초록 ▼

A lamina for a medium density structural board made from dimensioned wood flakes cut from a mixture of hardwood species and having a high retained internal bond strength is disclosed. The wood flakes are blended with a phenol formaldehyde resin having a major quantity of a low molecular weight fract

A lamina for a medium density structural board made from dimensioned wood flakes cut from a mixture of hardwood species and having a high retained internal bond strength is disclosed. The wood flakes are blended with a phenol formaldehyde resin having a major quantity of a low molecular weight fraction and a wax and then formed into a hot pressed product. The lamina may be used alone or as the core of a structural board having veneer, hardboard or plywood face panels. Three or more lamina may be formed into a structural board or used as the core of a board having veneer, hardboard or plywood face panels.

대표청구항 ▼

A medium density structural board comprising at least three lamina bonded together with a thermosetting resin wherein the core comprises a lamina having a density in the range of 40 to 50 pounds per cubic foot comprising wood flakes aligned normal to the length of the lamina, said flakes formed from

A medium density structural board comprising at least three lamina bonded together with a thermosetting resin wherein the core comprises a lamina having a density in the range of 40 to 50 pounds per cubic foot comprising wood flakes aligned normal to the length of the lamina, said flakes formed from a mixture of hardwood species, said mixture of hardwood species flakes comprising between 10 and 90 percent, by weight, high density hardwood species having individual species average specific gravities not less than 0.6, said flakes having a length up to 6.0 inches, a width up to 2 inches and a thickness in the range of 0.010 to 0.100 inch, the ratio of flake length to flake thickness defining a slenderness ratio greater than 30, the ratio of flake length to flake width defining an aspect ratio greater than 1.5, the ratio of the modulus of elasticity across the lamina to the modulus of elasticity along the lamina defining a degree of flake alignment in the range of 1.0 to 7.0; a phenol formaldehyde thermosetting resin in the range of 2-9 percent by weight having a formaldehyde/phenol ratio in the range of 1.4 to 2.0 and containing a major quantity of a low molecular weight fraction; and not more than 5 percent by weight of wax, wherein the retained internal bond strength exceeds about 35 psi, after said lamina is subjected to one cycle of hot water vacuum pressure soak, under 150°F., 15 in. mercury, for 30 minutes, followed by hot water soak (150°F.) at 1 atmosphere for 30 minutes and subsequently oven dried at 180°F. for 16 hours.