Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1998-11-20
2000-09-26
Cameron, Erma
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
1563083, 156314, 1563313, 1563317, 162136, 427391, 427393, B29C 3502
Patent
active
061237957
DESCRIPTION:
BRIEF SUMMARY
This application is the national phase of international application PCT/GB97/00440 filed Feb. 14, 1997 which designated the U.S.
BACKGROUND OF THE INVENTION
This invention relates to a method of preparing a sheet of a lignocellulosic material for the manufacture of a finished product and to a method of forming an article or finished product from one or more sheets of a lignocellulosic material so treated.
It is well known to manufacture spirally or convolutely wound paper tubing or angles, the latter referred to as edge board, from kraft paper. Such products are most frequently made by first cutting large reels of kraft paper into reels of limited widths of from 40 mm to 160 mm, and then unwinding the paper from these reels or "biscuits" for multi layer lamination, either over a mandrel in the case of spirally wound paper tubing, or across formers in the case of edge board, the glue between the layers being generally a water based polyvinyl acetate or alkali silicate. The product comes off the line continuously and can then be cut to lengths of any size. The result is a product that is fit for the purposes for which it is presently manufactured.
However, these basic shapes, i.e. tubular or angular sections, are generally not suitable for use in other applications such as high pressure pipes, ventilation pipes, replacements for aluminium extrusions, as poles or posts to hold signs, as fencing poles or posts, as irrigation pipes, or for a host of other applications where the tubular or angular sections are subjected to a greater degree of mechanical or other stress. In these cases, the paper from which the tubular or angular sections are made, must first be modified in order to provide the required degree of water resistance and mechanical strength.
In the manufacture of sheet products, i.e boards or panels, from a lignocellulosic material, it is also necessary to provide the material with the required degree of water resistance and mechanical strength.
Natural fibrous materials or lignocellulosic materials are comprised of hemi celluloses, celluloses and lignin. During the paper making process, the lignins are digested out of the composition, leaving principally the celluloses and hemi celluloses. A change in the moisture content of these materials results in swelling, as a result of their hydrophilic nature, and thus a loss in strength. The reason is that the cell wall polymers of the materials contain hydroxyl or other oxygen containing groups that attract water through hydrogen bonding. It is the hemi celluloses which are the most hygroscopic. Water can give rise to further degradation as a result of attack by micro organisms.
It is known to modify lignocellulosic materials chemically. Various classes of chemical reactions have been used with wood products and these are esters, acetals and ethers produced inter alia by the use of anhydrides.
Examples of documents which teach the use of anhydrides include U.S. Pat. Nos. 4,832,987, 5,055,247 and 5,064,592.
Examples of documents which teach the use of anhydrides to treat a cellulosic material to which there is then applied a polymer, are U.S. Pat. Nos. 5,120,776; 5,385,754 which teaches a process for modifying lignocellulosic material by a chemical treatment method, which method comprises treating the lignocellulosic material with phthalic anhydride and a thermosetting resin selected from phenol formaldehyde resins, urea formaldehyde resins and urethane resins and then curing the phthalalated resin treated product so formed; CA 119:227002; and CA 120:135905.
However, it is undesirable when preparing an article using a glue bond to use a material that gives rise to toxic volatiles or that may be toxic in itself. It is undesirable to have flammable solvents present, and in gluing paper laminates together that have been chemically modified or resinated, solvent or water carriers cannot be accommodated in the adhesive composition, because it is not possible for them subsequently to escape from the composite.
European Patent 0390536 to Plascon Technologies (P
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Cameron Erma
Windsor Technologies Limited
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