Recycled polyurethane elastic fiber, method for producing the same, fiber structure containing the recycled polyurethane elastic fiber, pleated member and sanitary material

Abstract

Provided are recycled polyurethane elastic fibers that can be used universally even as recycled products, a method for producing the same, a fiber structure containing the same, a pleated member, and a sanitary material. The present invention relates to recycled polyurethane elastic fibers, a method for producing the same, a fiber structure containing the same, a pleated member, and a sanitary material, wherein the recycled polyurethane elastic fibers are recycled polyurethane elastic fibers made of raw material polyurethane elastic fibers, have a reduced viscosity of 1.00 or more, and the total amount of mineral oil and silicone oil remaining in the recycled polyurethane elastic fibers after washing the recycled polyurethane elastic fibers with petroleum ether is 10% by weight or less relative to the weight of the washed fibers.

Description

Technical Field

[0001] The present invention relates to recycled polyurethane elastic fibers, a method for producing the same, a fiber structure, a pleated member and a sanitary material containing the recycled polyurethane elastic fibers. Background Art

[0002] Polyurethane fibers are used in a variety of products by mixing with other fibers due to their excellent elasticity. Examples include socks, swimsuits, clothes, diapers and other sanitary products. The demand for polyurethane fibers is increasing year by year, which also means an increase in the demand for polyols and isocyanates as raw materials and diamines and diols as chain extenders.

[0003] On the other hand, the depletion of oil resources and global warming have become serious problems in recent years, and efforts are being actively made to realize a sustainable society.

[0004] From the perspective of sustainability, production activities using biomass raw materials for the purpose of carbon neutrality are one of the major means of achieving this goal.

[0005] In addition, as life becomes more affluent, garbage and waste increase, and the shortage of disposal sites and treatment sites, environmental pollution, etc. have long been major problems. Therefore, efforts made on the following 3Rs, which refer to suppressing (reducing) the generation of waste, appropriately reusing (reusing) used products, etc., and finally recycling, can also become extremely effective means to achieve a sustainable society.

[0006] In this trend, the following Patent Document 1 has created a technology for producing 1,4-butanediol, which can be a raw material for polyol, from edible biomass raw materials, and proposed a polyurethane elastic fiber using polyols derived from this 1,4-butanediol. However, there are problems such as the very high cost of producing butanediol and the fact that biomass is edible rather than inedible, and it has not yet been widely adopted in society.

[0007] In addition, the following patent document 2 reports a method for recycling polyurethane elastic fibers themselves. However, when using this technology, the production method such as aging, pulverization, and moisture content management of the yarn is extremely carefully specified, and the energy required for the process cannot be ignored.

[0008] In addition, the following patent document 3 also reports a method of utilizing waste slurry (dope) generated during production. However, when using this method, diol, diisocyanate, amine, etc. need to be added again, which is the same as normal production. In addition, in either case, there are still questions about the stability and variation of the final physical properties.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application No. 2017-519121

[0012] Patent Document 2: China Publication Patent No. 106757490

[0013] Patent Document 3: China Publication Patent No. 108517580 Summary of the invention

[0014] Problem that the invention aims to solve

[0015] In view of the above-mentioned prior art, an object of the present invention is to provide a recycled polyurethane elastic fiber that can be generally used even as a recycled product, a method for producing the same, a fiber structure, a pleating member, and a sanitary material containing the recycled polyurethane elastic fiber.

[0016] Solutions for solving problems

[0017] Generally, polyurethane elastic fibers are fibers that are easy to adhere due to their viscoelasticity. In particular, in the inner layer of the winding body, adhesion will develop over time due to the pressure applied during winding. Therefore, when using the elastic fiber winding body, it will become poorly unwinded and cause broken ends. In order to improve this poor unwinding, in its spinning process, after applying the so-called oil agent, it is wound into a cheese shape to form a winding body (hereinafter also referred to as cheese yarn). In the case of making recycled polyurethane elastic fibers through a slurry solution in which these polyurethane elastic fibers are part of the raw materials, as long as no special treatment is performed, the oil agent contained in the raw materials, especially the silicone oil and mineral oil as the main components, will be directly brought into the recycled polyurethane elastic fibers and act as an internal oil additive inside the recycled polyurethane elastic fibers. However, the compatibility of the internal oil additive with the polyurethane urea polymer is low, and the larger the amount, the more it becomes the main reason for the reduction of physical properties. Furthermore, if it is other than a monofilament, the monofilaments will also separate from each other due to the reduction in adhesion. In addition, depending on the characteristics of the raw material polyurethane elastic fiber, the conditions during slurry preparation, etc., the reduced viscosity of the recycled polyurethane elastic fiber may decrease, which may cause a decrease in physical properties and a decrease in resistance to heat treatment during processing.

[0018] It is known that the physical properties, characteristics, ratio of hard segments, molecular weight, and other shapes of polyurethane elastic fibers vary greatly depending on the subtle differences in the ratio of the amount of polyol, isocyanate, and chain extender of the raw materials and the amount of heat. On the other hand, in order to recycle the polyurethane elastic fiber as a slurry raw material for dry and wet spinning, it is necessary to redissolve it in a solvent. At this time, if polyurethane elastic fibers with different shapes as described above are used, polyurethane elastic fibers with large molecular weight and hard segment ratios and polyurethane elastic fibers with more cross-linked structures may not be dissolved and remain. In the case of a large number of undissolved residues, even if they are filtered in the process, the filter will be immediately clogged, so the production efficiency is extremely poor and cannot be used for actual production. Although there are cases where it can be dissolved by heating operation, when high temperature is required, the side effect of molecular weight reduction occurs due to the breakage of polyurethane molecules, etc., which affects the performance and physical properties of the silk after spinning. On the contrary, polyurethane elastic fibers with too small molecular weight and hard segment ratio and polyurethane elastic fibers with less cross-linked structures are easy to dissolve, but they still cause the physical properties after spinning to decrease. For example, a 22 dtex polyurethane elastic fiber can be generally used if its physical properties are 25 cN or more at break strength and 550% or more at break elongation.

[0019] The present inventors conducted in-depth research and repeated experiments based on the above viewpoints, and unexpectedly found that recycled polyurethane elastic fibers with a certain amount of internal oil additives (total content of mineral oil and silicone oil) and relative concentrated viscosity have the same physical properties as those of conventional polyurethane elastic fibers spun from virgin polymers, thereby completing the present invention.

[0020] That is, the present invention is as follows.

[0021] [1] A recycled polyurethane elastic fiber, characterized in that it is a recycled polyurethane elastic fiber using a raw material polyurethane elastic fiber as a raw material, the recycled polyurethane elastic fiber has a concentrated viscosity of 1.00 or more, and the total amount of mineral oil and silicone oil remaining in the recycled polyurethane elastic fiber after washing the recycled polyurethane elastic fiber with petroleum ether is less than 10% by weight relative to the weight of the fiber after washing.

[0022] [2] The recycled polyurethane elastic fiber according to [1] above, wherein the total amount of mineral oil and silicone oil remaining in the fiber after washing with petroleum ether is 0.1% by weight or more relative to the weight of the fiber after washing.

[0023] [3] The method for producing recycled polyurethane elastic fibers according to the above-mentioned [1] or [2], wherein a slurry obtained by dissolving a raw material polyurethane elastic fiber in a solvent is used as a raw material of a spinning solution in the production of the above-mentioned recycled polyurethane elastic fiber, and as the raw material polyurethane elastic fiber, a polyurethane elastic fiber having a total content of mineral oil and silicone oil of not more than 20% by weight is used.

[0024] [4] The method according to [3] above, wherein the polyurethane elastic fiber having a total content of mineral oil and silicone oil of 12 wt % or more accounts for no more than 10 wt % of the total polyurethane elastic fiber used as the raw material.

[0025] [5] The method according to [3] or [4], wherein only polyurethane elastic fibers having a reduced viscosity of 1.00 or more and 4.20 or less are used as the raw material polyurethane elastic fibers.

[0026] [6] The method according to any one of [3] to [5], wherein the polyurethane elastic fiber used as the raw material has a reduced viscosity of 1.10 to 2.50 in an amount of 70% by weight or more of the total polyurethane elastic fiber used as the raw material.

[0027] [7] The method according to any one of [3] to [6], wherein the solvent for dissolving the raw material polyurethane elastic fiber is either DMF or DMAc.

[0028] [8] The method according to any one of [3] to [7], wherein the temperature at which the raw material polyurethane elastic fiber is dissolved in the solvent is 50° C. or higher and 100° C. or lower.

[0029] [9] The method according to any one of [3] to [8], wherein the spinning solution is a solution obtained by mixing a slurry obtained by dissolving the raw material polyurethane elastic fiber in a solvent and a newly prepared virgin polymer solution.

[0030]

[10] A fiber structure comprising the recycled polyurethane elastic fiber according to [1] or [2].

[0031]

[11] A pleated member comprising the recycled polyurethane elastic fiber according to [1] or [2].

[0032]

[12] A sanitary material comprising the pleated member according to

[11] .

[0033] Effects of the Invention

[0034] The recycled polyurethane elastic fiber of the present invention can be generally used as a recycled polyurethane elastic fiber, and thus can make a great contribution to 2R (reduction and recycling) by reusing non-standard yarns that would otherwise be discarded as raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a diagram for explaining the evaluation method of relaxation. DETAILED DESCRIPTION

[0036] Hereinafter, embodiments of the present invention will be described in detail.

[0037] The recycled polyurethane elastic fiber of the present embodiment is characterized in that it is a recycled polyurethane elastic fiber using raw material polyurethane elastic fiber as a raw material, the concentrated viscosity of the recycled polyurethane elastic fiber is greater than 1.00, and the total amount of mineral oil and silicone oil remaining in the recycled polyurethane elastic fiber after washing the recycled polyurethane elastic fiber with petroleum ether is less than 10 weight% relative to the weight of the fiber after washing.

[0038] If the total amount of mineral oil and silicone oil remaining in the recycled polyurethane elastic fiber after washing with petroleum ether is 10% by weight or less relative to the weight of the fiber after washing, the recycled polyurethane elastic fiber has physical properties that can be used as a general-purpose recycled polyurethane elastic fiber, and there is no separation between the monofilaments, so it can be used without problems. For the management of the amount of internal oil additives, for example, a method of managing the oil content of the raw material polyurethane elastic fiber; or a method of preparing a slurry (hereinafter also referred to as slurry, recycled slurry) obtained by dissolving the raw material polyurethane elastic fiber in a solvent and then leaving it to stand to remove the separated oil component, etc.

[0039] Furthermore, from the viewpoint of the release property, the total amount of the mineral oil and the silicone oil remaining in the fiber after washing with petroleum ether is preferably 0.1% by weight or more based on the weight of the fiber after washing.

[0040] The reduced viscosity of the recycled polyurethane elastic fiber of the present embodiment is 1.00 or more. The reduced viscosity is highly correlated with the molecular weight, and if it is 1.00 or more, it has no significant effect on the physical properties, and can fully withstand even the usual heating processing steps. On the other hand, the reduced viscosity of the recycled polyurethane elastic fiber is preferably 5.00 or less from the viewpoint of spinning stability.

[0041] The recycled polyurethane elastic fiber of the present embodiment can be produced by the following method: using a slurry obtained by dissolving a raw material polyurethane elastic fiber in a solvent as a raw material of a spinning solution in the production of the aforementioned recycled polyurethane elastic fiber, and using a polyurethane elastic fiber having a total content of mineral oil and silicone oil of 20% by weight or less as the raw material polyurethane elastic fiber.

[0042] The raw material polyurethane elastic fiber used in the manufacture of the recycled polyurethane elastic fiber of the present embodiment may contain an oil agent inside the fiber or attached to the fiber surface, either of which is acceptable, but the total content of mineral oil and silicone oil in the oil agent is preferably within a certain range. Specifically, as the raw material polyurethane elastic fiber, it is preferred to use only polyurethane elastic fibers whose content of mineral oil and silicone oil is 0% by weight or more and 20% by weight or less, from the perspective of managing the amount of oil brought into the raw material. The total content of mineral oil and silicone oil is more preferably 0% by weight or more and 17% by weight or less, and further preferably 0% by weight or more and 15% by weight or less. The total content of mineral oil and silicone oil contained in the recycled polyurethane elastic fiber can be adjusted by post-attachment as needed, so the raw material polyurethane elastic fiber does not necessarily have to contain mineral oil and silicone oil.

[0043] Furthermore, as the raw material polyurethane elastic fiber, it is preferred that the total content of mineral oil and silicone oil in the polyurethane elastic fiber is 12% by weight or more and is 10% by weight or less of the total polyurethane elastic fiber for the raw material. If the weight ratio of the polyurethane elastic fiber having a total content of mineral oil and silicone oil of 12% or more in the raw material polyurethane elastic fiber is within this range, it is easy to manage the total amount of mineral oil and silicone oil in the fiber to be 10% by weight or less relative to the weight after washing with petroleum ether in the recycled polyurethane elastic fiber. It is more preferred that the total content of mineral oil and silicone oil in the polyurethane elastic fiber is 10% by weight or less of the total polyurethane elastic fiber for the raw material, and it is further preferred that the total content of mineral oil and silicone oil in the polyurethane elastic fiber is 8% by weight or more and is 10% by weight or less of the total polyurethane elastic fiber for the raw material.

[0044] In the method for producing recycled polyurethane elastic fibers of the present embodiment, it is preferred to use only polyurethane elastic fibers having a reduced viscosity of 1.00 or more and 4.20 or less as the raw material polyurethane elastic fibers. If the reduced viscosity of the raw material polyurethane elastic fibers is 1.00 or more, the physical properties of the recycled polyurethane elastic fibers after spinning are not greatly affected, and the recycled polyurethane elastic fibers can fully withstand even a normal heating process. On the other hand, if the reduced viscosity of the raw material polyurethane elastic fibers is 4.20 or less, there is very little undissolved residue during slurry preparation, and even if there is undissolved residue, it can be easily removed by a filter in the process.

[0045] The reduced viscosity of the raw material polyurethane elastic fiber is more preferably 1.10 or more and 2.50 or less. Within this range, the variation in the physical properties of the obtained recycled polyurethane elastic fiber is suppressed, and the influence on the process is also extremely small. In addition, the weight ratio of the raw material polyurethane elastic fiber having a reduced viscosity of 1.10 or more and 2.50 or less is preferably 70% by weight or more, more preferably 100% by weight of the total raw material polyurethane elastic fiber.

[0046] In dry spinning or wet spinning, when polyurethane elastic fibers are used as recycled raw materials, it is preferred to prepare a slurry dissolved in any one of N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc) as amide solvents, and use it as the raw material of the spinning solution. In this case, the dissolution efficiency is improved by cutting the raw material polyurethane elastic fibers into appropriate lengths before dissolving. As a solvent, DMAc is more preferred from the viewpoint of ease of use.

[0047] The dissolution temperature when preparing the slurry of the raw material polyurethane elastic fiber is not particularly limited as long as the reduced viscosity of the obtained recycled polyurethane elastic fiber is 1.00 or more, but is preferably 50° C. or more for effective dissolution, and is preferably 100° C. or less from the viewpoint of not reducing the molecular weight and the physical properties of the yarn after spinning. The dissolution temperature is more preferably 60° C. or more and 90° C. or less.

[0048] The slurry prepared from the raw polyurethane elastic fiber can be used directly as a spinning solution by appropriately adjusting the concentration. Alternatively, the slurry prepared from the raw polyurethane elastic fiber can be mixed with a newly prepared spinning solution (original spinning solution) that does not use the raw polyurethane elastic fiber as a raw material, and the mixing ratio is not particularly limited.

[0049] The raw material polyurethane elastic fiber used in the method for producing the recycled polyurethane elastic fiber of the present embodiment and the polyurethane polymer supplied to the original spinning solution can be obtained by a known method of reacting a polymer diol with a diisocyanate to obtain a prepolymer, and reacting the prepolymer with a compound containing active hydrogen. Examples of the polymer diol include polyester diol, polycarbonate diol, polyether diol, etc., preferably polyether diol, more preferably polyalkylene ether diol in which one or more linear or branched alkylene groups having 2 to 10 carbon atoms are ether-bonded.

[0050] The polyalkylene ether glycol is a single or copolymer polyalkylene ether glycol in which one or more linear or branched alkylene groups having 2 to 10 carbon atoms are ether-bonded and the number average molecular weight is 500 to 6000. The copolymer polyalkylene ether glycol is a copolymer polyalkylene ether glycol in which the alkylene groups are ether-bonded in a block or random manner and the number average molecular weight is 500 to 6000.

[0051] As diisocyanates, known aliphatic, alicyclic or aromatic organic diisocyanates having two isocyanate groups in the molecule can be listed, and they can be used alone or in combination. Specifically, organic diisocyanates such as 4,4'-diphenylmethane diisocyanate (MDI), 2,4- or 2,6-toluene diisocyanate, p-phenylene diisocyanate, 1,5-naphthalene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate can be listed, preferably 4,4'-diphenylmethane diisocyanate. In addition, as organic diisocyanates, compounds having blocked isocyanate groups converted into free isocyanate groups can also be used.

[0052] As the active hydrogen-containing compound that reacts with an isocyanate group used in the raw material polyurethane elastic fiber and the polyurethane polymer supplied to the original spinning solution used in the method for producing the recycled polyurethane elastic fiber of the present embodiment, a chain extender commonly used in polyurethane polymers, that is, a low molecular weight compound having a molecular weight of 500 or less and containing at least two hydrogen atoms that can react with isocyanate, can be used. Specific examples thereof include diamines such as ethylenediamine, propylenediamine, benzalkonium diamine, meta-xylylenediamine, 1,3-diaminocyclohexane, isophoronediamine, hydrazine, 4,4'-diaminodiphenylmethane, dihydrazide, and piperazine, diamine compounds disclosed in Japanese Patent Application Laid-Open No. 5-155841, and diols such as ethylenediamine, propylenediol, and 1,4-butanediol. Preferably, ethylenediamine, 1,2-propylenediamine, and diamine compounds disclosed in Japanese Patent Application Laid-Open No. 5-155841 are used. These compounds may be used alone or in combination of two or more. In addition, they may be used in combination with a compound containing one active hydrogen that can react with isocyanate, as required.

[0053] As a method for producing a polyurethane polymer using a diisocyanate, a high molecular weight diol, and an active hydrogen-containing compound, a known urethanization reaction technique can be adopted.

[0054] The polyurethane polymer thus obtained may further contain known organic or inorganic compound heat stabilizers, antioxidants, ultraviolet light inhibitors, yellowing inhibitors, thermal discoloration inhibitors, chlorine-containing disinfectants for swimming pools, colorants, rosin, pigments, carbon black, acrylic resins, metal soaps, fillers, etc., which are useful for the polyurethane polymer. The polyurethane polymer thus obtained may be formed into fibers by known dry spinning, wet spinning, etc. to produce polyurethane elastic fibers.

[0055] The polyurethane elastic fibers thus obtained may be given oils such as polydimethylsiloxane, polyester-modified silicone, polyether-modified silicone, amino-modified silicone, mineral oil, mineral fine particles such as silica, colloidal alumina, talc, etc., higher fatty acid metal salt powders such as magnesium stearate, calcium stearate, etc., higher aliphatic carboxylic acids, higher aliphatic alcohols, paraffins, polyethylene, etc., which are solid waxes at room temperature, alone or in any combination as needed.

[0056] The fiber structure of the present embodiment only needs to contain the recycled polyurethane elastic fiber of the present embodiment as one of its constituent components, and examples thereof include fabrics (woven fabrics, knitted fabrics, nonwoven fabrics, fleece fabrics, etc.), rope-like materials (impregnated cords, ropes, tapes, fishnets, braided ropes, etc.).

[0057] There is no particular limitation on the raw material setting when the recycled polyurethane elastic fiber of this embodiment is combined with other raw materials to form a fiber structure, and examples thereof include cellulose fibers, protein fibers, polyolefin fibers, polyacrylic fibers, polyamide, polyester, and polyurethane elastic fibers.

[0058] The recycled polyurethane elastic fiber of this embodiment, or the fiber structure containing the fiber can be used for tights, panty stockings, undershirts, suspenders, cuffs, corsets, surgical bandages, woven fabrics and knitted swimsuits, and is particularly suitable for underwear, outerwear, leg socks, sportswear, jeans, swimsuits, etc.

[0059] In addition, a pleated member containing the recycled polyurethane elastic fiber of this embodiment and a sanitary material containing the same are also one embodiment of the present invention. Specific examples of sanitary materials include absorbent articles represented by disposable diapers and sanitary products, masks, bandages, etc. Pleated members made by bonding elastic fibers to nonwoven fabrics by hot melting are used in the waist and leg parts of diapers, and the pleated member of this embodiment is also applicable to such parts in the same manner as ordinary polyurethane elastic fibers.

[0060] Example

[0061] The present invention is specifically described below by way of examples and comparative examples. The present invention is not limited to these examples. The various determination methods described in the examples were performed using the methods described below. The evaluation results are shown in Table 1 below.

[0062] (1) Spinning method of recycled polyurethane elastic fiber

[0063] After the recycled polyurethane elastic fiber is degassed with the spinning stock solution under reduced pressure, a 400-mesh metal mesh filter is used as a spinneret filter, and the solvent is evaporated by extruding it in hot air through the fine holes of the spinning nozzle (the nozzle has two fine holes) under a nitrogen atmosphere. The dried filaments are passed through a godet roller, and an oil agent component with polyalkylsiloxane and mineral oil as the main components is attached to the polyurethane elastic fiber at about 5% by weight on the oiling roller. At a speed range of more than 600m / min and less than 1000m / min per minute, 500g of 22dtex / 2 filaments (single filament fineness 11dtex) polyurethane elastic fiber is wound on a paper tube. Various evaluations are performed using this polyurethane elastic fiber. Generally, the physical properties of 22dtex polyurethane elastic fibers preferably have high breaking strength and breaking elongation, but if the breaking strength is more than 25cN and the breaking elongation is more than 550%, it can be used in general use.

[0064] (2) Method for measuring reduced viscosity of recycled polyurethane elastic fibers and raw material polyurethane elastic fibers

[0065] The measurement was performed at 25°C using an Ubbelohde viscometer according to the method of JIS K7367-1. The solution concentration used a weight concentration, and the sample was dissolved in a manner to become 0.50% by weight. N,N-dimethylacetamide was used as the solvent. The insoluble matter produced was precipitated by centrifugation, and the supernatant was used for measurement. As a pretreatment, the oil component contained in the outside or inside of the polyurethane elastic fiber was removed. Specifically, about 3 g of polyurethane elastic fiber was used, and Soxhlet extraction was performed with 300 g of hexane for 5 hours, and the recycled polyurethane elastic fiber after treatment was fully dried for use.

[0066] (3) Method for determining the total weight ratio (weight %) of mineral oil and silicone oil in recycled polyurethane elastic fibers

[0067] Add petroleum ether to the extent that the recycled polyurethane elastic fiber (about 3g) is immersed, gently stir and mix, and then discard the petroleum ether. Repeat this operation 3 times, rinse the surface oil component, fully dry, and accurately weigh it. The dried sample is Soxhlet extracted with 300g of hexane for 5 hours. After the extracted hexane is concentrated, it is purified and concentrated by silica gel column chromatography using hexane as the developing solvent. Based on the obtained mineral oil and silicone oil residue weight and the accurately weighed weight, the total weight ratio of mineral oil and silicone oil contained in the recycled polyurethane elastic fiber is obtained.

[0068] (4) Method for determining the total weight ratio (weight %) of mineral oil and silicone oil contained in raw material polyurethane elastic fiber

[0069] The raw material polyurethane elastic fiber (about 3 g) was accurately weighed and Soxhlet extraction was performed with 300 g of hexane for 5 hours. After the hexane after extraction was concentrated, it was purified and concentrated by silica gel column chromatography using hexane as the developing solvent. The total weight ratio of mineral oil and silicone oil contained in the recycled polyurethane elastic fiber was obtained based on the obtained mineral oil and silicone oil residue weight and the accurately weighed weight.

[0070] (5) Determination of breaking strength [cN] and breaking elongation [%]

[0071] The tensile strength and elongation were measured at 20°C and 65% humidity at a rate of 50 cm / min for a test yarn with a sample length of 5 cm using a tensile testing machine (TENSILON RTG-1210 manufactured by ORIENTEC CO., LTD.). Seven points were measured for each test yarn, and the average of the five points excluding the maximum and minimum values ​​was calculated.

[0072] (6) Determination of adhesive stress of polyurethane elastic fiber [cN]

[0073] The sample was installed in a tensile testing machine (manufactured by ORIENTEC CO., LTD. under the trade name TENSILON RTG-1210) with a gripping interval of 50 mm, and the following method was used for measurement under the conditions of temperature 20°C and humidity 65 wt%. A 22 dtex / 2 filament monofilament was divided into two. After each torn filament was installed in the upper and lower chucks in a manner of tearing the bifurcation, the stress was measured by the same method as the strength and elongation measurement.

[0074] If measured by tearing a single filament, the stress of the part with strong adhesion is high, and the part with weak adhesion shows a low value. Therefore, the value fluctuates up and down as the measurement proceeds. The average of the maximum and minimum values ​​of the measured stress is taken as the adhesive stress. For each test filament, 7 points are measured, and the average of the 5 points excluding the maximum and minimum values ​​is calculated. The sample elastic filament with a small fluctuation range and a large average stress value can be judged as having strong adhesion of the filament and is good.

[0075] (7) Evaluation of relaxation

[0076] like Figure 1 As shown in the figure, an elastic yarn winding cylinder (1) with oil attached is installed on the unwinding side of the unwinding speed ratio measuring machine, and a paper tube (2) for winding is installed on the winding side. After adjusting the winding speed to a certain speed, rollers (3) and (4) are started at the same time. In this state, almost no tension is applied to the yarn (5), so the yarn will stick to the cheese yarn and will not move away, and the unwinding point (6) is at Figure 1 The state shown. By changing the unwinding speed, the unwinding point (6) of the yarn (5) from the cheese yarn changes, so the unwinding speed is set in a way that this point coincides with the contact point (7) between the cheese yarn and the roller. The unwinding speed ratio is calculated by the following formula. The smaller the value, the better the unwinding property. After winding onto the cheese yarn and storing at room temperature for 30 days, the unwinding speed ratio is calculated by the following formula:

[0077] Unwinding speed ratio (%) = (winding speed - unwinding speed) / unwinding speed × 100

[0078] The release properties were evaluated according to the following evaluation criteria.

[0079] [Evaluation criteria]

[0080] ◎: Relaxation rate ratio is less than 60%

[0081] ○: The relaxation rate ratio is 60% or more and less than 65%

[0082] ○~△: The relaxation rate ratio is 65% or more and less than 70%

[0083] △: The relaxation rate ratio is 70% or more and less than 80%

[0084] ×: The relaxation rate ratio is 80% or more.

[0085] (8) Preparation of polyurethane elastic fiber for raw materials

[0086] A DMAc solution of polyurethane containing PTMG, MDI, ethylenediamine and diethylamine with a molecular weight of 2000 was polymerized by a conventional method to prepare a DMAc polymer solution. At this time, various adjustments were made to the molar ratio of MDI to polyol and the molar ratio of ethylenediamine to diethylamine, and various adjustments were made to the amount of oil agent applied. In addition, the raw material polyurethane elastic fiber was produced according to the above-mentioned <(1) Spinning method of recycled polyurethane elastic fiber>, and the reduced viscosity and oil agent content were measured in advance. It should be noted that if (the number of moles of MDI) / (the number of moles of polyol) is close to 1, the molecular weight of the so-called prepolymer increases. In addition, the amount of amine is determined by the amount of unreacted isocyanate sites, and the smaller the ratio of diethylamine at this time, the larger the molecular weight of the polyurethane. By appropriately adjusting and combining these ratios, the molecular weight of the polymer that can be spun, that is, the reduced viscosity, can be adjusted. In addition, as the oil agent, the oil agent described in Example 3 of Japanese Patent Gazette No. 4731048 was used.

[0087] [Reference Example 1] (Polyurethane elastic fiber produced using virgin polymer)

[0088] A DMAc solution of polyurethane containing PTMG having a molecular weight of 1800, MDI and ethylenediamine was polymerized by a conventional method to prepare a DMAc polymer solution. At this time, the solution concentration was adjusted to 30% with (the number of moles of MDI) / (the number of moles of polyol) being 1.60, and polyurethane elastic fibers were obtained according to the above-mentioned <(1) Spinning method of recycled polyurethane elastic fibers>.

[0089] [Examples 1 to 9 and Comparative Examples 1 and 2]

[0090] Using a variety of raw materials for polyurethane elastic fibers, after adjusting the range of concentrated viscosity and oil content, a slurry of DMAc solution is prepared. This is mixed with the DMAc polymer solution of Reference Example 1 as needed, and polyurethane elastic fibers are obtained according to the above-mentioned <(1) Spinning method of recycled polyurethane elastic fibers>. The detailed conditions for preparing the recycled slurry, the mixing ratio with the original polymer, the spinning state, and the results of the physical property evaluation of the obtained polyurethane elastic fibers are shown in the following Table 1. It should be noted that the evaluation of the relaxation properties was only performed on Examples 8 and 9.

[0091] [Table 1]

[0092]

[0093] Industrial Applicability

[0094] The recycled polyurethane elastic fiber of the present invention can be generally used as a recycled polyurethane elastic fiber, and thus can make a significant contribution to 2R (reduction and recycling) by recycling non-standard yarns that would otherwise be discarded as raw materials.

[0095] Description of Reference Numerals

[0096] 1 Elastic silk winding cylinder

[0097] 2. Paper tube for winding side

[0098] 3 Rollers

[0099] 4 Rollers

[0100] 5 Silk

[0101] 6 Relaxation Points

[0102] 7 Touchpoints

Claims

1. A method for producing recycled polyurethane elastic fibers, characterized in that: The reduced viscosity of the recycled polyurethane elastic fiber is 1.00 or more, and the total amount of mineral oil and silicone oil remaining in the recycled polyurethane elastic fiber after washing with petroleum ether is less than 10% by weight relative to the weight of the washed fiber. A slurry prepared by dissolving the raw material polyurethane elastic fiber in a solvent is used as a raw material of a spinning solution in the production of the recycled polyurethane elastic fiber. As the raw material polyurethane elastic fiber, a polyurethane elastic fiber containing a total content of mineral oil and silicone oil of 20% by weight or less is used. The polyurethane elastic fiber containing the mineral oil and the silicone oil in a total content of 12% by weight or more is less than 10% by weight of the entire polyurethane elastic fiber used as a raw material, and As the raw material polyurethane elastic fiber, a polyurethane elastic fiber having a reduced viscosity of 1.10 or more and 2.50 or less is used in an amount of 70 wt % or more of the entire raw material polyurethane elastic fiber.

2. The method for producing recycled polyurethane elastic fibers according to claim 1, wherein: The total amount of mineral oil and silicone oil remaining in the fiber after washing with petroleum ether is 0.1% by weight or more based on the weight of the fiber after washing.

3. The method for producing recycled polyurethane elastic fibers according to claim 1 or 2, wherein: The reduced viscosity of the recycled polyurethane elastic fiber is 5.00 or less.

4. The method for producing recycled polyurethane elastic fibers according to claim 1, wherein: As the raw material polyurethane elastic fiber, a polyurethane elastic fiber containing a mineral oil and a silicone oil in a total content of 0% by weight or more and 17% by weight or less is used.

5. The method for producing recycled polyurethane elastic fibers according to claim 1, wherein: As the raw material polyurethane elastic fiber, a polyurethane elastic fiber containing a mineral oil and a silicone oil in a total content of 0% by weight or more and 15% by weight or less is used.

6. The method according to claim 1, wherein: The polyurethane elastic fiber containing the mineral oil and the silicone oil in a total content of 10 wt % or more is 10 wt % or less of the entire polyurethane elastic fiber used as the raw material.

7. The method according to claim 1, wherein: The polyurethane elastic fiber containing the mineral oil and the silicone oil in a total content of 8% by weight or more is 10% by weight or less of the entire polyurethane elastic fiber used as the raw material.

8. The method according to claim 1, wherein: As the raw material polyurethane elastic fiber, only polyurethane elastic fibers having a reduced viscosity of 1.00 or more and 4.20 or less are used.

9. The method according to claim 1, wherein: As the raw material polyurethane elastic fiber, a polyurethane elastic fiber having a reduced viscosity of 1.10 or more and 2.50 or less is used at 100% by weight of the entire raw material polyurethane elastic fiber.

10. The method according to claim 1, wherein: The solvent for dissolving the raw material polyurethane elastic fiber is either DMF or DMAc.

11. The method according to claim 1, wherein: The solvent for dissolving the raw material polyurethane elastic fiber is DMAc.

12. The method according to claim 1, wherein: The temperature when dissolving the raw material polyurethane elastic fiber in the solvent is 50° C. or higher and 100° C. or lower.

13. The method according to claim 1, wherein: The temperature when the raw material polyurethane elastic fiber is dissolved in the solvent is 60° C. or higher and 90° C. or lower.

14. The method according to claim 1, wherein: A solution obtained by mixing a slurry prepared by dissolving the raw material polyurethane elastic fiber in a solvent and a newly prepared virgin polymer solution was used as the spinning stock solution. 15 . A fiber structure comprising recycled polyurethane elastic fibers obtained by the production method according to claim 1 .

16. A pleated member comprising recycled polyurethane elastic fibers obtained by the production method according to any one of claims 1 to 14.

17. A sanitary material comprising the pleated member according to claim 16.

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