| There are still problems such as reaching nation stardard of formaldehyde emission and mechanical properties, high production costs , technology operation and so on since nation standard on limits of formaldehyde emission of wood panels and finishing products is forcibly carnied out . Researches and applications of enviroment protection UF are the main focus because it is the key factar to restrain the industry developments.The researches begin with technology problems during utilization of enviroment protection glues. They include viscosity stabilizer, the use of nin CaCO3 , the effects of methanol in formaldehyde material, the synthesis and coupling-chelating of low free formaldehyde glues, the synthesis and application of gas film produced low free formaldehyde glues, starch glue of composition of recycling resources and so on. The technology got the authentication of china enviroment symbol and passed the appraisal of experts ofprovince level. The technologies are in the lead in plywood use and have good social and economical benefit.The results from both preparation of low free formaldehyde resin and its application in plywood were summarized as follows:1. The storage atability of the undehydration UF adhesive is the question need to be solved immediately, the study has sieved sodium dodecyl sulfonate, ZHJ-68 from six kinds of addition agent (They are stearic acid, sodium dodecyl sulfonate , OP-10, Tween 80, silicone oil, ZHJ-68), while ZHJ-68 is an ideal viscosity stabilizer , the glued strength of dry or wet can achieve GB criterion.2. The effect of nanometer calcium carbonate on the curing time, free formaldehyde and adhesive strength of UF resin are researched . The results show that nanometer calcium carbonate delayed the curing time of resin, freeformaldehyde was decreased as the nanometer calcium carbonate was added, which had a little contribution to adhesive strength of plywood.3. The chapter studied on the influence of methanol in formaldehyde on low formaldehyde (low molecular ratio) UF resin, Results showed that more content of methanol in formaldehyde prolonged the storage time of formaldehyde, heightened the storage stability , led to more free formaldehyde in the resin, increased formaldehyde emission form plywood, The pot life &gelation time would be shortened by use NH4C1 as hardening agents, While the pot life & gelation time would be prolonged by use oxalic acid or10% HC1 as hardening agents. Further testing on the bond strength showed that more content of methanol would lower the wet strength of plywood and decrease the wood failure ratio. When the synthetic resin is made with 1 : 1. 1 rate mol(U : F)and higher than 6.0 percent of methanol in formaldehyde. The wet bond strength of poplar-core plywood could not reach to 0. 7 MPa the level of GB/T 9846-1998, and the wet bond strength of lauan-core plywood also decreased greatly, while the dry bond strength is hardly influenced. The 400 Hz 1H NMR showed that more content of methanol would lead to more content of hydrated formaldehyde in the resin and the group of -OCH3 would be increased, the SEM showed that resin graph was in tree shape on the lower methanol content resin, while in loose shape on the higher methanol content resin.4. By low molar ratio of urea and formaldehyde, Both the mechanical properties and formaldehyde emission theory in plywood of the new syntheticed resin are analyzed and discussed. The results show that: based on selecting propal molar ratio(F/U 1.3), changing synthetic technology, adding coupling-chelating agent(1.0%) and so on. Low - toxicity UF resin with good comprehensive performances could be made . And the formaldehyde emission amout of plywood meets GB18580-2001 E1( 1.5mg/L) Standard. The mechanical prorerties could meet reguirement specified in standard GB/T9846-1988 & GB/T15104-1994.5. By the use of adding bubbling agents halfway and mass-transmitting between liquid and gas, the low-toxicity UF resin was synthesized and the content of the free formaldehyde was re...
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