Toughened polyester and preparation method thereof

Abstract

The invention provides toughened polyester and a preparation method thereof, and belongs to the technical field of high polymer materials, the toughened polyester is obtained by polymerizing terephthalic acid, ethylene glycol, pentaerythritol and dihydroxy-terminated / diamino-terminated silicon oil, the pentaerythritol accounts for 0.05-1% of the mass of terephthalic acid, the dihydroxy-terminated / diamino-terminated silicon oil accounts for 0.05-1% of the mass of dihydroxy-terminated / diamino-terminated silicon oil, and the dihydroxy-terminated / diamino-terminated silicon oil accounts for 0.05- the double-terminal hydroxyl / double-terminal amino silicon oil accounts for 1-40% of the mass of terephthalic acid, and the double-terminal hydroxyl / double-terminal amino silicon oil is hydroxyl silicon oil, amino-terminated silicon oil or hydroxypropyl-terminated silicon oil. According to the invention, pentaerythritol and high-proportion dihydroxyl-terminated / diamino-terminated silicone oil are introduced at the same time, and the loss of melt strength and molecular chain mechanical strength of the polyester material is made up by utilizing the mutual cooperation of the moderate crosslinking effect of pentaerythritol and the flexible toughening effect of silicone oil, so that the polyester material has spinnability while the toughness of the polyester material is improved, and the polyester material has good mechanical properties. And the fabric spun from the toughened polyester is smooth in hand feeling. When the toughened polyester provided by the invention is used for the vamp material, the bending resistance of the vamp can also be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a toughened polyester and a preparation method thereof. Background Art

[0002] Polyester has high strength, chemical resistance and easy processability, and is widely used in the textile field. However, the inherent brittleness and insufficient toughness of polyester limit its further expansion in high-end fields such as sports shoes and clothing, flexible electronics, and medical devices.

[0003] Common toughening and modification strategies in the prior art include blending / compounding modification or copolymerization modification. Blending / compounding modification refers to introducing masterbatches with toughening functions (such as nylon, PBT, PTT, etc.) to improve the toughness of polyester materials. However, the amplitude of improving toughness by using this method is limited, and technical problems such as uneven dispersion of fillers are prone to occur during the blending / compounding process. In addition, phase separation is prone to occur in the multiphase system existing in the modified polyester, affecting the uniformity of dyeing. Copolymerization modification refers to introducing monomers such as polyethers for copolymerization to improve the toughness of polyester materials. However, adding a large amount of polyether monomers will significantly reduce the viscosity of the polyester melt, seriously affecting the spinnability of the polyester melt, and too low addition amount of polyether cannot endow the polyester with sufficient toughness.

[0004] In view of this, it is necessary to design a toughened polyester and a preparation method thereof to solve the above problems. Summary of the Invention

[0005] In view of the technical problem of poor toughness of polyester materials in the background art, the present application provides a toughened polyester and a preparation method thereof. The toughened polyester is obtained by polymerizing terephthalic acid, ethylene glycol, pentaerythritol, and bis-hydroxy / amino-terminated silicone oil. The toughness of the polyester is improved by the synergistic effect of pentaerythritol and silicone oil. When the dosage of the flexible silicone oil monomer is between 15-30%, and the dosage of pentaerythritol is between 0.05-0.25%, the elongation at break of the toughened polyester is 30-70%, and the yield strength is 50-70 MPa. At this time, the toughened polyester has spinnability, and the spun fibers or fabrics have a smooth hand feeling.

[0006] In the first aspect, an embodiment of the present application provides a toughened polyester, which is obtained by polymerizing terephthalic acid, ethylene glycol, pentaerythritol, and bis-hydroxy / amino-terminated silicone oil, and the toughened polyester has spinnability; wherein, the pentaerythritol accounts for 0.05-1% of the mass of the terephthalic acid, and the bis-hydroxy / amino-terminated silicone oil accounts for 1-40% of the mass of the terephthalic acid; the bis-hydroxy / amino-terminated silicone oil is hydroxy silicone oil, aminopropyl-terminated silicone oil or hydroxypropyl-terminated silicone oil, and the corresponding structural general formula of the toughened polyester is A, B or C, where

[0007] A is

[0008] B is

[0009] C is

[0010] and 1 ≤ m ≤ 2, 100 ≤ n ≤ 200, 1 ≤ o ≤ 40, 1 ≤ p ≤ 2, 10 ≤ q ≤ 100.

[0011] Furthermore, the number-average molecular weight of the hydroxy silicone oil is between 1000 and 8000; the number-average molecular weight of the amino-terminated silicone oil is between 1000 and 8000; the number-average molecular weight of the hydroxypropyl-terminated silicone oil is between 1000 and 8000.

[0012] Furthermore, the molar ratio of terephthalic acid to ethylene glycol is 1:(1.2 - 1.6); the pentaerythritol accounts for 0.05 - 0.25% of the mass of terephthalic acid, and the double-terminal hydroxy / double-terminal amino silicone oil accounts for 15 - 30% of the mass of terephthalic acid. At this time, the elongation at break of the toughened polyester is 30 - 70%, and the yield strength is 50 - 70 MPa.

[0013] In a second aspect, the embodiments of the present application provide a method for preparing a toughened polyester, including the following steps:

[0014] S1. Open the valve between the first condenser and the reaction kettle, put terephthalic acid and ethylene glycol into the reaction kettle, then add the catalyst Sb2O3, raise the temperature of the reaction kettle to 250 - 260 °C under a nitrogen atmosphere and a pressure of 100 - 105 kPa, and carry out an esterification reaction at a stirring frequency of 30 Hz. The by-product water generated during the reaction flows out from the rear end of the first condenser. When the water output reaches the theoretically calculated value, the esterification reaction ends.

[0015] S2. After the esterification reaction ends, put pentaerythritol and double-terminal hydroxy / double-terminal amino silicone oil into the reaction kettle and react at normal pressure for 0.5 - 1 h.

[0016] S3. Close the valve between the first condenser and the reaction kettle, raise the temperature of the reaction kettle to 260 - 280 °C, and open the valve between the second condenser and the reaction kettle to carry out a polycondensation reaction. First, control the vacuum degree in the reaction kettle to drop to a vacuum state through a vacuum fine-tuning valve during the reaction, and then continue the polycondensation for 1 - 2 h at a stirring frequency of 25 - 50 Hz. After the reaction ends, discharge the material from the bottom of the reaction kettle and pelletize to obtain the toughened polyester.

[0017] Further, in step S2, the dihydroxy / diamino silicone oil is hydroxy silicone oil, aminopropyl-terminated silicone oil or hydroxypropyl-terminated silicone oil; in step S2, the dosage of the dihydroxy / diamino silicone oil is 1-40% of the mass of terephthalic acid in step S1; in step S2, the dosage of pentaerythritol is 0.05-1% of the mass of terephthalic acid in step S1.

[0018] Further, in step S1, the molar ratio of terephthalic acid to ethylene glycol is 1:

[0019] (1.2-1.6), and the dosage of the catalyst Sb2O3 based on the dosage of terephthalic acid is 400-600 ppm.

[0020] Further, in step S3, continuing the polycondensation for 1-2 h at a stirring frequency of 25-50 Hz means first reacting at a stirring frequency of 50 Hz for 0.5-1 h, and then reacting at a stirring frequency of 25 Hz for 0.5-1 h.

[0021] Further, in step S2, pentaerythritol accounts for 0.05-0.25% of the mass of terephthalic acid, and the dihydroxy / diamino silicone oil accounts for 15-30% of the mass of terephthalic acid.

[0022] Further, in steps S1 and S2, the temperature of the first condenser is set at 145-150 °C; in step S1, the pressure of the esterification reaction is controlled within 360 kPa.

[0023] Further, in step S3, the temperature of the second condenser is set at 20-30 °C; in step S3, the reduction rate of the vacuum degree in the reaction kettle is 20 kPa / 10 min.

[0024] The beneficial effects of this application are as follows:

[0025] This application provides a toughened polyester and its preparation method. The toughened polyester is obtained by polymerizing terephthalic acid, ethylene glycol, pentaerythritol, and dihydroxy / diamino silicone oil. Among them, pentaerythritol accounts for 0.05-1% of the mass of terephthalic acid, preferably 0.05-0.25%; the dihydroxy / diamino silicone oil accounts for 1-40% of the mass of terephthalic acid, preferably 15-30%; the dihydroxy / diamino silicone oil is hydroxy silicone oil, aminopropyl silicone-terminated oil or hydroxypropyl-terminated silicone oil.

[0026] When the dosage of the flexible silicone monomer is between 15-30% and the dosage of pentaerythritol is between 0.05-0.25%, the elongation at break of the toughened polyester is 30-70%, and the yield strength is 50-70 MPa. At this time, the toughened polyester has spinnability, and the spun fiber or fabric has a smooth hand feeling.

[0027] In this application, pentaerythritol and a high proportion of dihydroxy / diamino silicone oil are introduced simultaneously. The synergistic effect of pentaerythritol and silicone oil is utilized to improve the toughness of polyester. The flexible silicone monomer can not only make the polyester fabric feel smooth, but also improve the flexibility of polyester. However, too many flexible chains will lead to a decrease in the melt strength and the mechanical strength of the molecular chain of the polyester material. Pentaerythritol can form a crosslinked network structure in the molecular chain of polyester. When the toughening effect of the flexible silicone monomer and the crosslinking effect of pentaerythritol work together, the loss of melt strength and the mechanical strength of the molecular chain can be compensated, and the toughness of the polyester material can be improved while maintaining spinnability.

[0028] The toughened polyester provided by this application can be used not only in the field of textile and clothing, but also in the preparation of products such as shoe upper materials, false eyelashes, and toothbrush bristles. Among them, when used in shoe upper materials, the bending resistance of the shoe upper can be improved.

[0029] The above description is only an overview of the technical solution of this application. In order to be able to understand the technical means of this application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of this application more obvious and understandable, the specific embodiments of this application are given below. Brief Description of the Drawings

[0030] In order to more clearly illustrate the technical solution of this application, the drawings used in this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 is the general structural formula of the toughened polyester provided by this application. Among them, A is prepared from hydroxy silicone oil, B is prepared from amino propyl terminated silicone oil, and C is prepared from hydroxy propyl terminated silicone oil;

[0032] Figure 2 is the tensile stress-strain curve diagram of the polyester prepared in Examples 1-5 and Comparative Examples 1-3 of this application. Detailed Description of the Embodiments

[0033] The embodiments of the technical solution of this application will be described in detail below with reference to the drawings. The following embodiments are only used to illustrate the technical solution of this application more clearly, so they are only examples and cannot be used to limit the protection scope of this application.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs; the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "comprising" and "having" and any variations thereof in the specification and claims of this application and the above description of the drawings are intended to cover non-exclusive inclusion.

[0035] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, "a plurality of" means more than two unless otherwise specifically defined.

[0036] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase does not necessarily refer to the same embodiment when it appears in various positions in the specification, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0037] In the description of the embodiments of this application, the term "and / or" is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0038] In the prior art, the improvement in toughness by blending / composite modification is limited, and the filler is unevenly dispersed, resulting in poor dyeing uniformity of the modified polyester; in copolymer modification, too much introduction of polyether monomers will affect the spinnability of the polyester melt, and too little will cause insufficient toughness of the material.

[0039] To solve the technical problem of poor toughness of polyester materials, this application provides a toughened polyester and its preparation method. Pentaerythritol and a high proportion of double-terminal hydroxyl / double-terminal amino groups are simultaneously introduced into polyethylene terephthalate. The two act synergistically to significantly improve the toughness of the polyester and ensure that the toughened polyester has spinnability.

[0040] Please refer to Figure 1, In a first aspect, an embodiment of the present application provides a toughened polyester obtained by polymerizing terephthalic acid, ethylene glycol, pentaerythritol, and a dihydroxy / diamino silicone oil. Among them, the molar ratio of terephthalic acid to ethylene glycol is 1:(1.2 - 1.6), pentaerythritol accounts for 0.05 - 1% of the mass of terephthalic acid, and the dihydroxy / diamino silicone oil accounts for 1 - 40% of the mass of terephthalic acid. Preferably, pentaerythritol accounts for 0.05 - 0.25% of the mass of terephthalic acid, and the dihydroxy / diamino silicone oil accounts for 15 - 30% of the mass of terephthalic acid.

[0041] In the embodiment of the present application, the dihydroxy / diamino silicone oil is a hydroxy silicone oil, an aminopropyl-terminated silicone oil, or a hydroxypropyl-terminated silicone oil, and the corresponding structural general formulas of the toughened polyester obtained are A, B, or C.

[0042] A is

[0043] B is

[0044] C is

[0045] And 1 ≤ m ≤ 2, 100 ≤ n ≤ 200, 1 ≤ o ≤ 40, 1 ≤ p ≤ 2, 10 ≤ q ≤ 100.

[0046] Among them, the number-average molecular weight of the hydroxy silicone oil is between 1000 - 8000, the number-average molecular weight of the amino-terminated silicone oil is between 1000 - 8000, and the number-average molecular weight of the hydroxypropyl-terminated silicone oil is between 1000 - 8000.

[0047] The toughened polyester provided by the present application has spinnability. When pentaerythritol accounts for 0.05 - 0.25% of the mass of terephthalic acid, and the dihydroxy / diamino silicone oil accounts for 15 - 30% of the mass of terephthalic acid, the elongation at break of the toughened polyester is 30 - 70%, and the yield strength is 50 - 70 MPa.

[0048] In a second aspect, an embodiment of the present application provides a method for preparing a toughened polyester, including the following steps:

[0049] S1, Open the valve between the first condenser and the reaction kettle, put terephthalic acid and ethylene glycol into the reaction kettle, then add the catalyst Sb2O3, raise the temperature of the reaction kettle to 250 - 260°C under a nitrogen atmosphere and a pressure of 100 - 105 kPa, and carry out an esterification reaction at a stirring frequency of 30 Hz. The by-product water generated during the reaction flows out from the rear end of the first condenser. When the water output reaches the theoretically calculated value, the esterification reaction ends.

[0050] In the embodiment of the present application, in step S1, the molar ratio of terephthalic acid to ethylene glycol is 1:(1.2 - 1.6).

[0051] In the embodiment of the present application, in step S1, the dosage of the catalyst Sb2O3 is calculated based on the mass of terephthalic acid and is 400-600 ppm.

[0052] In the embodiment of the present application, in step S1, the temperature of the first condenser is set to 145-150 °C, so that the evaporated ethylene glycol in the reaction is condensed and refluxed. At the same time, the water generated in the reaction is evaporated and discharged.

[0053] In the embodiment of the present application, as the temperature rises, the pressure in the reaction kettle also continuously increases, and the pressure of the esterification reaction is controlled within 360 kPa. During the reaction, when water droplets drip out from the rear end of the first condenser, the pressure is relieved to ensure that the by-product water in the esterification reaction is fully distilled out, promoting the progress of the esterification reaction.

[0054] S2, after the esterification reaction is completed, pentaerythritol and dihydroxy / diamino silicone oil are put into the reaction kettle and reacted at normal pressure for 0.5-1 h.

[0055] In the embodiment of the present application, in step S2, the temperature of the first condenser is set to 145-150 °C.

[0056] In the embodiment of the present application, in step S2, the dosage of pentaerythritol is 0.05-1% of the mass of terephthalic acid in step S1, preferably 0.05-0.25%.

[0057] In the embodiment of the present application, in step S2, the dihydroxy / diamino silicone oil is hydroxy silicone oil, amino propyl terminated silicone oil or hydroxy propyl terminated silicone oil, preferably hydroxy silicone oil or amino propyl terminated silicone oil. The dosage of the dihydroxy / diamino silicone oil is 1-40% of the mass of terephthalic acid in step S1, preferably 15-30%, and further preferably 30%.

[0058] S3, close the valve between the first condenser and the reaction kettle, raise the temperature of the reaction kettle to 260-280 °C, and open the valve between the second condenser and the reaction kettle to carry out a polycondensation reaction. During the reaction, first control the vacuum degree in the reaction kettle to drop to a vacuum state through a vacuum fine adjustment valve, and then continue the polycondensation for 1-2 h at a stirring frequency of 25-50 Hz. After the reaction is completed, the material is discharged from the bottom of the reaction kettle and pelletized to obtain toughened polyester.

[0059] In the embodiment of the present application, in step S3, the temperature of the second condenser is set to 20-30 °C to condense and recover the low-boiling substances distilled under vacuum.

[0060] The reduction rate of the vacuum degree in the reaction kettle is 20 kPa / 10 min.

[0061] In the embodiments of the present application, continuing the polycondensation for 1 - 2 h at a stirring frequency of 25 - 50 Hz means first reacting at a stirring frequency of 50 Hz for 0.5 - 1 h, and then reacting at a stirring frequency of 25 Hz for 0.5 - 1 h. As the polycondensation reaction proceeds, the viscosity of the material gradually increases. Adjusting the frequency can avoid the phenomenon of spraying and kettle blocking caused by the rapid increase in viscosity.

[0062] The present application simultaneously introduces pentaerythritol and a high - proportion of di - terminal - hydroxyl / di - terminal - amino silicone oil, and utilizes the synergistic effect of pentaerythritol and silicone oil to improve the toughness of polyester. The flexible silicone monomer can not only make the polyester fabric feel smooth, but also improve the flexibility of polyester. However, too many flexible chains will lead to a decrease in the melt strength and the mechanical strength of the molecular chain of the polyester material. Pentaerythritol can form a cross - linked network structure in the molecular chain of polyester. When the toughening effect of the flexible silicone monomer and the cross - linking effect of pentaerythritol cooperate with each other, it can make up for the loss of melt strength and molecular chain mechanical strength, and improve the toughness of the polyester material while having spinnability.

[0063] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those technologies or conditions not specified in the embodiments, they shall be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications. For the reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0064] Example 1

[0065] Example 1 provides a method for preparing toughened polyester, which includes the following steps:

[0066] S1, after checking the tightness of the reaction kettle, open the valve between the first condenser and the reaction kettle, put terephthalic acid and ethylene glycol into the reaction kettle according to a molar ratio of 1:1.4, then add 500 ppm of catalyst (Sb2O3), raise the temperature of the reaction kettle to 260 °C under the condition of a nitrogen atmosphere and a pressure of 100 kPa, set the temperature of the first condenser to 150 °C, and carry out the esterification reaction at a stirring frequency of 30 Hz. The way of introducing nitrogen into the reaction kettle is as follows: first introduce nitrogen until the pressure reaches 120 kPa, open the valve to release the pressure to atmospheric pressure, then close the valve and continue to introduce nitrogen, open the valve to release the pressure to atmospheric pressure, repeat the above operation until the air in the reaction kettle is emptied, and finally introduce nitrogen until the pressure reaches 100 kPa. In the esterification reaction, the pressure of the reaction kettle will increase with the increase in temperature, and the pressure of the reaction kettle needs to be controlled within 360 kPa. The by - product water generated in the esterification reaction flows out from the back end of the first condenser. When water droplets drip out from the back end of the first condenser, start to relieve the pressure. When the water output reaches the theoretically calculated value, the esterification reaction ends.

[0067] S2. After the esterification reaction is completed, pentaerythritol and hydroxyl silicone oil are introduced into the reaction kettle from the feeding port and reacted under normal pressure for 0.5 h. The dosage of pentaerythritol is 0.1% of the mass of terephthalic acid in step S1, and the dosage of hydroxyl silicone oil is 30% of the mass of terephthalic acid in step S1.

[0068] S3. Close the valve between the first condenser and the reaction kettle, turn off the heating switch of the first condenser, raise the temperature of the reaction kettle to 280 °C, set the temperature of the second condenser to 25 °C, and open the valve between the second condenser and the reaction kettle to carry out polycondensation reaction. During the reaction, first control the vacuum degree in the reaction kettle through the vacuum fine-tuning valve to decrease to the vacuum state at a rate of 20 kPa / 10 min, then react for 1 h at a stirring frequency of 50 Hz, and then react for 1 h at a stirring frequency of 25 Hz. After the reaction is completed, discharge the material from the bottom of the reaction kettle, pelletize, and obtain toughened polyester.

[0069] Example 2

[0070] The difference between Example 2 and Example 1 is that in step S2, the dosage of hydroxyl silicone oil is 20% of the mass of terephthalic acid in step S1. Others are the same as in Example 1 and will not be elaborated here.

[0071] Example 3

[0072] The difference between Example 3 and Example 1 is that the dosage of hydroxyl silicone oil is 15% of the mass of terephthalic acid in step S1. Others are the same as in Example 1 and will not be elaborated here.

[0073] Example 4

[0074] The difference between Example 4 and Example 1 is that in step S2, the double-ended hydroxyl / double-ended amino silicone oil is an aminopropyl-terminated silicone oil, and the dosage of the amino-terminated silicone oil is 30% of the mass of terephthalic acid in step S1. Others are the same as in Example 1 and will not be elaborated here.

[0075] Example 5

[0076] The difference between Example 5 and Example 1 is that in step S2, the double-ended hydroxyl / double-ended amino silicone oil is a hydroxypropyl-terminated silicone oil, and the dosage of the hydroxypropyl-terminated silicone oil is 30% of the mass of terephthalic acid in step S1. Others are the same as in Example 1 and will not be elaborated here.

[0077] Comparative Example 1

[0078] The difference between Comparative Example 1 and Example 1 is that step S2 is deleted. Others are the same as in Example 1 and will not be elaborated here. The product prepared in Comparative Example 1 is a conventional polyester.

[0079] Comparative Example 2

[0080] The difference between Comparative Example 2 and Example 1 is that in step S2, only pentaerythritol is added, and the amount of pentaerythritol is 0.1% of the mass of terephthalic acid in step S1. Others are the same as in Example 1 and will not be elaborated here.

[0081] Comparative Example 3

[0082] The difference between Comparative Example 3 and Example 1 is that in step S2, only hydroxy silicone oil is added, and the amount of hydroxy silicone oil is 30% of the mass of terephthalic acid in step S1. Others are the same as in Example 1 and will not be elaborated here.

[0083] The toughened polyesters prepared in Examples 1-5 and Comparative Examples 1-3 were respectively made into samples with dimensions of 40 mm×5 mm×2 mm, and the toughness of the samples was tested according to the standard GB / T 1040.2-2006 using an Instron electronic tensile testing machine. During the test, the samples were stretched at a rate of 5 mm / min, and each sample was measured 5 times and the average value was taken. The tensile stress-strain curve of the polyester is shown in Figure 2 as follows.

[0084] It can be seen that the elongation at break of Examples 1-3 is between 30% and 50%, and the yield strength is 50-70 MPa, which is significantly better than that of Comparative Examples 1-3 without adding functional monomers or adding only one functional monomer, and the toughening effect of Example 1 is the best. This is because adding only pentaerythritol will form a cross-linked network structure in the molecular chain of the polyester, making the polyester material slightly rigid and resulting in a decrease in the elongation at break; adding only silicone oil can improve the toughness of the polyester material to some extent, but the strength of the material is still insufficient. Therefore, only by adding pentaerythritol and silicone oil simultaneously and their synergistic effect can the tensile properties of the polyester material be effectively improved and the toughening effect be achieved. The amount of silicone oil is preferably 15-30% of the mass of terephthalic acid, and more preferably 30%.

[0085] The toughened polyester of Example 4 shows more excellent toughness than that of Example 1, with an elongation at break greater than 60% and a yield strength between 60-70 MPa. The elongation at break of the toughened polyester of Example 5 is relatively low, which may be due to the thermal decomposition of part of the hydroxypropyl-terminated silicone oil at high temperature during the preparation of the toughened polyester, resulting in partial influence on the performance of the finally obtained toughened polyester. Therefore, the silicone oil is preferably hydroxy silicone oil or aminopropyl-terminated silicone oil.

[0086] Application Example

[0087] The toughened polyesters prepared in Examples 1-3 were used for melt spinning, including the following steps: The polyester materials prepared in Examples 1-3 and Comparative Example 1 after slicing and sufficient drying were respectively mixed with a conventional polyester (self-made in the laboratory) at a mass ratio of 1:1, and melt spinning was carried out using a screw extrusion melt spinning machine. Among them, the diameter of the screw was 22 mm, the temperatures of the first, second, third, and fourth zones of the screw were set at 275 °C, 292 °C, 288 °C, and 292 °C respectively, the rotation speed of the pump was 40 r / min, the pump supply was adjusted to about 11 mL / r according to the actual fluidity during the spinning process, the aspect ratio of the spinneret was 1:4, the specification of the spinneret was 28 f / 0.5 mm, and the spinning speed was 1000 m / min.

[0088] The conventional polyester prepared in Comparative Example 1 was directly melt spun using a screw extrusion melt spinning machine, and the spinning parameters were the same as above, which will not be elaborated here.

[0089] The polyester fabrics were prepared from the yarns obtained by melt spinning, and the friction coefficients of the polyester fabrics were measured according to the standard ASTM D1894, that is, the static friction coefficient (COFs) and dynamic friction coefficient (COFk) when the slider slides on the fabric surface were measured. Specifically, the polyester fabric with no wrinkles and no pollution on the surface was cut into a size of 20 cm × 20 cm, and the static / dynamic friction coefficient was measured using a friction coefficient tester Labthink MXD-02 in an environment with a temperature of 25 ± 1 °C and a humidity of 65 ± 2% RH. Before measurement, the fabric needed to be equilibrated in an environment with the same temperature and humidity for 24 h. The test results are shown in the following table. By comparison, the friction coefficients of the polyester fabrics in Examples 1-3 were significantly smaller than those in Comparative Example 1, and the surface roughness was lower, indicating that the polyester fabrics in Examples 1-3 had a smoother handfeel.

[0090]

[0091] In summary, the present application provides a toughened polyester and its preparation method. By appropriately introducing bis-hydroxy / amino-terminated silicone oil and pentaerythritol monomers, and synergistically using the moderate cross-linking effect of pentaerythritol and the flexible toughening effect of silicone oil, the toughness of the polyester material is improved while having spinnability, and the fabric spun from the toughened polyester has a smooth handfeel. Among them, the dosage of silicone oil is preferably 15-30% of the mass of terephthalic acid, and more preferably 30%. The silicone oil is preferably hydroxy silicone oil or amino propyl terminated silicone oil. When pentaerythritol accounts for 0.05-0.25% of the mass of terephthalic acid and silicone oil accounts for 15-30% of the mass of terephthalic acid, the elongation at break of the toughened polyester prepared in the present application is 30-70%, and the yield strength is 50-70 MPa.

[0092] It should be noted that this application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments with the same composition and the same effects as the technical idea within the scope of the technical solution of this application are included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A toughened polyester, characterized in that, The toughened polyester is obtained by polymerizing terephthalic acid, ethylene glycol, pentaerythritol, and a hydroxyl-terminated / amino-terminated silicone oil. The toughened polyester has spinnability. Among them, the pentaerythritol accounts for 0.05-1% of the mass of the terephthalic acid, and the hydroxyl-terminated / amino-terminated silicone oil accounts for 1-40% of the mass of the terephthalic acid. The hydroxyl-terminated / amino-terminated silicone oil is hydroxyl silicone oil, aminopropyl-terminated silicone oil, or hydroxypropyl-terminated silicone oil. The corresponding structural general formulas of the toughened polyester are A, B, or C. Among them, A is B is C is and 1≤m≤2, 100≤n≤200, 1≤o≤40, 1≤p≤2, 10≤q≤100.

2. The toughened polyester according to claim 1, characterized in that, The number-average molecular weight of the hydroxyl silicone oil is between 1000 and 8000; the number-average molecular weight of the aminopropyl-terminated silicone oil is between 1000 and 8000; the number-average molecular weight of the hydroxypropyl-terminated silicone oil is between 1000 and 8000.

3. The toughened polyester according to claim 1, characterized in that, The molar ratio of the terephthalic acid to the ethylene glycol is 1:(1.2-1.6); the pentaerythritol accounts for 0.05-0.25% of the mass of the terephthalic acid, and the hydroxyl-terminated / amino-terminated silicone oil accounts for 15-30% of the mass of the terephthalic acid. At this time, the elongation at break of the toughened polyester is 30-70%, and the yield strength is 50-70 MPa.

4. A method for preparing the toughened polyester according to any one of claims 1-3, characterized in that, It includes the following steps: S1. Open the valve between the first condenser and the reaction kettle, put terephthalic acid and ethylene glycol into the reaction kettle, then add the catalyst Sb2O3, and raise the temperature of the reaction kettle to 250-260 °C under a nitrogen atmosphere and a pressure of 100-105 kPa. Carry out the esterification reaction at a stirring frequency of 30 Hz. The by-product water generated during the reaction flows out from the rear end of the first condenser. When the water output reaches the theoretically calculated value, the esterification reaction ends. S2. After the esterification reaction ends, put pentaerythritol and the hydroxyl-terminated / amino-terminated silicone oil into the reaction kettle and react at normal pressure for 0.5-1 h. S3. Close the valve between the first condenser and the reaction kettle, raise the temperature of the reaction kettle to 260-280 °C, and open the valve between the second condenser and the reaction kettle to carry out the polycondensation reaction. During the reaction, first control the vacuum degree in the reaction kettle to drop to the vacuum state through the vacuum fine-tuning valve, and then continue the polycondensation for 1-2 h at a stirring frequency of 25-50 Hz. After the reaction ends, discharge the material from the bottom of the reaction kettle and pelletize to obtain the toughened polyester.

5. The preparation method of the toughened polyester according to claim 4, characterized in that, In step S2, the hydroxyl-terminated / amino-terminated silicone oil is hydroxyl silicone oil, aminopropyl-terminated silicone oil, or hydroxypropyl-terminated silicone oil; in step S2, the dosage of the hydroxyl-terminated / amino-terminated silicone oil is 1-40% of the mass of the terephthalic acid in step S1; in step S2, the dosage of the pentaerythritol is 0.05-1% of the mass of the terephthalic acid in step S1.

6. The preparation method of the toughened polyester according to claim 4, characterized in that, In step S1, the molar ratio of the terephthalic acid to the ethylene glycol is 1:(1.2-1.6), and the dosage of the catalyst Sb2O3 based on the terephthalic acid is 400-600 ppm.

7. The preparation method of the toughened polyester according to claim 4, wherein, In step S3, continue polycondensation for 1 - 2 h at a stirring frequency of 25 - 50 Hz, which means reacting at a stirring frequency of 50 Hz for 0.5 - 1 h first, and then reacting at a stirring frequency of 25 Hz for 0.5 - 1 h.

8. The preparation method of the toughened polyester according to claim 5, wherein In step S2, the pentaerythritol accounts for 0.05 - 0.25% of the mass of the terephthalic acid, and the dihydroxy / diamino silicone oil accounts for 15 - 30% of the mass of the terephthalic acid.

9. The preparation method of the toughened polyester according to claim 4, wherein In steps S1 and S2, the temperature of the first condenser is set to 145 - 150 °C; in step S1, the pressure of the esterification reaction is controlled within 360 kPa.

10. The preparation method of the toughened polyester according to claim 4, characterized in that, In step S3, the temperature of the second condenser is set to 20 - 30 °C; in step S3, the reduction rate of the vacuum degree in the reaction kettle is 20 kPa / 10 min.

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