Ultralow-temperature setting melt-spun spandex fiber and preparation method thereof

Abstract

The invention discloses an ultralow-temperature setting melt-spun spandex fiber and a preparation method thereof, and belongs to the technical field of high polymer materials, the ultralow-temperature setting melt-spun spandex fiber is prepared from PHA and PPA of high-molecular-weight and low-crystallinity polyester polyol (the number-average molecular weight is 3000-4000 g / mol), a mixed chain extender mainly comprising 1, 4-butanediol, 4, 4, 6-tetramethyl-1, 3-pentanediol, 1, 4, 6-tetramethyl-1, 3-pentanediol, 1, 4, 6-tetramethyl-1, 3-pentanediol, the preparation method comprises the following steps: by taking diisocyanate mixed by 4, 4 '-diphenylmethane diisocyanate and hexamethylene diisocyanate as a raw material, carrying out a twin-screw bulk polymerization process to obtain an ultralow-melting-point melt-spun spandex slice; the ultra-low-temperature shaped melt-spun spandex fiber is prepared by taking the spandex as a main material and a cross-linking agent as an auxiliary material through a melt spinning process, and the shaping temperature of the ultra-low-temperature shaped melt-spun spandex fiber is 100-105 DEG C, so that the requirement of the polyethylene fiber and the polypropylene fiber on the shaping temperature can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to an ultra-low temperature setting melt-spun spandex fiber and a preparation method thereof. Background Art

[0002] Spandex is a polyurethane elastic fiber with the characteristics of high elongation at break, low modulus and high elastic recovery rate. It is usually blended with polyester, nylon, cotton, silk and wool. A small amount of addition (1-10%) can achieve excellent elasticity, so it enjoys the reputation of "fabric MSG".

[0003] Heat setting is essential for fabric finishing, significantly impacting the fabric's dimensional stability, surface smoothness, and tactile feel. Setting temperature is a key factor influencing the effectiveness of the setting process. Different materials have varying heat resistances, necessitating different setting temperatures. Conventional spandex has a setting temperature above 195°C, making it suitable for heat-resistant synthetic fibers like polyester and nylon, as well as natural fibers like cotton and wool. However, it is not suitable for heat-sensitive fibers like polyethylene and polypropylene, as these fibers must be heat-set at a strictly controlled temperature between 100°C and 105°C; excessively high temperatures will cause them to melt.

[0004] Currently, there is no spandex product on the market that can match the setting temperature of polyethylene and polypropylene, so there is an urgent need to develop a spandex fiber with ultra-low temperature setting (setting temperature at 100-105°C). Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a melt-spun spandex fiber with ultra-low temperature setting and a preparation method thereof. The melt-spun spandex fiber provided by the present invention has a high heat setting efficiency at a temperature of 100-105°C.

[0006] To achieve the above objectives, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing ultra-low temperature setting melt-spun spandex fiber, comprising the following steps:

[0008] The polyester polyol, diisocyanate and small molecule diol chain extender are heated and kept warm respectively, and the above raw materials are injected into the injection port of a twin-screw extruder, and a catalyst is added to react and polymerize. The melt-spun spandex chips are obtained by underwater pelletizing and aging. The DSC melting point of the melt-spun spandex chips is 100° C. to 105° C.

[0009] The melt-spun spandex chips are fed into the feed port of a twin-screw extruder, a cross-linking agent is injected into the end of the screw, and ultra-low-temperature-setting melt-spun spandex fibers are produced by spinning, with the setting temperature being 100-105° C. Furthermore, the molar ratio of the polyester polyol, the small molecule diol chain extender, and the diisocyanate is (0.18-0.23):(0.78-1.59):(1.07-1.84).

[0010] Furthermore, the polyester polyol is selected from at least one of poly(1,6-hexanediol adipate) polyol (PHA) and poly(1,5-pentanediol adipate) polyol (PPA).

[0011] Furthermore, the number average molecular weight of the poly(1,6-hexanediol adipate) polyol and the poly(1,5-pentanediol adipate) polyol are both 3000-4000 g / mol, the acid value is ≤0.5 mg KOH / g, and the water content is ≤100 ppm.

[0012] Furthermore, the diisocyanate is a mixture of aromatic 4,4'-diphenylmethane diisocyanate (MDI) and aliphatic hexamethylene diisocyanate (HDI), wherein the molar proportion of MDI is 40 to 90%.

[0013] Furthermore, the small molecule diol chain extender is selected from at least one of 1,4-butanediol (BDO), 1,6-hexanediol (HDO), and 1,5-pentanediol, and the molar proportion of 1,4-butanediol in the small molecule diol chain extender is 50-80%.

[0014] Furthermore, the catalyst is selected from organotin catalysts;

[0015] And / or, the added amount of the catalyst is 0.001 to 0.002% of the mass of the melt-spun spandex chips.

[0016] Furthermore, the organotin catalyst is selected from dibutyltin dilaurate (T12).

[0017] Furthermore, the crosslinking agent is a substance having a terminal NCO group, which is polymerized from poly(1,6-hexanediol adipate) polyol and hexamethylene diisocyanate, and has an NCO content of 5 to 10%.

[0018] And / or, the amount of the cross-linking agent is 5-12% of the mass of the melt-spun spandex chips.

[0019] Furthermore, the spinning steps are as follows: the melt is mixed evenly in a static mixer and then enters a metering pump, the filter screen removes gel impurities, the filament melt is ejected through a spinneret, and then sequentially undergoes side-blown cooling, oiling, winding and aging.

[0020] The present invention also provides a melt-spun spandex fiber prepared according to the preparation method and having an ultra-low temperature setting temperature of 100-105°C.

[0021] The present invention also provides the use of the ultra-low temperature setting melt-spun spandex fiber in the preparation of spandex products having a setting temperature matching that of ethylene and / or polypropylene.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects:

[0023] (1) The present invention uses high molecular weight and low crystallinity polyester polyol (polyadipate-1,6-hexanediol polyol (PHA) and polyadipate-1,5-pentanediol polyol (PPA) with a number average molecular weight of 3000-4000 g / mol), a mixed chain extender mainly composed of 1,4-butanediol, and a diisocyanate mixed with 4,4'-diphenylmethane diisocyanate and hexamethylene diisocyanate as raw materials, and obtains an ultra-low melting point melt-spun spandex chip through a twin-screw bulk polymerization process; using the PHA as the main ingredient and a special cross-linking agent as the auxiliary material, ultra-low temperature setting melt-spun spandex fiber is obtained through a melt spinning process. Among them, the introduction of high molecular weight, low crystallinity polyester polyols can reduce the DSC melting point of melt-spun spandex chips while providing good resilience. Combined with mixed chain extension technology such as 1,4-butanediol and 1,6-hexanediol and the introduction of MDI / HDI mixed isocyanate, the DSC melting point of melt-spun spandex chips can be further reduced by breaking the crystallinity of the hard segment and reducing the rigidity. Cross-linking agents are one of the important raw materials for preparing melt-spun spandex. They can improve the fluidity of the melt and compensate for the molecular chain breakage caused by screw shearing, playing a key role in improving spinning efficiency and mechanical properties. The inventors found that the structural composition of the cross-linking agent has a significant impact on the heat setting temperature of melt-spun spandex fibers. Through a large number of experimental tests, they screened out a special cross-linking agent suitable for low-melting-point spandex fibers. This cross-linking agent is synthesized using HDI and low-crystallinity polyester polyols. It has good fluidity and a mild reaction. The lower crystallinity ensures that the melt-spun spandex fibers have a lower heat setting temperature.

[0024] (2) The ultra-low temperature setting melt-spun spandex fiber prepared by the present invention has a setting temperature between 100 and 105°C, which can meet the setting temperature requirements of polyethylene and polypropylene.

[0025] (3) The ultra-low temperature shaped melt-spun spandex fiber prepared by the present invention has excellent resilience and can meet the requirements of FZ / T54010-2014 spandex filament.

[0026] (4) The preparation method of the present invention has the advantages of mature technology, simple process and high production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0028] Figure 1 This is a physical picture of the ultra-low temperature set melt-spun spandex fiber prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0030] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0031] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0032] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0033] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0034] An embodiment of the present invention provides a method for preparing ultra-low temperature set melt-spun spandex fiber, comprising the following steps:

[0035] The polyester polyol, diisocyanate and small molecule diol chain extender are heated and kept warm respectively, and the above raw materials are injected into the injection port of the twin-screw extruder, and a catalyst is added at the same time. The raw materials react and polymerize under the shearing action of the twin-screw extruder, and the melt-spun spandex chips are obtained after underwater pelletization and aging. The DSC melting point of the melt-spun spandex chips is 100°C to 105°C.

[0036] The melt-spun spandex chips are injected into the feed port of the twin-screw extruder, and the cross-linking agent is injected at the end of the screw. The melt is mixed evenly in a static mixer and then enters the metering pump. The filter removes gel impurities and the filament melt is ejected through the spinneret. It is then cooled by side air, oiled, wound and aged in sequence to produce ultra-low temperature set melt-spun spandex fiber, whose setting temperature is 100-105°C.

[0037] In an embodiment of the present invention, the molar ratio of polyester polyol, small molecule diol chain extender and diisocyanate is (0.18-0.23):(0.78-1.59):(1.07-1.84).

[0038] In an embodiment of the present invention, the polyester polyol is selected from at least one of poly(1,6-hexanediol adipate) polyol (PHA) and poly(1,5-pentanediol adipate) polyol (PPA).

[0039] In the embodiment of the present invention, the number average molecular weight of poly(1,6-hexanediol adipate) polyol and poly(1,5-pentanediol adipate) polyol are both 3000 to 4000 g / mol.

[0040] In an embodiment of the present invention, the diisocyanate is a mixture of aromatic 4,4'-diphenylmethane diisocyanate (MDI) and aliphatic hexamethylene diisocyanate (HDI), wherein the molar proportion of MDI is 40 to 90%.

[0041] In an embodiment of the present invention, the small molecule diol chain extender is selected from at least one of 1,4-butanediol (BDO), 1,6-hexanediol (HDO), and 1,5-pentanediol, and the molar proportion of 1,4-butanediol in the small molecule diol chain extender is 50-80%. For example, the small molecule diol chain extender is selected from BDO and HDO, and the molar proportion of BDO in the small molecule diol chain extender is 50-80%. For another example, the small molecule diol chain extender is selected from BDO and 1,5-pentanediol, and the molar proportion of BDO in the small molecule diol chain extender is 50-80%.

[0042] In an embodiment of the present invention, the catalyst is selected from an organotin catalyst, and the amount of the catalyst added is 0.001 to 0.002% of the mass of the melt-spun spandex chips. Exemplarily, the organotin catalyst is selected from dibutyltin dilaurate (T12).

[0043] In an embodiment of the present invention, the crosslinking agent is a substance with terminal NCO groups synthesized by polymerization of poly(1,6-hexanediol adipate) polyol and hexamethylene diisocyanate, and its NCO content is 5-10%. The amount of the crosslinking agent is 5-12% of the mass of the melt-spun spandex chips.

[0044] In an embodiment of the present invention, the hard segment content of the melt-spun spandex chips (the sum of the mass of the chain extender and the isocyanate / the mass of the spandex chips) is 29-45%, the temperature of the twin-screw extruder is 120°C to 220°C, preferably 180-200°C; the rotation speed is 80-130 r / min, and the aging temperature is 55-75°C.

[0045] In the embodiments of the present invention, the preparation method of poly(1,6-hexanediol adipate) polyol (PHA) and poly(1,5-pentanediol adipate) polyol (PPA) is not limited, and they can be synthesized according to the polyester polyol synthesis process disclosed in the industry, and the number average molecular weight is required to be 3000-4000 g / mol, the acid value is ≤0.5 mg KOH / g, and the moisture content is ≤100 ppm.

[0046] In an embodiment of the present invention, during side-blowing cooling, the temperature of the side-blowing cooling air is 15-35° C., and the wind speed is 3.5-6 m / s.

[0047] In an embodiment of the present invention, the winding speed is 800-1000 m / min.

[0048] An embodiment of the present invention further provides a melt-spun spandex fiber prepared according to the above preparation method and having an ultra-low temperature setting temperature of 100-105°C.

[0049] The ultra-low temperature setting melt-spun spandex fiber provided in the embodiment of the present invention can be used to prepare spandex products with a setting temperature matching that of polyethylene and / or polypropylene.

[0050] Unless otherwise specified, the room temperature in the present invention is 25±2°C.

[0051] All raw materials used in the examples of the present invention are commercially available.

[0052] In the following examples and comparative examples of the present invention, "parts" are parts by mass.

[0053] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0054] The spinning oil used in the examples and comparative examples of the present invention is DELION 342 (purchased from Takemoto Oil & Fats Co., Ltd., Japan).

[0055] The performance testing method used in the present invention is as follows:

[0056] The mechanical properties and melting point of melt-spun spandex chips were tested with reference to the standard "T / C CFA0103-2018 Fiber-grade polyurethane chips".

[0057] The mechanical properties of melt-spun spandex fibers were tested with reference to standard FZ / T 54010-2014.

[0058] Melt-spun spandex fiber setting efficiency test: The melt-spun spandex fiber was drafted twice (from 150mm to 300mm) and fixed. It was placed in a 100-105℃ forced air drying oven for 2 minutes, then the draft was removed. The fiber was placed in a 23℃*50%RH environment for cooling for 24 hours. The length after setting was measured. The setting efficiency was calculated based on the initial length, the length after drafting, and the length after setting:

[0059] Setting efficiency (%) = (length after setting - initial length) / (length after stretching - initial length) * 100%.

[0060] The technical solution of the present invention is further illustrated by the following examples.

[0061] Example 1

[0062] A melt-spun spandex fiber with ultra-low temperature setting, the preparation method is as follows:

[0063] Step 1: Preparation of poly(1,6-hexanediol adipate) polyol (PHA) with a number average molecular weight of 3000 g / mol

[0064] Adipic acid and hexanediol were added to a reactor equipped with a splitter, a condenser and a distillation receiver in a molar ratio of 1:1.08. After heating and melting, stirring was started and the reaction was carried out at 140°C for 1 hour. The reactor was heated to 220°C and the temperature of the top of the fractionating tower was controlled at 100°C. When the acid value reached 10 mg KOH / g, vacuum was started for 4 hours until the acid value dropped below 0.5 mg KOH / g. The reaction was stopped and the hydroxyl value of the sample was analyzed to be 37.4 mg KOH / g. The number average molecular weight was calculated to be 3000 g / mol. Nitrogen protection was added and the temperature was lowered to 120°C to obtain polyadipate-1,6-hexanediol ester polyol with a number average molecular weight of 3000 g / mol and a moisture content of 100 ppm. It was recorded as PHA-3000 and set aside.

[0065] Step 2: Preparation of ultra-low melting point melt-spun spandex chips

[0066] PHA-3000 was melted at 100°C for 1 hour, 1,4-butanediol (BDO) and 1,6-hexanediol (HDO) were melted at 65°C for 1 hour, and MDI (diphenylmethane diisocyanate) was melted at 55°C for 1 hour. HDI (hexamethylene diisocyanate) was heated at 50°C for 1 hour. The above materials were injected into the injection port of a twin-screw extruder in the following ratios: the molar ratios of PHA-3000, BDO, HDO, MDI and HDI were 0.23:0.39:0.39:0.43:0.64, respectively. At the same time, an organotin catalyst T12 was injected into the injection port at a level of 0.001% of the mass of the melt-spun spandex chips. The temperature of the twin-screw extruder was set at 120°C and the speed was set at 80 r / min. Melt-spun spandex chips were obtained by an underwater pelletizer and transferred to a 55°C drying barrel for aging to obtain ultra-low melting point melt-spun spandex chips. The hard segment content of the obtained chips was 29% and the R value was 1.05.

[0067] Step 3: Preparation of ultra-low melting point crosslinker

[0068] 9 parts of PHA-3000 were added to a reactor, dehydrated at 100°C and a vacuum degree of 0 kPa for 1 hour, nitrogen was added as a protective atmosphere, and the temperature was cooled to 60°C. 1 part of hexamethylene diisocyanate was added, and the reaction was stirred under nitrogen protection for 1 hour. The temperature was then raised to 90°C to obtain an ultra-low melting point crosslinking agent with an NCO content of 5%.

[0069] Step 4: Preparation of ultra-low melting point melt-spun spandex fiber

[0070] The ultra-low melting point melt-spun spandex slices fully matured in step 2 are injected into the feed port of the screw extruder, and the ultra-low melting point cross-linking agent prepared in step 3 is injected into the end of the screw. The amount of the ultra-low melting point cross-linking agent added is 12% of the mass of the ultra-low melting point melt-spun spandex slices. The temperature of the screw extruder is set to 180°C. The melt is mixed evenly in a static mixer and then enters a metering pump. The filter screen removes gel impurities and the filament melt is ejected through a spinneret. The filament melt is then cooled by side blowing, oiled and wound in sequence to obtain a spandex cake, wherein the side blowing temperature is 15°C, the wind speed is 6m / s, and the winding speed is 800m / min. The obtained cake is naturally matured at 30°C to obtain an ultra-low temperature set melt-spun spandex fiber finished product with a fineness of 30D. The actual picture of the ultra-low temperature set melt-spun spandex fiber prepared in this embodiment is shown in Figure 1 .

[0071] Example 2

[0072] A melt-spun spandex fiber with ultra-low temperature setting, the preparation method is as follows:

[0073] Step 1: Preparation of polyester polyol PPA-4000

[0074] Adipic acid and 1,5-pentanediol were added to a reactor equipped with a splitter, a condenser and a distillation receiver in a molar ratio of 1:1.06. After heating and melting, stirring was started and the reaction was carried out at 145°C for 2 hours. The reactor was quickly heated to 226°C and the temperature of the top of the fractionating tower was controlled at 120°C. When the acid value reached 13 mg KOH / g, vacuum was started for 4 hours until the acid value dropped below 0.5 mg KOH / g. The reaction was stopped and the hydroxyl value of the sample was analyzed to be 28 mg KOH / g. The number average molecular weight was calculated to be 4000 g / mol. Nitrogen protection was added and the temperature was lowered to 120°C to obtain polyadipate-1,5-pentanediol ester polyol with a number average molecular weight of 4000 g / mol and a moisture content of 80 ppm, which was recorded as PPA-4000 and set aside.

[0075] Step 2: Preparation of ultra-low melting point melt-spun spandex chips

[0076] PPA-4000 was melted at 120°C for 3 hours, BDO and 1,5-pentanediol (PDO) were melted at 85°C for 3 hours, MDI was melted at 65°C for 5 hours, and HDI was melted at 60°C for 2 hours. These materials were injected into the injection port of a twin-screw extruder in the following molar ratios: PPA-4000, BDO, PDO, MDI, and HDI (0.18:1.27:0.32:1.66:0.18, respectively). Simultaneously, an organotin catalyst, T12, was injected into the injection port at a level of 0.002% of the mass of the melt-spun spandex chips. The temperature of the twin-screw extruder was set at 200°C and the speed was set at 130 r / min. Melt-spun spandex chips were obtained by an underwater pelletizer and then transferred to a 75°C drying barrel for aging to obtain ultra-low melting point melt-spun spandex chips. The hard segment content of the obtained chips was 45% and the R value was 1.05.

[0077] Step 3: Preparation of ultra-low melting point crosslinker

[0078] 4 parts of PPA-4000 were added to a reactor, dehydrated at 120°C and a vacuum of 5 kPa for 2 hours, nitrogen was added as a protective atmosphere, the temperature was cooled to 70°C, 1 part of hexamethylene diisocyanate was added, and the reaction was stirred for 3 hours under nitrogen protection. The temperature was raised to 100°C to obtain an ultra-low melting point crosslinking agent with an NCO content of 10%.

[0079] Step 4: Preparation of ultra-low melting point melt-spun spandex fiber

[0080] The ultra-low melting point melt-spun spandex chips fully matured in step 2 are injected into the feed port of a screw extruder, and the ultra-low melting point cross-linking agent prepared in step 3 is injected at the end of the screw. The amount of the ultra-low melting point cross-linking agent added is 5% of the mass of the ultra-low melting point melt-spun spandex chips. The temperature of the screw extruder is set to 220° C. The melt is uniformly mixed in a static mixer and then enters a metering pump. A filter screen is used to remove gel impurities, and the filament melt is ejected through a spinneret. The filament melt is then sequentially cooled by side-blowing, oiled, and wound to obtain a spandex cake, wherein the side-blowing temperature is 35° C., the wind speed is 3.5 m / s, and the winding speed is 1000 m / min. The obtained cake is naturally matured at 30° C. to obtain an ultra-low temperature-set melt-spun spandex fiber product with a fineness of 30D.

[0081] Example 3

[0082] A melt-spun spandex fiber with ultra-low temperature setting, the preparation method is as follows:

[0083] Step 1: Preparation of polyester polyols PHA-3500 and PPA-3800

[0084] Adipic acid and 1,6-hexanediol were added to a reactor equipped with a splitter, a condenser, and a distillation receiver in a molar ratio of 1:1.07. The mixture was heated to melt and then stirred. The mixture was reacted at 150° C. for 1-2 hours. The reactor was rapidly heated to 230° C. The temperature at the top of the fractionating tower was controlled at 110° C. When the acid value reached 11 mg KOH / g, vacuum was applied for 4 hours until the acid value dropped below 0.5 mg KOH / g. The reaction was then stopped. The hydroxyl value of the sample was analyzed to be 32 mg KOH / g. The number average molecular weight was calculated to be 3500 g / mol. Nitrogen protection was added and the temperature was lowered to 120° C. to obtain poly(1,6-hexanediol adipate) polyol with a number average molecular weight of 3500 g / mol and a moisture content of 90 ppm, which was designated as PHA-3500 and set aside.

[0085] Adipic acid and 1,5-pentanediol were added to a reactor equipped with a splitter, a condenser, and a distillation receiver in a molar ratio of 1:1.06. The mixture was heated to melt and then stirred. The mixture was reacted at 140°C for 1.5 hours. The reactor was rapidly heated to 220°C, and the temperature at the top of the fractionating tower was controlled at 110°C. When the acid value reached 13 mg KOH / g, vacuum was applied for 4 hours until the acid value dropped below 0.5 mg KOH / g. The reaction was then stopped. The hydroxyl value of the sample was analyzed and found to be 29.5 mg KOH / g. The number average molecular weight was calculated to be 3800 g / mol. Nitrogen protection was added and the temperature was lowered to 120°C to obtain poly (1,5-pentanediol adipate) polyol with a number average molecular weight of 3800 g / mol, which was recorded as PPA-3800 and set aside.

[0086] Step 2: PHA-3500 and PPA-3800 were heated and melted at 110°C for 2 hours, BDO and HDO were heated and melted at 75°C for 2 hours, MDI was heated and melted at 60°C for 2 hours, and HDI was heated and melted at 55°C for 1.5 hours. The above materials were injected into the injection port of a twin-screw extruder in the following ratio: the molar ratio of PHA-3500, PPA-3800, BDO, HDO, MDI and HDI was 0.1:0.1:0.72:0.39:0.82:0.55, respectively. At the same time, an organotin catalyst T12 was injected into the injection port at a concentration of 0.0015% of the mass of the melt-spun spandex chips. The temperature of the twin-screw extruder was set to 180°C and the speed was set to 100 r / min. Melt-spun spandex chips were obtained by an underwater pelletizer and transferred to a 65°C drying barrel for aging to obtain ultra-low melting point melt-spun spandex chips. The hard segment content of the obtained chips was 36% and the R value was 1.05.

[0087] Step 3: Preparation of ultra-low melting point crosslinker

[0088] 5.3 parts of PPA-3500 were added to a reactor, dehydrated at 110°C and a vacuum of 2 kPa for 1.5 hours, nitrogen was added as a protective atmosphere, and the temperature was cooled to 65°C; 1 part of hexamethylene diisocyanate was added, stirred and reacted under nitrogen protection for 2 hours, and the temperature was raised to 95°C to obtain an ultra-low melting point crosslinking agent with an NCO content of 8%.

[0089] Step 4: Preparation of ultra-low melting point melt-spun spandex fiber

[0090] The fully matured ultra-low melting point melt-spun spandex chips are injected into the feed port of a screw extruder, and the ultra-low melting point crosslinking agent prepared in step 3 is injected into the end of the screw. The amount of the ultra-low melting point crosslinking agent added is 9% of the mass of the ultra-low melting point melt-spun spandex chips. The temperature of the screw extruder is set to 205° C. The melt is uniformly mixed in a static mixer and then enters a metering pump. The filter screen removes gel impurities, and the filament melt is ejected through a spinneret. The filament melt is then sequentially cooled by side blowing, oiled, and wound to obtain a spandex cake, wherein the side blowing temperature is 30° C., the wind speed is 4.5 m / s, and the winding speed is 900 m / min. The obtained cake is naturally matured at 30° C. to obtain an ultra-low temperature-set melt-spun spandex fiber product with a fineness of 30D.

[0091] Comparative Example 1

[0092] A melt-spun spandex fiber, the preparation method is as follows:

[0093] Step 1: Poly(1,6-hexanediol adipate) polyol (PHA-2500, prepared as described in Example 1, except that the number average molecular weight is 2500 g / mol, the acid value is 0.3 mg KOH / g, and the moisture content is 95 ppm) is heated to 100° C. for melting and holding for 1 hour. BDO and HDO are each heated to 65° C. for melting and holding for 1 hour. MDI is heated to 55° C. for melting and holding for 1 to 5 hours. HDI is heated to 50° C. for 1 to 2 hours. The above materials are injected into the injection port of a twin-screw extruder in the following ratios: the molar ratios of PHA, BDO, HDO, MDI, and HDI are 0.28:0.38:0.38:0.43:0.65, respectively. At the same time, an organotin catalyst T12 is injected into the injection port in an amount of 0.0001% of the mass of the melt-spun spandex chips. The temperature of the twin-screw extruder was set at 120°C and the speed was set at 80 r / min. Melt-spun spandex chips were obtained by an underwater pelletizer and transferred to a 55°C drying barrel for aging to obtain melt-spun spandex chips. The hard segment content of the obtained chips was 29% and the R value was 1.05.

[0094] Step 2: The fully matured melt-spun spandex chips were injected into the feed port of a screw extruder. The ultra-low melting point crosslinker prepared in Step 3 of Example 1 was injected into the end of the screw at a ratio of 12% of the mass of the melt-spun spandex chips. The screw extruder temperature was set to 180°C. The melt was mixed uniformly in a static mixer and then fed into a metering pump. A filter was used to remove gel impurities. The filament melt was ejected through a spinneret and then sequentially cooled by side-blown air, oiled, and wound to produce a spandex cake. The side-blown air temperature was 15°C, the wind speed was 6 m / s, and the winding speed was 800 m / min. The resulting cake was naturally matured at 30°C to obtain a finished melt-spun spandex fiber with a fineness of 30D.

[0095] Comparative Example 2

[0096] A melt-spun spandex fiber, the preparation method is as follows:

[0097] Step 1: Polypentanediol adipate (PPA-4000) with a number-average molecular weight of 4000 g / mol (acid value of 0.25 mg KOH / g, moisture content of 76 ppm) was heated to 120°C for 3 hours, BDO was heated to 85°C for 3 hours, and MDI was heated to 65°C for 5 hours. These materials were injected into the injection port of a twin-screw extruder in the following proportions: the molar ratio of PPA-4000, BDO, and MDI was 0.18:1.55:1.82, respectively. Simultaneously, an organotin catalyst, T12, was injected into the injection port at a ratio of 0.002% of the mass of the melt-spun spandex chips. The temperature of the twin-screw extruder was set at 200°C and the speed was set at 130 r / min. Melt-spun spandex chips were obtained by an underwater pelletizer and transferred to a 75°C drying barrel for aging to obtain melt-spun spandex chips. The hard segment content of the obtained chips was 45% and the R value was 1.05.

[0098] Step 2: The fully matured melt-spun spandex chips are injected into the feed port of a screw extruder, and the ultra-low melting point crosslinking agent prepared in step 3 of Example 2 is injected into the end of the screw. The addition ratio is 5% of the mass of the spandex chips. The temperature of the screw extruder is set to 220° C. The melt is mixed evenly in a static mixer and then enters a metering pump. The filter screen removes gel impurities and the filament melt is ejected through a spinneret. The filament melt is then cooled by side blowing, oiled, and wound in sequence to obtain a spandex cake, wherein the side blowing temperature is 35° C., the wind speed is 3.5 m / s, and the winding speed is 1000 m / min. The obtained cake is naturally matured at 30° C. to obtain a melt-spun spandex fiber product with a fineness of 30D.

[0099] Comparative Example 3

[0100] A melt-spun spandex fiber, the preparation method is as follows:

[0101] Steps 1-2 are the same as steps 1-2 of Example 2;

[0102] Step 3: The fully matured ultra-low melting point melt-spun spandex chips are injected into the feed port of a screw extruder, and a commercial cross-linking agent (the commercial cross-linking agent is purchased from Dow Chemical, brand Hyperlast 5130) is injected into the end of the screw at a ratio of 5% of the mass of the ultra-low melting point melt-spun spandex chips. The temperature of the screw extruder is set to 220° C. The melt is mixed uniformly in a static mixer and then enters a metering pump. The filter screen removes gel impurities and the filament melt is ejected through a spinneret. The filament melt is then sequentially cooled by side-blowing, oiled, and wound to obtain a spandex cake. The side-blowing temperature is 35° C., the wind speed is 3.5 m / s, and the winding speed is 1000 m / min. The obtained cake is naturally matured at 30° C. to obtain a finished melt-spun spandex fiber with a fineness of 30D.

[0103] The performance of the melt-spun spandex slices prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was tested, and the results are shown in Table 1.

[0104] Table 1 Properties of melt-spun spandex chips

[0105]

[0106]

[0107] The performance of the melt-spun spandex fibers prepared in Examples 1 to 3 and Comparative Examples 1 to 3 was tested, and the results are shown in Table 2.

[0108] Table 2 Properties and shaping efficiency of melt-spun spandex fibers

[0109]

[0110] Note: When calculating the setting efficiency, the setting temperature is 100-105℃.

[0111] It can be seen from Table 2 that the setting efficiency of Comparative Example 1 at 100-105°C is 61%. The reason is that the melting point of its chips is too low (DSC melting point 95°C), which causes the spandex fiber to melt during the setting process, thereby reducing the setting efficiency; the setting efficiency of Comparative Example 2 at 100-105°C is only 9%. The reason is that the melting point of its chips is too high (DSC melting point 125.6°C), which causes the spandex fiber to almost not melt at a temperature of 100-105°C, and has a very small adhesion effect, so the setting efficiency is low; the setting efficiency of Comparative Example 3 at 100-105°C is only 40%. The reason is that although ultra-low melting point melt-spun spandex chips are used, a low melting point cross-linking agent is not used, and a commercial cross-linking agent is used, resulting in the spandex fiber setting efficiency at 100-105°C dropping to 40%, so a higher heat setting temperature is required. As can be seen from Table 2, the heat setting efficiency of the melt-spun spandex fibers prepared in Examples 1 to 3 at 100-105° C. is ≥80%, which indicates that the melt-spun spandex fibers prepared in the present invention can match the heat setting temperature of polyethylene and polypropylene, thus filling the market gap.

[0112] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing ultra-low temperature setting melt-spun spandex fiber, characterized in that: The following steps are involved: The polyester polyol, diisocyanate and small molecule diol chain extender are heated and kept warm respectively, and the above raw materials are injected into the injection port of a twin-screw extruder, and a catalyst is added to react and polymerize. The melt-spun spandex chips are obtained by underwater pelletizing and aging. The DSC melting point of the melt-spun spandex chips is 100° C. to 105° C. The melt-spun spandex slices are injected into the feeding port of a twin-screw extruder, a cross-linking agent is injected into the end of the screw, and ultra-low temperature setting melt-spun spandex fibers are obtained through spinning, wherein the setting temperature is 100-105°C.

2. The method for preparing ultra-low temperature setting melt-spun spandex fiber according to claim 1, characterized in that: The molar ratio of the polyester polyol, the small molecule diol chain extender and the diisocyanate is (0.18-0.23):(0.78-1.59):(1.07-1.84).

3. The method for preparing ultra-low temperature setting melt-spun spandex fiber according to claim 2, characterized in that: The polyester polyol is selected from at least one of poly(1,6-hexanediol adipate) polyol and poly(1,5-pentanediol adipate) polyol.

4. The method for preparing ultra-low temperature setting melt-spun spandex fiber according to claim 3, characterized in that: The number average molecular weight of the poly(1,6-hexanediol adipate) polyol and the poly(1,5-pentanediol adipate) polyol are both 3000-4000 g / mol, the acid value is ≤0.5 mg KOH / g, and the moisture content is ≤100 ppm.

5. The method for preparing ultra-low temperature setting melt-spun spandex fiber according to claim 2, characterized in that: The diisocyanate is a mixture of 4,4'-diphenylmethane diisocyanate and hexamethylene diisocyanate, wherein the molar proportion of 4,4'-diphenylmethane diisocyanate is 40-90%.

6. The method for preparing ultra-low temperature setting melt-spun spandex fiber according to claim 1, characterized in that: The small molecule diol chain extender is selected from at least one of 1,4-butanediol, 1,6-hexanediol and 1,5-pentanediol, and the molar proportion of 1,4-butanediol in the small molecule diol chain extender is 50-80%.

7. The method for preparing ultra-low temperature setting melt-spun spandex fiber according to claim 1, characterized in that: The catalyst is selected from organotin catalysts; And / or, the added amount of the catalyst is 0.001 to 0.002% of the mass of the melt-spun spandex chips.

8. The method for preparing ultra-low temperature setting melt-spun spandex fiber according to claim 1, characterized in that: The crosslinking agent is a substance with terminal NCO groups, which is polymerized from polyadipate-1,6-hexanediol polyol and hexamethylene diisocyanate, and its NCO content is 5-10%; And / or, the amount of the cross-linking agent is 5-12% of the mass of the melt-spun spandex chips.

9. A melt-spun spandex fiber with ultra-low temperature setting, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the ultra-low temperature setting melt-spun spandex fiber according to claim 9 in the preparation of spandex products having a setting temperature matching that of polyethylene and / or polypropylene.

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