Exploration And Practices Of The Large-scale Foaming Technology Of The Smaller Pore Size PVA Collodion With Starch-free

The poly(vinyl alcohol)(PVA)collodion,as a kind of sponge material,is prepared by the foaming and solidification of PVA,which is widely used in the household cleaning area.Currently,the PVA collodion manufacturing technique which uses starch as the pore-forming agent was used by Jaxing Jackson Travel Products Co.,Ltd in the line of collodion industrial production.However,the starch–based technology will cause the high cost,increased water consumption and water pollution,PVA collodion mildewing and other problems.This study,proposed by Jaxing Jackson Travel Products Co.,Ltd,aims to use a new manufacturing technology of PVA collodion to replace the starch–based one.In our previous work,we have finished the research on the starch-free technology of PVA collodion foaming,the technological development of the PVA collodion with larger pore size,the experimental studies over PVA collodion with smaller pore size as well.However,in the pilot scale production of the smaller pore size collodion,which the viscosity of PVA collodion injection molding liquid appeared increasing rapidly,the result was no more than six moulds can be filled with injection molding liquid,with no hope to realize the large-scale production.Thus,the control of the increasing rate in viscosity is a precondition for the realisition of large-scale production in the smaller pore size collodion.In this paper,by analyzing the reason for the rapidly increasing of viscosity,we found the replacement of formaldehyde with small molecule glycol acetal mixture as curing agent or hydrochloric with weak acid G acid as catalyst can control the viscosity change of injection molding liquid effectively.And the starch-free technology of the smaller pore size PVA collodion catalyzed by weak acid G passed the pilot scale production successfully,which the property and apparent appearance of it are comparable to that of Jackson Co.,Ltd original starch–based technology.(1)By contrast with the smaller pore size starch–based technology,the reason for the rapid increase of the viscosity of original starch-free technology of the smaller pore size PVA collodion injection molding liquid was analyzed(the injection molding liquid temperature is 60?,stored within 8 min,the viscosity increased from 1250 mPa·s to 50000 mPa·s).Contrast with the starch–based one,the concentration of PVA,formaldehyde as well as hydrochloric acid in original starch-free technology of the smaller pore size PVA collodion are basically doubled,which causes the acetal reaction rate rapidly increasing.When the injection molding liquid temperature is 60?,stored within 40 min,the acetal degree of injection molding liquid of original starch-free technology increased from 28.3 % to 42.6 %,while the acetal degree of the starch–based one increased from 5.9 % to 18.8 %.The rapid acetal reaction resulted in the increse of the hydrophobic 6-membered acetal ring structure formed on the PVA molecular chain and the insoluble content of the injection molding liquid,which leads to a decrease the movement ability of the polymers,so that the viscosity of the injection molding liquid increases rapidly.(2)Explored the method of controlling the viscosity in the original starch-free technology of the smaller pore size PVA collodion injection molding liquid.Small molecule glycol acetal mixture as curing agent to replace formaldehyde or weak acid G as catalyst to replace hydrochloric acid,which can decrease the increase rate of viscosity in injection molding liquid effectively.When the injection molding liquid temperature is 60?,stored within 40 min,the viscosity of the former increased from 1250 mPa·s to 23700 mPa·s.the latter increased from 1250 mPa·s to 23200 mPa·s.The injection molding liquid of both can accomplish injection molding in a considerable long time completely.Small molecule glycol acetal mixture released formaldehyde by hydrolysis equilibrium to slow down the acetal reaction rate via controlling the formaldehyde concentration of the injection molding liquid.Weak acid G decreased the formation of C+H2OH by reducing acid strength,so that the acetal reaction rate slowed down accordingly.Thus they can control the viscosity of injection molding liquid effectively.(3)Determined the starch-free technology of the smaller pore size PVA collodion optimize formula laboratory test.PVA collodion prepared by small molecule glycol acetal mixture appeared a broken surface.While the property and apparent appearance of the PVA collodion prepared by weak acid G(cure temperature 60?,cure time 33 h)in the laboratory test are comparable to that of the original starch–based technology used by Jackson Co.,Ltd(hardness 12 N,water absorption 975 %,softening time 140 s,shrinkage ratio 9.7 %,apparent density 66 kg/m3,tensile strength 0.35 MPa).(4)Accomplished the pilot scale experiment of starch-free technology in the smaller pore size PVA collodion optimize formula.Weak acid G,as catalyst,can control the viscosity change of injection molding liquid effectively and realize 100 % injection molding in 45 moulds.The property and apparent appearance of PVA collodion prepared in the pilot scale are also comparable to that of the original starch–based technology used by Jackson Co.,Ltd(hardness 12.5 N,water absorption 950 %,softening time 136 s,shrinkage ratio 9.5 %,apparent density 68.5 kg/m3,tensile strength 0.35 MPa).Currently,Jackson Co.,Ltd is busy with equipment customization for the industrialized production of PVA collodion.Once the equipment arrived,the pilot scale starch-free technology would come into production in large-scale.