Preparation Of Cationic Emulsion And Its Application In Wood Blocking Coatings

Cationic acrylic emulsions are based on water as the dispersion medium,and cationic emulsifiers are used as main latex emulsion systems.Cationic acrylic emulsions can be applied to blocking wood primer.At present,due to the continuous improvement of people's living standard and the right energy and the growing awareness of environmental protection,the application field of waterborne coatings is extended continually.But compared to the traditional anionic emulsions,the preparation of cationic emulsion is developed later.There are three main reasons to explain this phenomenon:the slow development of cationic surfactants;the lack of cationic initiator and cationic monomer.With new method for synthesis of cationic emulsion,the limitation of those factors will be made up.Therefore,the application field of cationic emulsions is enlarged.The basic characteristics of cationic emulsion is with positive charge on the surface of latex and polymers themselves.This characteristics will be beneficial to improve the neutralization,adsorption and adhesion of the surface with negative charge.Consequently,the research and development of cationic emulsion has been paid more and more attention.In this paper,styrene,methyl methacrylate and acrylic acid was used as polymeric monomer;cationic emulsifier was used as surfactant and water-soluble free radical initiator was used as initiation system.Emulsion polymerization was used semi-continuous seed emulsion polymerization process.Cationic acrylic emulsion with higher stability and high solid content could be prepared by this emulsion polymerization process.And the application of cationic acrylic emulsion in the field of wood blocking primer was researched.The effect of polymerization process,polymerization temperature,the pre-emulsion dropping speed and stirring speed on the emulsion properties were examined.And the best process conditions were determined:the temperature controlled at 70 ?,stirring speed at 200r/min,the pre-emulsion dropping speed controlled within 4 hours.The research shows that cationic emulsion with higher stability could be prepared by using emulsifier J and OP-10.The best amount of emulsifier was 1.8%of the total monomer;cationic emulsion with stable polymerization performance and short reaction cycle could be prepared by using initiator C.The best amount of initiator was 0.8%of the total monomer;functional monomer AA,HEA,N-MA,GMA introduced into cationic emulsion polymerization would be beneficial to improve the polymerization stability of cationic emulsion.The best distribution ratio of functional monomer were 0.5%?2%?0.5%?1.2%.The research also shows that the emulsions prepared by core-shell emulsion polymerization process had lower MFFT,higher hardness and better film properties than emulsions prepared by conventional emulsion polymerization process;when increased the amount of St monomer,the sealing property of cationic emulsion was enhanced.The best amount of St monomer was 18.5g;GMA monomer introduced into cationic emulsion was beneficial to improve the sealing property.The best amount of GMA monomer was 1.2%of the total monomer.