A copolymer modified polyester and a method for preparing the same

Abstract

The application discloses a kind of copolymer modified polyester and its preparation method, belong to polyester field.The method uses glycerol or dimer glycerol as copolymer tri-monomer, synthesizes glycerol modified polyethylene isophthalate, and the melting point of the modified polyester can reach about 110 DEG C.This kind of low melting point copolymer with certain crosslinking molecular chain can be co-extruded with toughening modifier polybutylene adipate in screw extruder, and the plate material with thickness of more than 1cm is extruded by mixing, has excellent toughness and impact resistance, and is used for producing shoe front and rear cover material.

Description

Technical Field

[0001] This invention relates to the field of polyesters, and more specifically to a copolymer-modified polyester and its preparation method. Background Technology

[0002] Currently, the base materials for shoe toe puffs and hell counters are mainly polyvinyl chloride (PVC), high-density polyethylene, polyethylene copolymers, polycaprolactone, or 1,4-cyclohexanediethanol (CHDM) modified polyester PETG. These materials are mixed with impact performance modifiers and processed into thick plates for shoes. Impact performance modifiers mainly include epoxy-containing ethylene copolymers, anhydride-grafted ethylene copolymers such as maleic anhydride copolymers, and more commonly polybutylene adipate.

[0003] Among these substrates, polyvinyl chloride (PVC) is gradually being restricted due to environmental factors; polyethylene and polyethylene copolymers generally perform poorly; and polycaprolactone (PVC) and PETG are expensive. Saturated polyesters, such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), have excellent mechanical and heat resistance properties, but poor impact resistance, especially at temperatures below 0°C. Blending saturated polyesters with impact modifiers can significantly improve the poor impact resistance, meeting the requirements for footwear materials. However, because saturated polyesters have a high melting point, blending with impact modifiers requires a relatively high temperature (>250°C). At this temperature, the impact modifiers degrade severely due to their poor temperature resistance. Therefore, a modified polyester that can be blended with impact modifiers at low temperatures is needed. Summary of the Invention

[0004] This invention addresses the aforementioned technical problems by providing a copolymerized modified polyester and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A copolymer-modified polyester is prepared by using diacid and diol as raw materials and glycerol or diglycerol as copolymerizing monomers, and carrying out an esterification reaction under the action of a catalyst; after the esterification reaction is completed, a polycondensation reaction is carried out, and after the polycondensation reaction is completed, the target product can be obtained.

[0007] In the technical solution of this invention, the amount of the copolymer modified monomer in the polyester is 0.5wt% to 10wt%.

[0008] In the technical solution of this invention: the diacid is isophthalic acid, the diol is ethylene glycol; the polyol is ethylene glycol and a copolymerized modified monomer, and the molar ratio of the polyol to the diacid is not less than 1.60. More preferably: the molar ratio of the polyol to the diacid is 1.64 to 1.74.

[0009] In the technical solution of this invention: the polyol is ethylene glycol and glycerol; or the polyol is ethylene glycol and diglycerol; or the polyol is ethylene glycol, glycerol and diglycerol.

[0010] In the technical solution of this invention: the temperature of the esterification reaction is 200-260℃ and the esterification pressure is 2.3-2.8MPa.

[0011] In the technical solution of this invention, the catalyst used for the esterification reaction is any one of antimony glycolate, antimony acetate, or antimony trioxide.

[0012] In the technical solution of this invention: the amount of catalyst Sb in the polyester is 150-250 μg / g.

[0013] In the technical solution of this invention: the temperature of the polycondensation reaction is 270℃~290℃, and the vacuum degree is less than 100Pa.

[0014] A method for preparing the above-mentioned copolymer modified polyester, comprising: using isophthalic acid and ethylene glycol as raw materials, and glycerol or diglycerol as copolymer modifying monomers, carrying out an esterification reaction under the action of a catalyst; after the esterification reaction is completed, carrying out a polycondensation reaction; after the polycondensation reaction is completed, the target product can be obtained.

[0015] The present invention relates to the application of the copolymerized modified polyester as a base material for shoe front and back covers. Traditionally, low-melting-point polyesters are synthesized using copolymerizing monomers such as isophthalic acid and 1,4-cyclohexanediethanol. When the melting point is below 190°C, these are essentially non-crystalline copolyesters. This type of low-melting-point polyester is used in a screw extrusion compounding process with the toughening modifier polybutylene adipate to produce sheets with a thickness of 1 cm or more for the production of shoe front and back cover materials. However, due to its non-crystalline nature, this copolyester is difficult to dry and dehydrate, making it inconvenient to use.

[0016] This invention uses glycerol or diglycerol as a comonomer to synthesize glycerol-modified polyethylene isophthalate. This modified polyester is a low-melting-point polyester with a melting point of around 110°C and a certain degree of cross-linking in its polymer chains, and is capable of crystallization. Due to its certain crystallinity, it is easy to dry and remove water, and compared with non-crystallizable materials, the processed shoe materials have better strength and toughness.

[0017] This invention uses glycerol or diglycerol as a comonomer to synthesize glycerol-modified polyethylene isophthalate, which has a melting point of about 110°C.

[0018] The copolymerized modified monomers glycerol or diglycerol, isophthalic acid, ethylene glycol, and antimony catalyst are stirred and slurried together. After three nitrogen purgings, the mixture is heated to a temperature of 200℃~260℃ and an esterification pressure (gauge pressure) of about 2.5MPa. When the amount of water produced during esterification reaches the theoretical amount, the esterification is stopped, the pressure is released to atmospheric pressure, and the temperature is raised to above 270℃ for about 45 minutes under reduced pressure, entering the high-vacuum polycondensation stage. The vacuum is below 100Pa, and the polycondensation temperature is controlled at 270℃~290℃. When the stirring current reaches the rated value, the mixture is discharged, yielding the desired copolymerized modified polyester.

[0019] Similar to conventional polyester, the catalyst used is an antimony catalyst, which is any one of the antimony glycolate, antimony acetate, or antimony trioxide commonly used in the polyester industry, and the amount used is the same as that of conventional polyester.

[0020] The modified monomer glycerol or diglycerol is used in the polyester at a weight percentage of 0.5% to 10%, and the copolyester has a melting point of about 110°C to 125°C.

[0021] The prepared copolyester was mixed with a toughening modifier and added to a twin-screw extruder. After thorough melt mixing, the mixture was drawn into strands and pelletized. The pellets were then subjected to simple surface dehydration before being used for further processing. The pellets were fed into a single-layer extruder equipped with a T-die, and after melt plasticization, a flat material suitable for use as the forefoot and heel flaps of shoes was obtained. This flat material possesses excellent toughness, cold resistance, and stiffness, making it ideal as a shoe material, especially for the forefoot and heel flaps. Due to the poor temperature resistance and susceptibility to thermal degradation of the impact modifier, the mixing temperature of the copolyester and toughening modifier should not exceed 160℃.

[0022] The beneficial effects of this invention are:

[0023] The method of this invention produces a low-melting-point polyester. The prepared low-melting-point polyester has a melting point of approximately 110°C and can replace expensive PETG and polycaprolactone materials in the base material of shoe toe puffs and hell counters. This low-melting-point polyester can still crystallize, and when mixed with toughening modifiers, it can be used to produce flat sheet materials for shoe toe puffs and hell counters, exhibiting excellent toughness and impact resistance. Detailed Implementation

[0024] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto:

[0025] (1) Bending test---20 cm in size, folded in half horizontally and vertically once, and check for breakage. A batch of samples is tested 10 times. If one breaks, it is considered unqualified.

[0026] (2) Impact resistance test---ASTM-D3763 method, with 10 samples per batch, the average value is less than 250 kg / mm, which is considered unqualified.

[0027] (3) ROSS room temperature bending (23℃) and cold bending (-10℃) test---ASTM-D1052 method. The maximum number of room temperature bending tests is 75,000, and the maximum number of cold bending tests is 25,000. The sample is considered unqualified if there is cracking or breakage at the center cut of the sample.

[0028] Example 1

[0029] Add 41 g of glycerol, 200 g of ethylene glycol, 350 g of isophthalic acid, and 0.108 g of antimony glycol to a 2 L reactor. Esterification is carried out at a temperature of 200℃~260℃ and a pressure (gauge pressure) of 2.5 MPa. When the water output reaches the theoretical value, esterification is stopped, and the pressure is released to atmospheric pressure. The temperature is gradually increased to enter the low vacuum stage. After about 45 min of low vacuum, the high vacuum polycondensation stage (vacuum degree <100 Pa) is entered. The polycondensation temperature is 270℃~290℃. When the stirring power reaches the rated value, the material is discharged. The synthesized modified polyester has a DSC melting point of 111.6℃, a melting crystallization temperature of 89℃, an intrinsic viscosity of 0.662 dL / g, and a terminal carboxyl group of 28 mol / t.

[0030] Example 2

[0031] 21 g of glycerol, 213 g of ethylene glycol, 350 g of isophthalic acid, and 0.176 g of antimony glycol were added to a 2 L reactor. Esterification was carried out at a temperature of 200℃~260℃ and a pressure (gauge pressure) of 2.5 MPa. When the water output reached the theoretical value, esterification was stopped, and the pressure was released to atmospheric pressure. The temperature was gradually increased to enter the low vacuum stage. After about 45 min of low vacuum, the high vacuum polycondensation stage (vacuum degree <100 Pa) was entered. The polycondensation temperature was 270℃~290℃. The material was discharged when the stirring power reached the rated value. The synthesized modified polyester had a melting point of 116.5℃, a melting crystallization temperature of 90.3℃, an intrinsic viscosity of 0.651 dL / g, and a terminal carboxyl group of 29 mol / t, as determined by DSC testing.

[0032] Example 3

[0033] Add 2.0 g of glycerol, 220 g of ethylene glycol, 350 g of isophthalic acid, and 0.13 g of antimony glycol to a 2 L reactor. Esterification is carried out at a temperature of 200℃~260℃ and a pressure (gauge pressure) of 2.5 MPa. When the water output reaches the theoretical value, esterification is stopped, the pressure is released to atmospheric pressure, and stirring is continued for 10 minutes. The temperature is gradually increased to enter the low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage (vacuum degree <100 Pa) is entered. The polycondensation temperature is 270℃~290℃. When the stirring power reaches the rated value, the product is discharged. The synthesized modified polyester has a melting point of 122.7℃, a melting crystallization temperature of 92.1℃, an intrinsic viscosity of 0.645 dL / g, and a terminal carboxyl group of 23 mol / t, as determined by DSC testing.

[0034] Example 4

[0035] Add 21 g of diglycerol, 350 g of isophthalic acid, 0.13 g of antimony glycol, and 210 g of ethylene glycol to a 2 L reactor. Esterification temperature is 200℃~260℃, esterification pressure (gauge pressure) is 2.5 MPa. When the water output reaches the theoretical value, esterification is stopped, the pressure is released to atmospheric pressure, and stirring is continued for 10 minutes. The temperature is gradually increased to enter the low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage (vacuum degree <100 Pa) is entered. Polycondensation temperature is 270℃~290℃. When the stirring power reaches the rated value, the material is discharged. The synthesized modified polyester has a melting point of 115.5℃, a melting crystallization temperature of 90.5℃, an intrinsic viscosity of 0.653 dL / g, and a terminal carboxyl group of 26 mol / t, as determined by DSC testing.

[0036] Example 5

[0037] Add 40 g of diglycerol, 350 g of isophthalic acid, 0.13 g of antimony glycol, and 200 g of ethylene glycol to a 2 L reactor. Esterification temperature is 200℃~260℃, esterification pressure (gauge pressure) is 2.5 MPa. When the water output reaches the theoretical value, esterification is stopped, the pressure is released to normal, and stirring continues for 10 minutes. Gradually increase the temperature to enter the low vacuum stage. After about 45 minutes of low vacuum, enter the high vacuum polycondensation stage (vacuum degree <100 Pa). Polycondensation temperature is 270℃~290℃. When the stirring power reaches the rated value, discharge the material. The synthesized modified polyester has a melting point of 110.2℃, a melting crystallization temperature of 89.3℃, an intrinsic viscosity of 0.663 dL / g, and a terminal carboxyl group of 24.6 mol / t, as determined by DSC testing.

[0038] Example 6

[0039] Add 350 g of isophthalic acid, 0.13 g of antimony glycol, 210 g of ethylene glycol, 5 g of glycerol, and 15 g of diglycerol to a 2 L reactor. Esterification is carried out at a temperature of 200℃~260℃ and a pressure (gauge pressure) of 2.5 MPa. When the water output reaches the theoretical value, esterification is stopped, the pressure is released to atmospheric pressure, and stirring is continued for 10 minutes. The temperature is gradually increased to enter the low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage (vacuum degree <100 Pa) is entered. The polycondensation temperature is 270℃~290℃. When the stirring power reaches the rated value, the product is discharged. The synthesized modified polyester has a melting point of 115.8℃, a melting crystallization temperature of 90.7℃, an intrinsic viscosity of 0.663 dL / g, and a terminal carboxyl group of 25.6 mol / t, as determined by DSC testing.

[0040] Example 7

[0041] Add 350g isophthalic acid, 0.13g antimony glycol, 200g ethylene glycol, 15g glycerol, and 25g diglycerol to a 2L reactor. Esterification is carried out at a temperature of 200℃~260℃ and a pressure (gauge pressure) of 2.5MPa. When the water output reaches the theoretical value, esterification is stopped, the pressure is released to atmospheric pressure, and stirring is continued for 10 minutes. The temperature is gradually increased to enter the low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage (vacuum degree <100Pa) is entered. The polycondensation temperature is 270℃~290℃. When the stirring power reaches the rated value, the product is discharged. The synthesized modified polyester has a melting point of 110.6℃, a melting crystallization temperature of 89.5℃, an intrinsic viscosity of 0.655dL / g, and a terminal carboxyl group of 27.6mol / t, as determined by DSC testing.

[0042] Comparative Example 1:

[0043] 222 g of ethylene glycol, 350 g of isophthalic acid, and 0.13 g of antimony glycol were added to a 2 L reactor. Esterification was carried out at a temperature of 200℃~260℃ and a pressure (gauge pressure) of 2.5 MPa. When the water output reached the theoretical value, esterification was stopped, the pressure was released to atmospheric pressure, and stirring was continued for 10 minutes. The temperature was gradually increased to enter the low vacuum stage. After about 45 minutes of low vacuum, the high vacuum polycondensation stage (vacuum < 100 Pa) was entered. The polycondensation temperature was 270℃~290℃. The material was discharged when the stirring power reached the rated value. The synthesized modified polyester had a melting point of 148.7℃, a melting crystallization temperature of 105.1℃, an intrinsic viscosity of 0.655 dL / g, and a terminal carboxyl group of 26 mol / t, as determined by DSC testing.

[0044]

[0045] Table 1 Performance Test Results

[0046]

Claims

1. The application of a copolymer-modified polyester as a base material for the forefoot and heel counters of shoes, characterized in that: The polyester is prepared by using diacid and diol as raw materials, glycerol or diglycerol as comonomer, and carrying out esterification reaction under the action of catalyst; after the esterification reaction is completed, polycondensation reaction is carried out, and after the polycondensation reaction is completed, the target product can be obtained. The amount of copolymer-modifying monomer used in the polyester is 0.5 wt% to 10 wt%. The diacid is isophthalic acid, and the diol is ethylene glycol; the molar ratio of the total amount of diol and copolymer modified monomer to the diacid is 1.64~1.74; the melting point of the copolymer modified polyester is 110℃~125℃.

2. The application according to claim 1, characterized in that: The esterification reaction temperature is 200~260℃ and the esterification pressure is 2.3~2.8MPa.

3. The application according to claim 1, characterized in that: The catalyst used in the esterification reaction is any one of antimony glycolate, antimony acetate, or antimony trioxide.

4. The application according to claim 3, characterized in that: The amount of catalyst Sb used in polyester is 150–250 μg / g.

5. The application according to claim 1, characterized in that: The polycondensation reaction occurs at temperatures ranging from 270°C to 290°C, with a vacuum level below 100 Pa.

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