Polyester polyol prepared from PBAT waste and preparation method thereof

Abstract

The invention discloses polyester polyol prepared from PBAT waste and a preparation method of the polyester polyol, and relates to the technical field of high polymer material recycling, the polyester polyol is prepared from the following raw materials by weight: 25-35 parts of PBAT waste plastic; 15 to 20 parts of aromatic anhydride; 15 to 20 parts of unsaturated fatty acid; 30 to 45 parts of polyol; 0.1 part to 0.5 part of a catalyst; wherein the catalyst comprises zinc acetate and / or stannous chloride. According to the method, the PBAT waste is used as the raw material, the PBAT waste is recycled through a chemical method to synthesize the polyester polyol, the environmental pressure caused by the PBAT waste can be effectively relieved, the conversion rate of the PBAT waste reaches 95% or above by selecting the catalyst and controlling the adding amount of the catalyst, and the method is very suitable for large-scale popularization.

Description

Technical Field

[0001] The present application relates to the technical field of polymer material recycling, and in particular to a polyester polyol prepared from PBAT waste and a preparation method thereof. Background Art

[0002] As the environmental pollution caused by discarded plastics becomes more and more serious, biodegradable polyester has gradually become the focus of public attention. Polybutylene Adipate Terephthalate (PBAT) is an aliphatic aromatic copolyester, which is made by polycondensation of adipate-butylene glycol ester and terephthalate-butylene glycol ester. It not only maintains the good properties of aromatic polyester, but also has biodegradability due to its aliphatic components, and belongs to thermoplastic biodegradable plastics.

[0003] Compared with other biodegradable polyesters, PBAT has better ductility, thermal stability and plasticity, and is widely used in agriculture (agricultural mulch), textile industry, food packaging and other industries. According to the European Plastics Association, the global production of biodegradable plastics in 2021 was 1.556 million tons, of which PBAT plastics accounted for 29.9% (about 464,600 tons), the highest proportion among biodegradable plastics.

[0004] Although PBAT plastic is degradable, it has a regular crystalline molecular structure and the polymer fibers are arranged very closely, so it degrades slowly. Current studies have shown that the biodegradation of PBAT is usually achieved in composting at 70% humidity and 55°C. These conditions are not easy to exist in the natural environment and lack easy degradability under natural conditions. Therefore, only a few of the discarded PBAT plastics decompose in garbage dumps, soil, fresh water and sea water, and most of them are discarded and piled up in nature, posing a huge threat to the ecological environment.

[0005] Therefore, the art urgently needs to find a new way to recycle PBAT waste. Summary of the invention

[0006] At present, most rigid foam polyester polyols are synthesized using phthalic anhydride and polyols as raw materials. The technology is very mature, the homogeneous competition is serious, and the profit is getting lower and lower. The purpose of this application is to provide a new way to recycle PBAT waste, using PBAT waste as raw material, and using chemical method to recycle PBAT waste to synthesize polyester polyols, which can not only effectively alleviate the environmental pressure brought by PBAT waste, but also break the homogeneous competition of rigid foam polyester polyols.

[0007] To achieve the above objectives, this application provides the following technical solutions.

[0008] In the first aspect, the present application provides a polyester polyol prepared using PBAT waste, wherein the polyester polyol is prepared from the following raw materials in parts by weight: 25 to 35 parts of PBAT waste; 15 to 20 parts of aromatic anhydride; 15 to 20 parts of unsaturated fatty acid; 30 to 45 parts of polyol; and 0.1 to 0.5 parts of catalyst; wherein the catalyst includes zinc acetate and / or stannous chloride.

[0009] In some embodiments of the first aspect, in the catalyst, the weight ratio of the zinc acetate to the stannous chloride is (1-1.5):1.

[0010] In some embodiments of the first aspect, the raw materials satisfy any one or more of the following characteristics: (1) the aromatic anhydride includes phthalic anhydride; (2) the unsaturated fatty acid includes oleic acid; (3) the polyol includes 25 to 35 parts of diethylene glycol and 5 to 10 parts of glycerol.

[0011] In a second aspect, the present application provides a method for preparing polyester polyols using PBAT waste, wherein the method is prepared using the following raw materials in parts by weight: 25 to 35 parts of PBAT waste; 15 to 20 parts of aromatic anhydride; 15 to 20 parts of unsaturated fatty acid; 30 to 45 parts of polyol; and 0.1 to 0.5 parts of catalyst; wherein the catalyst includes zinc acetate and / or stannous chloride.

[0012] In some embodiments of the second aspect, the method includes the following steps: mixing and dissolving the PBAT waste, the aromatic anhydride, the unsaturated fatty acid and the polyol, and keeping them warm at a first temperature for a first predetermined time to obtain a reaction mixture; adding the catalyst to the reaction mixture, heating it to a second temperature and keeping it warm for a second predetermined time to react, so as to obtain the polyester polyol.

[0013] In some embodiments of the second aspect, the method satisfies any one or more of the following features: 1) in the catalyst, the weight ratio of the zinc acetate to the stannous chloride is (1 to 1.5):1; 2) the aromatic anhydride includes phthalic anhydride; 3) the unsaturated fatty acid includes oleic acid; 4) the polyol includes 25 to 35 parts of diethylene glycol and 5 to 10 parts of glycerol; 5) the first temperature is 170°C to 190°C, and the first predetermined time is 2 hours to 3 hours; 6) the second temperature is 210°C to 225°C, and the second predetermined time is 3 hours to 6 hours.

[0014] In some embodiments of the second aspect, the conversion rate of the PBAT waste is greater than 95%.

[0015] In some embodiments of the second aspect, the method further comprises: making the acid value of the polyester polyol reach a final target acid value.

[0016] In some embodiments of the second aspect, the method for making the acid value of the polyester polyol reach the target value includes: detecting the acid value of the polyester polyol, when the acid value reaches the initial target acid value, cooling to a third temperature, gradually increasing the vacuum degree and maintaining the vacuum degree within a preset range, sampling and detecting the acid value after vacuum dehydration for a third predetermined time, and stopping the vacuum when the acid value reaches the final target acid value.

[0017] In some embodiments of the second aspect, the initial target acid value is less than 10 mgKOH / g, the final target acid value is less than 2 mgKOH / g; the third temperature is 210°C to 220°C, the preset range is -0.02MPa to -0.09MPa, and the third predetermined time is 1 hour to 3 hours.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This application uses PBAT waste as raw material to synthesize polyester polyols, providing a new way to recycle PBAT waste, which can not only solve the environmental pollution problem of PBAT waste plastics, but also provide a new idea for the synthesis of polyester polyols, with high environmental value and commercial value. Furthermore, this application can achieve a conversion rate of more than 95% of PBAT waste through the selection of catalysts and the control of the amount of catalyst added, which is very suitable for large-scale promotion. DETAILED DESCRIPTION

[0020] The following description provides specific application scenarios and requirements of the present application, with the purpose of enabling those skilled in the art to make and use the content in the present application. It will be apparent to those skilled in the art that various local modifications to the disclosed embodiments are apparent, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present application. Therefore, the present application is not limited to the embodiments shown, but to the widest scope consistent with the claims.

[0021] The first aspect of the present application provides a polyester polyol prepared from PBAT waste, wherein the polyester polyol is prepared from the following raw materials in parts by weight: 25 to 35 parts of PBAT waste, 15 to 20 parts of aromatic anhydride, 15 to 20 parts of unsaturated fatty acid, 30 to 45 parts of polyol, and 0.1 to 0.5 parts of catalyst. The present application innovatively uses PBAT waste as raw material to prepare polyester polyol, which not only opens up a new way to recycle PBAT waste plastics, but also provides a new method for synthesizing polyester polyol.

[0022] As an example, the weight of the PBAT waste plastic can be 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, etc., or any point value in all sub-ranges that the listed values ​​can consist of. The weight of the aromatic anhydride can be 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, etc., or any point value in all sub-ranges that the listed values ​​can consist of. The weight of the unsaturated fatty acid can be 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, etc., or any point value in all sub-ranges that the listed values ​​can consist of. The weight of the polyol can be 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, 45 parts, etc., or any point value in all sub-ranges that can be formed by the listed values. The weight of the catalyst can be 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, etc., or any point value in all sub-ranges that can be formed by the listed values.

[0023] In particular, the application uses zinc acetate and / or stannous chloride as the catalyst of reaction, and the electronegativity of zinc metal ions in zinc acetate promotes metal acetate and alcohol reaction to generate metal alcoholate, and acetic acid is generated simultaneously, and then the metal on the metal alcoholate provides empty orbit, and the lone pair of electrons of carboxyl oxygen in PBAT is coordinated and combined (complexed) to complete transesterification reaction. The reason why zinc acetate has high catalytic efficiency is that zinc ion electronegativity is larger. And the catalytic principle of stannous chloride is similar to Lewis acid, and stannous chloride as Lewis acid in the reaction system can directly act on power supply reagent without decomposition, and the electronegativity of divalent tin ions is relatively high, and carboxylic acid group electrons have a certain attraction, and the carboxyl group II in the coordination bond and carboxylic acid is built to form a phase complex, causing the carboxyl carbon atom of the carboxyl group to carry more positive electricity, due to the nucleophilic characteristics of esterification, it is more conducive to the occurrence of nucleophilic addition of alcohol, so that the reaction activity can be reduced, and the reaction activity increases. When zinc acetate and stannous chloride are mixed and used as a catalyst, the alkaline centers distributed on the solid surface of stannous chloride can receive protons, which play a synergistic role in the formation of complex intermediates between zinc ions and acyl oxygen in zinc acetate. The original acyl oxygen is broken, and the zinc ions are freed again, and continue to complex with other acyl oxygens to produce the next round of catalytic process, thereby accelerating the depolymerization process of PBAT and achieving a synergistic effect of 1+1>2. At the same time, by controlling the amount of catalyst added, the degradation conversion rate of PBAT waste can unexpectedly reach more than 95% at a higher addition amount, and even up to 100%. Therefore, the present application achieves an excellent level of recycling rate of PBAT waste through the selection of catalysts and the control of their addition amount, which is very suitable for large-scale promotion.

[0024] In some preferred embodiments, the catalyst includes the zinc acetate and the stannous chloride in a weight ratio of (1-1.5):1. Compared with a single catalyst, the mixed catalyst can achieve a PBAT conversion rate of 100% in a shorter time.

[0025] Except for the type of the catalyst, the present application does not specifically limit the types of the aromatic anhydride, the unsaturated fatty acid and the polyol.

[0026] In some preferred embodiments, the aromatic anhydride includes phthalic anhydride.

[0027] In some preferred embodiments, the unsaturated fatty acid comprises oleic acid.

[0028] In some preferred embodiments, the polyol includes 25 to 35 parts of diethylene glycol and 5 to 10 parts of glycerol.

[0029] In some preferred embodiments, the polyester polyol is prepared from the following raw materials in parts by weight: 25 to 35 parts of PBAT waste, 15 to 20 parts of phthalic anhydride, 15 to 20 parts of oleic acid, 25 to 35 parts of diethylene glycol, 5 to 10 parts of glycerol, and 0.1 to 0.5 parts of zinc acetate and / or stannous chloride.

[0030] The PBAT waste of the present application can be any discarded PBAT plastic in nature, such as the leftovers from the start-up and shutdown of PBAT factories, cutting waste, unqualified slices, domestic and medical waste packaging materials, agricultural mulch, etc.

[0031] The second aspect of the present application provides a method for preparing polyester polyols using PBAT waste. The method adopts the raw materials described in the first aspect, and by selecting zinc acetate and / or stannous chloride as catalysts and controlling their weight parts between 0.1 parts and 0.5 parts, when the weight parts of the PBAT waste are as high as 25 parts to 35 parts, the conversion rate of the PBAT waste can also reach more than 95%.

[0032] In some embodiments, the method comprises the following steps:

[0033] S1: mixing and dissolving the PBAT waste, the aromatic anhydride, the unsaturated fatty acid and the polyol, and keeping the mixture at a first temperature for a first predetermined time to obtain a reaction mixture;

[0034] S2: After adding the catalyst into the reaction mixture, the temperature is raised to a second temperature and kept at the second predetermined time to react to obtain the polyester polyol.

[0035] In some preferred embodiments, step S1 and step S2 are performed under the protection of an inert gas, for example, the inert gas is nitrogen.

[0036] In some preferred embodiments, in step S1, the first temperature is 170°C to 190°C, and the first predetermined time is 2 hours to 3 hours.

[0037] In some preferred embodiments, in step S2, the second temperature is 210°C to 225°C, and the second predetermined time is 3 hours to 6 hours.

[0038] In some preferred embodiments, the method further comprises: making the acid value of the polyester polyol reach the final target acid value. In some specific embodiments, the method for making the acid value of the polyester polyol reach the target value comprises: detecting the acid value of the polyester polyol, when the acid value reaches the initial target acid value, cooling to a third temperature, gradually increasing the vacuum degree and keeping the vacuum degree within a preset range, sampling and detecting the acid value after the third predetermined time of vacuum dehydration, and stopping the vacuum when the acid value reaches the final target acid value. The vacuum dehydration operation can not only adjust the acid value of the reaction product polyester polyol to the final target acid value, but also optimize the hydroxyl value and viscosity adjustment to the desired numerical range at the same time. As an example, the initial target acid value is below 10 mgKOH / g, and the final target acid value is below 2 mgKOH / g.

[0039] Since the depolymerization of PBAT waste is an endothermic process, the increase in temperature is conducive to the reaction, but too high a temperature is likely to cause side reactions. Long-term reaction at high temperature will cause the material to turn yellow, resulting in a darker product color. Therefore, the third temperature is controlled between 210°C and 220°C in this application, and the third predetermined time is controlled between 1 hour and 3 hours. The preset range of the vacuum degree can be -0.02MPa to -0.09MPa.

[0040] The method provided in the present application can be used to prepare polyester polyols with the following characteristics: the appearance is light yellow to yellow liquid; the hydroxyl value is 380 mgKOH / g to 440 mgKOH / g as measured according to the HG / T 2709-2022 polyester polyol hydroxyl value determination method; the acid value is less than or equal to 2 mgKOH / g as measured according to the HG / T 2708-1995 polyester polyol acid value determination method; the viscosity is 2500 mPa·s to 4500 mPa·s as measured according to the method specified in Chapter 4 of GB / T 10247-2008.

[0041] The following will be combined with the embodiments of the present application to clearly and completely describe the technical solution of the present application. Unless otherwise specified, the reagents and raw materials used can be purchased through commercial channels. The experimental methods in the following examples that do not specify specific conditions are selected according to conventional methods and conditions, or according to the product specifications.

[0042] The PBAT waste used in the following examples and comparative examples comes from the start-up and shutdown waste of the PBAT factory.

[0043] The hydroxyl value of the polyester polyol product is determined by the method A in HG / T 2709-2022, the acid value is determined by the acid value determination method of polyester polyol HG / T 2708-1995, and the viscosity is determined by the provisions of Chapter 4 in GB / T 10247-2008.

[0044] Example 1

[0045] This embodiment provides a method for preparing polyester polyol using PBAT waste, comprising the following steps:

[0046] (1) Under nitrogen protection, 35 parts of PBAT waste, 15 parts of phthalic anhydride, 15 parts of oleic acid, 30 parts of diethylene glycol, and 10 parts of glycerol were heated by weight to dissolve the materials, and then the temperature was raised to 180° C. and kept at this temperature for 2 hours to obtain a first reaction mixture;

[0047] (2) under nitrogen protection, adding 0.1 parts of zinc acetate to the first reaction mixture, then heating to 225° C. and keeping the temperature for 6 hours to react, thereby obtaining a polyester polyol having a light yellow transparent liquid appearance;

[0048] (3) Detect the acid value of the polyester polyol. When the acid value is below 10 mgKOH / g, cool to 210°C and gradually increase the vacuum degree to perform vacuum dehydration, maintaining the vacuum degree at -0.02 MPa to -0.09 MPa. After 2 hours of vacuum dehydration, take a sample to detect the acid value. When the acid value is below 2 mgKOH / g, stop the vacuum to obtain a polyester polyol product. The viscosity at 25°C is 2500 mPa·s, the hydroxyl value is 380 mgKOH / g, and the acid value is 1.5 mgKOH / g.

[0049] Example 2

[0050] The method for preparing polyester polyol using PBAT waste in this embodiment is different from that in embodiment 1 in that in step (2), 0.5 parts of zinc acetate are used and the heat preservation time is 4 hours to obtain a polyester polyol having a light yellow transparent liquid appearance. After step (3), the viscosity of the polyester polyol product at 25°C is measured to be 3000 Pa·s, the hydroxyl value is 400 mgKOH / g, and the acid value is 1.2 mgKOH / g.

[0051] Example 3

[0052] The method for preparing polyester polyols from PBAT waste in this embodiment is different from that in Example 1 in that in step (2), zinc acetate is replaced with stannous chloride to obtain a polyester polyol having a yellow turbid liquid appearance. After step (3), the viscosity of the polyester polyol product at 25°C is measured to be 3200 Pa·s, the hydroxyl value is 410 mgKOH / g, and the acid value is 1.5 mgKOH / g.

[0053] Example 4

[0054] The method for preparing polyester polyol using PBAT waste in this embodiment is different from that in Example 2 in that in step (2), zinc acetate is replaced by stannous chloride, the heat preservation time is 5 hours, and a polyester polyol with a light yellow transparent liquid appearance is obtained. After step (3), the viscosity of the polyester polyol product at 25°C is measured to be 3500 Pa·s, the hydroxyl value is 420 mgKOH / g, and the acid value is 1.3 mgKOH / g.

[0055] Example 5

[0056] The method for preparing polyester polyols using PBAT waste in this embodiment is different from that in Example 1 in that in step (2), zinc acetate is replaced with 0.1 parts of zinc acetate and 0.1 parts of stannous chloride, and the mixture is kept warm for 5 hours to obtain a polyester polyol having a yellow transparent liquid appearance. After step (3), the viscosity of the polyester polyol product at 25°C is measured to be 3400 Pa·s, the hydroxyl value is 400 mgKOH / g, and the acid value is 1.2 mgKOH / g.

[0057] Example 6

[0058] The method for preparing polyester polyols using PBAT waste in this embodiment is different from that in Example 2 in that in step (2), zinc acetate is replaced with 0.3 parts of zinc acetate and 0.2 parts of stannous chloride, and the mixture is kept warm for 3 hours to obtain a polyester polyol having a yellow transparent liquid appearance. After step (3), the viscosity of the polyester polyol product at 25°C is measured to be 3500 Pa·s, the hydroxyl value is 410 mgKOH / g, and the acid value is 1.1 mgKOH / g.

[0059] Comparative Example 1

[0060] The method for preparing polyester polyol using PBAT waste in this comparative example is different from that in Example 1 in that in step (2), zinc acetate is replaced by tetrabutyl titanate.

[0061] Comparative Example 2

[0062] The method for preparing polyester polyol using PBAT waste in this comparative example is different from that in Example 2 in that in step (2), zinc acetate is replaced by tetrabutyl titanate and the holding time is 6 hours.

[0063] PBAT conversion rate

[0064] Deionized water was added to the polyester polyol product, and after stirring and filtering, the undepolymerized PBAT waste in the filter cake was collected and dried and weighed. The conversion rate of the PBAT waste was obtained by the following method:

[0065] Conversion rate of PBAT waste = W PBAT -W0 / W PBAT ×100%;

[0066] Among them, W PBAT W0 is the weight of the undepolymerized PBAT waste.

[0067] Table 1 shows the PBAT conversion rates of Examples 1 to 6 and Comparative Examples 1 to 2. When tetrabutyl titanate is used as a catalyst, the PBAT conversion rate is low. Surprisingly, when zinc acetate and / or stannous chloride are used as catalysts, the PBAT conversion rate can be significantly improved, and the PBAT conversion rate can be as high as 95% or more. Further, when the catalyst contains zinc acetate, the PBAT conversion rate can reach 100%. In particular, when a mixed catalytic system of zinc acetate and stannous chloride is used, due to the synergistic effect of zinc acetate and stannous chloride, not only can the PBAT conversion rate be increased to 100%, but also the reaction time can be shortened when the catalyst dosage is constant.

[0068] Table 1 PBAT conversion rate calculation results

[0069]

[0070] The above description of the embodiments is to facilitate those of ordinary skill in the art to understand and apply the present application. It is obvious that those familiar with the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without having to pay creative labor. Therefore, the present application is not limited to the embodiments herein, and improvements and modifications made by those skilled in the art based on the contents disclosed in the present application without departing from the scope and spirit of the present application are within the scope of the present application.

Claims

1. A polyester polyol prepared from PBAT waste, characterized in that: The polyester polyol is prepared from the following raw materials in parts by weight: Wherein, the catalyst includes zinc acetate and / or stannous chloride.

2. The polyester polyol prepared from PBAT waste according to claim 1, characterized in that: In the catalyst, the weight ratio of the zinc acetate to the stannous chloride is (1-1.5):

1.

3. The polyester polyol prepared from PBAT waste according to claim 1, characterized in that: The raw materials meet any one or more of the following characteristics: (1) The aromatic anhydride includes phthalic anhydride; (2) The unsaturated fatty acid includes oleic acid; (3) The polyol includes 25 to 35 parts of diethylene glycol and 5 to 10 parts of glycerol.

4. A method for preparing polyester polyols using PBAT waste, characterized in that: The method is prepared by using the following raw materials in parts by weight: Wherein, the catalyst includes zinc acetate and / or stannous chloride.

5. The method for preparing polyester polyols using PBAT waste according to claim 4, characterized in that: The method comprises the following steps: Mixing and dissolving the PBAT waste, the aromatic anhydride, the unsaturated fatty acid and the polyol, and keeping the mixture at a first temperature for a first predetermined time to obtain a reaction mixture; After the catalyst is added to the reaction mixture, the temperature is raised to a second temperature and kept at the second predetermined time to react and obtain the polyester polyol.

6. The method for preparing polyester polyols using PBAT waste according to claim 5, characterized in that: The method satisfies any one or more of the following characteristics: 1) In the catalyst, the weight ratio of the zinc acetate to the stannous chloride is (1-1.5):1; 2) The aromatic anhydride includes phthalic anhydride; 3) The unsaturated fatty acid includes oleic acid; 4) The polyol includes 25 to 35 parts of diethylene glycol and 5 to 10 parts of glycerol; 5) The first temperature is 170° C. to 190° C., and the first predetermined time is 2 hours to 3 hours; 6) The second temperature is 210° C. to 225° C., and the second predetermined time is 3 hours to 6 hours.

7. The method for preparing polyester polyols using PBAT waste according to claim 5, characterized in that: The conversion rate of the PBAT waste is above 95%.

8. The method for preparing polyester polyols using PBAT waste according to claim 5, characterized in that: The method further comprises: making the acid value of the polyester polyol reach a final target acid value.

9. The method for preparing polyester polyols using PBAT waste according to claim 8, characterized in that: The method for making the acid value of the polyester polyol reach the target value comprises: detecting the acid value of the polyester polyol, when the acid value reaches the initial target acid value, cooling to a third temperature, gradually increasing the vacuum degree and maintaining the vacuum degree within a preset range, sampling and detecting the acid value after vacuum dehydration for a third predetermined time, and stopping the vacuum when the acid value reaches the final target acid value.

10. The method for preparing polyester polyols using PBAT waste according to claim 9, characterized in that: The initial target acid value is below 10 mgKOH / g, the final target acid value is below 2 mgKOH / g; the third temperature is 210°C to 220°C, the preset range is -0.02 MPa to -0.09 MPa, and the third predetermined time is 1 hour to 3 hours.

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