| Waterborne polyacrylate binder is widely used in water-based ink industry because of its low price,high gloss and excellent corrosion resistance.But compared with solvent-based ink,there are still many deficiencies for water-based ink,such as low drying and curing speed caused by slow evaporation of water,poor storage stability of the latex due to easy hydrolysis of eater bonds in the polyacrylate resin,poor adhesive and poor leveling in PE or PP substrates due to low polarity of PP or PE and high surface tension of the latexes,and so on.In this paper,waterborne solid acrylic resin was used to replace the traditional emulsifier to prepare polyacrylate latex binder,and the effects of waterborne resin on latex properties and crosslinking curing reaction were studied.The formulation and polymerization process were optimized in order to acquire a polyacrylate latex with high solid,low viscosity,small fineness,fast drying speed,good resolubility and leveling performance for meeting the needs of production and application.The main contents of this paper are as follows:(1)The effects of several different types and dosages of resins,the neutralization degree of waterborne resins,and different waterborne resin compounding systems on various properties of connection materials were studied in detail.It was found that the type,dosage,neutralization degree and compounding ratio of the resin have great influence on the performance of the emulsion.When the ratio of A and B is 6/1,the dosage is 25%and the neutralization degree is 120%,the polyacrylate emulsion with good storage stability,small particle size(89.6 nm),low viscosity(189 mPa·s),full drying time of 100 s and good flowability can be prepared.(2)The effect of waterborne resin type on the crosslinking curing reaction of the binder during film formation was studied.It is found that the type of resin has a great influence on the crosslinking curing reaction of the latex films,while the dosage of resin has a relatively small influence on the crosslinking curing reaction.For the latex prepared by A,the activation energy of crosslinking curing reaction was E=3.34 kJ/mol,and the reaction order was n=0.767,which was relatively small,meaning that its crosslinking curing reaction is relatively easy.In addition,it is found that the greater the amount of resin,the easier the crosslinking reaction.(3)The effects of neutralizer types on the emulsion fineness,resolubility and drying rate were studied.It was found that using sodium hydroxide,amp-95 and ammonia as compound alkali neutralizer,and when sodium hydroxide/amp-95/ammonia is 2/1.5/6.5(mass ratio),a latex binder with particle size of 103.0 nm,viscosity of 188 mPas,small fineness(0-5 μm),good resolubility,fast drying speed(83 s)and excellent comprehensive performance can be prepared.Using a small amount of small molecule emulsifier COPS-1 can significantly improve the levelness of the latex and its corresponding inks,and improve the adhesion(0.1 grade).(4)The effect of initiator and chain transfer agent on latex fineness and adhesion was studied.When the amount of initiator is 7‰,a poly acry late latex with fineness of 5-10 μm and adhesion of 0 grade can be prepared.When the amount of chain transfer agent is 5‰,polyacrylate latex with fineness of 5-10 μm and adhesion of 0.5 grade can be prepared.(5)The pH value of the latex during storage has a certain influence on storage stability.The more neutral the pH value is,the better the storage stability is.The seed polymerization process has an effect on the fineness and storage stability of the latex.The latex prepared by adding initiator directly has small fineness and good storage stability.The post-elimination redox system with water as solvent,tert-butyl hydrogen peroxide as oxidant,ascorbic acid as reducing agent and the ratio of 2/1 had the best treatment effect on eliminating residual monomer,and the residual monomer can be reduce to less than 0.3%.(6)A step-by-step scale-up production study was completed from 20 L to 500 L then 2000 L.The problems of fineness increase and monomer residual increase occurred in the process of large-scale production were solved.The product performance has been recognized by cooperative enterprises and users. |
