JP2657454B2 - Method for producing organopolysiloxane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing an organopolysiloxane in which an organic group is introduced into a molecular chain terminal of an organopolysiloxane obtained by polymerization using an acid catalyst and the acid catalyst is neutralized simultaneously. About the method.

[0002]

2. Description of the Related Art In general, high molecular weight organopolysiloxanes are produced by polymerizing cyclic low molecular weight siloxane or the like using an acid or basic catalyst. As these catalysts, generally, sodium hydroxide, potassium hydroxide, tetraalkylammonium hydroxide or their siliconates, hydrochloric acid, sulfuric acid and the like are widely used.

[0003]

However, since the polymerization using the above-mentioned catalyst is a so-called equilibrium reaction, it not only cuts the bond of the cyclic siloxane as the starting material but also forms the linear organopolysiloxane formed. Breakage of the siloxane bond also occurs. For this reason, there is a problem that the obtained organopolysiloxane contains a relatively low molecular weight organopolysiloxane.

[0004] Accordingly, various polymerization methods have been studied in which the production of low-molecular-weight siloxane is small. For example, JP-A-3-179
No. 027 discloses that a high molecular weight organopolysiloxane can be obtained by performing a condensation reaction by reacting a catalyst comprising an acidic compound with an organosiloxane having a hydroxy group. It has been clarified that the condensation reaction is carried out without breaking the siloxane bond by using

By the way, when polymerization is carried out by acting an acid catalyst on an organosiloxane having a hydroxy group, the obtained organopolysiloxane naturally contains the acid used as a catalyst. When such an acid catalyst is contained in the organopolysiloxane, the siloxane bond of the organopolysiloxane is cleaved, and undesirable low-molecular-weight cyclic siloxane is formed, thereby deteriorating the stability of the organopolysiloxane.

Therefore, in the above-mentioned method, it is necessary to carry out neutralization after polymerization. However, in this neutralization step, siloxane bonds are broken, and as a practical matter, it is necessary to avoid the formation of low molecular weight organopolysiloxane. Has become difficult. In addition, when an alkali metal hydroxide or the like is used as a neutralizing agent, the terminal of the organopolysiloxane is terminated with a hydroxyl group, and when an organic group is introduced into the terminal, an additional step other than this neutralization step is performed. Is required.

Therefore, an object of the present invention is to suppress the production of organopolysiloxane having a low molecular weight as much as possible, and at the same time, to simultaneously carry out neutralization of the catalyst and introduction of an organic group to the terminal of the molecular chain. An object of the present invention is to provide a method for producing an organopolysiloxane having a molecular weight.

[0008]

According to the present invention, a process for polymerizing a hydroxy group-containing organosiloxane using an acid catalyst having a Pka of 3 or less, and the organopolysiloxane obtained in the above process are described below. General formula (1): R ₃ SiNHSiR ₃ (1) In the formula, R may be the same or different, and is a mixture of hexaorganodisilazane represented by an unsubstituted or substituted monovalent hydrocarbon group. A step of neutralizing the acid catalyst and introducing a group R to a molecular chain terminal of the organopolysiloxane obtained in the step, thereby producing an organopolysiloxane. Provided.

[0009]

That is, the present invention provides neutralization of an acid catalyst and molecular chain by adding hexaorganodidisilazane to a condensation polymerization product of a hydroxy group-containing organosiloxane using an acid catalyst having a Pka of 3 or less. Introduction of an organic group to the terminal,
This is based on a novel finding that the siloxane bond can be effectively performed without breaking the siloxane bond.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Starting material In the method of the present invention, the starting material is represented by the following general formula (2):

Embedded image Wherein R ¹ and R ² may be the same or different;
An unsubstituted or substituted monovalent hydrocarbon group, wherein n is 2 to
An organopolysiloxane having a silanol group at both ends of the molecular chain represented by an integer of 3,000 is used.

In the general formula (2), R ¹ and R
² is an unsubstituted or substituted monovalent hydrocarbon group, specifically, an alkyl group such as a methyl group, an ethyl group, and a propyl group, an alkenyl group such as a vinyl group and an allyl group, and a cycloalkyl group such as a cyclohexyl group. , An aryl group such as a phenyl group and a tolyl group, an aralkyl group such as a benzyl group and a phenylethyl group, and a group in which part or all of the hydrogen atoms of these groups are substituted with a halogen atom, a cyano group, etc., for example, a chloromethyl group , Trifluoropropyl group, cyanoethyl group,
Examples thereof include an α-cyanophenylethyl group.

N is an integer representing the degree of polymerization, and 2
3,000, but from the viewpoint of economy, preferably 10 to
It is an integer of 1,000.

In the present invention, among the above-mentioned organopolysiloxanes, those obtained by removing a cyclic siloxane which does not participate in polymerization by removing strips or the like as much as possible are preferably used from the viewpoint of suppressing the amount of low molecular siloxane.

Polymerization Step In the present invention, the polycondensation of the above-mentioned organosiloxane having both ends blocked by a hydroxy group is carried out by Pka (2
(0 ° C.) using an acid catalyst of 3 or less. Even if an acid catalyst is used, when Pka is larger than 3, polycondensation does not proceed quickly and is unsuitable. The acid catalyst having a Pka of 3 or less is a known one which has been conventionally used for the polymerization of organopolysiloxane, and representative examples thereof include the following.

CF ₃ COOH, FCH ₂ COOH, C ₃
F ₇ COOH, C ₃ F ₇ OCF (CF ₃ ) COOH, C
_{3 F 7 OCF (CF 3)} CF 2 OCF (CF 3) COO
H, ClCH ₂ COOH, BrCH ₂ COOH, CH ₂
(COOH) ₂

In the present invention, the above-mentioned acid catalyst is used in an amount of 0.0001 to 10 parts by weight, preferably 0.001 to 0.1 part by weight, per 100 parts by weight of the above-mentioned organosiloxane having both ends blocked with a hydroxy group. Is done.

In the polycondensation using an acid catalyst, the above-mentioned organosiloxane and the acid catalyst are mixed, and usually at 25 to 200 ° C.
By heating to a temperature of
An organopolysiloxane having a high degree of polymerization and a prolonged chain length can be obtained without breaking the siloxane bond. The terminal of this organopolysiloxane is silanol.

Neutralization and Terminal Blocking Step According to the present invention, after the above-mentioned polycondensation reaction is completed, the reaction system is represented by the above general formula (1), that is, R ₃ SiNHSiR ₃ (1). By adding and mixing hexaorganodisilazane, the terminal silanol of the produced high polymerization degree organopolysiloxane is blocked simultaneously with neutralization of the acid catalyst. That is, the terminal silanol of the organopolysiloxane obtained in the above step and the hexaorganodisilazane react with each other according to the following formula: 2 · {SiOH + R ₃ SiNHSiR ₃ }> 2 · {SiOSiR ₃ + NH ₃ Silanol is blocked with a triorganosilyl group, and at the same time, NH ₃ generated here causes
The neutralization of the acid catalyst is performed.

In the general formula (1), R is an unsubstituted or substituted monovalent hydrocarbon group. Specific examples thereof are the same as those exemplified for R ^{1 in the} general formula (2). Groups. In the present invention, particularly preferred groups are an alkyl group, a vinyl group and the like.

In the present invention, since the above-mentioned hexaorganodisilazane is used to neutralize the acid catalyst and block the ends of the organopolysiloxane, it is necessary to use at least an equimolar amount or more with respect to the acid catalyst. It is used in an amount of 0.01 to 5 parts by weight, preferably 0.05 to 2 parts by weight, based on 100 parts by weight of the organosiloxane obtained in the polymerization step. If the amount is smaller than this, it is difficult to effectively perform end blocking, and if used in large amounts,
Not only is it economically disadvantageous, but the stripping process is time-consuming, and siloxane bonds are broken, resulting in low molecular weight organopolysiloxanes.

Neutralization and terminal blocking with hexaorganodisilazane are usually carried out simply by adding hexaorganodisilazane to the reaction system and stirring uniformly, but if necessary, the boiling point of hexaorganodisilazane may be reduced. (Usually 20
(Lower than 0 ° C.). When heated to a temperature higher than this, hexaorganodisilazane is scattered and the reaction does not proceed effectively. In addition, the siloxane bond is cut off, and a low molecular weight organopolysiloxane is formed.

After the completion of the reaction, hexaorganodisilazane and the like are excessively removed by heating, depressurizing, or the like, to obtain a desired high molecular weight organopolysiloxane. The terminal of this organopolysiloxane is a triorganosilyl group,
That is, it is blocked by an R ₃ Si group.

[0023]

In the following examples, Dn means the degree of polymerization,
For example, D3 indicates that the degree of polymerization is 3. The viscosity indicates a value measured at 25 ° C.

Example 1 2,000 g of polydimethylsiloxane having a hydroxy group at both ends (viscosity: 720 cSt) 2.0 g of C ₃ F ₇ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) COOH was mixed. After stirring at 2 ° C. for 2 hours, both ends were terminated with a hydroxy group, and the number average molecular weight was 3.9.
× 10 ⁵ polydimethylsiloxane was obtained. When the content of the low-molecular siloxane in the polydimethylsiloxane was measured by gas chromatography, D3 to D2
0 was 950 ppm.

100 g of the obtained polydimethylsiloxane
Then, 0.5 g of hexamethyldisilazane was added thereto, and the mixture was stirred at room temperature for 2 hours. Then, 15 minutes under nitrogen gas ventilation.
By maintaining the temperature at 0 ° C., excess hexamethyldisilazane was removed to obtain polydimethylsiloxane having both ends blocked with a trimethylsilyl group. The low molecular siloxane (D3 to D20) contained in the polydimethylsiloxane is
It is 1030 ppm, which is almost the same as that after completion of the previous polymerization step, and it can be seen that siloxane bond breakage hardly occurs in this neutralization and terminal blocking step.

A 10% strength toluene solution was prepared using polydimethylsiloxane before and after the hexamethyldisilazane treatment, and the time-dependent change in viscosity at 25 ° C. was measured. Table 1 shows the results.

[0027]

[Table 1]

From the above results, it can be seen that the viscosity of the toluene solution of polydimethylsiloxane before the hexamethyldisilazane treatment is unstable, and the viscosity decreases with time. This is presumably because the acid catalyst was present in the polymer without being neutralized, and the siloxane bond was cleaved. On the other hand, in the case where the hexamethyldisilazane treatment is performed according to the present invention, the viscosity is stably maintained. That is, it is considered that since the acid catalyst present in the polymer is neutralized, the siloxane bond is not cleaved.

Further, 100 g of a 10% toluene solution of polydimethylsiloxane treated with hexamethyldisilazane.
Was added with 0.5 g of tetramethoxysilane and 0.01 g of tetrapropyl titanate, but no increase in viscosity was observed. This indicates that almost no hydroxyl group exists at the terminal of the polymer, and that a trimethylsilyl group has been introduced.

Example 2 0.3 g of hexamethyldisilazane was added to 100 g of the polydimethylsiloxane obtained in Example 1 before the hexamethyldisilazane treatment, and the mixture was stirred for 1 hour while maintaining a temperature of 60 ° C. Was. Then, the mixture was heated to 150 ° C. and an excess amount of hexamethyldisilazane was removed under a stream of nitrogen gas. As a result, polydimethylsiloxane (number average molecular weight: 3.9 × 10 ⁵ ) having both ends blocked by a trimethylsilyl group was obtained. Was. The D3 to D20 content was 1100 ppm.

Example 3 In Example 1, instead of hexamethyldisilazane,
The same operation as in Example 1 was carried out except that 0.6 g of 1,3-divinyl-1,1,3,3-tetramethyldisilazane was used, and the end was blocked with a vinyldimethylsilyl group. Polydimethylsiloxane was obtained. The number average molecular weight of this polymer is 3.9 × 10 ⁵ , and the vinyl group content is
0.0015 mol / 100 g, D3-D20 content was 1050 ppm.

Comparative Example 1 To 100 g of the polydimethylsiloxane obtained in Example 1 before the hexamethyldisilazane treatment, 1.0 g of an aqueous sodium hydroxide solution (NaOH: 0.05 g) was added, and the mixture was stirred at room temperature for 2 hours. Was. Next, this reaction system was heated to 150 ° C. to remove water, and polydimethylsiloxane having both ends blocked with hydroxyl groups was obtained. In this polymer, D3 ~
The low molecular siloxane of D20 was contained at 6300 ppm, and the content of the low molecular siloxane was remarkably increased as compared with the raw material, indicating that the siloxane bond was broken during the reaction.

[0033]

According to the present invention, a high molecular weight organopolysiloxane in which both ends of the molecular chain are blocked by a triorganosilyl group can be easily obtained. Moreover, cleavage of siloxane bonds during the production process is effectively suppressed, and the content of low molecular siloxane in the resulting organopolysiloxane is extremely small.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kaio Inoue 1-10 Hitomi, Matsuida-machi, Usui-gun, Gunma Prefecture Inside Silicone Electronics Materials Research Laboratory, Shin-Etsu Chemical Co., Ltd. (72) Inventor Masaharu Takahashi Matsui, Usui-gun, Gunma Prefecture Hitomi Tamachi 1-10 Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Research Laboratory (56) References JP-A-62-13437 (JP, A) JP-A-60-54392 (JP, A)

Claims (1)

(57) [Claims] 1. The method of claim 1, wherein the hydroxy group-containing organosiloxane is
A process in which Pka is polymerized using an acid catalyst having 3 or less, and the organopolysiloxane obtained in the above process is added to the following general formula (1): R ₃ SiNHSiR ₃ (1) May be an unsubstituted or substituted monovalent hydrocarbon group, by mixing hexaorganodisilazane represented by the above, neutralization of the acid catalyst, and to the molecular chain terminal of the organopolysiloxane Group R
And a process for introducing an organic polysiloxane.