Sewing yarn

Abstract

To provide a novel sewing yarn that is readily alkali-soluble and has excellent durability to industrial washing.SOLUTION: A sewing yarn includes at least one of long fiber and short fiber formed of alkaline soluble resin. The alkali-soluble resin is a copolyester resin. When the total amount of all acid components constituting the polyester is 100 mol%, the sewing yarn includes 80 mol% or more of terephthalic acid and 0.5 to 5 mol% of an aromatic dicarboxylic acid having a metal sulfonate group. When the total amount of all glycol components constituting the polyester is 100 mol%, the sewing yarn includes 80 mol% or more of ethylene glycol and 0.1 to 1.0 mol% of a polyether compound.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sewing thread made of fibers formed from an alkali-soluble resin having a specific composition. [Background technology]

[0002] In recent years, efforts have been made to collect and recycle used clothing from the perspective of environmental protection. Because clothing is made up of many components, in order to recycle clothing, it is first necessary to separate the recyclable parts from the clothing. For this reason, clothing recycling begins with separating the constituent parts of the clothing, such as the body, sleeves, collar, cuffs, hem, buttons, and zippers, and separating them into recyclable and non-recyclable parts. The components can be easily separated by cutting the sewn parts or removing the sewing threads. However, both of these processes are usually done by hand, and there has been a demand for labor-saving and simplification of the work.

[0003] Therefore, when separating garments into their constituent parts, it is conceivable to reduce the labor required and simplify the work by making the sewing thread that sews the constituent parts together dissolvable. For example, Patent Document 1 discloses a technique for dissolving sewing thread made of water-soluble polyvinyl alcohol fiber in warm water, and Patent Document 2 discloses a technique for dissolving sewing thread made of alkali-soluble polyester fiber in a strong alkaline aqueous solution. If these sewing threads are used, garments can be separated into their constituent parts simply by immersing the collected garments in warm water or a strong alkaline aqueous solution, without the hassle of cutting the sewn portions or removing the sewing threads.

[0004] However, clothing must be washed after wearing. Regarding stain removal, uniforms such as nursing, medical, work, and sportswear tend to be more susceptible to stains than regular clothing, and stains tend to adhere more firmly to the garments. Therefore, regular home washing may not be sufficient to remove the stains. For this reason, industrial washing is typically performed in warm water using commercial detergents containing alkaline agents, and washing is typically done every time the garments are worn.

[0005] In the case of clothing that requires repeated industrial washing, if sewing thread that cannot withstand industrial washing is used, the strength of the sewing thread will decrease during washing, causing significant problems when wearing the garment. The sewing threads described in Patent Documents 1 and 2 are advantageous in terms of recycling clothing because they can be easily dissolved by simply immersing collected clothing in warm water or a strong alkaline aqueous solution. However, these sewing threads do not have durability to industrial washing. Therefore, there is a problem in that sewing threads that do not have industrial washing resistance cannot be used for clothing that undergoes industrial washing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 8-81811 [Patent Document 2] Japanese Patent Application Publication No. 7-216615 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention is intended to solve the above problems, and has as its technical object the provision of a novel sewing thread which is readily soluble in alkali and at the same time has excellent durability against industrial washing. [Means for solving the problem]

[0008] The present inventors have discovered that the above problems can be solved by producing a sewing thread using fibers made of a copolymer polyester resin in which the acid component contains a specific amount of an aromatic dicarboxylic acid having a metal sulfonate group and the glycol component contains a specific amount of a polyether compound, and have arrived at this invention based on this discovery.

[0009] That is, the present invention is summarized as follows (1) to (3). (1) A sewing thread comprising at least one of long fibers or short fibers formed from an alkali-soluble resin, wherein the alkali-soluble resin is a copolymer polyester resin, and wherein, when the total amount of all acid components constituting the polyester is taken as 100 mol %, the sewing thread contains 80 mol % or more of terephthalic acid and 0.5 to 5 mol % of an aromatic dicarboxylic acid having a metal sulfonate group, and when the total amount of all glycol components constituting the polyester is taken as 100 mol %, the sewing thread contains 80 mol % or more of ethylene glycol and 0.1 to 1.0 mol % of a polyether compound. (2) The sewing thread according to (1), further comprising 1.0 to 10.0 mol % of diethylene glycol when the total glycol component content is taken as 100 mol %. (3) A sewing thread according to (1), which has a strength retention rate of 70% or more after 50 industrial washings and a weight loss rate of 50% or more when subjected to an alkaline weight loss treatment using an alkaline aqueous solution of 10 g / L at 100°C for 30 minutes. [Effects of the Invention]

[0010] The sewing thread of the present invention is easily soluble in a strong alkaline aqueous solution and has sufficient durability even after repeated industrial washing. Therefore, when used in, for example, uniform clothing that requires industrial washing after each wear, the strength of the sewing thread is unlikely to decrease during washing, making it possible to use it for a long period of time. Furthermore, when recycling the used garment, the garment can be easily separated into its constituent parts simply by immersing it in a strong alkaline aqueous solution, which is advantageous in terms of recycling the garment. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below.

[0012] The present invention relates to a sewing thread containing at least one of continuous fibers or staple fibers formed from an alkali-soluble resin, and a copolymer polyester resin is used as the alkali-soluble resin. Generally, sewing threads made from polyester fibers formed from polyester resins (polyester sewing threads) are considered to have a superior luster compared to sewing threads made from other fibers, and to produce a better appearance in the seams. The sewing thread of the present invention not only has the characteristics of conventional sewing threads made from alkali-soluble resins, particularly polyester sewing threads, but also exhibits the effects of the present invention described above.

[0013] The copolymer polyester resin contains 80 mol % or more of terephthalic acid, assuming the total amount of all acid components constituting the polyester to be 100 mol %. If the terephthalic acid content is less than 80 mol %, the crystallinity of the resin decreases, resulting in a decrease in fiber strength, making it impossible to obtain a sewing thread strong enough for use. On the other hand, there are no particular restrictions on the upper limit of the terephthalic acid content, but it is preferable to set the upper limit at 97.5 mol %. If the content exceeds 97.5 mol %, the content of aromatic dicarboxylic acids having metal sulfonate groups and aliphatic dicarboxylic acids having 5 to 10 carbon atoms, which will be described later, will decrease, making it difficult to impart alkali solubility, and as a result, the sewing thread will be less likely to dissolve even when clothing is immersed in a strong alkaline aqueous solution, which is undesirable.

[0014] Furthermore, the acid component constituting the copolymerized polyester resin preferably contains 0.5 to 5 mol % of an aromatic dicarboxylic acid having a metal sulfonate group as a copolymerization component, with 0.8 to 3 mol % being preferred. If the content (copolymerization amount) is less than 0.5 mol %, the resin becomes highly crystalline, making it difficult to impart alkali solubility to the fiber. On the other hand, if the content exceeds 5 mol %, the resistance to alkaline aqueous solutions decreases, making it difficult to obtain a sewing thread that can withstand industrial washing. Furthermore, the heat resistance of the fiber decreases, and when the sewing thread is used as a sewing thread, frictional heat during sewing makes the sewing thread more susceptible to thread breakage and skipped stitches.

[0015] Examples of aromatic dicarboxylic acids having a metal sulfonate group include 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 5-lithium sulfoisophthalic acid, sodium sulfonaphthalenedicarboxylic acid, sodium sulfophenyldicarboxylic acid, and 5-sodium sulfoterephthalic acid, and two or more of these can be used in combination or as derivatives thereof. In the present invention, 5-sodium sulfoisophthalic acid is preferred from the viewpoints of operability and cost during melt spinning.

[0016] Furthermore, the copolymer polyester resin may contain an acid component other than terephthalic acid and aromatic dicarboxylic acid having a metal sulfonate group, as long as the effects of the present invention are not impaired. Specific examples include isophthalic acid, phthalic acid, phthalic anhydride, naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, dodecanedioic acid, trimellitic anhydride, trimellitic acid, pyromellitic acid, adipic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, and dimer acid. In the present invention, two or more of these may be used in combination, and derivatives of these may also be used.

[0017] The glycol component, which is the other component constituting the polyester, contains 80 mol % or more of ethylene glycol and 0.1 to 1.0 mol % of a polyether compound, when the total amount of all glycol components constituting the polyester is 100 mol %. The ethylene glycol content is preferably 85 mol% or more, and more preferably 90 mol% or more. If the ethylene glycol content is less than 80 mol%, the heat resistance of the fiber tends to decrease, and as a result, when used as a sewing thread, thread breakage and skipped stitches are likely to occur due to frictional heat during sewing, which is undesirable. On the other hand, the upper limit of the ethylene glycol content is not particularly limited, but it is preferable to set the upper limit at 99 mol%. If it exceeds 99 mol%, the content of the polyether compound will be reduced, making it difficult to impart alkali solubility, and as a result, the sewing thread will not easily dissolve even when the garment is immersed in a strong alkaline aqueous solution, which is undesirable.

[0018] The content of the polyether compound is 0.1 to 1.0 mol%, preferably 0.15 to 0.6 mol% as a copolymerization component, and particularly preferably 0.2 to 0.5 mol%. If the content (copolymerization amount) is less than 0.1 mol%, it becomes difficult to impart alkali solubility to the fiber. On the other hand, if it exceeds 1.0 mol%, the resistance to alkaline aqueous solutions decreases, making it difficult to obtain a sewing thread that can withstand industrial washing.

[0019] Examples of the polyether compound in the present invention include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and copolymers of ethylene oxide and propylene oxide, with polyethylene glycol and polytetramethylene glycol being preferred.

[0020] The number average molecular weight of the polyether compound is preferably 1000 to 15000. If the number average molecular weight of the polyether compound is less than 1000, the alkali solubility of the resulting fiber tends to decrease. On the other hand, if the number average molecular weight of the polyether compound exceeds 15000, the thermal stability of the polyester resin is impaired, and frequent yarn breakage tends to occur during spinning.

[0021] Furthermore, the glycol component of the copolymerized polyester resin preferably contains 1.0 to 10.0 mol %, more preferably 2.0 to 7.0 mol %, and even more preferably 2.5 to 5.5 mol % of diethylene glycol. When a large amount of diethylene glycol is contained, the resin generally tends to become brittle. However, in the present invention, by containing the specific amount of the polyether compound and also containing diethylene glycol in the specific range, the strength of the sewing thread is maintained while the thread is made more susceptible to alkali elution, making the sewing thread suitable for recycling. Diethylene glycol may be added when the copolymerized polyester resin is produced, or it may be contained as a by-product that may be generated during production.

[0022] Furthermore, the copolymer polyester resin may contain glycol components other than ethylene glycol, polyether compounds, and diethylene glycol, as long as the effects of the present invention are not impaired. Specifically, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexamethylenediol, 1,4-cyclohexanedimethanol, dimer diol, ethylene oxide adducts of bisphenol A or bisphenol S, and the like can be used. In the present invention, two or more of these may be used in combination, and derivatives thereof can also be used. Furthermore, glycol components other than ethylene glycol, polyether compounds, and diethylene glycol may be contained as by-products that may be generated during the production of the copolymer polyester resin.

[0023] The copolymer polyester resin may be obtained by material recycling, in which a polyester resin that has been used once is reused, or may be obtained by chemical recycling.

[0024] The sewing thread of the present invention contains at least one of long fibers and short fibers formed from the alkali-soluble resin as described above. The sewing thread of the present invention may be made of only long fibers, only short fibers, or both.

[0025] In particular, the long fibers or short fibers formed from the alkali-soluble resin as described above preferably contain 90% by mass or more of the alkali-soluble resin, and more preferably are made solely of the alkali-soluble resin. In other words, the long fibers or short fibers formed from the alkali-soluble resin preferably consist solely of the alkali-soluble resin, but may also be composite fibers containing other resins as long as the effects of the present invention are not impaired. Examples of the form of the composite fiber include a side-by-side type, a core-sheath type, and an island-in-the-sea type.

[0026] The sewing thread of the present invention preferably contains 50% by mass or more of long fibers or short fibers formed from the above-mentioned copolymer polyester resin, more preferably 70% by mass or more, even more preferably 90% by mass or more, and most preferably 100% by mass.

[0027] The content of the copolymer polyester resin contained in the sewing thread is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and most preferably 100% by mass.

[0028] The sewing thread of the present invention may contain other fibers in addition to the long fibers or short fibers formed from alkali-soluble resin. Any other fibers may be used as long as they do not impair the effects of the present invention, and specific examples include polyethylene terephthalate fibers, nylon fibers, acrylic fibers, and cellulose fibers. The other fibers may be in the form of either long fibers or short fibers.

[0029] The sewing thread of the present invention may be in the form of a filament yarn, a spun yarn, or a long-short composite yarn containing at least one of long fibers or short fibers formed from the alkali-soluble resin, but is preferably in the form of a filament yarn or a spun yarn from a practical standpoint. In this case, it may be a decorative yarn depending on the purpose, or may be a yarn dyed with a single color or a composite of multiple dyed yarns to give a mottled look.

[0030] The thickness of the sewing thread of the present invention may be set arbitrarily depending on the purpose, and is preferably 20 to 1500 dtex for filament yarns, and 4 to 200 count (British cotton count) for spun yarns or long and short composite yarns.

[0031] Furthermore, the sewing thread of the present invention may be either a non-twisted thread or a twisted thread. Since the strength of a thread generally increases when the thread is twisted, a twisted thread is preferred from the viewpoint of strength. On the other hand, a faster rate of alkali reduction is preferred in order to efficiently separate a garment into its constituent parts, and the lower the twist, the faster the rate of alkali reduction. Therefore, a non-twisted thread is preferred from the viewpoint of alkali solubility. The choice of non-twisted or twisted thread can be made depending on the intended use of the sewing thread.

[0032] Furthermore, the sewing thread may consist of only one thread, but from the viewpoint of increasing the strength of the sewing thread, it is preferable to combine multiple threads. Specifically, various types can be selected depending on the purpose, such as preparing multiple threads and simply paralleling them, or paralleling them and twisting them. The thread prepared in this case may be a non-twisted thread, but from the viewpoint of increasing strength, it is preferable to use a twisted thread. In addition, multiple threads that have been twisted while paralleling them may be prepared, and these may be further twisted.

[0033] When the sewing thread of the present invention is a filament yarn, the filament yarn may be in the form of raw silk, false-twisted yarn, or mixed yarn. In the case of mixed yarn, interlaced mixed yarn, Taslan textured yarn, etc. may be used. Also, it may be a false-twisted mixed yarn which has been given false twist and mixed yarn.

[0034] When the sewing thread is in the form of a non-twisted yarn, if the sewing thread is made from only one filament yarn, the spun filament yarn may be used as the sewing thread as is, or the false-twisted or blended filament yarn may be used as the sewing thread as is. In this case, the thickness of the filament yarn is preferably 20 to 1500 dtex in either form, as described above. Furthermore, when doubling the filament yarn to make the sewing thread, in either form, a plurality of filament yarns, preferably 2 to 5 filaments, each having a thickness of about 20 to 200 dtex, are prepared and then pulled together using a winder or the like.

[0035] On the other hand, when the sewing thread is in the form of a twisted yarn, it may be made of only one filament yarn. In this case, the twist direction is preferably the Z direction in either form, and the twist number is also preferably about 100 to 1800 T / m. In the case of doubling, when only the first twist is given, each filament yarn is first twisted in either form, and then they are pulled together using a winder, etc. In this case, the thickness of each filament yarn is preferably 20 to 200 dtex, and the twist direction is preferably the Z direction.

[0036] When only the second twist is imparted, in either case, multiple untwisted filament yarns, preferably about 2 to 5, can be simultaneously fed to a ring twister and twisted while being pulled together, or multiple untwisted filament yarns can be combined in a winder and then fed to a double twister where they can be twisted. In this case, the thickness of each filament yarn is preferably 20 to 200 dtex, the twist direction is preferably Z-direction, and the twist rate is preferably about 100 to 1800 T / m.

[0037] Furthermore, when applying a final twist and a first twist, a plurality of untwisted filament yarns, preferably having a thickness of about 20 to 200 dtex, are prepared, each of which is first twisted in the S direction at about 100 to 1500 T / m, and then a final twist in the Z direction at about 0.5 to 0.9 times the first twist. Final twisting is preferably performed using a ring twisting machine or the like. When applying final twists, first twists, and intermediate twists, for example, a plurality of filament yarns, preferably 2 to 5, each of which has a first twist in the Z direction and a medium twist in the S direction, are prepared, and these are then aligned and final twisted in the Z direction at about 100 to 1000 T / m. This results in a sewing thread with excellent sewability.

[0038] Next, when the sewing thread of the present invention is a spun yarn, any type of spun yarn can be used, such as ring spun yarn, open-end spun yarn, or bundled spun yarn, and it may have a core-sheath structure such as a multi-layered yarn, or may be fluff-bound such as a compact spun yarn.

[0039] In the case of spun yarn, the sewing thread may be made of only one spun yarn, and in this case, the thickness is preferably 4 to 200 count (British cotton count) as described above. The twist direction is preferably Z direction, and the twist number is preferably about 100 to 2000 T / m.

[0040] When doubling spun yarns to make sewing threads, if only first twisting is required, then it is sufficient to prepare multiple strands of spun yarn, preferably 2 to 5 strands, each having a thickness of 10 to 60 (British cotton count) and a twist of about 100 to 2000 T / m in the Z direction, and then align them using a winder or the like.

[0041] When imparting final twist and primary twist, it is preferable to prepare multiple spun yarns with a count of 10 to 60 (British cotton count) and a primary twist of about 100 to 2000 T / m in the S direction, and then impart a final twist of about 0.5 to 0.9 times the primary twist in the Z direction. Final twisting is preferably performed using a ring twisting machine as described above.

[0042] Furthermore, when applying a final twist, a first twist and a medium twist, multiple spun yarns, preferably 2 to 5 yarns, each having a first twist in the Z direction and a medium twist in the S direction, are prepared, and these are aligned and final twisted in the Z direction to obtain the desired sewing thread.

[0043] When the sewing thread of the present invention is a long and short composite thread, it is possible to use, for example, a thread obtained by simultaneously spinning a filament yarn in the core and a staple roving in the sheath. In the case of a long-short composite yarn, as with a filament yarn and a spun yarn, the sewing thread may be made from only one yarn, or may be made by doubling up multiple yarns. When a long-short composite yarn is used to make a sewing thread, the thickness, number of twists, etc. may basically be the same as those of the above-mentioned spun yarn.

[0044] The sewing thread of the present invention is both highly alkali-soluble and resistant to industrial washing. The term "easily soluble in alkali" refers to the ability to be easily dissolved in a strong alkaline aqueous solution, and it is preferable that the sewing thread of the present invention has a weight loss rate that satisfies a specific range when subjected to an alkaline weight loss treatment for 30 minutes using an alkaline aqueous solution with a concentration of 10 g / L and at 100° C. Specifically, the alkaline aqueous solution in the present invention is sodium hydroxide.

[0045] The weight loss rate of the sewing thread of the present invention is preferably 50% or more, next more preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, and most preferably 90% or more.

[0046] When the weight loss rate reaches 50% or more, the sewing threads become easily broken with even a small amount of force. This greatly simplifies the process of separating garments into their constituent parts during recycling. Furthermore, when the strength retention rate drops below 25% after 30 minutes of alkaline weight loss treatment using an alkaline solution with a concentration of 10g / L at 100°C, the threads tend to break even more easily.

[0047] The alkaline weight reduction treatment conditions employed in this invention (treatment in an alkaline aqueous solution at 100°C for 30 minutes, with a concentration of 10 g / L) are designed to reduce environmental impact and facilitate subsequent recycling. In other words, it is not enough for sewing threads to simply be alkali-soluble; the desired alkali solubility must be achieved while minimizing environmental impact and minimizing damage to garment components caused by the alkaline aqueous solution. For example, increasing the concentration of the alkaline aqueous solution promotes alkali solubility, but this increases the amount of neutralizing agent required in wastewater treatment, thereby increasing the environmental impact. In addition, if the garment components contain, for example, polyester fibers, the fibers will be eluted, resulting in a reduction in the total amount of recyclable materials. Therefore, it is necessary to achieve the desired alkali solubility under the moderate conditions of 30 minutes in an alkaline aqueous solution at 10 g / L and 100°C.

[0048] On the other hand, in terms of industrial washing resistance, the tenacity retention after 50 washes is preferably 70% or more, more preferably 75% or more, and even more preferably 80% or more. This makes it possible to apply the material to a wide range of textile products, not only for general clothing but also for uniforms that require industrial washing after each wear, since the strength of the sewing thread is unlikely to decrease during washing. Industrial washing is applied to washing uniforms and other clothing, and is carried out under stricter conditions than home washing, such as using a high-temperature alkaline bath.

[0049] The conditions for industrial washing in the present invention are as follows: the steps shown in Table 1 are carried out according to the conditions for each step (temperature, amount of water, time, detergent, amount of detergent added). The detergent used is "BioHarvest (product name)" manufactured by Kao Professional Services.

[0050] First, in pre-wash 1, clothes are washed at room temperature, and then the water temperature is raised without draining, and pre-wash 2 is washed in warm water at 35°C. For the wash solution, adding water and detergent as shown in Table 1 will create an alkaline bath with a pH of approximately 10.0±1.0. Next, the water is replaced and the clothes are washed in the main wash. The bath ratio (detergent:water) is 1:30 for both pre-wash and main wash. Next, water is added while maintaining the water level until the water temperature reaches 40°C, and once this point is reached, the clothes are allowed to cool down for 5 minutes. The water is then replaced and soak rinse 1 is performed, and then soak rinses are performed in rinses 2 to 5, with the water being replaced each time. The clothes are then dehydrated and dried.

[0051] [Table 1]

[0052] In the present invention, the strength retention rate after 50 industrial washes is measured by evaluating the strength retention rate after repeating the washing procedure shown in Table 1 50 times, but repeating the washing procedure 50 times is a rather cumbersome task. Therefore, in the present invention, the strength retention rate of sewing thread after 50 industrial washes is measured by assuming that repeating the steps shown in Table 2 five times achieves the same washing effect as repeating the washing procedure shown in Table 1 50 times, and therefore.

[0053] [Table 2]

[0054] As described above, the present invention provides a sewing thread that can be easily dissolved in a strong alkaline aqueous solution while being sufficiently durable against repeated industrial washing. This makes it possible to apply the thread to not only general clothing but also uniform clothing that requires industrial washing after each wear. Any type of sewing thread can be used, including machine sewing thread and hand sewing thread.

[0055] Furthermore, from the viewpoint of preventing puckering when subjected to the heat of an iron after sewing, the sewing thread of the present invention preferably has a dry heat shrinkage of 5% or less when dry heat treated for 10 minutes at 160°C and a hot water shrinkage of 3% or less when hot water treated for 20 minutes at 100°C. The methods for measuring the dry heat shrinkage and hot water shrinkage will be described in detail in the Examples.

[0056] Polyester resin is preferably used for the sewing thread of the present invention, and the use of polyester resin provides the excellent luster inherent to polyester resin, allowing for a beautifully finished seam. Furthermore, the polyester sewing thread also exhibits heat resistance. As a result, the thread can withstand not only the frictional heat that occurs when used as a sewing thread due to the rotation of a sewing machine, but also the heat that occurs during autoclave treatment (high-pressure steam sterilization) that is carried out in conjunction with industrial washing of medical clothing and the like.

[0057] Next, a method for producing the sewing thread of the present invention will be described. The alkali-soluble resin described above can be melt-spun by known means to form a multifilament or staple fiber yarn, and the yarn can be processed into the form of a filament yarn, spun yarn, or long and short composite yarn as described above to form the desired sewing thread.

[0058] Here, we will explain a method for producing a sewing thread using a copolymer polyester resin containing the above-mentioned specific components to obtain a multifilament. First, the copolymer polyester resin is produced through a polymerization process, and the resulting copolymer polyester resin is then chipped. The chips are then dried and melt-spun to obtain a multifilament. Melt spinning conditions that can be used include a spinning temperature of 260-300°C, a spinning speed of 1000-2000 m / min, a drawing temperature of 50-85°C, a heat-setting temperature of 110-160°C, and a drawing speed of 300-1000 m / min. The draw ratio can be approximately 0.25-0.60 times the maximum draw ratio of the undrawn yarn. The spinning and drawing conditions are not limited to those described above. Examples of suitable methods include the POY method, in which high-speed spinning at 2000 m / min or higher is performed and the yarn is wound up as a semi-undrawn yarn, and the spin-draw method, in which high-speed spinning at 2000 m / min or higher is performed and the yarn is subsequently drawn without being wound up. Thereafter, the resulting multifilament is twisted in the Z direction at 300 to 800 T / M using a double twister, and the twist is set at 50 to 100°C for about 30 minutes to obtain the sewing thread of the present invention. [Example]

[0059] The present invention will be described in more detail below with reference to examples. The characteristic values ​​of the sewing thread were measured by the following methods.

[0060] 1. Strength retention rate after 50 industrial washes First, the obtained sewing thread was tubularly knitted to prepare a 200 g washing sample. Then, the washing sample and a guide fabric (knitted fabric made of polyester fiber, basis weight: 300 g / m 22,400 g of the sewing thread was placed in an industrial washing machine, and the process shown in Table 2 was repeated five times under the conditions shown in Table 2. Next, the sewing thread before tubular knitting and the sewing thread carefully removed from the washed sample after washing were prepared, and the tensile strength of the sewing thread was measured in accordance with JIS L1013 8.5.1 if the sewing thread was in the form of filament yarn, or in accordance with JIS L1095 9.5.1 if the sewing thread was in the form of spun yarn. The strength retention was then calculated using the following formula. Strength retention rate (%) = (tensile strength after washing (mN) / tensile strength before tubular knitting (mN)) x 100

[0061] 2. Weight loss rate and strength retention rate when treated with alkaline weight loss First, the resulting sewing thread was tubularly knitted to form a weight loss sample, which was then weighed. Next, the weight loss sample was sealed in a cylindrical container together with a 10 g / L sodium hydroxide aqueous solution in a bath ratio of 1:50 (weight loss sample:sodium hydroxide aqueous solution). The container was then immersed in a 100°C oil bath with its longitudinal direction horizontal, so that approximately half of the container was submerged. It was then rotated 20 times in one direction at a speed of 1 rotation per second, and then inverted the same number of times at the same speed. This process was repeated for 30 minutes, after which the cylindrical container was lifted from the oil bath, and the sample was removed from the container. The sample was then carefully washed with water, placed on a flat surface, and dried at room temperature. The dried weight loss sample was then weighed, and the weight loss rate was calculated using the following formula: Weight loss rate (%) = (mass before alkali reduction (g) - mass after alkali reduction (g)) / mass before alkali reduction (g) × 100

[0062] Furthermore, the sewing thread before tubular knitting and the sewing thread carefully removed from the weight loss sample after weight loss were prepared, and thereafter the strength retention rate was calculated in the same manner as in "1. Strength retention rate after 50 industrial washes" above. Strength retention rate (%) = (tensile strength after weight loss (mN) / tensile strength before tubular knitting (mN)) x 100

[0063] 3. Copolymer component content Measurements were carried out using a nuclear magnetic resonance spectrometer "ECA500 (trade name)" (room temperature probe) manufactured by JEOL Ltd. 15 mg of suture and 0.7 mL of trifluoroacetic acid were placed in a test tube, and the measurement solution was prepared by ultrasonic treatment and stirring at room temperature for 30 minutes. 1 H, Measured at a measurement frequency of 500 MHZ.

[0064] Example 1 We prepared a copolymer polyester resin chip whose main repeating unit is ethylene terephthalate, containing 98.1 mol% of terephthalic acid (TPA) and 1.9 mol% of 5-sodium sulfoisophthalic acid (SIPM) relative to 100 mol% of the acid components of the entire polyester, and containing 96.8 mol% of ethylene glycol (EG), 2.9 mol% of diethylene glycol (DEG), and 0.3 mol% of polyethylene glycol (PEG) with a number average molecular weight of 6000 relative to 100 mol% of the glycol components of the entire polyester.

[0065] The chips were then dried and placed in a spinning apparatus equipped with a spinneret. The chips were melt-spun through a 36-hole round cross-section spinneret at a spinning temperature of 280°C and a spinning speed of 1100 m / min to obtain an undrawn yarn, which was then drawn at a drawing speed of 361 m / min, a drawing temperature of 55°C, a heat treatment temperature of 130°C, and a maximum draw ratio of 0.42 to obtain a polyester fiber yarn of 56 dtex and 36 f. Thereafter, the polyester fiber yarn was twisted in the Z direction at 500 T / M using a double twister, and the twist was set at 70°C for 30 minutes to obtain a sewing thread of the present invention.

[0066] Example 2 We prepared a copolymer polyester resin chip whose main repeating unit is ethylene terephthalate, containing 98.2 mol% of terephthalic acid (TPA) and 1.8 mol% of 5-sodium sulfoisophthalic acid (SIPM) relative to 100 mol% of the acid components of the entire polyester, and containing 94.4 mol% of ethylene glycol (EG), 5.2 mol% of diethylene glycol (DEG), and 0.4 mol% of polyethylene glycol (PEG) with a number average molecular weight of 6000 relative to 100 mol% of the glycol components of the entire polyester.

[0067] The chips were then dried and placed in a spinning apparatus equipped with a spinneret. The chips were melt-spun from a 36-hole round cross-section spinneret at a spinning temperature of 280°C and a spinning speed of 1100 m / min to obtain an undrawn yarn, which was then drawn at a drawing speed of 361 m / min, a drawing temperature of 60°C, a heat treatment temperature of 130°C, and a maximum draw ratio of 0.40 to obtain a polyester fiber yarn of 56 dtex and 36 f. Thereafter, the polyester fiber yarn was twisted in the Z direction at 500 T / M using a double twister, and the twist was set at 70°C for 30 minutes to obtain a sewing thread of the present invention.

[0068] Example 3 We prepared a copolymer polyester resin chip whose main repeating unit is ethylene terephthalate, containing 98.2 mol% of terephthalic acid (TPA) and 1.8 mol% of 5-sodium sulfoisophthalic acid (SIPM) relative to 100 mol% of the acid components of the entire polyester, and containing 96.6 mol% of ethylene glycol (EG), 3.0 mol% of diethylene glycol (DEG), and 0.4 mol% of polyethylene glycol (PEG) with a number average molecular weight of 6000 relative to 100 mol% of the glycol components of the entire polyester.

[0069] The chips were then dried and placed in a spinning apparatus equipped with a spinneret. The chips were melt-spun from a 36-hole round cross-section spinneret at a spinning temperature of 280°C and a spinning speed of 1100 m / min to obtain an undrawn yarn, which was then drawn at a drawing speed of 361 m / min, a drawing temperature of 55°C, a heat treatment temperature of 130°C, and a maximum draw ratio of 0.40 to obtain a 56 dtex 36f polyester fiber yarn. Thereafter, the polyester fiber yarn was twisted in the Z direction at 500 T / M using a double twister, and the twist was set at 70°C for 30 minutes to obtain a sewing thread of the present invention.

[0070] Comparative Example 1 When the total amount of all acid components constituting the polyester is taken as 100 mol %, terephthalic acid is taken as 100 mol %, and when the total amount of all glycol components constituting the polyester is taken as 100 mol %, polyester resin chips containing 100 mol % ethylene glycol were prepared. Using the above chip, a polyester fiber yarn was obtained in the same manner as in Example 1, except that the spinning speed was set to 1200 m / min and the thickness of the polyester fiber yarn was set to 84 dtex 36 f. Thereafter, the polyester fiber yarn was twisted in the Z direction at 400 T / M using a double twister, and the twist was set at 70°C for 30 minutes to obtain a sewing thread of the present invention.

[0071] Comparative Example 2 The 84 dtex 36 f polyester fiber yarn obtained in Comparative Example 1 was cut to 3.8 mm to form short fibers (synthetic cotton), which were then spun in a conventional manner to form a 50 count spun yarn with a first twist of 1050 T / M in the S direction. Subsequently, three of these spun yarns were ply-twisted to obtain a sewing yarn count of 50 having a second twist of 700 T / M in the Z direction.

[0072] The property values ​​of the sewing threads obtained in Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 3.

[0073] [Table 3]

[0074] As is clear from Table 3, the sewing threads obtained in Examples 1 to 3 had a high strength retention rate after 50 industrial washings, and when subjected to alkali weight loss treatment, the weight loss rate was 50% or more. On the other hand, the sewing threads obtained in Comparative Examples 1 and 2 had a low weight loss rate after alkali weight loss treatment and were not suitable for use in the recycling applications targeted by the present invention.

[0075] The sewability of the sewing threads was evaluated by sewing five layers of cotton plain weave fabric (warp count 30, warp density 78 threads / 2.54cm, weft density 72 threads / 2.54cm) using a lockstitch sewing machine (JUKI "DDL-5530N (trade name)") at a sewing speed of 4500 spm and a stitch pitch of 2mm. The sewing was performed in a straight line over a length of 1m, and the test was carried out five times for each sewing thread. As a result, no thread breakage or skipped stitches were observed in any of the sewing threads obtained in Examples 1 to 3, and the sewing properties were good.

Claims

1. A sewing thread comprising at least one of long fibers or short fibers formed from an alkali-soluble resin, wherein the alkali-soluble resin is a copolymer polyester resin, and wherein, when the total amount of all acid components constituting the polyester is taken as 100 mol %, the sewing thread contains 80 mol % or more of terephthalic acid and 0.5 to 5 mol % of an aromatic dicarboxylic acid having a metal sulfonate group, and when the total amount of all glycol components constituting the polyester is taken as 100 mol %, the sewing thread contains 80 mol % or more of ethylene glycol and 0.1 to 1.0 mol % of a polyether compound.

2. 2. The sewing thread according to claim 1, further comprising 1.0 to 10.0 mol % of diethylene glycol when the total glycol component content is taken as 100 mol %.

3. 2. The sewing thread according to claim 1, which has a strength retention rate of 70% or more after 50 industrial washings and a weight loss rate of 50% or more when subjected to an alkaline weight loss treatment using an alkaline aqueous solution of 10 g / L at 100°C for 30 minutes.

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