Polyvinyl alcohol and a method for producing the same

Abstract

The application provides polyvinyl alcohol and a preparation method thereof, and the polyvinyl alcohol is prepared by taking 2-acrylamide-2-methylpropanesulfonic acid and dodecyl vinyl ether as a reaction type compound emulsifier. The polyvinyl alcohol can introduce hydrophilic sulfonic acid groups and soft segment long chain alkyl ether chains into a polyvinyl alcohol molecular chain, and can improve the flexibility and hydrolysis resistance of the polyvinyl alcohol on the basis of keeping the hydrophilicity, barrier property, biocompatibility and biodegradability of the polyvinyl alcohol.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of high polymer materials, and particularly relates to a polyvinyl alcohol and a preparation method thereof. BACKGROUND

[0002] Polyvinyl alcohol (PVA) is a kind of water-soluble functional high polymer material, which has strong film-forming property. The film formed by PVA has the characteristics of transparency, good mechanical property and strong gas barrier ability. PVA has excellent biocompatibility and biodegradability, and can be degraded into CO2 and H2O under the action of microorganisms. Therefore, PVA is widely used in various fields such as daily necessities, papermaking, textile, coating, battery, electronic components, biological medicine and the like.

[0003] However, PVA has poor water resistance. This is because PVA polymer contains a large number of hydrophilic hydroxyl groups in the side chain, which is easy to form intramolecular and intermolecular hydrogen bonds. In addition, PVA is easy to strongly exhibit the hydrophilic effect on water in the dry and wet changes of external environment, which destroys the intramolecular and intermolecular hydrogen bonds of PVA, leading to PVA swelling and then losing the excellent performance in mechanical property, barrier property and the like, greatly limiting the further popularization and application of PVA.

[0004] At present, the improvement of PVA water resistance is mainly to modify the PVA polymer to improve its water resistance, including physical modification and chemical modification. Physical modification is mainly through the formation of hydrogen bond, coordination bond between PVA side chain hydroxyl and modifier, such as adding tin tetrachloride to modify the commercially available polyvinyl alcohol in patent CN201510816800.5, using the strong coordination ability of tin ion to form complex with the side chain hydroxyl of PVA, which can exist stably in aqueous solution after film forming, and then significantly improve the water resistance of polyvinyl alcohol film; in patent CN2018103209445, polyvinyl alcohol is simply physically blended with chitosan or silicon dioxide, and a composite modified film is prepared by forming hydrogen bond between the side chain hydroxyl of PVA and chitosan or silicon dioxide, so as to improve the water resistance. Chemical modification is mainly through the reaction between PVA side chain hydroxyl and modifier to form stable chemical bond, such as patent 201610289989.1, which partially oxidizes part of the hydroxyl groups in polyvinyl alcohol to generate aldehyde groups with chemical activity, and then performs hydroxymethyl-like reaction with amide substances under alkaline conditions to generate hydroxymethyl-like derivatives, which perform condensation reaction at 80-100℃ during film coating process to form partial self-crosslinking film, thereby significantly improving the water resistance and oxygen barrier property of PVA film; patent 201510296306.0 makes the carboxyl of maleic anhydride esterify with the side chain hydroxyl of PVA to obtain maleic anhydride grafted PVA, and then reacts with sodium silicate solution under the catalysis of concentrated sulfuric acid to obtain inorganic silicon-maleic anhydride grafted polyvinyl alcohol material. The inorganic silicon-maleic anhydride grafted polyvinyl alcohol material has good water resistance after film forming without heat treatment, and no obvious swelling phenomenon is found after soaking the film material in boiling water bath for 4h, and the film surface is not broken.

[0005] However, the existing physical modification and chemical modification of PVA polymer all need to prepare PVA solution first, and the PVA polymer is easy to swell during the preparation of solution by dispersing in solvent, resulting in unsatisfactory modification effect; the physical modification has the defect of insufficient durability of modification effect, in addition, high temperature, long time and high content of modifier in the chemical modification process are easy to cause gel, and low temperature, short time and insufficient content of modifier are easy to cause unsatisfactory modification effect. SUMMARY

[0006] In order to overcome the problems existing in the prior art, the purpose of the present application is to provide a kind of polyvinyl alcohol and the preparation method of polyvinyl alcohol, which is prepared by using 2-acrylamide-2-methylpropane sulfonic acid and dodecyl vinyl ether as reaction type compound emulsifier, can introduce hydrophilic sulfonic acid group and soft segment long chain alkyl ether chain into polyvinyl alcohol molecular chain, improve its flexibility and hydrolysis resistance on the basis of keeping the hydrophilicity, barrier property, biocompatibility and biodegradability of polyvinyl alcohol.

[0007] The purpose of the present application is achieved by the following technical solutions.

[0008] A polyvinyl alcohol, raw materials of which include, vinyl acetate 20-60 parts, 2-acrylamide-2-methylpropane sulfonic acid 0.5-1.5 parts, dodecyl vinyl ether 0.5-1.5 parts, oxidizing agent 0.05-0.1 parts, reducing agent 0.03-0.15 parts, sodium chloride 0.01-0.5 parts, deionized water 100-300 parts.

[0009] Preferably, the molar ratio of 2-acrylamide-2-methylpropane sulfonic acid and dodecyl vinyl ether is 1-2:1.

[0010] Preferably, the molar ratio of 2-acrylamide-2-methylpropane sulfonic acid and dodecyl vinyl ether is 1:1.

[0011] Preferably, a polyvinyl alcohol, raw materials of which include, vinyl acetate 40-50 parts, 2-acrylamide-2-methylpropane sulfonic acid 0.8-1.2 parts, dodecyl vinyl ether 0.8-1.2 parts, oxidizing agent 0.08-0.1 parts, reducing agent 0.06-0.13 parts, sodium chloride 0.01-0.3 parts, deionized water 150-250 parts.

[0012] Preferably, a polyvinyl alcohol, raw materials of which include, vinyl acetate 50 parts, 2-acrylamide-2-methylpropane sulfonic acid 1 part, dodecyl vinyl ether 1 part, oxidizing agent 0.08 part, reducing agent 0.12 part, sodium chloride 0.09 part, deionized water 200 parts.

[0013] Preferably, the oxidizing agent is one or more of potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide.

[0014] Preferably, the reducing agent is one or more of sodium bisulfite, ferrous chloride, tartaric acid, mercaptan, VC.

[0015] A polyvinyl alcohol preparation method, comprising the following reaction steps:

[0016] Step one, vinyl acetate, 2-acrylamide-2-methylpropane sulfonic acid, dodecyl vinyl ether, reducing agent, sodium chloride and deionized water are added to the reaction equipment, stirred at room temperature, and nitrogen is passed to prepare solution A;

[0017] Step two, the temperature is raised to 35℃, the oxidizing agent is added dropwise, and the reaction is completed in 2h, and then the temperature is lowered to room temperature, and the reaction is completed to obtain the polymerization product B;

[0018] Step three, freezing for 5-12h at-10℃--5℃, thawing for 2-5h at room temperature, filtering, drying at 75℃-85℃, to obtain 2-acrylamide-2-methylpropanesulfonic acid / dodecyl vinyl ether / vinyl acetate resin.

[0019] Step four, dissolving the 2-acrylamide-2-methylpropanesulfonic acid / dodecyl vinyl ether / vinyl acetate resin obtained in step three in methanol to obtain a solution with a mass fraction of 10%-16%, adding sodium hydroxide methanol solution (solution mass fraction 30%) for alcoholysis, to obtain the target polyvinyl alcohol resin.

[0020] Preferably, the molar ratio of 2-acrylamide-2-methylpropanesulfonic acid / dodecyl vinyl ether / vinyl acetate resin and sodium hydroxide is 1:0.015-0.025.

[0021] Preferably, the molar ratio of 2-acrylamide-2-methylpropanesulfonic acid / dodecyl vinyl ether / vinyl acetate resin and sodium hydroxide is 1:0.02.

[0022] Beneficial effects:

[0023] 1. The polyvinyl alcohol resin of the present application is prepared by emulsion polymerization, and uses the reactive emulsifier 2-acrylamide-2-methylpropanesulfonic acid and dodecyl vinyl ether as a compounded emulsifier, which can not only exert the excellent emulsifying effect of the compounded emulsifier, but also introduce functional groups into the polyvinyl alcohol resin molecular chain through copolymerization to improve the performance of the polyvinyl alcohol.

[0024] 2. The polyvinyl alcohol resin of the present application is prepared by using 2-acrylamide-2-methylpropanesulfonic acid and dodecyl vinyl ether as a reactive compounded emulsifier to prepare polyvinyl alcohol, and through copolymerization to obtain 2-acrylamide-2-methylpropanesulfonic acid / dodecyl vinyl ether / polyvinyl alcohol resin, which can introduce hydrophilic sulfonic acid groups and soft segment long chain alkyl ether chains into the polyvinyl alcohol molecular chain, thereby improving the flexibility and hydrolysis resistance of the polyvinyl alcohol while maintaining its hydrophilicity, barrier property, biocompatibility and biodegradability. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be described below in conjunction with the embodiments, obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0026] The present application will be further explained and described below in conjunction with specific embodiments.

[0027] Example 1

[0028] A polyvinyl alcohol, the preparation method comprising the following reaction steps:

[0029] Step one, 50 parts of vinyl acetate, 1 part of 2-acrylamide-2-methylpropane sulfonic acid, 1 part of dodecyl vinyl ether, 0.12 parts of reducing agent VC, 0.09 parts of sodium chloride and 200 parts of deionized water are added into the reaction equipment, stirred at room temperature, and nitrogen is passed to prepare solution A;

[0030] Step two, the temperature is raised to 35°C, and the oxidizing agent potassium persulfate (0.08 parts of potassium persulfate is added to water to prepare a 30% mass fraction potassium persulfate aqueous solution) is added dropwise, and the dropping is completed within 2h, and the reaction is continued for 0.5-1h, then the temperature is lowered to room temperature, the reaction is ended, and the polymerization product B is obtained;

[0031] Step three, freezing at -10°C to -5°C for 10h, thawing at room temperature for 5h, filtering, and drying at 80°C to obtain a 2-acrylamide-2-methylpropane sulfonic acid / dodecyl vinyl ether / vinyl acetate resin.

[0032] Step four, the 2-acrylamide-2-methylpropane sulfonic acid / dodecyl vinyl ether / vinyl acetate resin obtained in step three is dissolved in methanol to obtain a 15% mass fraction solution, and sodium hydroxide methanol solution (30% mass fraction solution) is added for alcoholysis to obtain the target polyvinyl alcohol resin. The molar ratio of 2-acrylamide-2-methylpropane sulfonic acid / dodecyl vinyl ether / vinyl acetate resin and sodium hydroxide is 1:0.02.

[0033] Comparative Example 1

[0034] A polyvinyl alcohol, the preparation method comprising the following reaction steps:

[0035] Step one, 50 parts of vinyl acetate, 1 part of 2-acrylamide-2-methylpropane sulfonic acid, 1 part of Tween 20, 0.12 parts of reducing agent VC, 0.09 parts of sodium chloride and 200 parts of deionized water are added into the reaction equipment, stirred at room temperature, and nitrogen is passed to prepare solution A;

[0036] Step two, the temperature is raised to 35°C, and the oxidizing agent potassium persulfate (0.08 parts of potassium persulfate is added to water to prepare a 30% mass fraction potassium persulfate aqueous solution) is added dropwise, and the dropping is completed within 2h, and the reaction is continued for 0.5-1h, then the temperature is lowered to room temperature, the reaction is ended, and the polymerization product B is obtained;

[0037] Step three, freezing at -10°C to -5°C for 10h, thawing at room temperature for 5h, filtering, and drying at 80°C to obtain a 2-acrylamide-2-methylpropane sulfonic acid / dodecyl vinyl ether / vinyl acetate resin.

[0038] Step four, the 2-acrylamide-2-methylpropanesulfonic acid / vinyl acetate resin obtained in step three is dissolved in methanol to obtain a solution with a mass fraction of 15%, and sodium hydroxide methanol solution (solution mass fraction 30%) is added for alcoholysis to obtain the target polyvinyl alcohol resin. The molar ratio of 2-acrylamide-2-methylpropanesulfonic acid / vinyl acetate resin to sodium hydroxide is 1:0.02.

[0039] Comparative Example 2

[0040] A polyvinyl alcohol, the preparation method thereof comprising the following reaction steps:

[0041] Step one, 50 parts of vinyl acetate, 1 part of sodium dodecyl sulfonate, 1 part of dodecyl vinyl ether, 0.12 parts of reducing agent VC, 0.09 parts of sodium chloride, and 200 parts of deionized water are added to a reaction device, stirred at room temperature, and purged with nitrogen to prepare solution A;

[0042] Step two, the temperature is raised to 35°C, and the oxidizing agent potassium persulfate (0.08 parts of potassium persulfate is added to water to prepare a 30% mass fraction potassium persulfate aqueous solution) is added dropwise, and the reaction is completed in 2 hours. Continue to react for 0.5-1h, reduce to room temperature, end the reaction, and obtain polymerization product B;

[0043] Step three, freeze at -10°C to -5°C for 10h, thaw at room temperature for 5h, filter, and dry at 80°C to obtain dodecyl vinyl ether / vinyl acetate resin.

[0044] Step four, the dodecyl vinyl ether / vinyl acetate resin obtained in step three is dissolved in methanol to obtain a solution with a mass fraction of 15%, and sodium hydroxide methanol solution (solution mass fraction 30%) is added for alcoholysis to obtain the target polyvinyl alcohol resin. The molar ratio of dodecyl vinyl ether / vinyl acetate resin to sodium hydroxide is 1:0.02.

[0045] Comparative Example 3

[0046] A polyvinyl alcohol, the preparation method thereof comprising the following reaction steps:

[0047] Step one, 50 parts of vinyl acetate, 1 part of sodium dodecyl sulfonate, 1 part of Tween 20, 0.12 parts of reducing agent VC, 0.09 parts of sodium chloride, and 200 parts of deionized water are added to a reaction device, stirred at room temperature, and purged with nitrogen to prepare solution A;

[0048] Step two, temperature is raised to 35℃, drop by drop, add oxidant potassium persulfate (0.08 parts of potassium persulfate is added to water to prepare a 30% potassium persulfate aqueous solution), drop in 2h, continue to react for 0.5-1h, reduce to room temperature, end the reaction, to obtain the polymerization product B;

[0049] Step three, freeze at -10℃ to -5℃ for 10h, thaw at room temperature for 5h, filter, dry at 80℃, to obtain the vinyl acetate resin.

[0050] Step four, dissolve the vinyl acetate resin obtained in step three in methanol to obtain a 15% solution, add sodium hydroxide methanol solution (30% solution) for alcoholysis, to obtain the target polyvinyl alcohol resin. The molar ratio of the vinyl acetate resin and sodium hydroxide is 1:0.02.

[0051] Performance test

[0052] Take 100 parts of water, 15 parts of polyvinyl alcohol resin prepared in the example or the comparative example, raise the temperature to 90℃, stir and dissolve for 1h, then reduce the temperature to 80℃, continue to stir for 3h, after static defoaming, flow into a film. Measure the water temperature resistance, swelling rate, tensile strength of the coating film, as shown in the following table.

[0053] The test method of water temperature resistance: cut the film formed by flow into multiple samples, put into deionized water for water swelling, heat and raise the temperature, when the water temperature reaches 90℃, start stirring, stir for 10 seconds, static for 60 seconds, dry and weigh, the temperature is lowered by 5℃ for each sample, until the mass of the film is unchanged, record the water temperature at this time.

[0054] The test method of swelling rate: cut the film formed by flow, dry at 80℃ until the mass is unchanged, after drying, put into distilled water at room temperature for 24h, then take the film and quickly dry the water on the surface of the film sample with water absorption paper, weigh. Through the formula S=(m-m0) / m0 100% calculated swelling rate, wherein: S is the swelling rate (%); m is the swelling mass after soaking (g); m0 is the initial mass of the dried film (g). Take the average value of 5 groups of parallel samples for each sample.

[0055] The test method of tensile strength and elongation at break: according to the national standard GB / T 1040.3-2006, test the tensile strength and elongation at break of polyvinyl alcohol film.

[0056] Table 1 Performance of polyvinyl alcohol film

[0057]

[0058] From the comparison of the example 1 and the comparative example 1, the comparative example 2 and the comparative example 3, it can be seen that the polyamide resin curing agent polyvinyl alcohol prepared in the example 1 of the present application has significantly higher water resistance temperature, higher swelling rate, higher tensile strength and elongation at break, which is due to the preparation by the emulsion polymerization method and the use of the reactive emulsifier 2-acrylamide-2-methylpropane sulfonic acid and dodecyl vinyl ether as the compounded emulsifier, which can not only play the excellent emulsifying effect of the compounded emulsifier, but also can obtain 2-acrylamide-2-methylpropane sulfonic acid / dodecyl vinyl ether / polyvinyl alcohol resin by copolymerization, introduce the hydrophilic sulfonic acid group and the soft segment long chain alkyl ether chain into the polyvinyl alcohol molecular chain, the hydrophilic sulfonic acid group can keep the hydrophilicity of the polyvinyl alcohol, and has the hydrolysis resistance and high temperature resistance improvement effect at the same time, the ether bond in the soft segment long chain alkyl ether chain has the hydrophilicity, and the soft segment long chain alkyl can improve the flexibility and hydrolysis resistance of the polyvinyl alcohol. The comparative example 1 only introduces the hydrophilic sulfonic acid group, the comparative example 2 only introduces the soft segment long chain alkyl ether chain, and the comparative example 3 neither introduces the hydrophilic sulfonic acid group nor the soft segment long chain alkyl ether chain, so the performance in the water resistance temperature, the swelling rate, the tensile strength and the elongation at break is not as good as that of the example 1.

[0059] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and all are included in the protection scope of the present application.

Claims

1. A polyvinyl alcohol, raw materials of which comprise, vinyl acetate 20-60 parts, 2-acrylamido-2-methylpropane sulfonic acid 0.5-1.5 parts, dodecyl vinyl ether 0.5-1.5 parts, oxidizing agent 0.05-0.1 parts, reducing agent 0.03-0.15 parts, sodium chloride 0.01-0.5 parts, deionized water 100-300 parts, wherein, The molar ratio of 2-acrylamide-2-methylpropanesulfonic acid and dodecyl vinyl ether is 1-2:

1.

2. The polyvinyl alcohol according to claim 1, characterized in that, The molar ratio of 2-acrylamide-2-methylpropanesulfonic acid and dodecyl vinyl ether is 1-2:

1.

3. The polyvinyl alcohol according to claim 1, characterized in that, Vinyl acetate 40-50 parts, 2-acrylamide-2-methylpropanesulfonic acid 0.8-1.2 parts, dodecyl vinyl ether 0.8-1.2 parts, oxidizing agent 0.08-0.1 parts, reducing agent 0.06-0.13 parts, sodium chloride 0.01-0.3 parts, deionized water 150-250 parts.

4. The polyvinyl alcohol according to claim 1, characterized in that, Vinyl acetate 50 parts, 2-acrylamide-2-methylpropanesulfonic acid 1 part, dodecyl vinyl ether 1 part, oxidizing agent 0.08 part, reducing agent 0.12 part, sodium chloride 0.09 part, deionized water 200 parts.

5. The polyvinyl alcohol according to claim 1, characterized in that, The oxidizing agent is one or more of potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, and the reducing agent is one or more of sodium bisulfite, ferrous chloride, tartaric acid, mercaptan, and VC.

6. A process for the preparation of polyvinyl alcohol as claimed in any one of claims 1 to 5, characterized in that, The reaction steps include: Step one, add vinyl acetate, 2-acrylamide-2-methylpropanesulfonic acid, dodecyl vinyl ether, reducing agent, sodium chloride and deionized water into the reaction equipment, stir at room temperature, and pass nitrogen to prepare solution A; Step two, heat to 35°C, add the oxidizing agent drop by drop, drop for 2h, continue to react for 0.5-1h, reduce to room temperature, end the reaction, and obtain polymerization product B; Step three, freeze the polymerization product B obtained in step two at -10°C--5°C for 5-12h, thaw at room temperature for 2-5h, filter, and dry at 75°C-85°C to obtain 2-acrylamide-2-methylpropanesulfonic acid / dodecyl vinyl ether / vinyl acetate resin; Step four, dissolve the 2-acrylamide-2-methylpropanesulfonic acid / dodecyl vinyl ether / vinyl acetate resin obtained in step three in methanol to obtain a solution with a mass fraction of 10%-16%, add sodium hydroxide methanol solution for alcoholysis to obtain polyvinyl alcohol resin.

7. The method of producing polyvinyl alcohol according to claim 6, characterized by, The molar ratio of 2-acrylamide-2-methylpropanesulfonic acid / dodecyl vinyl ether / vinyl acetate resin and sodium hydroxide is 1:0.015-0.

025.

8. The method of producing polyvinyl alcohol according to claim 6, characterized by, The molar ratio of 2-acrylamide-2-methylpropanesulfonic acid / dodecyl vinyl ether / vinyl acetate resin and sodium hydroxide is 1:0.02.

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