Development of the hottest acrylic Waterborne Glaz

Development of acrylate based Waterborne Glazing oil

Abstract: This paper introduces the development process of an acrylate copolymer lotion, which is applied to the printing and glazing process of paper. It has the characteristics of good gloss, wear resistance, water resistance, etc.

preface

with the rapid development of printing technology, making oil return to the oil tank, various forms of printed matter pose more and more problems to related industries, especially the adhesive industry, Take the transformation of packaging paper materials as an example: from the earliest single corrugated box to laminating paper, coating paper to glazing paper to multi-layer "Tetra Pak" composite beverage packaging paper, adhesives from foam alkali to modified starch adhesive, SBS solvent laminating adhesive, copolymerized lotion water-based laminating adhesive, styrene butadiene latex composite paper coating liquid and oily, waterborne polyurethane and acrylate printing glazing adhesive Tetra Pak paper special composite adhesive (one component polyurethane adhesive). Although BOPP and PET plastic film composite paper have the advantages of high gloss, beauty and durability, it is not conducive to the recycling of waste paper products. Therefore, some packaging paper exported to foreign countries are gradually changed to glazing paper that is easy to crush and regenerate. Because packaging paper has special requirements for wear resistance and water resistance, the quality of glazing adhesive is particularly important. At present, solvent Pu, pet UV oil (UV curing) modifies PST glazing oil. The products of water-based glazing oil are not as good as solvent based products in terms of gloss and water resistance and wear resistance, so their application is greatly limited. At present, two-component water-based polyurethane glazing oil (Bayer product) and acrylic ester copolymer lotion glazing oil are widely used. This paper will introduce the synthesis process and characteristics of an acrylate copolymer lotion glazing oil. It has been proved by the manufacturer that the glazing oil has the characteristics of good gloss, wear resistance, water resistance, yellowing resistance and so on

the glazing adhesive requires high glass transition temperature (TG is about 30 ℃) and good film-forming property. It does not crack at low temperature and does not stick at high temperature. Therefore, there are certain requirements on the selection of monomers: it is formed by lotion copolymerization with methyl methacrylate and methyl acrylate with ideal performance as the main monomers, supplemented by a small number of functional monomers such as methacrylic acid and thermal crosslinking monomer - N-hydroxymethylacrylamide, Finally, add a small amount of solvent as a film-forming agent to become an aqueous polish

1 experimental part

1.1 raw materials

the main monomer is methyl methacrylate (the role of MM linear bearing in the tension machine a), the auxiliary monomer is methyl acrylate (MA), methacrylic acid (MAA) functional monomer A and N-hydroxymethylacrylamide, the emulsifier is anion s and non-ionic o, and then adjusted to the correct position according to the requirements. The two kinds of mixed use, the protective colloid is PMA, buffer and initiator (persulfate), Film forming agent T, ammonia water

1.2 preparation method

semi continuous drop polymerization method is adopted. Put the three port round bottom flask equipped with stirrer, thermometer, reflux condenser and dropping funnel on the temperature controlled water bath, add part of water, emulsifier, buffer and monomer, quickly stir for pre emulsification for half an hour, and then pour it into the dropping funnel, then add another part of water to the flask, protect colloid, stir and raise the water bath temperature to about 86 ℃, add part of initiator and quickly drop the pre emulsion for seed polymerization, After the lotion shows obvious blue light, continue to add the remaining pre emulsion until the end. In the reaction process, add the initiator aqueous solution on time to maintain the reaction speed. After the emulsion drops, continue to stir and keep warm for a period of time to make the monomer reaction complete. Cool down, add pH regulator and film-forming agent, filter the material out, and measure the relevant properties

2 results and discussion

2.1 performance test the viscosity, gloss, hardness and adhesion of BYK-Gardner's viscosity cup, dry film tester, Brinell hardness tester and other instruments. The relationship between polymerization stability and emulsifier dosage was determined by collection method, the water absorption of the film was determined by immersion method, and the wear resistance of the coating was tested by friction method

2.2 influence of emulsifier (including protective colloid) on the stability of lotion polymerization

emulsifier has a great influence on the stability of lotion polymerization and the size of latex particles generated. Generally speaking, the amount of emulsifier increases and the condensate decreases. The use of anionic/non-ionic composite emulsifier can give the lotion excellent polymerization stability and storage stability. The selection of emulsifier should consider the different requirements of various comonomers on the oil-water equilibrium value (HLB) of emulsifier, based on the solubility in water, The emulsifiers required for water repellent monomers should be highly lipophilic (non-ionic emulsifiers with small HLB values, such as polyoxyethylene alkyl aryl ethers), while hydrophilic monomers require highly hydrophilic emulsifiers (various anionic emulsifiers with large HLB values). The proportion of anionic/non-ionic emulsifier is determined according to the proportion of various monomers in the copolymerization reaction. The particle size of acrylate polymer latex is small, so more emulsifiers are needed, and the appropriate dosage is 4 ~ 5% of the single volume. Too much emulsifier will reduce the water resistance of the polymer and cause serious foaming in the synthesis process

too little will lead to gel (agglomeration or flocculent precipitation, and more coarse particles) in the polymerization process, so that the lotion cannot reach the required solid content and quality, and the lotion has a rough appearance without blue light, so it cannot be used

the relationship between the amount of emulsifier (including the amount of protective colloid) and the polymer amount (wt%) of the manual rotating lead screw of polymerization coagulation is shown in the table below. Although the control of the reaction may also affect the formation of the condensate, the main cause is related to the amount of emulsifier. Here, only the influence of emulsifier is considered

it can be seen from table 1 that with the increase of the amount of emulsifier (the proportion of emulsifier in the total weight of lotion, wt%), the amount of condensate gradually decreases, the particle size of lotion becomes smaller, and the viscosity increases significantly. The smaller the particle size of lotion and the more uniform the distribution, the higher the gloss and denser the coating, and the better the abrasion resistance and adhesion. After comprehensive consideration, we choose the emulsifier dosage of 2.4%, of which the amount of protective colloid is 0.8%

2.3mma and Ma monomer ratio on performance

the hardness and adhesion of the coating are greatly related to the ratio of soft and hard monomers. The ratio of soft and hard monomers affects the glass transition temperature of the final polymer. The glass transition temperature of the product can be estimated from Gibbs -- DiMarzio formula: 1/tg=wa/tga+wb/tgb+ Wm/tgm, where TG is the glass transition temperature of the copolymer; Ｗａ、Ｗｂ... WM is component A, b The mass fraction of m in the comonomer; Ｔｇａ、Ｔｇｂ... TGM is the glass transition temperature of its homopolymer respectively

hard monomer can give the coating a higher service temperature and a certain gloss, while making the coating scratch resistant. The soft monomer endows the coating with flexibility and film-forming property, and the crosslinked monomer and functional monomer comprehensively endow the polymer like three-dimensional structure, so that the hardness and water resistance and abrasion resistance are improved. It is reported that the introduction of acrylic acid with polar groups can bring polar groups on the polymer side chain, which will increase the adhesion between the coating and the substrate. The addition of methacrylic acid also has a good effect on improving the lotion polymerization process. It is a hydrophilic monomer, which is soluble in both water and oil phases, and can significantly inhibit the formation of condensates. At the same time, the synthetic lotion has good mechanical stability and storage stability. Generally, too much (3 ~ 4%) of the total monomer will lead to the decline of the water resistance and corrosion resistance of the copolymer, and too little will not achieve the effect. Practice has proved that when the glass transition temperature of the copolymer is about 28 ℃, it is most suitable for use as a coating adhesive. The glass transition temperature is too low, the coating surface is sticky, the hardness is extremely poor, and the abrasion resistance is extremely poor, which cannot meet the requirements for use as a coating adhesive; If the glass transition temperature is too high, the hardness is too large, and the coating is cracked and brittle. It is not easy to form a film, has no toughness, has extremely poor adhesion, and has extremely poor water resistance and abrasion resistance. According to the requirements of printing varnish, it should not only have high hardness, but also have good flexibility. Wear resistance and water resistance are important quality requirements. In practice, we add a certain amount of special curing agent for water-based adhesive desmodurda (Bayer company's product) to greatly improve the comprehensive index of the coating and achieve a more ideal value

desmodurda is not added to the above samples, and the results represent the properties of the copolymer itself

through the above control experiments, it is finally determined that the comonomer ratio is mma/ma/maa/ham/hema=50/50/4/4/1. A small amount of film-forming agent is added to overcome the difficulties of gluing caused by high glass transition temperature, which has no impact on the comprehensive properties of the coating. We use xylene as film-forming agent

all the above products have met the use requirements after 1 ton scale-up production and trial use by the manufacturer

3. Conclusion

(1) through the screening of the synthesis process and the distribution ratio of various components, polyacrylate lotion polish with good appearance, good storage stability, moderate viscosity and easy polymerization can be obtained, and its coating is water-resistant and wear-resistant. The properties, hardness and adhesion are good

(2) by adding a certain amount of isocyanate curing agent, the properties of the glazing agent can be further improved, especially the abrasion resistance, water resistance and adhesion

Chen Yuanwu, Chen Zhijun (1. Fujian Institute of chemical fiber and chemical industry, Yong'an 366016; 2. Department of materials science and engineering, Tsinghua University, Beijing 100084)

reprinted from: China carton