Preparation And Properties Of Waterborne Polyacrylate Colloid

Waterborne polyacrylate was one of the commonly used main film-forming substances in waterborne coatings.Due to its wide source,low price,good film-forming property,excellent weather resistance,and high transparency,waterborne polyacrylate had been widely used in the fields of automobiles,wood furniture,architecture,and other fields.However,waterborne polyacrylate possessed poor water resistance,"sticky in heat and brittle in cold",high film forming temperature and long film forming time,which limited its practical application.The water resistance and mechanical properties of the paint film could improve by crosslinking modification from the resin structure,but the defects of high film forming temperature and long film forming time can not be solved.Herein,based on the crosslinking modification of waterborne polyacrylic acid,this study starts from the film-forming mechanism of water-based resin,and achieves the purpose of film forming at room temperature(25°C)by reducing the minimum film-forming temperature(MFFT).Moreover,by introducing specific functional groups into the polymer chain segment,the water-based polyacrylate can lose water quickly and shorten the film forming time.The moin works of this paper are shown as follows:(1)The waterborne polyacrylate emulsion with hard-core and soft-shell structure was prepared by core-shell emulsion polymerization through particle design,and then the emulsion was crosslinked by diacetone acrylamide-adipate dihydrazide(DAAM-ADH)at room temperature.When the glass transition temperature(T_g)of core and shell were 25°C and-8°C respectively,the emulsion showed good film forming and anti-adhesion ability at room temperature,which can effectively avoid the use of film forming aid and reduce the volatile organic compounds(VOC)of emission.The gel fraction of the latex film reached 90.84%and the water absorption decreased to 4.38%when the additive amount of DAAM was 5 wt%,the mass distribution of core-shell was 1:2,and the molar ratio of ADH to DAAM was 1:1,which showed good stain resistance and thermal stability.(2)In the film forming process of high T_g waterborne polyacrylate emulsion,the trimethylolpropane diallyl ether(TMPDE)was added to reduce the MFFT,so that it can form a continuous and uniform latex film at room temperature.The amount of TMPDE increases with the increase of T_g and crosslinking degree.The addition of TMPDE would reduce the MFFT,thermal decomposition temperature,and anti-adhesion property of the latex film.The post-polymerization of the TMPDE in the latex film was ble to be initiated by methyl ethyl ketone peroxide(MEKP)and cobalt naphthenate at room temperature,leading to rapidly recover and improve the T_g,crosslinking degree,pencil hardness,stain resistance,and thermal stability of the paint film.Compared to conventional film forming aids,the TMPDE ultimately become a part of the paint film and will not volatilize after film formation.Considering the advantages of environmental protection and efficiency.The low VOC coating system should be able to apply in the fields of building,furniture,and wood coatings.(3)By introducing N-isopropylacrylamide(NIPAM)into the polymer chain via solution polymerization,a temperature-responsive aqueous polyacrylate secondary dispersion can be prepared.When the temperature was higher than the lower critical solution temperature(LCST),the hydrophilicity of the polymer chain segment decreases and the hydrophobic groups dominate,resulting in the collapse of the micellar structure and the separation from the water to achieve rapid water loss.The LCST of waterborne hydroxyl polyacrylate was closely related to the hydrophilic and hydrophobic ratio,molecular weight and solvent in polymer.By changing the influencing factors,different dispersion of LCST can be prepared to meet with various application environments.Amino resin was used as curing agent to cross-link polyacrylate at high temperature.The results showed that the addition of curing agent amino resin did not affect its LCST.When the mass ratio of waterborne hydroxyl polyacrylate to amino resin MR-4608 was 8:1,the film was cured at 140℃ for 40 min,the gel fraction of the film reaches 85.90%,the pencil hardness was 3H,the adhesion was 0,the water resistance reaches48 h,and the glass transition temperature and thermal decomposition temperature were improved.It has shown certain application prospects in the field of waterborne amino acrylate baking varnish.