Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1982-09-20
1983-10-25
Cockeram, H. S.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521155, 521170, 528 57, 528 75, C08G 1814, C08G 1822
Patent
active
044120133
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to expandable urethane compositions adapted for use as sealants in, for example, automotive industry applications requiring the sealing of various body panels or joints. More particularly, this invention relates to two-component expandable urethane sealant compositions which cure by chemical reaction between a first component comprising a mixture of hydroxy functional liquid elastomers and metal salts of an organic sulfonate and a second component comprising polyisocyanate.
BACKGROUND ART
Modern sealants are comprised of pigmented or unpigmented synthetic elastomeric polymers, which, in the non-cured state, constitute pourable or easily extrudable putty-like mastics. When cured, they are transformed into elastomeric materials which seal these structural elements and are able to contract or expand with the motion of the connected elements. They also form a tight barrier against moisture, gases and chemicals.
Such sealants include one-component and two-component compositions whose curing may proceed according to several mechanisms. One type of sealant, urethane sealants, include one-component compositions containing only isocyanate terminated prepolymers that cure by reaction of mixtures and isocyanate to form urea linkages. Two-component urethane sealants are prepared from isocyanate-terminated prepolymers and compounds containing active hydrogens both of which are generally sufficiently fluid to be blended at room temperature. These two component sealants cure by the formation of urethane linkages. Urethane polymers are good candidates for sealant applications because they possess a number of desirable properties including outstanding abrasion resistance, oil resistance, low temperature flexibility, resistance to degradation, excellent elasticity and, consequently, a high recovery. Because of an almost unlimited diversity of raw materials, polyurethanes can be formulated with excellent physical properties including low modulus, with retention of good tear and tensile strength.
Recently sealants which expand when heated have become available. These foam sealants, because they are able to expand to effectively seal a joint, are particularly useful as sealants for irregularly shaped or poorly fitting joints. Flexible urethane foams are generally prepared by incorporating water into the urethane composition. The reaction of the water and the isocyanate generates carbon dioxide which acts as a blowing agent to generate the foam. Alternately, fluorocarbons such as trichlorofluoromethane or other volatile solvents have been incorporated into polyurethane compositions as blowing agents to form flexible foams.
DISCLOSURE OF INVENTION
A novel composition has now been found to generate expandable urethane sealants without the use of water or volatile solvents as blowing agents therein. Such compositions have been found particularly useful as automotive sealants for sealing various body parts. The invention of the subject application is directed to a two-component expandable urethane sealant compositions comprising reactive elastomer and polyisocyanate, characterized in that these compositions comprise a first component mixture comprising liquid reactive elastomer and metal salts of an organic sulfonate and a second component comprising polyisocyanate.
The liquid reactive elastomer (a) has a number average molecular weight (M.sub.n) of between about 1500 and 15,000, (b) contains pendant hydroxyl groups, and (c) is liquid at between about 20.degree. C. and 25.degree. C. The metal salt of organic sulfonates have the formula: ##STR1## wherein R is selected from C.sub.8 -C.sub.36 hydrocarbon groups and M is a metal ion wherein n=1, 2 or 3. The elastomer and the metal salts of organic sulfonates are present in the mixture in amounts so as to provide between about 20 and about 80 percent hydroxyl groups and between about 80 and about 20 percent sulfonate groups, based on the total of these hydroxyl groups and sulfonate groups. Preferably, the sulfonate is employed dispersed in n
REFERENCES:
patent: 3433752 (1969-03-01), Zagoreu et al.
patent: 4073841 (1978-02-01), Dultgen et al.
patent: 4145302 (1979-03-01), Doan
patent: 4146687 (1979-03-01), Reale
patent: 4263408 (1981-04-01), Meyborg et al.
Cockeram H. S.
Ford Motor Company
May Roger L.
Melotik Lorraine S.
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