Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From heterocyclic reactant containing as ring atoms oxygen,...
Reexamination Certificate
2002-08-06
2004-10-12
Peng, Kuo-Liang (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From heterocyclic reactant containing as ring atoms oxygen,...
C556S411000, C525S452000, C524S265000, C524S589000, C528S052000
Reexamination Certificate
active
06803445
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a moisture curable polyurethane and/or epoxy resin composition suitable for use as a joint filling material, sealant or adhesive, or the like, and storage stabilizer to be contained in such a moisture curable polyurethane and/or epoxy resin composition.
2. Description of the Related Art
Isocyanate compounds having two or more isocyanate groups in the molecule form three-dimensional crosslinked structures due to the reaction with curing agents such as amines and polyols to provide polyurethane cured products which are excellent in high strength, high elongation, abrasion resistance, grease resistance, etc. Presence of a repeating unit having an ether skeleton in the main chains of such isocyanate compounds can give rise to flexible cured products. Polyurethane compositions comprising such urethane polymers as main integrants have heretofore found wide use as joint filling materials (joint compound), sealants, adhesives, etc. Such urethane polymers having isocyanate groups react with the moisture in the air and cure with decarboxylation, so that they can serve as one-pack type moisture curable polyurethane resins. Using moisture latent curing agents whose active hydrogen is chemically blocked and unblocked by moisture can not only control the curing but also prevent the foaming of the polyurethane resins.
Needless to say, one-pack type moisture curable polyurethane compositions have considerably improved workability and are more useful than two-pack type polyurethane compositions, of which the main ingredient and the curing agent are mixed at the time of working.
Incidentally, in the case where the moisture curable polyurethane compositions are used in particular as sealants, joint filling materials, etc., the property of good workability without causing sagging, in other words thixotropic properties (slump resistance) are required. The thixotropic properties can usually be improved by blending colloidal silica, etc., in the polyurethane compositions with using calcium carbonate as a filler having smaller surface area.
Calcium carbonate is known to include usually two types, i.e., heavy (having larger particle size about 1 &mgr;m or more than 1 &mgr;m as the mean diameter such as ground calcium carbonate, ground limestone, ground whiting) and light (having smaller particle size about 0.1 &mgr;m or less than 0.1 &mgr;m as the mean diameter such as colloidal calcium carbonate or precipitated calcium carbonate). The heavy calcium carbonate is used in combination with precipitated calcium carbonate such as colloidal silica to provide thixotropic one-pack type moisture curable polyurethane compositions, as described above. On the other hand, general light calcium carbonate is poor in storage stability and not used in one-pack type moisture curable polyurethane compositions due to the difficulty of elimination of water.
For this reason, where the light calcium carbonate, which has a larger surface area, is used in the one-pack type moisture curable polyurethane compositions, it is necessary to surface-treat the above-mentioned calcium carbonate with fatty acid esters (JP 2,652,044 B) or urethane compounds (JP 10-245221 A) in order to attain storage stability. The surface treatment can provide one-pack type moisture curable polyurethane compositions having thixotropic properties. However, using such calcium carbonates do not always give high storage stability. The addition of the above-mentioned colloidal silica has inherent problems that foaming and generation of cracks at the time of curing and too high a modulus of the cured product.
Under the circumstances, the inventors of the present invention have previously proposed blending a polyurethane composition containing calcium carbonated surface-treated with a fatty acid ester with a fatty acid silyl ester (JP 2,719,105 B) or with a polysiloxane having a fatty acid silyl ester group (JP 2,749,763 B) to improve storage stability. In particular, the polyurethane composition blended with the fatty acid silyl ester permit blending light calcium carbonate, so that thixotropic properties and storage stability can be imparted thereto.
On the other hand, in the case of a one-pack type epoxy resin containing a ketimine or an oxazolidine as a latent curing agent, storage stability is a big problem. To cope with this problem, the publication of WO98/31722 discloses the utilization of latent curing agents with steric hindrance. Although these latent curing agents exhibit excellent storage stability, they are not always satisfactory.
SUMMARY OF THE INVENTION
The inventors of the present invention have found that although fatty acid silyl ester groups are effective to both thixotropic properties and storage stability, in some situations they are hydrolyzed to produce free carboxylic acids (fatty acids), that is, since the fatty acid silyl ester groups have higher hydrolyzability than that of an isocyanate group, they are hydrolyzed with the moisture inherently contained in calcium carbonate, etc. used as a filler during its storage, thereby producing free carboxylic acids, which promote the hydrolysis of the latent curing agent, particularly the oxazolidines and the ketimines to decrease the storage stability of the resin compositions.
Therefore, emergence of a storage stabilizer is desired that can provide more improved storage stability of thixotropic moisture curable polyurethane compositions, in particular those containing inorganic fillers than that of the currently used curable polyurethane composition, and a thixotropic moisture curable polyurethane composition containing such a storage stabilizer and capable of providing cured products having not only excellent storage stability but also excellent thixotropic properties, high curing rates at the time of working and excellent mechanical characteristics such as elongation.
Furthermore, also in the case of a one-pack type epoxy resin, the latent curing agent is activated with a carboxylic acid to be released to decrease storage stability, and in addition the epoxy resin is also activated by the carboxylic acid to be released, which is also a cause of decreasing the storage stability. Accordingly, emergence of a storage stabilizer is desired that can provide more improved storage stability of epoxy resin compositions, in particular those containing inorganic fillers than that of the currently used epoxy resin composition, and an one-pack type epoxy resin composition containing the storage stabilizer and capable of providing cured products having not only excellent storage stability but also high curing rates at the time of working and excellent mechanical characteristics.
The above-mentioned object can be solved by the following aspects of the present invention.
Thus, the present invention relates to a storage stabilizer for polyurethanes and/or epoxy resins comprising an N-silylamide compound having a functional group represented by the formula: —CONH—Si≡.
Also, the present invention relates to a storage stabilizer for moisture curable polyurethanes and/or epoxy resins comprising an N-silylamide compound represented by the formula (1):
(R
1
—CONH)
4-n
—Si—R
2
n
(1)
wherein R
1
is a hydrocarbon group having 5 to 21 carbon atoms optionally containing a heteroatom, and R
2
is an alkyl or alkoxy group having 1 to 3 carbon atoms; and n is 0, 1, 2 or 3; provided that R
1
s and R
2
s may be the same or different.
Also, the present invention relates to a moisture curable polyurethane composition comprising (A) a urethane prepolymer having two or more isocyanate groups in the molecule, (B) 1 to 300 parts by weight per 100 parts by weight of the urethane prepolymer (A) of an inorganic filler, (C) 0.5 to 30 parts by weight per 100 parts by weight of the urethane prepolymer (A) of an N-silylamide compound represented by the formula (1), and (E) a moisture latent curing agent.
(R
1
—CONH)
4-n
—Si—R
2
n
(1)
wherein R
1
is a hydrocarbon group having 5 to 21 carbon atoms optionally containi
Hosoda Hiroyuki
Ishikawa Kazunori
Peng Kuo-Liang
The Yokohama Rubber Co. Ltd.
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