Split core type foamed polyester fiber and method for manufacturing the same

Abstract

The present application relates to the field of polyester, and discloses a kind of skin-core type foamed polyester fiber and its preparation method.The skin-core type foamed polyester fiber includes foamed polyester core layer and polyester skin layer;Foamed polyester core layer is obtained by melt spinning after modified foamed polyester is blended with nucleating agent and foaming agent;Modified foamed polyester is obtained by esterification, polycondensation with terephthalic acid, isophthalic acid, ethylene glycol and pentaerythritol as monomers.The present application reduces the melting point of foamed polyester by modification, and at the same time enhances its melt strength, and the polyester fiber is designed as skin-core structure, and the skin-core type foamed polyester fiber with good complete continuity and excellent mechanical strength can be successfully prepared.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of polyester, in particular to a skin-core type foamed polyester fiber and a preparation method thereof. BACKGROUND

[0002] Foamed material is a kind of light material with a large number of small bubble structure, the bubble can be closed or connected, uniform or non-uniform, and can also be single or composite. It is usually made of high molecular materials such as plastics and rubbers, and the porous structure is formed by physical or chemical foaming process, and the density is generally 0.01-0.6 g / cm 3 , much lower than that of ordinary high molecular materials, so as to give the material the characteristics of light weight, sound absorption, heat insulation, buffering and shock absorption, etc.

[0003] Among them, the polyethylene terephthalate foamed material gradually attracts the attention of the demand side due to its excellent heat resistance, mechanical strength and other advantages, and has wide application prospects in fields such as building construction, automobile inner plate, roof insulation, microwave container, sports equipment, automobile and aerospace industry, etc.

[0004] At present, foamed polyester is usually processed into board, film and other products, and rarely added into fiber form. The reason is that the high crystallinity and low melt strength of polyethylene terephthalate itself easily leads to the difficulty of forming closed bubbles for gas in its system, and the cell size is large (the cell size formed by conventional foaming agent is in the order of hundreds of microns), which is difficult to ensure the continuous forming of fiber, and even if the forming is formed, the foamed polyester fiber strength is too low to meet the use requirement. Therefore, the preparation of foamed polyester fiber not only needs to overcome the foaming difficulty of PET itself, but also needs to consider the complex relationship between the cell structure characteristics and the fiber diameter, mechanical properties, and the sequence of foaming process and spinning process, and the related process technology is not mature at present.

[0005] Patent CN109852009A discloses a kind of high thermoplastic foamed polyester, by adding acicular structure nucleating agent to improve the crystallization performance of thermoplastic polyester, speed up the crystallization rate, improve its mechanical properties, effectively improve the stability of foaming process technology;The addition of chain extender and antioxidant further improves the thermal stability and melt strength of polyester at high temperature, and finally a thermoplastic polyester foamed material is prepared by physical foaming. However, in this scheme, the diameter of acicular nucleating agent is 0.1-100 μm, and the aspect ratio is 3-100, which is too large for the spinning filter assembly, so it is not suitable for the production of foamed fiber.

[0006] Patent CN1760418A discloses a kind of porous PET foam fiber and its preparation method, by putting conventional or special-shaped PET fiber into high-pressure container, inert gas is filled, and gas penetration, pressure release and heat treatment are carried out to obtain foamed fiber.The method uses gas foaming, the high pressure condition involved requires higher equipment, and it is difficult to carry out large-scale production. SUMMARY

[0007] In order to solve the above technical problems, the present application provides a kind of skin-core type foamed polyester fiber and its preparation method.The present application reduces the melting point of foamed polyester by modification and at the same time enhances its melt strength, and designs the polyester fiber as skin-core structure, which can successfully produce skin-core type foamed polyester fiber with good complete continuity and excellent mechanical strength.

[0008] The specific technical scheme of the present application is:

[0009] In the first aspect, the present application provides a kind of skin-core type foamed polyester fiber, which includes foamed polyester core layer and polyester skin layer.The foamed polyester core layer is obtained by melt spinning after blending modified foamed polyester with nucleating agent and foaming agent;The modified foamed polyester is obtained by esterification and polycondensation using terephthalic acid, isophthalic acid, ethylene glycol and pentaerythritol as monomers.

[0010] In view of the technical problems that the melt strength of conventional polyester is insufficient, which can easily lead to bubble collapse in the foaming process, it is difficult to find a suitable chemical foaming agent due to the high spinning temperature of conventional polyester, and the bubble size formed by conventional foaming agent is large, which is difficult to ensure the continuous formation of the fiber, the present application provides the following improvement measures:

[0011] Firstly, the present application develops a special modified foamed polyester, which is obtained by esterification and polycondensation using terephthalic acid, isophthalic acid, ethylene glycol and pentaerythritol as monomers;The appropriate isophthalic acid can destroy the spatial regularity of polyester macromolecules, so that the melting point is reduced, and at the same time, the foaming temperature can also be reduced;The introduction of appropriate pentaerythritol into the polyester molecular chain can make the polyester have partial branched structure, enhance the melt strength, and at the same time, it can also improve the strength and modulus of the fiber.Therefore, the modified foamed polyester of the present application has the characteristics of low melting point and high melt strength, which can maintain the bubble structure in the foaming process.

[0012] Secondly, the present application ingeniously designs the polyester fiber as skin-core structure, the core layer uses foamed polyester, and the skin layer uses ordinary polyester;Such design can ensure that the core layer is wrapped by the skin layer polyester when foaming, so as to ensure the continuous formation of the fiber in the spinning process.Finally, the core layer of the obtained foamed polyester fiber presents a porous structure, and the skin layer acts as the outer wall of the core layer bubble structure, which can guarantee the complete continuity of the fiber structure and provide certain mechanical strength for the fiber.

[0013] Finally, the present application adds a nucleating agent while adding a foaming agent in the foamed polyester core layer, the nucleating agent can increase the bubble nucleation site, promote bubble nucleation and stability, and benefit the formation of uniform and dense cell structure.

[0014] As preferred, the mass ratio of the foamed polyester core layer and the polyester skin layer is 4:6-7:3.

[0015] If the skin layer is too thick, the proportion of the foamed core layer is too small, and the lightweight, warmth and other advantages of the fiber are not obvious enough; if the skin layer is too thin, the proportion of the foamed core layer is too large, and the strength of the fiber decreases too much, which is not conducive to the subsequent weaving and other processing processes.

[0016] As preferred, the foaming agent is selected from one or more of 4,4'-oxybis(benzene sulfonyl urea), trihydrazine and N-nitroguanidine.

[0017] The reason for selecting the above-mentioned foaming agent in the present application is that: first, the decomposition temperature of the above-mentioned foaming agent is about 240-250℃, the higher decomposition temperature is more matched with the melt spinning temperature of the modified foamed polyester, and the foamed structure can be obtained in situ during the fiber forming process; secondly, the present application finds that compared with other conventional foaming agents, the above-mentioned several types of foaming agents are especially suitable for the preparation of the foamed polyester fiber of the present application, and the final bubble size generated after high-temperature foaming is small, which will not significantly affect the strength of the fiber.

[0018] Further preferably, the foaming agent accounts for 0.5-2wt% of the total raw materials of the foamed polyester core layer.

[0019] As preferred, the nucleating agent is selected from one or more of nano-silicon dioxide, nano-titanium dioxide, nano-diatomite and nano-kaolin.

[0020] The reason for selecting the above-mentioned foaming agent in the present application is that: first, the present application finds that the use of the above-mentioned several types of nano-sized inorganic nucleating agents can make the bubble size generated by high-temperature foaming of the foaming agent smaller, which will not significantly affect the strength of the fiber; secondly, the above-mentioned nano-sized inorganic nucleating agent itself can improve the mechanical strength of the fiber to a certain extent as a reinforcing material.

[0021] Further preferably, the nucleating agent accounts for 0.5-2wt% of the total raw materials of the foamed polyester core layer.

[0022] As preferred, an antioxidant is also added in the formation process of the foamed polyester core layer.

[0023] The purpose of adding the antioxidant in the present application is to weaken the oxidative degradation of the polymer under the action of screw heating and shearing and the viscosity reduction caused thereby.

[0024] Further preferably, the antioxidant is selected from one or more of antioxidant 1024, antioxidant 264, antioxidant 1010 and antioxidant 1076.

[0025] Further preferably, the antioxidant accounts for 0.5-2wt% of the total raw material of the foamed polyester core layer.

[0026] As preferred, the alcohol acid molar ratio in the preparation process of the modified foamed polyester is 1.2-1.4:1.

[0027] As preferred, the isophthalic acid accounts for 10-20mol% of the total of terephthalic acid and isophthalic acid.

[0028] If the content of isophthalic acid is too low, the melting point of the modified polyester does not decrease significantly, and it cannot match the foaming temperature of the foaming agent; if the content of isophthalic acid is too high, the melting point and crystallinity of the modified polyester decrease significantly, resulting in the decrease of thermal stability and fiber strength.

[0029] As preferred, the pentaerythritol accounts for 0.02-0.2mol% of the total of ethylene glycol and pentaerythritol.

[0030] If the content of pentaerythritol is too low, the branched structure produced is insufficient, and the melt strength of the modified polyester is insufficient to support the pore structure; if the content of pentaerythritol is too high, too many branched structures are produced, and even crosslinking occurs, which is not conducive to subsequent spinning processing.

[0031] In a second aspect, the present application provides a preparation method of a sheath-core foamed polyester fiber, which comprises:

[0032] 1) using terephthalic acid, isophthalic acid, ethylene glycol and pentaerythritol as monomers, esterification and polycondensation to obtain a modified foamed polyester.

[0033] 2) using the modified foamed polyester, a foaming agent and a nucleating agent as core layer raw materials, and a polyester as a sheath layer raw material, in a melt spinning process, on the one hand, the melt is formed into a fiber, and on the other hand, the foaming agent is foamed at high temperature to produce pores, and finally a sheath-core foamed polyester fiber is formed.

[0034] As preferred, in step 1), the esterification is first esterification at 205-225℃ under normal pressure for 30-50min, and then pressurized esterification at 225-255℃ and 0.2-0.4MPa for 90-180min under inert atmosphere; the polycondensation is polycondensation under vacuum condition at 265-285℃ under negative pressure for 0.5-2h.

[0035] As preferred, in step 2), a double-screw extruder is used for melt blending; wherein the processing temperature of the double-screw mixing section is 210-230℃, and the double-screw rotation speed is 100-300r / min.

[0036] As preferred, in step 2), the skin layer spinning box temperature is 285-295℃, the core layer spinning box temperature is 235-245℃, and the winding speed is 2500-3000m / min.

[0037] Compared with the prior art, the present application has the following advantages:

[0038] (1) The present application develops a special modified foamed polyester, which is obtained by esterification and polycondensation with terephthalic acid, isophthalic acid, ethylene glycol and pentaerythritol as monomers; the appropriate isophthalic acid can destroy the spatial regularity of polyester macromolecules, so as to reduce the melting point, and also can reduce the foaming temperature; and the introduction of appropriate pentaerythritol into the polyester molecular chain can make the polyester have a partial branched structure, so as to enhance the melt strength, and also can improve the strength and modulus of the fiber. Therefore, the modified foamed polyester of the present application has the characteristics of low melting point and high melt strength, and can maintain the bubble structure in the foaming process.

[0039] (2) The polyester fiber is designed as a sheath-core structure in the present application, the core layer raw material is foamed polyester, and the sheath layer raw material is ordinary polyester; such design can ensure that the core layer is wrapped by the sheath layer polyester when foaming, so as to ensure the continuous forming of the fiber in the spinning process. Finally, the core layer of the obtained foamed polyester fiber presents a porous structure, and the sheath layer acts as the outer wall of the core layer bubble structure, which can guarantee the complete continuity of the fiber structure and provide certain mechanical strength for the fiber.

[0040] (3) The nucleating agent is added in the foamed polyester core layer in the present application, the nucleating agent can increase the bubble nucleation site, promote the bubble nucleation and stability, and is beneficial to the formation of uniform and dense bubble structure. Further, the present application finds that certain types of nano-sized inorganic nucleating agents not only make the bubble size generated by the foaming agent at high temperature smaller, which does not significantly affect the strength of the fiber; but also can improve the mechanical strength of the fiber to a certain extent as reinforcing materials.

[0041] (4) The present application finds a foaming agent which is particularly suitable for the modified foamed polyester of the present application. On the one hand, its decomposition temperature is more matched with the melt spinning temperature of the modified foamed polyester, so that the foaming structure can be obtained in situ during the fiber forming process; on the other hand, the bubble size generated by these foaming agents after high-temperature foaming is smaller, which does not significantly affect the strength of the fiber.

[0042] (5) The foaming agent is added to the polymer melt in the melt spinning process in the present application, which can avoid the decomposition of the foaming agent caused by early contact with high temperature, compared with the method of pre-melt mixing with the foaming modified polyester; and compared with the method of pre-physical mixing with the foaming modified polyester, the mixing of the powder and the polyester chip can be avoided to cause uneven foaming. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 Cross-section electron microscope image of the foamed polyester fiber core layer of the best embodiment.

[0044] Figure 2 Cross-section electron microscope image of the foamed polyester fiber core layer of Comparative Example 1. DETAILED DESCRIPTION

[0045] The application will be further described in conjunction with the examples below.

[0046] General Examples

[0047] A skin-core type foamed polyester fiber comprises a foamed polyester core layer and a polyester skin layer. The foamed polyester core layer is obtained by melt spinning after blending of modified foamed polyester, nucleating agent and foaming agent; the modified foamed polyester is obtained by esterification and polycondensation with terephthalic acid, isophthalic acid, ethylene glycol and pentaerythritol as monomers.

[0048] In some preferred embodiments, the mass ratio of the foamed polyester core layer and the polyester skin layer is 4:6-7:3.

[0049] In some preferred embodiments, the foaming agent is selected from one or more of 4,4'-oxybis(benzenesulfonylurea), trihydrazinyl-s-triazine and N-nitroguanidine. Further preferably, the foaming agent accounts for 0.5-2wt% of the total raw materials of the foamed polyester core layer.

[0050] In some preferred embodiments, the nucleating agent is selected from one or more of nano-silicon dioxide, nano-titanium dioxide, nano-diatomite and nano-kaolin. Further preferably, the nucleating agent accounts for 0.5-2wt% of the total raw materials of the foamed polyester core layer.

[0051] In some preferred embodiments, an antioxidant is further added in the formation process of the foamed polyester core layer. Further preferably, the antioxidant is selected from one or more of antioxidant 1024, antioxidant 264, antioxidant 1010 and antioxidant 1076. Further preferably, the antioxidant accounts for 0.5-2wt% of the total raw materials of the foamed polyester core layer.

[0052] In some preferred embodiments, the alcohol acid molar ratio in the preparation process of the modified foamed polyester is 1.2-1.4:1.

[0053] In some preferred embodiments, the isophthalic acid accounts for 10-20mol% of the total of terephthalic acid and isophthalic acid; the pentaerythritol accounts for 0.02-0.2mol% of the total of ethylene glycol and pentaerythritol.

[0054] A preparation method of a skin-core type foamed polyester fiber, comprising:

[0055] 1) esterification and polycondensation of terephthalic acid, isophthalic acid, ethylene glycol and pentaerythritol as monomers to obtain modified foaming polyester.

[0056] In some preferred embodiments, in step 1), the esterification is first esterification at 205-225℃ under normal pressure for 30-50min, and then pressurized esterification at 225-255℃, 0.2-0.4MPa for 90-180min; the polycondensation is polycondensation under vacuum condition at 265-285℃ under negative pressure for 0.5-2h.

[0057] 2) melt spinning forming with modified foaming polyester, foaming agent and nucleating agent as core layer raw materials, and polyester as skin layer raw materials to prepare skin-core foaming polyester fiber.

[0058] In some preferred embodiments, in step 2), melt blending is carried out by using a double screw extruder; the processing temperature of the double screw mixing section is 210-230℃, and the double screw rotation speed is 100-300r / min.

[0059] In some preferred embodiments, in step 2), during the melt spinning forming process, the skin layer spinning box temperature is 285-295℃, the core layer spinning box temperature is 235-245℃, and the winding speed is 2500-3000m / min.

[0060] Specific embodiments and comparative examples

[0061] Best embodiment

[0062] (1) 85mol% terephthalic acid and 15mol% isophthalic acid, 99.85mol% ethylene glycol and 0.15mol% pentaerythritol as polymerization monomers, esterification and polycondensation reaction to obtain low melting point, high melt strength modified foaming polyester, alcohol acid molar ratio is 1.3:1. The specific steps are as follows:

[0063] In a polyester polymerization reactor, 319.18 g (5.148 mol) of terephthalic acid, 7.08 g (0.052 mol) of isophthalic acid, 245.52 g (3.40 mol) of ethylene glycol, 5.45 g (0.60 mol) of pentaerythritol, 0.35 g (400 ppm based on the total mass of 4 mol of PET) of ethylene glycol antimony, and 0.18 g (200 ppm based on the total mass of 4 mol of PET) of sodium acetate were added. After nitrogen replacement for three times, esterification was first carried out at 215°C under normal pressure for 0.5 h, and then at 245°C under 0.30 MPa for 2 h, and the esterification water was separated and condensed by an esterification tower. Then the polycondensation temperature was adjusted to 278°C, and the low vacuum pre-polycondensation and high vacuum polycondensation were carried out for 1.5 h, so that the stirring power reached the expected value, and finally the melt was discharged at the bottom of the reactor, and was cooled under water and cut into particles to obtain a low-melting-point and high-melt-strength modified foaming polyester chip. The product index of the polyester is shown in Table 1.

[0064] (2) The low-melting-point and high-melt-strength modified foaming polyester, nucleating agent nano-silicon dioxide, and antioxidant 1024 were added into a double-screw extruder in a mass ratio of 98:1.0:1.0, and were blended and granulated under the processing conditions of a processing temperature of 225°C and a double-screw rotation speed of 200 r / min to obtain a foaming special modified polyester.

[0065] (3) Through a skin-core composite spinning design, the screw of the skin layer was added with conventional polyester (polyethylene terephthalate), and the screw of the core layer was added with the foaming special modified polyester and a chemical foaming agent (4,4'-oxobis(benzene sulfonyl urea amide urea)), wherein the chemical foaming agent was continuously and accurately added by a weight loss balance. The mass ratio of the foaming special modified polyester and the chemical foaming agent was 98.5:1.5. During the spinning forming process, the skin layer spinning box temperature was 285°C, the core layer spinning box temperature was 240°C, and the winding speed was 2800 m / min, and a skin-core type foaming polyester fiber was obtained in situ. The product index of the fiber is shown in Table 1. Figure 1 The cross-sectional electron microscope image of the foaming polyester fiber of the best embodiment.

[0066] Example 1

[0067] (1) 90 mol% of terephthalic acid and 10 mol% of isophthalic acid, 99.85 mol% of ethylene glycol, and 0.15 mol% of pentaerythritol were used as polymerization monomers, and a low-melting-point and high-melt-strength modified foaming polyester was obtained through esterification and polycondensation reaction, and the molar ratio of alcohol to acid was 1.3:1. The specific steps were as follows:

[0068] In a polyester polymerization reactor, 319.18 g (5.148 mol) of terephthalic acid, 7.08 g (0.052 mol) of isophthalic acid, 245.52 g (3.40 mol) of ethylene glycol, 5.45 g (0.60 mol) of pentaerythritol, 0.35 g (400 ppm, based on the total mass of 4 mol of PET) of ethylene glycol antimony, and 0.18 g (200 ppm, based on the total mass of 4 mol of PET) of sodium acetate were added. After nitrogen replacement for three times, esterification was first carried out at 215°C under normal pressure for 0.5 h, and then esterification was carried out at 245°C under 0.32 MPa for 2 h, and the esterification water was separated and condensed by an esterification tower. Then the polycondensation temperature was adjusted to 275°C, and low vacuum pre-polycondensation and high vacuum polycondensation were carried out for 1.5 h, so that the stirring power reached the expected value, and finally the melt was discharged at the bottom of the reactor, and was cooled under water and cut into particles to obtain a low-melting-point and high-melt-strength modified foaming polyester chip. The product index of the polyester is shown in Table 1.

[0069] (2) The low-melting-point and high-melt-strength modified foaming polyester, the nucleating agent nano-silicon dioxide, and the antioxidant 1024 were added into a double-screw extruder in a mass ratio of 98:1.0:1.0, and were blended and granulated under the processing conditions of a processing temperature of 225°C and a double-screw rotation speed of 200 r / min to obtain a foaming special modified polyester.

[0070] (3) Through a skin-core composite spinning design, the screw of the skin layer was added with conventional polyester (polyethylene terephthalate), and the screw of the core layer was added with the foaming special modified polyester and the chemical foaming agent (4,4'-oxobis(benzene sulfonyl urea amide urea)), wherein the chemical foaming agent was continuously and accurately added by a loss weight scale. The mass ratio of the foaming special modified polyester and the chemical foaming agent was 98.5:1.5. During the spinning forming process, the skin layer spinning box temperature was 285°C, the core layer spinning box temperature was 248°C, and the winding speed was 2800 m / min, and a skin-core type foaming polyester fiber was obtained in situ. The product index of the fiber is shown in Table 1.

[0071] Example 2

[0072] (1) 80 mol% of terephthalic acid and 20 mol% of isophthalic acid, 99.85 mol% of ethylene glycol, and 0.15 mol% of pentaerythritol were used as polymerization monomers to obtain a low-melting-point and high-melt-strength modified foaming polyester through esterification and polycondensation reaction, and the molar ratio of alcohol to acid was 1.3:1. The specific steps are as follows:

[0073] In a polyester polymerization reactor, 319.18 g (5.148 mol) of terephthalic acid, 7.08 g (0.052 mol) of isophthalic acid, 245.52 g (3.40 mol) of ethylene glycol, 5.45 g (0.60 mol) of pentaerythritol, 0.35 g (400 ppm, based on 4 mol of PET as the total mass) of ethylene glycol antimony, and 0.18 g (200 ppm, based on 4 mol of PET as the total mass) of sodium acetate were added. After nitrogen replacement for three times, esterification was first carried out at 210°C for 0.5 h under normal pressure, and then esterification was carried out at 250°C and 0.28 MPa for 2 h, and the esterification water was separated and condensed and discharged. Then the polycondensation temperature was adjusted to 280°C, and the stirring power reached the expected value after low-vacuum pre-polycondensation and high-vacuum polycondensation for 1.5 h, and finally the melt was discharged at the bottom of the reactor, and the particles were obtained by underwater cooling. The low-melting-point and high-melt-strength modified foaming polyester chip was prepared. The polyester product indexes are shown in Table 1.

[0074] (2) The low-melting-point and high-melt-strength modified foaming polyester, the nucleating agent nano-titanium dioxide, and the antioxidant 1024 were added into a double-screw extruder in a mass ratio of 98:1.0:1.0, and the special modified polyester for foaming was obtained by blending and granulating under the processing conditions of a processing temperature of 225°C and a double-screw rotation speed of 300 r / min.

[0075] (3) The components of the skin layer were added into the conventional polyester (polyethylene terephthalate) through the screw of the skin-core composite spinning design, and the components of the core layer were added into the special modified polyester for foaming and the chemical foaming agent (trihydrazine s-triazine) through the screw. The chemical foaming agent was continuously and accurately added through the loss weight scale. The mass ratio of the special modified polyester for foaming and the chemical foaming agent was 98.5:1.5. During the spinning forming process, the skin layer spinning box temperature was 285°C, the core layer spinning box temperature was 235°C, and the winding speed was 2700 m / min. The skin-core type foaming polyester fiber was obtained in situ. The fiber product indexes are shown in Table 1.

[0076] Example 3

[0077] (1) 85 mol% of terephthalic acid and 15 mol% of isophthalic acid, 99.80 mol% of ethylene glycol, and 0.20 mol% of pentaerythritol were used as polymerization monomers to obtain a low-melting-point and high-melt-strength modified foaming polyester through esterification and polycondensation reaction. The molar ratio of alcohol to acid was 1.3:1. The specific steps were as follows:

[0078] In a polyester polymerization reactor, 319.18 g (5.148 mol) of terephthalic acid, 7.08 g (0.052 mol) of isophthalic acid, 245.52 g (3.40 mol) of ethylene glycol, 5.45 g (0.60 mol) of pentaerythritol, 0.35 g (400 ppm, based on the total mass of 4 mol of PET) of ethylene glycol antimony, and 0.18 g (200 ppm, based on the total mass of 4 mol of PET) of sodium acetate were added. After nitrogen replacement for three times, esterification was first carried out at 215°C under normal pressure for 0.5 h, and then esterification was carried out at 248°C under 0.28 MPa for 1.8 h, and the esterification water was separated and condensed by an esterification tower. Then the polycondensation temperature was adjusted to 280°C, and the stirring power reached the expected value after low-vacuum pre-polycondensation and high-vacuum polycondensation for 1.5 h, and finally the melt was discharged at the bottom of the reactor, and the particles were obtained by underwater cooling. The low-melting-point and high-melt-strength modified foaming polyester chips were obtained. The product index of the polyester is shown in Table 1.

[0079] (2) The low-melting-point and high-melt-strength modified foaming polyester, the nucleating agent nano-titanium dioxide, and the antioxidant 264 were added into a double-screw extruder in a mass ratio of 98:1.0:1.0, and the special modified polyester for foaming was obtained by blending and granulating under the processing conditions of a processing temperature of 230°C and a double-screw rotation speed of 200 r / min.

[0080] (3) The special modified polyester for foaming and the chemical foaming agent (4,4'-oxobis(benzenesulfonylaminourea)) were added into the screw of the core layer, and the conventional polyester (polyethylene terephthalate) was added into the screw of the skin layer by the design of skin-core composite spinning. The chemical foaming agent was continuously and accurately added by a loss weight scale. The mass ratio of the special modified polyester for foaming and the chemical foaming agent was 98.5:1.5. During the spinning forming process, the skin layer spinning box temperature was 285°C, the core layer spinning box temperature was 243°C, and the winding speed was 2800 m / min. The skin-core type foaming polyester fiber was obtained in situ. The product index of the fiber is shown in Table 1.

[0081] Example 4

[0082] (1) 85 mol% of terephthalic acid and 15 mol% of isophthalic acid, 99.98 mol% of ethylene glycol, and 0.02 mol% of pentaerythritol were used as polymerization monomers to obtain a low-melting-point and high-melt-strength modified foaming polyester by esterification and polycondensation reaction. The molar ratio of alcohol to acid was 1.3:1. The specific steps were as follows:

[0083] In a polyester polymerization reactor, 319.18 g (5.148 mol) of terephthalic acid, 7.08 g (0.052 mol) of isophthalic acid, 245.52 g (3.40 mol) of ethylene glycol, 5.45 g (0.60 mol) of pentaerythritol, 0.35 g (400 ppm, based on 4 mol of PET as the total mass) of ethylene glycol antimony, and 0.18 g (200 ppm, based on 4 mol of PET as the total mass) of sodium acetate were added. After nitrogen replacement for three times, esterification was first carried out at 215°C for 0.5 h under normal pressure, and then esterification was carried out at 243°C and 0.34 MPa for 2.2 h, and the esterification water was separated and condensed and discharged. Then the polycondensation temperature was adjusted to 279°C, and the stirring power reached the expected value after low-vacuum pre-polycondensation and high-vacuum polycondensation for 1.5 h, and finally the melt was discharged at the bottom of the reactor, and the particles were obtained by underwater cooling. The low-melting-point, high-melt-strength modified foaming polyester chip was prepared. The polyester product indexes are shown in Table 1.

[0084] (2) The low-melting-point, high-melt-strength modified foaming polyester, nucleating agent nano-silicon dioxide, and antioxidant 1024 were added into a double-screw extruder in a mass ratio of 98:1.0:1.0, and the special modified polyester for foaming was obtained by blending and granulating under the processing conditions of a processing temperature of 225°C and a double-screw rotation speed of 200 r / min.

[0085] (3) The components of the skin layer were added into the conventional polyester (polyethylene terephthalate) through the screw of the skin-core composite spinning design, and the components of the core layer were added into the special modified polyester for foaming and the chemical foaming agent (trihydrazine uniform triazine) through the screw. The chemical foaming agent was continuously and accurately added through the loss weight scale. The mass ratio of the special modified polyester for foaming and the chemical foaming agent was 98.5:1.5. During the spinning forming process, the skin layer spinning box temperature was 285°C, the core layer spinning box temperature was 238°C, and the winding speed was 2700 m / min. The skin-core type foaming polyester fiber was obtained in situ. The fiber product indexes are shown in Table 1.

[0086] Example 5

[0087] (1) 85 mol% of terephthalic acid and 15 mol% of isophthalic acid, 99.85 mol% of ethylene glycol, and 0.15 mol% of pentaerythritol were used as polymerization monomers to obtain a low-melting-point, high-melt-strength modified foaming polyester through esterification and polycondensation reaction. The molar ratio of alcohol to acid was 1.3:1. The specific steps are as follows:

[0088] In a polyester polymerization reactor, 319.18 g (5.148 mol) of terephthalic acid, 7.08 g (0.052 mol) of isophthalic acid, 245.52 g (3.40 mol) of ethylene glycol, 5.45 g (0.60 mol) of pentaerythritol, 0.35 g (400 ppm, based on 4 mol of PET as the total mass) of ethylene glycol antimony, and 0.18 g (200 ppm, based on 4 mol of PET as the total mass) of sodium acetate were added. After nitrogen replacement for three times, esterification was first carried out at 220°C under normal pressure for 0.5 h, and then esterification was carried out at 250°C under 0.31 MPa for 2 h, and the esterification water was separated and condensed by an esterification tower. Then the polycondensation temperature was adjusted to 277°C, and the low-melting-point, high-melt-strength modified foaming polyester chip was prepared by pre-polycondensation under low vacuum and polycondensation under high vacuum for 1.5 h, until the stirring power reached the expected value, and finally the melt was discharged at the bottom of the reactor, underwater cooled and cut into particles.

[0089] (2) The low-melting-point, high-melt-strength modified foaming polyester, nucleating agent nano-silicon dioxide, and antioxidant 1010 were added into a double-screw extruder in a mass ratio of 97:2.0:1.0, and the special modified polyester for foaming was obtained by blending and granulating under the processing conditions of a processing temperature of 225°C and a double-screw rotation speed of 220 r / min.

[0090] (3) Through the design of a skin-core composite spinning process, the screw of the skin layer was added with conventional polyester (polyethylene terephthalate), and the screw of the core layer was added with the special modified polyester for foaming and a chemical foaming agent (4,4'-oxobis(benzene sulfonyl urea amide urea)), wherein the chemical foaming agent was continuously and accurately added by a loss-on-weighing balance. The mass ratio of the special modified polyester for foaming and the chemical foaming agent was 98.5:1.5. During the spinning forming process, the skin layer spinning box temperature was 285°C, the core layer spinning box temperature was 240°C, and the winding speed was 2800 m / min, and a skin-core type foaming polyester fiber was obtained in situ. The fiber product indexes are shown in Table 1.

[0091] Example 6

[0092] (1) 85 mol% of terephthalic acid and 15 mol% of isophthalic acid, 99.85 mol% of ethylene glycol, and 0.15 mol% of pentaerythritol were used as polymerization monomers to obtain a low-melting-point, high-melt-strength modified foaming polyester by esterification and polycondensation, and the molar ratio of alcohol to acid was 1.3:1. The specific steps were as follows:

[0093] In a polyester polymerization reactor, 319.18 g (5.148 mol) of terephthalic acid, 7.08 g (0.052 mol) of isophthalic acid, 245.52 g (3.40 mol) of ethylene glycol, 5.45 g (0.60 mol) of pentaerythritol, 0.35 g (400 ppm based on 4 mol of PET as total mass) of ethylene glycol antimony, and 0.18 g (200 ppm based on 4 mol of PET as total mass) of sodium acetate were added. After nitrogen replacement for three times, esterification was first carried out at 220℃ under normal pressure for 0.5 h, and then esterification was carried out at 251℃ under 0.29 MPa for 2 h, and the esterification water was separated and condensed by an esterification tower. Then the polycondensation temperature was adjusted to 280℃, and the stirring power reached the expected value after low vacuum pre-polycondensation and high vacuum polycondensation reaction for 1.5 h, and finally the melt was discharged at the bottom of the reactor, and the pellets were obtained by underwater cooling and cutting, thereby obtaining a low-melting-point and high-melt-strength modified foaming polyester chip.

[0094] (2) The low-melting-point and high-melt-strength modified foaming polyester, the nucleating agent nano diatomite, and the antioxidant 1024 were added into a double-screw extruder in a mass ratio of 98.5:0.5:1.0, and blending and granulation were carried out under the processing conditions of a processing temperature of 228℃ and a double-screw rotation speed of 200 r / min, thereby obtaining a foaming special modified polyester.

[0095] (3) Through a skin-core composite spinning design, the screw of the skin layer was added with conventional polyester (polyethylene terephthalate), and the screw of the core layer was added with the foaming special modified polyester and the chemical foaming agent (trihydrazine s-triazine). The chemical foaming agent was continuously and accurately added by a loss weight scale. The mass ratio of the foaming special modified polyester and the chemical foaming agent was 98.5:1.5. During the spinning forming process, the skin layer spinning box temperature was 285℃, the core layer spinning box temperature was 240℃, and the winding speed was 2600 m / min, thereby obtaining a skin-core type foaming polyester fiber in situ. The fiber product indexes are shown in Table 1.

[0096] Example 7

[0097] (1) 85 mol% of terephthalic acid and 15 mol% of isophthalic acid, 99.85 mol% of ethylene glycol, and 0.15 mol% of pentaerythritol were used as polymerization monomers to obtain a low-melting-point and high-melt-strength modified foaming polyester through esterification and polycondensation reaction, and the molar ratio of alcohol to acid was 1.3:1. The specific steps are as follows:

[0098] In a polyester polymerization reactor, 319.18 g (5.148 mol) of terephthalic acid, 7.08 g (0.052 mol) of isophthalic acid, 245.52 g (3.40 mol) of ethylene glycol, 5.45 g (0.60 mol) of pentaerythritol, 0.35 g (400 ppm based on 4 mol of PET as total mass) of ethylene glycol antimony, and 0.18 g (200 ppm based on 4 mol of PET as total mass) of sodium acetate were added. After nitrogen replacement for three times, esterification was first carried out at 218℃ for 0.5 h under normal pressure, and then esterification was carried out at 248℃ and 0.28 MPa for 2 h, and the esterification water was separated and condensed by an esterification tower. Then the polycondensation temperature was adjusted to 277℃, and the stirring power reached the expected value after low vacuum pre-polycondensation and high vacuum polycondensation reaction for 1.5 h, and finally the melt was discharged at the bottom of the reactor, and the pellets were obtained by underwater cooling and cutting, thereby obtaining a low-melting-point and high-melt-strength modified foaming polyester chip.

[0099] (2) The low-melting-point and high-melt-strength modified foaming polyester, the nucleating agent nano-kaolin, and the antioxidant 264 were added into a double-screw extruder in a mass ratio of 98:1.0:1.0, and were blended and granulated under the processing conditions of a processing temperature of 225℃ and a double-screw rotation speed of 200 r / min, thereby obtaining a foaming special modified polyester.

[0100] (3) Through a skin-core composite spinning design, the screw of the skin layer was added with conventional polyester (polyethylene terephthalate), and the screw of the core layer was added with the foaming special modified polyester and the chemical foaming agent (4,4'-oxobis(benzenesulfonylurea urea)), wherein the chemical foaming agent was continuously and accurately added by a loss-on-weighing balance. The mass ratio of the foaming special modified polyester and the chemical foaming agent was 98:2. During the spinning forming process, the skin layer spinning box temperature was 285℃, the core layer spinning box temperature was 242℃, and the winding speed was 2800 m / min, thereby obtaining a skin-core type foaming polyester fiber in situ. The fiber product indexes are shown in Table 1.

[0101] Example 8

[0102] (1) 85 mol% of terephthalic acid and 15 mol% of isophthalic acid, 99.85 mol% of ethylene glycol, and 0.15 mol% of pentaerythritol were used as polymerization monomers to obtain a low-melting-point and high-melt-strength modified foaming polyester through esterification and polycondensation reaction, and the molar ratio of alcohol to acid was 1.3:1. The specific steps were as follows:

[0103] In a polyester polymerization reactor, 319.18 g (5.148 mol) of terephthalic acid, 7.08 g (0.052 mol) of isophthalic acid, 245.52 g (3.40 mol) of ethylene glycol, 5.45 g (0.60 mol) of pentaerythritol, 0.35 g (400 ppm based on 4 mol of PET as total mass) of ethylene glycol antimony, and 0.18 g (200 ppm based on 4 mol of PET as total mass) of sodium acetate were added. After nitrogen replacement for three times, esterification was first carried out at 217℃ for 0.5 h under normal pressure, and then esterification was carried out at 252℃ and 0.31 MPa for 2 h, and the esterification water was separated and condensed by an esterification tower. Then the temperature of the polycondensation was adjusted to 278℃, and the low vacuum pre-polycondensation and high vacuum polycondensation were carried out for 1.5 h, so that the stirring power reached the expected value, and finally the melt was discharged at the bottom of the reactor, and the particles were obtained by underwater cooling, thereby obtaining a low-melting-point and high-melt-strength modified foaming polyester chip.

[0104] (2) The low-melting-point and high-melt-strength modified foaming polyester, nucleating agent nano-silicon dioxide, and antioxidant 1010 were added into a double-screw extruder in a mass ratio of 98:1.0:1.0, and blending granulation was carried out under the processing conditions of a processing temperature of 220℃ and a double-screw rotation speed of 220 r / min, thereby obtaining a foaming special modified polyester.

[0105] (3) Through a skin-core composite spinning design, the screw of the skin layer was added with conventional polyester (polyethylene terephthalate), and the screw of the core layer was added with the foaming special modified polyester and the chemical foaming agent (N-nitroguanidine), wherein the chemical foaming agent was continuously and accurately added by a loss-on-weighing balance. The mass ratio of the foaming special modified polyester and the chemical foaming agent was 99.5:0.5. During the spinning forming process, the skin layer spinning box temperature was 285℃, the core layer spinning box temperature was 242℃, and the winding speed was 2700 m / min, thereby obtaining a skin-core type foaming polyester fiber in situ. The fiber product indexes are shown in Table 1.

[0106] Example 9

[0107] (1) 85 mol% of terephthalic acid and 15 mol% of isophthalic acid, 99.85 mol% of ethylene glycol, and 0.15 mol% of pentaerythritol were used as polymerization monomers, and esterification and polycondensation were carried out to obtain a low-melting-point and high-melt-strength modified foaming polyester, and the molar ratio of alcohol to acid was 1.3:1. The specific steps are as follows:

[0108] In a polyester polymerization reactor, 319.18 g (5.148 mol) of terephthalic acid, 7.08 g (0.052 mol) of isophthalic acid, 245.52 g (3.40 mol) of ethylene glycol, 5.45 g (0.60 mol) of pentaerythritol, 0.35 g (400 ppm, based on 4 mol of PET as the total mass) of ethylene glycol antimony, and 0.18 g (200 ppm, based on 4 mol of PET as the total mass) of sodium acetate were added. After nitrogen replacement for three times, esterification was first carried out at 218°C for 0.5 h under normal pressure, and then esterification was carried out at 246°C and 0.28 MPa for 2 h, and esterification water was separated and condensed for 1.7 h through an esterification tower. Then the temperature for polycondensation was adjusted to 276°C, and low-vacuum pre-polycondensation and high-vacuum polycondensation were carried out until the stirring power reached the expected value, and finally the melt was discharged at the bottom of the reactor, and the product was obtained by underwater cooling and pelletizing, thereby obtaining a low-melting-point and high-melt-strength modified foaming polyester chip.

[0109] (2) The low-melting-point and high-melt-strength modified foaming polyester, the nucleating agent nano diatomite, and the antioxidant 1076 were added into a double-screw extruder in a mass ratio of 98:1.0:1.0, and blending and granulation were carried out under the processing conditions of a processing temperature of 225°C and a double-screw rotation speed of 220 r / min, thereby obtaining a foaming special modified polyester.

[0110] (3) Through a sheath-core composite spinning design, the screw of the sheath layer was added with conventional polyester (polyethylene terephthalate), and the screw of the core layer was added with the foaming special modified polyester and the chemical foaming agent (4,4'-oxobis(benzene sulfonyl urea amide urea)), and the chemical foaming agent was continuously and accurately added through a weight loss balance. The mass ratio of the foaming special modified polyester and the chemical foaming agent was 98.5:1.5. During the spinning forming process, the temperature of the sheath layer spinning box was 285°C, the temperature of the core layer spinning box was 238°C, and the winding speed was 2800 m / min, thereby obtaining a sheath-core type foaming polyester fiber in situ. The fiber product indexes are shown in Table 1.

[0111] Example 10

[0112] (1) 85 mol% of terephthalic acid and 15 mol% of isophthalic acid, 99.85 mol% of ethylene glycol, and 0.15 mol% of pentaerythritol were used as polymerization monomers, and esterification and polycondensation were carried out to obtain a low-melting-point and high-melt-strength modified foaming polyester, and the molar ratio of alcohol to acid was 1.3:1. The specific steps were as follows:

[0113] In a polyester polymerization reactor, 319.18 g (5.148 mol) of terephthalic acid, 7.08 g (0.052 mol) of isophthalic acid, 245.52 g (3.40 mol) of ethylene glycol, 5.45 g (0.60 mol) of pentaerythritol, 0.35 g (400 ppm, based on 4 mol of PET as the total mass) of ethylene glycol antimony, and 0.18 g (200 ppm, based on 4 mol of PET as the total mass) of sodium acetate were added. After nitrogen replacement for three times, esterification was first carried out at 218°C under normal pressure for 0.5 h, and then esterification was carried out at 246°C under 0.30 MPa for 2 h, and the esterification water was separated and condensed by an esterification tower. Then the temperature of the polycondensation was adjusted to 276°C, and the low vacuum pre-polycondensation and high vacuum polycondensation were carried out for 1.3 h, so that the stirring power reached the expected value, and finally the melt was discharged at the bottom of the reactor, and the particles were obtained by underwater cooling, thereby obtaining a low-melting-point and high-melt-strength modified foaming polyester chip.

[0114] (2) The low-melting-point and high-melt-strength modified foaming polyester, the nucleating agent nano kaolin, and the antioxidant 1024 were added into a double-screw extruder in a mass ratio of 98:1.0:1.0, and were blended and granulated under the processing conditions of a processing temperature of 228°C and a double-screw rotation speed of 250 r / min, thereby obtaining a foaming special modified polyester.

[0115] (3) Through a skin-core composite spinning design, the screw of the skin layer was added with conventional polyester (polyethylene terephthalate), and the screw of the core layer was added with the foaming special modified polyester and the chemical foaming agent (N-nitroguanidine), wherein the chemical foaming agent was continuously and accurately added by a loss-on-weighing balance. The mass ratio of the foaming special modified polyester and the chemical foaming agent was 98.5:1.5. During the spinning forming process, the skin layer spinning box temperature was 285°C, the core layer spinning box temperature was 238°C, and the winding speed was 2700 m / min, thereby obtaining a skin-core type foaming polyester fiber in situ. The fiber product indexes are shown in Table 1.

[0116] Comparative Example 1

[0117] (1) The conventional PET polyester, the nucleating agent nano silicon dioxide, and the antioxidant 1024 were added into a double-screw extruder in a mass ratio of 98:1.0:1.0, and were blended and granulated under the processing conditions of a processing temperature of 245°C and a double-screw rotation speed of 300 r / min, thereby obtaining a foaming polyester.

[0118] (2) By core-sheath composite spinning design, the screw of the sheath layer adds conventional polyester (polyethylene terephthalate), and the screw of the core layer adds foamed polyester and chemical foaming agent (4, 4'-oxybis (phenylsulfonyl urea amide urea)), wherein the chemical foaming agent is continuously and accurately added by a loss weight scale. The mass ratio of the sheath to the core is 4:6, and the mass ratio of the foamed polyester to the chemical foaming agent is 98.5:1.5. During the spinning forming process, the sheath layer spinning box temperature is 285°C, the core layer spinning box temperature is 275°C, and the winding speed is 2800 m / min. A sheath-core type foamed polyester fiber is obtained in situ. The fiber product index is shown in Table 1. Figure 2 is the cross-sectional electron microscope image of the foamed polyester fiber of Comparative Example 1.

[0119] Comparative Example 2

[0120] (1) 85 mol% terephthalic acid and 15 mol% isophthalic acid, 99.85 mol% ethylene glycol and 0.15 mol% pentaerythritol are used as polymerization monomers to obtain a low-melting-point and high-melt-strength modified foamed polyester through esterification and polycondensation reaction. The molar ratio of alcohol to acid is 1.3:1. The specific steps are as follows:

[0121] In the polyester polymerization reactor, 319.18 g (5.148 mol) of terephthalic acid, 7.08 g (0.052 mol) of isophthalic acid, 245.52 g (3.40 mol) of ethylene glycol, 5.45 g (0.60 mol) of pentaerythritol, 0.35 g (400 ppm, based on 4 mol of PET as total mass) of ethylene glycol antimony, and 0.18 g (200 ppm, based on 4 mol of PET as total mass) of sodium acetate are added. After nitrogen replacement for three times, esterification is first carried out at 215°C under normal pressure for 0.5 h, and then esterification is carried out at 245°C and 0.30 MPa for 2 h. The esterification water is separated and condensed by an esterification tower. Then the polycondensation temperature is adjusted to 278°C, and low vacuum pre-polycondensation and high vacuum polycondensation are carried out for 1.5 h, so that the stirring power reaches the expected value. Finally, the melt is discharged at the bottom of the reactor, cooled underwater, and cut into particles to obtain low-melting-point and high-melt-strength modified foamed polyester chips.

[0122] (2) The low-melting-point and high-melt-strength modified foamed polyester, the nucleating agent nano-silicon dioxide, and the antioxidant 1024 are added into a double-screw extruder in a mass ratio of 98:1.0:1.0, and are blended and granulated under the processing conditions of a processing temperature of 225°C and a double-screw rotation speed of 200 r / min to obtain a foamed special modified polyester.

[0123] (3) By core-sheath composite spinning design, the screw of the sheath layer adds the foaming special modified polyester, and the screw of the core layer adds the foaming special modified polyester and the chemical foaming agent (4, 4'-oxybis (benzenesulfonyl urea)), wherein the chemical foaming agent is continuously and accurately added by the loss weight scale. The mass ratio of the foaming special modified polyester and the chemical foaming agent is 98.5:1.5. In the spinning forming process, the sheath layer spinning box temperature is 255℃, the core layer spinning box temperature is 240℃, and the winding speed is 2800m / min. The core-sheath type foaming polyester fiber is obtained in situ. The fiber product index is shown in Table 1.

[0124] Comparative Example 3

[0125] (1) 85mol% terephthalic acid and 15mol% isophthalic acid, 99.85mol% ethylene glycol and 0.15mol% pentaerythritol are used as polymerization monomers to obtain a low melting point and high melt strength modified foaming polyester through esterification and polycondensation reaction. The molar ratio of alcohol to acid is 1.3:1. The specific steps are as follows:

[0126] In the polyester polymerization reactor, 319.18g (5.148mol) of terephthalic acid, 7.08g (0.052mol) of isophthalic acid, 245.52g (3.40mol) of ethylene glycol, 5.45g (0.60mol) of pentaerythritol, 0.35g (400ppm, based on 4mol of PET as total mass) of ethylene glycol antimony and 0.18g (200ppm, based on 4mol of PET as total mass) of sodium acetate are added. After three times of nitrogen replacement, esterification is carried out at 215℃ under normal pressure for 0.5h, and then esterification is carried out at 245℃ under 0.30MPa for 2h. The esterification water is separated and condensed by an esterification tower. Then the polycondensation temperature is adjusted to 278℃, and the low vacuum pre-polycondensation and high vacuum polycondensation reaction is carried out for 1.5h, so that the stirring power reaches the expected value. Finally, the melt is discharged at the bottom of the reactor, and the product is cut into particles by underwater cooling. The low melting point and high melt strength modified foaming polyester chip is obtained. The polyester product index is shown in Table 1.

[0127] (2) The low melting point and high melt strength modified foaming polyester, nucleating agent nano silicon dioxide and antioxidant 1024 are added into a double screw extruder according to the mass ratio of 98:1.0:1.0, and the foaming special modified polyester is obtained by blending and granulating under the processing conditions of processing temperature of 225℃ and double screw speed of 200r / min.

[0128] (3) By the design of core-sheath composite spinning, the screw of sheath layer adds conventional polyester (polyethylene terephthalate), and the screw of core layer adds foaming special modified polyester and chemical foaming agent (azodicarbonamide), wherein the chemical foaming agent is continuously and accurately added by the loss weight scale. The mass ratio of foaming special modified polyester and chemical foaming agent is 98.5:1.5. During the spinning forming process, the temperature of sheath layer spinning box is 285℃, the temperature of core layer spinning box is 240℃, and the winding speed is 2800m / min. The core-sheath type foaming polyester fiber is obtained in situ. The fiber product index is shown in Table 1.

[0129] Comparative Example 4

[0130] (1) 85mol% terephthalic acid and 15mol% isophthalic acid, 99.85mol% ethylene glycol and 0.15mol% pentaerythritol are used as polymerization monomers to obtain low melting point and high melt strength modified foaming polyester through esterification and polycondensation reaction. The molar ratio of alcohol to acid is 1.3:1. The specific steps are as follows:

[0131] In the polyester polymerization reactor, 319.18g (5.148mol) of terephthalic acid, 7.08g (0.052mol) of isophthalic acid, 245.52g (3.40mol) of ethylene glycol, 5.45g (0.60mol) of pentaerythritol, 0.35g (400ppm, based on the total mass of 4mol of PET) of ethylene glycol antimony and 0.18g (200ppm, based on the total mass of 4mol of PET) of sodium acetate are added. After three times of nitrogen replacement, esterification is carried out at 215℃ under normal pressure for 0.5h, and then esterification is carried out at 245℃ and 0.30MPa for 2h. The esterification water is separated and condensed by an esterification tower. Then the polycondensation temperature is adjusted to 278℃, and the low vacuum pre-polycondensation and high vacuum polycondensation reaction is carried out for 1.5h, so that the stirring power reaches the expected value. Finally, the melt is discharged at the bottom of the reactor, and the product is cut into particles by underwater cooling. Low melting point and high melt strength modified foaming polyester chips are obtained. The polyester product index is shown in Table 1.

[0132] (2) The low melting point and high melt strength modified foaming polyester, nucleating agent nano silicon dioxide and antioxidant 1024 are added into a double screw extruder according to the mass ratio of 98:1.0:1.0, and the special modified polyester for foaming is obtained by blending and granulating under the processing conditions of processing temperature of 225℃ and double screw speed of 200r / min.

[0133] (3) By the design of core-sheath composite spinning, the screw of sheath layer adds conventional polyester (polyethylene terephthalate), and the screw of core layer adds foaming special modified polyester and chemical foaming agent (sodium carbonate), wherein the chemical foaming agent is continuously and accurately added by the loss weight scale. The mass ratio of foaming special modified polyester and chemical foaming agent is 98.5:1.5. During the spinning forming process, the sheath layer spinning box temperature is 285℃, the core layer spinning box temperature is 240℃, and the winding speed is 2800m / min. The core-sheath type foaming polyester fiber is obtained in situ. The fiber product index is shown in Table 1.

[0134] Comparative Example 5

[0135] (1) 85mol% terephthalic acid and 15mol% isophthalic acid, 99.85mol% ethylene glycol and 0.15mol% pentaerythritol are used as polymerization monomers to obtain low melting point and high melt strength modified foaming polyester through esterification and polycondensation reaction. The molar ratio of alcohol to acid is 1.3:1. The specific steps are as follows:

[0136] In the polyester polymerization reactor, 319.18g (5.148mol) of terephthalic acid, 7.08g (0.052mol) of isophthalic acid, 245.52g (3.40mol) of ethylene glycol, 5.45g (0.60mol) of pentaerythritol, 0.35g (400ppm, based on 4mol of PET as total mass) of ethylene glycol antimony and 0.18g (200ppm, based on 4mol of PET as total mass) of sodium acetate are added. After three times of nitrogen replacement, esterification is carried out at 215℃ under normal pressure for 0.5h, and then esterification is carried out at 245℃ under 0.30MPa for 2h. The esterification water is separated and condensed by an esterification tower. Then the polycondensation temperature is adjusted to 278℃, and the low vacuum pre-polycondensation and high vacuum polycondensation reaction is carried out for 1.5h, so that the stirring power reaches the expected value. Finally, the melt is discharged at the bottom of the reactor, and the product is cut into particles by underwater cooling. Low melting point and high melt strength modified foaming polyester chips are obtained. The polyester product index is shown in Table 1.

[0137] (2) The low melting point and high melt strength modified foaming polyester, nucleating agent nano silicon dioxide and antioxidant 1024 are added into the twin-screw extruder according to the mass ratio of 98:1.0:1.0, and the special modified polyester for foaming is obtained by blending and granulating under the processing conditions of processing temperature of 225℃ and double screw speed of 200r / min.

[0138] (3) Through the design of skin-core composite spinning, the screw of the skin layer component adds conventional polyester (polyethylene terephthalate), and the screw of the core layer adds special modified polyester for foaming and chemical foaming agent (ammonium acetate), wherein the chemical foaming agent is continuously and accurately added by the loss weight scale. The ratio of skin to core is 4:6, and the mass ratio of special modified polyester for foaming to chemical foaming agent is 98.5:1.5. During the spinning forming process, the skin layer spinning box temperature is 285℃, the core layer spinning box temperature is 240℃, and the winding speed is 2800m / min. A skin-core type foamed polyester fiber is obtained in situ. The fiber product indicators are shown in Table 1.

[0139] Performance test

[0140] The modified foamed polyester chips and foamed polyester fibers of each example and comparative example were tested for performance, and the results are shown in Tables 1 and 2. The test method is as follows:

[0141] (1) The foamed polyester chips were evaluated for intrinsic viscosity and melting point according to the standard “GB / T 14190-2017 Fiber Grade Polyester (PET) Chip Test Method”.

[0142] (2) The foamed polyester chips were evaluated for melt flow rate according to the standard “GB / T 3682-2000 Determination of Melt Mass Flow Rate and Melt Volume Flow Rate of Thermoplastics”.

[0143] (3) The polyester fibers were evaluated for tensile strength and elongation at break after tensile deformation according to the standard “GB / T 14344-2022 Test Method for Tensile Properties of Chemical Fiber Filaments”.

[0144] (4) The polyester fibers were evaluated for thermal storage performance after knitting, and the thermal retention rate was evaluated according to “FZ / T 73022-2019 Knitted Thermal Underwear”.

[0145] Table 1: Foamed polyester chip indicators

[0146]

[0147] Table 2: Foamed polyester fiber indicators and performance

[0148]

[0149] In Table 1, the basic physical indicators of the prepared modified foaming polyester are mainly concerned, the intrinsic viscosity is mainly investigated to see whether the chip meets the needs of spinning processing, the melting point is mainly investigated to see whether it can match the decomposition and foaming temperature of the foaming agent, and the melt flow rate is mainly investigated to see the melt flow performance. Table 2 mainly concerns the indicators related to the prepared foaming polyester fiber material and application, the spinnability is mainly investigated to see the breakage and the like in the fiber forming process, the mechanical property is mainly investigated to see the application of the fiber material in subsequent weaving processing, the weight reduction rate is mainly investigated to see how much the bubble structure of the fiber is formed, and the warmth retention rate is mainly investigated to see the level of the heat insulation performance of the fabric.

[0150] As can be seen from Tables 1-2, by introducing the third component isophthalic acid to destroy the regular molecular chain structure of the conventional polyester, the melting point of the polyester is reduced to meet the application temperature of some high-decomposition-temperature foaming agents; by introducing the fourth component pentaerythritol to enhance the melt strength, the function of supporting the bubble structure is played; by using the skin-core composite structure design, the skin layer guarantees the integrity of the fiber structure and the mechanical property meets the standard, the core layer generates the bubble structure by chemical foaming, and the air is introduced to improve the warmth retention performance. Specifically:

[0151] By comparing Examples 1, 2 and the best embodiment, it can be found that the weight reduction rate of the foaming fiber prepared by the modified foaming polyester with a higher melting point (Example 1) decreases, which is because the higher melting point modified polyester needs a higher core layer spinning temperature, resulting in faster decomposition of the foaming agent, more decomposition process occurs before fiber forming, and the bubble structure in the fiber is reduced; but the foaming fiber prepared by the modified foaming polyester with a lower melting point (Example 2) has more bubble formation, and the mechanical property of the fiber decreases.

[0152] By comparing Examples 3, 4 and the best embodiment, it can be found that when the melt strength is higher (Example 3), the mechanical property of the fiber is improved, but the melt flow performance is poor, resulting in poor spinnability and easy breakage; and when the melt strength is lower (Example 4), the support for the bubble structure is weak, so the weight reduction rate of the fiber decreases.

[0153] By comparing Examples 5, 6 and the best embodiment, it can be found that more nucleating agents (Example 5) can increase the nucleation density, which is conducive to the formation of the bubble structure and thus improves the weight reduction rate, but the increased amount of the nucleating agent is not conducive to its dispersion in the matrix, which will also cause breakage and the like during spinning. When the nucleating agent is less (Example 6), the bubble is less and the size is large, and the fiber strength decreases.

[0154] By comparing Examples 7, 8 and the best embodiment, it can be found that when the foaming agent is added more (Example 7), the weight reduction of the fiber can be increased, but the mechanical property decreases significantly; and when the foaming agent is added less (Example 8), the weight reduction rate of the fiber is not high, which further leads to the unobvious improvement of the warmth retention rate.

[0155] From the comparison of the example 9, 10 and the best example, it can be found that the proportion of the skin and core layer components also needs to be considered comprehensively according to the fiber mechanical index and the warm-keeping performance. The core layer of the example 9 is more, and the weight reduction rate and the warm-keeping rate are further improved, but the fiber mechanical performance is seriously decreased. The core layer of the example 10 is less, the fiber mechanical index is excellent, but the warm-keeping performance is poor.

[0156] From the comparison of the comparative example 1 and the best example, it can be found that the conventional polyester is used as the fiber core layer material, the spinning temperature is higher, the melt strength is insufficient, the foaming agent is decomposed early and it is difficult to form stable cells (as shown in Figure 2 ), so the weight reduction rate and the warm-keeping rate are lower.

[0157] From the comparison of the comparative example 2 and the best example, it can be found that the modified low-melting polyester is used as the fiber skin layer material, and the fiber mechanical performance is poor.

[0158] The difference between the comparative examples 3-5 and the best example is that the conventional chemical foaming agent is used. Since the thermal decomposition temperature is lower, it is decomposed completely in the screw mixing stage before fiber formation, and the cell structure is disappeared immediately after the formation due to the shearing action, so it is not suitable as the foaming agent of the polyester fiber.

[0159] The raw materials and the equipment used in the present application are the common raw materials and the equipment in the field if no special description is given; the method used in the present application is the conventional method in the field if no special description is given.

[0160] The above is only the preferred embodiment of the present application, and does not limit the present application in any way. Any simple modification, change and equivalent transformation of the above embodiment according to the technical essence of the present application still belongs to the protection scope of the technical solution of the present application.

Claims

1. A core-sheath type foamed polyester fiber, characterized in that: It includes a foamed polyester core layer and a polyester sheath layer, which are obtained through core-sheath composite spinning; The foamed polyester core layer is obtained by melt spinning after blending modified foamed polyester with nucleating agent and foaming agent; The foaming agent is selected from 4,4'-oxobis(benzenesulfonamide), trihydrazine, and N One or more of -nitroguanidine; The nucleating agent is selected from one or more of nano-silica, nano-titanium dioxide, nano-diatomite, and nano-kaolin. The modified foamed polyester is obtained by esterification and polycondensation of terephthalic acid, isophthalic acid, ethylene glycol and pentaerythritol as monomers; Isophthalic acid accounts for 10-20 mol% of the total of terephthalic acid and isophthalic acid. Pentaerythritol accounts for 0.02-0.2 mol of the total amount of ethylene glycol and pentaerythritol.

2. The core-sheath type foamed polyester fiber according to claim 1, characterized in that: The mass ratio of the foamed polyester core layer to the polyester skin layer is 4:6-7:

3.

3. The core-sheath type foamed polyester fiber according to claim 1, characterized in that: The foaming agent accounts for 0.5-2 wt% of the total raw materials of the foamed polyester core layer; The nucleating agent accounts for 0.5-2 wt% of the total raw materials of the foamed polyester core layer.

4. The core-sheath type foamed polyester fiber according to claim 1, characterized in that: Antioxidants are also added during the formation of the foamed polyester core layer.

5. The core-sheath type foamed polyester fiber according to claim 1, characterized in that: The alkyd molar ratio in the preparation process of the modified foamed polyester is 1.2-1.4:

1.

6. A method for preparing core-sheath type foamed polyester fiber according to any one of claims 1-5, characterized in that... include: 1) Modified foamed polyester was obtained by esterification and polycondensation of terephthalic acid, isophthalic acid, ethylene glycol and pentaerythritol as monomers; 2) Using modified foamed polyester, foaming agent and nucleating agent as core material and polyester as skin material, the core-skin foamed polyester fiber is prepared by melt spinning.

7. The preparation method according to claim 6, characterized in that: In step 1), The esterification process involves first esterifying at atmospheric pressure (205-225℃) for 30-50 minutes under an inert atmosphere, followed by esterification at 225-255℃ and 0.2-0.4 MPa for 90-180 minutes.

8. The preparation method according to claim 6, characterized in that: In step 1), the polycondensation is performed under vacuum conditions at 265-285°C for 0.5-2 hours under negative compression.

9. The preparation method according to claim 6, characterized in that: In step 2), a twin-screw extruder is used for melt blending; the processing temperature of the twin-screw mixing section is 210-230℃, and the twin-screw speed is 100-300 r / min.

10. The preparation method according to claim 6, characterized in that: In step 2), during the melt spinning process, the temperature of the outer spinning box is 285-295℃, the temperature of the core spinning box is 235-245℃, and the winding speed is 2500-3000 m / min.

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