Hydrolysis-resistant polyester composition, hydrolysis-resistant polyester and preparation method thereof

Abstract

The invention relates to the field of polyester, and discloses a hydrolysis-resistant polyester composition, hydrolysis-resistant polyester and a preparation method thereof. The hydrolysis-resistant polyester composition contains polyester, a crystallization inhibitor and a hydrolysis-resistant agent, and based on the total weight of the composition, the content of the polyester is 80-99 wt%, the content of the crystallization inhibitor is 0.5-6 wt%, and the content of the hydrolysis-resistant agent is 1-10 wt%. According to the hydrolysis-resistant polyester composition, the crystallization inhibitor is introduced, so that the crystallization property of polyester can be reduced, and the problem that the hydrolysis resistance is reduced due to the crystallization property in the aging process is solved.

Description

Technical Field

[0001] The invention relates to the field of polyesters, and in particular to a hydrolysis-resistant polyester composition, a hydrolysis-resistant polyester and a preparation method thereof. Background Art

[0002] Polyethylene terephthalate (PET) has excellent mechanical, mechanical, and chemical properties. It has the advantages of heat resistance, resistance to chemical reagents, high mechanical strength, and good transparency. It is widely used in fibers, films, and bottle flakes.

[0003] Although PET has good performance, it still has the defect of poor moisture and heat resistance when used in certain fields, such as photovoltaic backplanes. This is because the high temperature and high humidity conditions outdoors will cause the hydrolysis and cleavage of the ester bonds in PET, and the generated terminal carboxyl groups have a self-catalytic effect, which will further accelerate the hydrolysis of the material, causing the mechanical properties of the material to deteriorate rapidly.

[0004] There are two main ways to modify the hydrolysis resistance of PET. One is to introduce a third component with better hydrolysis stability into the polyester chain through copolymerization, such as polyethylene glycol, naphthalene dicarboxylic acid, etc., thereby reducing the number of ester bonds and improving the hydrolysis stability of polyester. However, this method often affects the mechanical properties and processing properties of polyester.

[0005] CN110183629A discloses that a hydrolysis-resistant polyester with a low content of terminal carboxyl groups is obtained by adding a polyethylene glycol combination liquid during the polymerization stage of the polyester. The disadvantages are that the use of aluminum compounds as catalysts has insufficient activity, the synthesized polyester product is yellowish in color, and the aluminum compounds are solid, have very low solubility in ethylene glycol, and are difficult to accurately add and measure. Another method is to add a hydrolysis-resistant agent to reduce the number of terminal carboxyl groups in the system through its reaction with carboxyl groups, thereby preventing the catalytic hydrolysis of terminal carboxyl groups and inhibiting the occurrence and further development of hydrolysis.

[0006] CN103865240A discloses that a hydrolysis-resistant polyester composition is obtained by adding a capping agent glycidyl ether during a polycondensation reaction. However, during the film-making process, the glycidyl ether will generate smoke and overflow when heated, resulting in bubbles in the film, making film-making difficult and the physical properties of the obtained film unstable. Currently, commonly used hydrolysis-resistant additives mainly include carbodiimides, oxazolines and epoxies. Among them, the amino group of carbodiimide can react with the carboxyl group under relatively mild conditions. When added to the polyester material matrix, it can continuously react with the newly generated carboxyl group to slow down the hydrolysis rate of the polyester. The hydrolysis-resistant effect is the most significant, and it is currently the most commonly used hydrolysis-resistant agent in the polyester field. The inventors have found through long-term research that the use of the above-mentioned anti-hydrolysis agent modification can indeed obtain polyester with good hydrolysis resistance. After aging treatment at PCT (121°C, humidity 100%) for 48 hours, the elongation at break retention rate of the material can reach more than 80%. However, after further aging treatment such as PCT 72 hours, the mechanical properties of the material have deteriorated significantly, and the elongation at break retention rate is usually less than 10%. The inventors have observed that this may be due to the fact that under long-term water vapor and high temperature conditions, the polyester has further crystallized and generated a large number of spherulites. Especially when the aging time is long, such as 72 hours, the presence of these spherulites significantly reduces the hydrolysis resistance of the material. Therefore, there is still a need to develop polyester materials with better hydrolysis resistance. Summary of the invention

[0007] The purpose of the present invention is to overcome the problem of low hydrolysis resistance of materials in the prior art and to provide a hydrolysis-resistant polyester composition. The hydrolysis-resistant polyester composition can reduce the crystallization performance of the polyester by introducing a crystallization inhibitor, thereby solving the problem of decreased hydrolysis resistance caused by crystallization performance during aging.

[0008] In order to achieve the above-mentioned object, the present invention provides a hydrolysis-resistant polyester composition on one hand, characterized in that the composition contains polyester, a crystallization inhibitor and an anti-hydrolysis agent, wherein, based on the total weight of the composition, the content of the polyester is 80-99 weight %, the content of the crystallization inhibitor is 0.5-6 weight %, and the content of the anti-hydrolysis agent is 1-10 weight %.

[0009] Preferably, based on the total weight of the composition, the content of the polyester is 85-95% by weight, the content of the crystallization inhibitor is 1-5% by weight, and the content of the anti-hydrolysis agent is 5-10% by weight.

[0010] Preferably, the polyester comprises a condensation product of a dicarboxylic acid and an alkylene glycol.

[0011] Preferably, the dicarboxylic acid is an aromatic dicarboxylic acid having 8 to 16 carbon atoms; more preferably, the dicarboxylic acid is at least one of terephthalic acid, isophthalic acid, phthalic acid, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, 4,4'-biphenyl dicarboxylic acid and 2,2'-biphenyl dicarboxylic acid.

[0012] Preferably, the alkylene glycol is an alkylene glycol having 2 to 8 carbon atoms; more preferably, the alkylene glycol is at least one of ethylene glycol, 1,3-propylene glycol, 2,2-dimethyl-1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol and 2,3-butylene glycol.

[0013] Preferably, the crystallization inhibitor is a styrene polymer; more preferably, the crystallization inhibitor is at least one of polystyrene, acrylonitrile-styrene resin and acrylonitrile-butadiene-styrene copolymer.

[0014] Preferably, the composition further contains an antioxidant, and the content of the antioxidant is 0.5-1% by weight based on the total weight of the composition.

[0015] The second aspect of the present invention provides a method for preparing a hydrolysis-resistant polyester, characterized in that the method comprises the following steps:

[0016] 1) a step of subjecting a dicarboxylic acid to a polycondensation reaction with an alkylene glycol in the presence of a catalyst and a crystallization inhibitor to obtain a polyester product;

[0017] 2) A step of co-extruding the polyester product and an anti-hydrolysis agent.

[0018] Preferably, the molar ratio of the dicarboxylic acid to the alkylene glycol is 1:1.3-1.8.

[0019] Preferably, the amount of the crystallization inhibitor used is such that the content of the crystallization inhibitor in the obtained hydrolysis-resistant polyester is 0.5-6% by weight.

[0020] Preferably, the amount of the anti-hydrolysis agent used is such that the content of the anti-hydrolysis agent in the obtained hydrolysis-resistant polyester is 1-10% by weight.

[0021] Preferably, in the polycondensation reaction system, the weight of antimony atoms is 50-500 ppm based on the amount of the produced polyester.

[0022] Preferably, the conditions of the polycondensation reaction include: reaction temperature of 230-280° C., reaction pressure of 0-0.5 MPa, and reaction time of 60-120 min.

[0023] Preferably, the dicarboxylic acid is an aromatic dicarboxylic acid having 8 to 16 carbon atoms; more preferably, the dicarboxylic acid is at least one of terephthalic acid, isophthalic acid, phthalic acid, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, 4,4'-biphenyl dicarboxylic acid and 2,2'-biphenyl dicarboxylic acid.

[0024] Preferably, the alkylene glycol is an alkylene glycol having 2 to 8 carbon atoms; more preferably, the alkylene glycol is at least one of ethylene glycol, 1,3-propylene glycol, 2,2-dimethyl-1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol and 2,3-butylene glycol.

[0025] Preferably, the crystallization inhibitor is a styrene polymer; more preferably, the crystallization inhibitor is at least one of polystyrene, acrylonitrile-styrene resin and acrylonitrile-butadiene-styrene copolymer.

[0026] Preferably, the anti-hydrolysis agent is at least one of a carbodiimide compound and a glycidyl ether compound.

[0027] Preferably, the coextrusion is carried out in the presence of an antioxidant, and the amount of the antioxidant used is such that the content of the antioxidant in the obtained hydrolysis-resistant polyester is 0.5-2% by weight.

[0028] The third aspect of the present invention provides a hydrolysis-resistant polyester prepared by the method described in the second aspect of the present invention.

[0029] Through the above technical scheme, a crystallization inhibitor is added to reduce the influence of crystallization performance on the hydrolysis resistance of polyester during aging. The prepared hydrolysis-resistant polyester still has a good elongation retention rate at break after 72 hours of aging treatment, achieving good technical effects. DETAILED DESCRIPTION

[0030] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0031] According to a first aspect of the present invention, a hydrolysis-resistant polyester composition is provided, characterized in that the composition contains polyester, a crystallization inhibitor and an anti-hydrolysis agent, wherein, based on the total weight of the composition, the content of the polyester is 80-99 weight %, the content of the crystallization inhibitor is 0.5-6 weight %, and the content of the anti-hydrolysis agent is 1-10 weight %.

[0032] In order to further improve the hydrolysis resistance, preferably, the content of the polyester is 85-95% by weight, the content of the crystallization inhibitor is 1-5% by weight, and the content of the anti-hydrolysis agent is 5-10% by weight.

[0033] According to the present invention, preferably, the polyester contains a polycondensate of a dicarboxylic acid and an alkylene glycol.

[0034] In the present invention, considering the mechanical strength, heat resistance and ease of obtaining of polyester, the dicarboxylic acid is an aromatic dicarboxylic acid having 8-16 carbon atoms; more preferably, the dicarboxylic acid is at least one of terephthalic acid, isophthalic acid, phthalic acid, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, 4,4'-biphenyl dicarboxylic acid and 2,2'-biphenyl dicarboxylic acid.

[0035] In the present invention, considering the mechanical strength, heat resistance and ease of obtaining of polyester, the alkylene glycol is an alkylene glycol having 2-8 carbon atoms; more preferably, the alkylene glycol is at least one of ethylene glycol, 1,3-propylene glycol, 2,2-dimethyl-1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol and 2,3-butylene glycol.

[0036] According to the present invention, in order to reduce the crystallization performance of the polyester and prevent the decrease in hydrolysis resistance caused by the crystallization performance during aging, the crystallization inhibitor is a styrene polymer; more preferably, the crystallization inhibitor is at least one of polystyrene, acrylonitrile-styrene resin and acrylonitrile-butadiene-styrene copolymer.

[0037] According to the present invention, in order to improve the comprehensive performance, service life and hydrolysis resistance of the polymer material, the anti-hydrolysis agent is at least one of a carbodiimide compound and a glycidyl ether compound.

[0038] According to the present invention, in order to prevent lipid oxidation and delay the time when rubber products begin to relax, preferably, the composition also contains an antioxidant, and the content of the antioxidant is 0.5-2 weight% based on the total weight of the composition; more preferably, the content of the antioxidant is 0.5-1 weight% based on the total weight of the composition.

[0039] Among them, preferably, the antioxidant is a derivative of p-phenylenediamine; more preferably, the antioxidant is at least one of phenylnaphthylamines, ketoamine antioxidants, diphenylamine derivatives and p-phenylenediamine derivatives.

[0040] According to a second aspect of the present invention, a method for preparing a hydrolysis-resistant polyester is provided, characterized in that the method comprises the following steps:

[0041] 1) a step of subjecting a dicarboxylic acid to a polycondensation reaction with an alkylene glycol in the presence of a catalyst and a crystallization inhibitor to obtain a polyester product;

[0042] 2) A step of co-extruding the polyester product and an anti-hydrolysis agent.

[0043] According to the present invention, the molar ratio of the dicarboxylic acid to the alkylene glycol is 1:1.3-1.8; more preferably, the molar ratio of the dicarboxylic acid to the alkylene glycol is 1:1.4-1.6.

[0044] According to the present invention, preferably, the amount of the crystallization inhibitor used is such that the content of the crystallization inhibitor in the obtained hydrolysis-resistant polyester is 0.5-6 wt %; more preferably, the amount of the crystallization inhibitor used is such that the content of the crystallization inhibitor in the obtained hydrolysis-resistant polyester is 1-5 wt %.

[0045] According to the present invention, in order to improve the hydrolysis resistance of the hydrolysis-resistant polyester, preferably, the amount of the hydrolysis-resistant agent is such that the content of the hydrolysis-resistant agent in the obtained hydrolysis-resistant polyester is 1-10 wt %; more preferably, the amount of the hydrolysis-resistant agent is such that the content of the hydrolysis-resistant agent in the obtained hydrolysis-resistant polyester is 5-10 wt %.

[0046] According to the present invention, the amount of the catalyst is selected according to the amount of active metal in the catalyst. Preferably, the weight of antimony atoms is 50-500ppm based on the amount of polyester produced; more preferably, the weight of antimony atoms is 200-250ppm based on the amount of polyester produced.

[0047] According to the present invention, the conditions of the polycondensation reaction include: reaction temperature of 230-280°C, reaction pressure of 0-0.5MPa, and reaction time of 60-120min; more preferably, the conditions of the polycondensation reaction include: reaction temperature of 250-280°C, reaction pressure of 0-150Pa, and reaction time of 100-120min

[0048] According to the present invention, considering the mechanical strength, heat resistance and ease of obtaining of polyester, the dicarboxylic acid is an aromatic dicarboxylic acid with 8-16 carbon atoms; more preferably, the dicarboxylic acid is at least one of terephthalic acid, isophthalic acid, phthalic acid, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, 4,4'-biphenyl dicarboxylic acid and 2,2'-biphenyl dicarboxylic acid.

[0049] According to the present invention, considering the mechanical strength, heat resistance and ease of obtaining of polyester, the alkylene glycol is an alkylene glycol having 2-8 carbon atoms; more preferably, the alkylene glycol is at least one of ethylene glycol, 1,3-propylene glycol, 2,2-dimethyl-1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol and 2,3-butylene glycol.

[0050] According to the present invention, in order to reduce the crystallization performance of the polyester and prevent the decrease in hydrolysis resistance caused by the crystallization performance during aging, the crystallization inhibitor is a styrene polymer; more preferably, the crystallization inhibitor is at least one of polystyrene, acrylonitrile-styrene resin and acrylonitrile-butadiene-styrene copolymer; further preferably, the crystallization inhibitor is polystyrene.

[0051] According to the present invention, in order to improve the comprehensive performance, service life and hydrolysis resistance of the polymer material, preferably, the anti-hydrolysis agent is at least one of a carbodiimide compound and a glycidyl ether compound.

[0052] In a preferred embodiment of the present invention, the anti-hydrolysis agent is polycarbodiimide.

[0053] According to the present invention, in order to prevent lipid oxidation and delay the time when the rubber product begins to relax, preferably, the composition also contains an antioxidant, and the coextrusion is carried out in the presence of the antioxidant. The amount of the antioxidant is such that the content of the antioxidant in the obtained hydrolysis-resistant polyester is 0.5-2% by weight.

[0054] In a preferred embodiment of the present invention, the co-extrusion is performed using a twin-screw extruder. Preferably, the co-extrusion conditions include: a temperature of 200-290°C and a time of 30-120 min; more preferably, the co-extrusion conditions include: a temperature of 220-290°C and a time of 60-90 min.

[0055] According to a third aspect of the present invention, there is provided a hydrolysis-resistant polyester prepared by the method described in the second aspect of the present invention.

[0056] The present invention is described in detail below by way of examples, but the present invention is not limited to the following examples.

[0057] Example 1

[0058] Preparation of Polyester A

[0059] 500g of terephthalic acid, 316g of ethylene glycol and catalyst ethylene glycol antimony (based on the amount of polyester generated, the weight of antimony atoms is 200ppm) and 1% of polystyrene (purchased from Beijing Wokai Biotechnology Co., Ltd.) relative to the weight of polyester are mixed into a slurry and added into a polymerization kettle for esterification reaction at a temperature of 250-280°C, a pressure of 0.25MPa, and a time of 120min. The water generated by the reaction is discharged through a rectification device. After the esterification is completed, the pressure is reduced to normal pressure, and the system pressure is reduced by vacuum to less than 150Pa. At the same time, the reaction temperature is gradually increased to 280°C. When the system reaction reaches 120min, the reaction is stopped, and then the reaction product is squeezed out from the bottom of the polymerization kettle, cooled, and pelletized for the next step of processing.

[0060] Preparation of hydrolysis-resistant polyester

[0061] The temperature of each heating section of a twin-screw extruder (purchased from Thermo Fisher Scientific, model polylab) was controlled to be 220-290° C., specifically, the temperature of zone 1 was 220° C., the temperature of zone 2 was 270° C., the temperature of zone 3 was 280° C., and the temperature of zones 4 and 5 was 290° C. 1 kg of polyester A, hydrolysis-resistant agent polycarbodiimide (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) and antioxidant 1098 (purchased from BASF AG) were mixed and added into the twin-screw extruder for extrusion granulation, wherein the weight ratio of polycarbodiimide to the hydrolysis-resistant polyester was 5%, and the weight ratio of antioxidant 1098 to the hydrolysis-resistant polyester was 1‰. Hydrolysis-resistant polyester was obtained.

[0062] Example 2

[0063] Preparation of Polyester B

[0064] 500g of terephthalic acid, 316g of ethylene glycol and catalyst ethylene glycol antimony (based on the amount of polyester produced, the weight of antimony atoms is 200ppm) and 2.5% polystyrene relative to the weight of polyester are mixed into a slurry and added into a polymerization kettle for esterification reaction at a temperature of 250-280°C and a pressure of 0.25MPa. The water generated by the reaction is discharged through a rectification device. After the esterification is completed, the pressure is reduced to normal pressure, and the system pressure is reduced by vacuum to less than 150Pa. At the same time, the reaction temperature is gradually increased to 280°C. When the system reaction reaches 120min, the reaction is stopped. After that, the reaction product is squeezed out from the bottom of the polymerization kettle, cooled, and pelletized for the next step of processing.

[0065] Preparation of hydrolysis-resistant polyester

[0066] The temperature of each heating section of the twin-screw extruder is controlled to be 220-290° C., specifically, the temperature of the first zone is 220° C., the temperature of the second zone is 270° C., the temperature of the third zone is 280° C., and the temperature of the fourth and fifth zones is 290° C. 1 kg of polyester B, hydrolysis-resistant agent polycarbodiimide and antioxidant 1098 are mixed and added into the twin-screw extruder for extrusion granulation, wherein the weight ratio of polycarbodiimide to the hydrolysis-resistant polyester is 5%, and the weight ratio of antioxidant 1098 to the hydrolysis-resistant polyester is 1‰. Hydrolysis-resistant polyester is obtained.

[0067] Example 3

[0068] Preparation of Polyester C

[0069] 500g of terephthalic acid, 316g of ethylene glycol and catalyst ethylene glycol antimony (based on the amount of polyester produced, the weight of antimony atoms is 200ppm) and 5% polystyrene relative to the weight of polyester are mixed into a slurry and added into a polymerization kettle for esterification reaction. The esterification temperature is 250-280℃ and the pressure is 0.25MPa. The water generated by the reaction is discharged through a rectification device. After the esterification is completed, the pressure is reduced to normal pressure, and the system pressure is reduced by vacuum to less than 150Pa. At the same time, the reaction temperature is gradually increased to 280℃. When the system reaction reaches 120min, the reaction is stopped. After that, the reaction product is squeezed out from the bottom of the polymerization kettle, cooled, and pelletized for the next step of processing.

[0070] Preparation of hydrolysis-resistant polyester

[0071] The temperature of each heating section of the twin-screw extruder is controlled to be 220-290°C, specifically, the temperature of the first zone is 220°C, the temperature of the second zone is 270°C, the temperature of the third zone is 280°C, and the temperature of the fourth and fifth zones is 290°C. 1 kg of polyester C, hydrolysis-resistant agent polycarbodiimide and antioxidant 1098 are mixed and added into the twin-screw extruder for extrusion granulation, wherein the weight ratio of polycarbodiimide to the hydrolysis-resistant polyester is 5%, and the weight ratio of antioxidant 1098 to the hydrolysis-resistant polyester is 1‰. Hydrolysis-resistant polyester is obtained.

[0072] Example 4

[0073] The method of Example 2 was followed, except that 0.5% polystyrene was added relative to the weight of the polyester, and hydrolysis-resistant polyester was obtained in the same manner.

[0074] Example 5

[0075] The method of Example 2 was followed, except that 8% polystyrene was added relative to the weight of the polyester, and hydrolysis-resistant polyester was obtained in the same manner.

[0076] Example 6

[0077] The method of Example 2 is followed, except that the weight ratio of polycarbodiimide to polyester is 1%, and the hydrolysis-resistant polyester is obtained in the same manner.

[0078] Example 7

[0079] The method of Example 2 is followed, except that the weight ratio of polycarbodiimide to polyester is 10%, and the hydrolysis-resistant polyester is obtained in the same manner.

[0080] Example 8

[0081] The method of Example 2 is followed, except that the weight ratio of polycarbodiimide to polyester is 2.5%. The hydrolysis-resistant polyester is obtained in the same manner.

[0082] Example 9

[0083] The method of Example 2 is followed, except that carbodiimide is used as the anti-hydrolysis agent, and the weight ratio of carbodiimide to polyester is 5%. The hydrolysis-resistant polyester is obtained in the same manner.

[0084] Example 10

[0085] The method of Example 2 was followed, except that styrene-acrylonitrile copolymer (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) was used as the crystallization inhibitor to obtain hydrolysis-resistant polyester in the same manner.

[0086] Embodiment 11

[0087] The method of Example 2 was followed, except that butadiene-styrene copolymer (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) was used as the crystallization inhibitor to obtain hydrolysis-resistant polyester in the same manner.

[0088] Example 12

[0089] The method of Example 2 was followed, except that glycidyl ether (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) was used as the anti-hydrolysis agent, and the hydrolysis-resistant polyester was obtained in the same manner.

[0090] Comparative Example 1

[0091] Preparation of Polyester D

[0092] 500g of terephthalic acid, 316g of ethylene glycol and catalyst ethylene glycol antimony (based on the amount of polyester produced, the weight of antimony atoms is 200ppm) are mixed into a slurry, added into a polymerization kettle, and esterification reaction is carried out at a temperature of 250-280°C and a pressure of 0.25MPa. The water generated by the reaction is discharged through a rectification device. After the esterification is completed, the pressure is reduced to normal pressure, and the system pressure is reduced by vacuum until it is lower than 150Pa. At the same time, the reaction temperature is gradually increased to 280°C. When the system reaction reaches 120min, the reaction is stopped, and then the reaction product is extruded from the bottom of the polymerization kettle, cooled, and pelletized to obtain polyester D.

[0093] Comparative Example 2

[0094] Preparation of Polyester B

[0095] 500g of terephthalic acid, 316g of ethylene glycol and catalyst ethylene glycol antimony (based on the amount of polyester produced, the weight of antimony atoms is 200ppm) and 2.5% of polystyrene relative to the weight of polyester are mixed into a slurry and added into a polymerization kettle for esterification reaction. The esterification temperature is 250-280℃ and the pressure is 0.25MPa. The water generated by the reaction is discharged through a rectification device. After the esterification is completed, the pressure is reduced to normal pressure, and the system pressure is reduced by vacuum to less than 150Pa. At the same time, the reaction temperature is gradually increased to 280℃. When the system reaction reaches 120min, the reaction is stopped. After that, the reaction product is extruded from the bottom of the polymerization kettle, cooled, and pelletized to obtain polyester B.

[0096] Comparative Example 3

[0097] Preparation of hydrolysis-resistant polyester

[0098] The temperature of each heating section of the twin-screw extruder is controlled to be 220-290°C, specifically, the temperature of zone 1 is 220°C, the temperature of zone 2 is 270°C, the temperature of zone 3 is 280°C, and the temperature of zones 4 and 5 is 290°C. 1 kg of polyester D, hydrolysis-resistant agent polycarbodiimide and antioxidant 1098 are mixed and added into the twin-screw extruder for extrusion granulation, wherein the weight ratio of polycarbodiimide to polyester is 5%, and the weight ratio of antioxidant 1098 to polyester is 1‰. Hydrolysis-resistant polyester is obtained.

[0099] Comparative Example 4

[0100] The method of Example 2 was followed, except that 0.3% polystyrene was added relative to the weight of the polyester, and hydrolysis-resistant polyester was obtained in the same manner.

[0101] Comparative Example 5

[0102] The method of Example 2 was followed, except that 6.3% polystyrene was added relative to the weight of the polyester, and hydrolysis-resistant polyester was obtained in the same manner.

[0103] Test Example 1

[0104] The hydrolysis-resistant polyesters prepared in Examples 1-12 and Comparative Examples 1-5 were subjected to the following tests. The test results are shown in Table 1.

[0105] The elongation at break retention rate was tested after aging for 72 hours at a temperature of 121°C and a humidity of 100%.

[0106] Elongation at break retention rate = elongation at break of sample before aging - elongation at break of sample after aging.

[0107] Table 1

[0108]

[0109] As shown in Table 1, by comparing Examples 1-8 with Comparative Examples 1-3, it can be seen that the present invention can significantly improve the elongation at break retention of the samples through the synergistic effect of the crystallization inhibitor and the anti-hydrolysis agent.

[0110] By comparing Examples 1-3 and 4-5, it can be seen that by setting the crystallization inhibitor in the range of 1-5 wt % (based on the obtained hydrolysis-resistant polyester), the elongation retention rate at break of the sample can be further improved.

[0111] By comparing Examples 2, 6, 7 and 8, it can be seen that by setting the anti-hydrolysis agent in the range of 5-10 wt % (based on the obtained hydrolysis-resistant polyester), the elongation retention rate at break of the sample can be further significantly improved.

[0112] By comparing Examples 2 and 9, it can be seen that the use of polycarbodiimide can further significantly improve the elongation retention rate of the sample at break compared to carbodiimide.

[0113] By comparing Examples 2, 10, 11 and 12, it can be seen that by using polystyrene, the elongation retention rate of the sample at break can be further significantly improved compared with styrene-acrylonitrile and copolymer butadiene-styrene copolymer.

[0114] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A hydrolysis-resistant polyester composition, characterized in that: The composition contains polyester, a crystallization inhibitor and an anti-hydrolysis agent, wherein, based on the total weight of the composition, the content of the polyester is 80-99 weight percent, the content of the crystallization inhibitor is 0.5-6 weight percent, and the content of the anti-hydrolysis agent is 1-10 weight percent.

2. The composition according to claim 1, wherein Based on the total weight of the composition, the content of the polyester is 80-99 weight %, the content of the crystallization inhibitor is 0.5-6 weight %, and the content of the anti-hydrolysis agent is 1-10 weight %.

3. The composition according to claim 1, wherein The polyester contains a polycondensate of a dicarboxylic acid and an alkylene glycol.

4. The composition according to claim 3, wherein The dicarboxylic acid is an aromatic dicarboxylic acid having 8 to 16 carbon atoms; or The dicarboxylic acid is at least one of terephthalic acid, isophthalic acid, phthalic acid, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, 4,4'-biphenyl dicarboxylic acid and 2,2'-biphenyl dicarboxylic acid.

5. The composition according to claim 3 or 4, wherein The alkylene glycol is an alkylene glycol having 2 to 8 carbon atoms; or The alkylene glycol is at least one of ethylene glycol, 1,3-propylene glycol, 2,2-dimethyl-1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol and 2,3-butylene glycol.

6. The composition according to any one of claims 1 to 5, wherein The crystallization inhibitor is a styrene polymer; or The crystallization inhibitor is at least one of polystyrene, acrylonitrile-styrene resin and acrylonitrile-butadiene-styrene copolymer.

7. The composition according to any one of claims 1 to 5, wherein The anti-hydrolysis agent is at least one of a carbodiimide compound and a glycidyl ether compound.

8. The composition according to any one of claims 1 to 5, wherein The composition further contains an antioxidant, and the content of the antioxidant is 0.5-2 weight % based on the total weight of the composition.

9. A method for preparing hydrolysis-resistant polyester, characterized in that: The method comprises the following steps, 1) a step of subjecting a dicarboxylic acid to a polycondensation reaction with an alkylene glycol in the presence of a catalyst and a crystallization inhibitor to obtain a polyester product; 2) A step of co-extruding the polyester product and an anti-hydrolysis agent.

10. The method according to claim 9, wherein: The molar ratio of the dicarboxylic acid to the alkylene glycol is 1:1.3-1.

8.

11. The method according to claim 9, wherein: The amount of the crystallization inhibitor used is such that the content of the crystallization inhibitor in the obtained hydrolysis-resistant polyester is 0.5-6% by weight.

12. The method according to any one of claims 9 to 11, wherein: The amount of the anti-hydrolysis agent used is such that the content of the anti-hydrolysis agent in the obtained hydrolysis-resistant polyester is 1-10% by weight.

13. The method according to any one of claims 9 to 11, wherein: The weight of antimony atoms is 50 to 500 ppm based on the amount of the produced polyester.

14. The method according to any one of claims 9 to 11, wherein: The conditions of the polycondensation reaction include: reaction temperature of 230-280° C., reaction pressure of 0-0.5 MPa, and reaction time of 60-120 min.

15. The method according to any one of claims 9 to 11, wherein: The dicarboxylic acid is an aromatic dicarboxylic acid having 8 to 16 carbon atoms; or The dicarboxylic acid is at least one of terephthalic acid, isophthalic acid, phthalic acid, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, 4,4'-biphenyl dicarboxylic acid and 2,2'-biphenyl dicarboxylic acid.

16. The method according to any one of claims 9 to 11, wherein: The alkylene glycol is an alkylene glycol having 2 to 8 carbon atoms; or The alkylene glycol is at least one of ethylene glycol, 1,3-propylene glycol, 2,2-dimethyl-1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol and 2,3-butylene glycol.

17. The method according to any one of claims 9 to 11, wherein: The crystallization inhibitor is a styrene polymer; or The crystallization inhibitor is at least one of polystyrene, acrylonitrile-styrene resin and acrylonitrile-butadiene-styrene copolymer.

18. The method according to any one of claims 9 to 11, wherein: The anti-hydrolysis agent is at least one of a carbodiimide compound and a glycidyl ether compound.

19. The method according to any one of claims 9 to 11, wherein: The coextrusion is carried out in the presence of an antioxidant, and the amount of the antioxidant used is such that the content of the antioxidant in the obtained hydrolysis-resistant polyester is 0.5-2% by weight.

20. A hydrolysis-resistant polyester prepared by the method according to any one of claims 9 to 19.

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