TW202446819A - Polyester polyol and method for producing the same - Google Patents

Abstract

A polyester polyol and method for producing the same are provided. The method for producing the polyester polyol includes a depolymerization step, an esterification step, and a pressure-reducing polycondensation step. The depolymerization step is implemented by using a depolymerizing liquid to depolymerize recycled PET chips to obtain a degradant. A usage content of the recycled PET chips is 20 parts by weight to 30 parts by weight, and a usage content of the depolymerizing liquid is 28 parts by weight to 35 parts by weight. The esterification step is implemented by reacting the degradant with a polyether diol and a monobasic acid to form a prepolymer. A usage content of the polyether diol is 5 parts by weight to 10 parts by weight, and a usage content of the monobasic acid is 34 parts by weight to 40 parts by weight. the pressure-reducing polycondensation step is implemented by continuously reducing an emvironment pressure of the prepolymer until a hydroxyl value of the prepolymer is less than 50 mmKOH/g to obtain the polyester polyol.

Description

Polyester polyol and its production method

The present invention relates to a polyester polyol and a method for producing the same, and in particular to a polyester polyol containing recycled PET bottle flakes and a method for producing the same.

In the prior art, polyester polyols made from recycled PET bottle flakes have poor low-temperature bending resistance and abrasion resistance.

The technical problem to be solved by the present invention is to provide a polyester polyol and a manufacturing method thereof in view of the shortcomings of the prior art, so as to improve the problem that the polyester polyol made from recycled PET bottle flakes in the prior art has poor low-temperature bending resistance and abrasion resistance.

In order to solve the above technical problems, one of the technical solutions adopted by the present invention is to provide a method for producing polyester polyols, which includes: a depolymerization step, depolymerizing a plurality of recycled PET bottle flakes with a depolymerization liquid to obtain a degradation product; wherein the amount of the recycled PET bottle flakes is between 20 parts by weight and 30 parts by weight, and the amount of the depolymerization liquid is between 28 parts by weight and 35 parts by weight; an esterification step, reacting the degradation product with a polyether diol and a dibasic acid to obtain a prepolymer; wherein the amount of the polyether diol is between 5 parts by weight and 10 parts by weight, and the amount of the dibasic acid is between 34 parts by weight and 40 parts by weight; and a decompression polymerization step, continuously reducing the environmental pressure of the prepolymer until the hydroxyl value of the prepolymer is less than 50. mmKOH/g to obtain a polyester polyol.

Preferably, the number average molecular weight of the polyester polyol is between 4,000 and 5,000.

Preferably, the depolymerization liquid is at least one selected from the group consisting of ethylene glycol, 1,4-butanediol and 1,6-hexanediol.

Preferably, the polyether diol is polytetrahydrofuran ether, and the dibasic acid is at least one selected from the group consisting of adipic acid (AA), sebacic acid (SA), terephthalic acid (PTA) and isophthalic acid (IPA).

Preferably, the polyester polyol has an acid value of 0.5 mgKOH/g or less, a glass transition temperature of -53°C to -50°C, and a hydroxyl value of 40 mmKOH/g to 50 mmKOH/g.

In order to solve the above technical problems, another technical solution adopted by the present invention is to provide a polyester polyol, which is formed by reacting a plurality of recycled PET bottle flakes, a depolymerization liquid, a polyether diol and a dibasic acid; wherein the amount of the recycled PET bottle flakes is between 20 parts by weight and 30 parts by weight, the amount of the depolymerization liquid is between 28 parts by weight and 35 parts by weight, the amount of the polyether diol is between 5 parts by weight and 10 parts by weight, and the amount of the dibasic acid is between 34 parts by weight and 40 parts by weight; wherein the hydroxyl value of the polyester polyol is less than 50 mmKOH/g.

Preferably, the number average molecular weight of the polyester polyol is between 4,000 and 5,000.

Preferably, the depolymerization liquid is at least one selected from the group consisting of ethylene glycol, 1,4-butanediol and 1,6-hexanediol.

Preferably, the polyether diol is polytetrahydrofuran ether, and the dibasic acid is at least one selected from the group consisting of adipic acid (AA), sebacic acid (SA), terephthalic acid (PTA) and isophthalic acid (IPA).

Preferably, the polyester polyol has an acid value of 0.5 mgKOH/g or less, a glass transition temperature of -53°C to -50°C, and a hydroxyl value of 40 mmKOH/g to 50 mmKOH/g.

One of the beneficial effects of the present invention is that the polyester polyol and the production method thereof provided by the present invention can improve the problem of poor low-temperature flexural resistance and wear resistance of the polyester polyol made from recycled PET bottle flakes in the prior art through the technical scheme of "the polyester polyol is formed by the reaction of the recycled PET bottle flakes, the depolymerization liquid, the polyether diol and the dibasic acid" and "the amount of the recycled PET bottle flakes is between 20 and 30 parts by weight, the amount of the depolymerization liquid is between 28 and 35 parts by weight, the amount of the polyether diol is between 5 and 10 parts by weight, and the amount of the dibasic acid is between 34 and 40 parts by weight".

To further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are only used for reference and description and are not used to limit the present invention.

The following is a specific embodiment to illustrate the implementation of the "polyester polyol and its production method" disclosed in the present invention. The technical personnel in this field can understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments. The details in this specification can also be modified and changed in various ways based on different viewpoints and applications without deviating from the concept of the present invention. In addition, the drawings of the present invention are only for simple schematic illustrations and are not depicted according to actual sizes. Please note in advance. The following implementation will further explain the relevant technical content of the present invention in detail, but the disclosed content is not intended to limit the scope of protection of the present invention.

It should be understood that, although the terms "first", "second", "third", etc. may be used herein to describe various components or signals, these components or signals should not be limited by these terms. These terms are mainly used to distinguish one component from another component, or one signal from another signal. In addition, the term "or" used herein may include any one or more combinations of the associated listed items depending on the actual situation.

[Production method of polyester polyol]

Refer to FIG. 1 , which is a schematic flow chart of a method for producing polyester polyols according to an embodiment of the present invention. The embodiment of the present invention provides a method for producing polyester polyols, in particular, a method for producing polyester polyols using recycled PET bottles. The method for producing polyester polyols comprises a depolymerization step S110, an esterification step S120, and a decompression polymerization step S130. Of course, the method for producing polyester polyols may include other steps according to actual application requirements, but the present invention is not limited thereto.

In the depolymerization step S110, a plurality of recycled PET bottle flakes are depolymerized with a depolymerization liquid to obtain a degradation product. Specifically, in the depolymerization step S110, the recycled PET bottle flakes are mixed with the depolymerization liquid and a small amount of catalyst (such as zinc acetate), and nitrogen is introduced, and the mixture is continuously stirred and gradually heated to between 200° C. and 230° C. (preferably about 215° C.) to obtain the transparent depolymerization product.

In the depolymerization step S110, the amount of the recycled PET bottle flakes is between 20 parts by weight and 30 parts by weight, and the amount of the depolymerization liquid is between 28 parts by weight and 35 parts by weight. It is worth mentioning that the depolymerization step S110 in the present invention is specifically for recycled PET bottle flakes, and the depolymerization step that mainly uses virgin polyester resin for depolymerization is not suitable for the depolymerization step S110 in the present invention.

In the depolymerization step S110 of this embodiment, the depolymerization liquid is at least one selected from the group consisting of ethylene glycol, 1,4-butanediol and 1,6-hexanediol. It is worth mentioning that, since the chain length of ethylene glycol is shorter, when ethylene glycol is selected as the depolymerization liquid, the flexibility of the polyester polyol is less than ideal. Accordingly, the depolymerization liquid can exclude ethylene glycol and be limited to 1,4-butanediol or 1,6-hexanediol. Preferably, the depolymerization liquid is 1,4-butanediol.

In the esterification step S120, the degradation product is reacted with a polyether diol and a dibasic acid to obtain a prepolymer. Specifically, in the esterification step S120, the degradation product is cooled to between 130°C and 160°C (preferably about 145°C), the polyether diol and the dibasic acid are added, and the temperature is raised to between 175°C and 205°C (preferably about 190°C) to react for 1 hour, and then the temperature is further raised to between 200°C and 230°C (preferably about 215°C) to react for 2 hours to remove the water generated by the reaction to form the prepolymer.

The amount of the polyether diol used is between 5 parts by weight and 10 parts by weight, and the amount of the dibasic acid used is between 34 parts by weight and 40 parts by weight. In the esterification step S120 of this embodiment, the polyether diol is polytetrahydrofuran ether (PTMG), and the dibasic acid is at least one selected from the group consisting of adipic acid (AA), sebacic acid (SA), terephthalic acid (PTA) and isophthalic acid (IPA). Preferably, the number average molecular weight of the polyether diol is between 1,000 and 2,000, and the dibasic acid is adipic acid.

In the decompression polycondensation step S130, the environmental pressure of the prepolymer is continuously reduced until the hydroxyl value of the prepolymer is less than 50 mmKOH/g to obtain a polyester polyol. Preferably, the polyester polyol has an acid value of less than 0.5 mgKOH/g, a glass transition temperature (Tg) between -53°C and -50°C, and a hydroxyl value between 40 mmKOH/g and 50 mmKOH/g, and the number average molecular weight of the polyester polyol is between 4,000 and 5,000. It is worth mentioning that in the decompression polycondensation step S130, the hydroxyl value of the prepolymer is controlled so that the polyester polyol can have a specific number average molecular weight.

[Polyester polyol]

This embodiment also provides a polyester polyol, which can be prepared by the aforementioned polyester polyol preparation method, but the present invention is not limited thereto.

The polyester polyol is formed by reacting a plurality of recycled PET bottle flakes, a depolymerization liquid, a polyether diol and a dibasic acid. In terms of dosage, the dosage of the recycled PET bottle flakes is between 20 parts by weight and 30 parts by weight, the dosage of the depolymerization liquid is between 28 parts by weight and 35 parts by weight, the dosage of the polyether diol is between 5 parts by weight and 10 parts by weight, and the dosage of the dibasic acid is between 34 parts by weight and 40 parts by weight.

The depolymerization liquid is at least one selected from the group consisting of ethylene glycol, 1,4-butanediol and 1,6-hexanediol. Preferably, the depolymerization liquid is 1,4-butanediol or 1,6-hexanediol.

The polyether diol is polytetrahydrofuran ether, and the dibasic acid is at least one selected from the group consisting of adipic acid (AA), sebacic acid (SA), terephthalic acid (PTA) and isophthalic acid (IPA). Preferably, the dibasic acid is adipic acid.

The polyester polyol has a number average molecular weight of 4,000 to 5,000, an acid value of 0.5 mgKOH/g or less, a glass transition temperature of -53°C to -50°C, and a hydroxyl value of 40 mmKOH/g to 50 mmKOH/g.

[Experimental data test]

Hereinafter, the contents of the present invention will be described in detail with reference to Examples 1 to 4 and Comparative Examples 1 to 3. However, the following examples are only used to help understand the present invention, and the scope of the present invention is not limited to these examples.

In Example 1, the polyester polyol is formed by reacting recycled PET bottle flakes, 1,4-butanediol (1,4-BG), polytetrahydrofuran ether (PTMG) and adipic acid (AA), the amount of recycled PET bottle flakes is 20.4 parts by weight, the amount of 1,4-butanediol is 34.8 parts by weight, the amount of polytetrahydrofuran ether is 5.3 parts by weight, and the amount of adipic acid is 49.5 parts by weight. The polytetrahydrofuran ether has a number average molecular weight of 1,000, and the polyester polyol has a number average molecular weight of 4,652, qualified low temperature bending resistance, 0.15% weight loss in abrasion resistance test, an acid value of 0.45 mgKOH/g, a glass transition temperature of -50.5°C, and a hydroxyl value of 42.3 mgKOH/g.

In Example 2, the polyester polyol is formed by reacting recycled PET bottle flakes, 1,4-butanediol (1,4-BG), polytetrahydrofuran ether (PTMG) and adipic acid (AA), the amount of recycled PET bottle flakes is 24.3 parts by weight, the amount of 1,4-butanediol is 32.1 parts by weight, the amount of polytetrahydrofuran ether is 6.2 parts by weight, and the amount of adipic acid is 37.4 parts by weight. The polytetrahydrofuran ether has a number average molecular weight of 1,000, and the polyester polyol has a number average molecular weight of 4,396, qualified low temperature bending resistance, 0.14% weight loss in abrasion resistance test, an acid value of 0.43 mgKOH/g, a glass transition temperature of -51.6°C, and a hydroxyl value of 46.1 mgKOH/g.

In Example 3, the polyester polyol is formed by reacting recycled PET bottle flakes, 1,4-butanediol (1,4-BG), polytetrahydrofuran ether (PTMG) and adipic acid (AA), the amount of recycled PET bottle flakes is 26.3 parts by weight, the amount of 1,4-butanediol is 30 parts by weight, the amount of polytetrahydrofuran ether is 8.5 parts by weight, and the amount of adipic acid is 35.2 parts by weight. The polytetrahydrofuran ether has a number average molecular weight of 1,000, and the polyester polyol has a number average molecular weight of 4,299, qualified low temperature bending resistance, 0.15% weight loss in abrasion resistance test, an acid value of 0.42 mgKOH/g, a glass transition temperature of -52.3°C, and a hydroxyl value of 45.6 mgKOH/g.

In Example 4, the polyester polyol is formed by reacting recycled PET bottle flakes, 1,4-butanediol (1,4-BG), polytetrahydrofuran ether (PTMG) and adipic acid (AA), the amount of recycled PET bottle flakes is 30 parts by weight, the amount of 1,4-butanediol is 28.2 parts by weight, the amount of polytetrahydrofuran ether is 9.8 parts by weight, and the amount of adipic acid is 32 parts by weight. The polytetrahydrofuran ether has a number average molecular weight of 1,000, and the polyester polyol has a number average molecular weight of 4,183, qualified low temperature bending resistance, 0.15% weight loss in abrasion resistance test, an acid value of 0.44 mgKOH/g, a glass transition temperature of -52.8°C, and a hydroxyl value of 48.3 mgKOH/g.

In Comparative Example 1, polyester polyol is formed by reacting recycled PET bottle flakes, ethylene glycol (EG) and adipic acid (AA), the amount of recycled PET bottle flakes is 20.4 parts by weight, the amount of ethylene glycol is 30.3 parts by weight, and the amount of adipic acid is 59.7 parts by weight. The polyester polyol has a number average molecular weight of 4,112, unqualified low temperature flex resistance, a weight loss of 0.12% in abrasion resistance test, an acid value of 0.53 mgKOH/g, a glass transition temperature of -47.8°C, and a hydroxyl value of 48.8 mgKOH/g.

In Comparative Example 2, the polyester polyol is formed by reacting recycled PET bottle flakes, 1,4-butanediol (1,4-BG) and adipic acid (AA), the amount of recycled PET bottle flakes is 20.4 parts by weight, the amount of 1,4-butanediol is 37.2 parts by weight, and the amount of adipic acid is 42.2 parts by weight. The polyester polyol has a number average molecular weight of 4,200, unqualified low temperature flex resistance, a weight loss of 0.14% in abrasion resistance test, an acid value of 0.51 mgKOH/g, a glass transition temperature of -48.3°C, and a hydroxyl value of 45.8 mgKOH/g.

In Comparative Example 3, polyester polyol is formed by reacting recycled PET bottle flakes, 1,4-butanediol (1,4-BG), polytetrahydrofuran ether (PTMG) and adipic acid (AA), the amount of recycled PET bottle flakes is 30 parts by weight, the amount of 1,4-butanediol is 27.5 parts by weight, the amount of polytetrahydrofuran ether is 10.5 parts by weight, and the amount of adipic acid is 34 parts by weight. The polytetrahydrofuran ether has a number average molecular weight of 1,000, and the polyester polyol has a number average molecular weight of 4,140, qualified low temperature bending resistance, 0.32% weight loss in abrasion resistance test, an acid value of 0.48 mgKOH/g, a glass transition temperature of -55.2°C, and a hydroxyl value of 48.1 mgKOH/g.

The proportions of the components, low-temperature flexural resistance, abrasion resistance, acid value, glass transition temperature, and hydroxyl value of the polyester polyols of Examples 1 to 4 and Comparative Examples 1 to 3 are summarized in Table 1 below, and the relevant test methods are described below.

Low-temperature bending resistance: The test sample (4.5cm*7cm) is mounted on a bending resistance tester (model GT-7006-V50) and subjected to 100,000 bending tests at an angle of 22.5°, a frequency of 100 times/minute and a temperature of -20°C. The surface of the test specimen is then observed for damage (wrinkles and cracks).

Wear resistance: The test sample (outer diameter 10cm, inner diameter 8mm) was placed in an abrasion tester (model ABRASER-5130) with a grinding wheel model H-22, a weight of 1Kg, and rotated 1000 times. After the test, the weight loss percentage was calculated.

Acid value: Take 10g of sample (weigh to four decimal places) in a conical flask, add 40ml of ethanol and toluene (1:1) solution to dissolve, then add 3 drops of 0.1% phenolphthalein indicator, stir evenly, and titrate with 0.1N potassium hydroxide (KOH) aqueous solution until it turns slightly red (lasting for ten seconds), and calculate the acid value according to the acid value formula. Acid value (mgKOH/g) A is the titration amount of 0.1N KOH aqueous solution (ml). N is the concentration of 0.1N KOH aqueous solution. S is the weight of the sample in g.

Glass transition temperature: Take 5 mg of the sample and place it on a differential scanning thermometer (model: TA DSC25) and analyze it at a temperature of -90°C to 150°C at a rate of 20°C/min.

Hydroxyl value: Take 3g of sample in a round-bottom flask (weigh to four decimal places), add 5ml of acetylation reagent (add 25ml of anhydrous acetic anhydride to 75ml of pyridine and mix well, set aside), heat to 95~100℃ for 1 hour, stop the reaction, add 1ml of distilled water, continue to heat to 95~100℃ for 1 hour, cool to room temperature, add 3 drops of 0.1% phenolphthalein indicator, and titrate with 0.5N potassium hydroxide (KOH) aqueous solution until it turns slightly red (last for ten seconds), and calculate the hydroxyl value according to the hydroxyl value formula. Hydroxyl value (mgKOH/g) A is the weight of the acetylation reagent in the blank test (g). B is the weight of the acetylation reagent in the sample test (g). C is the titration amount of the 0.5N KOH aqueous solution in the blank test (ml). D is the titration amount of the 0.5N KOH aqueous solution in the sample test (ml). N is the concentration of the 0.5N KOH aqueous solution. S is the weight of the sample in g.

[Table 1 Component ratios and physicochemical properties test results of the examples and comparative examples] Project Example 1 Example 2 Example 3 Example 4 Comparison Example 1 Comparison Example 2 Comparison Example 3 Parameter conditions of each component Amount of recycled PET bottle flakes (parts by weight) 20.4 24.3 26.3 30 20.4 20.4 30 Amount of depolymerization liquid (parts by weight) 34.8 32.1 30 28.2 30.3 37.2 27.5 Composition of depolymerization solution 1,4-BG 1,4-BG 1,4-BG 1,4-BG EG 1,4-BG 1,4-BG Amount of polyether diol used (parts by weight) 5.3 6.2 8.5 9.8 without without 10.5 Number average molecular weight of polyether diol 1000 1000 1000 1000 without without 1000 Composition of polyether diols PTMG PTMG PTMG PTMG without without PTMG Amount of dibasic acid (parts by weight) 49.5 37.4 35.2 32 59.7 42.2 34 Composition of dibasic acids AA AA AA AA AA AA AA Physical and chemical properties Number average molecular weight of polyester polyol 4,652 4,396 4,299 4,183 4,112 4,200 4,140 Low temperature bending resistance (-20℃*100,000 times) OK OK OK OK NG NG OK Abrasion resistance (weight loss%) 0.15 0.14 0.15 0.15 0.12 0.14 0.32 Acid value (mgKOH/g) 0.45 0.43 0.42 0.44 0.53 0.51 0.48 Glass transition temperature (℃) -50.5 -51.6 -52.3 -52.8 -47.8 -48.3 -55.2 Hydroxyl value (mgKOH/g) 42.3 46.1 45.6 48.3 48.8 45.8 48.1

[Test Results Discussion]

As can be seen from Examples 1 to 4, the polyester polyol is formed by reacting 20.4 to 30 parts by weight of recycled PET bottle flakes, 28.2 to 34.8 parts by weight of depolymerization liquid, 5.3 to 9.8 parts by weight of polyether diol, and 32 to 49.5 parts by weight of dibasic acid, and the polyester polyol has a number average molecular weight between 4183 and 4652, qualified low-temperature flexural resistance, a weight loss between 0.14% and 0.15%, an acid value between 0.42 mmKOH/g and 0.45 mmKOH/g, a glass transition temperature between -52.8°C and -50.5°C, and a hydroxyl value between 42.3 mmKOH/g and 48.3 mmKOH/g.

It can be seen from Comparative Examples 1 and 2 that the polyester polyol does not contain polyether diol, resulting in the polyester polyol's low-temperature flexural resistance being unqualified, the acid value being too high, and the glass transition temperature being too high.

From Comparative Example 3, it can be seen that using an excessive amount of polyether diol will result in a higher weight loss in the abrasion resistance test.

One of the beneficial effects of the present invention is that the polyester polyol and the production method thereof provided by the present invention can improve the problem of poor low-temperature flexural resistance and wear resistance of the polyester polyol made from recycled PET bottle flakes in the prior art through the technical scheme of "the polyester polyol is formed by the reaction of the recycled PET bottle flakes, the depolymerization liquid, the polyether diol and the dibasic acid" and "the amount of the recycled PET bottle flakes is between 20 and 30 parts by weight, the amount of the depolymerization liquid is between 28 and 35 parts by weight, the amount of the polyether diol is between 5 and 10 parts by weight, and the amount of the dibasic acid is between 34 and 40 parts by weight".

The contents disclosed above are only preferred feasible embodiments of the present invention and are not intended to limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made using the contents of the specification and drawings of the present invention are included in the scope of the patent application of the present invention.

S110: Depolymerization step S120: Esterification step S130: Compression polymerization step

FIG1 is a schematic diagram of a process for producing polyester polyol according to an embodiment of the present invention.

S110: Depolymerization step

S120: Esterification step

S130: Decompression and polymerization step

Claims (10)

A method for producing polyester polyols, comprising: a depolymerization step, depolymerizing a plurality of recycled PET bottle flakes with a depolymerization liquid to obtain a degradation product; wherein the amount of the recycled PET bottle flakes is between 20 parts by weight and 30 parts by weight, and the amount of the depolymerization liquid is between 28 parts by weight and 35 parts by weight; an esterification step, reacting the degradation product with a polyether diol and a dibasic acid to obtain a prepolymer; wherein the amount of the polyether diol is between 5 parts by weight and 10 parts by weight, and the amount of the dibasic acid is between 34 parts by weight and 40 parts by weight; and a decompression polymerization step, continuously reducing the environmental pressure of the prepolymer until the hydroxyl value of the prepolymer is less than 50 mmKOH/g, to obtain a polyester polyol. The method for producing a polyester polyol as described in claim 1, wherein the number average molecular weight of the polyester polyol is between 4,000 and 5,000. The method for producing a polyester polyol according to claim 1, wherein the depolymerization liquid is at least one selected from the group consisting of ethylene glycol, 1,4-butanediol, and 1,6-hexanediol. The method for producing polyester polyol as described in claim 1, wherein the polyether diol is polytetrahydrofuran ether, and the dibasic acid is at least one selected from the group consisting of adipic acid (AA), sebacic acid (SA), terephthalic acid (PTA) and isophthalic acid (IPA). A method for producing a polyester polyol as described in claim 1, wherein the polyester polyol has an acid value of less than 0.5 mgKOH/g, a glass transition temperature between -53°C and -50°C, and a hydroxyl value between 40 mmKOH/g and 50 mmKOH/g. A polyester polyol is formed by reacting a plurality of recycled PET bottle flakes, a depolymerization liquid, a polyether diol and a dibasic acid; wherein the amount of the recycled PET bottle flakes is between 20 parts by weight and 30 parts by weight, the amount of the depolymerization liquid is between 28 parts by weight and 35 parts by weight, the amount of the polyether diol is between 5 parts by weight and 10 parts by weight, and the amount of the dibasic acid is between 34 parts by weight and 40 parts by weight; wherein the hydroxyl value of the polyester polyol is less than 50 mmKOH/g. The polyester polyol as described in claim 6, wherein the number average molecular weight of the polyester polyol is between 4,000 and 5,000. The polyester polyol according to claim 6, wherein the depolymerization liquid is at least one selected from the group consisting of ethylene glycol, 1,4-butanediol and 1,6-hexanediol. The polyester polyol as described in claim 6, wherein the polyether diol is polytetrahydrofuran ether, and the dibasic acid is at least one selected from the group consisting of adipic acid (AA), sebacic acid (SA), terephthalic acid (PTA) and isophthalic acid (IPA). The polyester polyol as described in claim 6, wherein the polyester polyol has an acid value of less than 0.5 mgKOH/g, a glass transition temperature between -53°C and -50°C, and the hydroxyl value between 40 mmKOH/g and 50 mmKOH/g.