Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
1998-10-01
2001-08-21
Hoke, Veronica P. (Department: 1714)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C524S415000, C524S417000
Reexamination Certificate
active
06277482
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to novel, improved materials which exhibit a combination of adhesive and fire retarding properties and to the use of such materials.
BACKGROUND OF THE INVENTION
A variety of products including chipboards and oriented strand boards are composed of adhesively-bonded pieces of wood and other flammable materials. The adhesives currently used in the manufacture of such products do nothing to reduce the flammability of the products. Adhesives with fire retarding properties would be desirable, particularly because the adhesive intimately coats the particles of the product substrate and would accordingly decrease significantly the fire hazards posed by such products.
SUMMARY OF THE INVENTION
Adhesives which are effective fire retardants have now been conceived and are disclosed herein. These novel fire retarding adhesives supply nitrogen and phosphorous for fire retardancy. They are composed of an A resin and a B resin, each made from constituents which form polymers when the pH and/or temperature of the reaction mass is adjusted to an appropriate value. Both resins also contain effective amounts of fire retarding nitrogen and/or phosphorus.
The adhesives disclosed herein are effective and durable, can be employed outdoors as well as inside, and can also be employed as fire retardant coatings.
The objects, advantages, and features of the present invention will be apparent to the reader from the foregoing, the appended claims, and the ensuing detailed description and discussion of the invention.
DETAILED DESCRIPTION OF THE INVENTION
As discussed above, the novel adhesives of the present invention contain nitrogen and phosphorous in a form which makes the adhesives effective fire retardants. Structurally, these adhesives are mixtures of thermosettable resins obtained by reacting A Resin and B resin constituents of particular character. The weight ratio of A Resin to B Resin in the adhesive prepared from those resins may range from 3:1 to 1.5:1 depending on the application for which the adhesive is destined.
Mole ratio combinations of A and B may be varied to provide for specific adhesive qualities. Resin A must be greater in proportion than Resin B in order to provide for adequate fire retardancy in the adhesive.
Resin A and Resin B can be combined to form a copolymer as soon as both resins are on hand because the combined and slightly reacted resins have a more than adequate shelf life. Combining the resins ahead of the time of use: allows the manufacturer to control mixing and reactions of the A and B resins for optimum performance of the adhesive and relieves the user/product fabricator of the adhesive of this step. Combining Resin A and Resin B at an earlier point in time also has the advantage that the bulk of the material that has to be stored is considerably reduced and that the number of items in inventory can be halved.
The bulk of the polymerization reactions effected in preparing the adhesive take place in Resin A and Resin B with there being only slight reactions to form a copolymer between the Resin A and Resin B constituents. This may be accomplished at a moderately elevated temperature—for example, 50-70 degrees C.—with the mixture of resins held at that temperature for a few—for example 5-10—minutes to ensure that the mixture copolymerizes.
Formulations for the A and B resins follow.
Ingredient
Amount (w/w %)
A Resin
(1)
Melamine, urea, and/or phenol
5-18
(2)
Phosphorus source
(3)
Glyoxal or additional aldehyde
(4)
Formaldehyde
2-8
(5)
Water
Balance
B Resin
(6)
Formaldehyde
9-34
(7)
Melamine, urea, and/or phenol
5-18
(8)
Lower alkyl alcohol
10-40
(9)
Phosphorus Source
(10)
Glyoxal or additional aldehyde
(11)
pH Modifier
0.1-0.3
What is characterized in the foregoing formulations as “additional aldehyde can be acetaldehyde, or any other appropriate aldehyde; and the formaldehyde in both the A and B resins can be in whole or in part be replaced with another aldehyde. In any event the amounts (3) plus (10) in both formulations are preferably limited to the range of 2-18 percent.
Phosphorous is a fire retardant and the sources of that element ((2) plus (9)) are employed in amounts providing from 5 to 18 percent, calculated as elemental phosphorous and based on the weight of the adhesive (Resin A plus Resin B). The phosphorus is split between Resin A and Resin B. To resist leaching, the phosphorus must be chemically bound to the melamine or its equivalent. All of the phosphorous needed for fire retardancy cannot be tied up in Resin A, which dictates that chemically bound phosphorous also must be present in Resin B.
The melamine (or above-listed alternatives) and aldehydes condense into thermosettable polymers with adhesive properties. Urea and melamine have the additional, significant advantage of providing fire retarding nitrogen. Phenol and melamine are preferred in B resins destined for use out of doors as these compositions provide more resistance to moisture than urea.
Glyoxal is employed in the A Resin to promote the solubility in the water of the remaining A Resin constituents. The preferred alcohol in the B Resin is methanol. This B Resin constituent increases the shelf life of the A Resin/B Resin adhesive and increases the ability of the adhesive to penetrate into the pores of the material to which it is applied, thereby creating a strong bond between the elements being joined.
The methanol (or other lower alkyl alcohol) may be provided as a separate constituent and/or as an ingredient of the formaldehyde component. The alcohol is provided to cap the resin copolymers which increases the shelf life of the adhesive. Upon curing the adhesive the blocking effect of the alcohol is eliminated, which allows the polymerization reactions to proceed to the point where the adhesive becomes a thermoset, solid, insoluble material.
One phosphorous source that can be employed to advantage, especially in the A resin, is phosphoric acid. This acid can be used to control the pH of the reaction mass and, consequentially, the fire retardancy and other characteristics of the A Resin and the adhesive prepared from that resin. Nevertheless, the use of this acid is not essential. Other acids such as hydrochloric and sulfuric can be used as pH modifiers. This acid reacts with the melamine to form melamine phosphate which reacts with glyoxol to allow the melamine phosphate to be soluble in water.
pH control in the manufacture of both the A Resin and the B Resin is important from the viewpoints of fire retardancy and the service life of the equipment in which the A and B resins are manufactured. B Resins are generally formulated to provide a pH of 1-12 depending on the use to which the Resin A/Resin B combination is to be put. The pH of the A Resin is always on the acid side to provide adequate fire retardancy. The pH of the A resin is preferably in the range of 0.5-6.5. A pH approaching neutral has the advantage of minimizing corrosion of the equipment in which the resin is manufactured with acid pH's tending to promote fire retardancy. In the acidic pH environment the cellulose of a substrate such as wood dehydrates. As a result, the surface of the wood chars when the wood is heated to ignition temperature instead of burning freely. The char acts as an insulator, thus providing additional fire retardancy to the substrate.
As suggested above, fire retarding adhesives embodying the principles of the present invention can be advantageously employed in the manufacture of chipboards, strand boards, and other wood products. Woods such as cedar and Douglas fir have an acidic pH (4-4.5), and an adhesive having an A Resin component on the acidic side is preferably used to bond the elements of these products. Hemlock, as one example, has a neutral pH; and more nearly neutral A Resins may be used in adhesives intended for manufacturing products from that wood. In any event, it is important to match the pH of the adhesive to the material being bonded to minimize degradation of the wood.
That the adhesive can be manufa
Amundson Fred J.
Trocino Frank S.
Hoke Veronica P.
Miller Nash LLP
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