Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Patent
1996-08-19
1998-05-05
Sergent, Rabon
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
525452, 525453, 525454, 525457, 525460, 528 27, 528 28, 528 48, 528 52, 528 55, 528 69, 528 73, C08G 1816, C08G 1822, C08G 1832, C08G 1838
Patent
active
057476276
DESCRIPTION:
BRIEF SUMMARY
This invention relates to room temperature curing polyurethane compositions useful as polyurethane resin-based adhesives, coatings, sealants, primers and the like.
Polyurethane is curable with moisture at room temperature and has excellent properties including resiliency and adhesiveness such that may find effective use as sealants, water-proofing agents, adhesives and the like. Polyurethane-based sealants are classified into one-pack and two-pack types of formulation. A two-pack sealant needs to be admixed uniformly with a curing agent prior to use, which advantageously would require a relatively short length of time but would be somewhat tedious as it is done at the site of application. Whereas, a one-pack type of sealant can dispense with prior mixing with other components and is easy to handle, thus leading to increased demand.
One-pack polyurethane compositions are primarily moisture-curable and curable with moisture in the air or moisture adsorbed to a blended compound. Such crosslinking curing progresses from the surface toward the interior of the composition with the results that it will take prolonged length of time before the composition is completely cured. Thus, one-pack compositions compared to two-pack counterparts are less curable and have the problem of storage stability due to initiation of curing upon reaction with moisture in the air or moisture adsorbed to their components.
Known as moisture curing potential agents are oxazolidine, ketimine, enamine and thiosilyl compounds, of which oxazolidine compounds are particularly preferred in terms of balanced curing ability and storage stability as well as satisfactory quality of their cured products. (Japanese Patent Publication No. 55-35407, No. 58-5913 and No. 58-5914). Attempts have been made to control the rate of ring opening (activation) of the oxazolidine ring by changing the 2-position carbon substituents.
Japanese Laid-Open Patent Publication No. 2-55715 discloses a one-pack urethane composition comprising an isocyanate prepolymer added with an oxazolidine compound having two oxazolidine rings and an aromatic polyfunctional isocyanate. This composition is disclosed to be good in respect of storage stability, but is not in fact good enough.
Acids such as 2-ethylhexane are known for accelerating the opening of the oxazolidine ring, but such acids in the preparation of one-pack urethane compositions tend to react with urethane, leading to reduced storage stability. Such acids in the case of two-pack urethane compositions would react with isocyanate, resulting in foaming. Thus, with urethane prepolymers having isocyanate terminal groups, there remain air bubbles in the resulting cured product which emanate from excessive carbon dioxide gas upon reaction of the isocyanate groups with moisture. This problem may be solved by adding ketimine, aldimine or enamine to the urethane prepolymer as disclosed in Japanese Patent Publication Nos. 62-9155 and 4-27962 and Japanese Laid-Open Disclosure Nos. 4-226522 and 5-8730. The disclosed methods may be highly effective in foam suppression, but have a drawback in that the compositions thereby produced are susceptible to viscosity increase over a prolonged period of storage. To provide enhanced to use hydrogen chloride or tin (IV) or organic compounds of tin and lead, or tertiary amine and like curing catalysts. Hydrogen chloride is malodorous and corrosive to clothing. Tin (IV) compounds are usually very stable in storage.
The present inventors have proposed as in Japanese Laid-Open Disclosure No. 7-138336 to use a urethane composition containing a urethane prepolymer, an oxazolidine compound, a silyl ester compound and a mono-isocyanate compound. This composition is characterized by the use of a monoisocyanate compound to trap moisture in the system, opening-ring oxazolidine compounds or free acids. Monoisocyanates are however not always useful for improvement in storage stability and sometimes liable to gelation.
It is an object of the invention to provide a curable composition containing an oxazolid
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Hosoda Hiroyuki
Ishikawa Kazunori
Kimura Kazushi
Okuhira Hiroyuki
Takeda Toshimitsu
Sergent Rabon
The Yokohama Rubber Co. Ltd.
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