A method for preparing an internal salt nucleating agent for the synthesis of highly crystalline polyesters and its application.

Abstract

This invention discloses a method for preparing an internal salt nucleating agent for the synthesis of highly crystalline polyesters. The method includes: S1: dissolving a nitrogen-containing cyclic compound in acetone to form a homogeneous and stable solution system; S2: reacting the solution system obtained in S1 with a sulfur-containing compound at a constant temperature for 1-72 h, followed by filtration, washing, and drying to obtain an internal salt solid; S3: under the action of an initiator, free radically polymerizing the internal salt solid obtained in S2 with an acrylic monomer in a solvent at a molar ratio of 1:9-9:1 for 1-48 h to obtain an internal salt nucleating agent for polyester synthesis. This method offers high yield, low cost, and mild reaction conditions, effectively improving the crystallization temperature, crystallization rate, and mechanical properties of polyesters.

Description

Technical Field

[0001] This invention relates to the field of nucleating agents and polyester synthesis technology, specifically to a method for preparing and applying an internal salt nucleating agent for the synthesis of highly crystalline polyesters. Background Technology

[0002] Currently, polyester, as a semi-crystalline polymer with a certain glass transition temperature (Tg) and a relatively high melting temperature (Tm), has been widely used in synthetic fibers, films, and engineering plastics. However, due to its relatively rigid molecular structure and slow crystallization rate, its applications are somewhat limited. To meet the basic requirements for polyester as an engineering plastic, adding nucleating agents to significantly improve the polyester crystallization rate and reduce the temperature requirement for crystallization is a relatively effective and cost-efficient method.

[0003] Currently, nucleating agents used in polyesters mainly fall into three categories: inorganic nucleating agents, organic nucleating agents, and polymeric nucleating agents. The principle of inorganic nucleating agents is basically heterogeneous nucleation, and the mechanism is to promote crystallization by lowering the energy barrier for forming crystals of the critical size. Graphite, talc, carbonates, and silica are typical representatives of this type of nucleating agent. Although they are inexpensive and widely available, they suffer from poor dispersibility and color variations in polyester products. Organic nucleating agents are generally considered to promote homogeneous nucleation and increase the crystallization rate of polyesters. Typical nucleating agents are Na, Mg, and Ca salts of monocarboxylic acids, and Mg and Zn salts of organophosphorus compounds. The specific mechanism is generally believed to be through reaction with the ester bonds of the polyester, introducing carboxylate functional groups into the polyester structure. These carboxylate functional groups attract each other to form crystal nuclei, thereby increasing the crystallization rate. Although the transparency of the obtained product is improved, it also has disadvantages such as poor dispersibility and unpleasant odor. The most commonly used nucleating agents among polymers are ionomers. According to the literature, these nucleating agents mainly reduce the glass transition temperature of polyester by blending, thereby increasing the crystallization rate. The molecular weight of these nucleating agents should not be too large, otherwise it will lead to restricted molecular chain flow and poor compatibility with polyester, thus affecting crystallization.

[0004] Generally, when selecting and designing nucleating agents, it is necessary to ensure that they are as infusible as possible below the melting point of the polymer, have a similar structure to the polymer so as to have relatively good dispersibility and blendability in the polymer, and be non-toxic or low in toxicity. Based on meeting the above conditions, this invention aims to synthesize an internal salt nucleating agent that can rapidly form crystal nuclei through the combination of intramolecular / intermolecular positive and negative charges, thereby increasing the crystallization rate of polyester. This has significant implications for shortening the molding cycle and improving the mechanical properties of polyester. Summary of the Invention

[0005] In order to solve one or more technical problems existing in the prior art, one of the objectives of this application is to provide a method for preparing an internal salt nucleating agent for the synthesis of highly crystalline polyester, which has high yield, low cost, mild reaction conditions, and can effectively improve the crystallization temperature, crystallization rate and mechanical properties of polyester.

[0006] The second objective of this application is to provide an internal salt nucleating agent for polyester synthesis, which regulates the nucleation promoting ability of the nucleating agent by changing the molar ratio of the internal salt solid and the acrylic monomer, thereby improving the crystallization rate of the polyester, shortening the molding cycle, and improving the mechanical properties of the polyester.

[0007] To address the aforementioned technical problems, one of the objectives of this application is achieved through the following technical solution:

[0008] A method for preparing an internal salt nucleating agent for the synthesis of highly crystalline polyesters, the method comprising:

[0009] S1: Dissolve nitrogen-containing cyclic compounds in acetone to form a homogeneous and stable solution system;

[0010] S2: The solution system obtained in S1 is reacted with a sulfur-containing compound at a constant temperature for 1 to 72 hours, and then filtered, washed, and dried to obtain an inner salt solid;

[0011] S3: Under the action of an initiator, the inner salt solid obtained in S2 is subjected to free radical polymerization with an acrylic monomer in a solvent at a molar ratio of 1:9 to 9:1 for 1 to 48 hours to obtain an inner salt nucleating agent for polyester synthesis.

[0012] Preferably, in step S2, the molar ratio of the solution system to the sulfur-containing compound is 1:1.2 to 1.2:1, the constant temperature is between 10 and 100°C, and the washing step involves washing three times with ethyl acetate.

[0013] Preferably, the solvent reaction temperature in step S3 is 10–150°C, and the reaction time is 2–48 h.

[0014] Preferably, the nitrogen-containing cyclic compound in step S1 is vinylimidazole or a derivative thereof, and the sulfur-containing compound in step S2 is sulfonyl lactone or a derivative thereof.

[0015] Preferably, the sulfonyl lactone is 1,3-propanesulfonyl lactone.

[0016] Preferably, the initiator is an azo initiator or a peroxide initiator, including but not limited to at least one of cyclohexanone peroxide, tert-butyl hydroperoxide, azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), ditert-pentyl peroxide (DTAP), and azobisisoheptanenitrile (DIHHN). The amount of the initiator is 0.2% to 2% of the total mass of the monomer.

[0017] Preferably, the solvent is any one of ethanol, ethylene glycol, acetonitrile, ethyl acetate, dimethyl sulfoxide, butanediol, propylene glycol, butanol, propanol, N,N-dimethylformamide, N,N-diethylacetamide, N-methylpyrrolidone, and m-cresol; more preferably, it is a polar solvent.

[0018] Preferably, the acrylic monomer is at least one selected from acrylic acid, butenoic acid, 3-methyl-3-butenoic acid, 2-methyl-2-acrylic acid, 3-ethyl-3-butenoic acid, phosphate methacrylate, polyethylene glycol phosphate methacrylate, and 2-hydroxyethyl phosphate methacrylate.

[0019] The second objective of this application is achieved by the following technical solution:

[0020] An internal salt nucleating agent for polyester synthesis is used in the synthesis of highly crystalline polyester. The amount of the internal salt nucleating agent added is 0.1 wt% to 2 wt% of the total mass of the polyester.

[0021] Preferably, the highly crystalline polyester is prepared by reacting diols and diacids as raw materials in the polyester under the action of the internal salt nucleating agent. The reaction temperature of the highly crystalline polyester is 220-300°C, the reaction pressure is 30Pa-0.4MPa, and the reaction time is 3.5-10.0h.

[0022] Preferably, the esterification temperature in the esterification reaction is 220–280°C, the esterification pressure is atmospheric pressure to 0.4 MPa, and the esterification time is 1.5–3.0 h; the pre-condensation temperature in the pre-condensation reaction is 260–300°C, the vacuum degree is 30–3000 Pa, and the reaction time is 1.0–3.5 h; and the final condensation temperature in the final condensation reaction is 270–300°C, the vacuum degree is 30–240 Pa, and the reaction time is 1.0–3.5 h.

[0023] Preferably, the diacid is at least one selected from terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, adipic acid, biphenyl dicarboxylic acid, cyclohexanedicarboxylic acid, and succinic acid; the diol is a diol having 2 to 10 carbon atoms, including at least one selected from ethylene glycol, propylene glycol, 1,4-butanediol, pentanediol, and cyclohexanediethanol; the molar ratio of the diacid to the diol is 1:1.2 to 2.0.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. The nucleating agent synthesized by this method is a high molecular weight polymer. The polymer chain includes two parts: a nitrogen-containing heterocycle and an acid functional group. These two components have two key functions. On the one hand, the nitrogen-containing heterocycle (quaternary ammonium imidazole salt) part has positive and negative functional groups, which promote crystal nucleus formation and improve nucleation efficiency through positive and negative charge Coulomb interaction. On the other hand, the acid functional group contains acidic groups, which can participate in the esterification and polycondensation process of polyester synthesis to a certain extent, so that the nucleating agent has a certain compatibility with the polyester chain, thereby achieving the purpose of improving the crystallization rate and improving crystallization.

[0026] 2. The internal salt nucleating agent synthesized by this method has virtually no effect on the intrinsic viscosity of polyester after addition, overcoming the trend of traditional organic nucleating agents significantly reducing the intrinsic viscosity of polyester, and improving tensile and bending properties.

[0027] 3. The internal salt nucleating agent synthesized by this method has mild reaction conditions, low toxicity and environmental friendliness, and low price. Compared with traditional nucleating agents, its dispersibility and compatibility are improved.

[0028] 4. In polyester synthesis, the formation of crystal nuclei is promoted by the new positive and negative charge Coulomb interaction force, which can effectively improve the crystallization nucleation efficiency of polyester with a small amount of additive. At the same time, by changing the molar ratio of internal salt solid and acrylic monomer, the nucleation efficiency and crystallization rate can be further optimized and controlled. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solutions of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific examples, but these should not be construed as limiting the present patent.

[0030] Unless otherwise specified, the experimental and testing methods described in the following examples are conventional methods; the reagents and materials described are obtained from conventional commercial sources or prepared using conventional methods, unless otherwise specified.

[0031] A method for preparing an internal salt nucleating agent for the synthesis of highly crystalline polyesters, the method comprising:

[0032] S1: Dissolve a nitrogen-containing cyclic compound in acetone to form a homogeneous and stable solution system, wherein the nitrogen-containing cyclic compound is vinylimidazole or a derivative thereof;

[0033] S2: The solution system obtained in S1 is reacted with the sulfur-containing compound at a constant temperature for 1 to 72 hours and then filtered, washed and dried to obtain the inner salt solid; the sulfur-containing compound is a sulfonate lactone or its derivative, and the sulfonate lactone is 1,3-propanesulfonate lactone.

[0034] S3: Under the action of an initiator, the inner salt solid obtained in S2 is radically polymerized with acrylic monomers in a solvent at a molar ratio of 1:9 to 9:1 for 1 to 48 hours to obtain an inner salt nucleating agent for polyester synthesis; the initiator is an azo initiator or a peroxide initiator, including but not limited to at least one of cyclohexanone peroxide, tert-butyl hydroperoxide, azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), di-tert-pentyl peroxide (DTAP), and azobisisoheptanenitrile (DIHHN). The amount of the initiator is 0.2% to 2% of the total mass of the monomers; the solvent is any one of ethanol, ethylene glycol, acetonitrile, ethyl acetate, dimethyl sulfoxide, butanediol, propylene glycol, butanol, propanol, N,N-dimethylformamide, N,N-diethylacetamide, N-methylpyrrolidone, and m-cresol; more preferably, a polar solvent.

[0035] In operation, the solid internal salt, acrylic monomers, and initiator are first dissolved in a solvent, and then added dropwise to a continuously stirred polymerization reaction substrate for polymerization. The reaction temperature is 10–150°C, and the reaction time is 2–48 h. The molar ratio of the solution system to the sulfur-containing compound is 1:1.2–1.2:1, and the constant temperature is between 10–100°C. The washing step involves washing three times with ethyl acetate.

[0036] The acrylic monomer is at least one of acrylic acid, butenoic acid, 3-methyl-3-butenoic acid, 2-methyl-2-acrylic acid, 3-ethyl-3-butenoic acid, phosphate methacrylate, polyethylene glycol phosphate methacrylate, and 2-hydroxyethyl phosphate methacrylate.

[0037] The nucleating agent synthesized in this invention is a high-molecular-weight polymer, comprising two parts: a nitrogen-containing heterocycle and acidic functional groups. These two components play two key roles. Firstly, the nitrogen-containing heterocycle (quaternary ammonium imidazole salt) contains both positive and negative functional groups, which promote crystal nucleation through Coulomb interactions, thereby improving nucleation efficiency. Secondly, the acidic functional groups contain acidic groups, which can participate to some extent in the esterification and polycondensation processes of polyester synthesis, resulting in a certain degree of compatibility between the nucleating agent and the polyester chain, thus achieving the purpose of increasing the crystallization rate and improving crystallization.

[0038] Research has shown that the molar ratio of internal salt solid to acrylic monomer needs to be strictly controlled to optimize the nucleation efficiency and compatibility of the nucleating agent. Therefore, the molar ratio of internal salt solid to acrylic monomer is 1-5:5-1, which improves the crystallization temperature of polyester.

[0039] An internal salt nucleating agent for polyester synthesis is disclosed. In the polyester synthesis process, a diacid, a diol, and the internal salt nucleating agent are added to a reactor. The reactor is then evacuated and purged with nitrogen. Under nitrogen protection, esterification, pre-condensation, and final condensation reactions are carried out sequentially to obtain a highly crystalline polyester. The amount of the internal salt nucleating agent added is 0.1 wt% to 2 wt% of the total polyester mass. The esterification temperature is 220–280 °C, the pressure is atmospheric pressure to 0.4 MPa, and the esterification time is 1.0–3.0 h. The pre-condensation temperature is controlled at 260–300 °C, the vacuum degree is 30–40 Pa, and the reaction time is 1.0–3.5 h. The final condensation temperature is controlled at 270–300 °C, the vacuum degree is 30–40 Pa, and the reaction time is 1.0–3.5 h.

[0040] Wherein, the diacid is at least one selected from terephthalic acid, isophthalic acid, naphthalene-dicarboxylic acid, adipic acid, biphenyl dicarboxylic acid, cyclohexanedicarboxylic acid, and succinic acid; the diol is a diol having 2 to 10 carbon atoms, including at least one selected from ethylene glycol, propylene glycol, 1,4-butanediol, pentanediol, and cyclohexanediethanol; the molar ratio of the diacid to the diol is 1:1.2 to 2.0; the diacid includes, but is not limited to, at least one selected from terephthalic acid, isophthalic acid, naphthalene-dicarboxylic acid, adipic acid, biphenyl dicarboxylic acid, cyclohexanedicarboxylic acid, and succinic acid; the diol includes, but is not limited to, at least one selected from ethylene glycol, propylene glycol, 1,4-butanediol, pentanediol, and cyclohexanediethanol; the molar ratio of the diacid to the diol is 1:1.2 to 2.

[0041] The specific preparation method of the internal salt nucleating agent and specific examples of applying the prepared internal salt nucleating agent to the synthesis of polyester are as follows:

[0042] Example 1:

[0043] Preparation of internal salt nucleating agents:

[0044] 10 g (0.11 mol) of vinylimidazole was dissolved in 150 ml of acetone and stirred to form a homogeneous and stable solution. Then, 12.98 g (0.11 mol) of 1,3-propanesulfonic acid lactone was gradually added dropwise to the solution and reacted at 50 °C for 24 h. A white solid precipitated during the reaction. The obtained solid was filtered and washed three times with ethyl acetate, and dried to obtain the inner salt solid. Under a nitrogen atmosphere and with the initiator of azobisisobutyronitrile, the obtained inner salt solid was subjected to free radical polymerization with acrylic acid at a molar ratio of 1:1 to obtain a nucleating agent. Specifically, 10 g (0.046 mol) of the inner salt solid, 3.96 g (0.046 mol) of acrylic acid, and 0.15 g of azobisisobutyronitrile were first dissolved in 100 ml of ethylene glycol. The mixed solution was then added dropwise over 2 hours to the polymerization reaction substrate at 80 °C. After the addition was complete, the reaction continued for 3 h, and then cooled to room temperature to obtain the inner salt nucleating agent for polyester synthesis.

[0045] Polyester synthesis:

[0046] 333.3g of purified terephthalic acid, 160g of ethylene glycol, 0.13g (170ppm) of antimony glycolate catalyst, and 4.9g (1%wt) of internal salt nucleating agent were added to a 1L reactor, and esterification, pre-condensation, and final condensation reactions were carried out sequentially under nitrogen protection. The esterification temperature was 240℃, the pressure was atmospheric pressure to 0.4MPa, and the esterification time was 2.5h. The pre-condensation temperature was 270℃, the vacuum degree was 30 to 1000Pa, and the reaction time was 1.5h. The final condensation temperature was 280℃, the vacuum degree was 30 to 240Pa, and the reaction time was 1.5h, finally yielding a polyester product.

[0047] Example 2:

[0048] Preparation of internal salt nucleating agents:

[0049] 10 g (0.11 mol) of vinylimidazole was dissolved in 150 ml of acetone and stirred to form a homogeneous and stable solution. Then, 12.98 g (0.11 mol) of 1,3-propanesulfonic acid lactone was gradually added dropwise to the solution and reacted at 50 °C for 24 h. A white solid precipitated during the reaction. The obtained solid was filtered and washed three times with ethyl acetate, and dried to obtain the inner salt solid. Under a nitrogen atmosphere and with the initiator of azobisisobutyronitrile, the obtained inner salt solid was subjected to free radical polymerization with acrylic acid at a molar ratio of 1:1 to obtain a nucleating agent. Specifically, 10 g (0.046 mol) of the inner salt solid, 7.92 g (0.096 mol) of acrylic acid, and 0.15 g of azobisisobutyronitrile were first dissolved in 100 ml of ethylene glycol. The mixed solution was then added dropwise over 2 hours to the polymerization reaction substrate at 80 °C. After the addition was complete, the reaction continued for 3 h, and then cooled to room temperature to obtain the inner salt nucleating agent for polyester synthesis.

[0050] Polyester synthesis:

[0051] 333.3g of purified terephthalic acid, 160g of ethylene glycol, 0.13g (170ppm) of antimony glycolate catalyst, and 4.9g (1%wt) of internal salt nucleating agent were added to a 1L reactor, and esterification, pre-condensation, and final condensation reactions were carried out sequentially under nitrogen protection. The esterification temperature was 240℃, the pressure was atmospheric pressure to 0.4MPa, and the esterification time was 2.5h. The pre-condensation temperature was 270℃, the vacuum degree was 30 to 2000Pa, and the reaction time was 1.5h. The final condensation temperature was 280℃, the vacuum degree was 30 to 240Pa, and the reaction time was 1.5h, finally yielding a polyester product.

[0052] Example 3:

[0053] Preparation of internal salt nucleating agents:

[0054] 10 g (0.11 mol) of vinylimidazole was dissolved in 150 ml of acetone and stirred to form a homogeneous and stable solution. Then, 12.98 g (0.11 mol) of 1,3-propanesulfonic acid lactone was gradually added dropwise to the solution and reacted at 50 °C for 24 h. A white solid precipitated during the reaction. The obtained solid was filtered and washed three times with ethyl acetate, and dried to obtain the inner salt solid. Under a nitrogen atmosphere and with the initiator of azobisisobutyronitrile, the obtained inner salt solid was subjected to free radical polymerization with acrylic acid at a molar ratio of 1:1 to obtain a nucleating agent. Specifically, 15 g (0.069 mol) of the inner salt solid, 2.97 g (0.035 mol) of acrylic acid, and 0.15 g of azobisisobutyronitrile were first dissolved in 100 ml of ethylene glycol. The mixed solution was then added dropwise over 2 hours to the polymerization reaction substrate at 80 °C. After the addition was complete, the reaction continued for 3 h, and then cooled to room temperature to obtain the inner salt nucleating agent for polyester synthesis.

[0055] Polyester synthesis:

[0056] 333.3g of purified terephthalic acid, 160g of ethylene glycol, 0.13g (170ppm) of antimony glycolate catalyst, and 4.9g (1%wt) of internal salt nucleating agent were added to a 1L reactor, and esterification, pre-condensation, and final condensation reactions were carried out sequentially under nitrogen protection. The esterification temperature was 240℃, the pressure was atmospheric pressure to 0.4MPa, and the esterification time was 2.5h. The pre-condensation temperature was 270℃, the vacuum degree was 30 to 2000Pa, and the reaction time was 1.5h. The final condensation temperature was 280℃, the vacuum degree was 30 to 240Pa, and the reaction time was 1.5h, finally yielding a polyester product.

[0057] Example 4:

[0058] Preparation of internal salt nucleating agents:

[0059] 10 g (0.11 mol) of vinylimidazole was dissolved in 150 ml of acetone and stirred to form a homogeneous and stable solution. Then, 12.98 g (0.11 mol) of 1,3-propanesulfonic acid lactone was gradually added dropwise to the solution and reacted at 50 °C for 24 h. A white solid precipitated during the reaction. The obtained solid was filtered and washed three times with ethyl acetate, and dried to obtain the inner salt solid. Under a nitrogen atmosphere and with the initiator of azobisisobutyronitrile, the obtained inner salt solid was subjected to free radical polymerization with acrylic acid at a molar ratio of 1:1 to obtain a nucleating agent. Specifically, 10 g (0.046 mol) of the inner salt solid, 5.94 g (0.069 mol) of acrylic acid, and 0.15 g of azobisisobutyronitrile were first dissolved in 100 ml of ethylene glycol. The mixed solution was then added dropwise over 2 hours to the polymerization reaction substrate at 80 °C. After the addition was complete, the reaction continued for 3 h, and then cooled to room temperature to obtain the inner salt nucleating agent for polyester synthesis.

[0060] Polyester synthesis:

[0061] 333.3g of purified terephthalic acid, 160g of ethylene glycol, 0.13g (170ppm) of antimony glycolate catalyst, and 4.9g (1%wt) of internal salt nucleating agent were added to a 1L reactor, and esterification, pre-condensation, and final condensation reactions were carried out sequentially under nitrogen protection. The esterification temperature was 240℃, the pressure was atmospheric pressure to 0.4MPa, and the esterification time was 2.5h. The pre-condensation temperature was 270℃, the vacuum degree was 30 to 2000Pa, and the reaction time was 1.5h. The final condensation temperature was 280℃, the vacuum degree was 30 to 240Pa, and the reaction time was 1.5h, finally yielding a polyester product.

[0062] Comparative Example 1

[0063] Polyester synthesis:

[0064] 333.3g purified terephthalic acid, 160g ethylene glycol, 0.13g antimony glycolate (170ppm), and 4.9g (1%wt) sodium benzoate nucleating agent were added to a 1L reactor, and esterification, pre-condensation, and final condensation reactions were carried out sequentially under nitrogen protection. The esterification temperature was 240℃, the esterification pressure was atmospheric pressure to 0.4MPa, and the esterification time was 2.5h. The pre-condensation temperature was 270℃, the vacuum degree was 30 to 2000Pa, and the reaction time was 1.5h. The final condensation temperature was 280℃, the vacuum degree was 30 to 240Pa, and the reaction time was 1.5h, finally yielding a polyester product.

[0065] Comparative Example 2

[0066] 333.3g of purified terephthalic acid, 160g of ethylene glycol, and 0.13g of antimony glycol (170ppm) were added to a 1L reactor, and esterification, pre-polymerization, and final polymerization reactions were carried out sequentially under nitrogen protection. The esterification temperature was 240℃, the esterification pressure was atmospheric pressure to 0.4MPa, and the esterification time was 2.5h. The pre-polymerization temperature was 270℃, the vacuum degree was 30 to 2000Pa, and the reaction time was 1.5h. The final polymerization temperature was 280℃, the vacuum degree was 30 to 240Pa, and the reaction time was 1.5h, finally yielding a polyester product.

[0067] The relevant polyester product indicators of Examples 1-4 and Comparative Examples 1-2 were tested:

[0068] Thermal crystallization peak temperature (Tmc): The PET sample was heated to 300℃ at 20℃ / min in a differential scanning calorimeter (DSC), held at that temperature for 5 min to eliminate thermal history, and then cooled to room temperature at 20℃ / min.

[0069] Intrinsic viscosity: The PET sample was dissolved in a phenol-tetrachloroethane mixed solution with a mass ratio of 1:1, with a concentration of approximately 5 mg / mL, and measured using an Ubbelohde viscometer at 25°C.

[0070] Tensile strength was tested according to GB / T 1040-2006 standard; flexural strength was tested according to GB / T 9341-2008 standard. The test results are shown in the table below:

[0071]

[0072] By comparing the examples and Comparative Example 1, it was found that the intrinsic viscosity of PET was not affected by the present invention compared with traditional organic nucleating agents, and the mechanical properties were improved. By comparing the examples and Comparative Example 2, it was found that the nucleating agent of the present invention improved the nucleation efficiency and crystallization temperature of polyester compared with pure PET.

[0073] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for the preparation of an internal salt nucleating agent for the synthesis of high crystalline polyesters, characterized in that: The preparation method comprises: S1: dissolving a nitrogen-containing cyclic compound in acetone to form a uniform and stable solution system; the nitrogen-containing cyclic compound is vinyl imidazole; S2: reacting the solution system obtained in S1 with a sulfur-containing compound at a constant temperature for 1-72 h, and filtering, washing and drying to obtain an inner salt solid; the molar ratio of the solution system to the sulfur-containing compound is 1:1.2-1.2:1, the constant temperature is 10-100 DEG C, and the washing step uses ethyl acetate for washing three times; the sulfur-containing compound is a sulfonic acid lactone; S3: under the action of an initiator, the inner salt solid obtained in S2 is subjected to radical polymerization with an acrylic monomer in a solvent at a molar ratio of 1:9-9:1 for 1-48 h to obtain an inner salt nucleating agent for polyester synthesis; the inner salt nucleating agent is a high molecular polymer, and the polymer chain comprises a nitrogen-containing heterocyclic ring and an acid functional group; the nitrogen-containing heterocyclic ring part has positive and negative functional groups, and the positive and negative charge coulomb interaction promotes the formation of crystal nucleus and improves the nucleation efficiency; the acid functional group contains an acidic group, which can participate in the esterification and polycondensation process of polyester synthesis to a certain extent, so that the nucleating agent has a certain compatibility with the polyester chain, thereby achieving the purposes of improving the crystallization rate and improving the crystallization.

2. A process for the preparation of an internal salt nucleating agent for the synthesis of highly crystalline polyesters according to claim 1, characterized in that: The initiator is an azo initiator or a peroxide initiator, including but not limited to at least one of cyclohexanone peroxide, tert-butyl hydroperoxide, azobis isobutyronitrile AIBN, dibenzoyl peroxide BPO, di-t-amyl peroxide DTAP, and azobis isohexyl cyanide; the amount of the initiator is 0.2%-2% of the total mass of the monomers.

3. A process for the preparation of an internal salt nucleating agent for the synthesis of highly crystalline polyesters according to claim 1, characterized by the fact that: The solvent is any one of ethanol, ethylene glycol, acetonitrile, ethyl acetate, dimethyl sulfoxide, butanediol, propylene glycol, butanol, propanol, N,N-dimethylformamide, N,N-diethylacetamide, N-methyl pyrrolidone, and m-cresol.

4. Use of an inner salt nucleating agent in the synthesis of a highly crystalline polyester, characterized in that: The inner salt nucleating agent prepared by the method according to any one of claims 1-3 is used in the synthesis of high-crystalline polyester, and the addition amount of the inner salt nucleating agent accounts for 0.1wt%-2wt% of the total mass of the polyester.

5. The use according to claim 4, characterized in that: The high-crystalline polyester is prepared by reacting dihydric alcohol and diacid under the action of the inner salt nucleating agent; the reaction temperature of the high-crystalline polyester is 220-300 DEG C, the reaction pressure is 30 Pa-0.4 MPa, and the reaction time is 3.5-10.0 h.

6. The use according to claim 5, characterized in that: The high-crystalline polyester sequentially undergoes esterification, pre-polycondensation and final polycondensation in the reaction process; the esterification temperature in the esterification reaction is 220-280 DEG C, the esterification pressure is normal pressure-0.4 MPa, and the esterification time is 1.5-3.0 h; the pre-polycondensation temperature in the pre-polycondensation reaction is 260-300 DEG C, the vacuum degree is 30-3000 Pa, and the reaction time is 1.0-3.5 h; the final polycondensation temperature in the final polycondensation reaction is 270-300 DEG C, the vacuum degree is 30-240 Pa, and the reaction time is 1.0-3.5 h.

7. The use according to claim 6, characterized in that: The binary acid is at least one of terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, adipic acid, diphenyl dicarboxylic acid, cyclohexane dicarboxylic acid, succinic acid; the binary alcohol is a binary alcohol having 2-10 carbon atoms, including at least one of ethylene glycol, propylene glycol, 1,4-butanediol, pentanediol and cyclohexane dimethyl carbinol; the molar ratio of the binary acid to the binary alcohol is 1:1.2-2.0.

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