Synthsis And Modification Of Low-Molecular Weight Water Soluble Phenol-Formaldehyde Resol Resin

Phenol-formaldehyde resol resin is widely used in many areas and can not be replaced by other resins due to its unique properties. Ordinary phenol-formaldehyde resol resin is insoluble in water and only dissolves in some organic solvents. However, the phenol-formaldehyde resol resin must be in the form of solution when used in the coating and laminated plastic industry, Water soluble phenol-formaldehyde resol resin was dissolved in water,to protect human health and reducing environmental pollution was used as a goal. Therefore, in-depth research of theory and technology on water soluble phenol-formaldehyde resol resin should be actively carried out, and its application in various fields would be further spread, which is the demand of the sustainable development of phenol-formaldehyde resol resin industry.In this paper, a low weight water soluble phenol-formaldehyde resol resin was synthesized by condensation of formaldehyde and phenol in one process step, with Ba（OH）2·8H2O as catalyst. The optimum conditions of low free formaldehyde content and high methylol group content was obtained by orthogonal experiment. The result showed that the optimal synthesis conditions were as follow: moler ratio of formaldehyde to phenol is 2.3:1, reaction temperature and time is 85℃/140min and catalyst consumption is 4%. Under these conditions, the phenol-formaldehyde resol resin was garnet liquid, with the free formaldehyde content, methylol group content and free phenol content was 1.40%, 23.10% and 2.26%, respectively. Moreover, some other physical and chemical properties were also listed as follow: the viscosity was 13’’50/25℃,gel time was 52’’/160℃,solid content was 41.6% and water mixed of 3 times. Comprehensive analysis with ¹³C-NMR and GPC showed that the product was a mixture consisting of polymers with polymerazation degree from 2 to 4, in which the phenolic ring was linked via methylene at ortho-para and para-para positions, and in the mixture many phenolic rings which were substitued by hydroxymethyls at ortho positions were observed. Further investigation indicated that the Mw of the resin was 485, the Mn was 413, the polydispersity of the resin was 1.17 with narrow moleculor weight distribution. The DSC result showed that the resin was cured via two-step reactions with 144¹68℃and 186¹99℃respectively.Three kinds of flexibilizer were used to modify phenol-formaldehyde resol resin. Results indicated that comparing with non-modified resin, the water soluble phenol-formaldehyde resol resin modified by adipic acid had a lower decomposition temperature of 89℃with lower free formaldehyde, higher waterdilutable ablity and similar storage stability. Higher flexibility of cured adipic acid modified resin was observed. Water soluble phenol-formaldehyde resol resin modified by adipic acid was used as a curing agent of water soluble rosin phenol-formaldehyde resol resin, addition amount was 10%. The results showed that film hardness increased to 6H from 5H without decrease of flexibility and adhesion.