machine, normal polyester dyeing was performed to obtain a stretch knitted fabric.

[0065] Comparative Example 1 Except for using recycled polyester resin (3) on the high viscosity side, melt spinning and drawing were performed in the same manner as in Example 1 to obtain a polyester composite fiber. Then, a stretch knitted fabric was obtained in the same manner as in Example 1.

[0066] Comparative Example 2 Except for using recycled polyester resin (4) on the high viscosity side and recycled polyester resin (5) on the low viscosity side, melt spinning and drawing were performed in the same manner as in Example 1 to obtain a polyester composite fiber. Then, a stretch knitted fabric was obtained in the same manner as in Example 1.

[0067] The characteristic values and evaluation results of the polyester composite fibers and stretch knitted fabrics obtained in Examples 1 to 3 and Comparative Examples 1 to 2 are shown in Table 2.

[0068] [Table 1]

[0069] [Table 2]

[0070] As is clear from Tables 1 and 2, the polyester composite fibers obtained in Examples 1 to 3 used, as the recycled polyester resin, those having the carboxyl end group amount, the content of diethylene glycol, and the average pressure increase rate within the ranges defined in the present invention. Therefore, they could be obtained with good spinnability and drawability. Furthermore, they had excellent crimp ratio, and the obtained knitted fabric was also excellent in color tone.

[0071] On the other hand, in Comparative Example 1, since a polyester resin with a high carboxyl end group amount and a high average pressure increase rate was used as the high-viscosity-side polyester resin, thermal decomposition occurred during melt extrusion, and the spinnability deteriorated due to an increase in contamination of the spinneret. Furthermore, after melt extrusion, the viscosity of the low-viscosity-side polyester resin decreased, and the obtained polyester composite fiber was inferior in crimp performance and color tone (knitted fabric). In Comparative Example 2, since a polyester resin with a high content of diethylene glycol was used as the high-viscosity-side polyester resin, a decrease in viscosity occurred during melt extrusion, cutting occurred during heat treatment during drawing, and it was inferior in drawability. And the obtained polyester composite fiber was inferior in crimp performance and color tone (knitted fabric).

Explanation of Signs

[0072] One loop in knitted fabric A C Cylinder needle. D Dial needle. F1 to F4 Yarn supply ports G Polyurethane fiber H Polyester composite fiber

Claims

1. Fibers in which two polyester resins with different limiting viscosities are side-by-side composite with each other, wherein at least the polyester resin on the high-viscosity side of the two polyester resins is a recycled polyester resin containing 40% by mass or more of a recycled polyester raw material obtained through a depolymerization and repolymerization process. When the total amount of all glycol components is 100 mol%, the recycled polyester resin has a diethylene glycol content of 4 mol% or less, a carboxyl end group concentration of 29.8 eq / t or less, and an average pressure increase rate of 0.6 MPa / h or less (however, the average pressure increase rate is a value calculated by the following procedure: Using a pressure increase tester including an extruder and a pressure sensor, a stainless steel filter (nominal size mesh: 1400 mesh, weave: twill weave, longitudinal mesh: 165 mesh, transverse mesh: 1400 mesh, longitudinal wire diameter: 0.07 mm, transverse wire diameter: 0.04 mm, filtration particle size: 12 μm) is set at the tip of the extruder, the polyester resin is melted at 300 °C in the extruder, and when the melt is extruded at a discharge rate of 29.0 g / min from the filter, taking the pressure value applied to the filter as the "initial pressure value (MPa)" at the start of extrusion and the pressure value at the time of continuous extrusion for 12 hours thereafter as the "final pressure value (MPa)", the average pressure increase rate is calculated by the following calculation formula A based on these pressure values: Average pressure increase rate (MPa / h) = (Final pressure value - Initial pressure value) / 12... A), characterized by the polyester composite fiber.

2. The polyester composite fiber according to Claim 1, wherein both of the two polyester resins are recycled polyester resins.

3. A woven or knitted fabric containing the polyester composite fiber according to Claim 1 or 2.

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