Halogen-free flame-retardant low-temperature spandex fiber and preparation method thereof

Abstract

The invention discloses a halogen-free flame-retardant low-temperature spandex fiber and a preparation method thereof, and belongs to the technical field of textile fibers. The phosphorus-containing polyol, the conventional polyol and the isocyanate are used for synthesizing the phosphorus-containing cross-linking agent, the phosphorus-containing cross-linking agent and the low-temperature spandex slices are used for preparing the halogen-free flame-retardant low-temperature spandex fiber, and the preparation method of the halogen-free flame-retardant low-temperature spandex fiber has the advantages that the process is simple, the process is easy to control, the production efficiency is high, the cost is low and the like. The flame-retardant grade of the halogen-free flame-retardant low-temperature spandex fiber prepared by the preparation method disclosed by the invention reaches V0, the limit oxygen index reaches more than 30%, and through stable chemical bonding, an anti-migration lasting flame-retardant effect is realized, and a woven flame-retardant fabric meets the standard requirement of the American consumer safety committee (CPSC) on the flammability of children pajamas.

Description

Technical Field

[0001] This invention belongs to the field of textile fiber technology, and in particular relates to a halogen-free flame-retardant low-temperature spandex fiber and its preparation method. Background Technology

[0002] Spandex, or polyurethane elastic fiber, is usually blended with polyester, nylon, cotton, silk, and wool. Adding a small amount (1-10%) can give the fabric excellent elasticity, hence its reputation as "fabric MSG." However, the limiting oxygen index (LOI) of conventional spandex is only about 18%, lower than the oxygen content of 21% in the air, making it a flammable material. When blended with other flame-retardant fibers, it will seriously affect the flame-retardant properties of flame-retardant fabrics and textiles.

[0003] Patent CN105420844A discloses a method for preparing flame-retardant spandex fibers. The method involves blending the spinning solution with a halogen-free phosphorus-based flame retardant and a synergist, silica, and then dry spinning the resulting spandex fibers to obtain fibers with good flame-retardant properties. However, the blending method carries the risk of precipitation.

[0004] Patent CN103590138B discloses a method for preparing flame-retardant polyurethane elastic fibers, which introduces a mixture containing -COOH and HPO2. 2- Reactive phosphorus-based flame retardants are used to copolymerize and modify polyurethane elastic fibers to obtain flame-retardant polyurethane fibers. The addition of reactive flame retardants will inevitably destroy the regularity of polyurethane molecules, thereby reducing the mechanical properties of spandex fibers.

[0005] Therefore, there is an urgent need in this field for a new type of halogen-free flame-retardant spandex fiber with high flame retardancy rating, high oxygen index and excellent mechanical properties. Summary of the Invention

[0006] The purpose of this invention is to provide a halogen-free flame-retardant low-temperature spandex fiber and its preparation method, thereby solving the problems existing in the prior art. This invention achieves a balance between flame retardant performance, mechanical properties, and environmental friendliness through the molecular structure design of the phosphorus-containing crosslinking agent and optimization of the melt blending process, thus solving problems such as flame retardant migration, complex processes, and high costs in the prior art.

[0007] In a first aspect, the present invention provides a halogen-free flame-retardant low-temperature spandex fiber, the raw materials of which include low-temperature spandex chips and a phosphorus-containing crosslinking agent; the mass of the phosphorus-containing crosslinking agent is 5-15% of the mass of the low-temperature spandex chips; the phosphorus-containing crosslinking agent is selected from phosphorus-containing macromolecules whose molecular chain ends have isocyanate groups.

[0008] Furthermore, the low-temperature spandex chips are selected from polyester-type, polyether-type, or ether-ester mixed fiber-grade thermoplastic polyurethane elastomers.

[0009] Furthermore, the content of isocyanate groups in the phosphorus-containing macromolecule is 4.3-7.2%.

[0010] Furthermore, the preparation method of the phosphorus-containing crosslinking agent includes the following steps: mixing macromolecular diol and phosphorus-containing diol, dehydrating under vacuum at 100-120°C for 1-2 hours, cooling to 60-70°C under an inert gas atmosphere, then introducing diisocyanate, heating to 70-80°C, and stirring the reaction for 1-3 hours to obtain the phosphorus-containing crosslinking agent.

[0011] Furthermore, the molar ratio of the macromolecular diol, the phosphorus-containing diol, and the diisocyanate is 1:(0.5-1.5):(2.5-7.5).

[0012] Furthermore, the macromolecular diol includes one or more of polyester diol, polycaprolactone diol, polycarbonate diol, polyether diol, polylactide diol, and polyglycolic acid diol.

[0013] The number-average molecular weight of the macromolecular diol is 1000~5000.

[0014] The phosphorus-containing diol includes one or more of Exolit OP 550 and Exolit OP 560.

[0015] The key to this invention lies in utilizing phosphorus-containing diols as reactive monomers to achieve inherent flame retardancy in low-temperature spandex. This method not only avoids the migration problem of traditional additive flame retardants, ensuring the long-term stability of flame retardant efficacy, but also aligns with the development trend of halogen-free and environmentally friendly technologies. This invention introduces phosphorus-containing polyols into the crosslinking agent. Compared to the traditional process of adding them via copolymerization to low-temperature spandex chips, this does not disrupt the molecular structure regularity of the chips, thereby ensuring that the prepared flame-retardant low-temperature spandex fibers possess superior mechanical properties.

[0016] Furthermore, the diisocyanate includes one or more of hydrogenated diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, cyclohexanedimethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophthalic diisocyanate, and 1,5-naphthalene diisocyanate. Preferably, one or more of diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate are selected.

[0017] Secondly, the present invention provides a method for preparing the above-mentioned halogen-free flame-retardant low-temperature spandex fiber, comprising the following steps: injecting pre-dried low-temperature spandex chips into the feed port of a screw extruder, injecting a phosphorus-containing crosslinking agent into the end of the screw, mixing the melt evenly through a static mixer and then entering a metering pump, removing gel impurities through a filter screen, and extruding fine filament melt through a spinneret, and then sequentially passing through side-blowing cooling, oiling, winding, and curing to prepare the halogen-free flame-retardant low-temperature spandex fiber.

[0018] Furthermore, the temperature of the screw extruder is set to 170-220℃; and / or the temperature of the side-blowing cooling air is 15-35℃, and the wind speed is 3-6m / s; and / or the winding speed is 700-1000m / min.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects:

[0020] This invention uses phosphorus-containing polyols, conventional polyols, and isocyanates to synthesize a phosphorus-containing crosslinking agent. This phosphorus-containing crosslinking agent, along with low-temperature spandex chips, is used to prepare halogen-free flame-retardant low-temperature spandex fibers. This method offers advantages such as simple processing, easy process control, high production efficiency, and low cost. The halogen-free flame-retardant low-temperature spandex fibers prepared by this invention achieve a flame retardancy rating of V0 and a limiting oxygen index of 30%. Furthermore, through stable chemical bonding, a long-lasting flame-retardant effect against migration is achieved. The woven flame-retardant fabric meets the flammability standards for children's sleepwear set by the U.S. Consumer Product Safety Commission (CPSC). Detailed Implementation

[0021] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0022] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0023] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0024] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0025] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0026] The method for preparing the low-temperature spandex chips used in this embodiment of the invention is as follows:

[0027] The preparation method of low-temperature spandex chips BT-9280 is as follows: Polytetramethylene ether diol (PTMEG-1000), 1,4-butanediol (BDO), and diphenylmethane diisocyanate (MDI) with a number average molecular weight of 1000 are heated and melted and kept at a constant temperature. The above materials are injected into the feed port of a twin-screw extruder in a specific ratio: PTMEG-1000, BDO, and MDI molar ratio of 1:0.55:1.65. Simultaneously, dibutyltin dilaurate catalyst is injected into the feed port at an amount of 0.002% of the mass of the thermoplastic polyurethane elastomer. The temperature of the twin-screw extruder is set to 160℃, and the speed is set to 100 r / min. The chips are then passed through an underwater pelletizer and dehumidified to obtain low-temperature spandex chips with a number average molecular weight of 350,000.

[0028] The preparation method of low-temperature spandex chips BT-9190 is as follows: Polycaprolactone diol (PCL-2000), 1,4-butanediol (BDO), and diphenylmethane diisocyanate (MDI) with a number average molecular weight of 2000 are heated and melted and kept at a constant temperature. The above materials are injected into the feed port of a twin-screw extruder in a ratio of PCL-2000, BDO, and MDI of 1:1.33:2.47. Simultaneously, dibutyltin dilaurate catalyst is injected into the feed port at an amount of 0.003% of the mass of the low-temperature spandex chips. The temperature of the twin-screw extruder is set to 180℃, and the speed is set to 120 r / min. The chips are then passed through an underwater pelletizer and dehumidified to obtain low-temperature spandex chips with a number average molecular weight of 300,000.

[0029] The preparation method of low-temperature spandex chips BT-9180 is as follows: Polytetramethylene ether diol (PTMEG-3000), 1,4-butanediol (BDO), and diphenylmethane diisocyanate (MDI) with a number average molecular weight of 3000 are heated and melted and kept at a constant temperature. The above materials are injected into the feed port of a twin-screw extruder in a specific ratio: PTMEG-3000, BDO, and MDI molar ratio of 1:2.50:3.71. Simultaneously, dibutyltin dilaurate catalyst is injected into the feed port at an amount of 0.003% of the mass of the low-temperature spandex chips. The temperature of the twin-screw extruder is set to 200℃, and the speed is set to 150 r / min. The chips are then passed through an underwater pelletizer and dehumidified to obtain low-temperature spandex chips with a number average molecular weight of 380,000.

[0030] The spinning oil agent DELION 342 used in the oiling process in this embodiment of the invention was purchased from Takemoto Oils & Fats Co., Ltd. of Japan.

[0031] In the embodiments of this invention, the phosphorus-containing diol used is Exolit OP 550 or Exolit OP 560, purchased from Klein Company.

[0032] Example 1

[0033] S1. Polybutylene adipate diol (PBA-1000) with a number average molecular weight of 1000 and Exolit OP550 were added to a reaction vessel at a molar ratio of 1:0.5 and mixed thoroughly. The mixture was dehydrated at 100°C and a vacuum of 0-5 kPa for 1 hour. Nitrogen gas was introduced as a protective atmosphere, and the mixture was cooled to 60°C. Diphenylmethane diisocyanate (diphenylmethane diisocyanate:PBA-1000 = 2.5:1 molar ratio) was introduced under nitrogen protection. The mixture was heated to 70°C and stirred for 1 hour to prepare a phosphorus-containing crosslinking agent with an isocyanate group content of 4.3%.

[0034] S2. Pre-dried low-temperature spandex chips BT-9280 (moisture content 0.05wt.%) are injected into the feed port of the screw extruder. The phosphorus-containing crosslinking agent prepared in S1 is injected into the end of the screw. The phosphorus-containing crosslinking agent is 5% of the mass of the low-temperature spandex chips. The temperature of the screw extruder is set to 180℃. After the melt is mixed evenly by the static mixer, it enters the metering pump. The filter screen removes gel impurities. The melt is then sprayed out as fine filaments through the spinneret. After passing through the side-blowing cooling, oiling, and winding processes, spandex filament cakes are obtained. The side-blowing temperature is 15℃, the wind speed is 3m / s, and the winding speed is 700m / min. The obtained spandex filament cakes are naturally cured at 30℃ to obtain halogen-free flame-retardant low-temperature spandex fibers.

[0035] Example 2

[0036] S1. Polycaprolactone diol (PCL-5000) with a number average molecular weight of 5000 and Exolit OP 560 were added to a reaction vessel at a molar ratio of 1:1.5 and mixed thoroughly. The mixture was dehydrated at 120°C and under a vacuum of 0 kPa for 2 hours. Nitrogen gas was introduced as a protective atmosphere, and the mixture was cooled to 70°C. Under nitrogen protection, hydrogenated diphenylmethane diisocyanate (hydrogenated diphenylmethane diisocyanate:PCL-5000 = 7.5:1 molar ratio) was introduced. The mixture was heated to 80°C and stirred for 3 hours to prepare a phosphorus-containing crosslinking agent with an isocyanate group content of 5.7%.

[0037] S2. Pre-dried low-temperature spandex chips BT-9190 (moisture content 0.03wt.%) are injected into the feed port of the screw extruder. The phosphorus-containing crosslinking agent prepared in S1 is injected into the end of the screw. The phosphorus-containing crosslinking agent is 15% of the mass of the spandex chips. The temperature of the screw extruder is set to 220℃. After the melt is mixed evenly by the static mixer, it enters the metering pump. The filter screen removes gel impurities. The melt is then sprayed out as fine filaments through the spinneret. After passing through the side-blowing cooling, oiling, and winding processes, spandex filament cakes can be obtained. The side-blowing temperature is 35℃, the wind speed is 6m / s, and the winding speed is 1000m / min. The obtained spandex filament cakes are naturally cured at 30℃ to obtain halogen-free flame-retardant low-temperature spandex fibers.

[0038] Example 3

[0039] S1. Polytetrahydrofuran diol (PTMEG-2000) with a number average molecular weight of 2000 and Exolit OP 550 were added to a reaction vessel at a molar ratio of 1:1 and mixed thoroughly. The mixture was dehydrated at 110°C and a vacuum of 0-5 kPa for 1.5 h. Nitrogen gas was introduced as a protective atmosphere, and the mixture was cooled to 65°C. Hexamethylene diisocyanate (hexamethylene diisocyanate:PTMEG-2000 = 5:1 molar ratio) was introduced under nitrogen protection. The mixture was heated to 75°C and stirred for 2 h to prepare a phosphorus-containing crosslinking agent with an isocyanate group content of 7.2%.

[0040] S2. Pre-dried low-temperature spandex chips BT-9180 (moisture content 0.01wt.%) are injected into the feed port of the screw extruder. The phosphorus-containing crosslinking agent prepared in S1 is injected into the end of the screw. The phosphorus-containing crosslinking agent is 10% of the mass of the spandex chips. The temperature of the screw extruder is set to 210℃. After the melt is mixed evenly by the static mixer, it enters the metering pump. The filter screen removes gel impurities. The melt is then sprayed out as fine filaments through the spinneret. After passing through the side-blowing cooling, oiling, and winding processes, spandex filament cakes are obtained. The side-blowing temperature is 25℃, the wind speed is 4m / s, and the winding speed is 900m / min. The obtained spandex filament cakes are naturally cured at 30℃ to obtain halogen-free flame-retardant low-temperature spandex fibers.

[0041] Comparative Example 1

[0042] S1. Polytetrahydrofuran diol (PTMEG-2000) with a number average molecular weight of 2000 was added to a reactor and dehydrated at 110°C and a vacuum of 0-5 kPa for 1.5 h. Nitrogen gas was introduced as a protective atmosphere, and the mixture was cooled to 65°C. Hexamethylene diisocyanate (hexamethylene diisocyanate:PTMEG-2000 = 3.17:1, molar ratio) was introduced under nitrogen protection. The mixture was heated to 75°C and stirred for 2 h to obtain a crosslinking agent with an isocyanate group content of 7.2%.

[0043] S2. Pre-dried low-temperature spandex chips BT-9180 (moisture content 0.02wt.%) are injected into the feed port of the screw extruder. The crosslinking agent prepared in S1 is injected into the end of the screw. The crosslinking agent is 10% of the mass of the spandex chips. The temperature of the screw extruder is set to 210℃. After the melt is mixed evenly by the static mixer, it enters the metering pump. The filter screen removes gel impurities. The melt is then spun out into fine filaments through the spinneret. After passing through the side-blowing cooling, oiling, and winding processes, spandex filament cakes are obtained. The side-blowing temperature is 25℃, the wind speed is 4m / s, and the winding speed is 900m / min. The obtained spandex filament cakes are naturally cured at 30℃ to obtain low-temperature spandex fibers.

[0044] Comparative Example 2

[0045] S1. Polycaprolactone diol (PCL-5000) with a number average molecular weight of 5000 was added to a reaction vessel and dehydrated at 120°C and 0 kPa vacuum for 2 hours. Nitrogen gas was introduced as a protective atmosphere, and the mixture was cooled to 70°C. Hydrogenated diphenylmethane diisocyanate (hydrogenated diphenylmethane diisocyanate:PCL-5000 = 5.34:1, molar ratio) was introduced under nitrogen protection. The mixture was heated to 80°C and stirred for 3 hours to prepare a phosphorus-containing crosslinking agent with an isocyanate group content of 5.7%.

[0046] S2. Pre-dried low-temperature spandex chips BT-9190 (moisture content 0.03wt.%) are injected into the feed port of the screw extruder. The phosphorus-containing crosslinking agent prepared in S1 is injected into the end of the screw. The phosphorus-containing crosslinking agent is 15% of the mass of the spandex chips. The temperature of the screw extruder is set to 220℃. After the melt is mixed evenly by the static mixer, it enters the metering pump. The filter screen removes gel impurities. The melt is then sprayed out as fine filaments through the spinneret. After passing through the side-blowing cooling, oiling, and winding processes, spandex filament cakes can be obtained. The side-blowing temperature is 35℃, the wind speed is 6m / s, and the winding speed is 1000m / min. The obtained spandex filament cakes are naturally cured at 30℃ to obtain halogen-free flame-retardant low-temperature spandex fibers.

[0047] The low-temperature spandex fibers prepared in Examples 1-3 and Comparative Examples 1-2 were tested for mechanical and flame retardant properties. The mechanical properties were tested according to standard FZ / T 54010-2014, the flame retardant rating was tested according to standard UL-94, the limiting oxygen index was tested according to standard GB / T 5454-1997, and the flame retardant properties were tested according to standard 16 CFR 1615 (the acceptance criteria are: the average char length of 5 samples must not exceed 17.8 cm, and no single sample can have a char length of 25.4 cm). The test results are shown in Table 1.

[0048] Table 1

[0049]

[0050] Note: LOI is the Limiting Oxygen Index.

[0051] As shown in Table 1, the halogen-free flame-retardant low-temperature spandex fibers prepared in Examples 1-3 exhibit excellent mechanical properties, achieving a flame retardancy rating of V0 and a limiting oxygen index exceeding 30%. Furthermore, they pass the 16 CFR 1615 standard test, meeting the US Consumer Product Safety Commission (CPSC) requirements for the flammability of children's pajamas. In Comparative Examples 1 and 2, the absence of phosphorus-containing diols in the crosslinking agent preparation resulted in a significant decrease in the flame retardant properties of the prepared low-temperature spandex fibers, failing the 16 CFR 1615 standard test.

[0052] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A halogen-free flame-retardant low-temperature spandex fiber, characterized in that, Its raw materials include low-temperature spandex chips and phosphorus-containing crosslinking agents; the mass of the phosphorus-containing crosslinking agent is 5-15% of the mass of the low-temperature spandex chips; the phosphorus-containing crosslinking agent is selected from phosphorus-containing macromolecules with isocyanate groups at the end of the molecular chain.

2. The halogen-free flame-retardant low-temperature spandex fiber according to claim 1, characterized in that, The low-temperature spandex chips are selected from polyester, polyether, or ether ester blended fiber-grade thermoplastic polyurethane elastomers.

3. The halogen-free flame-retardant low-temperature spandex fiber according to claim 1, characterized in that, The content of isocyanate groups in the phosphorus-containing macromolecule is 4.3-7.2%.

4. The halogen-free flame-retardant low-temperature spandex fiber according to claim 1, characterized in that, The preparation method of the phosphorus-containing crosslinking agent includes the following steps: mixing macromolecular diol and phosphorus-containing diol, dehydrating under vacuum at 100-120°C, cooling to 60-70°C under an inert gas atmosphere, then introducing diisocyanate, heating to 70-80°C, stirring to react, and obtaining the phosphorus-containing crosslinking agent.

5. The halogen-free flame-retardant low-temperature spandex fiber according to claim 4, characterized in that, The molar ratio of the macromolecular diol, the phosphorus-containing diol, and the diisocyanate is 1:(0.5-1.5):(2.5-7.5).

6. The halogen-free flame-retardant low-temperature spandex fiber according to claim 4, characterized in that, The macromolecular diols include one or more of polyester diols, polycaprolactone diols, polycarbonate diols, polyether diols, polylactide diols, and polyglycolic acid diols.

7. The halogen-free flame-retardant low-temperature spandex fiber according to claim 4, characterized in that, The phosphorus-containing diol is at least one of Exolit OP 550 and Exolit OP 560.

8. The halogen-free flame-retardant low-temperature spandex fiber according to claim 4, characterized in that, The diisocyanate includes one or more of hydrogenated diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, cyclohexanedimethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophthalic diisocyanate, and 1,5-naphthalene diisocyanate.

9. A method for preparing halogen-free flame-retardant low-temperature spandex fiber according to any one of claims 1-8, characterized in that, The process includes the following steps: pre-dried low-temperature spandex chips are injected into the feed port of a screw extruder, a phosphorus-containing crosslinking agent is injected at the end of the screw, the melt is mixed evenly by a static mixer and then enters a metering pump, a filter screen removes gel impurities, and the filament melt is ejected through a spinneret, and then sequentially undergoes side-blowing cooling, oiling, winding, and curing to obtain the halogen-free flame-retardant low-temperature spandex fiber.

10. The preparation method according to claim 9, characterized in that, The temperature of the screw extruder is set to 170-220℃; and / or the temperature of the side-blowing cooling air is 15-35℃ and the wind speed is 3-6m / s; and / or the winding speed is 700-1000m / min.

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