Polyester, nonwoven fabric and method for producing the same

Abstract

The application relates to the field of high polymer chemical industry and discloses a polyester and a preparation method thereof. The melting point of the polyester is 158-205 DEG C, and the heat distortion temperature of the polyester is 48-78 DEG C under the condition of a pressure of 0.45 MPa. The preparation method of the polyester comprises the following steps: (1) mixing a dibasic acid monomer, a dibasic alcohol monomer, a modified monomer and a catalyst to carry out a first stage reaction under esterification reaction conditions to obtain a prepolymer; the modified monomer contains a monomer with a structure shown in formula (I) and a monomer with a structure shown in formula (II); and (2) carrying out a second stage reaction on the prepolymer under polycondensation reaction conditions. The polyester has a low melting point, a high heat distortion temperature and good heat resistance.

Description

Technical Field

[0001] This invention relates to the field of polymer chemistry, specifically to a polyester, a nonwoven fabric, and a method for preparing the same. Background Technology

[0002] Currently, most squeeze rollers in domestic metal sheet and strip production lines are made of rubber or polyurethane, which have drawbacks such as poor drying and cleaning effects, easy slippage, short service life, and poor heat and acid / alkali corrosion resistance. A new type of nonwoven fabric roller can maintain close contact with the metal sheet and strip, achieving optimal squeezing effect. Its friction coefficient is 24 times that of rubber or polyurethane rollers, solving the slippage problem. The nonwoven fabric squeeze roller consists of high-strength nonwoven fabric and a metal mandrel. Degreasing and pickling machines in metal sheet and strip processing require squeeze rollers for the strip squeezing process. Therefore, the selection of the nonwoven fabric material is crucial, as these nonwoven fabric squeeze rollers need excellent resilience and strength.

[0003] Polypropylene terephthalate (PTT) fiber possesses excellent elastic recovery and softness, superior wrinkle resistance, sunlight resistance, and dyeability, making it suitable for use in high-end apparel fabrics, elastic swimwear, underwear, interior decoration, carpets, and more. Besides its fiber applications, PTT also has potential value in nonwoven fabrics, films, thermoplastic engineering plastics, and mold products. Low-melting-point PTT, as a raw material for producing PTT nonwoven fabrics, can be directly hot-rolled without the need for additional fiber composites or adhesives, offering advantages such as convenience, speed, and environmental friendliness. However, while copolymerization modification lowers the melting point of PTT, it also reduces its glass transition temperature and heat resistance. Since the pre-processing of the squeeze rollers in production often involves high-temperature passivation, the operating temperature of the squeeze rollers is typically above 70°C. Some squeeze rollers also incorporate a heat-conducting layer to improve drying efficiency, necessitating materials with certain high-temperature resistance for the nonwoven rollers.

[0004] Chinese invention application number 202010730323.1 discloses a high-elasticity nonwoven material for squeeze rollers and its preparation method, comprising an upper layer, a middle layer, and a lower layer. The upper and lower layers are composed of the following raw material components by mass percentage: 70%-90% PTT fiber and 10%-30% ES fiber, with the sum of the two raw materials being 100%; the middle layer is 100% PTT fiber. Chinese invention application number 202010816166.6 discloses a method for manufacturing a high-acid and alkali-resistant nonwoven material for squeeze rollers. First, 70%-90% high-strength polypropylene fiber and 10%-30% ultra-high molecular weight polyethylene fiber are weighed by mass percentage; the high-strength polypropylene fiber and ultra-high molecular weight polyethylene fiber are mixed to form a mixed fiber; the high-acid and alkali-resistant nonwoven material for squeeze rollers is then prepared. While these two inventions solve the problems of poor acid and alkali resistance and low strength in existing nonwoven squeeze rollers, their heat resistance is poor and needs improvement.

[0005] Therefore, the preparation of a nonwoven fabric with good resilience and heat resistance has great market potential. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem that modifying polyester to lower its melting point leads to a decrease in its glass transition temperature and thus a decline in its heat resistance. This invention provides a polyester, a nonwoven fabric, and a method for preparing the same, in which the polyester has a low melting point and a high heat distortion temperature, and exhibits good heat resistance.

[0007] To achieve the above objectives, the first aspect of the present invention provides a polyester having a melting point of 158-205°C and a heat distortion temperature of 48-78°C under a pressure of 0.45 MPa.

[0008] A second aspect of the present invention provides a method for preparing polyester, the method comprising the following steps:

[0009] (1) Under esterification reaction conditions, diacid monomers, diol monomers, modified monomers and catalysts are mixed to carry out the first stage reaction to obtain prepolymers;

[0010] The modified monomer contains a monomer having the structure shown in formula (I) and a monomer having the structure shown in formula (II);

[0011]

[0012] Where n is an integer from 4 to 10, and R1, R2, R3 and R4 are each independently selected from hydrogen or C1-C4 alkyl groups;

[0013] (2) Under polycondensation reaction conditions, the prepolymer is subjected to a second-stage reaction.

[0014] A third aspect of the present invention provides a nonwoven fabric prepared using the polyester described in the first aspect and / or the polyester prepared by the preparation method described in the second aspect.

[0015] The beneficial effects of the present invention through the above technical solution are as follows:

[0016] The polyester provided by this invention has a low melting point and a high heat distortion temperature, as well as good heat resistance, and has significant market prospects and environmental benefits. The polyester preparation method provided by this invention modifies the polyester using monomers having the structure shown in formula (I) and monomers having the structure shown in formula (II), enabling the prepared polyester to have a low melting point while significantly improving its heat distortion temperature and heat resistance.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0018] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0019] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0020] During the research process, the inventors of this invention unexpectedly discovered that adding monomers with the structure shown in formula (I) and monomers with the structure shown in formula (II) during the polyester preparation process can effectively reduce the melting point of polyester while avoiding a decrease in heat distortion temperature, thereby improving its heat resistance. This can be used to prepare a nonwoven fabric with good resilience and heat resistance, and the nonwoven fabric material can be used as a raw material for preparing nonwoven fabric squeeze rollers.

[0021] The first aspect of the present invention provides a polyester having a melting point of 158-205°C and a heat distortion temperature of 48-78°C under a pressure of 0.45 MPa.

[0022] In this invention, the melting point was measured using a Perkin-Elmer DSC-7 differential scanning calorimeter from PE Corporation. The heat distortion temperature was determined by testing the sample under a load of 0.45 MPa according to GB / T1634.2-2004 Determination of Deflection Temperature under Load Part 2: Plastics, Hard Rubber and Long Fiber Reinforced Composites.

[0023] The polyester provided by this invention has a specific melting point and heat distortion temperature. It has a low melting point and a high heat distortion temperature, and good heat resistance. When used to prepare nonwoven fabrics, it can be directly hot-rolled without the need for additional composite fibers or adhesives. It has the advantages of being convenient, quick, green and environmentally friendly.

[0024] According to the present invention, preferably, the polyester has a melting point of 169-200°C and a heat distortion temperature of 62-78°C under a pressure of 0.45 MPa.

[0025] To enable the polyester provided by this invention to be used in the preparation of nonwoven fabrics, the polyester should possess high strength in addition to having a specific melting point and heat distortion temperature. Preferably, the viscosity of the polyester is 0.7-1.0 dL / g, and polyesters with this viscosity have better strength than low-viscosity polyesters.

[0026] In this invention, the viscosity of polyester is tested in accordance with GB / T14189-2008 Fiber Grade Polyester Chips.

[0027] According to the present invention, preferably, the polyester contains structural unit (A) of formula (I) and structural unit (B) of formula (II);

[0028]

[0029] Wherein, n is an integer from 4 to 10, and R1, R2, R3, and R4 are each independently selected from hydrogen or C1-C4 alkyl groups. The inventors have discovered that, under this preferred embodiment, the polyester having structural unit (A) and structural unit (B) can increase the heat distortion temperature while lowering the melting point, and exhibits good heat resistance.

[0030] In this invention, in the monomer having the structure shown in formula (I), n can be 4, 5, 6, 7, 8, 9 or 10; in the monomer having the structure shown in formula (II), R1, R2, R3 and R4 can each be independently hydrogen, hydroxyl, straight-chain alkyl or cycloalkyl, specifically methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, tert-butyl or other feasible C1-C4 alkyl.

[0031] According to the present invention, preferably, in the polyester, the content of the structural unit (A) is 1-12% by weight, specifically 1% by weight, 6% by weight, 12% by weight, or any value between the two aforementioned values; the content of the structural unit (B) is 5-40% by weight, specifically 5% by weight, 20% by weight, 40% by weight, or any value between the two aforementioned values. It should be noted that the content of structural unit (A) being 1-12% by weight means that the content of structural unit (A) in the polyester accounts for 1-12% of the total mass of the polyester; the content of structural unit (B) being 5-40% by weight means that the content of structural unit (B) in the polyester accounts for 5-40% of the total mass of the polyester.

[0032] According to the present invention, preferably, the polyester contains a metal element.

[0033] According to the present invention, preferably, the metallic element is antimony and / or titanium.

[0034] According to the present invention, preferably, the content of the metal element in the polyester is 0.01-0.04% by weight, specifically 0.01%, 0.02%, 0.03%, 0.04%, or any value between the two aforementioned values.

[0035] A second aspect of the present invention provides a method for preparing polyester, the method comprising the following steps:

[0036] (1) Under esterification reaction conditions, diacid monomers, diol monomers, modified monomers and catalysts are mixed to carry out the first stage reaction to obtain prepolymers;

[0037] The modified monomer contains a monomer having the structure shown in formula (I) and a monomer having the structure shown in formula (II);

[0038]

[0039] Where n is an integer from 4 to 10, and R1, R2, R3 and R4 are each independently selected from hydrogen or C1-C4 alkyl groups;

[0040] (2) Under polycondensation reaction conditions, the prepolymer is subjected to a second-stage reaction.

[0041] The polyester preparation method provided by this invention is simple and suitable for industrial production. This invention utilizes the synergistic effect between monomers having the structure shown in Formula (II) and monomers having the structure shown in Formula (I) to lower the melting point of polyester while increasing its heat distortion temperature, thus improving its heat resistance.

[0042] In this invention, in the monomer having the structure shown in formula (I), n can be 4, 5, 6, 7, 8, 9 or 10.

[0043] According to the present invention, specifically, the monomer having the structure shown in formula (I) is the compound shown in formula (III);

[0044]

[0045] Where x is an integer between 3 and 9.

[0046] In the monomers of the present invention having the structure shown in formula (II), R1, R2, R3 and R4 can each be independently hydrogen, hydroxyl, straight-chain alkyl or cycloalkyl, specifically methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, tert-butyl or other feasible C1-C4 alkyl.

[0047] According to the present invention, preferably, R1, R2, R3 and R4 can all be hydrogen, and specifically, the monomer having the structure shown in formula (II) is preferably isophthalic acid.

[0048] According to the present invention, in order to further improve the heat distortion temperature of polyester while lowering the melting point, preferably, the weight ratio of the monomer having the structure shown in formula (II) to the monomer having the structure shown in formula (I) is 0.4-8:1, specifically 0.4:1, 2:1, 4:1, 6:1, 8:1, or any value between the two aforementioned values.

[0049] According to the present invention, preferably, the dicarboxylic acid monomer is an aromatic dicarboxylic acid and is different from the monomer having the structure shown in formula (II), more preferably at least one of terephthalic acid, 4,4'-biphenyl dicarboxylic acid and 2,6-naphthalenedicarboxylic acid, and even more preferably terephthalic acid.

[0050] According to the present invention, the diol monomer can be any diol, preferably ethylene glycol and / or propylene glycol, more preferably propylene glycol, specifically 1,2-propanediol or 1,3-propanediol.

[0051] According to the present invention, in order to further reduce the melting point of polyester while increasing its heat distortion temperature, preferably, the weight ratio of the diformic acid monomer, the diol monomer and the modified monomer is 0.5-1.2:1:0.2-0.8.

[0052] According to the present invention, preferably, the catalyst contains an antimony-based catalyst and / or a titanium-based catalyst. The catalyst may contain an antimony-based catalyst, may contain a titanium-based catalyst, or may contain both an antimony-based catalyst and a titanium-based catalyst. The inventors have found that, under this preferred embodiment, the heat distortion temperature of the polyester can be further increased while simultaneously lowering its melting point, thus further improving its heat resistance.

[0053] According to the present invention, there is no particular limitation on the types of antimony-based catalysts and titanium-based catalysts. In order to further reduce the melting point of polyester while increasing its heat distortion temperature, preferably, the antimony-based catalyst is selected from at least one of antimony glycolate, antimony trioxide and antimony acetate, more preferably antimony glycolate; the titanium-based catalyst is tetrabutyl titanate and / or titanium glycolate, more preferably tetrabutyl titanate.

[0054] In this invention, the content of the catalyst can be selected according to the performance requirements of the polyester. Preferably, the amount of catalyst added is 0.5-1.5g relative to 1000g of diacid monomer, specifically 0.5g, 1.0g, 1.5g, or any value between the two aforementioned values.

[0055] In this invention, the above-mentioned dicarboxylic acid monomer, diol monomer, modified monomer and catalyst can all be commercially available, or can be prepared by means of methods disclosed in the prior art.

[0056] According to the present invention, in order to further improve the reaction rate and product yield of the first-stage reaction, preferably, the conditions of the esterification reaction include at least: isolation from oxygen, a temperature of 230-250°C, specifically 230°C, 240°C, 250°C, or any value between the two aforementioned values; and a pressure of 0.18-0.22 MPa, specifically 0.18 MPa, 0.20 MPa, 0.22 MPa, or any value between the two aforementioned values. Isolation from oxygen can be achieved by introducing an inert gas such as nitrogen or helium into the reaction system; specifically, nitrogen is used as the inert gas.

[0057] In this invention, the first stage reaction is carried out under stirring conditions. There is no particular limitation on the stirring rate, which can be determined by the experimenter based on the actual situation.

[0058] In this invention, the experimenter can determine the conditions for the termination of the first-stage reaction based on actual conditions, such as the amount of water in the product. Preferably, the conditions for the termination of the first-stage reaction process include at least: the amount of water produced is not less than 90% of the theoretical amount of water produced.

[0059] According to the present invention, preferably, the conditions for the polycondensation reaction include at least: a temperature of 240-260°C, specifically 240°C, 250°C, 260°C, or any value between the two aforementioned values; and a vacuum pressure of less than 100 Pa.

[0060] In this invention, the experimenter can determine the conditions for the termination of the second-stage reaction process based on actual conditions. Preferably, the conditions for the termination of the second-stage reaction process include at least: the stirring current reaching a preset value. The inventors have found that, under this preferred embodiment, the esterification reaction product exhibits better polycondensation effect, improving the structural and performance stability of the polyester.

[0061] It should be noted that the preset value of the stirring current in this invention is the rated current value of the reactor used. Different reactors have different rated current values.

[0062] According to the present invention, before reaching the polycondensation reaction conditions, the reaction system needs to be gradually heated, and the heating rate can be 0.2-1.4℃ / min.

[0063] A third aspect of the present invention provides a nonwoven fabric prepared using the polyester described in the first aspect and / or the polyester prepared by the preparation method described in the second aspect.

[0064] In this invention, the nonwoven fabric can be obtained from polyester using conventional preparation methods. Specifically, the preparation process of the nonwoven fabric includes: preparing polyester into polyester fibers, and then performing opening, web laying, needle punching, and hot rolling to obtain the nonwoven fabric.

[0065] According to the present invention, the above-mentioned nonwoven fabric has a thickness of 0.5 mm and a density of 200 g / m³. 2 Preferably, the nonwoven fabric has a transverse breaking strength > 63 N / 5 cm and a longitudinal breaking strength > 70 N / 5 cm; the nonwoven fabric has a transverse breaking elongation > 150% and a longitudinal breaking elongation > 105%.

[0066] According to the present invention, the above-mentioned nonwoven fabric has a thickness of 0.5 mm and a density of 200 g / m³. 2 Preferably, the elastic recovery rate of the nonwoven fabric under 50% strain conditions is >84%.

[0067] This invention is based on GB / T3923.1-2013 Textiles - Tensile Properties of Fabrics - Part 1: Determination of Breaking Strength and Elongation at Break, and tests the elastic recovery rate of nonwoven fabrics under a certain load.

[0068] In this invention, the aforementioned nonwoven fabric, while possessing a low melting point, also exhibits a high heat distortion temperature, good heat resistance, and excellent strength and resilience. It has significant applications in the manufacture of squeeze rollers; when the squeeze roller is in close contact with the metal sheet / strip, it achieves a superior squeezing effect, effectively solving the problem of slippage in the metal sheet / strip.

[0069] According to a particularly preferred embodiment of the present invention, a method for preparing a nonwoven fabric is provided, comprising the following steps:

[0070] (1) After mixing the dicarboxylic acid monomer, diol monomer, modified monomer and catalyst, carry out the esterification reaction under nitrogen atmosphere, temperature of 230-250℃ and pressure of 0.18-0.22MPa until the water content in the esterification product is not less than 90% of the theoretical water content.

[0071] The modified monomer contains isophthalic acid and a compound of formula (III);

[0072]

[0073] Wherein, x is an integer from 3 to 9; the diacid monomer is terephthalic acid, and the diol monomer is propylene glycol; the weight ratio of isophthalic acid to the compound shown in formula (III) is 0.4-8:1; the weight ratio of the diacid monomer, the diol monomer, and the modified monomer is 0.5-1.2:1:0.2-0.8; the catalyst is antimony glycolate and / or tetrabutyl titanate; the weight of the catalyst is 0.5-1.5g relative to 1000g of the diacid monomer;

[0074] (2) Reduce the pressure and heat the product of the esterification reaction in step (1) for 45 minutes to make its temperature 240-260℃ and vacuum pressure less than 100Pa, and enter the high vacuum polycondensation stage. When the stirring current reaches the rated current value, the product is discharged to obtain polyester.

[0075] (3) After the polyester obtained in step (2) is prepared into polyester fiber, it is then processed by opening, web laying, needle punching and hot rolling to obtain nonwoven fabric.

[0076] In the above preferred embodiments, the prepared nonwoven fabric has a low melting point, can improve its heat distortion temperature, has good heat resistance, and also has good strength and resilience, which has significant market prospects and environmental benefits.

[0077] The present invention will be described in detail below with reference to embodiments, but this does not limit the scope of the invention.

[0078] In the following examples and comparative examples, all raw materials used were commercially available.

[0079] The melting point was tested using a differential scanning calorimeter.

[0080] The heat distortion temperature was tested on the sample with a load of 0.45 MPa in accordance with GB / T1634.2-2004 Determination of Deflection Temperature under Load Part 2: Plastics, Hard Rubber and Long Fiber Reinforced Composites.

[0081] The viscosity was tested in accordance with GB / T14189-2008 Fiber Grade Polyester Chips.

[0082] The transverse breaking strength, longitudinal breaking strength, transverse breaking elongation, longitudinal breaking elongation and elastic recovery rate were tested in accordance with GB / T3923.1-2013 Textiles - Tensile Properties of Fabrics - Part 1: Determination of Breaking Strength and Elongation at Break.

[0083] Example 1

[0084] In a 20L polymerization reactor, 4.38 kg of terephthalic acid, 4.12 kg of 1,3-propanediol, 0.62 kg of isophthalic acid, 558 g of the compound shown in formula (III) (x is 6), 3.32 g of antimony glycolate, and 2.12 g of tetrabutyl titanate were added as raw materials and stirred into a uniform slurry. The slurry was then added to a reaction vessel for esterification. The esterification reaction was carried out under pressure in a nitrogen atmosphere, with the pressure controlled at 0.18 MPa and the temperature controlled at 250℃. The esterification reaction was considered to have ended when the amount of water distilled out reached more than 90% of the theoretical value. After the esterification reaction was completed, the temperature was gradually increased to enter a low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage was entered (vacuum pressure less than 100 Pa) and the polycondensation temperature was 260℃. The material was discharged when the stirring current of the reaction vessel reached the set value, and polyester was obtained. After the polyester was prepared into polyester fibers, it was opened, laid, needle-punched, and hot-rolled to prepare nonwoven fabric.

[0085] Example 2

[0086] In a 20L polymerization reactor, 3.88 kg of terephthalic acid, 4.12 kg of 1,3-propanediol, 1.12 kg of isophthalic acid, 248 g of the compound shown in formula (III) (x = 3), 1.62 g of antimony glycolate, and 1.32 g of tetrabutyl titanate were added as raw materials and stirred into a uniform slurry. This slurry was then added to a reaction vessel for esterification. The esterification reaction was carried out under pressure in a nitrogen atmosphere, with the pressure controlled at 0.2 MPa and the temperature controlled at 240℃. The esterification reaction was considered to have ended when the amount of water distilled out reached more than 90% of the theoretical value. After the esterification reaction was completed, the temperature was gradually increased to enter a low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage was entered, with the vacuum pressure less than 100 Pa and the polycondensation temperature at 255℃. The material was discharged when the stirring current of the reaction vessel reached the set value, and polyester was obtained. After the polyester was prepared into polyester fibers, it was opened, laid, needle-punched, and hot-rolled to prepare nonwoven fabric.

[0087] Example 3

[0088] In a 20L polymerization reactor, 2.52 kg of terephthalic acid, 4.12 kg of 1,3-propanediol, 2.48 kg of isophthalic acid, 310 g of the compound shown in formula (III) (x = 3), 1.62 g of antimony glycolate, and 1.32 g of tetrabutyl titanate were added as raw materials and stirred into a uniform slurry. This slurry was then added to a reaction vessel for esterification. The esterification reaction was carried out under pressure in a nitrogen atmosphere, with the pressure controlled at 0.2 MPa and the temperature controlled at 250°C. The esterification reaction was considered to have ended when the amount of water distilled out reached more than 90% of the theoretical value. After the esterification reaction was completed, the temperature was gradually increased to enter a low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage was entered, with a vacuum pressure of less than 100 Pa and a polycondensation temperature of 255°C. The material was discharged when the stirring current of the reaction vessel reached the set value, and polyester was obtained. After the polyester was prepared into polyester fibers, it was opened, laid, needle-punched, and hot-rolled to prepare nonwoven fabric.

[0089] Example 4

[0090] In a 20L polymerization reactor, 3.45 kg of terephthalic acid, 4.12 kg of 1,3-propanediol, 1.55 kg of isophthalic acid, 745 g of the compound shown in formula (III) (x = 3), 1.62 g of antimony glycolate, and 1.32 g of tetrabutyl titanate were added as raw materials and stirred into a uniform slurry. This slurry was then added to a reaction vessel for esterification. The esterification reaction was carried out under pressure in a nitrogen atmosphere, with the pressure controlled at 0.2 MPa and the temperature controlled at 240°C. The esterification reaction was considered to have ended when the amount of water distilled out reached more than 90% of the theoretical value. After the esterification reaction was completed, the temperature was gradually increased to enter a low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage was entered, with a vacuum pressure of less than 100 Pa and a polycondensation temperature of 250°C. The material was discharged when the stirring current of the reaction vessel reached the set value, and polyester was obtained. After the polyester was prepared into polyester fibers, it was opened, laid into a web, needle-punched, and hot-rolled to prepare nonwoven fabric.

[0091] Example 5

[0092] In a 20L polymerization reactor, 4.68 kg of terephthalic acid, 4.12 kg of 1,3-propanediol, 0.32 kg of isophthalic acid, 745 g of the compound shown in formula (III) (x = 3), 1.62 g of antimony glycolate, and 1.32 g of tetrabutyl titanate were added as raw materials and stirred into a uniform slurry. This slurry was then added to a reaction vessel for esterification. The esterification reaction was carried out under pressure in a nitrogen atmosphere, with the pressure controlled at 0.2 MPa and the temperature controlled at 250°C. The esterification reaction was considered to have reached the endpoint when the amount of water distilled out reached more than 90% of the theoretical value. After the esterification reaction was completed, the temperature was gradually increased to enter a low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage was entered, with the vacuum pressure less than 100 Pa and the polycondensation temperature at 260°C. The material was discharged when the stirring current of the reaction vessel reached the set value, and polyester was obtained. After the polyester was prepared into polyester fibers, it was opened, laid into a web, needle-punched, and hot-rolled to prepare nonwoven fabric.

[0093] Example 6

[0094] In a 20L polymerization reactor, 3.45 kg of terephthalic acid, 4.12 kg of 1,3-propanediol, 1.55 kg of isophthalic acid, 745 g of the compound shown in formula (III) (x = 3), 3.32 g of antimony glycolate, and 1.32 g of tetrabutyl titanate were added as raw materials and stirred into a uniform slurry. This slurry was then added to a reaction vessel for esterification. The esterification reaction was carried out under pressure in a nitrogen atmosphere, with the pressure controlled at 0.2 MPa and the temperature controlled at 240℃. The esterification reaction was considered to have ended when the amount of water distilled out reached more than 90% of the theoretical value. After the esterification reaction was completed, the temperature was gradually increased to enter a low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage was entered, with a vacuum pressure of less than 100 Pa and a polycondensation temperature of 255℃. The material was discharged when the stirring current of the reaction vessel reached the set value, and polyester was obtained. After the polyester was prepared into polyester fibers, it was opened, laid into a web, needle-punched, and hot-rolled to prepare nonwoven fabric.

[0095] Example 7

[0096] In a 20L polymerization reactor, 3.45 kg of terephthalic acid, 4.12 kg of 1,3-propanediol, 1.55 kg of isophthalic acid, 745 g of the compound shown in formula (III) (x is 3), and 2.94 g of antimony glycol were added as raw materials and stirred into a uniform slurry. This slurry was then added to a reaction vessel for esterification. The esterification reaction was carried out under pressure in a nitrogen atmosphere, with the pressure controlled at 0.2 MPa and the temperature controlled at 230℃. The esterification reaction was considered to have ended when the amount of water distilled out reached more than 90% of the theoretical value. After the esterification reaction was completed, the temperature was gradually increased to enter a low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage was entered, with the vacuum pressure less than 100 Pa and the polycondensation temperature at 240℃. The material was discharged when the stirring current of the reaction vessel reached the set value, and polyester was obtained. After the polyester was prepared into polyester fibers, it was opened, laid into a web, needle-punched, and hot-rolled to prepare nonwoven fabric.

[0097] Example 8

[0098] In a 20L polymerization reactor, 3.76 kg of terephthalic acid, 4.12 kg of 1,3-propanediol, 1.24 kg of isophthalic acid, 62 g of the compound shown in formula (III) (x = 3), 1.62 g of antimony glycolate, and 1.32 g of tetrabutyl titanate were added as raw materials and stirred into a uniform slurry. This slurry was then added to a reaction vessel for esterification. The esterification reaction was carried out under pressure in a nitrogen atmosphere, with the pressure controlled at 0.2 MPa and the temperature controlled at 240℃. The esterification reaction was considered to have ended when the amount of water distilled out reached more than 90% of the theoretical value. After the esterification reaction was completed, the temperature was gradually increased to enter a low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage was entered, with a vacuum pressure of less than 100 Pa and a polycondensation temperature of 255℃. The product was discharged when the stirring current of the reaction vessel reached the set value, and polyester was obtained. After the polyester was prepared into polyester fibers, it was processed by opening, web laying, needle punching, and hot rolling to obtain nonwoven fabric.

[0099] Example 9

[0100] In a 20L polymerization reactor, 2.83 kg of terephthalic acid, 4.12 kg of 1,3-propanediol, 2.17 kg of isophthalic acid, 186 g of the compound shown in formula (III) (x = 9), 1.12 g of antimony glycolate, and 1.12 g of tetrabutyl titanate were added as raw materials and stirred into a uniform slurry. This slurry was then added to a reaction vessel for esterification. The esterification reaction was carried out under pressure in a nitrogen atmosphere, with the pressure controlled at 0.22 MPa and the temperature controlled at 240°C. The esterification reaction was considered to have ended when the amount of water distilled out reached more than 90% of the theoretical value. After the esterification reaction was completed, the temperature was gradually increased to enter a low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage was entered, with a vacuum pressure of less than 100 Pa and a polycondensation temperature of 260°C. The material was discharged when the stirring current of the reaction vessel reached the set value, and polyester was obtained. After the polyester was prepared into polyester fibers, it was opened, laid into a web, needle-punched, and hot-rolled to prepare nonwoven fabric.

[0101] Example 10

[0102] In a 20L polymerization reactor, 4.38 kg of 4,4-biphenyl dicarboxylic acid, 4.12 kg of ethylene glycol, 0.62 kg of isophthalic acid, 558 g of the compound shown in formula (III) (x = 6), 3.32 g of antimony glycolate, and 2.12 g of tetrabutyl titanate were added as raw materials and stirred into a uniform slurry. This slurry was then added to a reaction vessel for esterification. The esterification reaction was carried out under pressure in a nitrogen atmosphere, with the pressure controlled at 0.18 MPa and the temperature controlled at 250°C. The esterification reaction was considered to have ended when the amount of water distilled out reached more than 90% of the theoretical value. After the esterification reaction was completed, the temperature was gradually increased to enter a low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage was entered (vacuum pressure less than 100 Pa) and the polycondensation temperature was 255°C. The material was discharged when the stirring current of the reaction vessel reached the set value, and polyester was obtained. After the polyester was prepared into polyester fibers, it was opened, laid, needle-punched, and hot-rolled to prepare nonwoven fabric.

[0103] Comparative Example 1

[0104] 5 kg of terephthalic acid, 4.12 kg of 1,3-propanediol, 558 g of the compound shown in formula (III) (x is 6), 3.32 g of antimony glycolate, and 2.12 g of tetrabutyl titanate were added to a 20 L polymerization reactor and stirred into a uniform slurry. The slurry was then added to a reaction vessel for esterification. The esterification reaction was carried out under pressure in a nitrogen atmosphere, with the pressure controlled at 0.18 MPa and the temperature controlled at 245 °C. The esterification reaction was considered to have ended when the amount of water distilled out reached more than 90% of the theoretical value. After the esterification reaction was completed, the temperature was gradually increased to enter a low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage was entered (vacuum pressure less than 100 Pa) and the polycondensation temperature was 255 °C. The product was discharged when the stirring current of the reaction vessel reached the set value, and polyester was obtained. After the polyester was prepared into polyester fibers, it was opened, laid, needle-punched, and hot-rolled to prepare nonwoven fabric.

[0105] Comparative Example 2

[0106] In a 20L polymerization reactor, 3.76 kg of terephthalic acid, 4.12 kg of 1,3-propanediol, 1.24 kg of isophthalic acid, 1.62 g of antimony glycolate, and 1.32 g of tetrabutyl titanate were added as raw materials and stirred into a uniform slurry. This slurry was then added to a reaction vessel for esterification. The esterification reaction was carried out under pressure in a nitrogen atmosphere, with the pressure controlled at 0.2 MPa and the temperature controlled at 230℃. The esterification reaction was considered to have ended when the amount of water distilled out reached more than 90% of the theoretical value. After the esterification reaction was completed, the temperature was gradually increased to enter a low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage was entered, with the vacuum pressure less than 100 Pa and the polycondensation temperature at 260℃. The material was discharged when the stirring current of the reaction vessel reached the set value, and polyester was obtained. After the polyester was prepared into polyester fibers, it was opened, laid into a web, needle-punched, and hot-rolled to prepare nonwoven fabric.

[0107] Comparative Example 3

[0108] 5 kg of terephthalic acid, 4.12 kg of 1,3-propanediol, 1.62 g of antimony glycol, and 1.32 g of tetrabutyl titanate were added to a 20 L polymerization reactor and stirred into a uniform slurry. This slurry was then added to a reaction vessel for esterification. The esterification reaction was carried out under pressure in a nitrogen atmosphere, with the pressure controlled at 0.2 MPa and the temperature at 230 °C. The esterification reaction was considered complete when the amount of water distilled out reached more than 90% of the theoretical value. After the esterification reaction, the temperature was gradually increased to enter a low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage was entered, with a vacuum pressure of less than 100 Pa and a polycondensation temperature of 255 °C. The material was discharged when the stirring current of the reaction vessel reached the set value, and polyester was obtained. After the polyester was prepared into polyester fibers, it was opened, laid into a web, needle-punched, and hot-rolled to prepare nonwoven fabric.

[0109] Test Example 1

[0110] The polyesters prepared in Examples 1-10 and Comparative Examples 1-3 were tested for the content of structural unit (A), structural unit (B), antimony and titanium. The content of structural unit (A) and structural unit (B) was tested by gas chromatography, and the content of antimony and titanium was tested by inductively coupled plasma (ICP) spectrometry. The results are shown in Table 1.

[0111] Table 1

[0112]

[0113]

[0114] Test Example 2

[0115] The viscosity, melting point and heat distortion temperature of the polyesters prepared in Examples 1-10 and Comparative Examples 1-3 were measured, and the results are shown in Table 2.

[0116] Table 2

[0117] Example 1 0.854 198 75 Example 2 0.899 188 62 Example 3 0.917 158 66 Example 4 0.903 173 78 Example 5 0.925 200 70 Example 6 0.810 169 74 Example 7 0.922 172 72 Example 8 0.878 181 48 Example 9 0.921 165 55 Example 10 0.915 205 60 Comparative Example 1 0.889 218 66 Comparative Example 2 0.869 189 43 Comparative Example 3 0.902 220 40

[0118] As can be seen from the results in Table 2, compared with Comparative Examples 1-3, the polyesters prepared in Examples 1-10 have a low melting point and can improve their heat distortion temperature, thus exhibiting good heat resistance.

[0119] Test Example 3

[0120] Commercially available polypropylene nonwoven fabric, as well as the nonwoven fabrics prepared in Examples 1-10 and Comparative Examples 1-3, were made into fabrics with a thickness of 0.5 mm and a density of 200 g / m³. 2The samples were tested, and the strength and elastic recovery rate of the samples were tested. The results are shown in Table 3.

[0121] Table 3

[0122]

[0123] As can be seen from the results in Table 3, the nonwoven fabrics prepared in Examples 1-10 have good strength and resilience compared to polypropylene nonwoven fabrics.

[0124] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A polyester, characterized in that, The polyester has a melting point of 158-205℃ and a heat distortion temperature of 48-78℃ under a pressure of 0.45MPa. The polyester contains structural unit (A) as shown in formula (I) and structural unit (B) as shown in formula (II); Equation (I); Formula (II); Wherein, n is an integer from 4 to 10, and R1, R2, R3, and R4 are each independently selected from hydrogen or C1-C4 alkyl groups; in the polyester, the content of the structural unit (A) is 1-12% by weight, and the content of the structural unit (B) is 5-40% by weight. The polyester contains 0.01-0.04% by weight of a metal element, wherein the metal element is antimony and / or titanium.

2. The polyester according to claim 1, characterized in that, The polyester has a melting point of 169-200℃ and a heat distortion temperature of 62-78℃ under a pressure of 0.45MPa. The viscosity of the polyester is 0.7-1.0 dL / g.

3. A method for preparing polyester as described in claim 1 or 2, characterized in that, The method includes the following steps: (1) Under esterification reaction conditions, diacid monomers, diol monomers, modified monomers and catalysts are mixed to carry out the first stage reaction to obtain prepolymers; The modified monomer contains a monomer having the structure shown in formula (I) and a monomer having the structure shown in formula (II); Equation (I); Formula (II); Where n is an integer from 4 to 10, and R1, R2, R3 and R4 are each independently selected from hydrogen or C1-C4 alkyl groups; (2) Under polycondensation reaction conditions, the prepolymer is subjected to a second-stage reaction; The weight ratio of the monomer having the structure shown in formula (II) to the monomer having the structure shown in formula (I) is 0.4-8:1; the weight ratio of the dicarboxylic acid monomer, the diol monomer and the modified monomer is 0.5-1.2:1:0.2-0.8; the catalyst contains an antimony-based catalyst and / or a titanium-based catalyst.

4. The preparation method according to claim 3, characterized in that, The monomer having the structure shown in formula (II) is isophthalic acid, and the dicarboxylic acid monomer is an aromatic dicarboxylic acid and is different from the monomer having the structure shown in formula (II).

5. The preparation method according to claim 4, characterized in that, The dicarboxylic acid monomer is selected from at least one of terephthalic acid, 4,4'-biphenyl dicarboxylic acid, and 2,6-naphthalenedicarboxylic acid.

6. The preparation method according to claim 5, characterized in that, The diol monomer is ethylene glycol and / or propylene glycol.

7. The preparation method according to claim 6, characterized in that, The diol monomer is propylene glycol.

8. The preparation method according to claim 3, characterized in that, The antimony-based catalyst is selected from at least one of antimony glycolate, antimony trioxide, and antimony acetate; the titanium-based catalyst is tetrabutyl titanate and / or titanium glycolate.

9. The preparation method according to claim 8, characterized in that, The antimony-based catalyst is antimony glycolate, and the titanium-based catalyst is tetrabutyl titanate.

10. The preparation method according to any one of claims 3 to 9, characterized in that, In step (1), the conditions for the esterification reaction include at least: a temperature of 230-250℃ and a pressure of 0.18-0.22MPa; In step (2), the conditions for the polycondensation reaction include at least the following: temperature of 240-260℃ and vacuum pressure of less than 100Pa.

11. A nonwoven fabric, characterized in that, The polyester is prepared by using the polyester according to claim 1 or 2 and / or the preparation method according to any one of claims 3 to 10.

12. The nonwoven fabric according to claim 11, characterized in that, The nonwoven fabric has a transverse tensile strength > 63 N / 5 cm and a longitudinal tensile strength > 70 N / 5 cm; the nonwoven fabric has a transverse elongation at break > 150% and a longitudinal elongation at break > 105%. The nonwoven fabric exhibits an elastic recovery rate of >84% under 50% strain conditions.

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