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Types of film-forming substances include acrylics, polyurethanes, silicones, and the like.
1) Acrylic water-based emulsion varnish.
Pure acrylic emulsion and propylbenzene emulsion have a high glass transition temperature and the molecular chain is in a frozen state at a low temperature. Increasing the proportion of soft monomer, to a certain extent, can improve the low temperature performance of the coating, but at the same time it also makes the coating sticky at room temperature. In order to improve this situation, Wang Guojian introduced a double-linked third monomer, diethylene glycol bis(a-methacrylate), as a cross-linking agent in the emulsion copolymerization system to gel the latex particles. The low temperature performance of the emulsion coating was studied by dropping 5 g of plasticizer/lOOg emulsion at 80[deg.] C. during the polymerization. Introducing the cross-linking agent into the core-shell emulsion system can improve the shortcomings of the core-shell emulsion which is slightly inferior in hardness, and can also improve the disadvantages of brittleness of the cross-linked system and can prepare an acrylate emulsion with good flexibility. Wang Yanxiang et al. introduced a PBA/PS core/shell latex prepared by a batch-semi-batch process in the polymerization of PBA/PS composite latex with a crosslinking agent (CH2=CCH3-COO-CH2)3-C-CH2-CH3.
In the polymer chain of the self-crosslinking emulsion, there are functional groups that spontaneously condense or co-condense to crosslink the film under certain conditions. Due to the single-component packaging form of the cross-linked emulsion, it is difficult to ensure that the labor intensity and the film quality caused by the low-temperature cross-linked emulsion two-pack packaging are difficult to be fixed. Therefore, the research and development of the cross-linked emulsion, especially the low temperature or room temperature self Cross-linked emulsion research and development, more and more people's attention. Cheng Shiyuan developed the BA-AA-MMA-GMA self-crosslinking emulsion by semi-continuous seed emulsion polymerization. The hydroxyl-containing water-soluble resin they use can be stably suspended in an alkaline medium to uniformly disperse the benzene-acryloyl copolymer film in the medium and improve the stability; and the film-forming material can be further solubilized to prevent the glazing. Film deposits are deposited on the rollers. 2) Polyurethane-based water-based emulsion varnish.
Polyurethane emulsion has the characteristics of softness at low temperature, non-stick at high temperature, softness without reducing strength, and excellent film formation. Zhang Qingsi and other polyurethane emulsion coating, applied to paper finishing. As a result, it was found that in the presence of the diethylenetriamine cross-linking agent, the surface strength of printed paper is high, and the smoothness and whiteness are good. Although the paper gloss is not high, the gloss is soft and natural.
3) Silicone aqueous emulsion polish.
Silicone resins have high weathering resistance, heat resistance, gloss retention, and anti-pigmentation resistance. They can be used for glazing paper replicas, and can improve the strength, brightness, wear resistance, and moisture resistance of paper products. Whiteness and slipperiness are greatly improved, elasticity and brightness are good, no chalking, free from oil, animal and vegetable oil pollution.
3.1.3 Photocurable Water Emulsion Varnish
Photo-curable water dispersion Varnish mainly refers to aqueous emulsion dispersion system. As the cured film has better water resistance, the application prospects are optimistic. The polishing oil developed by Toeda consists of styrene-butadiene latex 100, triethylene glycol diacrylate 20, pentaerythritol triacrylate, cationic photoinitiator ethyl benzoate 1.5, 0.1% PVA10, and water 30. The cured film has good anti-blocking and adhesion properties.
3.2 Water-soluble paper products Varnish
3.2.1 Photocuring water-soluble paper products Varnish
The common paper coating film forming materials are generally urethane acrylate, urethane acrylate/bisphenol A diacrylate, and the like. Polyurethanes have outstanding adhesion, abrasion resistance and low temperature flexibility, while acrylic resins have excellent weather resistance, chemical resistance and gloss. The urethane acrylate oligomer obtained by the organic combination of the two not only reduces the cost, but also combines the advantages of both. Inaba et al. is a polyurethane diol made of 2,4-toluene-propane diisocyanate (MDI), diethylene glycol, dipropylene glycol, and then reacted with 2-methacryloylethyl isocyanate, dispersed in water, and a hexafunctional amino group. The urethane acrylate oligomer and the modified bisphenol A diacrylate oligomer are mixed to obtain a UV-curable oligomer, and the cured lacquer cured film has good gloss and good abrasion resistance.
3.2.2 Volatile Drying Water-soluble Paper Products Varnish
The common film formers are generally alcohol-soluble crotonic acid-vinyl acetate/rosin acid-maleic anhydride polyol polycondensates, benzene-propylene water solubles and the like. Edwards et al. consisted of crotonic acid-vinyl acetate 14, rosin acid-maleic anhydride polyol polycondensation 2.6, isopropyl alcohol 8.5, water, and coalescent additives to form a varnish. In order to more effectively improve the water-solvent-based gloss-type mechanical mechanical properties, people developed a nuclear / shell-type water-soluble coating. Morishita was copolymerized with 20:55:25 St:MMA:MAA, and then 40% of the gloss was obtained by taking 30 parts of a mixture containing 40 parts of St, BA, N,N-dimethylaminoethyl methacrylate in 70 parts. After the oil was eroded, the film had a gloss of 74% and had excellent adhesion, scratch resistance and anti-caking properties. 15 parts of 15:65:20St:MMA:MAA water-soluble polymer developed by Morishita reacted with 40 parts of a mixture containing St40, EA57 and ethylene glycol triacrylate at 80°C to give a gloss of 74%. , Has excellent anti-caking and good adhesion, abrasion resistance.
4 Waterborne Varnish Formula and Technical Specifications
Now more research is the acrylic ester water varnish, the best formula:
Water-soluble acrylic resin: 20% to 30%
Acrylic emulsion: 40% to 50%
Water + ethanol: 30% to 40%
Functional additives: 3% to 5%
The production process is carried out in two steps. The composite resin is first prepared and then the coating oil is synthesized. The technical process is to add a certain amount of water-soluble acrylic resin and other two or more kinds of acrylic emulsions with water and ethanol evenly, and then add additives, etc., and then uniformly measure the relevant indicators.
The main technical indicators of the waterborne varnish developed by the above method are as follows:
Appearance: white lotion
pH: 8-9
Solid content: ≥30%
Viscosity (coating - 4 cups) 25°C: ≥ 30s
5 Application of Waterborne Varnish
At present, the packaging of some high-end goods, such as smoke, wine. Famous tea and some book covers, stickers, pictures, etc., are often printed with some high-gloss water-based polishes. This will not only make the printed surface more bright, smooth, brighter and more vivid, but also play a role in preventing moisture, anti-counterfeiting and abrasion, increased the artistic effect and protection of prints, and increased the added value of goods.
In order to beautify printed matter, protect printed matter, enhance the publicity of printing, and increase the practical value of prints, different prints require different water-based coatings. Ordinary waterborne varnish, suitable for glazing products without special requirements, low price; Super abrasion resistant water varnish, suitable for products with high abrasion resistance requirements, such as shoe boxes, clothes, appliances, beer boxes The polishing of products such as products can completely solve the problem of discoloration of packaging products. Its abrasion resistance can be up to 1000 times; high gloss waterborne coating oil is suitable for products with high gloss requirements and has a certain degree of smoothness and Abrasion resistance, its gloss is as high as 80%; High-brightness wear-resisting water-based polish oil has a very high gloss, good wear resistance, smooth, suitable for polishing high-end products, such as cigarette label, medicine, cosmetics packaging box Etc., its gloss up to 85%, abrasion resistance up to 1000 times, can be hot, good heat sealing; non-slip waterborne coating, suitable for high wear resistance, but do not want the coating cool Sliding products, such as large appliances, equipment packaging boxes.
Author: GAO Yun Fu, Xin Xiulan, XIAO Yang Source: Packaging Engineering
3.1.2 Heat Curable Water Emulsion Varnish