Low-melting-point spandex and preparation method thereof

Abstract

The invention discloses low-melting-point spandex and a preparation method thereof.The method comprises the steps that polyhydric alcohol, diphenylmethane diisocyanate and 1, 4-butanediol are fully mixed by mass and then subjected to extrusion molding, and slices are prepared; the slices are dissolved in DMAC to prepare a polyurethane solution with the mass concentration of 35%, then a mixed amine solution is added for a chain extension reaction, a functional auxiliary agent is added after chain extension, and a polyurethane stock solution is obtained; curing the polyurethane stock solution to enable the apparent viscosity of the polyurethane stock solution to reach 6000-10000 poise; and carrying out dry spinning on the cured spinning solution to obtain the low-melting-point spandex. The low-melting-point spandex obtained in the invention can be shaped at a low temperature, can avoid or reduce damage to fabrics caused by high-temperature shaping, and can well maintain the original quality of the fabrics.

Description

Technical Field

[0001] The present application belongs to the technical field of spandex preparation, and specifically relates to a low-melting-point spandex and a preparation method thereof. Background Art

[0002] The spandex used in sanitary materials such as diapers needs to be bonded to non-woven fabrics, which requires the spandex to have a low melting point to facilitate the bonding of the spandex to the non-woven fabrics.

[0003] Existing research on spandex fiber products and spandex fiber production processes focuses on how to increase the Vicat softening temperature of spandex fibers. Spandex fibers with high Vicat softening temperature have better heat resistance, but also bring certain disadvantages, such as being not conducive to ironing, which limits its application range.

[0004] Due to the design limitations of the spandex preparation process, the spandex prepared by the existing process has the problems of high melting point, low elongation at break, and poor heat-setting resilience, resulting in poor adhesion between the spandex fiber and other fabrics. High-temperature setting will also cause damage to the fabric, affecting its feel, strength and other properties. Summary of the invention

[0005] The technical problem to be solved by the present application is that the low-melting-point spandex prepared by the prior art generally has poor adhesion to other fabrics, and high-temperature shaping will damage the fabric, affecting its feel, strength and other properties.

[0006] In order to solve the above problems, the present application provides a method for preparing low-melting-point spandex, comprising the following steps:

[0007] Slice preparation: polyol, diphenylmethane diisocyanate and 1,4-butanediol are fully mixed according to mass measurement and then extruded to obtain slices;

[0008] Chain extension: dissolving the slices prepared in the slice preparation step in DMAC to prepare a polyurethane solution with a mass concentration of 35%, then adding a mixed amine solution to carry out a chain extension reaction, and adding a functional additive after chain extension to obtain a polyurethane stock solution;

[0009] Ripening: Ripening the polyurethane stock solution prepared in the chain extension step to a viscosity of 6000-10000 poise;

[0010] Spinning: The spinning solution prepared in the aging step is dry-spun to obtain low-melting-point spandex.

[0011] The present application first performs a prepolymerization reaction to obtain a prepolymer and slices it, then performs a chain extension reaction on the prepolymer slices to obtain a polymerization stock solution, and the polymerization stock solution is spun after aging to obtain a low-melting-point spandex. The low-melting-point spandex obtained in the present application can be shaped at a lower temperature, which can avoid or reduce the damage to the fabric caused by high-temperature shaping, can better maintain the original quality of the fabric, make the fit between the fabric layers tighter and firmer, improve the overall stability and durability of the fabric product, and solve the problem of poor bonding ability between the low-melting-point spandex prepared by the prior art and other fabrics.

[0012] As an optional solution for the polyol in the above-mentioned slice preparation step, the polyol includes at least one of polyester polyol and polyether polyol.

[0013] As an optional solution for the polyol in the above-mentioned slice preparation step, the molecular weight of the polyol is 2000.

[0014] As an optional solution for the polyol in the above-mentioned chip preparation step, the polyester polyol is polybutylene adipate diol with a molecular weight of 2000, and the polyether polyol is polytetrahydrofuran with a molecular weight of 2000.

[0015] As a preferred choice of the above-mentioned slicing preparation step, in the slicing preparation step, the isocyanate index of the diphenylmethane diisocyanate and the polyol in the raw materials is 1.01 to 1.4.

[0016] The isocyanate index represents the equivalent ratio of isocyanate to polyol. The isocyanate index value of the present application is slightly greater than 1. This is because during the polymerization process, due to the presence of trace moisture in the system and the interaction between isocyanate groups, a relatively large amount of isocyanate groups are lost. Therefore, during the synthesis, a slight excess of isocyanate groups is usually made to achieve maximum chain extension of the molecule.

[0017] As an option for the mixed amine in the above chain extension step, the mixed amine is a mixture of a chain extender and a terminator, wherein the chain extender is one or two amines selected from ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, 1,2-butylenediamine (1,2-diaminotoluene), 1,3-butylenediamine (1,3-diaminotoluene), 1,4-butylenediamine (1,4-diaminotoluene), pentamethylenediamine, and 1,6-hexamethylenediamine, and the terminator is diethylamine; the mixed amine is dissolved in a DMAC solution with a mass concentration of 7% to 8%.

[0018] As an alternative to the above chain extension step, after the chain extension reaction, 2 The molar ratio to -NCO is 1.01 to 1.1.

[0019] As an option, the molar ratio of the chain extender to the terminator is 8-10:1.

[0020] As an option, in the chip preparation step, the mixing and extrusion is carried out in a twin-screw extruder.

[0021] The present application also provides a low-melting-point spandex based on the above method.

[0022] The beneficial effects of this application are:

[0023] The preparation method of low-melting spandex provided by the present application first slices the prepolymer, then dissolves the slices and performs chain extension to obtain a polymer stock solution, and then matures the polymer stock solution before spinning. The preparation method of low-melting spandex adopted by the present application does not require high-temperature melting and other processes, the overall reaction process is short, and the investment density is reduced. In addition, the raw material selection of the present application is flexible and changeable, and polyester / polyether polyols can be used.

[0024] The low-melting-point spandex obtained in the present application can melt at a relatively low temperature and combine with other fibers, so that the fit between the fabric layers is tighter and firmer, thereby improving the overall stability and durability of the fabric product. DETAILED DESCRIPTION

[0025] The embodiments of the technical solution of the present application are described in detail below. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0026] The present invention provides a method for preparing a low-melting-point spandex, comprising the following steps:

[0027] Slice preparation: According to the mass measurement, the polyol, diphenylmethane diisocyanate, and 1,4-butanediol are fully mixed and then extruded to obtain slices; wherein the polyol can be selected as at least one of polyester polyol and polyether polyol, for example, the polyester polyol is polybutylene adipate diol (PBA) with a molecular weight of 2000, and the polyether polyol is polytetrahydrofuran (PTMG) with a molecular weight of 2000, or a mixture of polyester polyol and polyether polyol can be selected, and the isocyanate index is 1.01-1.4; in this step, the equipment for mixing and extruding the polyol, diphenylmethane diisocyanate, and 1,4-butanediol is a twin-screw extruder. In the following specific embodiment, the twin-screw extruder is selected, the screw diameter is 65mm, the screw aspect ratio is 35mm, the screw extrusion temperature is 185°C, the temperature accuracy is controlled at ±2°C, the screw speed is 150rpm, and the screw load is 75%;

[0028] Chain extension: dissolve the slices prepared in the slice preparation step in DMAC to prepare a polyurethane solution with a mass concentration of 35%, then add a mixed amine solution to carry out a chain extension reaction, and add a functional additive after chain extension to obtain a polyurethane stock solution; in the chain extension step, the mixed amine is a mixture of a chain extender and a terminator, wherein the chain extender is one or two amines selected from ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, 1,2-butylenediamine (1,2-diaminotoluene), 1,3-butylenediamine (1,3-diaminotoluene), 1,4-butylenediamine (1,4-diaminotoluene), pentamethylenediamine, and 1,6-hexamethylenediamine, and the terminator is diethylamine; the mixed amine is dissolved in a DMAC solution with a mass concentration of 7% to 8%. The molar ratio of the chain extender to the terminator is 8-10:1; in the chain extension step, -NH 2 The molar ratio of -NCO to -NCO is 1.01 to 1.1; in the chain extension step, the functional additive can be an antioxidant, an anti-yellowing agent, a cohesion enhancer, an ultraviolet absorber, etc.; it can be understood that although the mixed amine in the following specific embodiments is a mixed amine configured by ethylenediamine and diethylamine, those skilled in the art should understand that the embodiments are only used to explain the preferred implementation scheme given in the present application, and are not used to limit the present application. Under the inspiration given by the embodiments, those skilled in the art can also give any type of amine among 1,2-propylenediamine, 1,3-propylenediamine, 1,2-butylenediamine (1,2-diaminotoluene), 1,3-butylenediamine (1,3-diaminotoluene), 1,4-butylenediamine (1,4-diaminotoluene), pentamethylenediamine, and 1,6-hexamethylenediamine according to the present application to obtain the present application. In the following examples, the functional additives are a mixture of antioxidants, anti-yellowing agents, cohesion enhancers, and ultraviolet absorbers in a mass ratio of 1:1:1:1. However, those skilled in the art should understand that the examples are only used to explain the preferred implementation schemes given in the present application and are not intended to limit the present application. Under the guidance of the examples, those skilled in the art can also obtain the present application according to the ratio of the functional additives given in the present application.

[0029] Ripening: Ripening the polyurethane stock solution prepared in the chain extension step to a viscosity of 6000-10000 poise;

[0030] Spinning: The spinning solution prepared in the aging step is dry-spun to obtain low-melting-point spandex. Specifically, the spinning solution passes through a spinneret to obtain primary fibers, and the primary fibers pass through a spinning tunnel, are stretched, false-twisted, and oiled, and finally are wound and formed by a winder to obtain low-melting-point spandex.

[0031] According to the embodiments provided in the present application, some specific experiments have been conducted on the present application, namely, an embodiment of preparing low-melting-point spandex by the preparation method of low-melting-point spandex provided in the present application, and an embodiment of controlling the isocyanate index and -NH 2The molar ratio of -NCO to -NCO is shown in the following examples, and some comparative examples are given on this basis. From these examples and comparative examples, it can be seen that the scheme provided by the present application has achieved good results. It should be noted that the following examples are only used to illustrate the present application in detail and do not limit the scope of protection of the invention in any way.

[0032] Example 1

[0033] Step 1, slice preparation: according to mass measurement, 75 parts of 2000 molecular weight polybutylene adipate diol, 21 parts of MDI, and 4 parts of 1,4-butanediol are accurately measured by a metering pump, and then injected into a twin-screw extruder through a high-speed mixing head. The screw diameter of the twin-screw extruder is 65 mm, the screw aspect ratio is 35 mm, the screw extrusion temperature is 185°C, the temperature accuracy is controlled at ±2°C, the screw speed is 150rpm, the screw load is 75%, and then the slices are obtained by an underwater pelletizer;

[0034] Step 2, chain extension: The slices prepared in step 1 are passed through the finished material conveying system and the slice drying system to control the moisture content below 100 ppm, and then the slices are dissolved in DMAC to prepare a 35% polyurethane solution through a dissolving machine, and then a mixed amine solution prepared by ethylenediamine and diethylamine is added to carry out a chain extension reaction, wherein the mass ratio of ethylenediamine to diethylamine is 9:1, the concentration of the mixed amine solution is 8%, and -NH 2 The molar ratio of -NCO is 1.1:1; after chain extension, 1 part of functional additives consisting of antioxidant, anti-yellowing agent, cohesion enhancer and ultraviolet absorber are added to obtain a high-performance polyurethane stock solution, and the ratio of chain extender to terminator is 9.3;

[0035] Step 3, aging: Stir the polyurethane stock solution prepared in step 2 at 45° C. for 36 hours to achieve an apparent viscosity of 6730 poise;

[0036] Step 4, spinning: the spinning solution prepared in step 3 is passed through a spinneret to obtain primary fibers, the primary fibers pass through a spinning tunnel, are stretched, false twisted, and oiled, and are finally wound by a winder to form.

[0037] Embodiments 2 to 5

[0038] The difference between the preparation method of low melting point spandex in Examples 2 to 5 and Example 1 lies in the mass fractions of polyol, diphenylmethane diisocyanate (MDI), 1,4-butanediol, isocyanate index, and in the chain extension reaction step, -NH 2 Different from the parameters such as the molar ratio of -NCO, the control parameters of the twin-screw extruder, the moisture control, and the aging control parameters are the same as those in the embodiment. The specific control parameters of each step are shown in Table 1.

[0039] Comparative Examples 1 to 5

[0040] Comparative Example 1

[0041] The difference between Comparative Example 1 and Example 1 is that the steps of Comparative Example 1 are as follows:

[0042] Step 1: 75 parts of 2000 molecular weight polybutylene adipate diol, 21 parts of MDI, 4 parts of 1,4-butanediol, and an isocyanate index of 1.01 are accurately measured by a metering pump and injected into a twin-screw extruder through a high-speed mixing head. The screw diameter is 65 mm, the screw aspect ratio is 35, the melting temperature is 185° C., the temperature accuracy is controlled at ±2° C., the screw speed is 150 rpm, and the polymer chips are extruded through a screw machine with a screw load of 75%. The polymer chips are pelletized using an underwater pelletizer;

[0043] Step 2: The polymer chip pellets prepared in step 1 are conveyed to the single screw extruder through the finished material conveying system and the chip drying system, and the moisture is controlled below 100ppm. The functional additives are mixed at the feeding port, and the high-temperature melt is melted and matured in the screw machine. The extrusion temperature is 175°C, and the melt is conveyed to the melt metering pump to enter the spinning assembly in the spinning box. The spinning melt passes through the spinneret to obtain the primary fiber, and the primary fiber passes through the spinning channel, the oiling device, and finally the winding machine to obtain the low-melting spandex fiber. The mechanical properties of the obtained low-melting spandex fiber are tested, as shown in Table 2.

[0044] Comparative Example 2

[0045] The difference between Comparative Example 2 and Example 1 is that the isocyanate index is 1. Other control parameters are detailed in Table 1.

[0046] Comparative Example 3

[0047] The difference between Comparative Example 3 and Example 1 is that the isocyanate index is 1.5. Other control parameters are detailed in Table 1.

[0048] Comparative Example 4

[0049] The difference between Comparative Example 4 and Example 1 is that in the chain extension step, -NH 2 The molar ratio of -NCO is 1:1, and other control parameters are shown in Table 1.

[0050] Comparative Example 5

[0051] The difference between Comparative Example 4 and Example 1 is that in the chain extension step, -NH 2 The molar ratio of -NCO is 1:12, and other control parameters are shown in Table 1.

[0052] Table 1 Process control parameters of various embodiments and comparative examples

[0053]

[0054]

[0055] The spandex fibers prepared in the above examples and comparative examples were tested for melting point, fineness, breaking strength, breaking elongation and heat setting. The heat setting test method is as follows: 10 cm spandex yarn (L0) is drafted 300% (L1) at room temperature, heated at 170°C for 60s, and then the yarn is cooled at room temperature and its length is measured (L2). The heat setting rebound rate E% is calculated according to the following formula: E% = (L2-L0) / (L1-L0) × 100%. The test results are shown in Table 2.

[0056] Table 2: Spandex limit performance test table obtained in each embodiment and comparative example

[0057]

[0058] It can be seen from Table 2 that the melting points of the spandex fibers obtained in Examples 1 to 5 are between 156° C. and 169° C., which are relatively low. At the same time, the elongation at break of the spandex fibers obtained in Examples 1 to 5 is relatively high, between 503% and 547%; and the heat setting resilience is also relatively good, between 83% and 90%.

[0059] Comparative Example 1 prepares spandex fiber by polymerizing first and then dissolving and spinning the slices. The melting point of the spandex product obtained is significantly higher than that of Example 1, and the elongation at break is relatively small.

[0060] In comparative example 2, the isocyanate index is 1, and the resulting spandex product has generally low breaking strength, breaking elongation and heat-setting resilience.

[0061] In comparative example 3, the isocyanate index is 1.5, and the resulting spandex product has lower elongation at break and heat-setting resilience.

[0062] In Comparative Example 4, -NH 2 The molar ratio of -NCO to -NCO is 1:1, and the resulting spandex product has a higher melting point and a lower heat-setting resilience.

[0063] In Comparative Example 5, -NH 2 The molar ratio of -NCO to -NCO is 1:12, and the resulting spandex product has a higher melting point, poorer breaking strength, and lower heat-setting resilience.

[0064] It can be seen from the above embodiments and comparative examples that the low-melting-point spandex obtained in the present application can be melted at a relatively low temperature, which is conducive to combining with other fibers, making the fit between the fabric layers tighter and firmer.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing low melting point spandex, characterized in that: The method comprises the following steps: Slice preparation: polyol, diphenylmethane diisocyanate and 1,4-butanediol are fully mixed according to mass measurement and then extruded to obtain slices; Chain extension: dissolving the slices prepared in the slice preparation step in DMAC to prepare a polyurethane solution with a mass concentration of 35%, then adding a mixed amine solution to carry out a chain extension reaction, and adding a functional additive after chain extension to obtain a polyurethane stock solution; Ripening: Ripening the polyurethane stock solution prepared in the chain extension step to a viscosity of 6000-10000 poise; Spinning: The spinning solution prepared in the aging step is dry-spun to obtain low-melting-point spandex.

2. The method for preparing low melting point spandex according to claim 1, characterized in that: The polyol includes at least one of polyester polyol and polyether polyol.

3. The method for preparing low melting point spandex according to claim 1, characterized in that: The molecular weight of the polyol is 2,000.

4. The method for preparing low melting point spandex according to claim 2, characterized in that: The polyester polyol is polybutylene adipate diol with a molecular weight of 2000, and the polyether polyol is polytetrahydrofuran with a molecular weight of 2000.

5. The method for preparing low melting point spandex according to claim 1, characterized in that: In the slice preparation step, the isocyanate index of the diphenylmethane diisocyanate and the polyol in the raw material is 1.01 to 1.

4.

6. The method for preparing low melting point spandex according to claim 1, characterized in that: The mixed amine is a mixture of a chain extender and a terminator, wherein the chain extender is one or two amines selected from ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, 1,2-butylenediamine (1,2-diaminotoluene), 1,3-butylenediamine (1,3-diaminotoluene), 1,4-butylenediamine (1,4-diaminotoluene), pentanediamine, and 1,6-hexanediamine, and the terminator is diethylamine; the mixed amine is dissolved in a DMAC solution with a mass concentration of 7% to 8%.

7. The method for preparing low melting point spandex according to claim 1, characterized in that: In the chain extension reaction step, the molar ratio of -NH2 to -NCO is 1.01 to 1.1:

1.

8. The method for preparing low melting point spandex according to claim 6, characterized in that: The molar ratio of the chain extender to the terminator is 8 to 10:

1.

9. A low melting point spandex, characterized in that: The method is obtained by any one of claims 1 to 8.

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