Patent Description:
Monomers comprising siloxane units are known as a compound used for preparing medical materials including ophthalmic devices. For example, <NUM>-[tris(trimethylsiloxy)silyl]propyl methacrylate (TRIS) is widely known as a monomer for ophthalmic devices. A polymer obtained by the copolymerization of TRIS with a hydrophilic monomer, N,N-dimethylacrylamide or N-vinyl-<NUM>-pyrrolidone, has useful characteristics such as high oxygen permeability. The siloxane monomer, which is highly hydrophobic, does not have sufficient compatibility with such a hydrophilic monomer. Therefore, in the preparation of a hydrogel prepared from these for a medical material, phase separation occurs, so that the hydrogel is cloudy.

Patent Literature <NUM>, <NUM>, <NUM> and <NUM> disclose siloxanes which are represented by the following formula (a), (a'), (b) or (b') and have a glycerol methacrylate moiety. <CHM>
<CHM>
<CHM>
The aforesaid compounds have a hydroxyl group and, accordingly, good hydrophilicity. Therefore, they have the advantage of excellent compatibility with a hydrophilic monomer. Patent Literature <NUM> describes comonomers which may possibly provide for further residues in the silicone prepolymer defined in claim <NUM> thereof. The structure of an exemplary such comonomer is as follows:
<CHM>
As with the structures of the above-discussed siloxanes having a glycerol methacrylate moiety, the above siloxane has a hydroxyl group which is other than a tertiary hydroxyl group. However, the Database Reaxys erroneously identifies the above siloxane disclosed in Patent Literature <NUM> as being a compound (with Database Accession No. XRN = <NUM>) represented by the following structure:
<CHM>.

When a hydrogel is prepared using a compound having a primary or secondary hydroxyl group at a position where the aforesaid (poly)siloxane and a polymerizable group are linked with each other, the highly reactive hydroxyl group may cause an undesirable result. For example, a radical may bond to the hydroxyl group of the compound to form a hydroxy radical which may cause crosslinked structure. This may cause an unexpected increase in hardness and a decrease in hydrophilicity due to the decreased amount of hydroxyl group. Thus, the conventional siloxane compounds cannot provide a medical material having useful hydrophilicity and sufficient strength. Therefore, a compound and a composition which overcome such defects are still desired.

The purpose of the present invention is to provide a siloxane which is suitable for preparing a medical material, and a method for preparing the siloxane compound.

The present inventor conducted keen research to solve the aforesaid problems and has found that a (poly)siloxane monomer having a (poly)siloxane structure at its end and having a tertiary hydroxyl group at a position where the (poly)siloxane structure and a polymerizable group are linked with each other is excellent in compatibility with another hydrophilic monomer and does not cause unexpected formation of a crosslinked structure in a (co)polymer of the (poly)siloxane monomer and the hydrophilic monomer.

That is, the present invention provides a siloxane represented by the following formula (<NUM>):
<CHM>
wherein R<NUM> is a hydrogen atom or a methyl group, R<NUM> is a monovalent hydrocarbon group having <NUM> to <NUM> carbon atoms, L is a divalent hydrocarbon group which has <NUM> to <NUM> carbon atoms and may have one or more ether bonds, and A is a group represented by the following formula (<NUM>) or (<NUM>):
<CHM>
<CHM>
wherein n is an integer of <NUM> to <NUM>, a is an integer of <NUM> to <NUM>, b is an integer of <NUM> to <NUM>, and c is an integer of <NUM> to <NUM>, provided that a+b+c is <NUM> or more, and R is, independently of each other, a monovalent hydrocarbon group having <NUM> to <NUM> carbon atoms.

The present invention further provides a method for preparing the aforesaid siloxane; a polymer comprising recurring units derived from the aforesaid siloxane; a hydrogel comprising the aforesaid polymer; and a medical material comprising the aforesaid polymer, all in accordance with the respective definition thereof set forth in the appended claims.

The siloxane of the present invention has a tertiary hydroxyl group and, thereby, has excellent compatibility with a hydrophilic monomer. A (co)polymer having recurring units derived from the siloxane has a preferable strength. The siloxane of the present invention is useful as a monomer for preparing a medical material.

The siloxane of the present invention will be described below in detail.

The present invention provides a siloxane represented by the aforesaid formula (<NUM>). The present siloxane is characterized in that the siloxane has a (poly)siloxane structure indicated by A at the terminal, a (meth)acryloyl group at another terminal, and a tertiary hydroxyl group on the linking part between the (poly)siloxane and the (meth)acryloyl group. The hydrophilic hydroxyl group is tertiary, whereby a side reaction is prevented in the preparation of the present siloxane. On account of these characteristics, the siloxane provides a (co)polymer having a recurring unit derived from the present siloxane and having a preferable strength, while keeping its compatibility with a hydrophilic monomer.

In the aforesaid formula (<NUM>), R<NUM> is a hydrogen atom or a methyl group, preferably a methyl group.

In the aforesaid formula (<NUM>), R<NUM> is a monovalent hydrocarbon group having <NUM> to <NUM> carbon atoms. Examples of the monovalent hydrocarbon group include alkyl groups such as methyl, ethyl, propyl, n-butyl, t-butyl, pentyl, and hexyl groups; cycloalkyl groups such as cyclopentyl and cyclohexyl groups; and aryl groups such as a phenyl group. R<NUM> is preferably an alkyl group having <NUM> to <NUM> carbon atoms, more preferably a methyl group.

In the aforesaid formula (<NUM>), L is a divalent hydrocarbon group which has <NUM> to <NUM> carbon atoms and may have one or more ether bonds, preferably a divalent hydrocarbon group having <NUM> to <NUM> carbon atoms. Examples of the aforesaid divalent hydrocarbon group include ethylene, <NUM>,<NUM>-propylene, <NUM>-methylpropylene, <NUM>,<NUM>-dimethylpropylene, <NUM>-methylpropylene, <NUM>,<NUM>-dimethylpropylene, <NUM>,<NUM>,<NUM>-trimethylpropylene, <NUM>,<NUM>-butylene, <NUM>-methyl-<NUM>,<NUM>-butylene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-butylene, <NUM>-methyl-<NUM>,<NUM>-butylene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-butylene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-butylene, <NUM>,<NUM>,<NUM>-trimethyl-<NUM>,<NUM>-butylene, <NUM>,<NUM>-pentylene, <NUM>,<NUM>-hexanylene, <NUM>,<NUM>-heptanylene, <NUM>,<NUM>-octanylene, <NUM>,<NUM>-nonanylene and <NUM>,<NUM>-decanylene.

Examples of the divalent hydrocarbon group which has <NUM> to <NUM>, preferably <NUM> to <NUM> carbon atoms, and has one or more ether bonds include (poly)alkylene oxide groups such as (poly)ethylene oxide, (poly)propylene oxide, and (poly)ethylene-propylene oxide groups. Preferred is a group represented by the following formula (<NUM>):
<CHM>
wherein p is an integer of <NUM> to <NUM>; q is an integer of <NUM> to <NUM>, preferably an integer of <NUM> to <NUM>, more preferably <NUM>; the site marked with * is bonded to the carbon atom in the formula (<NUM>); and the site marked with ** is bonded to A in the formula (<NUM>).

The group represented by the aforesaid formula (<NUM>) is preferably -CH<NUM>OC<NUM>H<NUM>- or -CH<NUM>OC<NUM>H<NUM>OC<NUM>H<NUM>-.

"A" is a polysiloxane group represented by the aforesaid formula (<NUM>) or (<NUM>), n is an integer of <NUM> to <NUM>, a is an integer of <NUM> to <NUM>, b is an integer of <NUM> to <NUM>, and c is an integer of <NUM> to <NUM>, provided that a+b+c is <NUM> or more. Preferably, n is an integer of <NUM> to <NUM>. In the formula (<NUM>), it is preferred that a is <NUM>, b is <NUM>, and c is <NUM>.

R is, independently of each other, a monovalent hydrocarbon group having <NUM> to <NUM> carbon atoms, preferably <NUM> to <NUM> carbon atoms. Examples of the monovalent hydrocarbon group include alkyl groups such as methyl, ethyl, propyl, n-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups; cycloalkyl groups such as cyclopentyl and cyclohexyl groups; and aryl groups such as phenyl and tolyl groups. R is preferably an alkyl group having <NUM> to <NUM> carbon atoms, more preferably <NUM> to <NUM> carbon atoms, or a phenyl group; and more preferably a methyl, n-butyl, or t-butyl group.

A method for preparing the siloxane represented by the aforesaid formula (<NUM>) will be described below.

The preparation method of the present invention comprises a step of hydrosilylation, wherein a compound represented by the following formula (<NUM>) and having unsaturated groups at the terminals thereof:
<CHM>.

The preparation method of the present invention is characterized in that the compound represented by the formula (<NUM>) has an unsaturated bond at the terminal thereof and a tertiary hydroxyl group. In the present preparation method, because the hydroxyl group of the raw material compound represented by the aforesaid formula (<NUM>) is tertiary, any undesirable side reaction by a hydroxyl group is suppressed in the hydrosilylation reaction. Therefore, the obtained siloxane has high purity.

In the aforesaid formula (<NUM>), R<NUM> is a hydrogen atom or a methyl group, preferably a hydrogen atom.

In the aforesaid formula (<NUM>), L' is a single bond or a divalent hydrocarbon group which has <NUM> to <NUM> carbon atoms and may have one or more ether bonds, preferably a divalent hydrocarbon group having <NUM> to <NUM> carbon atoms and having one or more ether bonds.

Examples of the divalent hydrocarbon group having <NUM> to <NUM> carbon atoms include methylene and the aforesaid divalent hydrocarbon groups. Examples of the group having one or more ether bonds include (poly)alkylene oxide groups such as (poly)ethylene oxide, (poly)propylene oxide, and (poly)ethylene-propylene oxide groups. Particularly, a group represented by the following formula (<NUM>') or (<NUM>") is preferred. <CHM>
wherein p is an integer of <NUM> to <NUM>; q' is an integer of <NUM> to <NUM>, preferably <NUM> or <NUM>, more preferably <NUM>; the site marked with * is bonded to the carbon atom in the formula (<NUM>); and the site marked with ** is bonded to A in the formula (<NUM>).

Thus, the divalent hydrocarbon group represented by the formula (<NUM>') or (<NUM>") is preferably -CH<NUM>OCH<NUM>- or -CH<NUM>OC<NUM>H<NUM>OCH<NUM>-.

The hydrosilylation-reaction may be done by any known method. For example, <NUM> molar equivalent of the hydrogen siloxane compound represented by the formula (<NUM>) or (<NUM>) and <NUM> molar equivalent or more of the unsaturated compound represented by the formula (<NUM>) may be subjected to the reaction. The reaction temperature is not particularly limited, and is preferably a temperature not exceeding the boiling temperature of the solvent to be used. For example, the reaction temperature is preferably from about <NUM> to about <NUM>. The reaction may be done in the presence of a solvent, a hydrosilylation catalyst and a stabilizer. Any known solvent, hydrosilylation catalyst and stabilizer may be used.

In the aforesaid reaction, the amount of the unsaturated compound is preferably <NUM> molar equivalent or more, per mole of the hydrogen siloxane compound. The amount of the unsaturated compound is more preferably <NUM> to <NUM> molar equivalents, still more preferably <NUM> to <NUM> molar equivalent, particularly preferably <NUM> to <NUM> molar equivalents. When <NUM> molar equivalent or more of the unsaturated compound is added, the amount of the remaining hydrogen siloxane compound and a side reaction are suppressed. Although the upper limit of the amount of the unsaturated compound is not limited, too large an amount is not preferred from the standpoint of the yield and economy.

The hydrosilylation catalyst is, for example, a noble metal catalyst, particularly a platinum catalyst derived from chloroplatinic acid. Preferably, the chlorine ions of chloroplatinic acid are neutralized with sodium bicarbonate to improve stability of the catalyst. For example, a complex of <NUM>,<NUM>,<NUM>,<NUM>-tetramethyl-<NUM>,<NUM>-divinyldisiloxane and chloroplatinic acid neutralized with sodium bicarbonate (Karstedt's catalyst) is more preferred.

The amount of the hydrosilylation catalyst may be a catalytic amount sufficient to promote the aforesaid reaction. For example, the complex of <NUM>,<NUM>,<NUM>,<NUM>-tetramethyl-<NUM>,<NUM>-divinyldisiloxane and chloroplatinic acid neutralized with sodium bicarbonate may be used in an amount such that the amount of platinum is <NUM> to <NUM> ppm, based on the mass of the hydrogen siloxane compound represented by the formula (<NUM>) or (<NUM>).

Examples of the solvent include glycol ether solvents such as methyl cellosolve, ethyl cellosolve, isopropyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, polyethylene glycol monomethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and polyethylene glycol dimethyl ether; ester-based solvents such as ethyl acetate, butyl acetate, amyl acetate, ethyl lactate, and methyl benzoate; aliphatic hydrocarbon-based solvents such as linear hexane, linear heptane, and linear octane; alicyclic hydrocarbon-based solvents such as cyclohexane and ethylcyclohexane; ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; petroleum-based solvents; and alcohol-based solvents such as methyl alcohol, ethyl alcohol, linear propyl alcohol, isopropyl alcohol, linear butyl alcohol, isobutyl alcohol, tert-butyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol. The aforesaid solvents may be used either alone or in combination of two or more.

Examples of the stabilizer include phenolic antioxidants, phosphorus-based antioxidants, amine-based antioxidants, and sulfur-based antioxidants. Any phenolic antioxidant may be used, and includes compounds selected from p-methoxyphenol, di-tert-butyl-p-cresol, pyrogallol, tert-butylcatechol, <NUM>,<NUM>-thiobis(<NUM>-methyl-<NUM>-tertbutylphenol), <NUM>,<NUM>'-methylenebis(<NUM>-methyl-<NUM>-t-butylphenol), phenolic resins and cresol resins. The phosphorus-based antioxidant is not particularly limited, and includes tris[<NUM>-[[<NUM>,<NUM>,<NUM>, <NUM>-tetrakis(<NUM>,<NUM>-dimethylethyl)dibenzo[d,f][<NUM>,<NUM>,<NUM>]dioxaphosphepin-<NUM>-yl]oxy]ethyl]amine, tris[<NUM>-[(<NUM>,<NUM>,<NUM>,<NUM>-tetra-tert-butyldibenzo[d,f][<NUM>,<NUM>,<NUM>]dioxaphosphepin-<NUM>-yl)oxy]ethyl]amine, and ethylbis(<NUM>,<NUM>-ditert-butyl-<NUM>-methylphenyl)phosphite. The amine-based antioxidant is not particularly limited, and includes tri- or tetra-C<NUM>-<NUM> alkylpiperidines and derivatives thereof, bis(<NUM>,<NUM>,<NUM>,<NUM>-tetramethyl-<NUM>-piperidyl)oxalate, <NUM>,<NUM>-bis(<NUM>,<NUM>,<NUM>,<NUM>-tetramethyl-<NUM>-piperidyloxy)ethane, phenylnaphthylamine, N,N'-diphenyl-<NUM>,<NUM>-phenylenediamine, and N-phenyl-N'-cyclohexyl-<NUM>,<NUM>-phenylenediamine. The sulfur-based antioxidant is not particularly limited and includes dilaurylthiodipropionate and distearylthiodipropionate. The stabilizer may be used alone or in combinations thereof.

In each of the aforesaid reactions, the end point of the reaction may be determined by the disappearance of a peak of a raw material compound in a conventional method, for example, by thin-layer chromatography (TLC), high-speed liquid chromatography (HPLC), or gas chromatography (GC). After completion of the reaction, purification may be conducted by any conventional method. For example, the organic layer is washed with water and the solvent is removed to obtain the product. Alternatively, distillation at a reduced pressure or treatment with activated carbon may be conducted.

A method for preparing the unsaturated group-containing compound represented by the aforesaid formula (<NUM>) is not particularly limited. The unsaturated group-containing compound may be obtained, for example, by reacting an epoxy compound represented by the following formula (a) with a (meth)acrylic acid. <CHM>
wherein R<NUM>, R<NUM> and L' are as described above.

The compound represented by the aforesaid formula (a) may be prepared in any conventional manner. For example, an epoxy compound represented by the aforesaid formula (a), having <NUM> to <NUM> carbon atoms and L' having one or more ether bonds are obtained by reacting an alcohol compound represented by the following formula (<NUM>):
<CHM>.

The reaction between the aforesaid alcohol compound and the epoxy compound may be conducted in accordance with any conventional manner. For example, <NUM> molar equivalent or more of the epoxy compound and <NUM> molar equivalent of the alcohol compound are put together and subjected to the reaction. The reaction temperature is not particularly limited, but is preferably not higher than the boiling temperature of the solvent used. For example, the reaction temperature is preferably about <NUM> to about <NUM>. The aforesaid reaction may be conducted in the presence of a solvent and a catalyst. The solvent and catalyst are not particularly limited and may be any known ones.

The reaction of the epoxy compound represented by the formula (a) with (meth)acrylic acid may be done in any known manner. For example, <NUM> molar equivalent of the epoxy compound and <NUM> molar equivalent or more of (meth)acrylic acid may be subjected to the reaction. The reaction temperature is not particularly limited, and is preferably a temperature not exceeding the boiling temperature of the solvent to be used. For example, the reaction temperature is preferably from about <NUM> to about <NUM>. The reaction may be done in the presence of a solvent, a catalyst and a stabilizer. Any known solvent, catalyst and stabilizer may be used. The solvent may be those described above.

Examples of the catalyst include organometallic catalysts, basic compounds, organophosphorus-based compounds, amine catalysts, and Lewis acids. Examples of the stabilizers include phenolic antioxidants, phosphorus-based antioxidants, amine-based antioxidants, and sulfur-based antioxidants. Specific examples are as described above.

In an embodiment of the preparation method of the present invention, <NUM> molar equivalent of the hydrogen siloxane compound represented by the formula (<NUM>) or (<NUM>), <NUM> molar equivalents of the unsaturated compound represented by the aforesaid formula (<NUM>), a solution of a complex of chloroplatinic acid neutralized with sodium bicarbonate and vinyl siloxane in toluene (platinum content: <NUM> wt%) in an amount of <NUM> ppm of platinum, based on the mass of the polysiloxane compound, and <NUM> mass% of toluene, based on the hydrogen siloxane compound, are put together and stirred at <NUM> in a nitrogen atmosphere to be allowed to react for about <NUM> hours, whereby the reaction is completed. The progress of the reaction may be followed by monitoring the unsaturated compound or a formed compound by GC. After completion of the reaction, n-hexane is added in an amount of <NUM> mass%, based on the hydrogen siloxane compound, and the organic layer is separated and washed with aqueous methanol (methanol:water = <NUM>:<NUM>). Then, the solvent and the unreacted raw material present in the organic layer are distilled off at a reduced pressure to obtain a siloxane compound represented by the aforesaid formula (<NUM>).

The siloxane compound of the present invention may be converted into a polymer comprising the recurring unit derived from the addition polymerization at the (meth)acrylic group. The siloxane compound of the present invention has good compatibility with another compound having a polymerizable group such as a (meth)acrylic group (hereinafter referred to as "a polymerizable monomer" or "a hydrophilic monomer"). A copolymer with the polymerizable monomer is therefore colorless and transparent. Alternatively, the siloxane compound of the present invention may be homo-polymerized.

In the preparation of the copolymer comprising the recurring units derived from the polymerization of the siloxane compound of the present invention and from another polymerizable (or hydrophilic) monomer, the amount of the siloxane compound of the present invention may be such that the mass of the recurring unit derived from the siloxane compound of the present invention is at least <NUM> % by mass, based on the mass of the copolymer. More specifically, the amount of the siloxane compound of the present invention may be <NUM> to <NUM> parts by mass, more preferably <NUM> to <NUM> parts by mass, relative to total <NUM> parts by mass of the siloxane compound of the invention and the polymerizable (hydrophilic) monomer. If the mass percent of the recurring unit is less than <NUM>%, the resulting copolymer is unlikely to exhibit the properties of the present compound.

Examples of the polymerizable monomer include acrylic monomers such as (meth)acrylic acid, methyl(meth)acrylate, ethyl(meth)acrylate, (poly)ethylene glycol dimethacrylate, polyalkylene glycol mono(meth)acrylate, polyalkylene glycol monoalkyl ether (meth)acrylate, trifluoroethyl (meth)acrylate, <NUM>-hydroxyethyl (meth)acrylate, and <NUM>,<NUM>-dihydroxypropyl (meth)acrylate; acrylic acid derivatives such as N,N-dimethylacrylamide, N,N-diethylacrylamide, N-acryloylmorpholine, and N-methyl (meth)acrylamide; N-vinylpyrrolidone, and other unsaturated aliphatic or aromatic compounds such as crotonic acid, cinnamic acid, and vinyl benzoic acid; and siloxane monomers having a polymerizable group such as (meth)acrylic group. The monomer may be used alone or in combinations thereof.

The copolymerization of the siloxane compound of the present invention with the another polymerizable monomer may be conducted in any conventional manner, for example, in the presence of a known polymerization initiator such as a heat polymerization initiator or a photopolymerization initiator. Examples of the polymerization initiator include <NUM>-hydroxy-<NUM>-methyl-<NUM>-phenyl-propan-<NUM>-one, azobisisobutyronitrile, azobisdimethylvaleronitrile, benzoyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, and <NUM>,<NUM>'-azobis(<NUM>-methylpropionamidine) dihydrochloride. The polymerization initiator may be used alone or in combinations thereof. The amount of the polymerization initiator is preferably from <NUM> to <NUM> parts by mass, more preferably from <NUM> to <NUM> part by mass, per total <NUM> parts by mass of the components to be polymerized.

The polymer of the present invention, which polymer comprises the recurring unit derived from the siloxane compound of the present invention, is excellent in hydrophilicity. The hydrogel obtained from the polymer is excellent in transparency and strength. The siloxane compound of the present invention is therefore suited for use in the preparation of medical materials such as ophthalmic devices, contact lenses, intraocular lenses, and artificial corneas. The method of preparing a medical material from the polymer of the present invention is not particularly limited and may be any conventional method. For example, a cutting process or a molding process may be used for shaping the polymer into a lens, such as contact lens or intraocular lens.

The present invention will hereinafter be described more specifically with reference to the following Examples and Comparative Examples, but the present invention is not limited by the following Examples. In the following Examples, <NUM>H-NMR analysis was done with JEOL ECS400 using deuterated chloroform as a measurement solvent. The gas chromatography (GC) was conducted under the following conditions.

The following compounds were used in the following Examples and Comparative Examples.

In a <NUM>-mL three-necked eggplant flask equipped with a Dimroth condenser and a thermometer, was added <NUM> of <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-heptamethyltrisiloxane, <NUM> of AHMPM (thus, the molar ratio of the unsaturated compound to the hydrogen siloxane compound is <NUM>), and <NUM> of a solution of a complex of chloroplatinic acid neutralized with sodium bicarbonate and vinyl siloxane in toluene (platinum content: <NUM> wt%) in a nitrogen atmosphere. The resulting mixture was heated to <NUM> and aged for <NUM> hours. After completion of the reaction, <NUM> of n-hexane was added and the resulting mixture was washed five times with an aqueous methanol solution (methanol:water = <NUM>:<NUM>). The solvent and the unreacted raw materials were distilled off at a temperature of <NUM> and a reduced pressure to obtain a colorless, transparent liquid. The yield was <NUM>. According to <NUM>H-NMR, the liquid was a compound represented by the following formula (<NUM>). <CHM>
The <NUM>H-NMR data are as follows.

The procedures of Example <NUM> were repeated, except that <NUM> of a hydrogen siloxane compound represented by the following formula (10A) was used instead of <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-heptamethyltrisiloxane used in Example <NUM>, and the amount of AHMPM was changed to <NUM> (thus, the molar ratio of the unsaturated compound to the hydrogen siloxane compound is <NUM>) to thereby obtain a colorless, transparent liquid. The yield was <NUM>. According to <NUM>H-NMR, the liquid was a compound represented by the following formula (10B). <CHM>
<CHM>
The <NUM>H-NMR data are as follows.

The procedures of Example <NUM> were repeated, except that <NUM> of a hydrogen siloxane compound represented by the following formula (11A) was used instead of <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-heptamethyltrisiloxane used in Example <NUM> and the amount of AHMPM was changed to <NUM> (thus, the molar ratio of the unsaturated compound to the hydrogen siloxane compound is <NUM>) to obtain a colorless, transparent liquid. The yield was <NUM>. According to <NUM>H-NMR, the liquid was a compound represented by the following formula (11B). <CHM>
<CHM>
The <NUM>H-NMR data are as follows.

The hydrogen siloxane compound represented by the aforesaid formula (10A), the following AHMPM (tertiary hydroxyl group-containing compound) or the following AHPM (secondary hydroxyl group-containing compound), and a solution of a complex of chloroplatinic acid neutralized with sodium bicarbonate and vinyl siloxane in toluene (platinum content: <NUM> wt%) were mixed in the amounts described in Table <NUM>. The resulting mixture was heated to <NUM> in a nitrogen atmosphere and aged for <NUM> hours. After completion of the reaction, the reaction mixture was subjected to GC analysis and the purity of the intended product was calculated from the area %, provided that any remaining raw materials, hydrogen siloxane compound, AHMPA, and AHPM, were neglected in the calculation of the purity. The results are as shown in Table <NUM>.

As seen in Table <NUM>, when the molar ratio of AHMPM having a tertiary hydroxyl group to the hydrogen siloxane compound is <NUM> or more in the addition reaction, the intended compound has a particularly improved purity. A side reaction during the hydrosilylation reaction is suppressed, which further increases the purity. In contrast, the compound obtained in Comparative Example <NUM> by the addition reaction of the unsaturated group-containing compound (AHPM) having a secondary hydroxyl group and the hydrogen siloxane has a lower purity compared to the compound of Example <NUM> prepared in the same molar ratio. This result means that any side reaction occurred more during the hydrosilylation reaction in Comparative Example <NUM>.

The compounds obtained in the aforesaid Examples <NUM> to <NUM>, SiGMA represented by the following formula, <NUM>-[tris(trimethylsiloxy)silyl]propyl methacrylate (TRIS) represented by the following formula, <NUM>-hydroxyethyl methacrylate (HEMA), N,N-dimethylacrylamide (DMA), ethylene glycol dimethacrylate (EGDMA), and Irgacure1173 (Irg1173) were mixed in the composition with the ratios shown in Table <NUM> or <NUM> and stirred until the mixture became a uniform solution. After the stirring, bubbling with N<NUM> was carried out for <NUM> minutes for sufficient deaeration and, then, the solution was put in a mold made of polypropylene and the mold was sealed. The mold containing the solution was irradiated with UV with a high-pressure mercury lamp to cure the solution. After the curing, the resulting resin was taken out from the mold and immersed in isopropanol, a <NUM>% aqueous solution of isopropanol and then deionized water for washing to obtain a hydrogel film. Physical properties of the film thus obtained were determined by the methods described below. The results are as shown in Tables <NUM> and <NUM>.

The film was immersed in deionized water at <NUM> for <NUM> hours, water on the film surface was wiped off, and the mass of the hydrated film was measured. Then, the hydrated film was dried in an oven at <NUM> for <NUM> hours and then at <NUM> for <NUM> hours and the mass of the dried film was measured. The equilibrium water content was calculated according to the following formula: <MAT>.

The film was immersed in deionized water at <NUM> for <NUM> hours and water on the film surface was wiped off to prepare a hydrated film. The appearance of the hydrated film was visually evaluated, based on the following criteria:.

The film was immersed in deionized water at <NUM> for <NUM> hours, water on the film surface was wiped off to prepare a hydrated film. The Young's modulus of elasticity of the hydrated film was determined using Instron <NUM>, as follows. A sample piece of <NUM> × <NUM> obtained by cutting the hydrated film was stretched with a load cell of <NUM> N at a head speed of <NUM>/min to obtain a curve of the stress in the ordinate and the strain in the abscissa. The slope of the stress-strain curve in the initial linear stage was determined. The slope is the Young's modulus of elasticity in MPa.

As seen in Table <NUM>, the hydrogel prepared with TRIS only as a comparative compound has a poor transparency (Comparative Example <NUM>). The hydrogels prepared with SiGMA only or the combination of SiGMA and TRIS as a comparative compound show a too high modulus of elasticity (Comparative Examples <NUM> and <NUM>).

In contrast, as seen in Table <NUM>, the hydrogel prepared with the siloxane compound of the present invention has excellent transparency and a suitable modulus of elasticity. Thus, the hydrogel obtained using the siloxane compound of the present invention has both a useful hydrophilicity and sufficient strength.

Claim 1:
A siloxane represented by the following formula (<NUM>):
<CHM>
wherein R<NUM> is a hydrogen atom or a methyl group, R<NUM> is a monovalent hydrocarbon group having <NUM> to <NUM> carbon atoms, L is a divalent hydrocarbon group which has <NUM> to <NUM> carbon atoms and may have one or more ether bonds, and A is a group represented by the following formula (<NUM>) or (<NUM>):
<CHM>
<CHM>
wherein n is an integer of <NUM> to <NUM>, a is an integer of <NUM> to <NUM>, b is an integer of <NUM> to <NUM>, and c is an integer of <NUM> to <NUM>, provided that a+b+c is <NUM> or more, and R is, independently of each other, a monovalent hydrocarbon group having <NUM> to <NUM> carbon atoms.