Preparation of Phenol-Formaldehyde Adhesives for High-Ortho Methylol Group Content and Its Properties

Somephenol-formaldehyde adhesives with the contents of low free formaldehyde and high-ortho methylol group are synthesized with barium hydroxide and sodium hydroxide as the composite catalyst and by adding separately formaldehyde in two times.The effects of the molar ratios of phenol and formaldehyde,the mass concentrations of barium hydroxide and sodium hydroxide,and the reaction time on the contents of free formaldehyde,free phenol and methylol group in the obtained phenol-formaldehyde adhesives are investigated by means of orthogona1 experiment.The results have shown that the optimum conditions of the preparing phenol-formaldehyde adhesives are as follow,the molar ratio of phenol and formaldehyde is 1.7,the mass concentration of barium hydroxide is 3.0%,the mass concentration of sodium hydroxide is 2.0% and the reaction time is 2 h.For the adhesive of the above-mentioned formula,the contents of free formaldehyde and phenol are 0.298% and 4.192% respectively,and the content of the methylol group is 36.29%.