Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Noninterengaged fiber-containing paper-free web or sheet...
Reexamination Certificate
2001-07-12
2004-03-30
Seidleck, James J. (Department: 1711)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Noninterengaged fiber-containing paper-free web or sheet...
C428S297400, C428S298100, C428S537100, C524S013000, C524S014000, C524S417000
Reexamination Certificate
active
06713168
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to fire retardant wood composite materials for use in the commercial and residential building industry. In particular, organophosphorus fire retardant chemicals are incorporated into wood composite materials to achieve a high level of fire retardancy, while maintaining the quality and strength of the wood composite.
BACKGROUND OF THE INVENTION
In the past, the forest product industry has continued to seek and develop cost-effective fire retardant chemicals for use in wood composite materials, such as particleboard, fiberboard, oriented strand boards, agricultural straw board and inorganic building materials such as gypsum boards. Typically, acceptable fire retarding performance is achieved by manufacturing and incorporating a fire retardant compound in the wood composite. Although processes for preparing fire retardants for wood composite materials are known, there is a continuing need for a more cost-effective, environmentally beneficial means to satisfy flame retardant specifications, while maintaining the quality and strength of the wood composite materials.
Prior attempts to incorporate fire retardant organic phosphate esters into wood composite materials have met with little success, primarily because reactions between the phosphate ester and isocyanate binder can be unpredictable and can lead to pre-curing and interfacial strength loss during composite manufacture. Furthermore, some phosphate esters are easily decomposed under the hot press conditions during the manufacture of wood composites. Finally, phosphate esters generally tend to leach out of the composite over time, thereby making these phosphate esters undesirable and environmentally unfriendly fire retardant additives.
BRIEF SUMMARY OF THE INVENTION
In one object of the present invention, the invention includes a fire retardant wood composite material comprising a polymeric binder, and characterized in that the material further comprises at least one organophosphorus ester.
A further object of the present invention is a process for preparing a fire retardant oriented strand board composite material. A first step in this process is coating wood strands or flakes with at least one polymeric binder, wax, and at least one organophosphorus ester and forming a mat of the coated wood strands or flakes. A further step in this process is compressing the mat under heat and pressure to form an oriented strand board composite panel, characterized in that upon compression the at least one organophosphorus ester forms cross-links between polymer chains of the at least one polymeric binder resin.
Preferably, the organophosphorus ester has the formula:
wherein R
1
, R
2
and R
3
are either alkyl or aryl chains having hydroxyl, carboxylic or both hydroxyl and carboxylic functionality.
An object of the present invention is to provide a fire retardant wood composite material wherein an effective amount of organophosphorus fire retardant chemicals are incorporated into a wood composite material to form a wood composite material having a high level of fire retardancy.
Another object of the present invention is to provide wood composite materials comprising organophosphorus fire retardant additives, characterized in that the organophosphorus fire retardant additives cross-link with the polymeric binders and wood composite materials, thereby preventing leaching of the organophosphorus materials from the wood composite material. In addition, this cross-linking ameliorates the strength loss that typically accompanies the addition of functional additives like fire retardants, and also improves the dimensional stability and durability of the composite panel.
Accordingly the wood composite materials prepared according to the present invention have a limiting oxygen index of about 26 to about 40, an average thickness swelling in the range of about 7% to about 15%, and a fire spread rating of greater than about 25 and less than about 75.
Other objects, features and advantages will be readily apparent from the following detailed description of preferred embodiments thereof.
All parts, percentages and ratios used herein are expressed by weight unless otherwise specified. All documents cited herein are incorporated by reference. Concentrations of the polymer resins, waxes, fire retardants and other additives that are included in the wood composite materials of the present invention are calculated based on the weight of the over-dried wood flakes or strands.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a fire retardant wood composite materials that incorporate organic phosphorus esters as a fire retardant, as well as processes for their manufacture.
As used herein, “wood” is intended to mean a cellular structure, with the cell walls being composed of cellulose and hemicellulose fibers bonded together by lignin material, which functions as a type of polymer cement.
By “wood composite material” it is meant a composite material that comprises wood and one or more other additives, such as adhesives or waxes. Non-limiting examples of wood composite materials include oriented strand board (“OSB”), waferboard, chipboard, particle board, fiberboard, and plywood. As used herein, “flakes”, “strands”, and “wafers” are considered equivalent to one another and are used interchangeably.
Preferred wood composite materials utilized in this invention are derived from naturally occurring hard or soft woods, singularly or mixed, whether such wood is dried (having a moisture content of between 2 wt % and 12 wt %) or green (having a moisture content of between 30 wt % and 200 wt %). Preferably, the wood composite materials comprise dry wood parts having a moisture content of about 3 to 8 wt %. Typically, the raw wood starting materials, either virgin or reclaimed, are cut into strands, wafers or flakes of desired size and shape, which are well-known to one of ordinary skill in the art.
In the commercial manufacture of OSB panels, after the strands are cut they are dried to a moisture content of about 2 wt % to 5 wt % and then coated with a polymeric thermosetting binder resin and wax additive. Conventionally, the binder, wax and any other additives are applied to the wood materials by one or more spraying, blending or mixing techniques. One such technique is to spray the wax, resin and additives upon the wood strands as the strands are tumbled in a drum blender. Binder resin and various additives applied to the wood materials are referred to herein as a coating, even though the binder and additives may be in the form of small particles, such as atomized particles or solid particles, which do not form a continuous coating upon the wood material. Fire retardant chemicals are incorporated either before, during or after coating of the wood materials. These fire retardant chemicals may be sprayed on the wood materials, or in the alternative, premixed with the binder and/or wax additive. The blended mixture is formed into either a random mat or oriented multi-layered mats. In particular, the coated wood materials are spread on a conveyor belt in a series of alternating layers, where one layer will have the flakes oriented generally in line with the conveyor belt, and the succeeding layer oriented generally perpendicular to the belt, such that alternating layers have coated wood materials oriented in generally a perpendicular fashion. Subsequently, the formed mats will be pressed under a hot press machine which fuses and binds together the wood materials to form consolidated OSB panels of various thickness and size. Preferably, the panels of the invention are pressed for 2-10 minutes at a temperature of about 175° C. to about 240° C. The resulting composite panels will have a density in the range of about 40 to about 50 pcf (ASTM D1037-98) and a thickness of about 0.25 (¼″) to about 1.5 (1½″) inches.
Various polymeric resins, preferably thermosetting resins, may be employed as a binder for the wood flakes or strands. Preferred polymeric binders include isocyanate resin, ur
Liu Feipeng
Ou Nian-hua
Bissett Melanie
Goodrich David Mitchell
J.M. Huber Corporation
Nieves Carlos
Seidleck James J.
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