JPH10316757A - Cationically photopolymerizable organosilicon compound and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cationically photopolymerizable organosilicon compound which can give a cured film having excellent adhesion even to an inorganic material such as a metal and is useful as a coating agent for release films or a stainproofing coating agent by effecting the addition reaction of a polysiloxane with an alkenyl-terminated oxetane compound. SOLUTION: The addition reaction of a polysiloxane with an alkenyl- terminated oxetane compound is effected to prepare a cationically polymerizable organosilicon compound of formula I (wherein R<0> is an organic functional group having oxetanyl; R<1> to R<3> are each an alkyl, a cycloalkyl or an aryl; and n is 1-10,000). It is desirable that R<0> in formula I is a functional group represented by formula II (wherein R<4> is hydrogen or a 1-6 C alkyl; and R<5> is a 2-6 C alkylene). The addition reaction is effected in the presence of a group 8 metal catalyst (e.g. Co, Ni, Pd or Pt). Because the polysiloxane as a starting material is an alkoxyhydrosilicone with its ends terminated, it can be easily reacted in the presence of a platinum catalyst in a manner in which the ring opening of the oxetanyl groups can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cationic photopolymerizable organosilicon compound and a method for producing the same.
The present invention relates to a cationic photopolymerizable organosilicon compound having a siloxane bond in the main chain, and an organic functional group having an alkoxy group and an oxetanyl group bound to both terminal silicon atoms, and a method for producing the same. The organosilicon compound of the present invention is useful as a macromonomer for photocationic polymerization, a polymer-type silane coupling agent, and the like.

[0002]

2. Description of the Related Art In the field of ultraviolet (UV) -initiated polymerization or ultraviolet-initiated curing, photoinitiated radical polymerization using polyfunctional acrylates and unsaturated polyesters has been widely studied and industrially used. However, since this radical polymerization is inhibited by oxygen in the air or the like, it is necessary to carry out the polymerization under an inert atmosphere in order to rapidly and completely polymerize the monomer.

[0003] On the other hand, photoinitiated cationic polymerization is not affected by polymerization inhibition by oxygen, unlike the photoinitiated radical polymerization, and can be completely polymerized even in air. Representative monomers used for photoinitiated cationic polymerization include epoxides and vinyl ethers. In particular, when an epoxide is used as a monomer, it is possible to obtain a cured product having good heat resistance, excellent adhesive strength, and good chemical resistance.

[0004]

However, the epoxide type photocurable monomer has a relatively low photopolymerization rate of the epoxy group, and therefore has a rapid photocurable property particularly when coated on paper or plastic. However, it is not always preferable for applications requiring the above.

On the other hand, since the photopolymerization rate of an oxetanyl group is usually much higher than that of an epoxy group, a compound having this oxetanyl group is useful as a monomer for photoinitiated cationic polymerization. JP-A-6-16804 discloses various monomers having an oxetanyl group,
As an example, a compound represented by the following formula (IV), that is, a compound having an oxetanyl group introduced at both ends of silicone is shown.

[0006]

Embedded image (However, each of R ² and R ³ is, for example, an alkyl group or an aryl group having 1 to 4 carbon atoms, and R ⁴ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a fluorine atom, A fluoroalkyl group, an allyl group, an aryl group, a furyl group or a thienyl group having 1 to 6 carbon atoms, and n is an integer of 0 to 2,000.)

However, a cured film of a composition comprising the above compound generally has low adhesion to a substrate, and it is difficult to obtain practically sufficient adhesion particularly when the substrate is an inorganic substance such as a metal. It is. This is presumably because the compound has no functional group other than the oxetanyl group, and thus has poor binding ability with an inorganic substance. Further, in the above-mentioned publication, the above-mentioned compound is produced using both ends of the hydrosilicone as a raw material. However, since the both ends of the hydrosilicone are expensive, the material cost increases. Furthermore, in the above publication, a rhodium catalyst is used as a reaction catalyst when introducing an oxetanyl group, but this rhodium catalyst is also expensive.

Another object of the present invention is to provide a novel cationic photopolymerizable organosilicon compound which can be produced using relatively inexpensive raw materials and catalysts and has excellent adhesion to inorganic substances such as metals. It is in. Still another object of the present invention is to provide a suitable method for producing the above-mentioned cationic photopolymerizable organosilicon compound.

[0009]

Means for Solving the Problems The present inventors have synthesized a novel photocationically polymerizable compound in which an oxetanyl group is introduced into both ends of silicone and the silicon atom at both ends of the silicone has an alkoxy group. did. This compound has a high photocationic polymerization rate due to oxetanyl groups and alkoxy groups, and provides a cured film having excellent adhesion to a substrate as compared with the compound represented by the above formula (IV). I found it. Furthermore, they have found a method for easily producing this compound using relatively inexpensive raw materials and catalysts, and have completed the present invention.

That is, the photocationically polymerizable organosilicon compound of the first invention in the present invention is characterized by being represented by the following structural formula (I).

[0011]

Embedded image (However, R ⁰ is an organic functional group having an oxetanyl group, R ¹ , R ² and R ³ are all alkyl groups, cycloalkyl groups or aryl groups, and n is 1 to 10,000.
Is a positive number. )

The organosilicon compound represented by the above formula (I) has a structure in which an oxetanyl group having a high photocationic polymerization rate is introduced into both terminals of silicone and an alkoxy group is bonded to silicon atoms at both terminals of the silicone. Have.
Since this compound has an alkoxy group in addition to a group having photocationic polymerizability, it is useful as a film coating agent for release, a stain-resistant coating agent, and the like. For example, when used as a photocationically polymerizable coating composition, a coating film having excellent adhesion to a substrate can be obtained as compared with an organosilicon compound having the same structure except that it does not have an alkoxy group. Further, the hardness of the cured film can be improved by condensing the alkoxy groups before and / or after the curing. Furthermore, by utilizing this alkoxy group to introduce another functional group into the compound or its cured product,
Alternatively, it is also possible to impart a hydrophilic property by introducing a hydroxyl group into the cured film by hydrolysis of an alkoxy group.

As in the second invention, R ⁰ is preferably an organic functional group represented by the following structural formula (II). This is because such a photocationically polymerizable organosilicon compound is easy to produce and is suitable for the above applications.

[0014]

Embedded image (However, R ⁴ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R ⁵ is an alkylene group having 2 to 6 carbon atoms.)

The third invention of the present invention is a method for producing the organosilicon compound of the first invention or the second invention, which comprises the following formula (I)
It is characterized in that the polysiloxane represented by the structural formula shown in II) is subjected to an addition reaction with an oxetane compound having an alkenyl terminal.

[0016]

Embedded image (However, R ¹ , R ² and R ³ are all alkyl groups, cycloalkyl groups or aryl groups, and n is 1 to 10,0
00 is a positive number. )

The compound represented by the above formula (III) can be produced at lower cost than hydrosilicone at both ends, and thus has the advantage of reducing raw material costs. Further, by using this compound as a raw material, the first invention or the second invention can be carried out by using a platinum catalyst, which is less expensive than a rhodium catalyst or the like, in a hydrosilylation reaction between the compound and an oxetane compound.
The organosilicon compound of the invention can be obtained.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the present specification, a compound having an oxetanyl group is referred to as an “oxetane compound”. Cationic photopolymerizable organic silicon compound of the invention, R ¹ in the above-mentioned formula (I),
R ² and R ³ are an alkyl group, a cycloalkyl group or an aryl group, respectively. Examples of the "alkyl group" include a methyl group, an ethyl group, an n- and i-propyl group,
-, I- and t-butyl groups. Examples of the “cycloalkyl group” include a cyclohexyl group,
Examples of the “aryl group” include a phenyl group.

One molecule of the compound represented by the formula (I) contains four R ^{1 s,} which may be the same group or two or more different groups. Also, R ²
And R ³ may be the same group or different groups. Furthermore, may be an n-number of R ² is also different for two or more be all the same radical groups contained in one molecule, R ³
The same applies to.

Among them, R ¹ is preferably an alkyl group having 1 to 3 carbon atoms, that is, —OR ¹ is preferably a methoxy group, an ethoxy group, an n-propoxy group or an i-propoxy group. In this case, since the hydrolyzability of the alkoxy group bonded to the silicon atoms at both ends is improved, this alkoxy group is effectively used for improving the adhesion to the substrate and improving the film strength by moisture curing. can do.

Further, R ² and R ³ are preferably a methyl group or an ethyl group, and more preferably all of R ² and R ³ are a methyl group. In this case, the organosilicon compound of the present invention can be produced from inexpensive raw materials,
This organosilicon compound is preferable because it easily gives so-called “silicone properties” such as releasability, surface lubricity, and water / oil repellency. Further, it is preferred that the four R ^{1 s} present in one molecule be the same group, because the synthesis of the organosilicon compound of the present invention is easy. Also,-
When OR ¹ is an ethoxy group, there is an advantage that the organosilicon compound of the present invention has low toxicity.

R ⁰ in the above formula (I) is not particularly limited as long as it is an organic functional group having at least one oxetanyl ring in a part thereof, and is a group represented by the structural formula shown in the above formula (II). Preferably, there is. In the formula (II), R ⁴ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and it is particularly preferable that R ⁴ is an ethyl group. R ⁵ is an alkylene group having 2 to 6 carbon atoms, and R ⁵ is particularly preferably a propylene group. This is because it is easy to obtain or synthesize such an oxetane compound.

In the above formula (I), n is 1 to 1.
It is a positive number of 0000. If n exceeds 10,000, problems occur such that the viscosity is too high and handling becomes difficult. From the viewpoint of preventing this problem, n is 1,000
Or less, more preferably 200 or less. The preferred range of n varies depending on the use of the organosilicon compound. For example, n is preferably 1 to 6 in applications where high strength is required for the cured product, and in applications where high tensile strength is required for the cured product. n is 100 to 20
It is preferably 0.

The method for producing the cationic photopolymerizable organosilicon compound of the present invention comprises an addition reaction of the polysiloxane represented by the structural formula (III) and an alkenyl-terminated oxetane compound. Here, “having an alkenyl terminal” means that the oxetane compound has at least one of a vinyl group, an allyl group, an ethynyl group, a propargyl group, an isopropenyl group, and the like at its terminal. Among these, it is preferable that the alkenyl terminal is an allyl group because the raw material can be easily obtained and synthesized, and the subsequent hydrosilylation reaction can be easily performed. In order to prevent gelation during the reaction, the oxetane compound preferably has one alkenyl terminal.

The preferred ranges of R ¹ , R ² , R ³ and n in the above formula (III) and the reasons thereof are as described above in the description of the formula (I).

Next, a method of "addition-reacting" the compound represented by the formula (III) with an oxetane compound will be described. This is a hydrosilylation reaction between Si-H groups at both ends of the compound represented by the above formula (III) and the alkenyl end of the oxetane compound, and proceeds in the presence of a Group VIII metal catalyst or the like.

Examples of the "group 8 metal catalyst" include simple substances of group 8 metals such as cobalt, nickel, ruthenium, rhodium, palladium, iridium and platinum, organometallic complexes, metal salts and metal oxides. . Among them, a platinum metal simple substance, an organometallic complex, a metal salt and a metal oxide are preferable, because the catalyst activity is appropriate and the handling is easy, and it is relatively inexpensive. It is particularly preferable to use an organic platinum complex. This catalyst is preferably used in an amount of 10 to 1,000 ppm by weight based on the total amount of the compound represented by the formula (III) and the oxetane compound. Other reaction conditions in the hydrosilylation reaction are not particularly limited, but a preferable reaction temperature is 20 to 80 ° C, and a preferable reaction time is 2 to 1
0 hours.

Here, unlike the compound represented by the above formula (III), in the hydrosilicone having an alkyl group at both terminal silicon atoms of the silicone (hereinafter referred to as "both terminal alkylhydrosilicone"), an oxetane having an alkenyl terminal is used. When a platinum catalyst is used in the hydrosilylation reaction with the compound, many side reactions such as ring opening of the oxetanyl group occur, so that the reaction system gels and the like, and the desired organosilicon compound cannot be obtained. Therefore, in the production of a photocationically polymerizable organosilicon compound using alkylhydrosilicone at both ends as a raw material, it is necessary to use a rhodium catalyst or the like having a lower catalytic activity than a platinum catalyst as a catalyst. However, there is a problem in that it is more expensive than the above. Further, in order for the rhodium catalyst to be uniformly present in the reaction system, it was necessary to use a solvent.

On the other hand, since the compound represented by the above formula (III) is a “both-terminal alkoxyhydrosilicone” in which both silicon atoms at the both ends of the silicone have an alkoxy group, the oxetanyl group can be used even when a platinum catalyst is used during the reaction. Is difficult to open. Therefore, the target compound, that is, the organosilicon compound of the present invention, can be obtained using a platinum catalyst that is less expensive than a rhodium catalyst. Further, unlike the rhodium catalyst, the platinum catalyst can be dissolved or uniformly dispersed in the reaction system without using a solvent, so that the reaction can be performed substantially without a solvent.

Further, the compound represented by the formula (III) can be suitably produced, for example, by a condensation reaction of a compound represented by the following formula (V) with a compound represented by the following formula (VI). Since all of the following compounds are relatively inexpensive,
The compound shown in I) can be produced at a lower cost than the alkylhydrosilicone at both ends. This condensation reaction is preferably carried out under the condition that the compound represented by the following formula (VI) becomes excessive (preferably large excess). Further, at the time of the reaction, a transesterification catalyst such as p-toluenesulfonic acid or trifluoroacetic acid may be used. However, it is preferred that the condensation reaction be allowed to proceed in a neutral atmosphere without using these catalysts.

[0031]

Embedded image (However, R ² and R ³ are an alkyl group, a cycloalkyl group or an aryl group, respectively, and n is a positive number of 1 to 10,000.)

[0032]

Embedded image (However, R ¹ is an alkyl group, a cycloalkyl group or an aryl group.)

[0033]

The present invention will be described more specifically with reference to the following examples and comparative examples.

(1) Synthesis of a photocationically polymerizable organosilicon compound (Synthesis Example 1) This is a compound represented by the above formula (III) which is used as a raw material in the method for producing a photocationically polymerizable organosilicon compound of the present invention. This is an example of synthesizing an alkoxyhydrosilicone. According to the reaction formula shown in the following formula (1),
R ¹ in the above formula (III) is an ethyl group, both R ² and R ³ are methyl groups, and n-terminal ethoxyhydropolydimethylsiloxane in which n is about 25 was synthesized.

[0035]

Embedded image

The raw materials used are as follows. [Raw materials] (1) Polydimethylsiloxane-α, ω-diol (manufactured by Chisso Corporation, molecular weight: about 2,000, trade name “DMS”
-S15 ") (2) Triethoxysilane (trade name" TRIS "manufactured by Toagosei Co., Ltd.)

Hereinafter, the reaction operation will be described. In a reactor equipped with a stirrer, thermometer and cooler, 157.0 g of polydimethylsiloxane-α, ω-diol (7
8.5 mmol, 156.1 mmol as a hydroxyl group) were charged, and after degassing in vacuo, the inside of the system was replaced with nitrogen. The reactor was heated to 60 ° C and triethoxysilane 14 was added.
8.9 g (908 mmol) was added, and the reaction was allowed to proceed with stirring while maintaining the inside of the system at 60 ° C. Follow the progress of the reaction by gas chromatography,
The reaction was terminated when the composition ratio of the raw material triethoxysilane and the by-produced ethanol stopped changing. Excess triethoxysilane and by-produced ethanol were removed from the obtained reaction solution under reduced pressure. Further, volatile impurities are removed under a heated vacuum atmosphere, and ethoxyhydropolydimethylsiloxane at both ends, which is the target substance, is removed.
3.1 g were obtained.

(Example 1) An oxetane compound having an alkenyl terminal was added to the ethoxyhydropolydimethylsiloxane at both ends obtained in Synthesis Example 1 according to the reaction formula shown in the following formula (2) to give the above-mentioned formula (I) And R in formula (II)
¹ is an ethyl group, both R ² and R ³ are methyl groups, R ⁴ is an ethyl group, R ⁵ is a propylene group, and n is about 25. A reactive organosilicon compound was produced. In addition, as the "oxetane compound having an alkenyl terminal", 3-ethyl-3-allyloxymethyloxetane was used.

[0039]

Embedded image

Hereinafter, the reaction operation will be described. In a reactor equipped with a stirrer, a thermometer and a cooler, 50.4 g of 3-ethyl-3-allyloxymethyloxetane was added.
(322.6 mmol) and 114.2 g of ethoxyhydropolydimethylsiloxane at both ends obtained in Synthesis Example 1 (5
1.9 mmol, assuming a molecular weight of 2,200). After the temperature inside the system was raised to 70 to 80 ° C., PtCl ₂ (C ₆ H
500 μl of a 0.05 M benzonitrile solution of ₅ CN) ₂ was added. Thereafter, the reaction was allowed to proceed while maintaining the inside of the system at 70 to 80 ° C. The progress of the reaction was confirmed by the rise in temperature in the system. After completion of the reaction, excess volatile substances such as 3-ethyl-3-allyloxymethyloxetane and benzonitrile are distilled off under a heated vacuum atmosphere, and the catalyst residue is further removed. The photocationically polymerizable organosilicon compound A-1 of the invention was obtained.

The structure of the organosilicon compound A-1 is shown in the following formula (VII). FIG. 1 shows an IR chart and FIG. 2 shows an NMR chart of the compound A-1. FIG.
The peak of 1260 cm ^-1 in the IR chart of the Si-CH ₃ bonds of dimethyl siloxane chain, also 1000
The peak at ~ 1100 cm ^-1 is the S ^value of the dimethylsiloxane chain.
It is attributed to the i-O-Si bond. Further, the peak at 0.3 ppm in the NMR chart of FIG. 2 corresponds to the hydrogen atom of the methyl group bonded to silicon of the dimethylsiloxane chain.
The peaks at 2 ppm and 3.8 ppm correspond to the hydrogen atoms of the ethoxy group bonded to both terminal silicon atoms, and the peaks at 4.3 ppm and 4.4 ppm correspond to -CH ₂ in the oxetane ring.
-Attributed to a hydrogen atom.

[0042]

Embedded image

Comparative Example 1 According to the following method, R ¹ , R ² , R ³ and n in the above formula (I) are the same as those of the organosilicon compound A-1 of Example 1, but R ⁰ is oxetanyl. An organosilicon compound B-1 which is an organic functional group having an epoxy group instead of a group was prepared. That is, 3-ethyl-3-
Except for using allyl glycidyl ether instead of allyloxymethyl oxetane, in the same manner as in Example 1,
An organosilicon compound B-1 of Comparative Example 1 having an alkoxy group and an epoxy group at both ends of the silicone was obtained. The structure of this organosilicon compound B-1 is shown in the following formula (VIII).

[0044]

Embedded image

(Comparative Example 2) By the same operation as in Example 1, an attempt was made to produce an organosilicon compound having oxetanyl groups at both ends but silicon at both ends having an alkyl group instead of an alkoxy group. . That is, the 3-ethyl-3- used in Example 1 was placed in a reactor purged with nitrogen.
6.3 g of allyloxymethyl oxetane (40.3 mm
ol) and both ends of a silicone having no alkoxy group at both ends of the silicon atom having no alkoxy group (manufactured by Chisso Corporation, trade name "DMS-H21", molecular weight 6)
00) 6.0 g (10.0 mmol). After the temperature in the system was raised to 70 ° C., PtCl ₂ (C ₆ H ₅ C
100 μl of a 0.05 M solution of N) ₂ in benzonitrile was added. As a result, after a while, the temperature and viscosity in the system rapidly increased. Finally, the inside of the system was solidified in a gel state, and the solidified product was analyzed. As a result, ring-opening polymerization of oxetane was observed.

(2) Evaluation of photocationically polymerizable organosilicon compound (2-1) Comparison of photocationic polymerization rate Organosilicon compound A-1 having an oxetanyl group and an alkoxy group obtained in Example 1, and comparison The tackifying energy (TFE) of the organosilicon compound B-1 having an epoxy group and an alkoxy group obtained in Example 1 was measured. For the measurement, a conveyor-type UV irradiation device (manufactured by i-Graphics Co., Ltd., model name "Power supply for ultraviolet curing of eye") was used. The measurement results are shown in Table 1 below. Here, the unit “mJ /
"cm < ² >" represents the minimum energy required for curing per square centimeter. That is, the smaller the value, the higher the photocurability.

[0047]

[Table 1]

As can be seen from Table 1, the organosilicon compound A-1 having an oxetanyl group has significantly higher photocurability than the organosilicon compound B-1 having an epoxy group.

(2-2) Evaluation of Adhesion and Hardness For the organosilicon compound A-1 having an oxetanyl group and an alkoxy group, and the organosilicon compound C-1 having an oxetanyl group but having no alkoxy group, The adhesion to the material was evaluated. In addition, this organosilicon compound C-1
Was prepared by the method of Comparative Example 2 using a rhodium catalyst in place of PtCl ₂ (C ₆ H ₅ CN) ₂ and using toluene as a solvent. The structure of this organosilicon compound C-1 is represented by the following formula (IX)
Shown in

[0050]

Embedded image

The adhesion was evaluated by the following method.
That is, each compound was applied on a base material shown in Table 2 below using a bar coater, and cured by irradiating UV under the following conditions. The cured film was evaluated for adhesion by the JIS K 5400 “cross-cut tape method”. The evaluation was performed on both the cured film immediately after curing by irradiation and the cured film exposed to moisture for 5 days in a room at 50 ° C. and 90% humidity after curing. [UV irradiation conditions] Lamp: 80 W / cm high-pressure mercury lamp Lamp height: 10 cm Conveyor speed: 10 m / min Irradiation atmosphere: in the atmosphere Pass number: 5 times Initiator: bis (dodecylphenyl) iodonium hexafluoroantimonate (2. (Use 5wt%)

The pencil hardness of the surface of the cured film immediately after curing and after exposure to moisture was measured according to JIS K5400. The results of these measurements are shown in Table 2 below.

[0053]

[Table 2]

As can be seen from Table 2, the organosilicon compound A-1 of the present invention has good adhesion to various substrates immediately after curing. It is clearly superior to C-1. It is considered that this is because at least a part of the alkoxy group of the compound A-1 reacts with the hydroxyl group on the surface of the base material after coating or at the time of photocation polymerization. In addition, when looking at changes in physical properties due to moisture exposure, A-1 having an alkoxy group has improved both adhesion and hardness by moisture exposure, but C-1 having no alkoxy group has changed little. It turns out that there is no.

The present invention is not limited to the above-described specific embodiments, but may be variously modified within the scope of the present invention depending on the purpose and application.

[0056]

The photocationically polymerizable organosilicon compound of the present invention has an oxetanyl group having a high photocationic polymerization rate, and is therefore superior in photocationic polymerizability to epoxide type monomers. In addition, since it has an alkoxy group in addition to the oxetanyl group, before and / or after curing, the alkoxy group reacts with a hydroxyl group or the like on the substrate or the substrate surface to improve adhesion, or The groups can be condensed to improve the hardness of the cured film. Furthermore, it is also possible to introduce another functional group into the compound or its cured product by utilizing this alkoxy group, or to introduce a hydroxyl group into the cured film by hydrolysis of the alkoxy group to impart hydrophilicity. Furthermore, the organosilicon compound of the present invention can be easily produced by the production method of the present invention using inexpensive raw materials and catalysts.

[Brief description of the drawings]

FIG. 1 is an IR chart of a photocationically polymerizable organosilicon compound of the present invention produced according to Example 1.

FIG. 2 is an NMR chart of the photocationically polymerizable organosilicon compound of the present invention produced according to Example 1.

Claims (3)

[Claims] 1. A photocationically polymerizable organosilicon compound represented by the following structural formula (I). Embedded image (However, R ⁰ is an organic functional group having an oxetanyl group, R ¹ , R ² and R ³ are all alkyl groups, cycloalkyl groups or aryl groups, and n is 1 to 10,000.
Is a positive number. ) 2. The cationic photopolymerizable organosilicon compound according to claim 1, wherein R ⁰ is an organic functional group represented by the following structural formula (II). Embedded image (However, R ⁴ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R ⁵ is an alkylene group having 2 to 6 carbon atoms.) 3. The cationic photopolymerizable organic compound according to claim 1, wherein an addition reaction is carried out between the polysiloxane represented by the following structural formula (III) and an oxetane compound having an alkenyl terminal. A method for producing a silicon compound. Embedded image (However, R ¹ , R ² and R ³ are all alkyl groups, cycloalkyl groups or aryl groups, and n is 1 to 10,0
00 is a positive number. )