Patent Description:
Since reactive silicon groups, especially alkoxysilyl groups are capable of hydrolytic condensation in the presence of water, polymers having reactive silicon groups can be used as curable compositions adapted to crosslink and cure in the presence of moisture or humidity.

Of such polymers, polymers of polyoxyalkylene backbone are generally known as modified silicones, and polymers of silicon-containing compound backbone are generally known as end-capped silicones.

Curable compositions comprising polymers having reactive silicon groups as typified by the foregoing polymers are characterized by being liquid at room temperature and becoming rubber elastomers upon curing. For utilizing these characteristics, they are widely used as coating agents, adhesives, building sealants and the like.

Nowadays, particularly in the applications of adhesives and building sealants, not only a strong bond is simply required, but an improvement in durability and bond of better quality are also required. For example, when the cured adhesive layer becomes a tough and flexible rubber elastomer which can accommodate the thermal expansion and shrinkage of a substrate and external stresses, there are obtained elastic adhesives which are improved in durability and reliability.

A number of proposals were made on the method for preparing polymers having reactive silicon groups at molecular chain ends. Some have been used for industrial manufacture.

For example, as the compound having a polyoxyalkylene group in the backbone and an alkoxysilyl group at molecular chain end, polymers of polyoxypropylene backbone having methyldimethoxysilyl groups bonded at both molecular chain ends are known. As a typical example of such polymers, room temperature curable compositions comprising an alkoxysilyl-end-capped polyoxyalkylene based compound as the main component or base polymer are known from Patent Documents <NUM> and <NUM>.

The room temperature curable compositions of Patent Documents <NUM> and <NUM>, however, have the problem that since crosslinking reaction takes place under the impetus of moisture curing of methyldimethoxysilyl or trimethoxysilyl groups, cured products after moisture curing have a high crosslinking density and are susceptible to cracking or peeling.

On the other hand, when a compound having a dimethylmonomethoxysilyl group is used in combination for the purpose of reducing the crosslinking density, there arises the problem of cure failure because the reactivity of dimethylmonomethoxysilyl group is very low.

Patent Document <NUM> discloses alkoxysilanes (A) that have at least one structural element of general formula [II]:
<CHM>
wherein R<NUM> represents an optionally substituted hydrocarbon group or a =N-CR<NUM><NUM> group, R<NUM> represents an alkyl group having <NUM> to <NUM> carbon atoms or an ω-oxaalkyl-alkyl group having a total of <NUM> to <NUM> carbon atoms, R<NUM> represents hydrogen or an optionally substituted hydrocarbon group, and a may be <NUM>, <NUM>, <NUM> or <NUM>.

Patent Document <NUM> discloses a modified conjugated diene-based polymer and its preparation method. The method comprises a polymerization step to obtain a conjugated diene-based polymer having a reactive end, and a modifying step of reacting a modifier with the reactive end of the conjugated diene-based polymer. One of the modifiers used in Patent Document <NUM> is
<CHM>.

An object of the invention, which has been made under the above-mentioned circumstances, is to provide an organosilicon compound containing a monoalkoxysilyl group and yet having a high reactivity, and a method for preparing the same.

Making extensive investigations to attain the above object, the inventors have found a specific organosilicon compound containing a specific heteroatom-methylene-silyl linkage as a linking group with a monoalkoxysilyl group at a molecular chain end, and a method for preparing the same, and that a composition comprising the organosilicon compound has high reactivity and gives a cured product having excellent flexibility and is suited as a curable composition for forming such materials as coating agents, adhesives and sealants. The invention is predicated on this finding.

The organosilicon compound of the invention contains a monoalkoxysilyl group and yet has a high reactivity. A composition comprising the organosilicon compound gives a cured product having excellent flexibility.

The inventive compound having such properties is advantageously used in such applications as coating agents, adhesives and sealants.

The invention provides an organosilicon compound having the structural formula (<NUM>). On use of such organosilicon compound, the resulting composition has further better shelf stability and the cured product has further better mechanical properties.

In formula (<NUM>), each R<NUM> is independently a C<NUM>-C<NUM> alkyl group or C<NUM>-C<NUM> aryl group, each R<NUM> is independently a C<NUM>-C<NUM> alkyl group or C<NUM>-C<NUM> aryl group, wherein some or all of the hydrogen atoms in R<NUM> and R<NUM> may be substituted by a halogen atom or cyano group, and R<NUM> is an unsubstituted C<NUM>-C<NUM> alkylene group.

Examples of the C<NUM>-C<NUM> alkylene group include straight or branched alkylene groups such as methylene, ethylene, trimethylene, propylene, tetramethylene, isobutylene, dimethylethylene, pentamethylene, <NUM>,<NUM>-dimethyltrimethylene, hexamethylene, heptamethylene and octamethylene, and cycloalkylene groups such as cyclopentylene and cyclohexylene.

The C<NUM>-C<NUM> alkylene group may be a divalent group having a chainlike moiety and a cyclic moiety commonly, as shown by the following formula (i). <CHM>
Herein Me stands for methyl, and * designates a valence bond.

R<NUM> is preferably methylene, ethylene or trimethylene, with ethylene being more preferred from the aspects of reactivity, availability, productivity, and cost.

The C<NUM>-C<NUM> alkyl groups represented by R<NUM> and R<NUM> may be straight, branched or cyclic, and examples thereof include straight or branched alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, t-butyl, n-pentyl, neopentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl, and cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and isobornyl.

Examples of the C<NUM>-C<NUM> aryl group include phenyl, tolyl, xylyl, α-naphthyl, and β-naphthyl.

R<NUM> and R<NUM> are preferably selected from methyl, ethyl, and phenyl, with methyl being most preferred from the aspects of reactivity, availability, productivity, and cost.

The organosilicon compound having formula (<NUM>) of the present invention may be prepared by reacting an amino-containing compound having the structural formula (<NUM>) with monoalkoxysilane II having formula (<NUM>). <CHM>
Herein R<NUM> and R<NUM> are as defined above. R<NUM> is a leaving group selected from among chlorine, bromine, iodine, methansulfonate, trifluoromethanesulfonate, and p-toluenesulfonate, or a (meth)acryloyloxy group. Examples of monoalkoxysilane II having formula (<NUM>) include chloromethyldimethylmethoxysilane, chloromethyldimethylethoxysilane, acryloyloxymethyldimethylmethoxysilane, acryloyloxymethyldimethylethoxysilane, methacryloyloxymethyldimethylmethoxysilane, and methacryloyloxymethyldimethylethoxysilane. <CHM>
Herein R<NUM> is as defined above.

Preferred examples of the compound having formula (<NUM>) include diazetidine, piperazine, and diazocine. Piperazine is most preferred from the aspects of reactivity, availability, productivity, and cost.

The method for reacting the compound having formula (<NUM>) with monoalkoxysilane II having formula (<NUM>) is not particularly limited, and a choice may be generally made among well-known methods used in the reaction with the compound having formula (<NUM>).

The invention further provides a curable composition, coating composition, and adhesive composition (collectively referred to as composition, hereinafter) comprising (A) the organosilicon compound defined above and optionally (B) a curing catalyst.

The organosilicon compound as component (A) has a specific structure, which ensures that when a cured article is obtained through coating or bonding treatment with a composition comprising the organosilicon compound, the organosilicon compound provides a cured product with better curability and flexibility than prior art compositions.

The curing catalyst (B) used in the composition is a component for promoting hydrolytic condensation reaction of hydrolysable groups on the organosilicon compound (A) with airborne moisture or dealcoholization reaction of the organosilicon compound with silanol groups, and helping the composition cure, and added for efficient curing.

The curing catalyst is not particularly limited as long as it is used in the curing of conventional moisture condensation curable compositions. Examples include alkyl tin compounds such as dibutyltin oxide and dioctyltin oxide; alkyl tin ester compounds such as dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctoate, dioctyltin dioctoate, and dioctyltin diversatate; titanates, titanium chelate compounds and partial hydrolysates thereof such as tetraisopropoxytitanium, tetra-n-butoxytitanium, tetrakis(<NUM>-ethylhexoxy)titanium, dipropoxybis(acetylacetonato)titanium, titanium diisopropoxybis(ethylacetoacetate), and titanium isopropoxyoctylene glycol; organometallic compounds such as zinc naphthenate, zinc stearate, zinc <NUM>-ethyloctoate, iron <NUM>-ethylhexoate, cobalt <NUM>-ethylhexoate, manganese <NUM>-ethylhexoate, cobalt naphthenate, aluminum trihydroxide, aluminum alcoholate, aluminum acylate, aluminum acylate salts, aluminosiloxy compounds, and aluminum chelates; aminoalkyl-substituted alkoxysilanes such as <NUM>-aminopropyltrimethoxysilane, <NUM>-aminopropyltriethoxysilane, <NUM>-aminopropylmethyldimethoxysilane, <NUM>-aminopropylmethyldiethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldiethoxysilane, bis[<NUM>-(trimethoxysilyl)propyl]amine, bis[<NUM>-(triethoxysilyl)propyl]amine, N,N'-bis[<NUM>-(trimethoxysilyl)propyl]ethane-<NUM>,<NUM>-diamine, N,N'-bis[<NUM>-(triethoxysilyl)propyl]ethane-<NUM>,<NUM>-diamine, and N-phenyl-<NUM>-aminopropyltrimethoxysilane; amine compounds and salts thereof such as hexylamine, dodecylamine phosphate and tetramethylguanidine; quaternary ammonium salts such as benzyltriethylammonium acetate; alkali metal salts of lower fatty acids such as potassium acetate, sodium acetate, and lithium oxalate; dialkylhydroxylamines such as dimethylhydroxylamine and diethylhydroxylamine; silanes and siloxanes having a guanidyl group such as tetramethylguanidylpropyltrimethoxysilane, tetramethylguanidylpropylmethyldimethoxysilane, tetramethylguanidylpropyltriethoxysilane, tetramethylguanidylpropylmethyldiethoxysilane, and tetramethylguanidylpropyltris(trimethylsiloxy)silane; and phosphazene base-containing silanes and siloxanes such as N,N,N',N',N",N"-hexamethyl-N‴-[<NUM>-(trimethoxysilyl)propyl]-phosphorimidic triamide, which may be used alone or in admixture.

Of these, preference is given to dioctyltin dilaurate, dioctyltin diversatate, tetraisopropoxytitanium, tetra-n-butoxytitanium, titanium diisopropoxybis(ethylacetoacetate), <NUM>-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, bis[<NUM>-(trimethoxysilyl)propyl]amine, N,N'-bis[<NUM>-(trimethoxysilyl)propyl]ethane-<NUM>,<NUM>-diamine, and tetramethylguanidylpropyltrimethoxysilane because of more reactivity. From the standpoint of effective cure of the composition, more preference is given to dioctyltin dilaurate, dioctyltin diversatate, <NUM>-aminopropyltrimethoxysilane, and tetramethylguanidylpropyltrimethoxysilane. From the standpoint that the composition is free of organotin compounds and less toxic, <NUM>-aminopropyltrimethoxysilane and tetramethylguanidylpropyltrimethoxysilane are especially preferred. From the standpoint of effective cure of the composition, tetramethylguanidylpropyltrimethoxysilane is most preferred.

Although the amount of the curing catalyst (B) added is not particularly limited, the amount is preferably <NUM> to <NUM> parts by weight, more preferably <NUM> to <NUM> parts by weight per <NUM> parts by weight of component (A) because it is desirable to adjust the curing rate to an appropriate range for efficient working.

The inventive composition may further comprise a solvent. The solvent used herein is not particularly limited as long as component (A) is dissolvable therein. Examples of the solvent include hydrocarbon solvents such as pentane, hexane, heptane, octane, decane, and cyclohexane; aromatic solvents such as benzene, toluene, and xylene; amide solvents such as formamide, N,N-dimethylformamide, pyrrolidone, and N-methylpyrrolidone; ester solvents such as ethyl acetate, butyl acetate, γ-butyrolactone, and propylene glycol-<NUM>-monomethyl ether-<NUM>-acetate; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; and ether solvents such as diethyl ether, dibutyl ether, cyclopentyl methyl ether, tetrahydrofuran, and <NUM>,<NUM>-dioxane, which may be used alone or in admixture.

Of these, aromatic solvents such as toluene and xylene are preferred from the standpoints of solubility and volatility.

The amount of the solvent added is preferably <NUM> to <NUM>,<NUM> parts by weight, more preferably <NUM> to <NUM>,<NUM> parts by weight per <NUM> parts by weight of component (A).

It is noted that various bases and additives such as base polymers, adhesion improvers, inorganic and organic UV absorbers, storage stability improvers, plasticizers, fillers, pigments and flavors may be added to the inventive composition depending on a particular application.

A coated solid substrate may be obtained by coating the coating composition of the invention described above on the surface of a solid substrate and curing the composition to form a coating layer. Also, a bonded laminate may be obtained by coating the adhesive composition of the invention on the surface of a solid substrate, laying another solid substrate thereon, and curing the composition to form a bond layer.

The technique of coating each composition is not particularly limited. The coating technique may be selected as appropriate from well-known techniques such as spray coating, spin coating, dip coating, roller coating, brush coating, bar coating, and flow coating.

The solid substrate is not particularly limited. Examples include organic resin substrates such as epoxy resins, phenolic resins, polyimide resins, polycarbonate resins such as polycarbonates and polycarbonate blends, acrylic resins such as poly(methyl methacrylate), polyester resins such as poly(ethylene terephthalate), poly(butylene terephthalate), and unsaturated polyester resins, polyamide resins, acrylonitrile-styrene copolymer resins, styrene-acrylonitrile-butadiene copolymer resins, polyvinyl chloride resins, polystyrene resins, blends of polystyrene and polyphenylene ether, cellulose acetate butyrate, and polyethylene resins; metal substrates such as iron, copper and steel plates; paint-coated surfaces; glass; ceramics; concrete; slates; textiles; inorganic fillers such as wood, stone, tiles, (hollow) silica, titania, zirconia, and alumina; and fiber glass parts such as glass fibers, glass clothes, glass tape, glass mat, and glass paper. The material and shape of the substrate are not particularly limited.

The inventive composition is such that upon contact with moisture in the atmosphere, hydrolytic condensation reaction of the organosilicon compound (A) or dealcoholization reaction of the organosilicon compound (A) with silanol groups takes place. As the index of moisture in the atmosphere, any humidity in the range of RH <NUM>% to <NUM>% is acceptable. Since faster hydrolysis takes place at a higher humidity, moisture may be added to the atmosphere if desired.

The temperature and time of curing reaction may vary over a range depending on various factors such as a particular substrate, moisture concentration, catalyst concentration, and the type of hydrolysable group. The curing reaction temperature is preferably normal temperature around <NUM> from the standpoint of working. To promote curing reaction, the coating may be cured by heating within the range below which the substrate is heat resistant. The curing reaction time is typically about <NUM> minute to about <NUM> week from the standpoint of working efficiency.

The inventive composition cures effectively even at normal temperature. Particularly when room temperature cure is essential for in-situ application or the like, the composition is good in cure and working because the coating surface becomes tack-free within several minutes to several hours. Nevertheless, heat treatment within the range below which the substrate is heat resistant is acceptable.

Examples and Comparative Examples are given below for further illustrating the invention.

It is noted that the viscosity is measured at <NUM> by a Brookfield rotational viscometer.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of piperazine, <NUM> of acetonitrile, and <NUM> (<NUM> mol) of diazabicycloundecene and heated at <NUM>. Then, <NUM> (<NUM> mol) of chloromethyldimethylmethoxysilane was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, chloromethyldimethylmethoxysilane disappeared completely was regarded the end of reaction. Subsequent purification by distillation yielded organosilicon compound <NUM> of the above structure.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of butylamine, <NUM> of acetonitrile, and <NUM> (<NUM> mol) of diazabicycloundecene and heated at <NUM>. Then, <NUM> (<NUM> mol) of chloromethyldimethylmethoxysilane was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, chloromethyldimethylmethoxysilane disappeared completely was regarded the end of reaction. Subsequent purification by distillation yielded organosilicon compound <NUM> of the above structure.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of aniline, <NUM> of acetonitrile, and <NUM> (<NUM> mol) of diazabicycloundecene and heated at <NUM>. Then, <NUM> (<NUM> mol) of chloromethyldimethylmethoxysilane was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, chloromethyldimethylmethoxysilane disappeared completely was regarded the end of reaction. Subsequent purification by distillation yielded organosilicon compound <NUM> of the above structure.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of sodium sulfide and <NUM> of methanol and heated at <NUM>. Then, <NUM> (<NUM> mol) of chloromethyldimethylmethoxysilane was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, chloromethyldimethylmethoxysilane disappeared completely was regarded the end of reaction. Subsequent purification by distillation yielded organosilicon compound <NUM> of the above structure.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of tetraethylene glycol bis(<NUM>-mercaptopropionate) and <NUM> (<NUM> mol) of potassium tert-butoxide and heated at <NUM>. Then, <NUM> (<NUM> mol) of chloromethyldimethylmethoxysilane was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, chloromethyldimethylmethoxysilane disappeared completely was regarded the end of reaction. Subsequently, the salt formed with the progress of reaction and the excess of basic compound were removed by pressure filtration, yielding organosilicon compound <NUM> of the above structure.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of tetraethylene glycol bis(<NUM>-mercaptopropionate) and <NUM> of <NUM>,<NUM>'-azobis-<NUM>-methylbutyronitrile and heated at <NUM>. Then, <NUM> (<NUM> mol) of methacryloyloxymethyldimethylmethoxysilane was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, methacryloyloxymethyldimethylmethoxysilane disappeared completely was regarded the end of reaction. There was obtained organosilicon compound <NUM> of the above structure.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of piperazine and <NUM> of methanol and heated at <NUM>. Then, <NUM> (<NUM> mol) of acryloyloxymethyldimethylmethoxysilane was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, acryloyloxymethyldimethylmethoxysilane disappeared completely was regarded the end of reaction. There was obtained organosilicon compound <NUM> of the above structure.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of hexamethylene diisocyanate and <NUM> of dioctyltin dilaurate and heated at <NUM>. Then, <NUM> (<NUM> mol) of mercaptomethyldimethylmethoxysilane was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, mercaptomethyldimethylmethoxysilane disappeared completely was regarded the end of reaction. There was obtained organosilicon compound <NUM> of the above structure.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of hexamethylene diisocyanate and heated at <NUM>. Then, <NUM> (<NUM> mol) of N-butylaminomethyldimethylmethoxysilane was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, N-butylaminomethyldimethylmethoxysilane disappeared completely was regarded the end of reaction. There was obtained organosilicon compound <NUM> of the above structure.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of hexamethylene diisocyanate and heated at <NUM>. Then, <NUM> (<NUM> mol) of N-phenylaminomethyldimethylmethoxysilane was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, N-phenylaminomethyldimethylmethoxysilane disappeared completely was regarded the end of reaction. There was obtained organosilicon compound <NUM> of the above structure.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of hexamethylene diisocyanate and heated at <NUM>. Then, <NUM> (<NUM> mol) of N-(dimethylmethoxysilylmethyl)piperazine was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, N-(dimethylmethoxysilylmethyl)piperazine disappeared completely was regarded the end of reaction. There was obtained organosilicon compound <NUM> of the above structure.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of isophorone diisocyanate and heated at <NUM>. Then, <NUM> (<NUM> mol) of N-(dimethylmethoxysilylmethyl)piperazine was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, N-(dimethylmethoxysilylmethyl)piperazine disappeared completely was regarded the end of reaction. There was obtained organosilicon compound <NUM> of the above structure.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of tris(<NUM>-isocyanatohexyl)isocyanurate and heated at <NUM>. Then, <NUM> (<NUM> mol) of N-(dimethylmethoxysilylmethyl)piperazine was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, N-(dimethylmethoxysilylmethyl)piperazine disappeared completely was regarded the end of reaction. There was obtained organosilicon compound <NUM> of the above structure.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of isocyanuric chloride, <NUM> of acetonitrile, and <NUM> (<NUM> mol) of diazabicycloundecene and heated at <NUM>. Then, <NUM> (<NUM> mol) of N-(dimethylmethoxysilylmethyl)piperazine was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, N-(dimethylmethoxysilylmethyl)piperazine disappeared completely was regarded the end of reaction. Since the solution after the reaction separated into two layers, the layer containing the basic compound and the salt formed with the progress of reaction was removed from the target compound layer by separatory operation. Thereafter, the target compound layer was heated at <NUM>, at which acetonitrile was distilled off under a reduced pressure below <NUM> Kpa (<NUM> mmHg), yielding organosilicon compound <NUM> of the above structure.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of isocyanuric chloride, <NUM> of acetonitrile, and <NUM> (<NUM> mol) of diazabicycloundecene and heated at <NUM>. Then, <NUM> (<NUM> mol) of mercaptomethyldimethylmethoxysilane was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, mercaptomethyldimethylmethoxysilane disappeared completely was regarded the end of reaction. Since the solution after the reaction separated into two layers, the layer containing the basic compound and the salt formed with the progress of reaction was removed from the target compound layer by separatory operation. Thereafter, the target compound layer was heated at <NUM>, at which acetonitrile was distilled off under a reduced pressure below <NUM> Kpa (<NUM> mmHg), yielding organosilicon compound <NUM> of the above structure.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of piperazine, <NUM> of acetonitrile, and <NUM> (<NUM> mol) of diazabicycloundecene and heated at <NUM>. Then, <NUM> (<NUM> mol) of chloropropyldimethylmethoxysilane was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, chloropropyldimethylmethoxysilane disappeared completely was regarded the end of reaction. Subsequent purification by distillation yielded organosilicon compound <NUM> of the above structure.

A <NUM>-mL separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with <NUM> (<NUM> mol) of piperazine, <NUM> of acetonitrile, and <NUM> (<NUM> mol) of diazabicycloundecene and heated at <NUM>. Then, <NUM> (<NUM> mol) of chloropropyltrimethoxysilane was added dropwise to the contents, which were stirred at <NUM> for <NUM> hours. On GC analysis, the time when the reactant, chloropropyltrimethoxysilane disappeared completely was regarded the end of reaction. Subsequent purification by distillation yielded organosilicon compound <NUM> of the above structure.

A composition was prepared on a moisture-blocked agitator by mixing <NUM> parts by weight of α,ω-dihydroxydimethylpolysiloxane having a viscosity of <NUM>,<NUM> mPa·s, <NUM> part by weight of organosilicon compound <NUM> obtained in Example <NUM>-<NUM>, and <NUM> part by weight of tetramethylguanidylpropyltrimethoxysilane as curing catalyst until uniform.

Compositions were prepared as in Example <NUM>-<NUM> aside from using organosilicon compounds <NUM> to <NUM> obtained in Reference Examples <NUM>-<NUM> to <NUM>-<NUM> or organosilicon compounds <NUM> to <NUM> obtained in Comparative Examples <NUM>-<NUM> to <NUM>-<NUM> instead of organosilicon compound <NUM> in Example <NUM>-<NUM>.

A composition was prepared as in Example <NUM>-<NUM> aside from omitting organosilicon compound <NUM> obtained in Example <NUM>-<NUM>.

The compositions prepared in Examples <NUM>-<NUM> and Reference Examples <NUM>-<NUM> to <NUM>-<NUM> and Comparative Examples <NUM>-<NUM> to <NUM>-<NUM> were evaluated as follows, with the results shown in Tables <NUM> and <NUM>.

A nitrogen gas-purged glass vial was charged with the composition obtained from the above preparation method, which was stored in plugged state in air at <NUM> and <NUM>% RH. After a lapse of a predetermined time, a percent viscosity rise was computed as [(viscosity after the predetermined time)/(viscosity immediately after charging)]×<NUM>. A larger value indicates that alkoxysilyl groups are more reactive.

As seen from Tables <NUM> and <NUM>, the compositions prepared in Examples <NUM>-<NUM> and Reference Examples <NUM>-<NUM> to <NUM>-<NUM> using organosilicon compounds <NUM> to <NUM> obtained in Examples <NUM>-<NUM> and Reference Examples <NUM>-<NUM> to <NUM>-<NUM> show higher viscosity rises than the compositions prepared in Comparative Examples <NUM>-<NUM> and <NUM>-<NUM>, indicating alkoxysilyl groups having better reactivity.

In contrast, the compositions of Comparative Examples <NUM>-<NUM> and <NUM>-<NUM> show little viscosity rises, indicating a failure to provide sufficient reactivity. The composition of Comparative Example <NUM>-<NUM> gelled after a lapse of the predetermined time because of an excessive increase of crosslinking density. All these compositions are unsuitable for the purpose of the invention.

A composition was prepared by mixing <NUM> parts by weight of silicone based coating agent KR-<NUM> (Shin-Etsu Chemical Co. ) and <NUM> parts by weight of organosilicon compound <NUM> obtained in Example <NUM>-<NUM> on a moisture-blocked agitator until uniform.

The composition was applied to a cold-finished steel plate by bar coater No. <NUM> in air at <NUM> and <NUM>% RH and dried and cured in air at <NUM> and <NUM>% RH for <NUM> days, obtaining a cured film.

Compositions and cured films were prepared as in Example <NUM>-<NUM> aside from using organosilicon compounds <NUM> to <NUM> obtained in Reference_Examples <NUM>-<NUM> to <NUM>-<NUM> or organosilicon compounds <NUM> to <NUM> obtained in Comparative Examples <NUM>-<NUM> to <NUM>-<NUM> instead of organosilicon compound <NUM> in Example <NUM>-<NUM>.

A composition and cured film were prepared as in Example <NUM>-<NUM> aside from omitting organosilicon compound <NUM> in Example <NUM>-<NUM>.

The cured films obtained in Examples <NUM>-<NUM> and Reference Examples <NUM>-<NUM> to <NUM>-<NUM> and Comparative Examples <NUM>-<NUM> to <NUM>-<NUM> were evaluated as follows, with the results shown in Tables <NUM> and <NUM>.

A test piece in the form of a cold-finished steel plate having a cured film formed thereon by the above coating method was tested by using a mandrel flexing tester prescribed in JIS K5600-<NUM>-<NUM>, and bending the test piece on a cylindrical mandrel having a diameter of <NUM>. It was visually observed whether or not the cured film cracked (or crazed) and peeled at the surface as a result of flexural deformation. The test piece was evaluated good (O), that is, the cured film was fully flexible, when neither cracking nor peeling was observed, and poor (×) when cracking and/or peeling was observed.

As seen from Tables <NUM> and <NUM>, the compositions prepared in Examples <NUM>-<NUM> and Reference Examples <NUM>-<NUM> to <NUM>-<NUM> using organosilicon compounds <NUM> to <NUM> obtained in Examples <NUM>-<NUM> and Reference Examples <NUM>-<NUM> to <NUM>-<NUM> are more curable than the composition prepared in Comparative Example <NUM>-<NUM>, indicating alkoxysilyl groups having better reactivity. Also the compositions using the inventive organosilicon compounds show higher flexibility than the compositions prepared in Comparative Examples <NUM>-<NUM> and <NUM>-<NUM>.

In contrast, the composition prepared in Comparative Example <NUM>-<NUM> forms a coating which remains tacky or sticky even after a lapse of a predetermined time, indicating a failure to provide sufficient reactivity. The compositions of Comparative Examples <NUM>-<NUM> and <NUM>-<NUM> failed to keep the cured film flexible because of an excessive increase of crosslinking density.

It has been demonstrated that the inventive organosilicon compounds contain monoalkoxysilyl groups and yet have high reactivity, and cured films having improved flexibility are obtained therefrom.

Claim 1:
An organosilicon compound having the structural formula (<NUM>):
<CHM>
wherein each R<NUM> is independently a C<NUM>-C<NUM> alkyl group or C<NUM>-C<NUM> aryl group,
each R<NUM> is independently a C<NUM>-C<NUM> alkyl group or C<NUM>-C<NUM> aryl group, wherein some or all of the hydrogen atoms in R<NUM> and R<NUM> may be substituted by a halogen atom or cyano group, and the C<NUM>-C<NUM> alkyl groups represented by R<NUM> and R<NUM> may be straight, branched or cyclic,
R<NUM> is an unsubstituted C<NUM>-C<NUM> alkylene group which may be a straight or branched alkylene, or cycloalkylene group.