Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-04-21
2002-11-19
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S272000, C525S125000, C525S127000, C525S131000
Reexamination Certificate
active
06482878
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to solvent-free moisture curable one-part hot melt polyurethane adhesive or sealant compositions which are solid at room temperature. In one embodiment, the polyurethane adhesive or sealant composition comprises in percentages by weight (a) from about 20% to about 75% of a urethane prepolymer; (b) from about 1% to about 66% of a reactive, hydroxyl containing, or a nonreactive polymer formed from ethylenically unsaturated monomers; and (c) from about 20% to about 75% of a thermoplastic resin. In another embodiment, the polyurethane adhesive or sealant composition comprises, in percentages by weight of the. polyurethane composition (a) from about 10% to about 90% of a urethane prepolymer; and (b) from about 5% to about 90% of a thermoplastic resin which is an ethylene vinylacetate/ethylene acrylate terpolymer.
BACKGROUND OF THE INVENTION
Hot melt adhesives are 100% solid materials which do not contain or require any solvents and are solid at room temperature. On application of heat, the hot melt adhesive melts to a liquid or fluid state in which form it is applied to a substrate. On cooling, the hot melt adhesive regains its solid form, cures by a chemical crosslinking reaction, and thereby gains its cohesive strength. Hot melt adhesives have been prepared using specific materials such as polyurethanes.
Reactive hot melts are one-component, 100% solid, solvent-free urethane prepolymers. Unlike conventional hot melts that can be repeatedly heated from solid state and flowed to a liquid form, the reactive hot melt behaves as a thermoset and goes through an irreversible chemical reaction once dispensed in the presence of ambient moisture. The reactive hot melts are isocyanate terminated prepolymers that react with surface or ambient moisture in order to chain-extend, forming a new polyurethane polymer which offers performance superior to that obtained with conventional hot melt.
U.S. Pat. No. 3,931,077 (Uchigaki et al.) discloses a reactive hot melt-type adhesive composition comprising a reactive compound, a thermoplastic resin, and a tackifier. The reactive compound is a urethane prepolymer having terminal isocyanate groups at both ends resulting from the addition polymerization of a diisocyanate and a diol. The thermoplastic resin is an ethylene-vinylacetate co-polymer, an ethylene-acrylic acid copolymer, an ethyleneacrylate copolymer, an atactic polypropylene, or a polyethyleneterephthalate linear polymer. The tackifier is a hydrogenated abietic acid-type rosin or ester having its double bonds removed by hydrogenation in whole or in part, or a terpene-phenol copolymer of a mono- or diterpene.
U.S Pat. No. 4,585,819 (Reischle et al.) discloses a fusion adhesive which comprises 20-90% by weight isocyanate prepolymer, and 5-50% by weight of a lower molecular weight synthetic resin selected from the group consisting of ketone resins, hydrogenated products of acetophenone, and condensation resins.
U.S. Pat. No. 4,775,719 (Markevka et al.'719) discloses a hot melt thermosetting urethane adhesive composition that can be extruded as a hot melt adhesive to form an initially high green strength hot melt bond and can moisture cure to a rigid moisture cure polyurethane bond. The urethane adhesive composition comprises (a) a film-forming thermoplastic ethylene-vinyl monomer copolymer which is a vinyl monomer of an acrylate monomer or a vinyl ester of a carboxylic acid compound; (b) a liquid polyurethane prepolymer composition; (c) a phenol-free, aromatic or aliphatic-aromatic polymer tackifier comprising a monomer selected from the group consisting of a C
4-6
diene, a styrenic monomer, an indene monomer, and dicyclopentadiene; and (d) an antioxidant.
U.S. Pat. No. 4,808,255 (Markevka et al.'255) discloses a reactive hot melt urethane adhesive composition having extended pot stability, bond heat stability, green strength and cured bond strength. The urethane adhesive composition comprises (a) a urethane prepolymer composition; (b) a structural thermoplastic ethylene vinyl monomer copolymer composition; and (c) a compatible aliphatic, aromatic or aliphatic-aromatic tackifying resin.
U.S. Pat. No. 5,021,507 (Stanley et al.) discloses the incorporation into a conventional polyurethane hot melt adhesive of low molecular weight polymers formed from ethylenically unsaturated monomers containing no reactive hydrogen. The polymers provide an improvement in cohesive and adhesive strength and assist in forming bonds with some of the more difficult to adhere substrates. In order to incorporate the low molecular weight polymer into the polyurethane, the respective monomers are polymerized within the urethane prepolymer or an already polymerized low molecular weight polymer is added into the urethane prepolymer. Typical monomers useful include acrylic monomers such as the C1 to C12 esters of acrylic or methacrylic acid as well as ethylenically unsaturated monomers containing moisture reactive functional groups such as silane or reactive isocyanate. Typical low molecular weight polymers are Elvacite 2013, a 64% butylmethacrylate/36% methylmethacrylate copolymer having an I.V. of 0.2.
U.S. Pat. No. 5,189,096 (Boutillier et al.) discloses a cross-linkable hot-melt adhesive composition comprising the prepolymerizate of an hydroxylated ethylene/vinyl acetate copolymer with a stoichiometric excess of a polyisocyanate. The prepolymerizate contains an effective crosslinkable amount of free isocyanate functional groups.
U.S. Pat. No. 5,506,296 (Chenard et al.) discloses a process for the preparation of a hot-melt adhesive comprising (a) melting and drying an EVA terpolymer comprising from 60 to 90% by ethylene, 10 to 40% vinyl acetate and an ethylenically unsaturated termonomer bearing at least one primary hydroxyl functional group per mole; (b) reacting the EVA terpolymer with a polyisocyanate to form a polyisocyanated EVA terpolymer; and (c) contacting the EVA terpolymer with an alcohol to obtain a moisture-curable hot-melt adhesive having a desired content of free NCO functional groups.
U.S. Pat. No. 5,866,656 (Hung et al.) discloses a solvent-free moisture curable one-part hot melt polyurethane adhesive or sealant composition which is solid at room temperature. The polyurethane composition comprises (a) 10 to 70% by weight of a urethane prepolymer having an isocyanate content of 0.25 to 15% by weight and an isocyanate index greater than 1 and up to about 3; and (b) 30 to 90% by weight of a hydroxyl containing polymer formed from ethylenically unsaturated monomers. The polymer has a number average molecular weight of 4,000 to 15,000. The polymer (b) contains sufficient hydroxyl functionality to provide an OH number of 5 to 15. The hydroxyl functionality is derived from hydroxyl substituted monomers selected from the group consisting of C1 to C12 esters of acrylic and methacrylic acids, vinyl esters, vinyl ethers, fumarates, maleates, styrene, and acrylonitrile.
While the class of adhesives in the above disclosures describe the preparation of a number of adhesive compositions, none of the above disclosures describe methods that are entirely satisfactory for preparing adhesive compositions. None of the above disclosures describe the preparation of a low cost, reactive, hot melt having increased heat and tensile properties. The present invention provides such improved hot melt compositions without the disadvantages characteristic of previously known compositions.
SUMMARY OF THE INVENTION
The present invention pertains to a solvent-free moisture curable one-part hot melt polyurethane adhesive or sealant composition which is solid at room temperature comprising, in percentages by weight of the polyurethane composition:
(a) from about 20% to about 75% of a urethane prepolymer having an isocyanate content from about 0.25% to about 15%, and an isocyanate index greater than 1 and up to about 5;
(b) from about 1% to about 66% of a reactive, hydroxyl containing, or a nonreactive polymer formed from ethylenically unsaturated monomers, the polymer having a number ave
Almer Charles W.
National Starch and Chemical Investment Holding Corporation
Short Patricia A.
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