High-molecular-weight polydiethylene glycol phthalate, preparation method thereof and low-warping hydrolysis-resistant glass fiber reinforced PBT (polybutylene terephthalate)

Abstract

The invention relates to high-molecular-weight polydiethylene glycol phthalate, a preparation method thereof and low-warping hydrolysis-resistant glass fiber reinforced PBT (polybutylene terephthalate) in the field of resin. The high-molecular-weight polydiethylene glycol phthalate has a structure as shown in a formula (I), and the low-warping hydrolysis-resistant glass fiber reinforced PBT is prepared from the following components: PBT, high-molecular-weight polydiethylene glycol phthalate, an inorganic filler and glass fibers. By adding the high-molecular-weight polydiethylene glycol phthalate, the tensile strength and bending strength of a PBT and high-molecular-weight polydiethylene glycol phthalate blending system can be improved, the notch impact strength of the system can be improved to a certain extent, the molding shrinkage rate of the blending system is reduced, and the PBT / high-molecular-weight polydiethylene glycol phthalate blending system has hydrolysis resistance and can be used for preparing the PBT / high-molecular-weight polydiethylene glycol phthalate composite material. And the effect is obvious.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of resin, and more particularly to a high molecular weight polydiethylene phthalate, a preparation method thereof and a low warpage hydrolysis-resistant glass fiber reinforced PBT. BACKGROUND

[0002] Polybutylene terephthalate (PBT) has excellent performance and is widely used in the automotive industry, electronics, electrical equipment and other industries. However, PBT also has some shortcomings that need to be improved, such as the relative slip of PBT material molecules is easy to orient and crystallize, resulting in a large shrinkage rate of the material, which causes the warpage deformation of PBT parts, especially large thin-walled parts. The difference between the length and width shrinkage rates of conventional low warpage PBT in the prior art is generally about 0.8, which cannot meet the increasing requirement of the market for low warpage of products.

[0003] With the development and innovation of science and technology, the warpage performance requirement of polybutylene terephthalate (PBT) in the field of intelligent home appliances is increasingly stringent. Household dishwashers, washing machines, robotic vacuum cleaners and other equipment are long-term indoor humid environments, and their requirements for quietness and humidity control are continuously improving, and at the same time, the parts are also required to have better low warpage. SUMMARY

[0004] In order to solve the above-mentioned problems existing in the prior art, the present application proposes a high molecular weight polydiethylene phthalate, a preparation method thereof and a low warpage hydrolysis-resistant glass fiber reinforced PBT. Specifically, it relates to a high molecular weight polydiethylene phthalate and a preparation method thereof, as well as a low warpage hydrolysis-resistant glass fiber reinforced PBT and a preparation method and application thereof.

[0005] The present application prepares a high molecular weight polydiethylene phthalate which can affect the shrinkage of PBT, blends the two, studies the effect of the content of high molecular weight polydiethylene phthalate on the molding shrinkage, mechanical properties and thermal properties of the PBT / high molecular weight polydiethylene phthalate system, and obtains a PBT / high molecular weight polydiethylene phthalate ratio with better comprehensive performance through analysis and comparison.

[0006] The glass fiber reinforced PBT prepared by blending the high molecular weight polydiethylene phthalate developed by the present application with PBT has a length and width shrinkage rate of 0.25-0.46 and can meet the water boiling experiment. In addition, the tonal purchase price of traditional warpage reduction additives (such as glass fiber modification compatibilizers and nucleating agent compounding systems) is about 18000-22000 yuan, which has a high cost. We use cheap diols to prepare high molecular weight polyesters, and the tonal cost is only 8000-12000 yuan. In the actual application process, the traditional method of reducing warpage cannot achieve the effect of the present application, and the mechanical properties are reduced, which is not practical.

[0007] One of the purposes of the present application is to provide a high molecular weight polydiethylene glycol phthalate having the structure shown in formula (I):

[0008]

[0009] In formula (I), the subscript n represents the number of corresponding units, and n can be a natural number ≥1, indicating that one or more units are contained. The present application does not make special requirements for the specific value of n.

[0010] Alternatively, the high molecular weight polydiethylene glycol phthalate described in the present application is a polymer containing a unit having the structure shown in formula (II):

[0011]

[0012] In the present application, the melt index is used to represent the high and low molecular weight. When the melt index of the polydiethylene glycol phthalate is ≤50 g / 10 min under the test conditions of 160℃ and 2.16 kg load, it is a high molecular weight polydiethylene glycol phthalate. The melt index of the high molecular weight polydiethylene glycol phthalate described in the present application can be ≤50 g / 10 min under the test conditions of 160℃ and 2.16 kg load, for example, specifically 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50 g / 10 min or any value between the above-mentioned values or a value range between any two of the above-mentioned values, for example, 10-45 g / 10 min, 10-40 g / 10 min, etc.

[0013] The second purpose of the present application is to provide a preparation method of the high molecular weight polydiethylene glycol phthalate, which can include the following steps:

[0014] The diethylene glycol and phthalic acid are subjected to esterification reaction and vacuum polycondensation to obtain the high molecular weight polydiethylene glycol phthalate.

[0015] Preferably, the preparation method of the high molecular weight polydiethylene glycol phthalate can include the following steps:

[0016] The diethylene glycol and phthalic acid are subjected to esterification reaction, after the esterification reaction, the components including catalyst and antioxidant are added, vacuum is drawn, the temperature in the system is kept (the temperature in the system can be kept at 240-250°C), and vacuum degree (the vacuum degree can be below 300Pa) is kept, and the reaction is continued (the reaction can be continued for 1-3 hours), preferably, a chain extender is added (the chain extender can be added or not added, and the chain extender is preferably added), to obtain high molecular weight polydiethylene glycol phthalate;

[0017] When one of the following two phenomena occurs, the esterification reaction is ended:

[0018] 1) the gas phase temperature in the reaction system is reduced to below 50°C; and / or,

[0019] 2) the reaction water reaches 60%-70% of the theoretical value (1 carboxyl and 1 hydroxyl react, and 1 molecule of water is removed);

[0020] In the above,

[0021] The molar ratio of diethylene glycol to phthalic acid is 1.6: (1-0.5), for example, it can be 1.6:1, 1.6:0.9, 1.6:0.8, 1.6:0.7, 1.6:0.6, 1.6:0.5, or any value between the above values or a value range between any two of the above values, for example, it can be 1: (0.6-0.9);

[0022] Preferably, the temperature of the esterification reaction is between 230-245°C.

[0023] Specifically, the vacuum drawing can be 30-60min from normal pressure to a vacuum degree below 300Pa in the system; and / or,

[0024] The catalyst can be selected from one or more of dibutyltin dilaurate, triethyl phosphate, and tetrabutyl titanate, and preferably is dibutyltin dilaurate; the amount of the catalyst can be 0.1-0.5wt% of the weight of phthalic acid, for example, it can be specifically 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, or any value between the above values or a value range between any two of the above values; and / or,

[0025] The antioxidant used in the preparation method of the high molecular weight polydiethylene glycol phthalate can be selected from one or more of trimethyl phosphite and triethyl phosphate; the amount of the antioxidant can be 0.1-0.5wt% of the weight of phthalic acid, for example, it can be specifically 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, or any value between the above values or a value range between any two of the above values; and / or,

[0026] The chain extender can be a phenolic epoxy type chain extender; preferably, the chain extender can be used in an amount of 1-5 ‰ by weight of phthalic acid, for example, specifically 1 ‰, 2 ‰, 3 ‰, 4 ‰, 5 ‰, or any value between the above-mentioned values or a value range between any two of the above-mentioned values.

[0027] The synthesis of the high molecular weight polydiethylene phthalate can refer to:

[0028]

[0029] The third object of the present application is to provide the high molecular weight polydiethylene phthalate prepared by the method for preparing the high molecular weight polydiethylene phthalate according to the second object of the present application.

[0030] The fourth object of the present application is to provide a low warpage hydrolysis resistant glass fiber reinforced PBT, which can comprise PBT, high molecular weight polydiethylene phthalate, inorganic filler, glass fiber.

[0031] More preferably, the low warpage hydrolysis resistant glass fiber reinforced PBT can comprise the following components blended in percentage by weight, based on 100% of the total weight of the low warpage hydrolysis resistant glass fiber reinforced PBT.

[0032]

[0033]

[0034] In some embodiments of the present application,

[0035] The PBT can have a melt index of 10-40 g / 10 min under the test conditions of 250℃, 2.16 kg load, for example, specifically 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 g / 10 min, or any value between the above-mentioned values or a value range between any two of the above-mentioned values, for example, 10-25 g / 10 min, etc. The PBT can be used in an amount of 50-70%, for example, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, or any value between the above-mentioned values or a value range between any two of the above-mentioned values, for example, 50-65%, 57-60%, etc., based on 100% of the total weight of the low warpage hydrolysis resistant glass fiber reinforced PBT.

[0036] In some embodiments of the present application,

[0037] The high molecular weight polydiethylene phthalate can be used in an amount of 3 to 15 %, for example specifically 3 %, 4 %, 5 %, 6 %, 7 %, 8 %, 9 %, 10 %, 11 %, 12 %, 13 %, 14 %, 15 %, or any value or range of values between any of the aforementioned values, for example 5 to 15 %, 5 to 10 %, etc., based on 100 % of the total weight of the low warpage hydrolysis resistant glass fiber reinforced PBT.

[0038] The inorganic filler can be selected from one or more of mica, calcium sulfate whisker, talc powder; preferably, the mica is passed through an 800 mesh sieve. The inorganic filler can be used in an amount of 2 to 10 %, for example specifically 2 %, 3 %, 4 %, 5 %, 6 %, 7 %, 8 %, 9 %, 10 %, or any value or range of values between any of the aforementioned values, for example 2 to 7 %, 2 to 5 %, etc., based on 100 % of the total weight of the low warpage hydrolysis resistant glass fiber reinforced PBT.

[0039] In some embodiments of the present application,

[0040] The average filament diameter of the glass fiber can be 5 to 20 μιη, for example specifically 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 μιη, or any value or range of values between any of the aforementioned values, for example 8 to 12 μιη, etc. The glass fiber can be used in an amount of 10 to 40 %, for example specifically 10 %, 11 %, 12 %, 13 %, 14 %, 15 %, 16 %, 17 %, 18 %, 19 %, 20 %, 21 %, 22 %, 23 %, 24 %, 25 %, 26 %, 27 %, 28 %, 29 %, 30 %, 31 %, 32 %, 33 %, 34 %, 35 %, 36 %, 37 %, 38 %, 39 %, 40 %, or any value or range of values between any of the aforementioned values, for example 20 to 35 %, 25 to 35 %, etc., based on 100 % of the total weight of the low warpage hydrolysis resistant glass fiber reinforced PBT.

[0041] In some embodiments of the present application,

[0042] The low warpage hydrolysis-resistant glass fiber reinforced PBT can further comprise an antioxidant; the antioxidant in the glass fiber reinforced PBT can be one or more of trimethyl phosphite, triethyl phosphate, antioxidant 1010, antioxidant S-9228; the amount of the antioxidant can be a conventional amount in the art, preferably, the weight amount of the antioxidant in the glass fiber reinforced PBT can be 0.1-0.3% based on 100% of the total weight of the low warpage hydrolysis-resistant glass fiber reinforced PBT, for example, can be 0.1%, 0.2%, 0.3% or any value between the above values or a value range between any two of the above values.

[0043] The fifth object of the present application is to provide a preparation method of the low warpage hydrolysis-resistant glass fiber reinforced PBT, which can comprise the following steps:

[0044] The components including PBT, high molecular weight polydiethylene phthalate, inorganic filler, optional antioxidant are mixed, and then extruded and granulated with glass fiber, dried to obtain the low warpage hydrolysis-resistant glass fiber reinforced PBT;

[0045] Specifically, a double-screw extruder can be used for extrusion granulation;

[0046] Specifically, the temperature of the extrusion granulation can be 230-270°C;

[0047] Specifically, the drying can be drying at 100-120°C for 3-5h.

[0048] The sixth object of the present application is to provide the low warpage hydrolysis-resistant glass fiber reinforced PBT obtained by the preparation method of the low warpage hydrolysis-resistant glass fiber reinforced PBT.

[0049] The seventh object of the present application is to provide the application of the high molecular weight polydiethylene phthalate or the preparation method thereof, or the application of the low warpage hydrolysis-resistant glass fiber reinforced PBT or the preparation method thereof, preferably in the field of low-noise, moisture-resistant environment conditions of motors in household, home appliances, office equipment or industry.

[0050] The term "and / or" herein is only to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which specifically means that A and B can exist simultaneously, A can exist alone, B can exist alone, and any one of the above three cases can exist.

[0051] The present application provides a high molecular weight polydiethylene phthalate and a preparation method thereof, and proposes a new low warping and hydrolysis resistant glass fiber reinforced PBT and a preparation method thereof, wherein the method adds inorganic fillers and then blends PBT with amorphous polymer high molecular weight polydiethylene phthalate to achieve the effect of low warping.

[0052] Experimental data show that the addition of high molecular weight polydiethylene phthalate can not only improve the tensile strength and bending strength of the PBT / high molecular weight polydiethylene phthalate blending system, but also can improve the notched impact strength of the system to a certain extent, and the shrinkage of the blending system with the addition of high molecular weight polydiethylene phthalate is reduced, and the blending system has hydrolysis resistance and obvious effect. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 The H spectrum of phthalic acid;

[0054] Figure 2 The H spectrum of polydiethylene phthalate of Example 1 of the present application;

[0055] Figure 3 The infrared spectrum of phthalic acid;

[0056] Figure 4 The infrared spectrum of polydiethylene phthalate of Example 1 of the present application.

[0057] From the infrared spectrum of polydiethylene phthalate, Figure 4 it can be seen that there is a strong C=O absorption peak at 1723cm -1 , aromatic ring skeleton absorption peaks appear at 1599cm -1 and 1651cm -1 , ether bond absorption peaks appear at 1141-1071cm -1 , CH2CH3 stretching absorption peaks appear at 2876cm -1 , ester group absorption peaks appear at 1285cm -1 , and OH absorption peaks appear at 3443cm -1 . There is no O=C-OH absorption peak, so the product synthesized has ester groups and hydroxyl groups, and no carboxyl groups, proving that the polydiethylene phthalate is successfully prepared.

[0058] From the infrared spectrum of phthalic acid, Figure 1) and the NMR H spectrum of polyethylene glycol phthalate Figure 2 ) can be seen that phthalic acid has a vibration peak of benzene ring at 7-8 ppm and COOH displacement at 13 ppm. Polyethylene glycol phthalate produces ArH signal at 7-8 ppm, C-O-C displacement at 3-0 ppm, and no COOH displacement, proving the successful preparation of polyethylene glycol phthalate. DETAILED DESCRIPTION

[0059] The present application will be described in detail below with specific examples. It is necessary to point out here that the following examples are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present application still fall within the scope of protection of the present application.

[0060] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and the values are approximate values. The endpoints of the ranges and the values can be approximated to a tolerance of ± 0.1%, or ± 1%, or ± 5%, or ± 10%, or ± 20%, or ± 50%, or ± 100%, or any other range or value as understood by one of ordinary skill in the art. For ranges of values, the endpoints of the ranges are combined with the individual points to form new ranges that are within the scope of the present application.

[0061] Source of raw materials

[0062] The raw materials used in the examples and comparative examples, if not specifically limited, are disclosed in the prior art, such as can be directly purchased or prepared according to the preparation method disclosed in the prior art.

[0063] Phthalic acid, Mcclin;

[0064] Diethylene glycol, Mcclin;

[0065] Dibutyltin dilaurate, Tianjin Fucheng Chemical Reagent Factory;

[0066] Antioxidant trimethyl phosphite, National Pharmaceutical Group Chemical Reagents (Shanghai) Co., Ltd.;

[0067] PBT, Yizheng Chemical Fiber, GX112 particles, the melt index under the test conditions of 250℃ and 2.16 kg load is 15 g / 10 min;

[0068] Glass fiber, ECS10-3.0-T436H, Taishan Glass Fiber, the single filament diameter of the glass fiber is 10 μm;

[0069] Phenolic epoxy chain extender, epoxy resin F-44, Guangzhou Taiji New Materials Co., Ltd.

[0070] Preparation of high molecular weight polyethylene glycol phthalate in Example 1

[0071] The preparation method specifically comprises the following steps:

[0072] In a 500ml three-necked flask, add diethylene glycol 84.8g (0.8.mol), phthalic acid 106.2g (0.64mol), control the temperature between 230-245℃ to carry out esterification reaction (see Table 1 for the formula and reaction parameters), observe the gas phase temperature in the system, when it is reduced to below 50℃ or the amount of water produced in the reaction reaches 60-70% of the theoretical value, add the catalyst dibutyltin dilaurate (the amount is 0.1% of the weight of phthalic acid), the antioxidant trimethyl phosphite (the amount is 0.1% of the weight of phthalic acid), slowly vacuumize to carry out polycondensation, about 40min from normal pressure to vacuum degree below 300Pa in the system, keep the temperature (240℃-250℃) and vacuum degree in the system to continue the reaction for 2 hours, after cooling to 200℃, add the phenolic epoxy chain extender with the amount of 1‰ of the weight of phthalic acid, then discharge, and high molecular weight polydiethylene glycol phthalate can be obtained, the melt index of high molecular weight polydiethylene glycol phthalate under the test condition of 160℃, 2.16kg load is 35g / 10min. The nuclear magnetic H spectrum and infrared spectrum of high molecular weight polydiethylene glycol phthalate can be seen in Figure 2 and Figure 4 . The yield of high molecular weight polydiethylene glycol phthalate can be seen in Table 1.

[0073] Comparative Example 1

[0074] The specific experimental steps of Comparative Example 1 refer to Example 1, and the only difference from Example 1 is that four different reaction temperatures (190℃, 210℃, 260℃, 270℃) are used, and four experiments are independently carried out respectively. See Table 1 for the specific ratio and parameters.

[0075] Table 1 Formula and reaction parameters of Example 1 and Comparative Example 1

[0076]

[0077] It can be seen that the reaction temperature has a great influence on the preparation product, and diethylene glycol phthalate can be obtained above 230℃, the yield is the highest at 230-245℃, and the yield begins to decrease if it exceeds 245℃. Therefore, the reaction is determined to be carried out between 230-245℃.

[0078] Comparative Example 2

[0079] The specific experimental steps for Comparative Example 2 are the same as those for Example 1. The only difference between Comparative Example 2 and Example 1 is that the reactants are different. Specifically, diethylene glycol is replaced with three different reactants (ethylene glycol, butanediol, and 1,3-propanediol), and each experiment is conducted independently three times. The specific ratios and parameters are shown in Table 2.

[0080] Table 2. Formulation and reaction parameters of Comparative Example 2

[0081]

[0082] As shown in Table 2, different alcohols (such as ethylene glycol, butanediol, and 1,3-propanediol) have different effects on the synthesis of phthalates. The highest yield is only 74%, which is significantly lower than the 92% yield when diethylene glycol was used as a reactant in Example 1 of this invention. Therefore, this invention selects diethylene glycol as the preferred alcohol because it has a high yield, good effect, and low price (1,3-propanediol is 26,000 yuan / ton, and diethylene glycol is 3,500-5,000 yuan / ton).

[0083] Examples 2-5: Preparation and performance testing of low-warpage and hydrolysis-resistant glass fiber reinforced PBT

[0084] The components, including PBT and high molecular weight poly(diethylene phthalate), were mixed according to the formula ratio (see Table 3). After uniform mixing, mica (passed through an 800-mesh sieve) and trimethyl phosphite were added and mixed. The mixture was then granulated with glass fiber using a twin-screw extruder at 230-270℃ (later stage (230-250℃), middle stage (240-260℃), and earlier stage (250-270℃)). The granulated material was then dried at 120℃ for 4 hours and injection molded into standard test strips for performance testing. The test results are shown in Table 4.

[0085] The test items and standards are as follows:

[0086] 1) Tensile strength: GB / T 1040-2006 (speed: 10mm / min);

[0087] 2) Bending strength: GB / T 9341-2008 (speed: 2mm / min);

[0088] 3) Notched impact strength (room temperature): GB / T 1043-2008.

[0089] Comparative Example 3

[0090] The preparation and testing methods for this comparative example are the same as those in Example 2, except that the amount of components is different and high molecular weight poly(diethylene phthalate) was not added. The specific component formulation ratios are shown in Table 3, and the test results are shown in Table 4.

[0091] Comparative Example 4

[0092] The preparation and testing methods for this comparative example are the same as in Example 3, except that low molecular weight diethylene phthalate is used instead of high molecular weight polyethylene phthalate. The specific component ratios are shown in Table 3, and the test results are shown in Table 4.

[0093] The method for preparing low molecular weight diethylene glycol phthalate includes the following steps: In a 500ml three-necked flask, add 84.8g (0.8mol) of diethylene glycol, 106.2g (0.64mol) of phthalic acid, and dibutyltin dilaurate (0.1% of the weight of phthalic acid). Heat to 230℃ and stir for 2 hours. Remove the generated water using a water separator. Continue the reaction for 1 hour without vacuuming, then directly cool and discharge to obtain low molecular weight diethylene glycol phthalate. Under test conditions of 160℃ and 2.16kg load, the melt index of the prepared low molecular weight diethylene glycol phthalate is 60g / 10min.

[0094] Following the preparation and testing methods of Example 3, the low molecular weight diethylene phthalate (DEP) was blended with PBT and other components, and its mechanical properties were tested. Specific components and formulation ratios are shown in Table 3, and the test results are shown in Table 4. Compared with Example 3, it can be seen that the performance of the blend of low molecular weight DEP and PBT is inferior to that of the blend of high molecular weight DEP and PBT.

[0095] Comparative Example 5

[0096] The preparation and testing methods for this comparative example are the same as in Example 3, except that polycarbonate (Covestro 2405) is used instead of high molecular weight poly(diethylene phthalate). Specific components and formulation ratios are shown in Table 3, and test results are shown in Table 4.

[0097] Example 6

[0098] The preparation of high molecular weight poly(diethylene phthalate) without the addition of a chain extender is described in Example 1, with the specific formulation and reaction parameters as described above. The only difference is the absence of a chain extender. Specific steps may include:

[0099] In a 500ml three-necked flask, add 84.8g (0.8mol) of diethylene glycol and 106.2g (0.64mol) of phthalic acid. Control the temperature between 230-245℃ for esterification. Observe the gas phase temperature within the system. When the temperature drops below 50℃ or the amount of water produced reaches the theoretical 60-70%, add the catalyst dibutyltin dilaurate (0.1% of the weight of phthalic acid) and the antioxidant trimethyl phosphite (0.1% of the weight of phthalic acid). The mixture was slowly evacuated under vacuum for about 40 minutes until the vacuum level in the system was below 300 Pa. The temperature (240℃-250℃) and vacuum level in the system were maintained for another 2 hours. After cooling to 200℃, the mixture was discharged to obtain high molecular weight poly(diethylene phthalate) without the addition of chain extender. Under the test conditions of 160℃ and 2.16 kg load, the melt index of the high molecular weight poly(diethylene phthalate) without the addition of chain extender was 45 g / 10 min.

[0100] High molecular weight poly(diethylene phthalate) prepared without chain extenders was blended with PBT and other components. The preparation and testing methods were the same as in Example 3, except that no chain extenders were added during the preparation of the high molecular weight poly(diethylene phthalate). Specific components and formulation ratios are shown in Table 3, and mechanical test results are shown in Table 4.

[0101] Table 3 shows the formulation ratios of Examples 2-6 and Comparative Examples 3-5 (ratios are by weight).

[0102]

[0103]

[0104] Table 4. Product test performance of Examples 2-6 and Comparative Examples 3-5

[0105]

[0106] The experimental results show that adding low molecular weight diethylene glycol phthalate significantly reduces the mechanical properties of the system; the mechanical properties of polycarbonate are comparable to those of high molecular weight diethylene glycol phthalate; when high molecular weight diethylene glycol phthalate is added (Examples 2-5), as the proportion of high molecular weight diethylene glycol phthalate in the system gradually increases from 0%, 5%, 7%, 10%, and 15%, the mechanical properties of the system first increase and then decrease, and the mechanical properties are best when the proportion of high molecular weight diethylene glycol phthalate increases to 7%.

[0107] Example 7 Shrinkage Test

[0108] This embodiment investigates the shrinkage of the PBT / high molecular weight poly(diethylene phthalate) system under different mixing ratios.

[0109] Particles from Examples 2-6 and Comparative Examples 3 and 5 were used to prepare specimens using consistent process parameters and square plastic parts with equal wall thickness (length 60±2mm, width 60±2mm, thickness 2.0±0.1mm). Ten specimens were prepared for each type of particle material.

[0110] Take 10 samples of the same material and measure them with vernier calipers at 23±2℃, accurate to 0.025mm. After taking the average value, represent the longitudinal and transverse directions with Z and W respectively, and calculate the longitudinal and transverse shrinkage rates and the longitudinal and transverse shrinkage ratio according to the formula.

[0111] S z =[(Z m -Z s ) / Z m ]*100%

[0112] In the formula, S z Z represents the shrinkage rate (%) in the longitudinal direction; m Z represents the longitudinal width of the mold (mm); s

[0113] The average longitudinal width of the specimen (mm);

[0114] S w =[(W m -W s ) / W m ]*100%

[0115] In the formula, S w W represents the lateral shrinkage rate (%); m Represents the lateral width of the mold (mm);

[0116] W s The average transverse width of the specimen (mm)

[0117] P = S z -S w

[0118] In the formula, P represents the difference between the longitudinal and transverse shrinkage rates.

[0119] The shrinkage test results of Examples 2-6 (with added high molecular weight poly(diethylene phthalate)) and Comparative Examples 3 and 5 (with added polycarbonate system) are shown in Table 5.

[0120] Table 5

[0121]

[0122] As can be seen from Comparative Example 5 in Table 5, the effect of amorphous polymer polycarbonate in reducing warpage is significantly less than that of the high molecular weight poly(diethylene phthalate) prepared in this invention.

[0123] As shown in Table 5 and Example 6, the warpage reduction effect of the high molecular weight poly(diethylene phthalate) prepared without chain extender is comparable to that of the high molecular weight poly(diethylene phthalate) prepared with chain extender, and both have a significant effect on reducing warpage.

[0124] As shown in Table 5, with the increase of high molecular weight poly(diethylene glycol) phthalate content, the difference in longitudinal and transverse shrinkage rates of the blend system first decreased and then increased, both showing a significant reduction in warpage compared to pure PBT. Among them, the system in Example 3 exhibited the best shrinkage uniformity. The preceding analysis indicates that the longitudinal and transverse shrinkage rates of the system with added high molecular weight poly(diethylene glycol) phthalate are lower than those of pure PBT. This is because PBT molecular chains, lacking side chains, are prone to stacking and entanglement, resulting in high crystallinity. However, high molecular weight poly(diethylene glycol) phthalate is ortho-substituted, and compared to para-substituted PBT, its molecular chain arrangement regularity is significantly reduced. This structural characteristic hinders the orderly stacking of molecular chains, making it unfavorable for forming a long-range ordered crystalline structure. Adding it can prevent the PBT molecular chains from entangled, thereby inhibiting PBT crystallization.

[0125] Example 8: Boiling Test

[0126] In this embodiment, the standard samples from Examples 3 and 6 were boiled in water (20 hours, 65°C), and then their performance was tested. The test results are shown in Table 6 below.

[0127] Table 6

[0128]

[0129] As shown in Table 6, after a 20-hour boiling test at 65℃, the high molecular weight poly(diethylene phthalate) prepared with added chain extender, when blended with PBT (Example 3), exhibited better hydrolysis resistance due to the high molecular weight of the poly(diethylene phthalate) being a non-low molecular weight ester. The chain extender further increased the polymer molecular weight, resulting in better compatibility with PBT. The tensile strength and flexural strength of the composite material retained over 93%, and the difference in longitudinal and transverse shrinkage after the boiling test was 0.26. The high molecular weight poly(diethylene phthalate) prepared without added chain extender, when blended with PBT (Example 6), showed no change in shrinkage or warpage due to the addition of the chain extender, and retained 76% of its mechanical properties. It exhibited some hydrolysis resistance, but not as good as in Example 3. For applications requiring hydrolysis resistance, such as humid environments, chain extenders can be further added to the synthesis method of high molecular weight poly(diethylene phthalate) to further improve hydrolysis resistance and applicability.

Claims

1. A high molecular weight poly(diethylene phthalate), characterized in that, It has the structure shown in equation (I): Preferably, the high molecular weight poly(diethylene glycol phthalate) has a melt index of ≤50g / 10min under test conditions of 160℃ and 2.16kg load, more preferably 10~45g / 10min.

2. The method for preparing high molecular weight poly(diethylene phthalate) ester according to claim 1, characterized in that... Includes the following steps: Diethylene glycol and phthalic acid were subjected to esterification reaction, followed by vacuum polycondensation to obtain high molecular weight poly(diethylene phthalate).

3. The method for preparing high molecular weight poly(diethylene phthalate) ester according to claim 2, characterized in that... Includes the following steps: Diethylene glycol and phthalic acid are subjected to an esterification reaction. After the esterification reaction is completed, components including a catalyst and an antioxidant are added, and the mixture is subjected to condensation under vacuum. The temperature and vacuum level in the system are maintained to continue the reaction. Preferably, a chain extender is added to obtain high molecular weight poly(diethylene phthalate). Preferably, the reaction is continued for 1 to 3 hours. Preferably, the vacuum level is below 300 Pa. Preferably, the esterification reaction ends when one of the following two phenomena occurs: 1) The gas phase temperature in the reaction system drops below 50°C; and / or, 2) When the reaction output reaches 60% to 70% of the theoretical value; in, Preferably, the molar ratio of diethylene glycol to phthalic acid is 1.6:(1-0.5), more preferably 1: (0.6～0.9)； Preferably, the esterification reaction temperature is between 230 and 245°C; Preferably, the temperature inside the system is maintained at 240°C to 250°C.

4. The method for preparing high molecular weight poly(diethylene phthalate) ester according to claim 3, characterized in that: The chain extender is a phenolic epoxy chain extender; Preferably, the amount of the chain extender is 1 to 5‰ of the weight of phthalic acid; Preferably, the catalyst is selected from one or more of dibutyltin dilaurate, triethyl phosphate, and tetrabutyl titanate, and is more preferably dibutyltin dilaurate; the amount of the catalyst is 0.1 to 0.5 wt% of the weight of phthalic acid; and / or, Preferably, the antioxidant is selected from one or more of trimethyl phosphite and triethyl phosphate; the amount of the antioxidant is 0.1 to 0.5 wt% of the weight of phthalic acid.

5. The high molecular weight poly(diethylene glycol phthalate) obtained by the method for preparing high molecular weight poly(diethylene glycol phthalate) according to any one of claims 2 to 4.

6. A low-warpage, hydrolysis-resistant glass fiber reinforced PBT comprising the high molecular weight poly(diethylene phthalate) as described in claim 1 or 5, characterized in that... It comprises PBT, the high molecular weight poly(diethylene phthalate), inorganic fillers, and glass fiber; Preferably, Based on 100% of the total weight of the low-warpage and hydrolysis-resistant glass fiber reinforced PBT, it comprises the following blended components by weight percentage:

7. The low-warpage, hydrolysis-resistant glass fiber reinforced PBT according to claim 6, characterized in that: The inorganic filler is selected from one or more of mica, calcium sulfate whiskers, and talc. Preferably, the mica is passed through an 800-mesh sieve; And / or, The average monofilament diameter of the glass fiber is 5–20 μm; and / or, The melt flow index of the PBT under test conditions of 250℃ and 2.16kg load is 10~40g / 10min.

8. The method for preparing low-warpage, hydrolysis-resistant glass fiber reinforced PBT according to any one of claims 5 to 7, characterized in that... Includes the following steps: The components, including PBT, high molecular weight poly(diethylene phthalate), inorganic fillers, and optional antioxidants, are mixed, extruded and granulated with glass fiber, and dried to obtain the low warp and hydrolysis resistant glass fiber reinforced PBT. A twin-screw extruder is preferred for extrusion granulation; The preferred extrusion granulation temperature is 230–270°C; The preferred drying method is to dry at 100-120℃ for 3-5 hours.

9. The low-warpage, hydrolysis-resistant glass fiber reinforced PBT obtained by the preparation method of the low-warpage, hydrolysis-resistant glass fiber reinforced PBT according to claim 8.

10. The application of the high molecular weight poly(diethylene phthalate) according to claim 1 or 4, or the preparation method according to claim 2 or 3, or the low warpage and hydrolysis resistant glass fiber reinforced PBT according to any one of claims 5 to 7, 9, or the preparation method according to claim 8, preferably in the field of motors for low noise and humid environments in home furnishings, home appliances, office equipment, or industry.

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