Process for the production of super-slick soft polyester staple fibers

Abstract

The present application relates to a kind of preparation methods of super smooth soft polyester staple fiber, modified copolyester is prepared by melt spinning and post-processing super smooth soft polyester staple fiber;Modified copolyester is prepared by melt blending of lubricating functional masterbatch and flexible polyester chip;Lubricating functional masterbatch is prepared by terephthalic acid, ethylene glycol and polydimethylsiloxane copolymerization, and flexible polyester chip is prepared by terephthalic acid, ethylene glycol and third monomer copolymerization.The preparation method of super smooth soft polyester staple fiber of the present application solves the compatibility problem of lubricating functional masterbatch and flexible polyester chip by the micro chain extension of polydimethylsiloxane containing terminal hydroxyl group, improves the interface effect, so that polyester staple fiber has mechanical properties and lubricating property, the friction coefficient is 0.05~0.15, the breaking strength is 3.5~5 cN / dtex, the breaking elongation is 150~300%, and the contact angle is ≥100 °.

Description

Technical Field

[0001] This invention belongs to the field of polyester staple fiber technology and relates to a method for preparing ultra-smooth and soft polyester staple fiber. Background Technology

[0002] Polyester fiber accounts for more than 50% of textile fibers, making it the most important source of textile fibers globally. The technology of using polyethylene terephthalate (PET) as a matrix to modify and prepare multifunctional polyester fibers has become a major, efficient, low-cost, and energy-saving process. Existing modified PET polyesters are widely used in functional areas such as flame retardancy, water repellency, moisture absorption, resilience, and warmth retention. With social progress and economic development, people are constantly raising new demands for the comfort of textile products, especially in terms of feel, requiring smoothness, softness, and fluffiness.

[0003] The softness of fiber materials, also known as the softness of fibers or fabrics, reflects the material's rigidity and flexibility. Softness is one of the important indicators for evaluating the wearability of fibers and determining their application range. Smoothness, softness, and stiffness determine the physical and mechanical properties of fabrics. When touching a fabric, its quality can be subjectively assessed. Fabrics that are easily compressed are likely to be considered soft and have a low compression modulus and high compressibility. Any fabric that generates little frictional resistance when moving across its surface has a low coefficient of friction and can be called a smooth fabric. Among commonly used clothing fibers, wool fibers are long and thin with a low initial modulus, resulting in fabrics that are soft, delicate to the touch, warm, and comfortable against the skin. Among synthetic fibers, nylon has a low modulus, good abrasion resistance, and a soft, smooth feel, and is often used to make underwear.

[0004] In existing ultra-soft polyester fiber preparation technologies, patent CN106283260A introduces branched hexanediols (such as one or more of 2-pentyl-1,6-hexanediol, 2-hexyl-1,6-hexanediol, 2-heptyl-1,6-hexanediol, 2-octyl-1,6-hexanediol, 2-nonyl-1,6-hexanediol, or 2-decyl-1,6-hexanediol) to prepare copolymerized modified polyesters and porous ultra-soft polyester fiber FDY filaments, achieving an initial modulus ≤70cN / dtex. This achieves a soft effect while improving the fiber's dyeing ability. However, long-chain 1,6-hexanediols have low reactivity and require harsh reaction conditions. The presence of branches leads to a significant decrease in melting point, affecting crystallization performance. At the same time, branched 1,6-hexanediols undergo side reactions during polymerization, easily cyclizing to form cyclic oligomers. Increased oligomer content can lead to difficulties in spinning and forming, and reduced fiber breaking strength and elongation at break.

[0005] Patent CN106381547A describes a modified polyester fabric prepared from terephthalic acid segments, ethylene glycol segments, and branched hexanediol segments. This modified polyester is then spun into porous, ultra-soft polyester POY fibers using a porous spinneret. The introduction of branched hexanediol segments reduces the initial modulus and improves softness compared to traditional polyester fibers, achieving an initial modulus ≤70 cN / dtex. However, while the use of branched diol segments effectively enhances softness, it also reduces melt viscosity and tensile strength, limiting its processing and applications.

[0006] In existing technologies for preparing smooth and soft polyester, patent CN103603086A involves adding modified organosilicon (which possesses both smoothness and softness) to aromatic diacids and aliphatic diols for in-situ polymerization to obtain organosilicon polyester composite materials. These materials are then spun to produce polyester fibers. The resulting fibers exhibit both softness and smoothness, eliminating the need for softening finishing processes and reducing the discharge of organic wastewater during dyeing and finishing. However, this type of organosilicon polyester composite material involves copolymerization with polyether-modified organosilicon after esterification. The resulting polymer is a block copolymer, and the long-chain organosilicon has low transesterification activity. This leads to a significant difference between the actual copolymerization ratio and the feed ratio, a high polydispersity index (a drawback of organosilicon block copolymers), uneven molecular weight distribution, uncontrollable melting temperature, and difficulty in crystallization. Subsequent drying to reduce moisture content is also challenging. Direct use in spinning results in breakage, and process control is difficult.

[0007] Blending modification is a method of mechanically mixing polymers using mixing equipment. It is simple to operate, widely applicable, and low-cost. However, this method requires high compatibility, crystallinity, and thermal properties between the two components of the blend. If the melting and crystallization temperatures of the two components differ too much at the same processing temperature, it will lead to a large difference in their flowability during melt extrusion, resulting in uneven blending. For example, the literature (Preparation of Super-Soft PBT Fibers and Their Properties Based on Masterbatch Blending Modification [D]. Donghua University, 2020. DOI:10.27012 / d.cnki.gdhuu.2019.000343.) uses PDMS masterbatch with a melting point of 190–210℃ and PBT chips with a melting point of 225℃ to prepare smooth and soft fibers. The melting points of the two components are close, which makes them relatively homogeneous during melt blending. The blend exhibits good compatibility under the same processing temperature. The effect of PDMS masterbatch addition on the properties of the blended fibers was investigated. With the increase of PDMS masterbatch addition, the elongation of the blended fibers increased to 32.5%, while the initial modulus decreased to 21.7 cN / dtex. The compatibility between PDMS masterbatch and PBT deteriorated with the increase of PDMS masterbatch content, which also led to a decrease in breaking strength from 3.4 cN / dtex to 2.9 cN / dtex, resulting in defects in mechanical properties. In addition, SEM revealed that PDMS masterbatch was distributed in the PBT matrix in the form of micron-sized microspheres, forming an island-type structure. When the PDMS content was higher than 8 wt%, the microsphere morphology was more obvious. Excessive addition of polysiloxane could cause microsphere rupture, leading to poor compatibility and insufficient interfacial forces, which may result in discontinuous and uneven fiber properties.

[0008] Therefore, it is of great significance to study a method for preparing ultra-smooth and soft polyester staple fiber in order to solve the problem that it is difficult to achieve the same mechanical properties, softness and smoothness of fibers in the existing technology. Summary of the Invention

[0009] The purpose of this invention is to solve the above-mentioned problems existing in the prior art and to provide a method for preparing ultra-smooth and soft polyester staple fibers.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A method for preparing ultra-smooth and soft polyester staple fiber, wherein modified copolyester is melt-spun and post-processed to obtain ultra-smooth and soft polyester staple fiber;

[0012] The modified copolyester was prepared by melt blending lubricating masterbatch and flexible polyester chips;

[0013] The lubricating masterbatch is prepared by copolymerization of terephthalic acid, ethylene glycol and polydimethylsiloxane, and the flexible polyester chips are prepared by copolymerization of terephthalic acid, ethylene glycol and a third monomer.

[0014] The terminal structure of polydimethylsiloxane is either hydroxyl-terminated (CAS 70131-67-8) or hydroxyl-alkyl-terminated (CAS 70131-67-8 or 156327-07-0); the number average molecular weight of polydimethylsiloxane is 500-3000 g / mol, and the dynamic viscosity is 20-75 mPa·s. After esterification, polydimethylsiloxane is added to the esterified product of PTA and ethylene glycol to prepare block copolyester as a lubricating masterbatch. The molecular chain length of polydimethylsiloxane affects the thermal properties of the lubricating masterbatch. In order to make the thermal properties closer to those of flexible polyester chips and improve the compatibility between the lubricating masterbatch and flexible polyester chips, polydimethylsiloxane in this number average molecular weight range is selected.

[0015] The third monomer is polyethylene glycol with a number average molecular weight of 400–2000 g / mol or polytetrahydrofuran with a number average molecular weight of 250–2000 g / mol; introducing polyether segments into flexible polyester chips, polyether and polysiloxane are structurally similar and have similar melting points, which is beneficial to improving the compatibility and flexibility of the lubricating masterbatch and flexible polyester chips.

[0016] The terminal hydroxyl groups of the lubricating masterbatch include Si-OH (or Si-(CH2)2-O-(CH2)2-OH) and CH2-OH. The high mobility and reactivity of Si-OH (or Si-(CH2)2-O-(CH2)2-OH) make it easier to undergo micro-chain extension reactions with the C-OH (terminal hydroxyl group CH2-OH, terminal carboxyl group HO-CO-CH2) remaining in the flexible polyester chips during the blending process to form Si-OC bonds. Long-chain polydimethylsiloxanes can only undergo micro-chain extension reactions. This invention introduces long-chain polydimethylsiloxanes to optimize interfacial interactions and improve the compatibility of lubricating masterbatches and flexible polyester chips. Without polydimethylsiloxanes, the terminal hydroxyl groups of conventional diols have low activity, resulting in extremely weak reactions between the two phases, and micro-chain extension will not occur at the interface through bonding. In the prior art, short-chain siloxanes have a high Si-OH content and are often used as silane coupling agents to undergo chain extension reactions and improve interfacial interactions. However, the intense chain extension reaction is uncontrollable in the twin-screw melt extrusion blending process, leading to uneven molecular weight distribution and high polydispersity coefficient of the melt-extruded blend chips. Ultimately, this results in discontinuous melt spinning or affects the coefficient of variation of the fibers. Therefore, the intense chain extension reaction is not suitable for the blending system of this invention.

[0017] As a preferred technical solution:

[0018] In the preparation method of the super smooth and soft polyester staple fiber described above, the melting point of the lubricating masterbatch is 180-200℃; based on the lubricating masterbatch, the amount of polydimethylsiloxane added is 10-20wt%.

[0019] The intrinsic viscosity of flexible polyester chips is 0.65–0.85 dl / g, and the melting point is 200–220℃. The melting point of the lubricating masterbatch is slightly lower than that of the flexible polyester chips. This is to ensure that the melt of the lubricating masterbatch has better fluidity under the same melting temperature, so that it can be evenly dispersed into the melt of the flexible polyester chips.

[0020] The introduction of flexible chain segments to control the melting point of flexible polyester chips not only further improves the compatibility of the two components during processing, but also enhances the softness of the modified copolyester.

[0021] The preparation steps of the lubricating masterbatch in the above-described method for preparing ultra-smooth and soft polyester staple fiber are as follows:

[0022] (1) Under the conditions of adding catalyst, heat stabilizer and anti-ether agent, terephthalic acid and ethylene glycol are esterified at a molar ratio of 1:1.2 to 1.4 until the water content reaches more than 95%; the amount of catalyst, heat stabilizer and anti-ether agent added is 300 ppm; the esterification temperature is 200 to 230℃ and the esterification time is 3 to 4 h.

[0023] (2) After esterification, polydimethylsiloxane is added. First, vacuum is applied for 40-60 minutes until the absolute vacuum reaches below 50 Pa. At the same time, the temperature is raised from the esterification temperature to 268-272℃ during the vacuuming process. Then, the power of the stirrer is observed to increase until the power of the stirrer no longer increases. The viscosity of the product reaches the limit, the reaction ends, and the lubricating masterbatch is obtained.

[0024] The preparation steps of the flexible polyester chips according to the above-described method for preparing ultra-smooth and soft polyester staple fibers are as follows:

[0025] (1) Under the conditions of adding catalyst, heat stabilizer and anti-ether agent, terephthalic acid and ethylene glycol are esterified at a molar ratio of 1:1.2 to 1.4 until the water content reaches more than 95%; the amount of catalyst, heat stabilizer and anti-ether agent added is 300 ppm; the esterification temperature is 200 to 230℃ and the esterification time is 3 to 4 h.

[0026] (2) After esterification, the third monomer is added. First, vacuum is applied for 40-60 minutes until the absolute vacuum reaches below 50 Pa. At the same time, the temperature is raised from the esterification temperature to 268-272℃ during the vacuuming process. Then, the power of the stirrer is observed to start to rise until the power of the stirrer no longer increases. The viscosity of the product reaches the limit, the reaction ends, and flexible polyester chips are obtained. The amount of the third monomer added is 5-30 wt%, based on the total amount of terephthalic acid, ethylene glycol and the third monomer.

[0027] The preparation method of the super smooth and soft polyester staple fiber as described above uses one or two of the following catalysts: antimony glycolate, antimony trioxide, antimony acetate, tetrabutyl titanate, and isopropyl titanate; the heat stabilizer is one or two of the following: trimethyl phosphate, triphenyl phosphite, and alkyl phosphate diester; and the ether inhibitor is anhydrous sodium acetate.

[0028] The preparation method of the super smooth and soft polyester staple fiber described above has a lubricating functional masterbatch and flexible polyester chips with a mass ratio of 5 to 10:100 and a melt blending temperature of 250 to 270°C.

[0029] The method for preparing ultra-smooth and soft polyester staple fiber as described above involves vacuum drum drying of the modified copolyester before melt spinning. The vacuum drum drying temperature is 90-110°C, and the time is 48 hours. Conventional blended chips do not undergo further solid-phase reactions unless a catalyst is added to increase the temperature for solid-phase polycondensation. The polydimethylsiloxane introduced in this invention has high activity. The modified copolyester utilizes the high activity of polydimethylsiloxane to further induce micro-chain extension reactions between the two phases during blending and vacuum drum drying, thereby optimizing interfacial interactions and improving compatibility.

[0030] The micro-chain extension reaction was characterized by determining the content of terminal hydroxyl and terminal carboxyl groups of the modified copolyester before and after vacuum drum drying using potentiometric titration. The content of terminal hydroxyl and terminal carboxyl groups of the modified copolyester decreased after vacuum drum drying due to the micro-chain extension reaction. Before vacuum drum drying, the content of terminal hydroxyl groups in the modified copolyester was 20-30 mol / t, the content of terminal carboxyl groups was 10-15 mol / t, and the polydispersity index was ≤2.2. After vacuum drum drying, the content of terminal hydroxyl groups was 10-20 mol / t, and the content of terminal carboxyl groups was 5-10 mol / t.

[0031] The preparation method of the super smooth and soft polyester staple fiber described above involves a spinning temperature of 265–270°C and a spinning speed of 600–800 m / min.

[0032] The preparation method of the super-smooth and soft polyester staple fiber described above, according to T / CSTM 00522-2022, yields a friction coefficient of 0.05–0.15. The friction coefficient can be used to characterize the smoothness performance; the better the smoothness, the lower the friction coefficient. The breaking strength of the super-smooth and soft polyester staple fiber is 3.5–5 cN / dtex, the initial modulus is ≤50 cN / dtex, and the breaking elongation is 150–300%. The breaking strength and breaking elongation are tested according to GB / T 14460-2015, and the water contact angle is ≥100°, tested according to GB / T 14210. The rheological properties of the modified copolyester are tested using a dual-barrel capillary rheometer. The melt viscosity of the modified copolyester at the spinning temperature is 10–50 Pa·s, and the softness is ≥100 twists / 200 mm.

[0033] Invention principle:

[0034] The lack of interfacial interaction between existing lubricating masterbatch and flexible polyester chips during direct blending and spinning can lead to problems such as discontinuous and uneven fiber distribution.

[0035] In blending systems, cross-linking can be achieved during the blending process by introducing side chains with reactive groups, forming a three-dimensional network structure to improve melt strength, heat resistance, and weather resistance, and to optimize the interfacial interaction between the two components to improve compatibility. However, the cross-linking reaction that forms a three-dimensional structure can lead to disorder in the ordered linear molecular chain structure, reducing crystallization performance and affecting the drying process of the blended chips. At the same time, the reduced crystallization rate can easily lead to adhesion during the spinning and winding process. Since the conditions for the cross-linking reaction of the two components in the screw at different times are uncontrollable and inconsistent, phenomena such as uneven molecular weight and molecular agglomeration can occur, which can affect the continuity of the spinning and forming process.

[0036] This invention uses PET as the matrix, polydimethylsiloxane as the lubricating modifying monomer to prepare lubricating functional masterbatch, and flexible segments as the third monomer to prepare flexible polyester chips (polydimethylsiloxane is a long-chain monomer; directly copolymerizing terephthalic acid (PTA), ethylene glycol (EG), and the third monomer polyethylene glycol or polytetrahydrofuran with polydimethylsiloxane to prepare ternary multi-block copolymers will lead to uneven polymer molecular weight distribution and unstable performance). Modified copolyester is prepared through melt blending. By blending the lubricating functional masterbatch with the flexible polyester chips to achieve "parallel" molecular chains (i.e., parallel molecular chain arrangement), the problems of wide molecular weight distribution, difficult drying, slow crystallization, and adhesion during spinning in ternary multi-block copolymers found in copolymerization methods are avoided. Specifically:

[0037] Because the lubricating masterbatch of this invention is added via a masterbatch method during the preparation of modified copolyester, and the chain length of polydimethylsiloxane is strictly controlled during the preparation of the lubricating masterbatch, the defects of the prior art, such as wide molecular weight distribution and difficulty in crystallization, are effectively reduced. After introducing long-chain polydimethylsiloxane into the lubricating masterbatch, the terminal hydroxyl groups of the lubricating masterbatch contain Si-OH (or Si-(CH2)2-O-(CH2)2-OH) and CH2-OH. Utilizing the high mobility and reactivity of Si-OH (or Si-(CH2)2-O-(CH2)2-OH) in polydimethylsiloxane, it is easier to undergo micro-chain extension reactions with the C-OH (terminal hydroxyl CH2-OH, terminal carboxyl group HO-CO-CH2) remaining in the flexible polyester chips during blending and vacuum drum drying to form Si-OC bonds, optimizing interfacial interactions and improving compatibility. This solves the problem of incompatibility between the mechanical properties, softness, and smoothness of conventional polyester staple fibers, meeting the market demand for ultra-smooth and soft polyester staple fibers.

[0038] Beneficial effects:

[0039] (1) The present invention provides a method for preparing an ultra-smooth and soft polyester staple fiber. By using the micro-chain extension effect of polydimethylsiloxane, the compatibility problem between the lubricating masterbatch and the flexible polyester chips is solved, the interfacial effect is improved, and the polyester staple fiber takes into account both mechanical properties and soft and smooth properties. The coefficient of friction is 0.05 to 0.15, the breaking strength is 3.5 to 5 cN / dtex, the initial modulus is ≤50 cN / dtex, the breaking elongation is 150 to 300%, and the contact angle is ≥100°.

[0040] (2) The preparation method of the super smooth and soft polyester staple fiber of the present invention has a simple synthesis process and low energy consumption. Polydimethylsiloxane, polyethylene glycol and polytetrahydrofuran have chain extension effects on PET and can effectively polymerize high molecular weight copolyester.

[0041] (3) A method for preparing super smooth and soft polyester staple fiber of the present invention controls the lubrication performance by adjusting the amount of polydimethylsiloxane added in the masterbatch, and prepares polyester staple fiber that meets different application scenarios.

[0042] (4) In response to the problems in patent CN103603086A, this invention uses polydimethylsiloxane to prepare lubricating masterbatch as a reinforcing agent and polyether to prepare flexible polyester chips as a matrix. Then, they are blended to prepare modified copolyester, which can reduce the defects caused by long-chain organosilicon, avoid excessively high molecular weight distribution and difficult crystallization, reduce processing difficulty, simplify process path, realize continuous spinning and forming processing, and at the same time, the flexible polyester chips have longer flexible chain segments, giving the blended chips higher softness. Detailed Implementation

[0043] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0044] The testing standards / methods used in this invention are as follows:

[0045] Breaking strength, elongation at break, and initial modulus: tested according to GB / T 14460-2015;

[0046] Water contact angle: Tested according to GB / T 30693;

[0047] Melt viscosity: Tested using a dual-barrel capillary rheometer (Malvin RH2000) under the following conditions: temperature 265–270 °C, shear rate 1000 s. -1 ;

[0048] Softness: Tested according to GB / T 12411.4-1990 Test method for softness of jute and kenaf fibers using twist meter test method.

[0049] Example 1

[0050] A method for preparing ultra-smooth and soft polyester staple fiber, the specific steps of which are as follows:

[0051] (1) Preparation of raw materials:

[0052] Catalyst: Antimony glycol;

[0053] Heat stabilizer: Trimethyl phosphate;

[0054] Anti-ether agent: anhydrous sodium acetate;

[0055] Terephthalic acid;

[0056] Ethylene glycol;

[0057] Polydimethylsiloxane: Hydroxyl-terminated double-ended polydimethylsiloxane (CAS 70131-67-8), Manufacturer: Adamas, Trademark No.: 77916;

[0058] The third monomer: polyethylene glycol with a number average molecular weight of 400 g / mol;

[0059] (2) Preparation of lubricating masterbatch:

[0060] (2.1) Under the conditions of adding catalyst, heat stabilizer and anti-ether agent, terephthalic acid and ethylene glycol were esterified at a molar ratio of 1:1.2 until the water content reached 95%; wherein, the amount of catalyst, heat stabilizer and anti-ether agent added was 300 ppm; the esterification temperature was 230℃ and the esterification time was 3h.

[0061] (2.2) After esterification, polydimethylsiloxane was added. First, the vacuum was evacuated for 40 minutes until the absolute vacuum reached 50 Pa. At the same time, the temperature was raised to 268°C during the vacuum process. Then, the power of the stirrer was observed to increase until the power of the stirrer stopped increasing. The reaction ended, and a lubricating masterbatch with a melting point of 200°C was obtained. The amount of polydimethylsiloxane added was 10 wt% based on the lubricating masterbatch.

[0062] (3) Preparation of flexible polyester chips:

[0063] (3.1) Under the conditions of adding catalyst, heat stabilizer and anti-ether agent, terephthalic acid and ethylene glycol were esterified at a molar ratio of 1:1.2 until the water content reached 95%; wherein, the amount of catalyst, heat stabilizer and anti-ether agent added was 300 ppm; the esterification temperature was 230℃ and the esterification time was 3h.

[0064] (3.2) After esterification, the third monomer was added. First, the vacuum was evacuated for 40 minutes until the absolute vacuum reached 50 Pa. At the same time, the temperature was raised to 268°C during the vacuuming process. Then, the power of the stirrer was observed to increase until it stopped increasing. The reaction was then complete, and flexible polyester chips with an intrinsic viscosity of 0.85 dl / g and a melting point of 220°C were obtained. The amount of the third monomer added was 5 wt%, based on the total amount of terephthalic acid, ethylene glycol and the third monomer.

[0065] (4) The lubricating masterbatch from step (2) and the flexible polyester chips from step (3) were melt-blended at 250°C at a mass ratio of 5:100 to obtain a modified copolyester; the modified copolyester had a terminal hydroxyl content of 25 mol / t, a terminal carboxyl content of 14 mol / t, and a polydispersity index of 1.98.

[0066] (5) The modified copolyester was subjected to vacuum drum drying at 90°C for 48 hours;

[0067] The modified copolyester after vacuum drum drying has a terminal hydroxyl content of 15 mol / t and a terminal carboxyl content of 8 mol / t.

[0068] (6) The modified copolyester after vacuum drum drying is melt-spun, pre-stretched, cooled and shaped, re-stretched and cut to obtain super smooth and soft polyester staple fiber.

[0069] The spinning temperature was 265℃, the spinning speed was 600m / min, the initial draw ratio was 3, and the redraw ratio was 2; the melt viscosity of the modified copolyester at the spinning temperature was 50Pa·S.

[0070] According to T / CSTM 00522-2022, the coefficient of friction of the super smooth and soft polyester staple fiber is 0.15; the breaking strength of the super smooth and soft polyester staple fiber is 5cN / dtex, the breaking elongation is 150%, the initial modulus is 50cN / dtex, the water contact angle is 102°, and the softness is 100 twists / 200mm.

[0071] Example 2

[0072] A method for preparing ultra-smooth and soft polyester staple fiber, the specific steps of which are as follows:

[0073] (1) Preparation of raw materials:

[0074] Catalyst: Antimony trioxide;

[0075] Heat stabilizer: Triphenyl phosphite;

[0076] Anti-ether agent: anhydrous sodium acetate;

[0077] Terephthalic acid;

[0078] Ethylene glycol;

[0079] Polydimethylsiloxane: Hydroxyl-terminated double-ended polydimethylsiloxane (CAS 70131-67-8), Manufacturer: Sigma-Aldrich, Trademark No.: 481939;

[0080] The third monomer: polytetrahydrofuran with a number average molecular weight of 250 g / mol;

[0081] (2) Preparation of lubricating masterbatch:

[0082] (2.1) Under the conditions of adding catalyst, heat stabilizer and anti-ether agent, terephthalic acid and ethylene glycol were esterified at a molar ratio of 1:1.25 until the water content reached 95.5%; wherein, the amount of catalyst, heat stabilizer and anti-ether agent added was 300 ppm; the esterification temperature was 225℃ and the esterification time was 3.25 h;

[0083] (2.2) After esterification, polydimethylsiloxane was added. First, the vacuum was evacuated for 45 minutes until the absolute vacuum reached 48 Pa. At the same time, the temperature was raised to 269°C during the vacuum process. Then, the power of the stirrer was observed to increase until the power of the stirrer stopped increasing. The reaction ended, and a lubricating masterbatch with a melting point of 190°C was obtained. The amount of polydimethylsiloxane added was 12 wt% based on the lubricating masterbatch.

[0084] (3) Preparation of flexible polyester chips:

[0085] (3.1) Under the conditions of adding catalyst, heat stabilizer and anti-ether agent, terephthalic acid and ethylene glycol were esterified at a molar ratio of 1:1.2 until the water content reached 95%; wherein, the amount of catalyst, heat stabilizer and anti-ether agent added was 300 ppm; the esterification temperature was 225℃ and the esterification time was 3.25 h.

[0086] (3.2) After esterification, the third monomer was added. First, the vacuum was evacuated for 42 minutes until the absolute vacuum reached 48 Pa. At the same time, the temperature was raised to 268℃ during the vacuuming process. Then, the power of the stirrer was observed to start to increase until the power of the stirrer stopped increasing. The reaction ended, and flexible polyester chips with an intrinsic viscosity of 0.82 dl / g and a melting point of 212℃ were obtained. The amount of the third monomer added was 10 wt%, based on the total amount of terephthalic acid, ethylene glycol and the third monomer.

[0087] (4) The lubricating masterbatch from step (2) and the flexible polyester chips from step (3) were melt-blended at 255°C at a mass ratio of 6:100 to obtain a modified copolyester; the modified copolyester had a terminal hydroxyl content of 23 mol / t, a terminal carboxyl content of 13 mol / t, and a polydispersity index of 2.03.

[0088] (5) The modified copolyester was subjected to vacuum drum drying at 95°C for 48 hours;

[0089] The modified copolyester after vacuum drum drying has a terminal hydroxyl content of 14 mol / t and a terminal carboxyl content of 7 mol / t.

[0090] (6) The modified copolyester after vacuum drum drying is melt-spun, pre-stretched, cooled and shaped, re-stretched and cut to obtain super smooth and soft polyester staple fiber.

[0091] The spinning temperature was 266℃, the spinning speed was 650m / min, the initial draw ratio was 3, and the redraw ratio was 2.3; the melt viscosity of the modified copolyester at the spinning temperature was 45Pa·S.

[0092] According to T / CSTM 00522-2022, the coefficient of friction of the super smooth and soft polyester staple fiber is 0.13; the breaking strength of the super smooth and soft polyester staple fiber is 4.6 cN / dtex, the breaking elongation is 200%, the initial modulus is 45 cN / dtex, the water contact angle is 105°, and the softness is 120 twists / 200mm.

[0093] Example 3

[0094] A method for preparing ultra-smooth and soft polyester staple fiber, the specific steps of which are as follows:

[0095] (1) Preparation of raw materials:

[0096] Catalyst: Antimony acetate;

[0097] Heat stabilizer: Alkyl phosphate diester;

[0098] Anti-ether agent: anhydrous sodium acetate;

[0099] Terephthalic acid;

[0100] Ethylene glycol;

[0101] Polydimethylsiloxane: Hydroxyl-terminated double-ended polydimethylsiloxane (CAS 70131-67-8), Manufacturer: Sigma-Aldrich, Trademark No.: 481955;

[0102] The third monomer: polyethylene glycol with a number average molecular weight of 1000 g / mol;

[0103] (2) Preparation of lubricating masterbatch:

[0104] (2.1) Under the conditions of adding catalyst, heat stabilizer and anti-ether agent, terephthalic acid and ethylene glycol were esterified at a molar ratio of 1:1.3 until the water content reached 96%; wherein, the amount of catalyst, heat stabilizer and anti-ether agent added was 300 ppm; the esterification temperature was 220℃ and the esterification time was 3.5 h;

[0105] (2.2) After esterification, polydimethylsiloxane was added. First, the vacuum was evacuated for 50 minutes until the absolute vacuum reached 46 Pa. At the same time, the temperature was raised to 270°C during the vacuum process. Then, the power of the stirrer was observed to increase until the power of the stirrer stopped increasing. The reaction ended, and a lubricating masterbatch with a melting point of 185°C was obtained. The amount of polydimethylsiloxane added was 14 wt% based on the lubricating masterbatch.

[0106] (3) Preparation of flexible polyester chips:

[0107] (3.1) Under the conditions of adding catalyst, heat stabilizer and anti-ether agent, terephthalic acid and ethylene glycol were esterified at a molar ratio of 1:1.25 until the water content reached 96%; wherein, the amount of catalyst, heat stabilizer and anti-ether agent added was 300 ppm; the esterification temperature was 220℃ and the esterification time was 3.5 h;

[0108] (3.2) After esterification, the third monomer was added. First, the vacuum was evacuated for 45 minutes until the absolute vacuum reached 46 Pa. At the same time, the temperature was raised to 269°C during the vacuuming process. Then, the power of the stirrer was observed to increase until the power of the stirrer stopped increasing. The reaction was then completed, and flexible polyester chips with an intrinsic viscosity of 0.8 dl / g and a melting point of 208°C were obtained. The amount of the third monomer added was 15 wt%, based on the total amount of terephthalic acid, ethylene glycol and the third monomer.

[0109] (4) The lubricating masterbatch from step (2) and the flexible polyester chips from step (3) were melt-blended at 260°C at a mass ratio of 7:100 to obtain a modified copolyester; the modified copolyester had a terminal hydroxyl content of 22 mol / t, a terminal carboxyl content of 12 mol / t, and a polydispersity index of 2.1.

[0110] (5) The modified copolyester was subjected to vacuum drum drying at 100°C for 48 hours;

[0111] The modified copolyester after vacuum drum drying has a terminal hydroxyl content of 13.5 mol / t and a terminal carboxyl content of 6.8 mol / t.

[0112] (6) The modified copolyester after vacuum drum drying is melt-spun, pre-stretched, cooled and shaped, re-stretched and cut to obtain super smooth and soft polyester staple fiber.

[0113] The spinning temperature was 267℃, the spinning speed was 700m / min, the initial draw ratio was 3, and the redraw ratio was 2.5; the melt viscosity of the modified copolyester at the spinning temperature was 40Pa·S.

[0114] According to T / CSTM 00522-2022, the coefficient of friction of the super smooth and soft polyester staple fiber is 0.11; the breaking strength of the super smooth and soft polyester staple fiber is 4.3 cN / dtex, the breaking elongation is 250%, the initial modulus is 40 cN / dtex, the water contact angle is 110°, and the softness is 130 twists / 200mm.

[0115] Example 4

[0116] A method for preparing ultra-smooth and soft polyester staple fiber, the specific steps of which are as follows:

[0117] (1) Preparation of raw materials:

[0118] Catalyst: Tetrabutyl titanate;

[0119] Heat stabilizer: trimethyl phosphate and triphenyl phosphite in a 1:1 mass ratio;

[0120] Anti-ether agent: anhydrous sodium acetate;

[0121] Terephthalic acid;

[0122] Ethylene glycol;

[0123] Polydimethylsiloxane: Hydroxyl-terminated double-endopeptide polydimethylsiloxane (CAS156327-07-0), Manufacturer: Achem-block, Trademark No.: ABC-B636184;

[0124] The third monomer: polytetrahydrofuran with a number average molecular weight of 1000 g / mol;

[0125] (2) Preparation of lubricating masterbatch:

[0126] (2.1) Under the conditions of adding catalyst, heat stabilizer and anti-ether agent, terephthalic acid and ethylene glycol were esterified at a molar ratio of 1:1.35 until the water content reached 96.5%; wherein, the amount of catalyst, heat stabilizer and anti-ether agent added was 300 ppm; the esterification temperature was 215℃ and the esterification time was 3.75 h.

[0127] (2.2) After esterification, polydimethylsiloxane was added. First, the vacuum was evacuated for 55 minutes until the absolute vacuum reached 45 Pa. At the same time, the temperature was raised to 271°C during the vacuum process. Then, the power of the stirrer was observed to increase until the power of the stirrer stopped increasing. The reaction ended, and a lubricating masterbatch with a melting point of 182°C was obtained. The amount of polydimethylsiloxane added was 16 wt% based on the lubricating masterbatch.

[0128] (3) Preparation of flexible polyester chips:

[0129] (3.1) Under the conditions of adding catalyst, heat stabilizer and anti-ether agent, terephthalic acid and ethylene glycol were esterified at a molar ratio of 1:1.3 until the water content reached 96%; wherein, the amount of catalyst, heat stabilizer and anti-ether agent added was 300 ppm; the esterification temperature was 215℃ and the esterification time was 3.75 h.

[0130] (3.2) After esterification, the third monomer was added. First, the vacuum was evacuated for 50 minutes until the absolute vacuum reached 45 Pa. At the same time, the temperature was raised to 270°C during the vacuuming process. Then, the power of the stirrer was observed to increase until it stopped increasing. The reaction was then complete, and flexible polyester chips with an intrinsic viscosity of 0.75 dl / g and a melting point of 206°C were obtained. The amount of the third monomer added was 20 wt%, based on the total amount of terephthalic acid, ethylene glycol and the third monomer.

[0131] (4) The lubricating masterbatch from step (2) and the flexible polyester chips from step (3) were melt-blended at 265°C at a mass ratio of 8:100 to obtain a modified copolyester; the modified copolyester had a terminal hydroxyl content of 21 mol / t, a terminal carboxyl content of 11 mol / t, and a polydispersity index of 2.13.

[0132] (5) The modified copolyester was subjected to vacuum drum drying at 105°C for 48 hours;

[0133] The modified copolyester after vacuum drum drying has a terminal hydroxyl content of 13 mol / t and a terminal carboxyl content of 6.5 mol / t.

[0134] (6) The modified copolyester after vacuum drum drying is melt-spun, pre-stretched, cooled and shaped, re-stretched and cut to obtain super smooth and soft polyester staple fiber.

[0135] The spinning temperature was 268℃, the spinning speed was 750m / min, the initial draw ratio was 3, and the redraw ratio was 2.7; the melt viscosity of the modified copolyester at the spinning temperature was 35Pa·S.

[0136] According to T / CSTM 00522-2022, the coefficient of friction of the super smooth and soft polyester staple fiber is 0.08; the breaking strength of the super smooth and soft polyester staple fiber is 4.1 cN / dtex, the breaking elongation is 270%, the initial modulus is 35 cN / dtex, the water contact angle is 115°, and the softness is 140 twists / 200mm.

[0137] Example 5

[0138] A method for preparing ultra-smooth and soft polyester staple fiber, the specific steps of which are as follows:

[0139] (1) Preparation of raw materials:

[0140] Catalyst: Isopropyl titanate;

[0141] Heat stabilizer: triphenyl phosphite and alkyl phosphate diester in a 1:1 mass ratio;

[0142] Anti-ether agent: anhydrous sodium acetate;

[0143] Terephthalic acid;

[0144] Ethylene glycol;

[0145] Polydimethylsiloxane: Hydroxyl-terminated double-endopeptinated polydimethylsiloxane (CAS156327-07-0), Manufacturer: Adamas, Trademark No.: 4054085;

[0146] The third monomer: polyethylene glycol with a number average molecular weight of 2000 g / mol;

[0147] (2) Preparation of lubricating masterbatch:

[0148] (2.1) Under the conditions of adding catalyst, heat stabilizer and anti-ether agent, terephthalic acid and ethylene glycol were esterified at a molar ratio of 1:1.4 until the water content reached 97%; wherein, the amount of catalyst, heat stabilizer and anti-ether agent added was 300 ppm; the esterification temperature was 210℃ and the esterification time was 4 h.

[0149] (2.2) After esterification, polydimethylsiloxane was added. First, the vacuum was evacuated for 58 minutes until the absolute vacuum reached 43 Pa. At the same time, the temperature was raised to 272°C during the vacuum process. Then, the power of the stirrer was observed to increase until the power of the stirrer stopped increasing. The reaction ended, and a lubricating masterbatch with a melting point of 180°C was obtained. The amount of polydimethylsiloxane added was 18 wt% based on the lubricating masterbatch.

[0150] (3) Preparation of flexible polyester chips:

[0151] (3.1) Under the conditions of adding catalyst, heat stabilizer and anti-ether agent, terephthalic acid and ethylene glycol were esterified at a molar ratio of 1:1.35 until the water content reached 97%; the amount of catalyst, heat stabilizer and anti-ether agent added was 300 ppm; the esterification temperature was 210℃ and the esterification time was 3.75 h.

[0152] (3.2) After esterification, the third monomer was added. First, the vacuum was evacuated for 55 minutes until the absolute vacuum reached 43 Pa. At the same time, the temperature was raised to 271°C during the vacuuming process. Then, the power of the stirrer was observed to start to increase until the power of the stirrer stopped increasing. The reaction was then completed, and flexible polyester chips with an intrinsic viscosity of 0.7 dl / g and a melting point of 203°C were obtained. The amount of the third monomer added was 25 wt%, based on the total amount of terephthalic acid, ethylene glycol and the third monomer.

[0153] (4) The lubricating masterbatch from step (2) and the flexible polyester chips from step (3) were melt-blended at 268°C at a mass ratio of 9:100 to obtain a modified copolyester; the modified copolyester had a terminal hydroxyl content of 20.5 mol / t, a terminal carboxyl content of 10.8 mol / t, and a polydispersity index of 2.17.

[0154] (5) The modified copolyester was subjected to vacuum drum drying at 108°C for 48 hours;

[0155] The modified copolyester after vacuum drum drying has a terminal hydroxyl content of 12.7 mol / t and a terminal carboxyl content of 6.2 mol / t.

[0156] (6) The modified copolyester after vacuum drum drying is melt-spun, pre-stretched, cooled and shaped, re-stretched and cut to obtain super smooth and soft polyester staple fiber.

[0157] The spinning temperature was 269℃, the spinning speed was 780m / min, the initial draw ratio was 3, and the redraw ratio was 2.8; the melt viscosity of the modified copolyester at the spinning temperature was 30Pa·S.

[0158] According to T / CSTM 00522-2022, the coefficient of friction of the super smooth and soft polyester staple fiber is 0.06; the breaking strength of the super smooth and soft polyester staple fiber is 3.8 cN / dtex, the breaking elongation is 290%, the initial modulus is 30 cN / dtex, the water contact angle is 120°, and the softness is 150 twists / 200mm.

[0159] Example 6

[0160] A method for preparing ultra-smooth and soft polyester staple fiber, the specific steps of which are as follows:

[0161] (1) Preparation of raw materials:

[0162] Catalyst: Tetrabutyl titanate and isopropyl titanate in a mass ratio of 1:1;

[0163] Heat stabilizer: trimethyl phosphate and alkyl phosphate diester in a 1:1 mass ratio;

[0164] Anti-ether agent: anhydrous sodium acetate;

[0165] Terephthalic acid;

[0166] Ethylene glycol;

[0167] Polydimethylsiloxane: Hydroxyl-terminated double-ended polydimethylsiloxane (CAS 70131-67-8), Manufacturer: Alfa, Trademark No.: 043769;

[0168] The third monomer: polytetrahydrofuran with a number average molecular weight of 2000 g / mol;

[0169] (2) Preparation of lubricating masterbatch:

[0170] (2.1) Under the conditions of adding catalyst, heat stabilizer and anti-ether agent, terephthalic acid and ethylene glycol were esterified at a molar ratio of 1:1.4 until the water content reached 98%; wherein, the amount of catalyst, heat stabilizer and anti-ether agent added was 300 ppm; the esterification temperature was 200℃ and the esterification time was 4 h.

[0171] (2.2) After esterification, polydimethylsiloxane was added. First, the vacuum was evacuated for 60 minutes until the absolute vacuum reached 40 Pa. At the same time, the temperature was raised to 272°C during the vacuum process. Then, the power of the stirrer was observed to increase until the power of the stirrer stopped increasing. The reaction ended, and a lubricating masterbatch with a melting point of 181°C was obtained. The amount of polydimethylsiloxane added was 20 wt% based on the lubricating masterbatch.

[0172] (3) Preparation of flexible polyester chips:

[0173] (3.1) Under the conditions of adding catalyst, heat stabilizer and anti-ether agent, terephthalic acid and ethylene glycol were esterified at a molar ratio of 1:1.4 until the water yield reached 97%; wherein, the amount of catalyst, heat stabilizer and anti-ether agent added was 300 ppm; the esterification temperature was 200℃ and the esterification time was 4h.

[0174] (3.2) After esterification, the third monomer was added. First, the vacuum was evacuated for 60 minutes until the absolute vacuum reached 40 Pa. At the same time, the temperature was raised to 272°C during the vacuuming process. Then, the power of the stirrer was observed to increase until it stopped increasing. The reaction was then complete, and flexible polyester chips with an intrinsic viscosity of 0.65 dl / g and a melting point of 200°C were obtained. The amount of the third monomer added was 30 wt%, based on the total amount of terephthalic acid, ethylene glycol and the third monomer.

[0175] (4) The lubricating masterbatch from step (2) and the flexible polyester chips from step (3) were melt-blended at 270°C at a mass ratio of 10:100 to obtain a modified copolyester; the modified copolyester had a terminal hydroxyl content of 20 mol / t, a terminal carboxyl content of 10 mol / t, and a polydispersity index of 2.19.

[0176] (5) The modified copolyester was subjected to vacuum drum drying at 110°C for 48 hours;

[0177] The modified copolyester after vacuum drum drying has a terminal hydroxyl content of 12 mol / t and a terminal carboxyl content of 5.5 mol / t.

[0178] (6) The modified copolyester after vacuum drum drying is melt-spun, pre-stretched, cooled and shaped, re-stretched and cut to obtain super smooth and soft polyester staple fiber.

[0179] The spinning temperature was 270℃, the spinning speed was 800m / min, the initial draw ratio was 3, and the redraw ratio was 3; the melt viscosity of the modified copolyester at the spinning temperature was 25Pa·S.

[0180] According to T / CSTM 00522-2022, the coefficient of friction of the super smooth and soft polyester staple fiber is 0.05; the breaking strength of the super smooth and soft polyester staple fiber is 3.5 cN / dtex, the breaking elongation is 300%, the initial modulus is 25 cN / dtex, the water contact angle is 123°, and the softness is 160 twists / 200mm.

Claims

1. A method for preparing ultra-smooth and soft polyester staple fiber, characterized in that: Modified copolyester is melt-spun and post-processed to produce ultra-smooth and soft polyester staple fibers; The modified copolyester was prepared by melt blending lubricating masterbatch and flexible polyester chips; The lubricating masterbatch is prepared by copolymerization of terephthalic acid, ethylene glycol, and polydimethylsiloxane; the flexible polyester chips are prepared by copolymerization of terephthalic acid, ethylene glycol, and a third monomer; the polydimethylsiloxane has a terminal structure of either hydroxyl-terminated double-ended or hydroxyl-alkyl-terminated double-ended; the number average molecular weight of polydimethylsiloxane is 500~3000 g / mol, and the dynamic viscosity is 20~75 mPa·s; the third monomer is polyethylene glycol with a number average molecular weight of 400~2000 g / mol or polytetrahydrofuran with a number average molecular weight of 250~2000 g / mol. According to T / CSTM 00522-2022, the coefficient of friction of the super smooth and soft polyester staple fiber is 0.05~0.15; the tensile strength of the super smooth and soft polyester staple fiber is 3.5~5 cN / dtex, the initial modulus is ≤50cN / dtex, the elongation at break is 150~300%, the water contact angle is ≥100°, the melt viscosity of the modified copolyester at the spinning temperature is 10~50 Pa·s, and the softness is ≥100 twists / 200mm.

2. The method for preparing an ultra-smooth and soft polyester staple fiber according to claim 1, characterized in that, The melting point of the lubricating masterbatch is 180~200℃; based on the lubricating masterbatch, the amount of polydimethylsiloxane added is 10~20wt%; The intrinsic viscosity of flexible polyester chips is 0.65~0.85 dl / g, and the melting point is 200~220℃.

3. The method for preparing an ultra-smooth and soft polyester staple fiber according to claim 1, characterized in that, The preparation steps for lubricating masterbatch are as follows: (1) Under the conditions of adding catalyst, heat stabilizer and anti-ether agent, terephthalic acid and ethylene glycol are esterified at a molar ratio of 1:1.2~1.4 until the water content reaches more than 95%; the amount of catalyst, heat stabilizer and anti-ether agent added is 300 ppm; the esterification temperature is 200~230℃ and the esterification time is 3~4h; (2) After esterification, polydimethylsiloxane is added. First, vacuum is applied for 40-60 minutes until the absolute vacuum reaches below 50 Pa. At the same time, the temperature is raised to 268-272℃ during the vacuum process. Then, the power of the stirrer is observed to increase until the power of the stirrer no longer increases. The reaction ends and the lubricating masterbatch is obtained.

4. The method for preparing an ultra-smooth and soft polyester staple fiber according to claim 1, characterized in that, The preparation steps for flexible polyester chips are as follows: (1) Under the conditions of adding catalyst, heat stabilizer and anti-ether agent, terephthalic acid and ethylene glycol are esterified at a molar ratio of 1:1.2~1.4 until the water content reaches more than 95%; the amount of catalyst, heat stabilizer and anti-ether agent added is 300 ppm; the esterification temperature is 200~230℃ and the esterification time is 3~4h; (2) After esterification, the third monomer is added. First, vacuum is applied for 40-60 minutes until the absolute vacuum reaches below 50 Pa. At the same time, the temperature is raised to 268-272℃ during the vacuum process. Then, the power of the stirrer is observed to increase until the power of the stirrer no longer increases. The reaction ends and flexible polyester chips are obtained. The amount of the third monomer added is 5-30 wt, based on the total amount of terephthalic acid, ethylene glycol and the third monomer.

5. A method for preparing an ultra-smooth and soft polyester staple fiber according to claim 3 or 4, characterized in that, The catalyst is one or two of antimony glycolate, antimony trioxide, antimony acetate, tetrabutyl titanate, and isopropyl titanate; the heat stabilizer is one or two of trimethyl phosphate, triphenyl phosphite, and alkyl phosphate diester; and the ether inhibitor is anhydrous sodium acetate.

6. The method for preparing an ultra-smooth and soft polyester staple fiber according to claim 1, characterized in that, The mass ratio of lubricating masterbatch to flexible polyester chips is 5~10:100, and the melt blending temperature is 250~270℃.

7. The method for preparing an ultra-smooth and soft polyester staple fiber according to claim 1, characterized in that, Before melt spinning, the modified copolyester is first subjected to vacuum drum drying treatment at a temperature of 90~110℃ for 48 hours. Before vacuum drum drying, the modified copolyester has a terminal hydroxyl content of 20-30 mol / t, a terminal carboxyl content of 10-15 mol / t, and a polydispersity index ≤2.

2. After vacuum drum drying, the terminal hydroxyl content is 10-20 mol / t, and the terminal carboxyl content is 5-10 mol / t.

8. The method for preparing an ultra-smooth and soft polyester staple fiber according to claim 1, characterized in that, The spinning temperature is 265~270℃ and the spinning speed is 600~800 m / min.