| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | May 4, 1999 |
| PATENT TITLE |
Curable composition based on oxypropylene polymer |
| PATENT ABSTRACT | A curable composition is disclosed and comprises the following components. (A) 100 parts by weight of a oxypropylene polymer having a polymer main chain containing a repeating unit represented by the following formula ##STR1## and having at least one group containing a silicon atom bonded to a hydroxyl group and/or a hydrolyzable group and capable of crosslinking by forming a siloxane bond, wherein Mw/Mn thereof is not more than 1.6 and the number average molecular weight is at least 6,000, (B) from 1 to 200 parts by weight of a filler having a BET specific surface area of not higher than 10 m.sup.2 /g, and (C) from 0.1 to 20 parts by weight of a curing catalyst, said composition containing substantially no plasticizer. |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | September 5, 1995 |
| PATENT FOREIGN APPLICATION PRIORITY DATA | This data is not available for free |
| PATENT REFERENCES CITED | Machine Design, vol. 52, No. 13, Jun. 1980, Cleveland Ohio, USA, pp. 113-116 Database WPIL, Derwent Publications Ltd., London, GB; AN 90-213243 (28). |
| PATENT PARENT CASE TEXT | This data is not available for free |
| PATENT CLAIMS |
What is claimed is: 1. A curable composition comprising (A) 100 parts by weight of a liquid oxypropylene polymer having a polymer main chain containing a repeating unit represented by the following formula ##STR7## and having at least one group containing a silicon atom bonded to a hydroxyl group and/or a hydrolyzable group and capable of crosslinking by forming a siloxane bond, wherein Mw/Mn of the liquid oxypropylene polymer is not more than 1.6 and its number average molecular weight is from 6,000 to 60,000, (B) from 1 to 200 parts by weight of a filler having a BET specific surface area of not higher than 10 m2/g, and (C) from 0.1 to 20 parts by weight of a curing catalyst, said composition containing substantially no plasticizer. 2. The curable composition of claim 1, wherein said group having a silicon atom bonded to a hydroxyl group and/or a hydrolyzable group is a group represented by the following formula (I) ##STR8## wherein R.sup.1 and R.sup.2 each represents an alkyl group having from 1 to 20 carbon atoms, an aryl group having from 6 to 20 carbon atoms, an aralkyl group having from 7 to 20 carbon atoms, or a triorganosiloxy group represented by (R').sub.3 SiO-- (wherein R' represents a univalent hydrocarbon group having from 1 to 20 carbon atoms and the three R' groups may be the same or different), when two or more R.sup.1 groups and R.sup.2 groups are present, R.sup.1 and R.sup.2 may be the same or different; X represents a hydroxyl group or a hydrolyzable group, and when two or more X groups are present, the X groups may be the same or different; a represents an integer of from 0 to 3; b represents an integer of from 0 to 2, the integers b in the m number of groups shown by the following formula ##STR9## may be the same or different; and m represents an integer of from 0 to 19, said m satisfying the relationship a+.SIGMA.b.ltoreq.1. 3. The curable composition of claim 1, wherein said group having a silicon atom bonded to a hydroxyl group and/or a hydrolyzable group and capable of crosslinking by forming a siloxane bond is a group represented by the following formula ##STR10## wherein R.sup.2, X, and a have the same respective meanings as ascribed in claim 2. 4. The curable composition of claim 1, wherein said group having a silicon atom bonded to a hydroxyl group and/or a hydrolyzable group and capable of crosslinking by forming a siloxane bond are present at the terminal position of the molecular chain of the polymer. 5. The curable composition of claim 1, wherein Mw/Mn of the polymer as component (A) is not more than 1.5. 6. The curable composition of claim 1, wherein Mw/Mn of the polymer as component (A) is not more than 1.4. 7. The curable composition of claim 1, wherein the BET specific surface area of the filler is not higher than 5 m2 /g. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
FIELD OF THE INVENTION The present invention relates to a curable composition comprising a oxypropylene polymer having a group containing a silicon atom bonded to a hydroxyl group and/or a hydrolyzable group and capable of crosslinking by forming a siloxane bond. BACKGROUND OF THE INVENTION Oxyalkylene series polymers each having a reactive silicon group are disclosed in JP-A-52-73998 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), U.S. Pat. No. 3,971,751, etc., and a typical example thereof is a polymer represented by the following formula; X".sub.3 Si(oxypropylene polymer)SiX".sub.3 wherein X" represents a hydrolyzable group such as a methoxy group, etc. A oxyalkylene series polymer having a reactive silicon groups cures by forming a siloxane bond (Si--O--Si) between the polymer molecules by function of moisture in air at room temperature to obtain a rubbery cured material. Since the cured products exhibit excellent elongation properties, strength, adhesion, etc., the material is used as a sealant, adhesives, so on. The polymer may be used in a form of a composition by mixing with a filler to save material cost. The composition, however, is liable to substantially increase in viscosity, accordingly, a plasticizer is technically essential to be incorporated into the composition. On the other hand, use of the plasticizer has various problems due to evaporation and shifting the material. For instances, the problems include softening of the composition due to shifting the material to the substrate, causing cracks of the products, softening of a paint when the paint is coated over the products, contamination of the products due to adhesion, and also lowering of the adhesive property and the flexibility of coating with the passage of time, etc. SUMMARY OF THE INVENTION According to the present invention, there is provided a substantially plasticizer-free curable composition comprising; (A) a oxypropylene polymer having a polymer main chain containing a repeating unit represented by the formula; ##STR2## and at least one reactive silicon group,wherein Mw/Mn is not more than 1.6 and a number average molecular weight is at least 6,000. (B) a filler having a BET specific surface area of not more than 10 m.sup.2 /g , and (C) a curing catalyst. DETAILED DESCRIPTION OF THE INVENTION The present invention is described in detail as follows. There is no particular restriction on the reactive silicon group contained in the oxypropylene polymer (A) but typical examples are the groups represented by following formula (I); ##STR3## wherein, R.sup.1 and R.sup.2 each represents an alkyl group having from 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aralkyl group having from 7 to 20 carbon atoms, or a triorganosiloxy group represented by (R').sub.3 SiO--(wherein R' represents a monovalent hydrocarbon group having from 1 to 20 carbon atoms and three R's may be the same or different), when two or more said R.sup.1 and R.sup.2 exist, they may be the same or different; X represents a hydroxy group or a hydrolyzable group, and when two or more Xs exist, they may be the same or different; "a" represents an integer of from 0 to 3; and "b" represents an integer of from 0 to 2; "b"s in the "m" groups ##STR4## may be the same or different; "m" represents an integer of from 0 to 19, and "a" and "b" satisfy the relationship a+.SIGMA.b.gtoreq.1. There is no particular restriction on the hydrolyzable group, represented by X, and conventionally known hydrolyzable groups can be used in this invention. Specific examples thereof are a hydrogen atom, a halogen atom, an alkoxyl group, an acyloxy group, a ketoxymate group, an amino group, an amido group, an acid amido group, an aminoxy group, a mercapto group, and an alkenyloxy group. In these groups, a hydrogen atom, an alkoxy group, an acyloxy group, a ketoxymate group, an amino group, an amido group, an aminoxy group, a mercapto group, and an alkenyloxy group are preferable, and also from the view point that the hydrolysis is moderate and hence the compound can be easily handled, alkoxy groups such as methoxy, etc., are particularly preferable. One to three of the hydrolyzable groups or hydroxy groups may bond to one silicon atom and (a+.SIGMA.b) is preferably from 1 to 5. When two or more hydrolyzable groups or hydroxy groups exist in the reactive silicon group, they may be the same or different. The number of silicon atom(s) existing in the reactive silicon group may be 1 or 2 or more and in the case of the reactive silicon group to which silicon atoms are bonded by siloxane bonds, etc., about 20 silicon atoms may exist. In addition, the reactive silicon group represented by the following formula is preferable from the point of easy availability; ##STR5## Wherein R.sup.2, X, and a have the same meaning as described above. Also, typical examples of R.sup.1 and R.sup.2 in formula (I) described above are an alkyl group such as methyl, ethyl, etc., a cycloalkyl group such as cyclohexyl, etc., an aryl group such as phenyl, etc., an aralkyl group such a benzyl etc., and a triorganosiloxy group shown by (R').sub.3 SiO--, wherein R' is methyl, phenyl, etc. R.sup.1, R.sup.2, and R' are particularly preferably a methyl group. It is preferable that at least one, and preferably from 1.1 to 5 reactive silicon groups exist in one molecule of the oxypropylene polymer. If a number of the reactive silicon group contained in one molecule of the polymer is less than 1, a curability of the curable composition becomes insufficient and a good rubbery elastic behavior is difficult to obtain. The reactive silicon group(s) may exist at the terminal(s) of the molecular chain of the oxypropylene polymer or may exist in the inside thereof. When the reactive silicon group exists at the terminal position of the molecular chain, an amount of the effective network chains of the oxypropylene polymer component contained in the cured product finally formed is increased, whereby a rubbery cured product showing a high strength, a high elongation, and a low elasticity is obtained. The oxypropylene polymer constituting the polymer main chain in component (A) for use in the present invention has the repeating unit shown by the following formula; ##STR6## These oxypropylene polymers may be straight chain ones or branched ones, or may be a mixture of the straight chain one and the branched one. Also, the oxypropylene polymer may contain other monomer units but in this case, it is preferred that the monomer unit (the repeating unit) shown by the above formula exists in the polymer in an amount of at least 50% by weight, and more preferably at least 80% by weight. It is preferable that the reactive silicon group-containing oxypropylene polymer having Mw/Mn of not higher than 1.6 and a number average molecular weight of at least 6,000 used as component (A) in the present invention is obtained by introducing the reactive silicon group(s) into a oxypropylene polymer. The oxypropylene polymer having a functional group, which is used for the foregoing purpose can be obtained by ring-opening-polymerization of a corresponding propylene oxide. As a method of polymerizing propylene oxide, there are; (a) a method of using an alkali catalyst such as sodium hydroxide, potassium hydroxide, sodium alkoxide, potassium alkoxide, etc., (b) a method of using a metal catalyst such as an aluminum porphiline complex, composite metals, a cyanide complex, etc. Furthermore, the oxypropylene polymer can be also obtained by; (c) a method of reacting a oxypropylene polymer once obtained by a polymerization and a compound having two or more functional groups capable of reacting the terminal group(s) of the oxypropylene polymer. In the foregoing methods, by the method (a), a oxypropylene polymer having a large molecular weight is not obtained, furthermore, a oxypropylene polymer having a large molecular weight obtained by the method (c) is disadvantageous since there is a tendency of broadening the molecular weight distribution, and hence the method (b) is advantageous. In addition, since by the introduction of the reactive silicon groups into the oxypropylene polymer, the molecular weight distribution tends to become broader than the polymer before the introduction of the reactive silicon groups, the molecular weight distribution of the polymer before the introduction of the reactive silicon groups is preferably as narrow as possible. The reactive silicon groups may be introduced by a known method. There are, for example, the following methods. (1) A oxypropylene polymer having functional groups such as a hydroxy group, etc., at the terminal position is reacted with an organic compound having an active group showing a reactivity to the functional group and an unsaturated group, and then the reaction product is hydrosilylated by acting therewith a hydrosilane having a hydrolyzable group. (2) A oxypropylene polymer having functional groups (hereinafter, is referred to as Y functional group) such as a hydroxyl group, an epoxy group, an isocyanate group, etc., at the terminal group is reacted with a compound having a functional group (hereinafter, is referred to as Y' functional group) showing a reactivity to the Y functional group and a reactive silicon group. Specific examples of the silicon compound having the Y' functional groups are an amino group-containing silanes such as .gamma.-(2-aminoethyl)aminopropyltrimethoxysilane, .gamma.-(2-amino-ethyl)aminopropylmethyldimethoxysilane, .gamma.-aminopropyl-triethoxysilane, etc.; mercapto group-containing silanes such as .gamma.-mercaptopropyltrimethoxysilane, .gamma.-mercaptopropylmethyl-dimethoxysilane, etc.; epoxy silanes such as .gamma.-glycidoxypropyltrimethoxysilane, .beta.-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, etc.; vinyl type unsaturated group-containing silanes such as vinyltriethoxysilane, .gamma.-methacryloyloxypropyltrimethoxysilane, .gamma.-acryloyloxypropylmethyldimethoxysilane, etc; chlorine atom-containing silanes such as .gamma.-chloropropyltrimethoxysilane, etc.; isocyanate-obtaining silane such as .gamma.-isocyanatopropyltriethoxysilane, .gamma.-isocyanatopropylmethyldimethoxysilane, etc.; and hydrosilanes such as methyldimethoxysilane, trimethoxysilane, methyldiethoxysilane, etc., although the silicon compounds having the Y' functional groups for use in this invention are not limited to these compounds. In the foregoing method (1) or (2), the method of reacting a oxypropylene polymer having a hydroxy group at the terminal position and a compound having an isocyanate group and a reactive silicon group is preferred from the view point of ease of the synthesis. The number average molecular weight (Mn) of the reactive silicon-containing oxypropylene polymer, which is component (A) of the curable composition of the present invention is effectively at least 6,000, preferably from 6,000 to 60,000, and more preferably from 7,000 to 30,000. Such oxypropylene polymers are described in JP-B-3-79627, etc., (the term "JP-B" as used herein means an "examined published Japanese patent publication"). Furthermore, in the foregoing reactive silicon-containing oxypropylene polymer, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is not higher than 1.6 and thus the molecular weight distribution is very narrow (the monomer has mono-dispersibility). The value of (Mw/Mn) is preferably not higher than 1.5, and more preferably not higher than 1.4. In addition, the molecular weight distribution can be measured by various methods but is usually measured by a gel permeation chromatographic (GPC) method. As described above, since the oxypropylene polymer being used in the present invention has a narrow molecular weight distribution in spite of the large number average molecular weight, the composition containing the polymer shows a good viscosity behavior, shows excellent processing property and workability in spite of containing substantially no plasticizer, and does not show various faults based on a plasticizer. A filler being used as component (B) in the present invention is not limited to specific fillers and ordinary fillers can be used. Practical examples thereof are reinforcing fillers such as fumed silica, precipitated silica, silicic anhydride, silicic hydrate, carbon black, etc.; fillers such as calcium carbonate, magnesium carbonate, diatomaceous earth, calcined clay, clay, talc, titanium oxide,bentonite, organic bentonite, ferric oxide, zinc oxide, activated zinc white, and organic fillers (e.g., hydrogenated castor oil, polyvinyl chloride, and polyolefin); fibrous fillers such as asbestos, glass fibers, glass filaments, etc.; and inorganic and organic hollow microspheres, such as Sirasu (one kind of volcanic ashes) hollow microspheres, glass hollow microspheres, Saran hollow microspheres, phenol hollow microspheres, etc. Fillers may be used singly or as a mixture thereof. Also, the filler for use in the present invention is not limited to the foregoing specific fillers and may be selected according to the desired characteristics of the curable composition of the present invention. However, in general, it is preferred to use at least one kind of a filler having a BET specific surface area of not more than 10 m.sup.2 /g, and preferably not more than 5 m.sup.2 /g from the points of improving the mechanical characteristics and of the viscosity. From the above-described view points and also the points of cost and the easy availability, preferred fillers are calcium carbonate, a vinyl chloride(paste) resin, hollow microspheres. It is preferable that the filler is used in an amount of from 1 to 200 parts by weight (hereinafter, is referred to as simply "parts"), and particularly from 5 to 200 parts to 100 parts of the reactive silicon-containing oxypropylene polymer. Also, as described above, it is preferable to use at least one kind of a filler having a BET specific surface area of not more than 10 m.sup.2 /g. In the case of using fillers, it is preferable that the filler having a BET specific surface area of not more than 10 m.sup.2 /g exists in an amount of at least 10% by weight of the whole fillers. The BET specific surface area is the surface area calculated by a BET method. There is no particular restriction on the curing catalyst used as component (C) of the curable component of the present invention and practical examples thereof are silanol condensation catalysts, e.g., titanic acid esters such as tetrabutyl titanate, tetrapropyl titanate, etc.; tin carboxylates such as dibutyltin dilaurate, dibutyltin maleate, dibutyltin diacetate, tin octylate, tin naphthenate, etc.; the reaction products of dibutyltin oxide and phthalic acid esters; dibutyltin diacetylacetate; organic aluminum compounds such as aluminum trisacetylacetonate, aluminum trisethylacetoacetate, diisopropoxyaluminum ethylacetoacetate, etc.; chelate compounds such as zirconium tetraacetylacetonate, titanium tetraacetylacetonate, etc.; lead octylate; amine series compounds such as butylamine, octylamine, laurylamine, dibutylamine, monoethanolanine, diethanolamine, triethanol-amine, diethylenetriamine, triethylenetetramine, oleylamine, cyclohexylamine, benzylamine, diethylaminopropylamine, xylenediamine, triethyleneamine, guanidine, diphenyl-guanidine, 2,4,6-tris(dimethylaminomethyl)phenol, morpholine, N-methylmorpholine, 2-ethyl-4-methyl imidazole, 1,8-diazabicyclo(5,4,O)undecene-7 (DBU), etc.; the salts of these amine series compounds and carboxylic acids, etc.; low molecular weight polyamide resins obtained from excessive polyamine and polybasic acids; reaction products of excessive polyamine and epoxy compounds; and silane coupling agents having an amino group, such as .gamma.-aminopropyltrimethoxysilabe, N-(B-aminoethyl)aminopropylmethyl dimethoxysilane, etc.; and known silanol condensation catalysts such as other acidic catalysts, basic catalysts, etc. These catalysts may be used singly or as a mixture. The amount of the curing catalyst is preferably from about 0.1 to 20 parts, and more preferably from about 1 to 10 parts to 100 parts of the reactive silicon group-containing oxypropylene polymer. If the amount of the curing catalyst is too small relative to the reactive silicon group-containing oxypropylene polymer, the curing speed is delayed and also the curing reaction is impeded, which are undesirable. On the other hand, if the amount of the curing catalyst is too large relative to the reactive silicon group-containing oxypropylene polymer, local heating and foaming occur at hardening, whereby a good cured product is difficult to obtain, which is also undesirable. In the case of using the curable composition of the present invention, if necessary, various kinds of additives such as an adhesion improving agent, a property controlling agent, a storage stability improving agent, an aging inhibitor, a ultraviolet absorbent, a metal inactivating agent, an ozone deterioration inhibitor, a light stabilizer, an amine series radical chain inhibitor, a phosphorus series peroxide decomposing agent, a lubricant, a pigment, a foaming agent, etc., can be properly added to the polymer. There is no particular restriction on the preparation method of the curable composition of the present invention and, for example, an ordinary method comprises compounding the foregoing components and kneading the compounded mixture at room temperature or under heating using a mixer, rolls, a kneader, etc., or dissolving the foregoing components in a small amount of a solvent and mixing them. Also, by suitably combining these components they can be used as one part type or two part type compounds. When the curable composition of the present invention is exposed in the air, the composition forms a three-dimensional network structure by the action of moisture and is cured into a solid having a rubbery elasticity. The curable composition of the present invention is particularly useful as an elastic sealant and can be used as a sealant for buildings, ships, motor cars, roads, etc. The curable composition of this invention can adhere closely to wide range of substrates, such as glasses, porcelains, woods, metals, resin moldings, etc., or to such primed substrates. Moreover, the curable composition of this invention is also useful as tackifiers, coating compositions, coating water-proofing agents, food packing materials, casting rubber materials, molding materials, foaming materials, etc. As described above, according to the present invention, a curable composition is capable of overcoming various difficulties based on a plasticizer. |
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