Low-temperature easy-to-shape composite spandex and preparation method thereof

Abstract

The invention relates to low-temperature easy-to-shape composite spandex and a preparation method thereof. The low-temperature easy-to-shape composite spandex comprises two main components, namely polyvinyl acetal and polyurethane-urea. The preparation method comprises the following steps: uniformly mixing polyvinyl acetal and polyurethane-urea in a solution blending manner, and spinning the composite spandex by using a dry spinning technology. The polyvinyl acetal is added, so that the internal phase separation degree of the spandex can be effectively reduced, the intermolecular acting force is weakened, a molecular chain is rapidly dissociated and rearranged under the condition of relatively low energy, and efficient shaping of the spandex is realized. In addition, a microcrystalline structure formed by the polyvinyl acetal can serve as a physical crosslinking point in the fiber, and the original mechanical strength and elasticity of the spandex fiber are reserved to the maximum extent. The shaping efficiency of the prepared composite bare spandex yarn can reach 70% at the temperature of 120-140 DEG C, the shaping effect of an ammonia-containing fabric formed by blending the composite bare spandex yarn with polylactic acid fibers and polyethylene fibers is excellent, and the shrinkage rate is lower than 3.0%.

Description

Technical Field

[0001] The invention belongs to the field of elastic fibers, and in particular relates to a low-temperature easy-to-set composite spandex and a preparation method thereof. Technical Background

[0002] As a fiber material with high elasticity, spandex is generally used in combination with other fibers. Among them, the proportion of spandex is generally no more than 10%, which can give spandex-containing fabrics a certain degree of elasticity. Most fabrics need to go through the process of heat setting during processing to eliminate the wrinkles and deformation of the fabric surface, while improving the feel and dimensional stability of the fabric. Different fibers require different setting temperatures. For example, the setting temperature of polyester is 180-200℃, the setting temperature of spandex is 180-195℃, the setting temperature of nylon is 160-180℃, the setting temperature of acrylic is 140-160℃, the setting temperature of polylactic acid fiber is 130-140℃, and the setting temperature of polypropylene fiber is 120-130℃. Fabrics such as polyester / spandex and nylon / spandex can achieve good setting effects under higher temperature conditions because the setting temperatures of the component fibers are similar. However, for fabrics with large differences in the setting temperatures of their component fibers, it is necessary to use a type of spandex with a setting temperature close to that of the main fibers of the fabric. For example, polylactic acid / spandex fabrics, polyethylene / spandex and other fabrics require spandex that can be set at 130-140 degrees during the weaving process. This functional spandex, which has a setting temperature much lower than that of conventional spandex, is the so-called low-temperature easy-setting spandex.

[0003] At present, most of the development and research of low-temperature easy-setting spandex is to change the hard segment composition of spandex, reduce the arrangement regularity and crystallization degree of the hard segment, so as to reduce the restriction of the hard segment crystallization on the molecular chain segment, so that the spandex can quickly achieve the relaxation and rearrangement of the molecular chain segment under low energy conditions, and achieve a good setting effect. For example, asymmetric diisocyanate is used to replace diphenylmethane diisocyanate with good symmetry (patent CN101849048A), asymmetric amine chain extender or alcohol chain extender replaces highly symmetric chain extender (patent CN1176967A), etc. However, the change of hard segment composition often has a greater impact on the mechanical properties and heat resistance of spandex. Summary of the invention

[0004] Technical problem: In view of the shortcomings of the prior art, the present invention provides a low-temperature easy-to-set composite spandex and a preparation method thereof, and prepares dry-process spandex by dissolving and blending, so that the composite spandex has both high setting properties and good mechanical strength.

[0005] Technical solution: The present invention provides a low-temperature easy-to-set composite spandex, which contains two components: polyvinyl acetal and polyurethane-urea; the mass ratio of the polyvinyl acetal to the polyurethane-urea is 10:90 to 50:50.

[0006] The preparation method comprises the following steps:

[0007] 1) mixing polyvinyl acetal with a solvent to obtain a polyvinyl acetal solution;

[0008] 2) reacting the polymer polyol, diisocyanate, diamine chain extender and terminator to obtain a polyurethane-urea solution;

[0009] 3) The two solutions are mixed to obtain a spinning solution, and low-temperature easy-to-set composite spandex is prepared by dry spinning.

[0010] in:

[0011] The mass concentration of the polyvinyl acetal solution is 20-30wt%.

[0012] The polymer polyol is a polyether diol or polyester diol with a number average molecular weight of 1000-5000 g / mol, including one or more of polytetrahydrofuran diol, polyethylene glycol or polypropylene glycol.

[0013] The diisocyanate includes toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dimethylbiphenyl diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, dicyclohexylmethane diisocyanate and / or one or more of their derivatives and / or modified polymers.

[0014] The diamine chain extender includes C2-C8 small molecule diamines, including one or more of ethylenediamine, propylenediamine, pentamethylenediamine and hexamethylenediamine.

[0015] The terminator includes a small molecule monoamine or monoalcohol of C2-C10, including one or more of dimethylamine, diethylamine, dipropylamine, n-butanol, and ethanolamine.

[0016] The temperature of the dry spinning tunnel is set at 200-220°C, and the spinning winding speed is 500-600m / min.

[0017] Beneficial effects: Adding an appropriate amount of polyvinyl acetal to spandex can effectively reduce the degree of internal phase separation of spandex, weaken the intermolecular forces, and enable the molecular chains to quickly dissociate and rearrange under low energy conditions, thereby achieving efficient shaping of spandex. In addition, the microcrystalline structure formed by polyvinyl acetal can act as a physical cross-linking point inside the fiber, retaining the original mechanical strength and elasticity of the spandex fiber to the greatest extent. The low-temperature easy-to-shape spandex bare yarn of the present invention can achieve a shaping efficiency of 70% at 120-140°C, and the fabric blended with polylactic acid fiber and polyethylene fiber has a good shaping effect and a shrinkage rate of less than 3.0%. DETAILED DESCRIPTION

[0018] The low-temperature easy-to-set composite spandex contains polyvinyl acetal and polyurethane-urea, and is obtained by dry spinning using the polyurethane-urea and polyvinyl acetal as spinning raw materials.

[0019] The mass ratio of the polyvinyl acetal to the polyurethane-urea is 10:90 to 50:50;

[0020] The polyvinyl acetal comprises a reaction product of polyvinyl alcohol and an aldehyde substance, wherein the aldehyde substance comprises formaldehyde and / or butyraldehyde; further, the aldehyde substance comprises formaldehyde; further, the polyvinyl acetal comprises at least one of polyvinyl formal and polyvinyl butyral, wherein polyvinyl formal is preferred; the product brand may be one or more combinations of PA98897 of Guangdong Wengjiang Chemical Reagent Co., Ltd., BD6468 of Hubei Baidu Chemical Co., Ltd., XHL6931 of Hubei Xinhongli Chemical Co., Ltd., and XK1325 of Hubei Xinkang Pharmaceutical Chemical Co., Ltd.;

[0021] The number average molecular weight of the polyvinyl acetal is 40000-80000 g / mol;

[0022] In the present invention, by adding an appropriate amount of polyvinyl acetal polymer with a low softening point, polar solvent solubility, and thermoplasticity to spandex, the two substances can be directly mixed and dry-spun to obtain composite spandex, and the heat-deformable property of polyvinyl acetal is utilized to enable the spandex to have heat setting properties under relatively low temperature conditions. Compared with adding other low-melting-point polymers such as TPU to spandex, polyvinyl acetal has the characteristics of low thermoplastic temperature and self-crystallization, which can not only reduce the temperature required for setting, but also form a microcrystalline structure as a physical cross-linking point inside the composite fiber.

[0023] The polyurethane-urea comprises the reaction product of a polymer polyol, a diisocyanate, a diamine chain extender and a terminator;

[0024] Furthermore, the polyurethane-urea is obtained by reacting a polymer polyol and a diisocyanate to obtain a prepolymer, which is then reacted with a diamine chain extender and a terminator;

[0025] The polymer polyol is polyester polyol and / or polyether polyol, and further the polymer polyol includes polyether polyol, and the polyether polyol includes one or more of polytetramethylene glycol, polyethylene glycol or polypropylene glycol;

[0026] The number average molecular weight of the polymer polyol is 1000 to 5000 g / mol;

[0027] The diisocyanates independently include toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dimethylbiphenyl diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, dicyclohexylmethane diisocyanate and / or derivatives and / or modified polymers thereof;

[0028] The diamine chain extender includes a C2-C8 small molecule diamine, and further, the small molecule diamine includes one or more of ethylenediamine, propylenediamine, pentamethylenediamine, and hexamethylenediamine;

[0029] The terminator includes a small molecule monoamine or monoalcohol of C2 to C10, and further includes one or more of dimethylamine, diethylamine, dipropylamine, n-butanol, and ethanolamine.

[0030] In some embodiments of the present invention, the polyurethane-urea preparation method comprises the following steps:

[0031] The polymer polyol and diisocyanate are reacted to obtain a prepolymer-containing product, which is dissolved in the presence of a solvent to obtain a prepolymer solution, and the prepolymer solution is reacted with a mixed amine solution containing a diamine chain extender and a terminator to obtain a polyurethane-urea stock solution;

[0032] The mass ratio of the polymer polyol to the polyurethane-urea is 65-85wt%;

[0033] The mass ratio of the diisocyanate to the polyurethane-urea is: 15-25wt%;

[0034] The mass ratio of the diamine chain extender to the polyurethane-urea is 2-8wt%;

[0035] The monoamine end-capping agent accounts for 0.1 to 1.0 wt% of the polyurethane-urea mass;

[0036] The solvent includes one or more of N,N-dimethylacetamide, N-methyl-2-pyrrolidone and dimethylformamide.

[0037] In some embodiments of the present invention, the method for preparing the low-temperature easy-setting composite spandex comprises the following steps:

[0038] (1) mixing polyvinyl acetal with a solvent to obtain a polyvinyl acetal solution;

[0039] (2) adopting a two-step reaction of prepolymerization-chain extension to obtain a polyurethane-urea stock solution;

[0040] (3) mixing the two solutions to obtain a spinning solution, and spinning the spinning solution through a spinning assembly to obtain the low-temperature easy-setting spandex;

[0041] Preferably, the polyvinyl acetal is dried before the dissolution process of the polyvinyl acetal in step (1), the drying temperature is 50 to 60° C., and the drying time is 10 to 24 hours;

[0042] Preferably, the mixing temperature of the polyvinyl acetal and the solvent in step (1) is 70-80° C., and the mixing temperature is 3-6 hours; the polyvinyl acetal solution can be selectively filtered to remove impurities and incompletely dissolved solid small particles;

[0043] Preferably, the polyvinyl acetal solution in step (1) has a mass concentration of 20-30 wt % and a viscosity of 2000-3000 P;

[0044] Preferably, the mass concentration of the polyurethane-urea stock solution in step (2) is 30-40wt%, and the viscosity is 2000-3000P;

[0045] Preferably, the mixing temperature in step (3) is 40-60° C. and the mixing time is 100-120 min;

[0046] Preferably, the mass concentration of the spinning solution in step (3) is 25-35%, and the viscosity is 2000-3000P;

[0047] Wherein, solution mass concentration = solute mass / total solution mass × 100%;

[0048] Preferably, the spinning solution can be aged before spinning in step (3), the aging temperature is 25 to 45° C., and the aging time is 15 to 30 hours.

[0049] Preferably, the spinning method described in step (3) is dry spinning technology.

[0050] Preferably, the spinning through the spinneret assembly in step (3) further comprises the steps of drying in the spinning tunnel, false twisting, oiling, drawing, and winding;

[0051] Preferably, the spinning tunnel temperature is 200-220° C., and the winding speed is 500-600 m / min.

[0052] The following examples are used to describe the production process of the present invention in detail, but these examples should not be construed as limiting the present invention in any sense.

[0053] Preparation of polyvinyl acetal solution:

[0054] Commercially available polyvinyl acetal is dry-dried at 50°C for 12 hours to remove moisture; it is then mixed with N,N-dimethylacetamide and stirred at 70°C for 4 hours; the polyvinyl acetal solution is filtered to remove impurities and incompletely dissolved solid small particles to obtain a polyvinyl formal solution with a mass concentration of 25wt%.

[0055] Preparation of polyurethane-urea solution:

[0056] Polytetrahydrofuran diol (number average molecular weight of 1800) and diphenylmethane diisocyanate are mixed and reacted at 70°C for 2 hours to obtain a prepolymer; a mixture of ethylenediamine and n-butanol is added dropwise to the prepolymer for chain extension reaction, and N,N-dimethylacetamide is added for dilution to obtain a polyurethane-urea stock solution with a mass concentration of 35wt%. The mass ratio of polytetrahydrofuran diol: diphenylmethane diisocyanate: ethylenediamine: ethylenediamine is 75:20:4.5:0.5; the examples and comparative examples of the present invention all use this type of polyurethane-urea solution.

[0057] The specific raw material component types and proportions of the embodiments and comparative examples are shown in Table 1 below:

[0058]

[0059]

[0060] Preparation of composite spandex:

[0061] Add the polyvinyl acetal solution and the polyurethane-urea solution into a static mixer, mix at 40°C for 120 minutes, and after fully mixing, age at 45°C for 20 hours to obtain a composite spinning solution, wherein the mass concentration of the composite spinning solution is controlled to be 35%;

[0062] The composite spinning solution was ejected through a spinneret assembly, passed through a spinning tunnel at 220° C. to remove N,N-dimethylacetamide, false twisted, coated with a spinning oil, and wound at a spinning speed of 600 min to obtain a 20-denier composite spandex.

[0063] The spinning conditions and spinnability performance of the embodiments and comparative examples are shown in Table 2 below:

[0064] Spinnability: The total number of spinning failures in a spinning position within 48 hours will be recorded. Spinning failures include broken yarns, doubling, and other spinning process stops caused by problems with the stock solution. The spinnability performance is excellent if the total number of failures is less than 1, good if it is 2 to 4, and poor if it is more than 5;

[0065] Table 2:

[0066]

[0067] The fibers prepared in the examples and comparative examples were tested for spinnability, mechanical properties, bare yarn shaping efficiency, and fabric shrinkage, and the testing methods were as follows:

[0068] (1) Mechanical properties: The test is based on the textile industry standard "Test Method for Tensile Properties of Spandex Yarn" (FZ / T5006-2013);

[0069] (2) Shaping efficiency: Measure a 10cm sample, stretch it 2 times, and place it in a 120-140°C dry heat oven for 2 minutes; after cooling for 30 minutes, measure the sample length again. The formula for calculating the shaping efficiency is as follows:

[0070] Shaping efficiency = (l2-l0) / (l1-l0)*100%.

[0071] Among them: L0 is the original length, L1 is the length after drafting, and L2 is the length after shaping.

[0072] (3) Fabric shrinkage rate: Cut a piece of composite spandex and polylactic acid fiber interwoven fabric larger than 1 square meter, and keep the edge of the fabric; use a needle clip to fix the fabric sample, put it into a 120-140 degree oven for 2 minutes to set it, and cool it for 30 minutes. Mark a 100*100cm square at a certain distance inward from the edge of the fabric; wash the fabric sample in 30 degree warm water, then dry it in a dryer. After it is fully cooled, measure the warp and weft dimensions of the marked square. The formula for calculating the shrinkage rate is as follows:

[0073] Shrinkage rate = (M0-M1) / M0*100%

[0074] Among them: M0 is the size before washing, and M1 is the size after washing.

[0075] The performance test results of the fibers prepared in the examples and comparative examples are shown in Table 3 below:

[0076] Table 3:

[0077]

Claims

1. A low-temperature easy-setting composite spandex, characterized in that: The low-temperature easy-to-set composite spandex contains two components, namely, polyvinyl acetal and polyurethane-urea; the mass ratio of the polyvinyl acetal to the polyurethane-urea is 10:90-50:

50.

2. A method for preparing a low-temperature easy-setting composite spandex, characterized in that: The preparation method comprises the following steps: 1) mixing polyvinyl acetal with a solvent to obtain a polyvinyl acetal solution; 2) reacting the polymer polyol, diisocyanate, diamine chain extender and terminator to obtain a polyurethane-urea solution; 3) The polyvinyl acetal solution and the polyurethane-urea solution are mixed to obtain a spinning solution, and low-temperature easy-to-set composite spandex is prepared by dry spinning.

3. The method for preparing the low-temperature easy-setting composite spandex according to claim 2, characterized in that: The polyvinyl acetal is at least one of polyvinyl formal and polyvinyl butyral, and the number average molecular weight of the polyvinyl acetal is 40000-80000 g / mol.

4. The method for preparing the low-temperature easy-setting composite spandex according to claim 2, characterized in that: The mass concentration of the polyvinyl acetal solution is 20-30wt%.

5. The method for preparing the low-temperature easy-setting composite spandex according to claim 2, characterized in that: The polymer polyol is a polyether diol or polyester diol with a number average molecular weight of 1000-5000 g / mol, including one or more of polytetrahydrofuran diol, polyethylene glycol or polypropylene glycol.

6. The method for preparing the low-temperature easy-setting composite spandex according to claim 2, characterized in that: The diisocyanate includes toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dimethylbiphenyl diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, dicyclohexylmethane diisocyanate and / or one or more of their derivatives and / or modified polymers.

7. The method for preparing the low-temperature easy-setting composite spandex according to claim 2, characterized in that: The diamine chain extender includes C2-C8 small molecule diamines, including one or more of ethylenediamine, propylenediamine, pentamethylenediamine and hexamethylenediamine.

8. The method for preparing the low-temperature easy-setting composite spandex according to claim 2, characterized in that: The terminator includes a small molecule monoamine or monoalcohol of C2-C10, including one or more of dimethylamine, diethylamine, dipropylamine, n-butanol, and ethanolamine.

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