Superfine polyethylene / polyester composite fiber and preparation method thereof

Abstract

The invention discloses a superfine polyethylene / polyester composite fiber and a preparation method thereof, belongs to the technical field of composite fibers, and solves the problems that in the prior art, the compatibility of a skin layer and a core layer is poor, the fineness of PE / PET fibers is large, and fiber ultra-fining is not facilitated. The filament number of the superfine polyethylene / polyester composite fiber is 0.6-0.8 dtex, the superfine polyethylene / polyester composite fiber is of a skin-core structure, the skin layer is made of polyethylene, the core layer is made of a blend of modified polyester and a compatilizer, a molecular chain of the modified polyester is composed of a terephthalic acid chain segment, an ethylene glycol chain segment and an isophthalic acid chain segment, and the molecular chain of the modified polyester is composed of an ethylene glycol chain segment and an isophthalic acid chain segment. And the compatilizer is a grafted copolymer of polyethylene and poly (ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate. The preparation method disclosed by the invention is simple and easy to implement, the compatibility of the skin layer and the core layer is good, the superfine fiber is favorably realized, and the composite fiber has excellent performance and can meet high-end market requirements.

Description

Technical Field

[0001] The invention belongs to the technical field of composite fibers and relates to an ultrafine polyethylene / polyester composite fiber and a preparation method thereof. Background Art

[0002] Bi-component spunbond nonwovens are increasingly attracting attention for their high strength, elongation and soft feel. Choosing different raw material combinations and different combination forms can change the variety of bi-component spunbond nonwovens, making the products rich and colorful with different characteristics and performance. Polyethylene / polyester (PE / PET) bi-component spunbond nonwovens are made of slices of PE and PET components, which are extruded by separate screw extruders and then melt-compounded into a web and reinforced. PE / PET skin-core composite fibers have high strength, good fluffiness and high elastic recovery rate. The nonwovens produced after hot rolling of the fiber web have the characteristics of soft feel and good elasticity. They are currently widely used in sanitary products such as surgical masks and bandages.

[0003] With the development of economy, the quality of life of the people is improving year by year. At the same time, consumer demand is also changing. The demand for multifunctional and high-quality products such as sanitary napkins and diapers is increasing year by year, such as dryness, breathability, softness and non-irritation, which also puts higher requirements on the performance and quality of raw materials of products. PE / PET fiber with stronger functionality and adaptability is an ideal material for manufacturing high-end sanitary napkins and diapers, which conforms to the development trend of high-end consumption and has a good development prospect. From the current market situation, 80% of domestic PE / PET fiber products are medium and low-end products, and high-value-added high-end products are basically monopolized by foreign manufacturers. The main reason is that the fineness of domestic PE / PET fiber is too large and PE / PET fiber is easy to cause skin-core separation and slippage, which affects the post-processing technology and the comfort of the fabric layer of terminal sanitary products. At present, the single-filament fineness of the main domestic products can only reach about 2.0dtex, and its application is severely restricted.

[0004] When the fiber monofilament fineness is reduced to a certain level, the fabric woven with this ultrafine fiber will show many unique characteristics: such as soft touch, high flexibility, high water absorption, etc. Therefore, it is of great significance to improve the quality of PE / PET fibers, research and develop ultrafine PE / PET fibers, and meet the needs of the high-end market. Summary of the invention

[0005] The purpose of the present invention is to solve the above problems existing in the prior art and to provide an ultrafine polyethylene / polyester composite fiber and a preparation method thereof.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: An ultrafine polyethylene / polyester composite fiber, wherein the monofilament fineness of the ultrafine polyethylene / polyester composite fiber is 0.6-0.8 dtex; The ultrafine polyethylene / polyester composite fiber has a skin-core structure, the skin layer material is polyethylene (PE), and the core layer material is a blend of modified polyester and a compatibilizer; The molecular chain of the modified polyester consists of a terephthalic acid segment, an ethylene glycol segment and an isophthalic acid segment; The compatibilizer is polyethylene and poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate graft copolymer.

[0007] As the preferred technical solution: The ultrafine polyethylene / polyester composite fiber as described above has a breaking strength of 3.3~3.7cN / dtex, an elongation at break of 50.0±10.0%, a curl number of 13~16 / 25mm, a curl degree of 14~18%, and a fiber length of 35~40mm.

[0008] In the ultrafine polyethylene / polyester composite fiber as described above, the sheath-core weight ratio of the sheath-core structure is 40-50:50-60.

[0009] As described above, the ultrafine polyethylene / polyester composite fiber has a melt index of 20±2 g / 10 min measured at a temperature of 190°C and a pressure of 0.3 MPa, and the intrinsic viscosity of the modified polyester is 0.64~0.66 dL / g.

[0010] The ultrafine polyethylene / polyester composite fiber as described above, the preparation process of the modified polyester is as follows: (1) After terephthalic acid, isophthalic acid and ethylene glycol are prepared into a slurry, an esterification reaction is carried out, and the reaction is carried out under a nitrogen atmosphere under a pressure of normal pressure to 0.3 MPa and a reaction temperature of 230 to 250°C. When the amount of water distilled during the esterification reaction reaches more than 95% of the theoretical value, the esterification reaction ends, and an esterification product is obtained; (2) After the esterification reaction in step (1) is completed, a low vacuum stage polycondensation reaction is started under negative pressure under the action of a catalyst and a stabilizer. The pressure in this stage is steadily pumped from normal pressure to an absolute pressure below 500 Pa, the temperature is controlled at 260-270° C., and the reaction time is 30-50 minutes. Then, the vacuum is continued to be pumped to reduce the reaction pressure to an absolute pressure of less than 70 Pa, and a high vacuum stage polycondensation reaction is carried out. The reaction temperature is controlled at 275-280° C., and the reaction time is 50-90 minutes. After the polycondensation is completed, the material is discharged and granulated to obtain the modified polyester.

[0011] The ultrafine polyethylene / polyester composite fiber as described above, wherein in step (1), the molar ratio of terephthalic acid, isophthalic acid and ethylene glycol is 1:0.3-0.5:1.7-2.3; In step (2), the catalyst is antimony trioxide, ethylene glycol antimony or antimony acetate, and the stabilizer is triphenyl phosphate, trimethyl phosphate or trimethyl phosphite; the amount of the catalyst added is 0.01% to 0.05% of the total weight of terephthalic acid and isophthalic acid, and the amount of the stabilizer added is 0.01% to 0.05% of the total weight of terephthalic acid and isophthalic acid.

[0012] The preparation process of the ultrafine polyethylene / polyester composite fiber as described above is as follows: (1) Initiator 4,4'-azo (4-cyanovaleric acid), monomer methyl methacrylate and chain transfer agent thioglycolic acid are added to a reaction kettle in sequence, and then tetrahydrofuran is added to dissolve, and the mixture is reacted in a nitrogen atmosphere at 60-65°C for 4-5 hours. After the reaction is completed, the product is purified and dried to obtain carboxyl-containing polymethyl methacrylate (PMMA-COOH); (2) After drying, poly(ethylene-co-glycidyl methacrylate) (EGMA) and carboxyl-containing polymethyl methacrylate are added to an internal mixer together with an initiator, and granulated by internal mixing to obtain poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate (EGMA-g-PMMA); wherein the temperature of the internal mixer is 180-190°C, the speed is 50-60 rpm, and the mixing time is 8-10 min; (3) The polyethylene and poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate) are dried separately and added into an internal mixer, and the compatibilizer is obtained by internal mixer granulation; wherein the temperature of the internal mixer is 180-190°C, the rotation speed is 50-60 rpm, and the internal mixer time is 10-15 min.

[0013] The ultrafine polyethylene / polyester composite fiber as described above, wherein in step (1), the molar ratio of methyl methacrylate, thioglycolic acid and 4,4'-azo(4-cyanovaleric acid) is 100:5-6:1-1.5, and the mass ratio of methyl methacrylate to tetrahydrofuran is 1:1-1.5; In step (2), the mass ratio of poly(ethylene-co-glycidyl methacrylate) to carboxyl-containing polymethyl methacrylate is 100:5-8, and the amount of dibenzoyl peroxide is 0.2%-0.3% of the total mass of poly(ethylene-co-glycidyl methacrylate) and carboxyl-containing polymethyl methacrylate; In step (3), the mass ratio of polyethylene to poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate is 100:3-5.

[0014] The present invention also provides a method for preparing an ultrafine polyethylene / polyester composite fiber as described in any one of the above items, wherein the ultrafine polyethylene / polyester composite fiber is prepared according to a core-skin composite spinning process, and specifically comprises the following steps: (1) The dried polyethylene is melted by the screw, and the measured polyethylene melt enters the spinning box A; (2) The dried modified polyester and the compatibilizer are mixed in a mass ratio of 100:2.5-3.5, and then melted and exhausted by the screw in sequence. The metered mixed melt enters the spinning box B; (3) The melt in spinning beam A and spinning beam B is ejected through a composite spinneret to form a filament with a sheath-core structure, which is then spun, cooled, bundled, stretched, curled, cut, and dried in sequence to obtain ultrafine polyethylene / polyester composite fibers.

[0015] As the preferred technical solution: In the method for preparing ultrafine polyethylene / polyester composite fibers as described above, in step (1), the screw melting temperature is 220-250°C, and the polyethylene melt conveying temperature is 260-265°C; In step (2), the screw melting temperature is 260-270°C, and the mixed melt conveying temperature is 275-280°C; In step (3), the spinning temperature is 275-280°C, and the spinning speed is 1000-1200 m / min; the cooling adopts ring air cooling, the ring air temperature is 14-18°C, and the ring air speed is 1.0-1.2 m / s; the first stretching temperature is 70-75°C, the second stretching temperature is 100°C, and the total stretching multiple is 3.4-3.6 times; the drying temperature is 100-110°C.

[0016] Invention mechanism: Since the diameter of ultrafine fiber is very small, its bending stiffness is very small, and the fiber feels particularly soft; its specific surface area is very large, so the coverage, fluffiness and warmth retention of ultrafine fiber fabrics are significantly improved, and the ultrafine fabrics are also waterproof and breathable. The main factors restricting the ultrafineness of PE / PET fiber are: first, the compatibility between the PE in the cortex and the PET in the core layer of PE / PET sheath-core fiber is poor, which causes the sheath fiber and the core fiber to fall off easily during stretching, resulting in hair, making the ultrafineness of the fiber more difficult; second, the polyester as the core layer crystallizes during the stretching process, and because of the low melting point of polyethylene, the stretching temperature of PE / PET fiber is low, resulting in a low stretching multiple.

[0017] The present invention adds a PE graft copolymer as a compatibilizer to the PET in the core layer of the PE / PET fiber. The compatibilizer is formed by grafting polyethylene with ethylene-glycidyl methacrylate (GMA)-methyl methacrylate (MMA). The glycidyl methacrylate molecule in the compatibilizer contains two hydroxyl groups, which can form an ether bond with the terminal hydroxyl group of PET and react with the terminal carboxyl group to form an ester.

[0018] Due to the certain viscosity difference between PET and the compatibilizer, the low-viscosity component compatibilizer migrates from the central low shear rate zone to the outer high shear rate zone and gathers outside the core polyester fiber. On the one hand, the compatibility of the compatibilizer with the polar polyester is improved due to the introduction of polar groups, which enhances the interaction between the compatibilizer and the polyester; on the other hand, since the compatibilizer gathers outside the core polyester fiber and is preferentially distributed at the interface between the two phases, the ethylene-co-methyl methacrylate in the compatibilizer copolymer reduces the interfacial tension between PET and PE, can appropriately improve the interfacial adhesion between PET and PE, reduce the interfacial energy between PET and PE, and increase the compatibility between PET and PE; at the same time, due to the increase in the specific surface area of ​​the skin fiber and the core fiber in the ultrafine fiber, higher requirements are put forward for the interfacial adhesion between the skin fiber and the core fiber. Methyl methacrylate (MMA) in the compatibilizer can both increase the compatibility of PET and improve the mechanical properties of the material. The ester bond of PMMA is easy to form intermolecular hydrogen bonding with PET at the interface, making it easy for the PE and PET molecular chains to entangle, further enhancing the interaction between the two components, which is beneficial to the increase of the stretching multiple of PE / PET fibers and provides conditions for the preparation of ultrafine fibers. The polyolefin part in the compatibilizer is similarly compatible with the polyethylene of the skin layer. The compatibilizer increases the tightness of the core layer PET and the skin layer PE, connects the PET and PE macromolecular chains, and improves the compatibility of the two materials, thereby increasing the interaction force between the skin layer and the core layer, strengthening the bonding force between the skin and core layers, and improving the incompatibility of components such as the slippage of the skin-core fibers, thereby solving the problems of skin-core separation and poor strength caused by poor compatibility.

[0019] The polyester in the primary fiber of PE / PET fiber is amorphous, and its stretching process is carried out above the glass transition temperature of polyester; the water bath temperature of the stretching bath for the primary stretching of PE / PET fiber is 70~75℃. After the primary stretching, the fiber has a certain degree of orientation, and the crystallinity of polyester is also improved. When the secondary steam stretching is carried out, a higher steam stretching temperature of 100℃ must be used. However, the stretching temperature of PE / PET fiber is only suitable for the stretching of polyethylene, which is too low for polyester. The stretching temperature of conventional polyester is 80~85℃ for the primary stretching and 125~130℃ for the secondary stretching. Due to the low melting point of polyethylene, if the temperature is too high, the sliding of the macromolecular chain will increase, the fiber strength will decrease, and even the fiber cortex will soften, bond or melt. How to increase the stretching multiple at the existing E / PET fiber stretching temperature is the key to solving the problem.

[0020] The invention introduces isophthalic acid into polyester. The introduction of isophthalic acid chain segments destroys the molecular structure of polyester, changing it from a highly ordered regular structure to a disordered chaotic structure; the addition of isophthalic acid chain segments changes the ratio and size between different sub-macroscopic crystal forms of polyester, making it difficult for polyester to crystallize and tend to exist in an amorphous manner; the amorphous modified polyester can obtain a higher stretching multiple at a lower temperature, thereby increasing the total stretching multiple of PE / PET composite fibers, which is beneficial to the ultra-fine fiber. At the same time, by regulating the content of isophthalic acid, the melting point of the modified polyester is controlled to be around 200°C, maintaining a certain dimensional stability during the fabric processing process, and playing a supporting role.

[0021] Therefore, the dual effects of the compatibilizer polyethylene and poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate graft copolymer and the modified polyester overcome the main factors restricting the ultrafineness of PE / PET fibers, making it possible to prepare ultrafine polyethylene / polyester composite fibers.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention discloses an ultrafine polyethylene / polyester composite fiber, wherein the core layer is mixed with a specific compatibilizer, wherein the glycidyl methacrylate molecule in the compatibilizer contains two hydroxyl groups, which can form an ether bond with the terminal hydroxyl group of PET and react with the terminal carboxyl group to form an ester. The grafted PMMA in the compatibilizer can not only increase the compatibility of PET, but also improve the mechanical properties of the material. The compatibilizer increases the tightness of the core layer PET and the skin layer PE, connects the PET and PE macromolecular chains, improves the compatibility of the two materials, thereby increasing the interaction force between the skin layer and the core layer, and solves the problems of skin-core separation caused by poor compatibility and is conducive to the ultrafineness of the fiber. (2) The ultrafine polyethylene / polyester composite fiber of the present invention is prepared by adding isophthalic acid chain segments into polyester to destroy the molecular structure, making it difficult for the polyester to crystallize and tending to exist in an amorphous state; the amorphous modified polyester can obtain a higher stretching multiple at a lower temperature, thereby increasing the total stretching multiple of the PE / PET composite fiber and facilitating the ultrafineness of the fiber. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0024] Among the raw materials used in the embodiments of the present invention, the melt index of polyethylene measured at a temperature of 190° C. and a pressure of 0.3 MPa is 20 g / 10 min, and the intrinsic viscosity of polyester is 0.67 dL / g.

[0025] Example 1 A method for preparing ultrafine polyethylene / polyester composite fibers, the specific steps are as follows: (1) Preparation of modified polyester; S1. After preparing terephthalic acid, isophthalic acid and ethylene glycol in a molar ratio of 1:0.3:1.7 into a slurry, an esterification reaction is carried out, and a pressure reaction is carried out under a nitrogen atmosphere. The pressure is normal pressure and the reaction temperature is 230° C. When the amount of water distilled in the esterification reaction reaches 95% of the theoretical value, the esterification reaction is terminated to obtain an esterification product; S2 After the esterification reaction of step S1 is completed, under the action of antimony trioxide catalyst (the amount added is 0.01% of the total weight of terephthalic acid and isophthalic acid) and triphenyl phosphate stabilizer (the amount added is 0.01% of the total weight of terephthalic acid and isophthalic acid), a low vacuum stage polycondensation reaction is started under negative pressure conditions. The pressure in this stage is steadily pumped from normal pressure to an absolute pressure of 500Pa, the temperature is controlled at 260°C, and the reaction time is 50 minutes; then the vacuum is continued to reduce the reaction pressure to an absolute pressure of 68Pa, and a high vacuum stage polycondensation reaction is carried out. The reaction temperature is controlled at 275°C, and the reaction time is 90 minutes; after the polycondensation is completed, the material is discharged and granulated to obtain the modified polyester; (2) Preparation of compatibilizer; S1 4,4'-azo (4-cyanovaleric acid), methyl methacrylate and thioglycolic acid are added to a reaction kettle in sequence, and then tetrahydrofuran is added to dissolve, and the mixture is reacted in a nitrogen atmosphere at 60° C. for 5 hours. After the reaction is completed, the product is purified and dried to obtain carboxyl-containing polymethyl methacrylate; wherein the molar ratio of methyl methacrylate, thioglycolic acid and 4,4'-azo (4-cyanovaleric acid) is 100:5:1, and the mass ratio of methyl methacrylate to tetrahydrofuran is 1:1; S2: Poly(ethylene-co-glycidyl methacrylate) and carboxyl-containing polymethyl methacrylate in a mass ratio of 100:5 are dried separately, added into an internal mixer together with dibenzoyl peroxide (the amount is 0.2% of the total mass of poly(ethylene-co-glycidyl methacrylate) and carboxyl-containing polymethyl methacrylate), and granulated by internal mixing to obtain poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate; wherein the temperature of the internal mixer is 180°C, the speed is 50 rpm, and the mixing time is 10 min; S3: Polyethylene and poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate) in a mass ratio of 100:3 are dried separately and added into an internal mixer, and granulated by internal mixer to obtain a polyethylene and poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate graft copolymer, i.e., a compatibilizer; wherein the temperature of the internal mixer is 180°C, the speed is 50 rpm, and the internal mixer time is 10 min; (3) Spinning; S1 The dried polyethylene is melted by the screw, and the measured polyethylene melt enters the spinning box A; wherein the screw melting temperature is 220°C, and the polyethylene melt conveying temperature is 260°C; S2 The dried modified polyester and the compatibilizer are mixed in a mass ratio of 100:2.5, and then melted and exhausted by the screw in sequence. The metered mixed melt enters the spinning box B; wherein the screw melting temperature is 260°C, and the mixed melt conveying temperature is 275°C; S3 The melt in spinning box A and spinning box B is ejected through the composite spinneret in a weight ratio of 40:60 to form filaments with a skin-core structure, and then spun, cooled, bundled, stretched, curled, cut and dried in sequence to obtain ultrafine polyethylene / polyester composite fibers; wherein, the spinning temperature is 275°C and the spinning speed is 1000m / min; cooling is carried out by ring air cooling, the ring air temperature is 14°C, and the ring air speed is 1.0m / s; the first stretching temperature is 70°C, the second stretching temperature is 100°C, and the total stretching multiple is 3.4 times; the drying temperature is 100°C.

[0026] The final ultrafine polyethylene / polyester composite fiber has a single filament fineness of 0.6 dtex, a breaking strength of 3.30 cN / dtex, a breaking elongation of 60%, a curl number of 13 / 25 mm, a curl degree of 14%, and a fiber length of 35 mm.

[0027] Example 2 A method for preparing ultrafine polyethylene / polyester composite fibers, the specific steps are as follows: (1) Preparation of modified polyester; S1: terephthalic acid, isophthalic acid and ethylene glycol in a molar ratio of 1:0.3:1.9 are prepared into a slurry, and then an esterification reaction is carried out. The reaction is carried out under a nitrogen atmosphere under a pressure of normal pressure and a reaction temperature of 230° C. When the amount of water distilled in the esterification reaction reaches 96% of the theoretical value, the esterification reaction is terminated to obtain an esterification product. S2 After the esterification reaction of step S1 is completed, under the action of antimony trioxide catalyst (the amount added is 0.02% of the total weight of terephthalic acid and isophthalic acid) and triphenyl phosphate stabilizer (the amount added is 0.02% of the total weight of terephthalic acid and isophthalic acid), a low vacuum stage polycondensation reaction is started under negative pressure conditions. The pressure in this stage is steadily pumped from normal pressure to an absolute pressure of 480Pa, the temperature is controlled at 262°C, and the reaction time is 35 minutes; then the vacuum is continued to reduce the reaction pressure to an absolute pressure of 68Pa, and a high vacuum stage polycondensation reaction is carried out, the reaction temperature is controlled at 277°C, and the reaction time is 85 minutes; after the polycondensation is completed, the material is discharged and granulated to obtain the modified polyester; (2) Preparation of compatibilizer; S1 4,4'-azo (4-cyanovaleric acid), methyl methacrylate and thioglycolic acid are added to a reaction kettle in sequence, and then tetrahydrofuran is added to dissolve, and the mixture is reacted in a nitrogen atmosphere at 62°C for 5 hours. After the reaction is completed, the product is purified and dried to obtain carboxyl-containing polymethyl methacrylate; wherein the molar ratio of methyl methacrylate, thioglycolic acid and 4,4'-azo (4-cyanovaleric acid) is 100:5:1.5, and the mass ratio of methyl methacrylate to tetrahydrofuran is 1:1.2; S2: Poly(ethylene-co-glycidyl methacrylate) and carboxyl-containing polymethyl methacrylate in a mass ratio of 100:6 are dried separately, and then added into an internal mixer together with dibenzoyl peroxide (the amount is 0.25% of the total mass of poly(ethylene-co-glycidyl methacrylate) and carboxyl-containing polymethyl methacrylate), and granulated by internal mixing to obtain poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate; wherein the temperature of the internal mixer is 180°C, the speed is 55 rpm, and the mixing time is 10 min; S3: Polyethylene and poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate) in a mass ratio of 100:3 are dried separately and added into an internal mixer, and granulated by internal mixer to obtain a polyethylene and poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate graft copolymer, i.e., a compatibilizer; wherein the temperature of the internal mixer is 185°C, the speed is 55 rpm, and the internal mixer time is 12 min; (3) Spinning; S1 The dried polyethylene is melted by the screw, and the measured polyethylene melt enters the spinning box A; wherein the screw melting temperature is 225°C, and the polyethylene melt conveying temperature is 261°C; S2 The dried modified polyester and the compatibilizer are mixed in a mass ratio of 100:3, and then melted and exhausted by the screw in sequence. The metered mixed melt enters the spinning box B; wherein the screw melting temperature is 262°C, and the mixed melt conveying temperature is 277°C; S3 The melt in spinning box A and spinning box B is ejected through the composite spinneret in a weight ratio of 50:50 to form filaments with a skin-core structure, and then spun, cooled, bundled, stretched, curled, cut and dried in sequence to obtain ultrafine polyethylene / polyester composite fibers; wherein, the spinning temperature is 277°C and the spinning speed is 1150m / min; cooling is carried out by ring air cooling, the ring air temperature is 15°C, and the ring air speed is 1.1m / s; the first stretching temperature is 70°C, the second stretching temperature is 100°C, and the total stretching multiple is 3.4 times; the drying temperature is 100°C.

[0028] The final ultrafine polyethylene / polyester composite fiber has a single filament fineness of 0.75 dtex, a breaking strength of 3.46 cN / dtex, a breaking elongation of 55%, a curl number of 16 / 25 mm, a curl degree of 18%, and a fiber length of 38 mm.

[0029] Example 3 A method for preparing ultrafine polyethylene / polyester composite fibers, the specific steps are as follows: (1) Preparation of modified polyester; S1: terephthalic acid, isophthalic acid and ethylene glycol in a molar ratio of 1:0.4:2.3 are prepared into a slurry, and then an esterification reaction is carried out. The reaction is carried out under a nitrogen atmosphere under a pressure of 0.15 MPa and a reaction temperature of 235°C. When the amount of water distilled during the esterification reaction reaches 98.5% of the theoretical value, the esterification reaction is terminated to obtain an esterified product. S2 After the esterification reaction of step S1 is completed, under the action of the catalyst antimony glycol (the amount added is 0.02% of the total weight of terephthalic acid and isophthalic acid) and the stabilizer trimethyl phosphate (the amount added is 0.02% of the total weight of terephthalic acid and isophthalic acid), a low vacuum stage polycondensation reaction is started under negative pressure conditions. The pressure in this stage is steadily pumped from normal pressure to an absolute pressure of 490Pa, the temperature is controlled at 265°C, and the reaction time is 40 minutes; then the vacuum is continued to reduce the reaction pressure to an absolute pressure of 65Pa, and a high vacuum stage polycondensation reaction is carried out, the reaction temperature is controlled at 278°C, and the reaction time is 70 minutes; after the polycondensation is completed, the material is discharged and granulated to obtain the modified polyester; (2) Preparation of compatibilizer; S1 4,4'-azo (4-cyanovaleric acid), methyl methacrylate and thioglycolic acid are added to a reaction kettle in sequence, and then tetrahydrofuran is added to dissolve, and the mixture is reacted in a nitrogen atmosphere at 65°C for 4.5 hours. After the reaction is completed, the product is purified and dried to obtain carboxyl-containing polymethyl methacrylate; wherein the molar ratio of methyl methacrylate, thioglycolic acid and 4,4'-azo (4-cyanovaleric acid) is 100:4.5:1, and the mass ratio of methyl methacrylate to tetrahydrofuran is 1:1.2; S2: Poly(ethylene-co-glycidyl methacrylate) and carboxyl-containing polymethyl methacrylate in a mass ratio of 100:6.5 are dried separately, added into an internal mixer together with dibenzoyl peroxide (the amount is 0.3% of the total mass of poly(ethylene-co-glycidyl methacrylate) and carboxyl-containing polymethyl methacrylate), and granulated by internal mixing to obtain poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate; wherein the temperature of the internal mixer is 185°C, the speed is 55 rpm, and the mixing time is 9 min; S3: Polyethylene and poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate) in a mass ratio of 100:3.5 are dried separately and added into an internal mixer, and granulated by internal mixer to obtain a polyethylene and poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate graft copolymer, i.e., a compatibilizer; wherein the temperature of the internal mixer is 187°C, the speed is 55 rpm, and the internal mixer time is 12 min; (3) Spinning; S1 The dried polyethylene is melted by the screw, and the measured polyethylene melt enters the spinning box A; wherein the screw melting temperature is 230°C, and the polyethylene melt conveying temperature is 265°C; S2 The dried modified polyester and the compatibilizer are mixed in a mass ratio of 100:3.5, and then melted and exhausted by the screw in sequence. The metered mixed melt enters the spinning box B; wherein the screw melting temperature is 265°C, and the mixed melt conveying temperature is 276°C; S3 The melt in spinning box A and spinning box B is ejected through the composite spinneret in a weight ratio of 50:50 to form filaments with a skin-core structure, and then spun, cooled, bundled, stretched, curled, cut and dried in sequence to obtain ultrafine polyethylene / polyester composite fibers; wherein, the spinning temperature is 278°C and the spinning speed is 1200m / min; cooling is carried out by ring air cooling, the ring air temperature is 15°C, and the ring air speed is 1.1m / s; the first stretching temperature is 72°C, the second stretching temperature is 100°C, and the total stretching multiple is 3.45 times; the drying temperature is 105°C.

[0030] The final ultrafine polyethylene / polyester composite fiber has a single filament fineness of 0.8 dtex, a breaking strength of 3.55 cN / dtex, a breaking elongation of 50%, a curl number of 14 / 25 mm, a curl degree of 15%, and a fiber length of 38 mm.

[0031] Example 4 A method for preparing ultrafine polyethylene / polyester composite fibers, the specific steps are as follows: (1) Preparation of modified polyester: S1: terephthalic acid, isophthalic acid and ethylene glycol in a molar ratio of 1:0.5:2.3 are prepared into a slurry, and then an esterification reaction is carried out. The reaction is carried out under a nitrogen atmosphere under a pressure of 0.2 MPa and a reaction temperature of 240°C. When the amount of water distilled during the esterification reaction reaches 98% of the theoretical value, the esterification reaction is terminated to obtain an esterified product. S2 After the esterification reaction of step S1 is completed, under the action of the catalyst antimony glycol (the amount added is 0.05% of the total weight of terephthalic acid and isophthalic acid) and the stabilizer trimethyl phosphite (the amount added is 0.05% of the total weight of terephthalic acid and isophthalic acid), a low vacuum stage polycondensation reaction is started under negative pressure conditions. The pressure in this stage is steadily pumped from normal pressure to an absolute pressure of 485Pa, the temperature is controlled at 270°C, and the reaction time is 40 minutes; then the vacuum is continued to reduce the reaction pressure to an absolute pressure of 63Pa, and a high vacuum stage polycondensation reaction is carried out, the reaction temperature is controlled at 280°C, and the reaction time is 60 minutes; after the polycondensation is completed, the material is discharged and granulated to obtain the modified polyester; (2) Preparation of compatibilizer; S1 4,4'-azo (4-cyanovaleric acid), methyl methacrylate and thioglycolic acid are added to a reaction kettle in sequence, and then tetrahydrofuran is added to dissolve, and the mixture is reacted in a nitrogen atmosphere at 60° C. for 4 hours. After the reaction is completed, the product is purified and dried to obtain carboxyl-containing polymethyl methacrylate; wherein the molar ratio of methyl methacrylate, thioglycolic acid and 4,4'-azo (4-cyanovaleric acid) is 100:6:1.2, and the mass ratio of methyl methacrylate to tetrahydrofuran is 1:1.5; S2: Poly(ethylene-co-glycidyl methacrylate) and carboxyl-containing polymethyl methacrylate in a mass ratio of 100:7 are dried separately, added into an internal mixer together with dibenzoyl peroxide (the amount is 0.3% of the total mass of poly(ethylene-co-glycidyl methacrylate) and carboxyl-containing polymethyl methacrylate), and granulated by internal mixing to obtain poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate; wherein the temperature of the internal mixer is 190°C, the speed is 55 rpm, and the mixing time is 8 min; S3: Polyethylene and poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate) in a mass ratio of 100:5 are dried separately and added into an internal mixer, and granulated by internal mixer to obtain a polyethylene and poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate graft copolymer, i.e., a compatibilizer; wherein the temperature of the internal mixer is 190°C, the speed is 60rpm, and the internal mixer time is 15min; (3) Spinning; S1 The dried polyethylene is melted by the screw, and the measured polyethylene melt enters the spinning box A; wherein the screw melting temperature is 240°C, and the polyethylene melt conveying temperature is 264°C; S2 The dried modified polyester and the compatibilizer are mixed in a mass ratio of 100:2.5, and then melted and exhausted by the screw in sequence. The metered mixed melt enters the spinning box B; wherein the screw melting temperature is 270°C, and the mixed melt conveying temperature is 280°C; S3 The melt in spinning box A and spinning box B is ejected through the composite spinneret in a weight ratio of 50:50 to form filaments with a skin-core structure, and then spun, cooled, bundled, stretched, curled, cut and dried in sequence to obtain ultrafine polyethylene / polyester composite fibers; wherein, the spinning temperature is 280°C and the spinning speed is 1200m / min; cooling is carried out by ring air cooling, the ring air temperature is 18°C, and the ring air speed is 1.2m / s; the first stretching temperature is 74°C, the second stretching temperature is 100°C, and the total stretching multiple is 3.5 times; the drying temperature is 110°C.

[0032] The final ultrafine polyethylene / polyester composite fiber has a single filament fineness of 0.7 dtex, a breaking strength of 3.63 cN / dtex, a breaking elongation of 45%, a curl number of 15 / 25mm, a curl degree of 16%, and a fiber length of 40 mm.

[0033] Example 5 A method for preparing ultrafine polyethylene / polyester composite fibers, the specific steps are as follows: (1) Preparation of modified polyester; S1: terephthalic acid, isophthalic acid and ethylene glycol in a molar ratio of 1:0.3:2.1 are prepared into a slurry, and then an esterification reaction is carried out. The reaction is carried out under a nitrogen atmosphere under a pressure of 0.3 MPa and a reaction temperature of 250°C. When the amount of water distilled in the esterification reaction reaches 99% of the theoretical value, the esterification reaction ends, and an esterification product is obtained; S2 After the esterification reaction of step S1 is completed, under the action of antimony acetate catalyst (the amount added is 0.05% of the total weight of terephthalic acid and isophthalic acid) and trimethyl phosphite stabilizer (the amount added is 0.05% of the total weight of terephthalic acid and isophthalic acid), a low vacuum stage polycondensation reaction is started under negative pressure conditions. The pressure in this stage is steadily pumped from normal pressure to an absolute pressure of 480Pa, the temperature is controlled at 270°C, and the reaction time is 30 minutes; then the vacuum is continued to reduce the reaction pressure to an absolute pressure of 65Pa, and a high vacuum stage polycondensation reaction is carried out, the reaction temperature is controlled at 280°C, and the reaction time is 50 minutes; after the polycondensation is completed, the material is discharged and granulated to obtain the modified polyester; (2) Preparation of compatibilizer; S1 4,4'-azo (4-cyanovaleric acid), methyl methacrylate and thioglycolic acid are added to a reaction kettle in sequence, and then tetrahydrofuran is added to dissolve, and the mixture is reacted in a nitrogen atmosphere at 62°C for 4.2 hours. After the reaction is completed, the product is purified and dried to obtain carboxyl-containing polymethyl methacrylate; wherein the molar ratio of methyl methacrylate, thioglycolic acid and 4,4'-azo (4-cyanovaleric acid) is 100:5:1.5, and the mass ratio of methyl methacrylate to tetrahydrofuran is 1:1.5; S2: Poly(ethylene-co-glycidyl methacrylate) and carboxyl-containing polymethyl methacrylate in a mass ratio of 100:8 are dried separately, added into an internal mixer together with dibenzoyl peroxide (the amount is 0.3% of the total mass of poly(ethylene-co-glycidyl methacrylate) and carboxyl-containing polymethyl methacrylate), and granulated by internal mixing to obtain poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate; wherein the temperature of the internal mixer is 190°C, the speed is 60 rpm, and the mixing time is 8 min; S3: Polyethylene and poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate) in a mass ratio of 100:5 are dried separately and added into an internal mixer, and granulated by internal mixer to obtain a polyethylene and poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate graft copolymer, i.e., a compatibilizer; wherein the temperature of the internal mixer is 190°C, the speed is 60rpm, and the internal mixer time is 15min; (3) Spinning; S1 The dried polyethylene is melted by the screw, and the measured polyethylene melt enters the spinning box A; wherein the screw melting temperature is 250°C, and the polyethylene melt conveying temperature is 265°C; S2 The dried modified polyester and the compatibilizer are mixed in a mass ratio of 100:2.8, and then melted and exhausted by the screw in sequence. The metered mixed melt enters the spinning box B; wherein the screw melting temperature is 270°C, and the mixed melt conveying temperature is 280°C; S3 The melt in spinning box A and spinning box B is ejected through the composite spinneret in a weight ratio of 60:40 to form filaments with a skin-core structure, and then spun, cooled, bundled, stretched, curled, cut and dried in sequence to obtain ultrafine polyethylene / polyester composite fibers; wherein, the spinning temperature is 280°C and the spinning speed is 1200m / min; cooling is carried out by ring air cooling, the ring air temperature is 18°C, and the ring air speed is 1.2m / s; the first stretching temperature is 75°C, the second stretching temperature is 100°C, and the total stretching multiple is 3.6 times; the drying temperature is 110°C.

[0034] The final ultrafine polyethylene / polyester composite fiber has a single filament fineness of 0.65 dtex, a breaking strength of 3.70 cN / dtex, a breaking elongation of 40%, a curl number of 16 / 25 mm, a curl degree of 18%, and a fiber length of 38 mm.

Claims

1. An ultrafine polyethylene / polyester composite fiber, characterized in that: The single fiber fineness of the ultrafine polyethylene / polyester composite fiber is 0.6-0.8 dtex; The ultrafine polyethylene / polyester composite fiber has a skin-core structure, the skin layer is made of polyethylene, and the core layer is made of a blend of modified polyester and a compatibilizer; The molecular chain of the modified polyester consists of a terephthalic acid segment, an ethylene glycol segment and an isophthalic acid segment; The compatibilizer is polyethylene and poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate graft copolymer.

2. The ultrafine polyethylene / polyester composite fiber according to claim 1, characterized in that: The ultrafine polyethylene / polyester composite fiber has a breaking strength of 3.3-3.7 cN / dtex, a breaking elongation of 50.0±10.0%, a crimp number of 13-16 / 25mm, and a crimp degree of 14-18%.

3. The ultrafine polyethylene / polyester composite fiber according to claim 1, characterized in that: The skin-to-core weight ratio of the skin-to-core structure is 40-50:50-60.

4. The ultrafine polyethylene / polyester composite fiber according to claim 1, characterized in that: The melt index of the polyethylene measured at a temperature of 190° C. and a pressure of 0.3 MPa is 20±2 g / 10 min, and the intrinsic viscosity of the modified polyester is 0.64-0.66 dL / g.

5. The ultrafine polyethylene / polyester composite fiber according to claim 4, characterized in that: The preparation process of the modified polyester is as follows: (1) After terephthalic acid, isophthalic acid and ethylene glycol are prepared into a slurry, an esterification reaction is carried out, and the reaction is carried out under a nitrogen atmosphere under a pressure of normal pressure to 0.3 MPa and a reaction temperature of 230 to 250°C. When the amount of water distilled during the esterification reaction reaches more than 95% of the theoretical value, the esterification reaction ends, and an esterification product is obtained; (2) After the esterification reaction in step (1) is completed, a low vacuum stage polycondensation reaction is started under negative pressure under the action of a catalyst and a stabilizer. The pressure in this stage is evacuated from normal pressure to an absolute pressure below 500 Pa, the temperature is controlled at 260-270° C., and the reaction time is 30-50 minutes. Then, the vacuum is continued to be evacuated to reduce the reaction pressure to an absolute pressure of less than 70 Pa, and a high vacuum stage polycondensation reaction is carried out. The reaction temperature is controlled at 275-280° C., and the reaction time is 50-90 minutes. After the polycondensation is completed, the material is discharged and granulated to obtain the modified polyester.

6. The ultrafine polyethylene / polyester composite fiber according to claim 5, characterized in that: In step (1), the molar ratio of terephthalic acid, isophthalic acid and ethylene glycol is 1:0.3-0.5:1.7-2.3; In step (2), the catalyst is antimony trioxide, ethylene glycol antimony or antimony acetate, and the stabilizer is triphenyl phosphate, trimethyl phosphate or trimethyl phosphite; the amount of the catalyst added is 0.01% to 0.05% of the total weight of terephthalic acid and isophthalic acid, and the amount of the stabilizer added is 0.01% to 0.05% of the total weight of terephthalic acid and isophthalic acid.

7. The ultrafine polyethylene / polyester composite fiber according to claim 1, characterized in that: The preparation process of the compatibilizer is as follows: (1) 4,4'-azo(4-cyanovaleric acid), methyl methacrylate and thioglycolic acid are added to a reaction kettle in sequence, and then tetrahydrofuran is added to dissolve, and the mixture is reacted in a nitrogen atmosphere at 60-65°C for 4-5 hours. After the reaction is completed, the product is purified and dried to obtain carboxyl-containing polymethyl methacrylate; (2) After drying, poly(ethylene-co-glycidyl methacrylate) and carboxyl-containing polymethyl methacrylate are added to an internal mixer together with dibenzoyl peroxide, and granulated by internal mixing to obtain poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate; wherein the temperature of the internal mixer is 180-190° C., the speed is 50-60 rpm, and the mixing time is 8-10 min; (3) The polyethylene and poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate) are dried separately and added into an internal mixer, and the compatibilizer is obtained by internal mixer granulation; wherein the temperature of the internal mixer is 180-190°C, the rotation speed is 50-60 rpm, and the internal mixer time is 10-15 min.

8. The ultrafine polyethylene / polyester composite fiber according to claim 7, characterized in that: In step (1), the molar ratio of methyl methacrylate, thioglycolic acid and 4,4'-azo(4-cyanovaleric acid) is 100:5-6:1-1.5, and the mass ratio of methyl methacrylate to tetrahydrofuran is 1:1-1.5; In step (2), the mass ratio of poly(ethylene-co-glycidyl methacrylate) to carboxyl-containing polymethyl methacrylate is 100:5-8, and the amount of dibenzoyl peroxide is 0.2%-0.3% of the total mass of poly(ethylene-co-glycidyl methacrylate) and carboxyl-containing polymethyl methacrylate; In step (3), the mass ratio of polyethylene to poly(ethylene-co-glycidyl methacrylate)-g-polymethyl methacrylate is 100:3-5.

9. The method for preparing an ultrafine polyethylene / polyester composite fiber according to any one of claims 1 to 8, characterized in that: The ultrafine polyethylene / polyester composite fiber is prepared according to a core-skin composite spinning process, which specifically includes the following steps: (1) The dried polyethylene is melted by the screw, and the measured polyethylene melt enters the spinning box A; (2) The dried modified polyester and the compatibilizer are mixed in a mass ratio of 100:2.5-3.5, and then melted and exhausted by the screw in sequence. The metered mixed melt enters the spinning box B; (3) The melt in spinning beam A and spinning beam B is ejected through a composite spinneret to form a filament with a sheath-core structure, which is then spun, cooled, bundled, stretched, curled, cut, and dried in sequence to obtain ultrafine polyethylene / polyester composite fibers.

10. The method for preparing ultrafine polyethylene / polyester composite fibers according to claim 9, characterized in that: In step (1), the screw melting temperature is 220-250°C, and the polyethylene melt conveying temperature is 260-265°C; In step (2), the screw melting temperature is 260-270°C, and the mixed melt conveying temperature is 275-280°C; In step (3), the spinning temperature is 275-280°C, and the spinning speed is 1000-1200 m / min; the cooling adopts ring air cooling, the ring air temperature is 14-18°C, and the ring air speed is 1.0-1.2 m / s; the first stretching temperature is 70-75°C, the second stretching temperature is 100°C, and the total stretching multiple is 3.4-3.6 times; the drying temperature is 100-110°C.