Low-melting spandex and method for preparing the same

Abstract

The application discloses low-melting-point spandex and a preparation method thereof, and the method comprises the following steps: mixing polyhydric alcohol, diphenylmethane diisocyanate and 1,4-butanediol by mass, and then extruding and forming to obtain a slice; dissolving the slice in DMAC to prepare a polyurethane solution with a mass concentration of 35%, and then adding a mixed amine solution to perform a chain extension reaction; adding a functional additive after the chain extension to obtain a polyurethane stock solution; aging the polyurethane stock solution until the apparent viscosity reaches 6000-10000 poise; and performing dry spinning on the aged spinning stock solution to obtain low-melting-point spandex. The low-melting-point spandex obtained by the application can be set at a lower temperature, can avoid or reduce damage to the fabric caused by high-temperature setting, and can better maintain the original quality of the fabric.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of spandex preparation, and in particular relates to a low-melting-point spandex and a preparation method thereof. BACKGROUND

[0002] Spandex used in hygiene materials such as paper diapers needs to be bonded with non-woven fabric, and the spandex is required to have a low melting point to facilitate bonding of the spandex with the non-woven fabric.

[0003] The existing researches on spandex fiber products and spandex fiber production processes are all focused on how to improve the Vicat softening temperature of spandex fibers. Spandex fibers with high Vicat softening temperature have better heat resistance, but also have certain disadvantages, such as being not conducive to ironing, which limits the application range thereof.

[0004] Due to the limitation of spandex preparation process design, the spandex prepared by the existing process has the problems of high melting point, low elongation at break, and poor heat setting resilience, which leads to poor bonding ability of the obtained spandex fiber with other fabrics, and also causes damage to the fabric during high-temperature setting, affecting the hand feeling, strength and other properties of the fabric. SUMMARY

[0005] The technical problem to be solved by the present application is that the low-melting-point spandex prepared by the existing technology generally has poor bonding ability with other fabrics, high-temperature setting causes damage to the fabric, and affects the hand feeling, strength and other properties of the fabric.

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

[0007] Slice preparation: measure the polyol, diphenylmethane diisocyanate and 1,4-butanediol by mass, mix them thoroughly, and then extrude and form to obtain a slice;

[0008] Chain extension: dissolve the slice prepared in the slice preparation step in DMAC to configure a polyurethane solution with a mass concentration of 35%, then add a mixed amine solution for chain extension reaction, and after chain extension, add a functional additive to obtain a polyurethane stock solution;

[0009] Curing: cure the polyurethane stock solution prepared in the chain extension step to make its apparent viscosity reach 6000-10000 poise;

[0010] Spinning: dry spinning the spinning stock solution prepared in the curing step to obtain low-melting-point spandex.

[0011] The application firstly carries out prepolymerization to obtain a prepolymer and carries out slicing, and then carries out chain extension reaction on the prepolymer slice to obtain a polymerization stock solution, and the polymerization stock solution is spun after aging to obtain low-melting-point spandex. The low-melting-point spandex obtained by the application can be set at a relatively low temperature, which can avoid or reduce the damage to the fabric caused by high-temperature setting, can better maintain the original quality of the fabric, make the fit between the layers of the fabric more closely and firmly, improve the overall stability and durability of the fabric product, and solve the problem of poor fit between the low-melting-point spandex prepared by the prior art and other fabrics.

[0012] As an optional solution of the polyol in the slicing preparation step, the polyol includes at least one of a polyester polyol and a polyether polyol.

[0013] As an optional solution of the polyol in the slicing preparation step, the molecular weight of the polyol is 2000.

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

[0015] As a preferred selection of the slicing preparation step, in the slicing preparation step, the isocyanate index of the diphenylmethane diisocyanate in the raw material and the polyol is 1.01-1.4.

[0016] The isocyanate index represents the equivalent ratio of isocyanate to polyol. The isocyanate index value of the application is slightly greater than 1, because during the polymerization process, due to the presence of trace amount of water in the system and the interaction between isocyanate groups, the isocyanate groups are relatively lost more, so during synthesis, the isocyanate group is usually slightly excessive, which can achieve the maximum degree of chain extension of the molecule.

[0017] As a selection of the mixed amine 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-propanediamine, 1,3-propanediamine, 1,2-butanediamine (1,2-diaminotoluene), 1,3-butanediamine (1,3-diaminotoluene), 1,4-butanediamine (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%-8%.

[0018] As a selection of the chain extension step, the molar ratio of -NH2 to -NCO after the chain extension reaction is 1.01-1.1.

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

[0020] Alternatively, in the slicing step, the mixing and extruding is performed in a twin-screw extruder.

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

[0022] The application has the following advantages:

[0023] The preparation method of the low-melting-point spandex provided by the application first slices the prepolymer, then dissolves the slice to perform chain extension to obtain a polymer stock solution, and then performs spinning after aging the polymer stock solution. The preparation method of the low-melting-point spandex adopted by the application does not need high-temperature melting and the like, the overall reaction process is short, and the investment density is reduced. In addition, the raw materials of the application are flexible and variable, and polyester / polyether polyols can be used.

[0024] The low-melting-point spandex obtained by the application can be melted at a relatively low temperature and combined with other fibers, so that the fit between the layers of the fabric is more compact and firm, and the overall stability and durability of the fabric product are improved. DETAILED DESCRIPTION

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

[0026] The application provides a preparation method of a low-melting-point spandex, including the following steps:

[0027] Slicing preparation: a polyol, diphenyl methane diisocyanate, and 1,4-butanediol are fully mixed and extruded to form a slice; the polyol can be at least one of a polyester polyol and a polyether polyol, for example, the polyester polyol is 2000 molecular weight polybutylene adipate diol (PBA), and the polyether polyol is 2000 molecular weight polytetramethylene glycol (PTMG), or a mixture of a polyester polyol and a polyether polyol, and the isocyanate index is 1.01-1.4; in this step, the equipment for mixing and extruding the polyol, diphenyl methane diisocyanate, and 1,4-butanediol is a twin-screw extruder; in the specific embodiments described below, the twin-screw extruder has a screw diameter of 65 mm, a screw length-diameter ratio of 35 mm, a screw extrusion temperature of 185°C, a temperature precision control of ±2°C, a screw rotation speed of 150 rpm, and a screw load of 75%;

[0028] Chain extension: the chips prepared in the chip preparation step are dissolved in DMAC to prepare a polyurethane solution with a mass concentration of 35%, and then a mixed amine solution is added for chain extension reaction. After chain extension, a functional additive is added 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-propanediamine, 1,3-propanediamine, 1,2-butanediamine (1,2-diaminotoluene), 1,3-butanediamine (1,3-diaminotoluene), 1,4-butanediamine (1,4-diaminotoluene), pentanediamine, 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%. The molar ratio of the chain extender to the terminator is 8-10:1; in the chain extension step, the molar ratio of -NH2 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 examples is a mixed amine prepared from ethylenediamine and diethylamine, those skilled in the art should understand that the examples are only used to explain the preferred embodiments given in the present application and do not limit the present application. Those skilled in the art can also obtain the present application according to any type of amine selected from 1,2-propanediamine, 1,3-propanediamine, 1,2-butanediamine (1,2-diaminotoluene), 1,3-butanediamine (1,3-diaminotoluene), 1,4-butanediamine (1,4-diaminotoluene), pentanediamine, 1,6-hexanediamine under the inspiration of the examples given in the present application. The functional additive in the following examples is a mixture composed of an antioxidant, an anti-yellowing agent, a cohesion enhancer, and an ultraviolet absorber with a mass ratio of 1:1:1:1, but those skilled in the art should understand that the examples are only used to explain the preferred embodiments given in the present application and do not limit the present application. Those skilled in the art can also obtain the present application according to the given ratio of the functional additive under the inspiration of the examples given in the present application.

[0029] Maturation: the polyurethane stock solution prepared in the chain extension step is matured to make its apparent viscosity reach 6000-10000 poise;

[0030] Spinning: the spinning stock solution prepared in the maturation step is subjected to dry spinning to obtain low-melting-point spandex. Specifically, the spinning stock solution passes through a spinneret to obtain a nascent fiber, the nascent fiber passes through a spinning duct, is subjected to stretching, false twisting, and oiling device, and is finally wound into shape by a winding machine to obtain low-melting-point spandex.

[0031] According to the embodiments provided in the present application, some specific experiments have been made, i.e. the preparation of low-melting-point spandex by the preparation method of low-melting-point spandex provided in the present application, including the embodiment of controlling the isocyanate index and the embodiment of controlling the molar ratio of -NH2 and -NCO, on the basis of which, some comparative examples are given. From these examples and comparative examples, it can be seen that the scheme provided in 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 protection scope of the invention in any way.

[0032] Example 1

[0033] Step one, slice preparation: according to the mass, 75 parts of polybutylene adipate glycol with a molecular weight of 2000, 21 parts of MDI, and 4 parts of 1,4-butanediol are weighed, and the material with an isocyanate index of 1.01 is accurately metered by a metering pump and then injected into a double screw extruder through a high-speed mixing head. The screw diameter of the double screw extruder is 65 mm, the screw length-diameter ratio is 35 mm, the screw extrusion temperature is 185°C, the temperature precision is controlled within ±2°C, the screw speed is 150 rpm, and the screw load is 75%. Then, the slice is prepared by underwater pelletizer;

[0034] Step two, chain extension: the slice prepared in step one is passed through a finished product material conveying system, a slice drying system to control the moisture content below 100 ppm, and a dissolving machine to dissolve the slice in DMAC to configure a 35% polyurethane solution. Then, a mixed amine solution prepared by adding ethylenediamine and diethylamine is added for chain extension reaction, wherein the mass ratio of ethylenediamine and diethylamine is 9:3, the concentration of the mixed amine solution is 8%, and the molar ratio of -NH2 to -NCO is 1.1:1. After chain extension, 1 part of functional additives composed of antioxidants, anti-yellowing agents, cohesion enhancers, and ultraviolet absorbers is added to obtain a high-performance polyurethane stock solution, and the ratio of chain extender to terminator is 9.3;

[0035] Step three, aging: the polyurethane stock solution prepared in step two is aged at 45°C for 36 hours with stirring, and the apparent viscosity is 6730 poise;

[0036] Step four, spinning: the spinning stock solution prepared in step three is passed through a spinneret to obtain a nascent fiber, which is passed through a spinning duct, stretched, false twisted, and oiled, and finally wound into a shape by a winding machine.

[0037] Examples 2-5

[0038] The difference between Examples 2-5 and the preparation method of the low-melting-point spandex of Example 1 lies in the mass fraction of the polyol, diphenyl methane diisocyanate (MDI), 1,4-butanediol, the isocyanate index, the molar ratio of -NH2 to -NCO in the chain extension reaction step, and other parameters. The control parameters of the twin-screw extruder, moisture control, and curing control parameters are the same as in the example, and the specific control parameters of each step are shown in Table 1.

[0039] Comparative Examples 1-5

[0040] Comparative Example 1

[0041] The difference between Comparative Example 1 and Example 1 lies in the following steps of Comparative Example 1:

[0042] Step one, measure by mass fraction, 75 parts of polybutylene adipate glycol with a molecular weight of 2000, 21 parts of MDI, and 4 parts of 1,4-butanediol, with an isocyanate index of 1.01, accurately measured by a metering pump, and then injected into a twin-screw extruder through a high-speed mixing head. The screw diameter is 65 mm, the screw length-diameter ratio is 35, the melting temperature is 185°C, the temperature precision is controlled within ±2°C, the screw speed is 150 rpm, the extrusion is carried out through the screw machine, the screw load is 75%, and the polymer chip granules are prepared by using an underwater pelletizer.

[0043] Step two, the polymer chip granules prepared in step one are transported through a finished material conveying system, dried by a chip drying system, and the moisture is controlled below 100 ppm, and then transported to a single-screw extruder. The high-temperature melt after mixing the functional additives at the feeding port is melted and cured in the screw machine, the extrusion temperature is 175°C, and the melt is transported to the spinning assembly in the spinning box through a melt metering pump. The spinning melt passes through the spinneret to obtain the primary fiber, the primary fiber passes through the spinning duct, is oiled by the oiling device, and is finally wound into a low-melting-point spandex fiber by the winding machine. The obtained low-melting-point spandex fiber is subjected to mechanical property detection, and the details are shown in Table 2.

[0044] Comparative Example 2

[0045] The difference between Comparative Example 2 and Example 1 lies in that the isocyanate index is 1, and other control parameters are shown in Table 1.

[0046] Comparative Example 3

[0047] The difference between Comparative Example 3 and Example 1 lies in that the isocyanate index is 1.5, and other control parameters are shown in Table 1.

[0048] Comparative Example 4

[0049] The difference between Comparative Example 4 and Example 1 lies in that the molar ratio of -NH2 to -NCO in the chain extension step is 1:1, and other control parameters are shown in Table 1.

[0050] Comparative Example 5

[0051] Comparative Example 4 differs from Example 1 in that the molar ratio of -NH2 to -NCO in the chain extension step is 1:1.12, and other control parameters are as shown in Table 1.

[0052] Table 1. Process control parameters of each example and comparative example

[0053]

[0054] 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 was as follows: 10 cm of spandex yarn (L0) was drawn by 300% (L1) at room temperature, and then heated at 170°C for 60 s, and then the length of the yarn (L2) was measured after the yarn was cooled at room temperature. The heat setting recovery rate E% was calculated according to the following formula: E% = (L2-L0) / (L1-L0) x 100%, and the test results are shown in Table 2.

[0055] Table 2. Performance test table of spandex obtained in each example and comparative example

[0056]

[0057] As can be seen from Table 2, the melting point of the spandex fibers obtained in Examples 1-5 is between 156°C and 169°C, the melting point is relatively low, at the same time, the breaking elongation of the spandex fibers obtained in Examples 1-5 is relatively high, between 503% and 547%, and the heat setting recovery rate is also good, between 83% and 90%.

[0058] Comparative Example 1 uses the method of polymerization first, then pelletization and dissolution, and then spinning to prepare spandex fibers, and the melting point of the obtained spandex product is significantly higher than that of Example 1, and the breaking elongation is relatively small.

[0059] Comparative Example 2 has an isocyanate index of 1, and the breaking strength, breaking elongation, and heat setting recovery rate of the obtained spandex product are generally low.

[0060] Comparative Example 3 has an isocyanate index of 1.5, and the breaking elongation and heat setting recovery rate of the obtained spandex product are relatively low.

[0061] In Comparative Example 4, the molar ratio of -NH2 to -NCO is 1:1, and the melting point of the obtained spandex product is relatively high, and the heat setting recovery rate is relatively low.

[0062] In Comparative Example 5, the molar ratio of -NH2 to -NCO is 1:1.12, and the melting point of the obtained spandex product is relatively high, the breaking strength is relatively poor, and the heat setting recovery rate is relatively low.

[0063] It can be seen from the above examples and comparative examples that the low-melting point spandex obtained by the application can be melted at a lower temperature, which is beneficial to the combination with other fibers, and makes the fit between the layers of the fabric more close and firm.

[0064] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the application, but not to limit them; although the application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A method for producing low-melting spandex characterized by, The method comprises the following steps: Slice preparation: after mixing the polyol, diphenyl methane diisocyanate and 1,4-butanediol by mass, extruding and molding to obtain a slice; in the slice preparation step, the isocyanate index of the diphenyl methane diisocyanate in the raw material and the polyol is 1.01-1.4; Chain extension: dissolving the slice prepared in the slice preparation step in DMAC to configure a polyurethane solution with a mass concentration of 35%, then adding a mixed amine solution for chain extension reaction, adding a functional additive after chain extension to obtain a polyurethane stock solution; in the chain extension reaction step, the molar ratio of -NH2 to -NCO is 1.01-1.1:1; Maturation: maturing the polyurethane stock solution prepared in the chain extension step to make its apparent viscosity reach 6000-10000 poise; Spinning: dry spinning the spinning stock solution prepared in the maturation step to obtain low-melting point spandex.

2. The method for preparing low-melting-point spandex according to claim 1, characterized in that, The polyol comprises at least one of a polyester polyol and a 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 2000.

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

5. 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 of 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%-8%.

6. The method for preparing low-melting-point spandex according to claim 5, characterized in that, The molar ratio of the chain extender to the terminator is 8-10:

1.

7. A low melt spandex characterized in that, Obtained by the preparation method of any one of claims 1-6. Obtained by the preparation method of any one of claims 1-6.

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