Modified vinyl acetate resin emulsion

PVAc emulsion has excellent adhesive properties, simple production methods, inexpensive raw materials and no pollution, and is widely used in wood processing, paper processing and other aspects. In many applications, PVA is used as a protective colloid for vinyl acetate (VAc) emulsion polymerization. Due to the water solubility of PVA, there is a problem of water resistance in its application. Many people have done a lot to improve the water resistance of PVA. If a fatty acid having 8 to 12 carbon atoms is reacted with VAc, a copolymer containing a small amount of a higher vinyl carboxylate is obtained and saponified to obtain a PVA containing a higher vinyl carboxylate. Alternatively, VAc may be copolymerized with a small amount of a higher alkyl vinyl ether, and then the copolymer may be saponified to obtain a PVA containing about 1 mol of higher alkyl vinyl ether having a degree of saponification of 79% to 95% (mol), which is used in a vinyl single product. Body lotion or protective colloid during suspension polymerization. Reacting with divinyl ketone and PVA to acetoacetylate PVA to obtain a PVA with a degree of acetoacetylation of 1% to 10% (mol), which is used as a protective colloid for VAc emulsion polymerization to obtain a very strong water resistance film. Emulsion. In recent years, many improved performance PVAc emulsions have been developed by increasing the water resistance of the emulsion and reducing or adjusting the MFT of the emulsion.

1 PVAc Emulsion for Plastic Film Adhesion <br> To reduce PVAc Emulsion MFT, phthalate plasticizers or butyl cellosolve, butyl carbitol and other high-boiling solvents are generally used, especially at lower temperatures. Under the former, the amount of the former is very high. As a result, the cohesive strength of the rubber is decreased, and the heat resistance and creep resistance are deteriorated. Although the film forming property is superior to the former, the price is high and there is a special odor. Adding isopropyl benzyl alcohol or a derivative thereof to a PVAc emulsion can achieve very good film forming properties. For 100 parts by mass (all mass percentages not otherwise specified below) of the PVAc emulsion, 2.5 parts of isopropylbenzyl alcohol was added, the MFT was 1C, and the normal bond strength was 16.7 MPa. When 4.5% DBP was added, the MFT reached 1°C and the normal bond strength was 14.5 MPa. The isopropyl benzyl alcohol has no odor and does not cause the formation of agglomerates. The alkylene glycol monoalkyl ether carboxylate may be used as a homopolymer containing VAc as a main component or in a copolymer emulsion containing only one kind of monomer among vinyl, acrylic and vinyl versatate. A PVAc emulsion adhesive for plastic film and coated plastic paper was prepared. In the copolymer emulsion containing VAc as the main component, VAc accounts for 60% to 100% of the total monomer amount. When the VAc content is less than 50%, the copolymerization property deteriorates, the residual monomer content increases, and the stability is also low. The solid content of 30% to 60%. Such carboxylic acid esters have good solubility to polyvinyl chloride, polyolefins, polyesters, etc. When the paper coated with these resins and their films are adhered, the compatibility between the adhesive and the adherend is improved, and Get higher bond strength. The amount added is 10-30 parts per 100 parts of PVAc emulsion (in terms of solids content), less than 1 part does not show the effect, and more than 40 parts the emulsion stability deteriorates. The method of addition is not limited, but it is desirable to add after the polymerization is completed in consideration of not affecting the polymerization reaction. For systems that are easily soluble or easily dispersible, they can be added as they are. On the contrary, it is recommended that they be diluted with water to a 25% to 50% aqueous solution and then added. A practical emulsion is a vinegar-propylene copolymer emulsion having a VAc:2-EHA=400:100, a solids content of 54%, a Sumitomo Chemical Industry Co., Ltd. product 400, a VAE emulsion having a solids content of 55%, and a central chemical and physical industry company. System WH-909, solids content 55%. The carboxylic acid esters used were ethylene glycol monomethyl ether acetate and propylene glycol monomethyl ether propionate in an amount of 5% to 20%.

2 High Viscosity, High Water Resistance Emulsion <br> Water-soluble glyoxal PVA is used as a protective colloid for ethylene emulsion polymerization. The obtained emulsion film has significantly improved water resistance, high emulsion viscosity, placement stability, and pigments. Emulsion with excellent urea-formaldehyde resin mixing and freeze-thaw stability. When formaldehyde or acetaldehyde is used instead of glyoxal, the water resistance of the emulsion film deteriorates. Glyoxal PVA colloidal PVA and glyoxal were heated and acetalized in water or organic solvent by acid catalysis. As the reaction proceeded, the viscosity of the reaction solution increased, and the degree of reaction was determined by measuring the viscosity. When the degree of acetal reached 0.3%, the water resistance of the emulsion film was improved, and when the viscosity reached 20%, the viscosity of the emulsion was greatly increased, and the water resistance of the film was further increased. However, the emulsion was easily gelled, the film was easily peeled off, and the adhesiveness was decreased. In order to meet the above requirements, the degree of acetalization is suitable for between 1% and 15%, practically 2%, 5% and 7.5% of the products, corresponding to a molar ratio of glyoxal to vinyl alcohol of 0.42%, 1.07% and 1.66%. There is no specific limit to the PVA used. Partially saponified PVA glyoxal, its water resistance is better than partially saponified PVA. The amount of glyoxal PVA used varies depending on the type of PVA, the degree of condensation of glyoxal, and the required amount of the emulsion resin, and is generally 1% to 10% (mol) of the total amount of the emulsion polymerization system. The practical amount in the example is 2.7. %, 4.0% and 5.0%.

3 High viscosity, high fluidity, high water resistance woodworking emulsion <br>The use of ethylene modified PVA and cellulose as protective colloids to prepare high viscosity, good fluidity, water resistance, excellent adhesion to wood PVAc emulsion [[ 9]. For the vinyl alcohol copolymer used herein having an ethylene content of 0.5% to 10% (mol) and a degree of saponification of 80% or more, it can be produced by a general method, that is, a method of first copolymerizing VAc with ethylene and then saponifying it. The cellulose used in combination with the ethylene-modified PVA has a 2% aqueous solution, HEC, MC, and CMCNa having a viscosity of 1000 to 8000 mPa·s. Ethylene PVA having an ethylene content of 0.5% to 10% by mole and a degree of saponification greater than 80% has a degree of saponification of 80% by mole, and more desirably more than 95% by mole. The saponification degree is less than 80% (mol), and the water resistance of the emulsion may not be sufficient. Although there is no definite requirement for its degree of polymerization, it is preferably between 300 and 3,000. Less than 300 does not have a protective colloid function, more than 8000 is difficult to produce. The optimum ratio of ethylene-modified PVA (A) and water-soluble high-molecular cellulose (B) is 9.8:0.2 to 7:3. When the ratio is more than 9.9:0.1, the prepared emulsion has a low viscosity, and when the ratio is less than 5:5, the emulsion fluidity deteriorates. The total amount of the two is 5% to 15% of the resin in the emulsion polymer, that is, 5% to 15% of the total amount of the monomers. Using this ethylene-modified PVA as the protective emulsion polymerization emulsion mainly composed of VAc, the prepared PVAc emulsion has high viscosity, good fluidity, and good water resistance and low temperature stability. Suitable for assembling boards, glulam, slicing single-layer boards, plywood processing, plywood secondary processing, general woodworking adhesives, impregnated paper, adhesives for non-woven products, repair materials, coatings, paper processing and fibers Used in processing and other fields.

4 Water-resistant boiled vinegar-acrylic emulsion with excellent adhesive force <br>When VAc is copolymerized with carboxyl-containing vinyl monomer emulsion, the aforementioned ethylene-modified PVA is used as protective colloid to obtain emulsion (A) and then added. The aluminide (B) produces a copolymer emulsion that is water-resistant and has good bonding strength. The suitable mass ratio of carboxyl-containing vinyl monomers to VAc monomers is from 0.03 to 2:100. When it is less than 0.01, the water resistance and the water-resistant boil-off adhesive force are insufficient, and when it exceeds 3, the polymerization stability may be deteriorated and the polymerization reaction may not be performed. As the aluminide, there are aluminum chloride, aluminum nitrate, aluminum sulfate (gentleman), among which AlCl3 is the best, and Al(NO3)3 is the second. For the composition of deionized water 300g, PVA [DP1000, OH99.3% (mol), ethylene content of 7.0% (mol)] 26g, VAc: AA = 99.5:0.5 (total monomer is 360g) mixed evenly after An emulsion prepared under a redox initiation system was added dropwise over 3 to 3.5 hours, and 5 parts of DBP was added per 100 parts to become emulsion (A). For every 100 parts (A) (solids) plus 0.5 parts of AlCl3, the water absorption rate of the emulsion film was 20.1%, the dissolution rate was 0.5%, the boiling water-resistant adhesive strength was 2.1 MPa, and there was no change in the viscosity at 5-40°C. If 0.5 part of AlCl3 was changed to 1 part of Al(NO3)3, the water absorption was 19.8%, the dissolution rate was 0.4%, the boiling water adhesive strength was 2MPa, and the viscosity did not change at 5-40°C; the same emulsion (A) ), When the aluminide is not added, the water absorption rate is 38.7%, the dissolution rate is 3.5%, the boiling water-resistant adhesive strength is 0.2 MPa, and there is no change in the viscosity at 5-40°C.

5 Needle-leaf wood plywood <br> Water-resistant composition In the past, plywood was mainly produced with amino resin adhesives such as melamine formaldehyde and urea formaldehyde. In recent years, in order to reduce formaldehyde hazards, the use of VAc or its modified resin adhesives has gradually increased. In addition, since the amount of plywood produced from coniferous wood is gradually increasing, and the amount of resin contained in coniferous wood is high, conventional adhesives for hardwood single-layer boards are difficult to adapt. 20%-95% of vinyl acetate acrylic copolymer emulsion and 80%-5% of water soluble phenolic resin (optimal composition ratio of 30% to 90%: 70% to 10%) composed of modified vinyl acetate emulsion adhesive The adhesive can meet the requirements, and the formaldehyde content is lower than the ASF-1 standard. The monomer composition of the acetic-acrylic copolymer emulsion contains 0.1% to 20% of acrylic acid in addition to vinyl acetate and (meth)acrylate. A small amount of AA can improve the water resistance of the film and the resistance to boiling water, promote the curing of the amino resin, neutralize some of this basic substance, and chelate and crosslink with a certain metal ion. The lack of AA content (<0.1%) has little effect, and the polymerization rate is significantly lower than 20%, and the viscosity is abnormally increased, and it is difficult to use. When the water-soluble amino resin is produced, the phenol:formaldehyde:catalyst (base) is 1:1 to 3:0.5 to 0.5 (mol/mol), and the water solubility of the control resin is 250%. The amount of amino resin is more than 80%, the viscosity of the adhesive is too low, the rubber coating on the single layer is insufficient, the amount of formaldehyde emission is large, less than 5% curing is not complete, and the water resistance does not meet the requirements.