Composites prepared with ready-to-use resin/wax emulsion adhesiv

Details Composites prepared with ready-to-use resin/wax emulsion adhesiv Composites prepared with ready-to-use resin/wax emulsion adhesiv

1997-03-03

2000-10-17

Davis, Jenna

Stock material or miscellaneous articles

Composite

Of wax or waxy material

1563313, 1563319, 156335, 428528, B32B 2100

Patent

active

061328855

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention is directed to a single package, ready-to-use (RTU) adhesive combining a thermosetting resin and a wax emulsion sizing agent, a process for preparing the adhesive composition and the use of the adhesive in making bonded composites such as wood products, including, parallel strand lumber, oriented strand board (OSB), wafer board and particle board, and textile products, including ceiling tiles.


BACKGROUND OF THE INVENTION

There are a variety of adhesives for composites such as particle boards, fiber boards, and textile composites. Generally these adhesives are made from urea resins, urea-melamine resins, phenolic resins, and the like. In order to impart sufficient water-resistant properties to the constructions made with these resins, attempts have been made to combine a wax emulsion sizing agent with the resin. However, it has been very problematic to obtain a stable blend of resin and wax emulsion. Wax solids may not remain homogeneously suspended in mixtures with water-borne resins, particularly during transport, transfer, and use. Thus, the resin-wax blend needs to be used immediately or else separation occurs resulting in non-uniformity in the water-repellency and bond quality imparted to the composite by the adhesive. Further, since wood shrinks and swells as its moisture content varies, if the composite is not properly treated with a sizing agent and resin, the composite will have less integrity or debond on exposure to moisture.
Often the wax emulsion is combined with the resin at the time of use. Of course this complicates handling and mixing at the site of use. It would be much more convenient to provide the user with a ready-to-use adhesive that requires no mixing prior to application.
U.S. Pat. No. 4,407,999 attempts to provide a single component, ready-to-use (RTU), water repellant adhesive composition for wooden material, purportedly having good blendability and storage stability. The adhesive consists essentially of a paraffin emulsion containing oxidized paraffin and a resin such as a phenolic resole resin. This patent suggests that by using an oxidized paraffin having an acid value of from 10 to 70 and a melting point of from 30 to 90.degree. C., with the conventional paraffin wax component, one can successfully prepare a pre-blended adhesive from the resin and wax emulsion. Too low an acid value makes emulsification of the wax difficult; too high a value reduces the water resistance of the composite. The wax emulsion is prepared in the presence of a surfactant and/or a water-soluble alkali metal compound such as sodium hydroxide. Blending of wax emulsion and resin is carried out from ambient temperature to 60.degree. C.


SUMMARY OF THE INVENTION

Applicants have discovered that adjusting the pH of the wax emulsion to closely match that of the resin and heating the resin prior to addition of the wax emulsion greatly improved resin/wax compatibility and handling. Applicants further discovered that the resultant resin/wax adhesive blend provided composites having unexpectedly improved thickness swell and water absorption properties over composites made with prior art technology, i.e. resin-wax blends not treated with the combination of pH adjustment and heating. The adhesive also provided good storage life and low odor. The resin/wax emulsion adhesive of the present invention eliminates the need to handle multiple raw materials at the site of use.
The present invention is directed to a composite prepared by combining a furnish and a ready-to-use, single package, adhesive composition. The adhesive composition comprises a combination of a thermosetting resin and a wax emulsion prepared by: 40.degree. C., wherein the resin has a pH of about 9 to 12; resin; and the temperature of the resin above 40.degree. C.


BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1, 2, and 3 depict data from a strand board study using the RTU resin/wax system of the present invention.
FIG. 1 shows Internal Bond strength results.
FIG. 2 shows % Thickness Swell performance.
FIG. 3 show

REFERENCES:
patent: 2682516 (1954-06-01), Wilder et al.
patent: 3443986 (1969-05-01), Watanabe et al.
patent: 4361612 (1982-11-01), Shaner et al.
patent: 4407999 (1983-10-01), Fushiki et al.
patent: 4439575 (1984-03-01), Schwarz
patent: 4758478 (1988-07-01), Daisy et al.
patent: 5047275 (1991-09-01), Chiu

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