CN115418145A - Water-based thermosetting coating based on polyvinyl alcohol resin with low alcoholysis degree and preparation method thereof - Google Patents
Water-based thermosetting coating based on polyvinyl alcohol resin with low alcoholysis degree and preparation method thereof Download PDFInfo
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- CN115418145A CN115418145A CN202211000982.5A CN202211000982A CN115418145A CN 115418145 A CN115418145 A CN 115418145A CN 202211000982 A CN202211000982 A CN 202211000982A CN 115418145 A CN115418145 A CN 115418145A
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 63
- 229920002451 polyvinyl alcohol Polymers 0.000 title claims abstract description 52
- 239000004372 Polyvinyl alcohol Substances 0.000 title claims abstract description 51
- 238000000576 coating method Methods 0.000 title claims abstract description 44
- 238000006136 alcoholysis reaction Methods 0.000 title claims abstract description 43
- 239000011248 coating agent Substances 0.000 title claims abstract description 38
- 229920005989 resin Polymers 0.000 title claims abstract description 22
- 239000011347 resin Substances 0.000 title claims abstract description 22
- 229920001187 thermosetting polymer Polymers 0.000 title claims abstract description 11
- 238000002360 preparation method Methods 0.000 title claims abstract description 9
- 238000001723 curing Methods 0.000 claims abstract description 21
- 239000006185 dispersion Substances 0.000 claims abstract description 17
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 15
- 239000002904 solvent Substances 0.000 claims abstract description 15
- 229920002689 polyvinyl acetate Polymers 0.000 claims abstract description 13
- 239000011118 polyvinyl acetate Substances 0.000 claims abstract description 13
- 239000000843 powder Substances 0.000 claims abstract description 8
- 239000003960 organic solvent Substances 0.000 claims abstract description 6
- 239000002245 particle Substances 0.000 claims abstract description 6
- 238000001035 drying Methods 0.000 claims abstract description 3
- 238000002156 mixing Methods 0.000 claims abstract description 3
- 238000003756 stirring Methods 0.000 claims abstract description 3
- 239000007788 liquid Substances 0.000 claims abstract 2
- LEQAOMBKQFMDFZ-UHFFFAOYSA-N glyoxal Chemical compound O=CC=O LEQAOMBKQFMDFZ-UHFFFAOYSA-N 0.000 claims description 14
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 12
- 125000002887 hydroxy group Chemical group [H]O* 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 11
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 claims description 10
- 239000012948 isocyanate Substances 0.000 claims description 9
- 150000002513 isocyanates Chemical class 0.000 claims description 9
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 8
- SXRSQZLOMIGNAQ-UHFFFAOYSA-N Glutaraldehyde Chemical compound O=CCCCC=O SXRSQZLOMIGNAQ-UHFFFAOYSA-N 0.000 claims description 7
- 229940015043 glyoxal Drugs 0.000 claims description 7
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 6
- 239000003054 catalyst Substances 0.000 claims description 6
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 5
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 claims description 5
- 239000003513 alkali Substances 0.000 claims description 4
- 238000006243 chemical reaction Methods 0.000 claims description 3
- 230000008569 process Effects 0.000 claims description 3
- 238000001132 ultrasonic dispersion Methods 0.000 claims description 3
- 125000000524 functional group Chemical group 0.000 claims description 2
- 238000010008 shearing Methods 0.000 claims description 2
- 150000004945 aromatic hydrocarbons Chemical class 0.000 claims 1
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims 1
- 150000002576 ketones Chemical class 0.000 claims 1
- 239000000463 material Substances 0.000 claims 1
- GRONZTPUWOOUFQ-UHFFFAOYSA-M sodium;methanol;hydroxide Chemical compound [OH-].[Na+].OC GRONZTPUWOOUFQ-UHFFFAOYSA-M 0.000 abstract description 5
- 238000003889 chemical engineering Methods 0.000 abstract description 2
- 239000012847 fine chemical Substances 0.000 abstract description 2
- 238000010438 heat treatment Methods 0.000 abstract description 2
- 238000010298 pulverizing process Methods 0.000 abstract 1
- 238000001029 thermal curing Methods 0.000 abstract 1
- 235000019422 polyvinyl alcohol Nutrition 0.000 description 35
- 239000011521 glass Substances 0.000 description 5
- 229920000642 polymer Polymers 0.000 description 4
- IQPQWNKOIGAROB-UHFFFAOYSA-N isocyanate group Chemical group [N-]=C=O IQPQWNKOIGAROB-UHFFFAOYSA-N 0.000 description 3
- 239000003973 paint Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 125000003172 aldehyde group Chemical group 0.000 description 2
- 238000004132 cross linking Methods 0.000 description 2
- 238000005187 foaming Methods 0.000 description 2
- 229910021389 graphene Inorganic materials 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000008961 swelling Effects 0.000 description 2
- 229920003169 water-soluble polymer Polymers 0.000 description 2
- 229920000742 Cotton Polymers 0.000 description 1
- 229920000877 Melamine resin Polymers 0.000 description 1
- 239000004640 Melamine resin Substances 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- GZCGUPFRVQAUEE-SLPGGIOYSA-N aldehydo-D-glucose Chemical class OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C=O GZCGUPFRVQAUEE-SLPGGIOYSA-N 0.000 description 1
- 239000003849 aromatic solvent Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 230000005587 bubbling Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 229920000891 common polymer Polymers 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004945 emulsification Methods 0.000 description 1
- 238000007720 emulsion polymerization reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000003759 ester based solvent Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000010528 free radical solution polymerization reaction Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000005453 ketone based solvent Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 150000007974 melamines Chemical class 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 125000000914 phenoxymethylpenicillanyl group Chemical group CC1(S[C@H]2N([C@H]1C(=O)*)C([C@H]2NC(COC2=CC=CC=C2)=O)=O)C 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 239000011253 protective coating Substances 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 230000002087 whitening effect Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D129/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Coating compositions based on hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Coating compositions based on derivatives of such polymers
- C09D129/02—Homopolymers or copolymers of unsaturated alcohols
- C09D129/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
- C09D7/40—Additives
- C09D7/60—Additives non-macromolecular
- C09D7/63—Additives non-macromolecular organic
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Wood Science & Technology (AREA)
- Organic Chemistry (AREA)
- Paints Or Removers (AREA)
Abstract
The invention belongs to the technical field of fine chemical engineering, and particularly relates to a water-based thermosetting coating based on polyvinyl alcohol resin with a low alcoholysis degree and a preparation method thereof. The preparation method comprises the following steps: dissolving polyvinyl acetate in an organic solvent, and adding a sodium hydroxide methanol solution to prepare polyvinyl alcohol with low alcoholysis degree, wherein the alcoholysis degree range of the polyvinyl alcohol is 30-70%; removing liquid from polyvinyl alcohol with low alcoholysis degree, drying, and pulverizing at low temperature into powder with particle size less than 50 μm; dispersing the polyvinyl alcohol powder with low alcoholysis degree in water, and stirring to obtain a water dispersion with a certain consistency; mixing the polyvinyl alcohol water dispersion with low alcoholysis degree and a curing agent according to a certain molar ratio to prepare the waterborne polyvinyl alcohol thermosetting coating with low alcoholysis degree. The coating does not contain VOC, can be cured and crosslinked to form a film under the heating condition, has good water resistance and solvent resistance of the film, has higher hardness, and can solve the problem of high VOC content of the existing aqueous thermal curing coating.
Description
Technical Field
The invention belongs to the technical field of fine chemical engineering, and particularly relates to a water-based thermosetting coating based on a polyvinyl alcohol resin with a low alcoholysis degree and a preparation method thereof.
Background
The water-based paint is an effective way for realizing the environmental protection of the paint, and the core technology is the preparation of water-based resin. Currently marketed resins for aqueous coatings are largely classified into three types, including water-soluble polymers, aqueous polymer dispersions, and polymer latexes. The water-soluble polymer contains a large amount of hydrophilic groups, and even if curing crosslinking is carried out, the water resistance of the coating is generally difficult to meet the use requirement; aqueous polymer dispersions are prepared by a process of solution polymerization followed by emulsification, which dispersions usually still contain a certain amount of organic solvents, resulting in large VOC emissions; polymer latexes are prepared by emulsion polymerization and have very low VOC content, but the latexes are generally difficult to crosslink effectively and the coating properties are limited. Therefore, the field of aqueous thermosetting coatings still faces the problems of low VOC and high water resistance.
Polyvinyl alcohol (PVA) resin is a common polymer, is nontoxic and harmless, and has wide application fields. In the field of coatings, the coating is mainly used for oxygen barrier coatings, interior wall decorative coatings and the like. However, commercially available PVAs have a high alcoholysis degree of 70% or more, and are excellent in water solubility but poor in water resistance. The improvement is generally carried out by blocking part of hydroxyl groups or adding pigments and fillers in the literature. For example, in the invention patent 201110197929.4 in China, methylated melamine resin or methylated urea-formaldehyde resin is added into a polyvinyl alcohol coating to partially seal hydroxyl groups, so that the affinity effect of the polyvinyl alcohol coating with water is reduced, and the moisture absorption phenomenon of the coating is eliminated. In the invention patent 201611026578.X in China, more graphene is added into PVA to improve the water resistance of the coating, but the graphene has high cost and dark color, and the application occasion of the coating is limited.
The invention aims to prepare a water-dispersible PVA resin with low hydroxyl content from the alcoholysis degree of the PVA resin and further provides a water-dispersible PVA resin-based water-based thermosetting coating. The paint has good water resistance and does not contain VOC.
Disclosure of Invention
The invention aims to provide a water-based heat-curable coating which is excellent in water resistance and does not contain VOC and is based on a PVA resin with a low alcoholysis degree and a preparation method thereof.
The invention provides a method for manufacturing a water-based heat-cured coating based on a PVA resin with a low alcoholysis degree, which comprises the following steps:
(1) Preparation of PVA resin with low alcoholysis degree
Dissolving polyvinyl acetate in an organic solvent, slowly dropwise adding a sodium hydroxide methanol solution (namely an alkaline alcohol solution) with a certain mass ratio for alcoholysis, reacting at 40-50 ℃ for 2-4h, and finally adding dilute hydrochloric acid to adjust the pH of a reaction system to 6-7 to obtain PVA with low alcoholysis degree, wherein the alcoholysis degree is 30-70%;
(2) Removing the PVA with the low alcoholysis degree prepared in the step (1), drying, and then crushing at low temperature to prepare resin powder with the particle size of less than 50 mu m;
(3) Dispersing the PVA powder with low alcoholysis degree obtained in the step (2) in water to prepare a water dispersion with certain consistency;
(4) Mixing the PVA water dispersion with low alcoholysis degree obtained in the step (3) with a curing agent, wherein the molar ratio of reactive functional groups of the curing agent to hydroxyl groups in the PVA is in a range of 0.5; and adding a proper amount of water and a catalyst to obtain the zero-VOC aqueous thermosetting coating.
In step (1) of the present invention, the polyvinyl acetate used has a molecular weight in the range of 5000 to 50000g/mol.
In the step (1), the organic solvent is one of tetrahydrofuran, ester solvents, aromatic solvents and ketone solvents.
In the step (1), 30-80% of polyvinyl acetate (volume) is added as alkaline alcohol solution, sodium hydroxide is used as alkali in the alkaline alcohol solution, and the concentration of the sodium hydroxide is 5%.
In the step (1), the alcoholysis degree of PVA is 30-70%; when the alcoholysis degree is too high, the residual hydroxyl groups of the PVA after crosslinking and film forming are too much, and the water resistance of the film is poor; if the alcoholysis degree is too low, the resin cannot swell in water, and thus there is a problem that the internal curing of the resin particles is difficult.
In the step (2) of the invention, the particle size of the resin is less than 50 μm. Too large particle size results in too large surface roughness of the formed coating film, which is not favorable for use.
In the step (3), the viscosity range of the PVA aqueous dispersion with low alcoholysis degree is 1-50 Pa.s, so that the aqueous dispersion has good storage stability. The preferred viscosity range is 10-40 Pa.s.
In the step (3), the dispersion method of the PVA powder with low alcoholysis degree in water is stirring, shearing or ultrasonic dispersion at room temperature for 0.5-3 hours.
In the step (4), the curing agent is one of water-based blocked isocyanate, glutaraldehyde and glyoxal.
In the step (4), if the adopted curing agent is water-based closed isocyanate, the curing temperature is 100-140 ℃; if the curing agent is glutaraldehyde or glyoxal, the curing temperature is 70-90 ℃.
In the step (4), when the curing agents are glutaraldehyde and glyoxal, the adopted catalyst is dilute sulfuric acid; when the curing agent is water-based blocked isocyanate, no catalyst is added.
The aqueous thermosetting coating based on the PVA resin with low alcoholysis degree, which is prepared by the invention, has good film forming property under the heating condition, good water resistance and solvent resistance of a coating film and higher hardness, and can be used as an industrial protective coating.
Detailed Description
The invention is further illustrated by the following specific examples.
Example 1:
185.6g tetrahydrofuran and 84.4g polyvinyl acetate are added into a 500mL four-neck flask, the polyvinyl acetate is completely dissolved at 40 ℃, 30.0g sodium hydroxide methanol solution is slowly added, after 2 hours of reaction, a proper amount of dilute hydrochloric acid is added to adjust the pH value to 6-7, and the polyvinyl alcohol with 31% alcoholysis degree is obtained.
40g of polyvinyl alcohol with 31 percent of alcoholysis degree is crushed to be below 40 mu m at low temperature, then 160g of water is added, and ultrasonic dispersion is carried out for 1 hour to obtain polyvinyl alcohol aqueous dispersion with 20 percent of solid content and the viscosity is 10 Pa.s. 10g of the solution was taken, 3.1g of aqueous blocked isocyanate (molar ratio of hydroxyl groups to blocked isocyanate functional groups: 1: 0.6) and 10g of water were added, mixed homogeneously, applied to a glass plate and cured at 120 ℃ for 2 hours.
The coating film is subjected to water resistance, solvent resistance and mechanical property tests, the water resistance and the solvent resistance are good, and the pencil hardness can reach 2H.
Example 2:
and (2) adding 179.4g of tetrahydrofuran and 81.6g of polyvinyl acetate into a 500mL four-neck flask, completely dissolving the polyvinyl acetate at 40 ℃, slowly adding 39.0g of sodium hydroxide methanol solution, reacting for 2 hours, and adding a proper amount of dilute hydrochloric acid to adjust the pH value to 6-7 to obtain the polyvinyl alcohol with the alcoholysis degree of 57%.
40g of polyvinyl alcohol with alcoholysis degree of 57% is crushed to 20 mu m at low temperature, then added into 160g of water and stirred and dispersed for 2 hours to obtain a polyvinyl alcohol water dispersion with solid content of 20% and viscosity of 30Pa.s. 10g of the solution was taken, 5.6g of aqueous blocked isocyanate (molar ratio of hydroxyl groups to blocked isocyanate functional groups: 1: 0.6) and 15g of water were added, mixed homogeneously, applied to a glass plate and cured at 120 ℃ for 2 hours.
The coating film is subjected to water resistance, solvent resistance and mechanical property tests, the water resistance and the solvent resistance are good, and the pencil hardness can reach 2H.
Example 3:
adding 175.3g of tetrahydrofuran and 79.7g of polyvinyl acetate into a 500mL four-neck flask, completely dissolving the polyvinyl acetate at 40 ℃, slowly adding 45.0g of sodium hydroxide methanol solution, reacting for 2h, adding a proper amount of dilute hydrochloric acid to adjust the pH value to 6-7, and obtaining the polyvinyl alcohol with the alcoholysis degree of 67%.
40g of polyvinyl alcohol with alcoholysis degree of 67 percent is crushed to below 15m at low temperature, then added into 160g of water and stirred and dispersed for 2 hours to obtain polyvinyl alcohol water dispersion with solid content of 20 percent and viscosity of 42Pa.s. 10g of the solution was taken, 8.4g of aqueous blocked isocyanate (molar ratio of hydroxyl groups to blocked isocyanate functional groups: 1.6) and 15g of water were added, mixed homogeneously and applied to a glass plate and cured at 120 ℃ for 2h.
The coating film is subjected to water resistance, solvent resistance and mechanical property tests, the water resistance and the solvent resistance are good, and the pencil hardness can reach 3H.
Example 4:
10g of the aqueous polyvinyl alcohol dispersion obtained in example 1 was added with 0.8g of an aqueous glutaraldehyde solution (50% concentration, molar ratio of hydroxyl group to aldehyde group 1:1), 10g of water and 0.1g of dilute sulfuric acid (10% concentration), mixed uniformly, applied to a glass plate, and cured at 90 ℃ for 2 hours.
The coating film is subjected to water resistance, solvent resistance and mechanical property tests, the water resistance and the solvent resistance are good, and the pencil hardness can reach H.
Example 5:
10g of the aqueous polyvinyl alcohol dispersion obtained in example 2 was added with 1.0g of an aqueous glyoxal solution (40% concentration, molar ratio of hydroxyl groups to aldehyde groups 1:1), 10g of water and 0.1g of dilute sulfuric acid (10% concentration), mixed uniformly, coated on a glass plate, and cured at 80 ℃ for 2 hours.
The coating film is subjected to water resistance, solvent resistance and mechanical property tests, the water resistance and the solvent resistance are good, and the pencil hardness can reach H.
Test methods and results:
(1) Water resistance test
The coatings were tested for water resistance by soaking them in water for 24h according to GB/T1733-1993. Observing whether the coating has the phenomena of color change, bubbling, wrinkling, falling off and the like; the coating has no swelling, foaming, wrinkling, whitening and falling off;
(2) Solvent resistance test
According to GB/T23989-2009, a complete wipe back and forth was performed on the coated surface one hundred times with absorbent cotton soaked with acetone. Observing whether the coating has wrinkling, falling off and other phenomena; the coating has no swelling, foaming, wrinkling, whitish and falling off;
(3) Pencil hardness test
The pencil hardness of the coating film is measured according to the national standard GB/T6739-2006. And inserting a pencil into a pencil hardness tester, pressing the pencil downwards on the surface of the coating film at an angle of 45 degrees, and slowly sliding the hardness tester to obtain the pencil hardness which can not scratch the surface of the coating, namely the pencil hardness of the coating.
The above description is only for the embodiments of the present invention, but the scope of the present invention is not limited thereto, and those skilled in the art can make modifications without departing from the inventive concept, and these modifications are all within the scope of the present invention.
Claims (8)
1. A method for preparing a water-based thermosetting coating based on polyvinyl alcohol resin with low alcoholysis degree is characterized by comprising the following steps:
(1) Preparation of PVA resin with low alcoholysis degree
Dissolving polyvinyl acetate in an organic solvent, slowly dropwise adding an alkaline alcohol solution for alcoholysis, reacting at 40-50 ℃ for 2-4h, and finally adding diluted hydrochloric acid to adjust the pH of the reaction system to 6-7 to obtain PVA with low alcoholysis degree, wherein the alcoholysis degree is 30-70%;
(2) Removing liquid from the PVA with the low alcoholysis degree prepared in the step (1), drying, and then crushing at low temperature to prepare resin powder with the particle size of less than 50 mu m;
(3) Dispersing the PVA powder with low alcoholysis degree obtained in the step (2) in water to obtain an aqueous dispersion with the viscosity of 1-50 Pa.s;
(4) Mixing the PVA water dispersion with low alcoholysis degree obtained in the step (3) with a curing agent, wherein the molar ratio of reactive functional groups of the curing agent to hydroxyl groups in the PVA is in the range of 0.5; and adding a proper amount of water and a catalyst to obtain the zero-VOC aqueous thermosetting coating.
2. The process according to claim 1, wherein the polyvinyl acetate used in the step (1) has a molecular weight in the range of 5000 to 50000g/mol.
3. The method according to claim 1, wherein the organic solvent used in step (1) is one of tetrahydrofuran, an ester solvent, an aromatic hydrocarbon solvent and a ketone solvent.
4. The method according to claim 1, wherein the alkali alcohol solution added in step (1) is 30-80% of polyvinyl acetate, the alkali in the alkali alcohol solution is sodium hydroxide, and the concentration of sodium hydroxide is 5%.
5. The method according to claim 1, wherein the dispersing of the PVA powder with low alcoholysis degree in water in step (3) is carried out by stirring, shearing or ultrasonic dispersion at room temperature for 0.5-3 hours.
6. The method according to claim 1, wherein the curing agent used in step (4) is one of water-based blocked isocyanate, glutaraldehyde, glyoxal;
if the adopted curing agent is water-based closed isocyanate, the curing temperature range is 100-140 ℃; if the curing agent is glutaraldehyde or glyoxal, the curing temperature is 70-90 ℃.
7. The method according to claim 1, wherein when the curing agents used in the step (4) are glutaraldehyde and glyoxal, the catalyst used is dilute sulfuric acid; when the curing agent is water-based blocked isocyanate, no catalyst is added.
8. Aqueous heat-curable coating materials based on polyvinyl alcohol resins with a low degree of alcoholysis obtained by the process according to any one of claims 1 to 7.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211000982.5A CN115418145A (en) | 2022-08-19 | 2022-08-19 | Water-based thermosetting coating based on polyvinyl alcohol resin with low alcoholysis degree and preparation method thereof |
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| CN202211000982.5A CN115418145A (en) | 2022-08-19 | 2022-08-19 | Water-based thermosetting coating based on polyvinyl alcohol resin with low alcoholysis degree and preparation method thereof |
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| CN114773502A (en) * | 2022-05-07 | 2022-07-22 | 安徽皖维高新材料股份有限公司 | Alcoholysis method of polyvinyl acetate |
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2022
- 2022-08-19 CN CN202211000982.5A patent/CN115418145A/en active Pending
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| CN101638540A (en) * | 2009-08-31 | 2010-02-03 | 浙江比例包装股份有限公司 | Polyvinyl alcohol coating fluid and production process thereof |
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