Study On Sheet Varnish Prepared By Modified Polystyrene Foamed Plastics

Polystyrene foamed plastics are widely used in packing because of light quality, heat insulation and shock proof. Offal caused greatly hazard. Making full uses of polystyrene has being one of hot spots studied by people. To be coating modified by Waste plastics has simple operation, meanwhile, resources are multiple utilization and Environment pollution is controlled in this way, which is of society advantages and economic advantages.Three parts were studied in this article, including synthesis of modified resin of polystyrene(PS); synthesis of amino group resin containing low free formaldehyde; preparation of varnish and film coating test.polystyrene is a kind of nonpolarity macromoleculer, has poor adhesive power on matrix. In order to achieve modification for improving polarity, polar monomer is grafted onto polystyrene. The technology of maleic anhydride (MAH)grafted onto polystyrene in medium of 2-butanol-acetoacetate-xylene was studied, the variance results showed by orthogonal test that the amount of initiator and monomer had a great impact on grafting reaction;soaking time had a certain impact on grafting reaction;reaction time had tiny impact on investigation range.The optimal conditions were found by orthogonal balance method as follow: BPO (benzoyl peroxide) 1%, MAH3%, soaking time 3 h, reaction temperature 100℃, the rate of stem grafting was 1.24%, the efficiency of stem grafting was 93.2%. Infrared spectrogram demonstrated that poly maleic anhydride, generated in the reaction, and monomers left can be removed by purified and also proved that MAH was grafted onto PS as saturated helices.The synthesis of amino resin process for low free formaldehyde was studied based on traditional technology. The optimal conditions as follow: hydroxylation 2.5 h, etherized time 2 h, reaction temperature around 90℃,water distribution -atmospheric distillation - vacuum distillation for dehydration, vacuum distillation time for dealcoholize 15min, temperature 85℃, degree of vacuum -0.085Mpa. The optimal conditions of formula as follow: n_{mela min e}: n_formaldehyde:n_{2-bu tan ol} =1:6.2:6.6 , magnesium carbonate 0.2%, phthalic anhydride 0.3%, xylene 12%, free formaldehyde content of amino resin prepared under the conditions was lower than 585-1's, and the content was dropped below 1%, solid content 62±2 %, viscosity 80-100s (tested by coating 4 cup), tolerance degree 3.5±1,adhensive power can reach 1 grade, good alcohol soluble, the product sealed save five months without gel.PS modified resin self made, which had moderate viscosity, can be used directly as one of compositions of varnish without dilution. Amino resin strengthened adhesive power of PS resin. The product formula was determined through the single factors as follow: PS modified resin 90.2%, amino resin 6.8%, plasticizer 3.0%, a bit of leveling agents. Varnish prepared in this way was of translucent and shallow yellow mucilage, which can applied without dilution, drying time 40s under ambient temperature, min viscosity, firm content 48%, adhesive power 2 grade, water tolerance exceeded 24h, glossiness 92°.