Patent GB-956175-A (GB)
Title: Synthetic lignocellulose structural products
Inventor: MEILER JOHN GEORGE
IPC: H01J37/305
Filed: 1962-02-12
Abstract: A method of producing a structural hardboard product comprises admixing under substantially dry conditions, lignocellulose fibres with (a) water-soluble two-dimensional phenol-formaldehyde resin of molecular weight between 150 and 3,000 and (b) a water-soluble two-dimensional phenol-formaldehyde resin of molecular weight of from 5,000 to 15,000 in a weight ratio (a):(b) of from 2:1 to 1:2 to provide from 0.75% to 10% by weight of resin per dry weight of fibres; forming the resultant fibre-resin mixture into a unitary mat and compacting the mat into a structural product by means of heat and pressure. The molecular weight of resin (a) is preferably from 200 to 2,000 and resin (b) from 8,000 to 12,000 and the preferred total percentage of resin to lignocellulose fibres is from 1.5% to 5%. The lignocellulose fibres may initially contain from 0.5% to 5% of wax to reduce their water absorption and the mat is preferably compacted to form a hardboard having a specific gravity of from 0.8 to 1.2  In a particular embodiment the lignocellulose fibres initially are separated into two portions the first being admixed with 0.75% to 2.5% by weight of resins (a) and (b) per dry weight of fibres and the second portion admixed separately with from 2.5% to 10% by weight of resins (a) and (b) per dry weight of fibres, both mixtures are then formed into a unitary mat having said first mixture as a core layer and said second mixture as a surface layer and the mat is then compacted into a structional product by means of heat and pressure. U.S.A. Specifications 2,631,097 and 2,631,098 are referred to.ALSO:A method of producing a structural hardboard product comprises the steps of admixing, under substantially dry conditions, lignocellulose fibres with (a) water-soluble, two-dimensional phenol-formaldehyde resin of molecular weight between about 150 and about 3,000 and (b) a water-soluble, two-dimensional phenol-formaldehyde resin of molecular weight of from about 5,000 to about 15,000 in a weight ratio (a):(b) of from about 2:1 to about 1:2 to provide from about 0.75% to about 10% by weight of resin per dry weight of fibres, forming the resultant fibre-resin mixture into a unitary mat and compacting the mat into a structural product by means of heat and pressure. "Phenol" is defined as phenol, cresol, resorcinol or mixtures thereof.  The molecular weight of resin (a) is preferably from about 200 to about 2,000 and resin (b) from about 8,000 to about 12,000 and the preferred total percentage of resin to lignocellulose fibres is from about 1.5% to 5%.  The lignocellulose fibres may initially contain from about 0.5% to about 5% of wax to reduce their water absorption and the mat is preferably compacted to form a hardboard having a specific gravity of from about 0.8 to about 1.2.  In a particular embodiment the lignocellulose fibres initially are separated into two portions, the first being admixed with from about 0.75% to about 2.5% by weight of resins (a) and (b) per dry weight of fibres and the second portion admixed separately with from about 2.5% to about 10% by weight of resins (a) and (b) per dry weight of fibres, both mixtures are then formed into a unitary mat having said first mixture as a core layer and said second mixture as a surface layer and the mat is then compacted into a structural product by means of heat and pressure.  U.S.A. Specifications 2,631,097 and 2,631,098 are referred to.