Biomass polyvinyl alcohol and preparation method thereof

Abstract

The invention discloses biomass polyvinyl alcohol and a preparation method thereof, and relates to the technical field of polyvinyl alcohol, the method comprises the following steps: adding initial biomass vinyl acetate into a rectifying tower for continuous rectification to obtain refined biomass vinyl acetate; the method comprises the following steps: adding refined biomass vinyl acetate, a methanol solution and an initiator into a polymerization kettle, stirring for reaction, transferring into a rectifying tower for rectification after the reaction is finished, obtaining a biomass polyvinyl acetate methanol solution from the kettle, uniformly mixing the biomass polyvinyl acetate methanol solution and an alkali methanol solution, performing alcoholysis reaction, crushing, extruding and drying, thereby obtaining the biomass polyvinyl acetate. Biomass polyvinyl alcohol is obtained; by using the biomass vinyl acetate as the raw material, the bio-based content in the polyvinyl alcohol can be increased, the biodegradability of the polyvinyl alcohol is further improved, and the polyvinyl alcohol has the advantages of sustainable development, low energy consumption, environmental protection and high quality, can meet the national requirements of ecological priority and green low-carbon development road, and expands the application field of the polyvinyl alcohol.

Description

Technical Field

[0001] The invention relates to the technical field of polyvinyl alcohol, and in particular to biomass polyvinyl alcohol and a preparation method thereof. Background Art

[0002] Bio-based polyvinyl alcohol (PVA) is produced by biochemical, physical and other methods using renewable resources, including crops, trees, other plants and their residues. Compared with traditional petrochemical polyvinyl alcohol, bio-based polyvinyl alcohol has the advantages of carbon emission reduction, sustainable raw material regeneration, green production, resource conservation, etc. According to the Organization for Economic Cooperation and Development, at least 20% (about US$800 billion) of petrochemical products can be replaced by bio-based products in the next decade, while the current replacement rate is less than 5%, leaving a huge market gap.

[0003] The existing production methods for polyvinyl alcohol include the carbide acetylene method, the petroleum ethylene method, the natural gas acetylene method, etc. The PVA produced by these methods has very little or even zero bio-based content, an activity between 10.5min-15.5min, many impurities, and low cleanliness, resulting in unstable and volatile reactions in the subsequent polymerization process, and the product quality cannot be guaranteed, resulting in poor biodegradability and being very unfriendly to the environment.

[0004] Based on this, the present invention is committed to providing a biomass polyvinyl alcohol and a preparation method thereof. Summary of the invention

[0005] The purpose of the present invention is to provide a biomass polyvinyl alcohol and a preparation method thereof, to solve the following technical problems:

[0006] How to improve the biodegradability of polyvinyl alcohol.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] In the first aspect, the present invention discloses a biomass polyvinyl alcohol, which uses biomass polyvinyl acetate as a production raw material. Biomass polyvinyl acetate is an existing commercially available raw material and has good degradability. Therefore, the biomass polyvinyl alcohol produced as a production raw material has excellent biodegradability.

[0009] In a second aspect, the present invention further discloses a method for preparing the biomass polyvinyl alcohol as described above, comprising the following steps:

[0010] S1, adding the initial biomass vinyl acetate into a distillation tower for continuous distillation to obtain refined biomass vinyl acetate;

[0011] S2, adding the refined biomass vinyl acetate, methanol solution and initiator into a polymerization kettle, stirring and reacting for 210-270 min under the conditions of pressure of 0-10 KPa and temperature of 65° C., transferring to a distillation tower for distillation after the reaction, and obtaining a biomass polyvinyl acetate methanol solution from the kettle;

[0012] S3. Evenly mix the biomass polyvinyl acetate methanol solution and the alkali methanol solution, perform alcoholysis reaction at 40-75° C., and then grind, extrude and dry to obtain biomass polyvinyl alcohol.

[0013] Furthermore, the specific operation steps of step S1 are: the initial biomass vinyl acetate is 10m 3 / h is added into the distillation tower, and the distillation is continued under the conditions of tower pressure of 0.013-0.03MPa, kettle temperature of 73-81°C, and top temperature of 64-72°C. The inhibitor solution is added at a flow rate of 100L / h to control the activity of biomass vinyl acetate to ≤570s, so as to obtain refined biomass vinyl acetate.

[0014] Furthermore, the preparation method of the polymerization inhibitor is: using the initial biomass vinyl acetate as a solvent and hydroquinone as a solute, and diluting and preparing a polymerization inhibitor solution with a mass concentration of 1%.

[0015] Furthermore, in step S2, the preparation method of the initiator solvent is: using methanol as solvent and azobisisobutyronitrile as solute, and diluting to prepare an initiator solution with a mass concentration of 0.9-1.1%.

[0016] Furthermore, the specific operation steps of step S2 are:

[0017] S21, when the temperature of the first polymerization kettle preheater rises to 59°C and the steam pressure of the first polymerization kettle lower jacket is 0.1-0.15MPa, the refined biomass vinyl acetate is heated at 5m 3 / h, methanol solution at 1.3m 3 / h, initiator solution at 0.1m 3 / h flow rate into the first polymerization kettle preheater, and then add it into the first polymerization kettle for stirring reaction, maintain the bottom temperature of the first polymerization kettle preheater at 59°C, adjust the steam volume of the lower jacket of the first polymerization kettle, and stop adding when the liquid level of the kettle reaches 52% of the liquid level. The reaction residence time is 1.5h;

[0018] S22, 30 minutes before the first polymerization kettle pump feeds the second polymerization kettle, open the second polymerization kettle jacket steam to heat up, when the polymerization rate of the first polymerization kettle reaction liquid reaches 20%, re-add to the first polymerization kettle, while maintaining the first polymerization kettle liquid level unchanged, send the reaction liquid in the first polymerization kettle to the second polymerization kettle for stirring reaction, adjust the second polymerization kettle jacket steam volume, when the second polymerization kettle liquid level reaches 52% liquid level, the polymerization rate reaches 58%, maintain the second polymerization kettle liquid level at 52%, while the second polymerization kettle pump feeds to the first distillation tower;

[0019] S23, sending the reaction liquid of the second polymerization kettle to a distillation tower for separation, with a tower pressure of 0.015-0.033 MPa, a kettle temperature of 66-74°C, a top temperature of 58-66°C, and obtaining a biomass polyvinyl acetate methanol solution out of the kettle.

[0020] Furthermore, in step S3, the preparation method of the alkali methanol is: using methanol as a solvent and solid alkali as a solute, and diluting to prepare an alkali methanol solution with a mass concentration of 55 g / L.

[0021] Furthermore, the solid alkali is sodium hydroxide.

[0022] Furthermore, in step S3, the alkali molar ratio of the biomass polyvinyl acetate methanol solution to the alkali methanol solution is 0.011-0.0145 g / L.

[0023] Furthermore, the specific operation steps of step S3 are:

[0024] S31, mixing the biomass polyvinyl acetate methanol solution and the alkali methanol solution, adding the mixture to a belt conveyor alcoholysis machine with a steam jacket, raising the temperature to 40-75° C., starting the belt conveyor alcoholysis machine, and reacting for 20-40 min to obtain white block solid biomass polyvinyl alcohol;

[0025] S32, adding white block solid biomass polyvinyl alcohol into a first pulverizer with a comb-type blade and a second pulverizer with a roller-type blade, and then adding the pulverizer into an extruder for squeezing to obtain crushed material;

[0026] S33, adding the crushed material into a dryer with a rotating stirring device, maintaining a slight vacuum state in the dryer, with the temperature of the front section being 55-85°C, the temperature of the middle front section being 70-90°C, the temperature of the middle rear section being 70-100°C, and the temperature of the rear section being 100-130°C, and obtaining biomass polyvinyl alcohol in the rear section of the dryer.

[0027] Beneficial effects of the present invention:

[0028] (1) The biomass polyvinyl alcohol of the present invention uses biomass vinyl acetate as a raw material, which can increase the biobased content in polyvinyl alcohol to more than 98%, thereby improving its biodegradability. It has sustainable development, low energy consumption, environmental protection, and high quality. It can meet the country's requirements for ecological priority and green and low-carbon development, and expand the application field of polyvinyl alcohol.

[0029] (2) In the preparation method of biomass polyvinyl alcohol of the present invention, biomass polyvinyl acetate is refined before use, so that refined biomass polyvinyl acetate with higher purity and better degradation performance can be obtained, thereby improving the activity of the prepared biomass polyvinyl alcohol, reducing the impurity content of the biomass polyvinyl alcohol product, and improving its cleanliness. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial channels.

[0032] Example 1

[0033] Preparation of biomass polyvinyl alcohol:

[0034] Step 1: Preparation of Refined Biomass Vinyl Acetate

[0035] (1) Using the initial biomass vinyl acetate (purchased from Guangxi Wanwei Biomass Technology Co., Ltd.) as a solvent and hydroquinone as a solute, a polymerization inhibitor solution with a mass concentration of 1% was prepared by dilution.

[0036] (2) The initial biomass vinyl acetate (purchased from Guangxi Wanwei Biomass Technology Co., Ltd.) was heated to 10 m 3 / h is added into the distillation tower, and distillation is continued under the conditions of tower pressure of 0.02MPa, kettle temperature of 78°C and top temperature of 68°C. In addition, an inhibitor solution is added at a flow rate of 100L / h to control the activity of biomass vinyl acetate to be ≤570s, thereby obtaining refined biomass vinyl acetate.

[0037] Step 2: Preparation of biomass polyvinyl acetate methanol solution

[0038] (1) Using methanol as solvent and azobisisobutyronitrile as solute, dilute and prepare an initiator solution with a mass concentration of 1%.

[0039] (2) When the temperature of the first polymerization kettle preheater rises to 59°C and the steam pressure of the first polymerization kettle lower jacket is 0.12MPa, the refined biomass vinyl acetate is heated at 5m 3 / h, methanol solution at 1.3m 3 / h, initiator solution at 0.1m 3 / h flow rate into the first polymerization kettle preheater, and then added into the first polymerization kettle for stirring reaction, maintaining the bottom temperature of the first polymerization kettle preheater at 59°C, adjusting the amount of steam in the lower jacket of the first polymerization kettle, and stopping the feeding when the liquid level in the kettle reaches 52% of the liquid level. The reaction residence time is 1.5h.

[0040] (3) 30 minutes before the first polymerization kettle pump feeds the second polymerization kettle, the steam in the jacket of the second polymerization kettle is turned on to increase the temperature. When the polymerization rate of the reaction liquid in the first polymerization kettle reaches 20%, the first polymerization kettle is re-added while the liquid level of the first polymerization kettle is maintained unchanged. The reaction liquid in the first polymerization kettle is fed to the second polymerization kettle for stirring and reaction. The amount of steam in the jacket of the second polymerization kettle is adjusted. When the liquid level of the second polymerization kettle reaches 52% and the polymerization rate reaches 58%, the liquid level of the second polymerization kettle is maintained at 52%. At the same time, the second polymerization kettle pump feeds the first distillation tower;

[0041] (4) The reaction liquid from the second polymerization kettle is sent to a distillation tower for separation. The tower pressure is 0.02 MPa, the kettle temperature is 70° C., and the top temperature is 62° C., and a biomass polyvinyl acetate methanol solution is obtained from the kettle.

[0042] Step 3: Preparation of biomass polyvinyl alcohol

[0043] (1) Using methanol as solvent and sodium hydroxide as solute, dilute and prepare an alkaline methanol solution with a mass concentration of 55 g / L.

[0044] (2) mixing the biomass polyvinyl acetate methanol solution and the alkali methanol solution at an alkali molar ratio of 0.013 g / L, and adding the mixture to a belt conveyor alcoholysis machine with a steam jacket, heating the mixture to 60° C., starting the belt conveyor alcoholysis machine, and reacting for 30 min to obtain a white block solid biomass polyvinyl alcohol;

[0045] (3) adding white block solid biomass polyvinyl alcohol into a first pulverizer with a comb-type blade, a second pulverizer with a roller-type blade, and then adding it into an extruder for squeezing to obtain crushed material;

[0046] (4) Add the crushed material into a dryer with a rotating stirring device, maintain a slight vacuum state in the dryer, set the temperature of the front section to 75°C, the temperature of the middle front section to 80°C, the temperature of the middle rear section to 85°C, and the temperature of the rear section to 120°C, and obtain biomass polyvinyl alcohol in the rear section of the dryer.

[0047] Example 2

[0048] Preparation of biomass polyvinyl alcohol:

[0049] Step 1: Preparation of Refined Biomass Vinyl Acetate

[0050] (1) Using the initial biomass vinyl acetate (purchased from Guangxi Wanwei Biomass Technology Co., Ltd.) as a solvent and hydroquinone as a solute, a polymerization inhibitor solution with a mass concentration of 1% was prepared by dilution.

[0051] (2) The initial biomass vinyl acetate (purchased from Guangxi Wanwei Biomass Technology Co., Ltd.) was heated to 10 m 3 / h is added into the distillation tower, and distillation is continued under the conditions of tower pressure of 0.013MPa, kettle temperature of 73°C and top temperature of 64°C. In addition, an inhibitor solution is added at a flow rate of 100L / h to control the activity of biomass vinyl acetate to be ≤570s, thereby obtaining refined biomass vinyl acetate.

[0052] Step 2: Preparation of biomass polyvinyl acetate methanol solution

[0053] (1) Using methanol as solvent and azobisisobutyronitrile as solute, dilute and prepare an initiator solution with a mass concentration of 0.9%.

[0054] (2) When the temperature of the first polymerization kettle preheater rises to 59°C and the steam pressure of the first polymerization kettle lower jacket is 0.12MPa, the refined biomass vinyl acetate is heated at 5m 3 / h, methanol solution at 1.3m 3 / h, initiator solution at 0.1m 3 / h flow rate into the first polymerization kettle preheater, and then added into the first polymerization kettle for stirring reaction, maintaining the bottom temperature of the first polymerization kettle preheater at 59°C, adjusting the amount of steam in the lower jacket of the first polymerization kettle, and stopping the feeding when the liquid level in the kettle reaches 52% of the liquid level. The reaction residence time is 1.5h.

[0055] (3) 30 minutes before the first polymerization kettle pump feeds the second polymerization kettle, the steam in the jacket of the second polymerization kettle is turned on to increase the temperature. When the polymerization rate of the reaction liquid in the first polymerization kettle reaches 20%, the first polymerization kettle is re-added while the liquid level of the first polymerization kettle is maintained unchanged. The reaction liquid in the first polymerization kettle is fed to the second polymerization kettle for stirring and reaction. The amount of steam in the jacket of the second polymerization kettle is adjusted. When the liquid level of the second polymerization kettle reaches 52% and the polymerization rate reaches 58%, the liquid level of the second polymerization kettle is maintained at 52%. At the same time, the second polymerization kettle pump feeds the first distillation tower;

[0056] (4) The reaction liquid from the second polymerization kettle was sent to a distillation tower for separation. The tower pressure was 0.015 MPa, the kettle temperature was 66° C., and the top temperature was 58° C., and a biomass polyvinyl acetate methanol solution was obtained from the kettle.

[0057] Step 3: Preparation of biomass polyvinyl alcohol

[0058] (1) Using methanol as solvent and sodium hydroxide as solute, dilute and prepare an alkaline methanol solution with a mass concentration of 55 g / L.

[0059] (2) mixing the biomass polyvinyl acetate methanol solution and the alkali methanol solution at an alkali molar ratio of 0.011 g / L, and adding the mixture to a belt conveyor alcoholysis machine with a steam jacket, heating the mixture to 75° C., starting the belt conveyor alcoholysis machine, and reacting for 40 min to obtain a white block solid biomass polyvinyl alcohol;

[0060] (3) adding white block solid biomass polyvinyl alcohol into a first pulverizer with a comb-type blade, a second pulverizer with a roller-type blade, and then adding it into an extruder for squeezing to obtain crushed material;

[0061] (4) Add the crushed material into a dryer with a rotating stirring device, maintain a slight vacuum state in the dryer, set the temperature of the front section to 55°C, the temperature of the middle front section to 70°C, the temperature of the middle rear section to 70°C, and the temperature of the rear section to 100°C, and obtain biomass polyvinyl alcohol in the rear section of the dryer.

[0062] Example 3

[0063] Preparation of biomass polyvinyl alcohol:

[0064] Step 1: Preparation of Refined Biomass Vinyl Acetate

[0065] (1) Using the initial biomass vinyl acetate (purchased from Guangxi Wanwei Biomass Technology Co., Ltd.) as a solvent and hydroquinone as a solute, a polymerization inhibitor solution with a mass concentration of 1% was prepared by dilution.

[0066] (2) The initial biomass vinyl acetate (purchased from Guangxi Wanwei Biomass Technology Co., Ltd.) was heated to 10 m 3 / h is added into the distillation tower, and distillation is continued under the conditions of tower pressure of 0.03MPa, kettle temperature of 81°C and top temperature of 72°C. In addition, an inhibitor solution is added at a flow rate of 100L / h to control the activity of biomass vinyl acetate to be ≤570s, thereby obtaining refined biomass vinyl acetate.

[0067] Step 2: Preparation of biomass polyvinyl acetate methanol solution

[0068] (1) Using methanol as solvent and azobisisobutyronitrile as solute, dilute and prepare an initiator solution with a mass concentration of 1.1%.

[0069] (2) When the temperature of the first polymerization kettle preheater rises to 59°C and the steam pressure of the first polymerization kettle lower jacket is 0.12MPa, the refined biomass vinyl acetate is heated at 5m 3 / h, methanol solution at 1.3m 3 / h, initiator solution at 0.1m 3 / h flow rate into the first polymerization kettle preheater, and then added into the first polymerization kettle for stirring reaction, maintaining the bottom temperature of the first polymerization kettle preheater at 59°C, adjusting the amount of steam in the lower jacket of the first polymerization kettle, and stopping the feeding when the liquid level in the kettle reaches 52% of the liquid level. The reaction residence time is 1.5h.

[0070] (3) 30 minutes before the first polymerization kettle pump feeds the second polymerization kettle, the steam in the jacket of the second polymerization kettle is turned on to increase the temperature. When the polymerization rate of the reaction liquid in the first polymerization kettle reaches 20%, the first polymerization kettle is re-added while the liquid level of the first polymerization kettle is maintained unchanged. The reaction liquid in the first polymerization kettle is fed to the second polymerization kettle for stirring and reaction. The amount of steam in the jacket of the second polymerization kettle is adjusted. When the liquid level of the second polymerization kettle reaches 52% and the polymerization rate reaches 58%, the liquid level of the second polymerization kettle is maintained at 52%. At the same time, the second polymerization kettle pump feeds the first distillation tower;

[0071] (4) The reaction liquid from the second polymerization kettle was sent to a distillation tower for separation. The tower pressure was 0.033 MPa, the kettle temperature was 74° C., and the top temperature was 66° C., and a biomass polyvinyl acetate methanol solution was obtained from the kettle.

[0072] Step 3: Preparation of biomass polyvinyl alcohol

[0073] (1) Using methanol as solvent and sodium hydroxide as solute, dilute and prepare an alkaline methanol solution with a mass concentration of 55 g / L.

[0074] (2) mixing the biomass polyvinyl acetate methanol solution and the alkali methanol solution at an alkali molar ratio of 0.0145 g / L, and adding the mixture to a belt conveyor alcoholysis machine with a steam jacket, heating the mixture to 40° C., starting the belt conveyor alcoholysis machine, and reacting for 20 min to obtain a white block solid biomass polyvinyl alcohol;

[0075] (3) adding white block solid biomass polyvinyl alcohol into a first pulverizer with a comb-type blade, a second pulverizer with a roller-type blade, and then adding it into an extruder for squeezing to obtain crushed material;

[0076] (4) Add the crushed material into a dryer with a rotating stirring device, maintain a slight vacuum state in the dryer, set the temperature of the front section to 85°C, the temperature of the middle front section to 90°C, the temperature of the middle rear section to 100°C, and the temperature of the rear section to 130°C, and obtain biomass polyvinyl alcohol in the rear section of the dryer.

[0077] Comparative Example 1

[0078] Preparation of biomass polyvinyl alcohol: Compared with Example 1, the only difference is that step one is cancelled, and the refined biomass vinyl acetate in step two is replaced by initial biomass vinyl acetate (purchased from Guangxi Wanwei Biomass Technology Co., Ltd.), and the other steps and conditions are exactly the same, and biomass polyvinyl alcohol is finally obtained.

[0079] Comparative Example 2

[0080] Preparation of polyvinyl alcohol: Compared with Example 1, the only difference is that step one is cancelled, and the refined biomass vinyl acetate in step two is replaced by conventional non-biomass vinyl acetate (purchased from Guangxi Wanwei Biomass Technology Co., Ltd.), and the other steps and conditions are exactly the same, and polyvinyl alcohol is finally obtained.

[0081] Comparative Example 3

[0082] Polyvinyl alcohol currently available on the market (purchased from Guangxi Wanwei Biomass Technology Co., Ltd.) was directly used as the polyvinyl alcohol in Comparative Example 3.

[0083] The performance of the polyvinyl alcohol of Examples 1-3 and Comparative Examples 1-3 was tested by the following method:

[0084] Appearance: Observation method;

[0085] Volatile matter: instrumental method, refer to the method specified in Appendix A of GB / T 12010.2;

[0086] Sodium acetate content: Chemical method, refer to the method specified in Appendix B of GB / T 12010.2;

[0087] Purity: reduction method, refer to the method specified in GB / T 12010.34.6;

[0088] Alcoholysis degree: chemical method, refer to the method specified in Appendix D of GB / T 12010.2;

[0089] Ash content: calculated based on the sodium acetate content, referring to the method specified in Appendix C of GB / T 12010.2;

[0090] pH value: instrumental method, refer to the method specified in GB / T 12010.4;

[0091] Viscosity: Instrumental method, refer to the method specified in Appendix E of GB / T 12010.2. During arbitration, Brookfield viscometer is used;

[0092] Coloration degree: chemical method, instrumental method;

[0093] Transparency: Instrumental method, refer to the method specified in GB / T 12010.8;

[0094] Swelling degree: instrumental method.

[0095] The test results are listed in Table 1. Table 1 is as follows:

[0096] Table 1

[0097]

[0098] By analyzing the data in Table 1, it can be found that compared with comparative examples 1-3, the biomass polyvinyl alcohol prepared in Examples 1-3 has better performance in all aspects tested, among which the coloring and transparency are significantly higher, indicating that the gloss will be better after film formation, and the viscosity and swelling are significantly higher, indicating that it has more stable mechanical stability and sustainability, which can meet the country's requirements for ecological priority, green and low-carbon development, and expand the application field of polyvinyl alcohol.

[0099] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A biomass polyvinyl alcohol, characterized in that: Biomass polyvinyl acetate is used as the production raw material.

2. A method for preparing biomass polyvinyl alcohol according to claim 1, characterized in that: The steps include: S1, adding the initial biomass vinyl acetate into a distillation tower for continuous distillation to obtain refined biomass vinyl acetate; S2, adding the refined biomass vinyl acetate, methanol solution and initiator into a polymerization kettle, stirring and reacting for 210-270 min under the conditions of pressure of 0-10 KPa and temperature of 65° C., transferring to a distillation tower for distillation after the reaction, and obtaining a biomass polyvinyl acetate methanol solution from the kettle; S3. After the biomass polyvinyl acetate methanol solution and the alkali methanol solution are uniformly mixed, alcoholysis reaction is carried out at 40-75° C., and then the mixture is crushed, extruded and dried to obtain biomass polyvinyl alcohol.

3. The method for preparing biomass polyvinyl alcohol according to claim 2, characterized in that: The specific operation steps of step S1 are: 3 / h is added into the distillation tower, and the distillation is continued under the conditions of tower pressure of 0.013-0.03MPa, kettle temperature of 73-81°C, and top temperature of 64-72°C. The inhibitor solution is added at a flow rate of 100L / h to control the activity of biomass vinyl acetate to ≤570s, so as to obtain refined biomass vinyl acetate.

4. The method for preparing biomass polyvinyl alcohol according to claim 3, characterized in that: The preparation method of the polymerization inhibitor is as follows: using initial biomass vinyl acetate as solvent and hydroquinone as solute, and diluting and preparing a polymerization inhibitor solution with a mass concentration of 1%.

5. The method for preparing biomass polyvinyl alcohol according to claim 2, characterized in that: In step S2, the initiator solvent is prepared by using methanol as solvent and azobisisobutyronitrile as solute, and diluting the solvent to prepare an initiator solution with a mass concentration of 0.9-1.1%.

6. The method for preparing biomass polyvinyl alcohol according to claim 2, characterized in that: The specific operation steps of step S2 are: S21, when the temperature of the first polymerization kettle preheater rises to 59°C and the steam pressure of the first polymerization kettle lower jacket is 0.1-0.15MPa, the refined biomass vinyl acetate is heated at 5m 3 / h, methanol solution at 1.3m 3 / h, initiator solution at 0.1m 3 / h flow rate into the first polymerization kettle preheater, and then add it into the first polymerization kettle for stirring reaction, maintain the bottom temperature of the first polymerization kettle preheater at 59°C, adjust the steam volume of the lower jacket of the first polymerization kettle, and stop adding when the liquid level of the kettle reaches 52% of the liquid level. The reaction residence time is 1.5h; S22, 30 minutes before the first polymerization kettle pump feeds the second polymerization kettle, open the second polymerization kettle jacket steam to heat up, when the polymerization rate of the first polymerization kettle reaction liquid reaches 20%, re-add to the first polymerization kettle, while maintaining the first polymerization kettle liquid level unchanged, send the reaction liquid in the first polymerization kettle to the second polymerization kettle for stirring reaction, adjust the second polymerization kettle jacket steam volume, when the second polymerization kettle liquid level reaches 52% liquid level, the polymerization rate reaches 58%, maintain the second polymerization kettle liquid level at 52%, while the second polymerization kettle pump feeds to the first distillation tower; S23, sending the reaction liquid of the second polymerization kettle to a distillation tower for separation, with a tower pressure of 0.015-0.033 MPa, a kettle temperature of 66-74°C, a top temperature of 58-66°C, and obtaining a biomass polyvinyl acetate methanol solution out of the kettle.

7. The method for preparing biomass polyvinyl alcohol according to claim 2, characterized in that: In step S3, the preparation method of the alkali methanol is: using methanol as a solvent and solid alkali as a solute, diluting and preparing an alkali methanol solution with a mass concentration of 55 g / L.

8. The method for preparing biomass polyvinyl alcohol according to claim 7, characterized in that: The solid alkali is sodium hydroxide.

9. The method for preparing biomass polyvinyl alcohol according to claim 2, characterized in that: In step S3, the alkali molar ratio of the biomass polyvinyl acetate methanol solution to the alkali methanol solution is 0.011-0.0145 g / L.

10. The method for preparing biomass polyvinyl alcohol according to claim 2, characterized in that: The specific operation steps of step S3 are: S31, mixing the biomass polyvinyl acetate methanol solution and the alkali methanol solution, adding the mixture to a belt conveyor alcoholysis machine with a steam jacket, raising the temperature to 40-75° C., starting the belt conveyor alcoholysis machine, and reacting for 20-40 min to obtain white block solid biomass polyvinyl alcohol; S32, adding white block solid biomass polyvinyl alcohol into a first pulverizer with a comb-type blade and a second pulverizer with a roller-type blade, and then adding the pulverizer into an extruder for squeezing to obtain crushed material; S33, adding the crushed material into a dryer with a rotating stirring device, maintaining a slight vacuum state in the dryer, with the temperature of the front section being 55-85°C, the temperature of the middle front section being 70-90°C, the temperature of the middle rear section being 70-100°C, and the temperature of the rear section being 100-130°C, and obtaining biomass polyvinyl alcohol in the rear section of the dryer.

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