A bio-based polycarbonate diol and its preparation method

Abstract

The present invention provides a bio-based polycarbonate diol and a preparation method thereof, belonging to the field of bio-based polycarbonate diol. The preparation method of the bio-based polycarbonate diol comprises the following steps: material preparation, ester exchange, and polymerization, including the use of bio-based 1,4-butanediol and diol to prepare the bio-based polycarbonate diol. The preparation method of the bio-based polycarbonate diol of the present invention effectively avoids the adverse effects of catalyst residues on the application performance of the polycarbonate diol, further improves the physical properties and chemical corrosion resistance of the obtained polyurethane elastomer; at the same time, the obtained polycarbonate diol has a stable hydroxyl value, a narrow molecular weight distribution, a high bio-based carbon content, and a high-quality polycarbonate diol product.

Description

Technical Field

[0001] The present invention relates to the field of bio-based polycarbonate diol, in particular to a bio-based polycarbonate diol and a preparation method thereof. Background Art

[0002] Polycarbonate diol (PCDL) is a polymer with multiple carbonate groups within the molecule and hydroxyl groups at both ends. It can be used to synthesize polycarbonate polyurethanes. Compared to polyurethane materials synthesized from traditional polyols, PCDLs exhibit superior mechanical properties, hydrolysis resistance, heat resistance, oxidation resistance, and wear resistance. Consequently, the development of PCDLs and corresponding new PCDL materials is gaining increasing attention within the industry. Currently, PCDLs are widely used in the preparation of various polyurethane materials.

[0003] In recent years, with growing environmental awareness and increasingly stringent environmental regulations, traditional solvent-based polyurethane materials have gradually shifted towards waterborne polyurethanes. However, the introduction of hydrophilic groups into waterborne polyurethanes generally compromises their water resistance. Using polycarbonate diols instead of traditional polyols to synthesize waterborne polyurethanes effectively addresses this issue and improves the material's water resistance. Consequently, polycarbonate diols have gained widespread application in the synthesis of waterborne polyurethanes.

[0004] Polycarbonate-based polyurethanes have excellent resistance to in vivo oxidation and are widely used in aqueous environments and for long-term implantable medical devices. Furthermore, polycarbonate diols are microbially degradable, making them suitable for development as environmentally friendly materials. Consequently, research on polycarbonate diols is growing.

[0005] In the existing art, polycarbonate diols are synthesized using the following methods: phosgene, carbon dioxide-epoxide-mediated copolymerization, ring-opening polymerization of cyclic carbonates, and transesterification of small molecule carbonates. The main technical route involves the polymerization of dimethyl carbonate and a dihydroxy compound under catalytic conditions to produce polycarbonate diol. The dihydroxy compound is typically an aliphatic diol.

[0006] However, the inventors have discovered through research that, in actual applications, the existing catalysts for the polymerization of polycarbonate diols are difficult to effectively separate after the polymerization reaction is completed, and the residual catalyst affects the application performance of the polycarbonate diol. The physical properties and chemical corrosion resistance of the polyurethane elastomers produced using the catalysts need to be further improved. At the same time, the existing industrial preparation methods for polycarbonate diols also have the problem that the hydroxyl value of the polycarbonate diols produced is unstable and the molecular weight distribution is wide, which affects the quality and application of the polycarbonate diol products. Summary of the Invention

[0007] In order to solve the technical problems existing in the prior art, the present invention provides a bio-based polycarbonate diol and a preparation method thereof, which effectively solves the problem in the prior art that the catalyst is difficult to effectively separate after the polymerization reaction is completed, effectively avoids the adverse effects of catalyst residues on the application performance of the polycarbonate diol, and further improves the physical properties and chemical corrosion resistance of the prepared polyurethane elastomer; at the same time, the prepared polycarbonate diol has a stable hydroxyl value and a narrow molecular weight distribution, and the polycarbonate diol product is of good quality, which can be used in subsequent applications of the polycarbonate diol.

[0008] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0009] A method for preparing bio-based polycarbonate diol comprises the following steps: material preparation, ester exchange, and polymerization.

[0010] The raw material preparation comprises mixing bio-based 1,4-butanediol and diol, and keeping the mixture at 30-40° C. for 15-30 minutes to obtain a raw material liquid; or using bio-based 1,4-butanediol as the raw material liquid.

[0011] In the prepared material, the molar ratio of bio-based 1,4-butanediol to diol is 3-4:1.

[0012] The diol is preferably one of the following: 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol;

[0013] The diol is more preferably 1,5-pentanediol or 1,6-hexanediol.

[0014] The transesterification step comprises introducing the raw material liquid and carbonate into a reaction device filled with a catalyst, adjusting the pressure in the reactor to 5-10 kPa under nitrogen atmosphere, and stirring for a certain period of time; then heating to 150-170° C., maintaining the temperature and reflux reaction for 4-10 hours, closing the reflux, and distilling to recover the azeotropic methanol and carbonate, thereby completing the transesterification step.

[0015] In the transesterification, the carbonate is one of the following: ethylene carbonate, dimethyl carbonate, diethyl carbonate, diphenyl carbonate, dibutyl carbonate;

[0016] The carbonate ester is more preferably ethylene carbonate or dimethyl carbonate.

[0017] During the transesterification, the heating rate is 1-3°C / min;

[0018] The weight ratio of the raw material liquid, the carbonate ester and the catalyst is 100:60-70:3-4.

[0019] The catalyst is prepared by the following steps: pretreatment and loading.

[0020] The pretreatment comprises placing the hydroxyapatite in a nitrogen atmosphere, heating it to 200-300° C., keeping it warm for 30-60 minutes, naturally cooling it to 55-65° C., adding it to 3-6 times the volume of a pretreatment liquid, adjusting the temperature of the pretreatment liquid to 60-70° C., keeping it warm for 2-3 hours, filtering it out, keeping it warm and drying it at 95-105° C. for 2-3 hours, heating it to 350-400° C., keeping it warm and roasting it for 3-4 hours, and granulating it into 10-20 meshes to obtain a pretreated material.

[0021] In the pretreatment, the particle size of hydroxyapatite is 5-8 μm;

[0022] The pretreatment liquid is a deionized water solution containing potassium nitrate, strontium nitrate and copper nitrate. In the pretreatment liquid, the concentration of potassium nitrate is 5-6wt%, the concentration of strontium nitrate is 1-1.3wt% and the concentration of copper nitrate is 2-2.5wt%.

[0023] The loading is carried out by adding the pretreated material into 3-4 times the volume of the loading liquid, heating to 40-50° C., keeping the temperature and standing for 6-8 hours, filtering out, placing in a vacuum environment of 0.03-0.05 MPa, keeping the temperature and drying at 70-80° C. to constant weight, thereby preparing the catalyst.

[0024] The loading liquid is an ethanol solution containing triethylenediamine and tetrabutyl titanate, wherein the weight ratio of triethylenediamine, tetrabutyl titanate and ethanol is 2-3:1-1.5:100.

[0025] After the polymerization and transesterification steps are completed, the vacuum degree in the reactor is adjusted to 0.01-0.03 MPa, the temperature is raised to 200-220° C., and the polymerization is carried out by heat preservation for 3-5 hours. The monomers and low molecular weight polycarbonate are then removed by distillation, and the solid matter is filtered out to obtain bio-based polycarbonate diol.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The method for preparing bio-based polycarbonate diol of the present invention uses bio-based 1,4-butanediol as a raw material for the preparation of polycarbonate diol; a pre-treated and loaded specific catalyst is provided in the transesterification step; the bio-based polycarbonate diol obtained through the transesterification and polymerization steps effectively solves the problem in the prior art that the catalyst is difficult to effectively separate after the polymerization reaction is completed, effectively avoids the adverse effects of catalyst residues on the application performance of the polycarbonate diol, and further improves the physical properties and chemical corrosion resistance of the obtained polyurethane elastomer; at the same time, the obtained polycarbonate diol has a stable hydroxyl value, a narrow molecular weight distribution, a high bio-based carbon content, and a good quality of the polycarbonate diol product, and utilizes the subsequent application of the polycarbonate diol.

[0028] (2) The preparation method of the bio-based polycarbonate diol of the present invention has a hydroxyl value of 58.7-61.6 mgKOH / g, a molecular weight of 1822-1913, a stable hydroxyl value, and a narrow molecular weight distribution; at the same time, the acid value of the bio-based polycarbonate diol is 0.010-0.013 mgKOH / g, the bio-based carbon content is 20-80 wt%, and the moisture content is less than 24 ppm. The product quality is good and the subsequent application of the polycarbonate diol is utilized.

[0029] (3) The preparation method of the bio-based polycarbonate diol of the present invention has a tensile strength of 32.9-35.7 MPa and an elongation at break of 618-632%. Under low temperature (-20°C), the stress at 100% elongation is 8.1-9.1 MPa, and the physical properties are good.

[0030] (4) The method for preparing the bio-based polycarbonate diol of the present invention has good chemical corrosion resistance. According to tests, the oleic acid resistance (weight gain rate) of the bio-based polycarbonate diol is 8.1-9.0%, and the ethanol resistance (weight gain rate) is 7.3-8.1%.

[0031] (5) The preparation method of the bio-based polycarbonate diol of the present invention has a simple process flow and mild process conditions, and is suitable for large-scale industrial production. DETAILED DESCRIPTION

[0032] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described.

[0033] Example 1

[0034] A method for preparing bio-based polycarbonate diol, specifically comprising:

[0035] 1. Prepare ingredients

[0036] The bio-based 1,4-butanediol was pumped into the 1,4-butanediol metering high-level tank by a feed pump; the diol was pumped into the diol metering high-level tank by a feed pump; the bio-based 1,4-butanediol and diol were respectively measured and introduced into the preparation kettle, kept warm and stirred for 15 minutes at 30°C to obtain the raw material liquid.

[0037] Among them, the diol is 1,5-pentanediol.

[0038] The molar ratio of bio-based 1,4-butanediol to 1,5-pentanediol is 3:1.

[0039] 2. Transesterification

[0040] The raw material liquid and ethylene carbonate were introduced into a reactor filled with a catalyst. After the air in the reactor was completely replaced with nitrogen, the pressure in the reactor was adjusted to 5KPa and stirred for 10 minutes. Then, the temperature was increased to 150°C at a heating rate of 1°C / min, and the mixture was kept at reflux for 4 hours. After that, the reflux was turned off and the azeotropic methanol and ethylene carbonate were recovered by distillation to complete the ester exchange step.

[0041] The weight ratio of the raw material liquid, ethylene carbonate and catalyst is 100:60:3.

[0042] The catalyst is prepared by the following method:

[0043] 1) Preprocessing

[0044] The hydroxyapatite was placed in a nitrogen atmosphere, heated to 200°C, kept warm for 30 minutes, and then naturally cooled to 55°C. The hydroxyapatite was added into 3 times the volume of the pretreatment liquid, and the temperature of the pretreatment liquid was adjusted to 60°C. The pretreatment liquid was kept warm for 2 hours and then filtered out. The pretreatment liquid was dried at 95°C for 2 hours, heated to 350°C, kept warm and calcined for 3 hours, and granulated into 10 mesh to obtain a pretreated material.

[0045] The particle size of hydroxyapatite is 5 μm.

[0046] The pretreatment liquid is a deionized water solution containing potassium nitrate, strontium nitrate and copper nitrate. In the pretreatment liquid, the concentration of potassium nitrate is 5 wt %, the concentration of strontium nitrate is 1 wt % and the concentration of copper nitrate is 2 wt %.

[0047] 2) Load

[0048] The pretreated product was added to 3 times the volume of the loading liquid, heated to 40°C, kept still for 6 hours, filtered out, placed in a vacuum environment of 0.03 MPa, and dried at 70°C to constant weight to obtain a catalyst.

[0049] The loading liquid is prepared by adding triethylenediamine and tetrabutyl titanate into ethanol and stirring until completely dissolved. The weight ratio of triethylenediamine, tetrabutyl titanate, and ethanol is 2:1:100.

[0050] 3. Aggregation

[0051] After the transesterification step is completed, the vacuum degree in the reactor is adjusted to 0.01 MPa, the temperature is raised to 200° C., and the polymerization is carried out by heat preservation for 3 hours. The monomers and low molecular weight polycarbonate are then distilled off, and the solid matter is filtered out to obtain bio-based polycarbonate diol.

[0052] The bio-based polycarbonate diol prepared in this example has a number average molecular weight of 1822, a hydroxyl value of 61.6 mgKOH / g, an acid value of 0.013 mgKOH / g, a bio-based carbon content of 52.9 wt %, and a moisture content of 24 ppm.

[0053] Example 2

[0054] A method for preparing bio-based polycarbonate diol, specifically comprising:

[0055] 1. Prepare ingredients

[0056] The bio-based 1,4-butanediol was pumped into the 1,4-butanediol metering high-level tank by a feed pump; the diol was pumped into the diol metering high-level tank by a feed pump; the bio-based 1,4-butanediol and diol were respectively measured and introduced into the preparation kettle, kept warm and stirred at 35°C for 20 minutes to obtain the raw material liquid.

[0057] Among them, the diol is 1,5-pentanediol.

[0058] The molar ratio of bio-based 1,4-butanediol to 1,5-pentanediol is 3.5:1.

[0059] 2. Transesterification

[0060] The raw material liquid and ethylene carbonate were introduced into a reactor filled with a catalyst. After the air in the reactor was completely replaced with nitrogen, the pressure in the reactor was adjusted to 5 kPa and stirred for 30 minutes. Then, the temperature was increased to 170°C at a heating rate of 1.5°C / min, and the mixture was kept at reflux for 8 hours. After that, the reflux was turned off and the azeotropic methanol and ethylene carbonate were recovered by distillation to complete the ester exchange step.

[0061] The weight ratio of the raw material liquid, ethylene carbonate and catalyst is 100:65:3.2.

[0062] The catalyst is prepared by the following method:

[0063] 1) Preprocessing

[0064] The hydroxyapatite was placed in a nitrogen atmosphere, heated to 250°C, kept warm for 60 minutes, and then naturally cooled to 60°C. The hydroxyapatite was added into 4 times the volume of the pretreatment liquid, and the temperature of the pretreatment liquid was adjusted to 65°C. After keeping warm for 3 hours, it was filtered out and dried at 105°C for 3 hours. The temperature was then raised to 400°C, kept warm and calcined for 4 hours, and granulated into 15 mesh to obtain a pretreated material.

[0065] The particle size of hydroxyapatite is 6 μm.

[0066] The pretreatment liquid is a deionized water solution containing potassium nitrate, strontium nitrate and copper nitrate. In the pretreatment liquid, the concentration of potassium nitrate is 5.5 wt %, the concentration of strontium nitrate is 1.3 wt % and the concentration of copper nitrate is 2.5 wt %.

[0067] 2) Load

[0068] The pretreated product was added to 4 times the volume of the loading liquid, heated to 50°C, kept at this temperature for 8 hours, filtered out, placed in a vacuum environment of 0.05 MPa, and dried at 75°C to constant weight to obtain a catalyst.

[0069] The loading liquid is prepared by adding triethylenediamine and tetrabutyl titanate into ethanol and stirring until completely dissolved. The weight ratio of triethylenediamine, tetrabutyl titanate, and ethanol is 2.5:1.2:100.

[0070] 3. Aggregation

[0071] After the transesterification step is completed, the vacuum degree in the reactor is adjusted to 0.02 MPa, the temperature is raised to 200° C., and the polymerization is carried out by heat preservation for 4 hours. The monomers and low molecular weight polycarbonate are then distilled off, and the solid matter is filtered out to obtain bio-based polycarbonate diol.

[0072] The bio-based polycarbonate diol prepared in this example has a number average molecular weight of 1886, a hydroxyl value of 59.5 mgKOH / g, an acid value of 0.01 mgKOH / g, a bio-based carbon content of 56.9 wt %, and a moisture content of 18 ppm.

[0073] Example 3

[0074] A method for preparing bio-based polycarbonate diol, specifically comprising:

[0075] 1. Prepare ingredients

[0076] The bio-based 1,4-butanediol is pumped into the 1,4-butanediol metering high-level tank using a feed pump, and after metering, it is introduced into the preparation kettle to obtain the raw material liquid.

[0077] 2. Transesterification

[0078] The raw material liquid and ethylene carbonate were introduced into a reactor filled with a catalyst. After the air in the reactor was completely replaced with nitrogen, the pressure in the reactor was adjusted to 5 kPa and stirred for 30 minutes. Then, the temperature was increased to 170°C at a heating rate of 1.5°C / min, and the mixture was kept at reflux for 8 hours. After that, the reflux was turned off and the azeotropic methanol and ethylene carbonate were recovered by distillation to complete the ester exchange step.

[0079] The weight ratio of the raw material liquid, ethylene carbonate and catalyst is 100:65:3.2.

[0080] The catalyst is prepared by the following method:

[0081] 1) Preprocessing

[0082] The hydroxyapatite was placed in a nitrogen atmosphere, heated to 250°C, kept warm for 60 minutes, and then naturally cooled to 60°C. The hydroxyapatite was added into 4 times the volume of the pretreatment liquid, and the temperature of the pretreatment liquid was adjusted to 65°C. After keeping warm for 3 hours, it was filtered out and dried at 105°C for 3 hours. The temperature was then raised to 400°C, kept warm and calcined for 4 hours, and granulated into 15 mesh to obtain a pretreated material.

[0083] The particle size of hydroxyapatite is 6 μm.

[0084] The pretreatment liquid is a deionized water solution containing potassium nitrate, strontium nitrate and copper nitrate. In the pretreatment liquid, the concentration of potassium nitrate is 5.5 wt %, the concentration of strontium nitrate is 1.3 wt % and the concentration of copper nitrate is 2.5 wt %.

[0085] 3) Load

[0086] The pretreated product was added to 4 times the volume of the loading liquid, heated to 50°C, kept at this temperature for 8 hours, filtered out, placed in a vacuum environment of 0.05 MPa, and dried at 75°C to constant weight to obtain a catalyst.

[0087] The loading liquid is prepared by adding triethylenediamine and tetrabutyl titanate into ethanol and stirring until completely dissolved. The weight ratio of triethylenediamine, tetrabutyl titanate, and ethanol is 2.5:1.2:100.

[0088] 3. Aggregation

[0089] After the transesterification step is completed, the vacuum degree in the reactor is adjusted to 0.02 MPa, the temperature is raised to 200° C., and the polymerization is carried out by heat preservation for 4 hours. The monomers and low molecular weight polycarbonate are then distilled off, and the solid matter is filtered out to obtain bio-based polycarbonate diol.

[0090] The bio-based polycarbonate diol prepared in this example has a number average molecular weight of 1878, a hydroxyl value of 59.7 mgKOH / g, an acid value of 0.011 mgKOH / g, a bio-based carbon content of 79.8 wt %, and a moisture content of 19 ppm.

[0091] Example 4

[0092] A method for preparing bio-based polycarbonate diol, specifically comprising:

[0093] 1. Prepare ingredients

[0094] The bio-based 1,4-butanediol was pumped into the 1,4-butanediol metering high-level tank by a feed pump; the diol was pumped into the diol metering high-level tank by a feed pump; the bio-based 1,4-butanediol and diol were respectively measured and introduced into the preparation kettle, kept warm and stirred at 35°C for 20 minutes to obtain the raw material liquid.

[0095] Among them, the diol is 1,5-pentanediol.

[0096] The molar ratio of bio-based 1,4-butanediol to 1,5-pentanediol is 4:1.

[0097] 2. Transesterification

[0098] The raw material liquid and dimethyl carbonate were introduced into a reactor filled with a catalyst. After the air in the reactor was completely replaced with nitrogen, the pressure in the reactor was adjusted to 8 kPa and stirred for 20 minutes. Then, the temperature was increased to 160°C at a heating rate of 2°C / min, and the mixture was kept at reflux for 8 hours. After that, the reflux was turned off and the azeotropic methanol and dimethyl carbonate were recovered by distillation to complete the ester exchange step.

[0099] The weight ratio of the raw material liquid, dimethyl carbonate and catalyst is 100:65:3.5.

[0100] The catalyst is prepared by the following method:

[0101] 1) Preprocessing

[0102] The hydroxyapatite was placed in a nitrogen atmosphere, heated to 250°C, kept warm for 40 minutes, and then naturally cooled to 60°C. The hydroxyapatite was added into 5 times the volume of the pretreatment liquid, and the temperature of the pretreatment liquid was adjusted to 65°C. The pretreatment liquid was kept warm for 2.5 hours and then filtered out. The pretreatment liquid was dried at 100°C for 2.5 hours, then heated to 380°C, kept warm and calcined for 3.5 hours, and granulated into 15 mesh to obtain a pretreated material.

[0103] The particle size of hydroxyapatite is 6 μm.

[0104] The pretreatment liquid is a deionized water solution containing potassium nitrate, strontium nitrate and copper nitrate. In the pretreatment liquid, the concentration of potassium nitrate is 5.5 wt %, the concentration of strontium nitrate is 1.2 wt % and the concentration of copper nitrate is 2.2 wt %.

[0105] 2) Load

[0106] The pretreated product was added to 3.5 times the volume of the loading liquid, heated to 45°C, kept still for 7 hours, filtered out, placed in a vacuum environment of 0.04 MPa, and dried at 75°C to constant weight to obtain a catalyst.

[0107] The loading liquid is prepared by adding triethylenediamine and tetrabutyl titanate into ethanol and stirring until completely dissolved. The weight ratio of triethylenediamine, tetrabutyl titanate, and ethanol is 2.5:1.3:100.

[0108] 3. Aggregation

[0109] After the transesterification step, the vacuum degree in the reactor was adjusted to 0.02 MPa, the temperature was raised to 210° C., and the polymerization was carried out by heat preservation for 4 hours. The monomers and low molecular weight polycarbonate were removed by distillation, and the solid matter was filtered out to obtain bio-based polycarbonate diol.

[0110] The bio-based polycarbonate diol prepared in this example has a number average molecular weight of 1860, a hydroxyl value of 60.3 mgKOH / g, an acid value of 0.011 mgKOH / g, a bio-based carbon content of 59.7 wt %, and a moisture content of 21 ppm.

[0111] Example 5

[0112] A method for preparing bio-based polycarbonate diol, specifically comprising:

[0113] 1. Prepare ingredients

[0114] The bio-based 1,4-butanediol was pumped into the 1,4-butanediol metering high-level tank by a feed pump; the diol was pumped into the diol metering high-level tank by a feed pump; the bio-based 1,4-butanediol and diol were respectively measured and introduced into the preparation kettle, kept warm and stirred for 30 minutes at 40°C to obtain the raw material liquid.

[0115] Among them, the diol is 1,6-hexanediol.

[0116] The molar ratio of bio-based 1,4-butanediol to 1,6-hexanediol is 4:1.

[0117] 2. Transesterification

[0118] The raw material liquid and dimethyl carbonate were introduced into a reactor filled with a catalyst. After the air in the reactor was completely replaced with nitrogen, the pressure in the reactor was adjusted to 10KPa and stirred for 30 minutes. Then, the temperature was increased to 170°C at a heating rate of 3°C / min. After the reaction was refluxed for 10 hours, the reflux was turned off and the azeotropic methanol and dimethyl carbonate were recovered by distillation to complete the ester exchange step.

[0119] The weight ratio of the raw material liquid, dimethyl carbonate and catalyst is 100:70:4.

[0120] The catalyst is prepared by the following method:

[0121] 1) Preprocessing

[0122] The hydroxyapatite was placed in a nitrogen atmosphere, heated to 300°C, kept warm for 60 minutes, and then naturally cooled to 65°C. The hydroxyapatite was added into 6 times the volume of the pretreatment liquid, and the temperature of the pretreatment liquid was adjusted to 70°C. After keeping warm for 3 hours, it was filtered out and dried at 105°C for 3 hours. The temperature was raised to 400°C, kept warm and calcined for 4 hours, and granulated into 20 mesh to obtain a pretreated material.

[0123] The particle size of hydroxyapatite is 8 μm.

[0124] The pretreatment liquid is a deionized water solution containing potassium nitrate, strontium nitrate and copper nitrate. In the pretreatment liquid, the concentration of potassium nitrate is 6 wt %, the concentration of strontium nitrate is 1.3 wt % and the concentration of copper nitrate is 2.5 wt %.

[0125] 2) Load

[0126] The pretreated product was added to 4 times the volume of the loading liquid, heated to 50°C, kept still for 8 hours, filtered out, placed in a vacuum environment of 0.05 MPa, kept dry at 80°C to constant weight, and the catalyst was prepared.

[0127] The loading liquid is prepared by adding triethylenediamine and tetrabutyl titanate into ethanol and stirring until completely dissolved. The weight ratio of triethylenediamine, tetrabutyl titanate, and ethanol is 3:1.5:100.

[0128] 3. Aggregation

[0129] After the transesterification step is completed, the vacuum degree in the reactor is adjusted to 0.03 MPa, the temperature is raised to 220° C., and the polymerization is carried out by heat preservation for 5 hours. The monomers and low molecular weight polycarbonate are then distilled off, and the solid matter is filtered out to obtain bio-based polycarbonate diol.

[0130] The bio-based polycarbonate diol prepared in this example has a number average molecular weight of 1913, a hydroxyl value of 58.7 mgKOH / g, an acid value of 0.012 mgKOH / g, a bio-based carbon content of 59.3 wt %, and a moisture content of 23 ppm.

[0131] Comparative Example 1

[0132] The technical solution of Example 2 was adopted, except that in the transesterification step, the pretreatment step was omitted during the preparation of the catalyst, and the hydroxyapatite was directly granulated into 15 mesh and then used directly in the loading step.

[0133] The bio-based polycarbonate diol prepared in this comparative example had a number average molecular weight of 2240, a hydroxyl value of 50.1 mgKOH / g, an acid value of 0.021 mgKOH / g, a bio-based carbon content of 53.5 wt %, and a moisture content of 32 ppm.

[0134] Comparative Example 2

[0135] The technical solution of Example 2 was adopted, with the following differences: 1) in the transesterification step, the addition of the catalyst was omitted, and instead a certain amount of potassium nitrate and strontium nitrate was added; the amount of potassium nitrate added was 200 ppm, and the amount of strontium nitrate added was 50 ppm. 2) in the polymerization step, a certain amount of tetrabutyl titanate was added; the amount of tetrabutyl titanate added was 100 ppm.

[0136] The bio-based polycarbonate diol prepared in this comparative example has a number average molecular weight of 2408, a hydroxyl value of 46.6 mgKOH / g, an acid value of 0.025 mgKOH / g, a bio-based carbon content of 55.2 wt %, and a moisture content of 36 ppm.

[0137] Polyurethane elastomers were prepared using the polycarbonate diols prepared in Examples 1-5 and Comparative Examples 1-2, respectively, and the physical properties and chemical corrosion resistance of each polyurethane elastomer were tested. Specifically, the polyurethane elastomers were prepared using the following method: the polycarbonate diols prepared in Examples 1-5 and Comparative Examples 1-2 were respectively added to a reactor, the vacuum degree in the reactor was adjusted to 0.06 MPa, the temperature was raised to 110°C, and the reactor was kept warm to remove water for 30 minutes; the temperature was then lowered to no more than 60°C, diphenylmethane-4,4'-diisocyanate and dibutyltin dilaurate were added, the temperature was raised to 80°C, the reaction was kept warm for 2 hours, the mixture was naturally cooled, and the mixture was allowed to stand for 24 hours; 1,4-butanediol was continuously added, the mixture was stirred evenly, the mixture was poured into a mold, the mixture was placed in a 110°C environment, the mixture was allowed to stand for 2 hours, the mixture was naturally cooled, the mold was removed, and the mixture was allowed to stand for 24 hours, thereby preparing the polyurethane elastomers corresponding to each Example and Comparative Example.

[0138] The weight ratio of bio-based polycarbonate diol, diphenylmethane-4,4'-diisocyanate, dibutyltin dilaurate and butanediol is 100:20:13:4.

[0139] The physical properties of each polyurethane elastomer were tested using an electronic universal testing machine (CMT4104, Meters Industrial Systems Co., Ltd.), following the specific testing methods outlined in GB / T1040. The prepared polyurethane elastomers were cut into standard 1cm x 10cm strips for testing. The samples were moved at a rate of 100 mm / min, and tensile strength and elongation at break were measured at room temperature. Furthermore, each polyurethane elastomer was placed at -20°C for 5 minutes, and then the stress at 100% elongation was measured to determine its low-temperature tensile properties.

[0140] Polyurethane elastomers are tested for chemical corrosion resistance, including resistance to oleic acid and ethanol. The oleic acid resistance test involves cutting the prepared polyurethane elastomer into 3cm*3cm squares, measuring the initial weight, and then immersing the squares in 10 times the volume of oleic acid. Under a nitrogen atmosphere, the squares are then incubated at 80°C for 24 hours, removed, and any excess liquid removed from the surface. The squares are then weighed after immersion and the rate of weight gain calculated.

[0141] The ethanol resistance test method is as follows: the prepared polyurethane elastomer is cut into 3cm*3cm pieces, the initial weight is weighed, and then it is immersed in 10 times the volume of anhydrous ethanol. Under the protection of a nitrogen atmosphere, it is allowed to stand at 25°C for 1 hour, then taken out, the excess liquid phase on the surface is removed, the weight after immersion is weighed, and the weight increase rate is calculated.

[0142] The test results of the physical properties and chemical corrosion resistance of the polyurethane elastomers corresponding to Examples 1-4 and Comparative Examples 1-2 are shown in the following table:

[0143]

[0144] It can be seen that the present invention adopts bio-based 1,4-butanediol as a raw material for the preparation of polycarbonate diol; a pretreated and loaded specific catalyst is provided in the ester exchange step; the bio-based polycarbonate diol obtained through the ester exchange and polymerization steps effectively solves the problem in the prior art that the catalyst is difficult to effectively separate after the polymerization reaction is completed, effectively avoids the adverse effects of catalyst residues on the application performance of the polycarbonate diol, and further improves the physical properties and chemical corrosion resistance of the obtained polyurethane elastomer; at the same time, the obtained polycarbonate diol has a stable hydroxyl value, a narrow molecular weight distribution, a high bio-based carbon content, and a good quality polycarbonate diol product, which utilizes the subsequent applications of the polycarbonate diol.

[0145] Unless otherwise specified, all percentages used in the present invention are by mass.

[0146] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing bio-based polycarbonate diol, characterized in that: The method consists of the following steps: material preparation, ester exchange, and polymerization; The raw material preparation comprises uniformly mixing bio-based 1,4-butanediol and diol to obtain a raw material liquid; or using bio-based 1,4-butanediol as the raw material liquid; In the prepared material, the molar ratio of bio-based 1,4-butanediol to diol is 3-4:1; the diol is 1,5-pentanediol or 1,6-hexanediol; The transesterification step comprises introducing the raw material liquid and carbonate into a reaction device filled with a catalyst, adjusting the pressure in the reactor to 5-10 kPa under nitrogen atmosphere, and stirring; then heating to 150-170° C., maintaining the temperature and reflux reaction for 4-10 hours, closing the reflux, and distilling to recover the azeotropic methanol and carbonate, thereby completing the transesterification step; In the transesterification, the carbonate is ethylene carbonate or dimethyl carbonate; The catalyst is prepared by the following steps: pretreatment and loading; The pretreatment comprises placing the hydroxyapatite in a nitrogen atmosphere, heating it to 200-300° C., keeping it warm for 30-60 minutes, and then naturally cooling it to 55-65° C.; adding it to a pretreatment solution of 3-6 times its volume, adjusting the temperature of the pretreatment solution to 60-70° C., keeping it warm for 2-3 hours, and then filtering it out; and drying, roasting, and granulating it to obtain a pretreated product. In the pretreatment, the pretreatment liquid is a deionized water solution containing potassium nitrate, strontium nitrate and copper nitrate, wherein the concentration of potassium nitrate in the pretreatment liquid is 5-6 wt %, the concentration of strontium nitrate is 1-1.3 wt %, and the concentration of copper nitrate is 2-2.5 wt %; The hydroxyapatite particle size is 5-8 μm; The loading is to put the pretreated material into 3-4 times the volume of the loading liquid, heat it to 40-50°C, keep it at this temperature and let it stand for 6-8 hours, then filter it out and dry it to obtain the catalyst; In the loading, the loading liquid is an ethanol solution in which triethylenediamine and tetrabutyl titanate are dissolved; After the polymerization and transesterification steps are completed, the vacuum degree in the reaction device is adjusted to 0.01-0.03 MPa, the temperature is raised to 200-220° C., and the polymerization is carried out by heat preservation for 3-5 hours. The monomers and low molecular weight polycarbonate are then distilled off, and the solid matter is filtered off to obtain bio-based polycarbonate diol.

2. The method for preparing bio-based polycarbonate diol according to claim 1, wherein: During the transesterification, the heating rate is 1-3°C / min; The weight ratio of the raw material liquid, the carbonate ester and the catalyst is 100:60-70:3-4.

3. The method for preparing bio-based polycarbonate diol according to claim 1, characterized in that: In the loading liquid, the weight ratio of triethylenediamine, tetrabutyl titanate and ethanol is 2-3:1-1.5:

100.

4. A bio-based polycarbonate diol, characterized in that The method is prepared according to any one of claims 1 to 3.

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