A polyester and a method for producing the same

Abstract

This invention belongs to the field of polyester preparation technology, and relates to a polyester and its preparation method. The polyester is prepared by reacting a diacid, a diol, and a metal dicarboxylate; the structural formula of the metal dicarboxylate is: HOOC-R1-COO-M 2+ -COO-R2-COOH, where -R1- and -R2- are both chain segments composed of carbon and hydrogen atoms, and the number of carbon atoms in -R1- and -R2- is 1-8. The number of carbon atoms in -R1- and -R2- may be the same or different. M 2+ For Be 2+ Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ Ra 2+ Fe 2+ Zn 2+ or Co 2+ Preparation method: Dicarboxylic acid, diol, and metal dicarboxylate are used as reactants to undergo esterification and polycondensation reactions to obtain polyester. This invention solves the problem of rapid increase in melt viscosity and easy burst polymerization caused by side-chain ionic groups during the polycondensation reaction of traditional cationic polyesters.

Description

Technical Field

[0001] This invention belongs to the field of polyester preparation technology, and relates to a polyester and its preparation method. Background Technology

[0002] Polyesters, especially semi-aromatic polyesters with polyethylene terephthalate (PET), polypropylene terephthalate (PTT) and polybutylene terephthalate (PBT) as the main components, have been widely used in the fiber industry due to their excellent comprehensive properties.

[0003] To improve the dyeability of these polyesters, existing technologies (such as patent application CN110776629A) commonly employ copolymerization modification by adding 0.5-5 wt% of sodium isophthalate sulfonate (SIPA) or its dimethyl phthalate (SIPM), thereby obtaining cationic dyeable polyester (CDP). However, the introduction of SIPA or SIPM introduces ionic groups into the polymer side chains. This structural change leads to a sharp increase in melt viscosity during the polycondensation reaction, resulting in problems such as polymer sticking and high gel content. In severe cases, it can even cause the agitator to seize up, i.e., "bursting polymerization." Polyester chips obtained after bursting polymerization often experience problems such as clogging of filter components and filament breakage during subsequent spinning, adversely affecting production efficiency and product quality. Summary of the Invention

[0004] The purpose of this invention is to solve the problems existing in the prior art and to provide a polyester and a method for preparing the same.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A polyester is prepared by reacting a diacid, a diol, and a metal dicarboxylate. The mass of the metal dicarboxylate is less than 1 / 10 of the mass of the diacid. If the amount of metal dicarboxylate used is too high, there is still a risk of explosive polymerization.

[0007] The structural formula of the metal dicarboxylate is: HOOC-R1-COO-M 2+ -COO-R2-COOH, where -R1- and -R2- are both chain segments composed of carbon and hydrogen atoms, and the number of carbon atoms in -R1- and -R2- is 1-8. The number of carbon atoms in -R1- and -R2- may be the same or different. M 2+ It can be Be²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Ra²⁺, Fe²⁺, Zn²⁺, or Co²⁺.

[0008] This invention addresses the problems of existing technologies by altering the form in which ionic groups exist within polyester molecules. The polyester of this invention is prepared by reacting a diacid, a diol, and a specific metal dicarboxylate. The ionic groups contained in this metal dicarboxylate enter the main chain of the polyester molecule during the reaction, rather than the side chains, thus avoiding abnormal changes in melt viscosity caused by side-chain ionic groups.

[0009] As a preferred technical solution:

[0010] In the polyester described above, the mass of the metal dicarboxylate is more than 1 / 200 of the mass of the dicarboxylic acid. If the amount of metal dicarboxylate used is too low, the improvement in dyeability is limited.

[0011] In the polyester described above, HOOC-R1-COO- and -COO-R2-COOH are oxalic acid segments, malonic acid segments, succinic acid segments, glutaric acid segments, adipic acid segments, heptanoic acid segments, octanoic acid segments, cyclohexanedicarboxylic acid segments, terephthalic acid segments, isophthalic acid segments, or phthalic acid segments.

[0012] As described above, the metal dicarboxylate is magnesium dimalonate, zinc dimalonate, calcium dimalonate, magnesium disuccinate, calcium disuccinate, zinc disuccinate, magnesium adipate, calcium adipate, zinc adipate, calcium isophthalate, zinc isophthalate, magnesium isophthalate, calcium terephthalate, magnesium terephthalate, or zinc terephthalate.

[0013] In one of the polyesters described above, the dicarboxylic acid is terephthalic acid, isophthalic acid, succinic acid, or adipic acid.

[0014] In one of the polyesters described above, the diol is ethylene glycol, 1,3-propanediol, 1,4-butanediol, or neopentyl glycol.

[0015] In one of the polyesters described above, the molar ratio of diol to diacid is 1.1-2.0:1.

[0016] The present invention also provides a method for preparing a polyester as described in any of the preceding claims, wherein a dicarboxylic acid, a diol, and a metal dicarboxylate are used as reactants, and an esterification reaction and a polycondensation reaction are carried out sequentially to obtain the polyester.

[0017] As a preferred technical solution:

[0018] As described above, a catalyst is added before the esterification reaction. The catalyst is one or more of antimony trioxide, antimony glycolate, germanium dioxide, tetrabutyl titanate, and tetraisopropyl titanate. The amount of catalyst used is 50-1000 ppm of the theoretical yield of polyester. After the esterification reaction and before the polycondensation reaction, a stabilizer is added. The stabilizer is one or more of triphenyl phosphate, tributyl phosphate, triphenyl phosphite, antioxidant 1010, and antioxidant 245. The amount of stabilizer used is 50-3000 ppm of the theoretical yield of polyester.

[0019] The specific steps of the method described above are as follows:

[0020] (a) After mixing the dicarboxylic acid, diol, metal dicarboxylate, and catalyst, the mixture is subjected to esterification under nitrogen or inert atmosphere at a temperature of 190-270℃ and a pressure of 0-0.5MPa until the esterification rate reaches more than 95%. Then the pressure is released to atmospheric pressure to end the esterification process.

[0021] (b) After adding a stabilizer to the reaction system, gradually reduce the pressure and increase the temperature of the reaction system to 230-290℃ and ≤100Pa, and then carry out the polycondensation reaction for more than 80 minutes to obtain polyester.

[0022] The principle of this invention is as follows:

[0023] In existing technologies, when SIPA or SIPM is copolymerized with polyester, ionic groups are introduced into the polymer side chains. These ionic groups readily interact to form ionic clusters (i.e., stable structural units formed by the aggregation of multiple ions through electrostatic interactions). Through in-depth investigation, this invention has discovered that the ionic clusters formed by the side chain ionic groups are the key factor leading to an abnormal increase in melt viscosity and triggering explosive polymerization.

[0024] During polycondensation, the formation of ion clusters leads to a sharp increase in melt viscosity. The core mechanism lies in the strong constraint effect of these ion clusters on the movement of molecular chains as dynamic physical cross-linking points: ion groups and counterions aggregate through electrostatic interactions to form nanoscale ion clusters. These cluster structures fix the ion groups on the molecular chains through electrostatic attraction, forming local confinement regions that restrict the rotation and translation of chain segments, requiring the molecular chains to overcome higher energy barriers to undergo conformational changes. At the same time, the aggregation of ion clusters leads to the formation of multi-chain entanglement networks, complicating the topological structure and making it difficult for molecular chains to slip and untangle, further hindering fluid flow. Under shear or stretching, the dynamic equilibrium of depolymerization and recombination of ion clusters is broken, and the cluster structure persists and increases in size, forming a large number of "ion cluster-molecular chain complexes," significantly increasing energy dissipation and flow resistance, ultimately leading to a sharp increase in melt viscosity. This, in turn, causes polymer climbing, high gel content, and in severe cases, stirrer seizure (i.e., "explosive polymerization"). Furthermore, the polyester chips obtained after explosive polymerization are prone to problems such as clogging of filter components and fiber breakage during subsequent spinning.

[0025] This invention selects a metal dicarboxylate with a specific structure, and uses it together with a diacid and a diol as reactants to carry out esterification and polycondensation reactions to prepare polyester. During the reaction, the ionic groups contained in the metal dicarboxylate enter the main chain of the polyester molecule. The main chain ionic groups of adjacent molecular chains are "separated" by the main chain backbone segments on both sides and the rigid structure of the main chain itself, and cannot freely approach each other. The steric hindrance directly blocks the "physical path" of ion aggregation through electrostatic interaction, thereby reducing the formation of ion clusters from the root. This effectively solves the problem of the rapid increase in melt viscosity and easy bursting of polymerization caused by the side chain ionic groups during the polycondensation reaction of traditional cationic polyesters. At the same time, it ensures that the final polyester has good spinnability in the subsequent melt spinning process and reduces the phenomenon of yarn breakage.

[0026] Beneficial effects:

[0027] This invention introduces ionic groups into the polymer backbone by reacting a metal dicarboxylate with a specific structure and a dicarboxylic acid or diol. This effectively solves the problem of rapid increase in melt viscosity and easy explosive polymerization caused by the formation of ionic clusters by side chain ionic groups in traditional cationic polyesters. Attached Figure Description

[0028] Figure 1 This is the 1H NMR spectrum of the polyester in Example 8 of the present invention. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0030] The following are the test methods for relevant performance indicators in each embodiment, comparative example, and control group:

[0031] Polycondensation reaction time: When the polycondensation temperature reaches the process set temperature and the absolute pressure inside the polymerization reactor is ≤100Pa, the timing starts; the stirring speed is set to 40rpm, and the timing stops when the stirring power display reaches the set value (300W). This time period is the polycondensation reaction time.

[0032] Number of fiber breaks during melt spinning of polyester: Using a spinning machine (Abe Corporation, Japan, ABE Φ25×2 type), the spinning temperature (290℃) was set according to the specific requirements of the finished product, the winding speed was fixed at 800m / min, and the other process parameters were referenced to the conventional polyester spinning conditions. The polyester product to be tested was melt spun and run stably, and the number of fiber breaks per hour was counted.

[0033] Example 1

[0034] A method for preparing polyester, comprising the following specific steps:

[0035] (1) Preparation of materials;

[0036] Dicarboxylic acid: terephthalic acid;

[0037] Diol: Ethylene glycol;

[0038] Metal dicarboxylate: Zinc diisophthalate;

[0039] Catalyst: Antimony glycol;

[0040] Stabilizer: Triphenyl phosphate;

[0041] (2) Preparation of polyester;

[0042] (a) After mixing the dicarboxylic acid, diol, metal dicarboxylate, and catalyst, the esterification reaction is carried out under nitrogen or inert atmosphere at a temperature of 240°C and a pressure of 0.2 MPa (with stirring at a stirring speed of 40 rpm) until the esterification rate reaches 95%. Then, the pressure is released to atmospheric pressure to end the esterification.

[0043] (b) After adding a stabilizer to the reaction system, the reaction system is gradually depressurized and heated to a temperature of 280°C and an absolute pressure of ≤100Pa, and then polycondensation reaction is carried out for 170 minutes to obtain polyester.

[0044] In steps (a) to (b), the mass of the dicarboxylic acid is 200 times the mass of the metal dicarboxylate, the molar ratio of the diol to the dicarboxylic acid is 1.5:1, the amount of catalyst used is 250 ppm of the theoretical yield of polyester, and the amount of stabilizer used is 300 ppm of the theoretical yield of polyester.

[0045] Tests showed that the final polyester produced had 0 yarn breaks per hour during melt spinning.

[0046] Control group 1

[0047] A method for preparing polyester differs from Example 1 in that: no metal dicarboxylate is added; and the polycondensation reaction time is 180 min.

[0048] Tests showed that the final polyester produced had 0 yarn breaks per hour during melt spinning.

[0049] Comparing Example 1 and Control Group 1, it can be seen that the final products of both had 0 yarn breaks per hour during melt spinning, indicating comparable spinnability. In Example 1, the addition of a metal dicarboxylate resulted in a polycondensation reaction time of 170 min, which is close to the 180 min polycondensation time of Control Group 1 without the metal dicarboxylate. This suggests that the introduction of the metal dicarboxylate did not significantly interfere with the polyester polycondensation process, and the overall performance was essentially the same as that of the normally prepared polyester (Control Group 1), achieving process stability and processing effects close to those of conventional polyester.

[0050] Comparative Example 1

[0051] A method for preparing polyester differs from Example 1 in that: the metal dicarboxylate is replaced with sodium isophthalate sulfonate; and the polycondensation reaction time is 120 min.

[0052] Tests showed that the final polyester produced had a breakage rate of 4 times per hour during melt spinning.

[0053] Comparative Example 2

[0054] A method for preparing polyester differs from Example 1 in that: the metal dicarboxylate is replaced with sodium isophthalate sulfonate, the mass of the dicarboxylic acid is 20 times the mass of sodium isophthalate sulfonate, and the polycondensation reaction time is 65 min.

[0055] Tests showed that the final polyester produced had a breakage rate of 9 times per hour during melt spinning.

[0056] Comparative Example 3

[0057] A method for preparing polyester differs from Example 1 in that: the metal dicarboxylate is replaced with sodium isophthalate sulfonate, the mass of the dicarboxylic acid is 10 times the mass of sodium isophthalate sulfonate, and the polycondensation reaction time is 45 min.

[0058] Tests showed that the final polyester produced had a breakage rate of 17 times per hour during melt spinning.

[0059] Compared with Example 1, the spinnability of the final products in Comparative Examples 1-3 was significantly worse, and the polycondensation reaction time was significantly shortened. This is because the sodium isophthalate sulfonate used in Comparative Examples 1-3 causes metal ions to be located on the molecular side chain, resulting in a sharp increase in melt viscosity during high-vacuum polycondensation, an excessively fast reaction rate, and an increased risk of explosive polymerization. In contrast, the zinc diisophthalate used in this example, as a metal dicarboxylate, introduces ionic groups into the molecular backbone, making the vacuum polycondensation reaction rate more stable and effectively improving the explosive polymerization phenomenon. While ensuring spinnability, the polycondensation time is closer to the level of conventional polyester.

[0060] Example 2

[0061] A method for preparing polyester differs from Example 1 in that the amount of metal dicarboxylate added is adjusted, the mass of the dicarboxylic acid is 40 times the mass of the metal dicarboxylate, and the polycondensation reaction time is 125 min.

[0062] Tests showed that the final polyester produced had 0 yarn breaks per hour during melt spinning.

[0063] Example 3

[0064] A method for preparing polyester differs from Example 1 in that the amount of metal dicarboxylate added is adjusted, the mass of the dicarboxylic acid is 10 times the mass of the metal dicarboxylate, and the polycondensation reaction time is 90 min.

[0065] Tests showed that the final polyester produced had a breakage rate of 2 times per hour during melt spinning.

[0066] Example 4

[0067] A method for preparing polyester differs from Example 3 in that the metal dicarboxylate is zinc diadipate; and the polycondensation reaction time is 95 min.

[0068] Tests show that the final polyester has a breakage rate of 1 per hour during melt spinning.

[0069] Example 5

[0070] A method for preparing polyester differs from Example 3 in that: the metal dicarboxylate is calcium dimalonate; and the polycondensation reaction time is 92 min.

[0071] Tests showed that the final polyester produced had a breakage rate of 2 times per hour during melt spinning.

[0072] Example 6

[0073] A method for preparing polyester differs from Example 3 in that: the metal dicarboxylate is magnesium dimalonate; and the polycondensation reaction time is 94 min.

[0074] Tests show that the final polyester has a breakage rate of 1 per hour during melt spinning.

[0075] Example 7

[0076] A method for preparing polyester differs from Example 3 in that the metal dicarboxylate is magnesium disuccinate and the polycondensation reaction time is 97 min.

[0077] Tests show that the final polyester has a breakage rate of 1 per hour during melt spinning.

[0078] Example 8

[0079] A method for preparing polyester, comprising the following specific steps:

[0080] (1) Preparation of materials;

[0081] Dicarboxylic acid: terephthalic acid;

[0082] Diol: 1,4-Butanediol;

[0083] Metal dicarboxylate: Zinc diisophthalate;

[0084] Catalyst: Tetrabutyl titanate;

[0085] Stabilizer: Triphenyl phosphate;

[0086] (2) Preparation of polyester;

[0087] (a) After mixing the dicarboxylic acid, diol, metal dicarboxylate, and catalyst, the esterification reaction is carried out under nitrogen or inert atmosphere at a temperature of 220°C and a pressure of 0.3 MPa (with stirring at a stirring speed of 40 rpm) until the esterification rate reaches 95%. Then, the pressure is released to atmospheric pressure to end the esterification.

[0088] (b) After adding a stabilizer to the reaction system, the reaction system is gradually depressurized and heated to a temperature of 255°C and an absolute pressure of ≤100Pa, and then polycondensation reaction is carried out for 80 minutes to obtain polyester.

[0089] In steps (a) to (b), the mass of the dicarboxylic acid is 20 times the mass of the metal dicarboxylate, the molar ratio of the diol to the dicarboxylic acid is 1.5:1, the amount of catalyst used is 500 ppm of the theoretical yield of polyester, and the amount of stabilizer used is 300 ppm of the theoretical yield of polyester.

[0090] Tests show that the final polyester (NMR spectrum as shown in Figure 1) has the following properties: Figure 1 As shown, the number of yarn breaks during the melt spinning process is 1 per hour.

[0091] Control group 2

[0092] A method for preparing polyester differs from Example 8 in that: no metal dicarboxylate is added; and the polycondensation reaction time is 170 min.

[0093] Tests showed that the final polyester produced had 0 yarn breaks per hour during melt spinning.

[0094] Example 9

[0095] A method for preparing polyester differs from Example 8 in that the diol is 1,3-propanediol and the polycondensation reaction time is 95 min.

[0096] Tests show that the final polyester has a breakage rate of 1 per hour during melt spinning.

[0097] Control group 3

[0098] A method for preparing polyester differs from Example 9 in that: no metal dicarboxylate is added; and the polycondensation reaction time is 190 min.

[0099] Tests showed that the final polyester produced had 0 yarn breaks per hour during melt spinning.

[0100] Comparing Example 8 with Control Group 2 and Example 9 with Control Group 3, it can be seen that Example 8 and Example 9, due to the addition of a metal dicarboxylate (zinc diisophthalate), had polycondensation reaction times of 80 min and 95 min respectively, which are shorter than those of Control Group 2 (170 min) and Control Group 3 (190 min). However, the final product had only one breakage per hour during melt spinning, which is close to the spinnability of Control Groups 2 and 3. This indicates that even if the type of diol is changed (using 1,4-butanediol or 1,3-propanediol), the introduction of a metal dicarboxylate does not result in a sharp increase in melt viscosity due to side chain ionic groups as seen in the prior art. The reaction process remains relatively stable, and the risk of explosive polymerization is not significantly increased due to the shortened polycondensation time. The processing stability and spinnability of the final product are not significantly affected, and they can still meet actual processing requirements, confirming the applicability of the present invention in different diol systems.

[0101] Example 10

[0102] A method for preparing polyester, comprising the following specific steps:

[0103] (1) Preparation of materials;

[0104] Dicarboxylic acid: isophthalic acid;

[0105] Diol: Neopentyl glycol;

[0106] Metal dicarboxylate: calcium dimalonate;

[0107] Catalyst: Antimony trioxide;

[0108] Stabilizer: Tributyl phosphate;

[0109] (2) Preparation of polyester;

[0110] (a) After mixing the dicarboxylic acid, diol, metal dicarboxylate, and catalyst, the esterification reaction is carried out under nitrogen or inert atmosphere at a temperature of 190°C and a pressure of 0.5 MPa (with stirring at a stirring speed of 40 rpm) until the esterification rate reaches 97%. Then, the pressure is released to atmospheric pressure to end the esterification.

[0111] (b) After adding a stabilizer to the reaction system, the reaction system is gradually depressurized and heated to a temperature of 230°C and an absolute pressure of ≤100Pa, and then polycondensation reaction is carried out for 180 minutes to obtain polyester.

[0112] In steps (a) to (b), the mass of the dicarboxylic acid is 50 times the mass of the metal dicarboxylate, the molar ratio of the diol to the dicarboxylic acid is 1.1:1, the amount of catalyst used is 50 ppm of the theoretical yield of polyester, and the amount of stabilizer used is 50 ppm of the theoretical yield of polyester.

[0113] Tests show that the final polyester has a breakage rate of 1 per hour during melt spinning.

[0114] Example 11

[0115] A method for preparing polyester, comprising the following specific steps:

[0116] (1) Preparation of materials;

[0117] Dicarboxylic acid: adipic acid;

[0118] Diol: Ethylene glycol;

[0119] Metal dicarboxylate: calcium disuccinate;

[0120] Catalyst: Tetraisopropyl titanate;

[0121] Stabilizer: Triphenyl phosphite;

[0122] (2) Preparation of polyester;

[0123] (a) After mixing the dicarboxylic acid, diol, metal dicarboxylate, and catalyst, the esterification reaction is carried out under nitrogen or inert atmosphere at a temperature of 190°C and a pressure of 0 MPa (with stirring at a stirring speed of 40 rpm) until the esterification rate reaches 97%. Then, the pressure is released to atmospheric pressure to end the esterification.

[0124] (b) After adding a stabilizer to the reaction system, the reaction system is gradually depressurized and heated to a temperature of 240°C and an absolute pressure of ≤100Pa, and then polycondensation reaction is carried out for 190 minutes to obtain polyester.

[0125] In steps (a) to (b), the mass of the dicarboxylic acid is 50 times the mass of the metal dicarboxylate, the molar ratio of the diol to the dicarboxylic acid is 2.0:1, the amount of catalyst used is 1000 ppm of the theoretical yield of polyester, and the amount of stabilizer used is 3000 ppm of the theoretical yield of polyester.

[0126] Tests showed that the final polyester produced had 0 yarn breaks per hour during melt spinning.

[0127] Example 12

[0128] A method for preparing polyester, comprising the following specific steps:

[0129] (1) Preparation of materials;

[0130] Dicarboxylic acid: succinic acid;

[0131] Diol: 1,3-propanediol;

[0132] Metal dicarboxylate: magnesium diadipic acid;

[0133] Catalyst: Antimony glycol;

[0134] Stabilizer: Antioxidant 1010;

[0135] (2) Preparation of polyester;

[0136] (a) After mixing the dicarboxylic acid, diol, metal dicarboxylate, and catalyst, the esterification reaction is carried out under nitrogen or inert atmosphere at a temperature of 270°C and a pressure of 0.2 MPa (with stirring at a stirring speed of 40 rpm) until the esterification rate reaches 95%. Then, the pressure is released to atmospheric pressure to end the esterification.

[0137] (b) After adding a stabilizer to the reaction system, the reaction system is gradually depressurized and heated to a temperature of 260°C and an absolute pressure of ≤100Pa, and then polycondensation reaction is carried out for 170 minutes to obtain polyester.

[0138] In steps (a) to (b), the mass of the dicarboxylic acid is 80 times the mass of the metal dicarboxylate, the molar ratio of the diol to the dicarboxylic acid is 1.5:1, the amount of catalyst used is 500 ppm of the theoretical yield of polyester, and the amount of stabilizer used is 1500 ppm of the theoretical yield of polyester.

[0139] Tests showed that the final polyester produced had 0 yarn breaks per hour during melt spinning.

[0140] Example 13

[0141] A method for preparing polyester, comprising the following specific steps:

[0142] (1) Preparation of materials;

[0143] Dicarboxylic acid: succinic acid;

[0144] Diol: 1,3-propanediol;

[0145] Metal dicarboxylate: calcium diadipic acid;

[0146] Catalyst: Antimony glycol;

[0147] Stabilizer: Antioxidant 245;

[0148] (2) Preparation of polyester;

[0149] (a) After mixing the dicarboxylic acid, diol, metal dicarboxylate, and catalyst, the esterification reaction is carried out under nitrogen or inert atmosphere at a temperature of 200°C and a pressure of 0 MPa (with stirring at a stirring speed of 40 rpm) until the esterification rate reaches 98%. Then, the pressure is released to atmospheric pressure to end the esterification.

[0150] (b) After adding a stabilizer to the reaction system, the reaction system is gradually depressurized and heated to a temperature of 260°C and an absolute pressure of ≤100Pa, and then polycondensation reaction is carried out for 200 minutes to obtain polyester.

[0151] In steps (a) to (b), the mass of the dicarboxylic acid is 80 times the mass of the metal dicarboxylate, the molar ratio of the diol to the dicarboxylic acid is 1.5:1, the amount of catalyst used is 500 ppm of the theoretical yield of polyester, and the amount of stabilizer used is 1500 ppm of the theoretical yield of polyester.

[0152] Tests show that the final polyester has a breakage rate of 1 per hour during melt spinning.

[0153] In all the above embodiments and comparative examples, the pressure reduction was stopped when the pressure of the reaction system during the polycondensation reaction was lower than 100 Pa.

Claims

1. A polyester, characterized in that, It is prepared by reacting a dicarboxylic acid, a diol, and a metal dicarboxylate, wherein the mass of the metal dicarboxylate is 1 / 200-1 / 10 of the mass of the dicarboxylic acid, and the molar ratio of the diol to the dicarboxylic acid is 1.1-2.0:

1. The structural formula of the metal dicarboxylate is: HOOC-R1-COO-M 2+ -COO-R2-COOH, where -R1- and -R2- are both chain segments composed of carbon and hydrogen atoms, and the number of carbon atoms in -R1- and -R2- is 1-8, with -R1- and -R2- having the same number of carbon atoms. M 2+ Mg 2+ Ca 2+ or Zn 2+ .

2. The polyester according to claim 1, characterized in that, HOOC-R1-COO- and -COO-R2-COOH are oxalic acid segments, malonic acid segments, succinic acid segments, glutaric acid segments, adipic acid segments, hematonic acid segments, octanoic acid segments, cyclohexanedicarboxylic acid segments, terephthalic acid segments, isophthalic acid segments, or phthalic acid segments.

3. A polyester according to claim 2, characterized in that, The metal dicarboxylate salts are magnesium dimalonate, zinc dimalonate, calcium dimalonate, magnesium disuccinate, calcium disuccinate, zinc disuccinate, magnesium diadhesive, calcium diadhesive, zinc diadhesive, calcium isophthalate, zinc isophthalate, magnesium isophthalate, calcium terephthalate, magnesium terephthalate, or zinc terephthalate.

4. A polyester according to claim 1, characterized in that, The dicarboxylic acid is terephthalic acid, isophthalic acid, succinic acid, or adipic acid.

5. A polyester according to claim 1, characterized in that, The diol is ethylene glycol, 1,3-propanediol, 1,4-butanediol, or neopentyl glycol.

6. A method for preparing a polyester according to any one of claims 1 to 5, characterized in that, Polyester is obtained by sequentially carrying out esterification and polycondensation reactions using dicarboxylic acid, diol, and metal dicarboxylate as reactants.

7. The method according to claim 6, characterized in that, A catalyst is added before the esterification reaction. The catalyst is one or more of antimony trioxide, antimony glycolate, germanium dioxide, tetrabutyl titanate, and tetraisopropyl titanate. The amount of catalyst used is 50-1000 ppm of the theoretical yield of polyester. A stabilizer is added after the esterification reaction and before the polycondensation reaction. The stabilizer is one or more of triphenyl phosphate, tributyl phosphate, triphenyl phosphite, antioxidant 1010, and antioxidant 245. The amount of stabilizer used is 50-3000 ppm of the theoretical yield of polyester.

8. The method according to claim 7, characterized in that, The specific steps are as follows: (a) After mixing the dicarboxylic acid, diol, metal dicarboxylate, and catalyst, the mixture is subjected to esterification under nitrogen or inert atmosphere at a temperature of 190-270℃ and a pressure of 0-0.5MPa until the esterification rate reaches more than 95%. Then the pressure is released to atmospheric pressure to end the esterification process. (b) After adding a stabilizer to the reaction system, gradually reduce the pressure and increase the temperature of the reaction system to 230-290℃ and ≤100Pa, and then carry out the polycondensation reaction for more than 80 minutes to obtain polyester.

Images