Bio-based polyester polyol based on waste polyester depolymerization monomer and preparation method of bio-based polyester polyol

Abstract

The invention discloses bio-based polyester polyol based on a waste polyester depolymerization monomer and a preparation method of the bio-based polyester polyol. The method comprises the following steps: 1) carrying out alcoholysis on waste PET polyester in ethylene glycol by using a catalyst, and carrying out purification treatment such as filtration, rotary evaporation, centrifugal washing and the like to obtain an alcoholysis monomer bis (2-hydroxyethyl) terephthalate; 2) mixing bis (2-hydroxyethyl) terephthalate and bio-based dimer acid according to different alcohol acid molar ratios, and adding a catalyst for reaction to obtain rough bio-based polyester polyol; and 3) purifying the rough bio-based polyester polyol obtained in the step 2) to obtain the pure bio-based polyester polyol. According to the method, the defects that traditional petroleum-based polyester is poor in biocompatibility and biodegradability and the like are overcome, recycling of resources is achieved, and the prepared bio-based polyester polyol is uniform in structure, narrow in molecular weight and good in heat resistance.

Description

Technical Field

[0001] The invention belongs to the field of bio-based materials, and specifically relates to a bio-based polyester polyol based on waste polyester depolymerization monomers and a preparation method thereof. Background Art

[0002] Polyethylene terephthalate (PET) is a polyester material that is widely used in the packaging field. With the development of society and the improvement of social methods, the use of PET beverage bottles is increasing. If the PET after consumption is discarded at will, it will not only cause environmental pollution, but also cause serious waste of resources. How to recycle and reuse the waste PET materials is a hot topic of concern.

[0003] Biomass resources come from nature, such as natural polymer materials or bio-based compounds, which are renewable and help reduce dependence on non-renewable resources such as petroleum. Using bio-based dimer acids such as bio-based hydrogenated dimer acid (HDA) to construct polymer materials can significantly reduce the complexity of the target network generated by the uncertainty of raw biomass.

[0004] Polyester polyol is a polymer obtained by esterification, polymerization and dehydration of polyacid and polyol under certain conditions. It is usually prepared by polycondensation or transesterification of organic dicarboxylic acid and polyol, and is widely used in the fields of polyurethane synthesis, packaging, electronics, etc. Currently, the commonly used polyols are petroleum-grade polyols, which are non-renewable and degradable, causing great pressure on the environment. Therefore, it is very necessary to develop environmentally friendly and high-performance bio-based polyols.

[0005] The Chinese patent application with publication number CN116535314A discloses a preparation method and application of a bio-based polyol, wherein the preparation method is to catalyze epoxidation of bio-based vegetable oil with carboxylic acid and hydrogen peroxide by strongly acidic cation exchange resin, filter and separate solid-liquid two phases, purify by vacuum distillation to obtain epoxidized vegetable oil, and adopt a ring-opening agent and epoxidized vegetable oil to catalyze ring opening by strongly acidic cation exchange resin, and purify by vacuum distillation to obtain vegetable oil-based polyol. Although this method can obtain polyols with different branched structures, this preparation method has cumbersome steps, complex purification process, large energy consumption, and the reaction efficiency and molecular weight of polyols prepared only by ring-opening reaction cannot be guaranteed, which will lead to a low yield of bio-based polyol. In addition, the bio-based polyol cannot have both toughness and strength at the same time, which limits its scope of application, so it is a very meaningful work to develop a bio-based polyol based on waste polyester depolymerization monomer based on the above technical background. Summary of the invention

[0006] In order to overcome the shortcomings and deficiencies of the prior art, the object of the present invention is to provide a bio-based polyester polyol based on waste polyester depolymerization monomers and a preparation method thereof.

[0007] The present invention utilizes ethylene glycol to depolymerize waste PET bottle flakes to obtain bis(2-hydroxyethyl) terephthalate (BHET), and utilizes bis(2-hydroxyethyl) terephthalate (BHET) and bio-based dimer acid to react to prepare bio-based polyester polyols. The obtained bio-based polyester polyols have stable molecular weight, good heat resistance and biodegradability, and can be further used to prepare bio-based polyester materials with biodegradability. The present invention realizes the high-value reuse of waste polyester and biomass resources, and the raw materials are cheap and abundant in resources. The molecular weight of the bio-based polyester polyol can be adjusted according to the needs of users, and the performance requirements of users for bio-based polyester materials are met, and the bio-based polyester polyols have good development prospects. The bio-based polyester polyols of the present invention are applied to the fields of biodegradable materials, medical materials and food packaging materials.

[0008] The purpose of the present invention is implemented through the following technical solutions.

[0009] A bio-based polyester polyol based on waste polyester depolymerization monomers, mainly prepared from the following raw materials in parts by weight:

[0010]

[0011]

[0012] The waste polyester is waste PET.

[0013] The catalyst is one or more of tetrabutyl titanate, p-toluenesulfonic acid, dibutyltin dilaurate, and dibutyltin diacetate;

[0014] The organic solvent is one or more of N,N-dimethylformamide, N-methylpyrrolidone and butanone.

[0015] The bio-based dimer acid is one or more of hydrogenated dimer acid (HDA) and dimer acid (DA).

[0016] The molecular weight of the bio-based dimer acid is 400-600.

[0017] The present invention also provides a method for preparing bio-based polyester polyols based on waste polyester depolymerization monomers, comprising the following steps:

[0018] 1) Under a protective atmosphere, waste PET bottle flakes and diol are reacted at 180-200° C. for 2-6 hours under the action of zinc acetate catalyst, filtered, rotary evaporated, centrifuged, washed, cooled, crystallized, and dried to obtain depolymerized monomer bis(2-hydroxyethyl) terephthalate;

[0019] 2) dissolving bis(2-hydroxyethyl) terephthalate in an organic solvent and mixing with bio-based dimer acid, adding a catalyst, performing an esterification reaction at 140-160° C. for 2-4 hours, and then performing a polycondensation reaction at 180-200° C. for 1-3 hours; obtaining a rough bio-based polyester polyol;

[0020] 3) Dissolving the crude bio-based polyol in a polar solvent, then dropping the mixture into methanol, stirring until the bio-based polyol is completely extracted, and finally filtering and drying to obtain purified bio-based polyol.

[0021] The diol is ethylene glycol.

[0022] The mass ratio of the waste PET to the diol is 1:(2-4); the amount of the catalyst used is 1-3% of the mass of the waste PET.

[0023] The catalyst is one or more of zinc acetate, nickel acetate, manganese acetate and copper acetate.

[0024] The organic solvent in step 2) is one or more of N,N-dimethylformamide, N-methylpyrrolidone and butanone.

[0025] The weight ratio of the organic solvent to BHET in step 2) is (8-20): (4-8).

[0026] The step 2) of dissolving bis(2-hydroxyethyl) terephthalate in an organic solvent is carried out in a molar ratio of alcohol to acid in the range of 1.2 to 2.

[0027] The catalyst in step 2) is one or more of tetrabutyl titanate, p-toluenesulfonic acid, dibutyltin dilaurate, and dibutyltin diacetate.

[0028] The amount of the catalyst in step 2) is 1-3% of the mass of the bio-based dimer acid;

[0029] The polar solvent in step 3) is one or more of chloroform, dichloromethane and tetrahydrofuran.

[0030] In the bio-based polyester polyol of the present invention, the depolymerized monomer bis(2-hydroxyethyl) terephthalate (BHET) is a rigid structure with a benzene ring, has a high elastic modulus and heat resistance, and exists as a small molecule diol in an alkyd condensation reaction; the bio-based dimer acid is derived from natural biomass, has an aliphatic long-chain structure, a large molecular weight and toughness, and reacts with BHET to generate a bio-based polyester polyol with certain strength, toughness and degradability.

[0031] The present invention measures the molecular structure of bio-based polyester polyol by hydrogen nuclear magnetic resonance spectroscopy.

[0032] The present invention measures the molecular weight of bio-based polyester polyols by gel permeation chromatography.

[0033] The present invention measures the heat resistance of bio-based polyester polyol by thermogravimetric method.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The present invention introduces bis(2-hydroxyethyl) terephthalate (BHET), a depolymerized monomer of waste PET with a benzene ring structure, as a diol in the alkyd condensation reaction into the synthesis design of bio-based polyester polyols, thereby improving the strength and heat resistance of the polyester polyols, and can be used to produce high-performance bio-based polyester products.

[0036] 2. The bio-based dimer acid used in the present invention is an environmentally friendly aliphatic diacid derived from biomass resources and has a relatively long flexible chain segment. It can be introduced into the synthetic design of bio-based polyester polyols as a dibasic acid in an alkyd condensation reaction, thereby imparting flexibility to the polyester polyols and can be used to produce biodegradable polyester materials.

[0037] 3. The preparation of the bio-based polyester polyol of the present invention is convenient and efficient, and can be synthesized without strict reduced pressure conditions during the polycondensation reaction, and the yield is relatively high.

[0038] 4. The bio-based polyester polyol of the present invention has a relatively uniform component, a narrow molecular weight distribution, and good heat resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of the preparation of bio-based polyester polyols;

[0040] Figure 2 It is the H NMR spectrum of bis(2-hydroxyethyl) terephthalate (BHET), bio-based hydrogenated dimer acid (HDA), and bio-based polyester polyol;

[0041] Figure 3 The molecular weight distribution diagram of the bio-based polyester polyols prepared at different alcohol-acid molar ratios in Examples 1 to 3;

[0042] Figure 4 Graph showing the heat resistance of bio-based polyols prepared at different alcohol-acid molar ratios. DETAILED DESCRIPTION

[0043] The specific implementation of the present invention is further described below in conjunction with examples, but the implementation of the present invention is not limited thereto.

[0044] Figure 1The schematic diagram of the preparation of bio-based polyester polyols in Examples 1 to 3 represents the reaction mechanism of different alcohol-acid molar ratios.

[0045] Figure 2 The nuclear magnetic resonance hydrogen spectrum of the bio-based polyester polyol is the nuclear magnetic resonance hydrogen spectrum of the polyester polyol in Example 3 when the alcohol-acid ratio is 1.5:1.

[0046] Example 1

[0047] (1) Waste PET bottle flakes and ethylene glycol are mixed in a mass ratio of 1:3 and 2 wt% of a catalyst zinc acetate (2% of the mass of the waste PET) are added to a reaction container, stirred and reacted at 190° C. for 4 h, and the product is filtered, rotary evaporated, cooled and crystallized, centrifuged and washed, and dried to obtain a depolymerized monomer bis(2-hydroxyethyl) terephthalate (BHET).

[0048] (2) According to the alcohol-acid molar ratio of 1.2:1, 4.28 parts by weight of bis(2-hydroxyethyl) terephthalate (BHET) was dissolved in 8 parts by weight of N,N-dimethylformamide and added to the reactor, and then 8 parts by weight of bio-based hydrogenated dimer acid (HDA) and 0.16 parts by weight of catalyst tetrabutyl titanate were added, and the mixture was stirred at 150°C at 100 rpm for 3 hours, and then stirred at 190°C at 100 rpm for 2 hours to obtain a rough bio-based polyester polyol.

[0049] (3) The crude bio-based polyester polyol in step (2) is dissolved in 20 parts by weight of chloroform, and then the mixture is dropped into 20 parts by weight of methanol, and stirred until the bio-based polyester polyol is completely extracted, and finally filtered and dried to obtain purified bio-based polyol.

[0050] The preparation principle diagram of the bio-based polyester polyol prepared in this embodiment is as follows Figure 1 As shown. Figure 1 It can be seen that the carboxyl group of HDA and the hydroxyl group of BHET can undergo esterification and polycondensation reaction to polymerize into bio-based polyester polyol. Different alcohol-acid ratios will lead to different polymerization degrees. Generally speaking, the closer the alcohol-acid ratio is to 1, the greater the theoretical polymerization degree. The molecular weight distribution diagram of the bio-based polyester polyol prepared in this example is shown in FIG. Figure 3 As shown. Figure 3 It can be seen that when the molar ratio of alkyd to acid is 1.2:1, the molecular weight distribution of the prepared bio-based polyester polyol is the narrowest and more uniform, with an average molecular weight of 2514 g / mol, which can meet the application requirements of bio-based polyester polyol in materials such as polyurethane. Figure 4 As shown. Figure 4It can be seen that the initial thermal decomposition temperature of bio-based polyester polyol increases with the increase of the alkyd-acid ratio. This is because when the alkyd-acid ratio increases, the BHET content increases, and the rigid benzene ring content in BHET increases, thereby improving the heat resistance of the polyol. When the alkyd-acid ratio is 1.2:1, the bio-based polyester polyol still has a high decomposition temperature and good heat resistance.

[0051] Example 2

[0052] (1) Waste PET bottle flakes and ethylene glycol are mixed in a mass ratio of 1:3 and 2 wt% of a catalyst zinc acetate (2% of the mass of the waste PET) are added to a reaction container, stirred and reacted at 190° C. for 4 h, and the product is filtered, rotary evaporated, cooled and crystallized, centrifuged and washed, and dried to obtain a depolymerized monomer bis(2-hydroxyethyl) terephthalate (BHET).

[0053] (2) According to the alcohol-acid molar ratio of 1.5:1, 5.35 parts by weight of bis(2-hydroxyethyl) terephthalate (BHET) was dissolved in 12 parts by weight of N,N-dimethylformamide and added to the reactor, and then 8 parts by weight of bio-based hydrogenated dimer acid (HDA) and 0.16 parts by weight of catalyst tetrabutyl titanate were added, and the mixture was stirred at 150°C at 100 rpm for 3 hours, and then stirred at 190°C at 100 rpm for 2 hours to obtain a rough bio-based polyester polyol.

[0054] (3) The crude bio-based polyester polyol in step (2) is dissolved in 24 parts by weight of chloroform, and then the mixture is dropped into 24 parts by weight of methanol, and stirred until the bio-based polyester polyol is completely extracted, and finally filtered and dried to obtain purified bio-based polyol.

[0055] The preparation principle diagram of the bio-based polyester polyol prepared in this embodiment is as follows Figure 1 As shown. Figure 1 It can be seen that the carboxyl group of HDA and the hydroxyl group of BHET can undergo esterification and polycondensation reaction to polymerize into bio-based polyester polyol. Different alcohol-acid ratios will lead to different polymerization degrees. Generally speaking, the closer the alcohol-acid ratio is to 1, the greater the theoretical polymerization degree. The H NMR spectrum of the bio-based polyester polyol prepared in this example is shown in FIG. Figure 2 As shown. Figure 2 It can be seen that the prepared bio-based polyester polyol has a characteristic absorption peak of bio-based hydrogenated dimer acid HDA in the chemical shift range of 0-3ppm, a resonance peak of benzene ring hydrogen on the depolymerized monomer BHET in the chemical shift range of 8-8.5ppm, and a peak at 4-5ppm belongs to the methylene resonance peak at the covalent bond connection formed by the reaction of BHET and HDA. Therefore, it can be shown that the reaction of BHET and HDA successfully prepared bio-based polyester polyol. The molecular weight distribution diagram of the bio-based polyester polyol prepared in this example is shown in FIG. Figure 3 As shown. Figure 3 It can be seen that when the molar ratio of alkyd to acid is 1.5:1, the molecular weight distribution of the prepared bio-based polyester polyol is narrow and very uniform, with an average molecular weight of 2063 g / mol, which can meet the application requirements of bio-based polyester polyol in materials such as polyurethane. Figure 4 As shown. Figure 4 It can be seen that the initial thermal decomposition temperature of bio-based polyester polyol increases with the increase of the alkyd-acid ratio. This is because when the alkyd-acid ratio increases, the BHET content increases, and the rigid benzene ring content in BHET increases, thereby improving the heat resistance of the polyol. When the alkyd-acid ratio is 1.5:1, the bio-based polyester polyol has a high decomposition temperature and good heat resistance.

[0056] Example 3

[0057] (1) Waste PET bottle flakes and ethylene glycol are mixed in a mass ratio of 1:3 and 2 wt% of a catalyst zinc acetate (2% of the mass of the waste PET) are added to a reaction container, stirred and reacted at 190° C. for 4 h, and the product is filtered, rotary evaporated, cooled and crystallized, centrifuged and washed, and dried to obtain a depolymerized monomer bis(2-hydroxyethyl) terephthalate (BHET).

[0058] (2) According to the alcohol-acid molar ratio of 1.8:1, 6.42 parts by weight of bis(2-hydroxyethyl) terephthalate (BHET) was dissolved in 16 parts by weight of N,N-dimethylformamide and added to the reactor, and then 8 parts by weight of bio-based hydrogenated dimer acid (HDA) and 0.16 parts by weight of catalyst tetrabutyl titanate were added, and the mixture was stirred at 150°C at 100 rpm for 3 hours, and then stirred at 190°C at 100 rpm for 2 hours to obtain a rough bio-based polyester polyol.

[0059] (3) The crude bio-based polyester polyol in step (2) is dissolved in 30 parts by weight of chloroform, and then the mixture is dropped into 30 parts by weight of methanol, and stirred until the bio-based polyester polyol is completely extracted, and finally filtered and dried to obtain purified bio-based polyol.

[0060] The preparation principle diagram of the bio-based polyester polyol prepared in this embodiment is as follows Figure 1 As shown. Figure 1 It can be seen that the carboxyl group of HDA and the hydroxyl group of BHET can undergo esterification and polycondensation reaction to polymerize into bio-based polyester polyol. Different alcohol-acid ratios will lead to different polymerization degrees. Generally speaking, the closer the alcohol-acid ratio is to 1, the greater the theoretical polymerization degree. The molecular weight distribution diagram of the bio-based polyester polyol prepared in this example is shown in FIG. Figure 3 As shown. Figure 3It can be seen that when the molar ratio of alkyd to acid is 1.8:1, the molecular weight distribution of the prepared bio-based polyester polyol is the narrowest and more uniform, with an average molecular weight of 1082 g / mol, which can meet the application requirements of bio-based polyester polyol in materials such as polyurethane. Figure 4 As shown. Figure 4 It can be seen that the initial thermal decomposition temperature of bio-based polyester polyol increases with the increase of the alkyd-acid ratio. This is because when the alkyd-acid ratio increases, the BHET content increases, and the rigid benzene ring content in BHET increases, thereby improving the heat resistance of the polyol. When the alkyd-acid ratio is 1.8:1, the bio-based polyester polyol has the highest decomposition temperature and good heat resistance.

[0061] Example 4

[0062] (1) Waste PET bottle flakes and ethylene glycol are mixed in a mass ratio of 1:3 and 2 wt% of a catalyst zinc acetate (2% of the mass of the waste PET) are added to a reaction container, stirred and reacted at 190° C. for 4 h, and the product is filtered, rotary evaporated, cooled and crystallized, centrifuged and washed, and dried to obtain a depolymerized monomer bis(2-hydroxyethyl) terephthalate (BHET).

[0063] (2) According to the alcohol-acid molar ratio of 2:1, 7.14 parts by weight of bis(2-hydroxyethyl) terephthalate (BHET) was dissolved in 20 parts by weight of N,N-dimethylformamide and added to the reactor, and then 8 parts by weight of bio-based hydrogenated dimer acid (HDA) and 0.16 parts by weight of catalyst tetrabutyl titanate were added, and the mixture was stirred at 150°C at 100 rpm for 3 hours, and then stirred at 190°C at 100 rpm for 2 hours to obtain a rough bio-based polyester polyol.

[0064] (3) The crude bio-based polyester polyol in step (2) is dissolved in 35 parts by weight of chloroform, and then the mixture is dropped into 35 parts by weight of methanol, and stirred until the bio-based polyester polyol is completely extracted, and finally filtered and dried to obtain purified bio-based polyol.

Claims

1. A bio-based polyester polyol based on depolymerized monomers of waste polyester, characterized in that: It is prepared from the following raw materials in parts by weight:

2. The bio-based polyester polyol based on waste polyester depolymerization monomers according to claim 1, characterized in that: The waste polyester is waste PET.

3. The bio-based polyester polyol based on depolymerized monomers of waste polyester according to claim 1, characterized in that: The catalyst is one or more of tetrabutyl titanate, p-toluenesulfonic acid, dibutyltin dilaurate, and dibutyltin diacetate.

4. The bio-based polyester polyol based on waste polyester depolymerization monomers according to claim 1, characterized in that: The organic solvent is one or more of N,N-dimethylformamide, N-methylpyrrolidone and butanone.

5. The bio-based polyester polyol based on waste polyester depolymerization monomers according to claim 1, characterized in that: The bio-based dimer acid is one or more of hydrogenated dimer acid (HDA) and dimer acid (DA).

6. The bio-based polyester polyol based on depolymerized monomers of waste polyester according to claim 5, characterized in that: The molecular weight of the bio-based dimer acid is 400-600.

7. A method for preparing bio-based polyester polyols based on depolymerized monomers of waste polyester, characterized in that: The following steps are involved: 1) Under a protective atmosphere, waste PET bottle flakes and diol are reacted at 180-200° C. for 2-6 hours under the action of zinc acetate catalyst, filtered, rotary evaporated, centrifuged, washed, cooled, crystallized, and dried to obtain depolymerized monomer bis(2-hydroxyethyl) terephthalate; 2) dissolving bis(2-hydroxyethyl) terephthalate in an organic solvent and mixing with bio-based dimer acid, adding a catalyst, performing an esterification reaction at 140-160° C. for 2-4 hours, and then performing a polycondensation reaction at 180-200° C. for 1-3 hours; obtaining a rough bio-based polyester polyol; 3) Dissolving the crude bio-based polyol in a polar solvent, then dropping the mixture into methanol, stirring until the bio-based polyol is completely extracted, and finally filtering and drying to obtain purified bio-based polyol.

8. The method according to claim 7, characterized in that The diol is ethylene glycol.

9. The method according to claim 7, characterized in that: The mass ratio of the waste PET to the diol is 1:(2-4); preferably, the amount of the catalyst is 1-3% of the mass of the waste PET, and preferably, the catalyst is one or more of zinc acetate, nickel acetate, manganese acetate, and copper acetate.

10. The method according to claim 7, characterized in that The organic solvent in step 2) is one or more of N,N-dimethylformamide, N-methylpyrrolidone, and butanone; preferably, the weight ratio of the organic solvent to BHET in step 2) is (8-20): (4-8), preferably, the bis(2-hydroxyethyl) terephthalate is dissolved in the organic solvent in step 2) according to the alcohol acid molar ratio range of 1.2 to 2, preferably, the catalyst in step 2) is one or more of tetrabutyl titanate, p-toluenesulfonic acid, dibutyltin dilaurate, and dibutyltin diacetate, preferably, the amount of the catalyst in step 2) is 1-3% of the mass of the bio-based dimer acid; preferably, the polar solvent in step 3) is one or more of chloroform, dichloromethane, and tetrahydrofuran.

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