Polyvinyl alcohol with excellent anti-gel properties

Abstract

The invention belongs to the technical field of polyvinyl alcohol, and specifically relates to a polyvinyl alcohol with excellent anti-gelling property. The content of free acetate ions in the polyvinyl alcohol is less than 0.07% by mass. The polyvinyl alcohol of the invention has excellent anti-gelling property.

Description

Technical Field

[0001] The invention belongs to the technical field of polyvinyl alcohol, and in particular relates to polyvinyl alcohol with excellent anti-gelling property. Background Art

[0002] Polyvinyl alcohol is referred to as PVA, and its molecular formula is (CH 2 CHOH)n, with a flocculent, powdery or flaky appearance, is obtained by alcoholysis of polyvinyl acetate, has a planar zigzag conformation, a regular chemical structure, strong polarity, high crystallinity, chemical stability, high barrier properties, oil resistance, film-forming properties, solvent resistance and unique bonding properties ("Production and Market Status and Development Suggestions of Polyvinyl Alcohol in my country", Zhang Zhanhong, Weilun Newsletter, Vol. 36, No. 4, 2016, p. 1, left column, paragraph 1, lines 1-5, published on December 31, 2016; "Study on Plasticization Modification of Polyvinyl Alcohol", Ma Cong, Master's Thesis of Donghua University, 2017, p. 1, paragraph 1, line 1 to paragraph 2, line 1, published on December 31, 2017).

[0003] However, the existing polyvinyl alcohol has poor anti-gel performance. When the mass concentration of its aqueous solution is greater than 8%, it will produce gel and become jelly-like after being left for 24 hours. Summary of the invention

[0004] In view of this, an object of the present invention is to provide a polyvinyl alcohol.

[0005] The object of the present invention is to provide a polyvinyl alcohol, wherein the content of free acetate ions in the polyvinyl alcohol is less than 0.07% by mass.

[0006] The present invention also aims to protect a production method of polyvinyl alcohol, which includes polymerization, alcoholysis and washing steps, wherein the washing liquid in the washing step is ethanol with a purity of ≥99.9%.

[0007] Preferably, the washing liquid is anhydrous ethanol.

[0008] The present invention also aims at protecting a method for purifying polyvinyl alcohol, which uses ethanol with a purity of ≥99.9% for washing.

[0009] Furthermore, the alcohol is anhydrous ethanol.

[0010] The beneficial effects of the present invention are:

[0011] The polyvinyl alcohol of the present invention is excellent in anti-gelling property.

[0012] The production method of the invention is simple, convenient and easy to produce. DETAILED DESCRIPTION

[0013] The examples are provided to better illustrate the content of the present invention, but the content of the present invention is not limited to the examples. Therefore, those skilled in the art can make non-essential improvements and adjustments to the implementation scheme according to the above content of the invention, which still fall within the protection scope of the present invention.

[0014] In the present invention, the method for detecting the free acetate ion content is: the sample is divided into two parts, and one part of the sample (m 1 ) is placed in a crucible (m 2 ) and then slowly heated on an electric furnace until the sample is completely carbonized or volatilized. 3 );

[0015] Take another sample (m 4 ) was extracted with a Soxhlet extractor for 48 hours, dried at 105°C for 2 hours, allowed to cool to room temperature in a desiccator, and then placed in a crucible (m 5 ) and then slowly heated on an electric furnace until the sample is completely carbonized or volatilized, and weighed (m 6 );

[0016] Then according to the formula Calculate the free acetate ion content;

[0017] Among them, m 3 and m 6 is the mass of the crucible and the heated sample, in g; m 2 and m 5 is the mass of the constant weight crucible, in g; m 1 and m 4 is the mass of the sample in g.

[0018] In the present invention, the anti-gelling property detection method is as follows: 150 ml of a 10% polyvinyl alcohol aqueous solution is prepared and placed in a 250 ml conical flask, which is sealed and stored at room temperature for 24 hours, and then poured out from the conical flask. If the solution is in a jelly-like state, it cannot be poured out; if it is not in a jelly-like state, it can be poured out smoothly.

[0019] Example 1

[0020] Polyvinyl alcohol is prepared by using the following raw materials according to the following steps:

[0021] Add vinyl acetate, acrylic acid, pentaerythritol triallyl ether and methanol in a mass ratio of 74.5:3:0.5:22 into a three-necked glass flask, and then add tert-butyl peroxydecanoate in an initiator in a mass ratio of 0.02% of vinyl acetate, and react at 60° C. for 5 hours to obtain a vinyl acetate copolymer;

[0022] The polymer solution was distilled and purified at 75°C to obtain a vinyl acetate copolymer with a purity of 99.0%;

[0023] A copolymer of vinyl acetate with a purity of 99.0% is prepared into a methanol solution with a mass concentration of 22.0%, and mixed with a sodium methoxide-methanol solution with a mass concentration of 30%, the mixing ratio being a molar ratio of the vinyl acetate copolymer to the sodium methoxide of 20:100, followed by alcoholysis at 40°C for 0.6 hours;

[0024] After the alcoholysis reaction, the solid and liquid phases are completely separated, and the product is formed and hard. The formed block of polyvinyl alcohol product is cut into small cubes and put into a grinder for crushing. Finally, the crushed powder product is washed several times with anhydrous ethanol solution. The washing liquid does not contain solid crushed matter and can clean the metal particles in the non-polymerized part. The washed material is vacuum dried at 85°C for 6 hours to obtain white powder particles.

[0025] Example 2

[0026] The difference between this embodiment and embodiment 1 is that the comonomer used is methacrylic acid.

[0027] Example 3

[0028] The difference between this embodiment and embodiment 1 is that the comonomer used is itaconic acid.

[0029] Example 4

[0030] The difference between this embodiment and embodiment 1 is that the comonomer used is crotonic acid.

[0031] Example 5

[0032] The difference between this embodiment and embodiment 1 is that the comonomer used is maleic acid.

[0033] Example 6

[0034] The difference between this embodiment and embodiment 1 is that the comonomer used is N,N-methylenebisacrylamide.

[0035] Comparative Example 1

[0036] The difference between this comparative example and Example 1 is that the powdered product after crushing is washed with a methanol solution, the surface of the product after washing becomes sticky and partially dissolves in the methanol solution, and the product quality loses more than 30%.

[0037] Table 1 Performance test results

[0038] source Free sodium acetate / % Gel resistance test Example 1 0.02 Smooth pouring Example 2 0.05 Smooth pouring Example 3 0.03 Smooth pouring Example 4 0.04 Smooth pouring Example 5 0.02 Smooth pouring Example 6 0.03 Smooth pouring Comparative Example 1 0.7 Jelly-like and cannot be poured out

[0039] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for improving the anti-gelling property of polyvinyl alcohol in the production of polyvinyl alcohol, characterized in that: The steps include polymerization, alcoholysis and washing processes, wherein the raw monomers used in the polymerization process are vinyl acetate, acrylic acid and pentaerythritol triallyl ether; wherein the washing liquid in the washing process is ethanol with a purity of ≥99.9%; and the content of free acetate ions in the polyvinyl alcohol product prepared by the method is less than 0.07%, calculated in mass percentage.