JPH0859838A - Composition and method for decomposing polysiloxane - Google Patents

Abstract

PURPOSE: To decompose and remove a silicone rubber, a silicone resin, etc., under mild conditions by using a mixture comprising an orthoester, an active hydrogen compd.. and an acid catalyst. CONSTITUTION: A mixture comprising an orthoester, an active hydrogen compd., and an acid catalyst is used as a compsn. for decomposing a polysiloxane in the form of an oil, a raw or vulcanized rubber, a varnish, a resin, or a polysilsesquioxane. The orthoester is pref. methyl orthoformate and is used in an amt. of 0.5mol or higher based on 1mol of Si-O-Si bond. The active hydrogen compd. (e.g. a hydroxyl compd.) is pref. methyl alcohol and is used in an amt. of 0.01mol or higher, pref. 0.5mol or higher. And, the acid catalyst is pref. sulfuric acid and is used in an amt. of 0.01-1wt.%. pref. 0.05-0.5wt.%. The compsn. can decompose a polysiloxane under mild conditions by bringing them into contact with each other by applying, immersing, etc.. and is thus effective e.g. for removing a thin polysiloxane film.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composition for decomposing a polysiloxane into a silicon compound having a lower molecular weight and a method for decomposing the polysiloxane.

[0002]

2. Description of the Related Art Polysiloxane is chemically stable, and in order to decompose it, it is necessary to treat it at a high temperature or in the presence of an alkali and an acid at a high temperature.

[0003]

However, these methods require a high temperature or use an alkali or an acid at a high temperature, and there is a problem that the polysiloxane cannot be decomposed under mild conditions. The invention of the present application solves the above-mentioned drawbacks of the prior art, and provides a composition and a decomposition method capable of decomposing polysiloxane even under mild conditions, thereby reusing silicon rubber and a polysiloxane thin film on a substrate. The purpose is to facilitate the removal of impurities, surface modification by partial decomposition of the silicon surface, and the like.

[0004]

The inventors of the present application have studied various methods for achieving such an object, and as a result, have found that polysiloxane is composed of an orthoester, an active hydrogen group-containing compound, and an acid catalyst. It was found that the decomposition of polysiloxane proceeds even at room temperature by bringing it into contact with the composition, and the invention of this application was completed.

The polysiloxane decomposed by the composition of the present invention is a so-called silicone oil,
Examples thereof include, but are not limited to, silicone raw rubber, vulcanized silicone rubber, silicone varnish, silicone resin, and polysilsesquioxane.

As the substituent on silicon, a hydrogen atom, an alkyl group, a substituted alkyl group such as a chloromethyl group, an alkenyl group such as a vinyl group and an allyl group, an aryl group such as a phenyl group and a tolyl group, Examples thereof include, but are not limited to, an alkoxy group such as a methoxy group and an ethoxy group.

Examples of the orthoester of the composition of the present invention include methyl orthoformate, ethyl orthoformate, propyl orthoformate, butyl orthoformate, octyl orthoformate, orthoformate, methyl orthoacetate, ethyl orthoacetate, orthoacetate. Examples thereof include orthoacetic acid esters such as propyl, butyl orthoacetate, and octyl orthoacetate, but are not limited thereto. Among these, orthomethyl esters such as methyl orthoformate are particularly preferable in terms of reactivity. The amount to be mixed varies depending on the purpose of the decomposition, but in the case of promoting the decomposition in a relatively large amount, 0.5 mol or more of the orthoester is preferably used with respect to 1 mol of the Si-O-Si bond of the polysiloxane. , 1.0 mol or more is particularly preferable.

The active hydrogen group-containing compound of the composition of the present invention is a compound containing a hydroxyl group, a carboxyl group, a mercapto group, an amino group or the like in the molecule, and specifically, water,
Examples thereof include alcohols, carboxylic acids, mercaptans and amines, with water, alcohols and carboxylic acids being particularly preferred. Examples of the alcohol used in the present invention include monohydric alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol and n-butanol, and polyhydric alcohols such as ethylene glycol, propylene glycol and glycerin. However, the present invention is not limited to these. Among these,
Methyl alcohol and ethyl alcohol are preferable, and methyl alcohol is particularly preferable. Examples of the carboxylic acid used in the invention of the present application include, but are not limited to, formic acid, acetic acid, propionic acid, acrylic acid and the like. Further, since the amount to be mixed affects the rate of decomposition, 0.01 mol or more is preferable, and 0.5 mol or more is particularly preferable, relative to 1 mol of Si-O-Si bond of polysiloxane.

Examples of the acid catalyst include sulfuric acid, hydrochloric acid, phosphoric acid, acetic acid and aluminum chloride, but the acid catalyst is not limited thereto. Of these, sulfuric acid and hydrochloric acid are preferable, and sulfuric acid is particularly preferable. Further, the amount to be mixed is preferably 0.01 to 1.0% (by weight) in the composition for decomposition,
0.05 to 0.5% (weight) is particularly preferable.

In the decomposition method of the present invention, an orthoester, an active hydrogen group-containing compound and an acid catalyst are mixed in advance to prepare a mixed solution, and the mixed solution is brought into contact with polysiloxane. , By immersion,
This is performed by adding polysiloxane to the mixed solution.

According to the invention of this application, polysiloxane can be decomposed under mild conditions. Therefore, in reusing silicon rubber, removing polysiloxane thin film on a substrate, surface modification by partial decomposition of silicon surface, etc. It has an excellent effect.

[0012]

EXAMPLES Next, examples and comparative examples will be specifically described, but the invention of the present application is not limited thereto. Example 1 113.56 g (1.0%) of methyl orthoformate in a glass container.
70 mol), 34.97 g of methanol (1.091 m)
ol) and 0.1 g (1 mmol) of sulfuric acid were added and stirred to prepare a mixed solution. Immerse 4.4 g of vulcanized silicone rubber molded product in the dropper cap at room temperature.
Left for days. When I tried to pinch the dropper cap with tweezers, it fell apart. After standing for another 3 days, the supernatant was measured by gas chromatography, and it was found that dimethyldimethoxysilane had been formed.

Example 2 A silicone rubber sheet piece, which is a vulcanized rubber molded product, was immersed in the same liquid mixture as in Example 1. Observation after 2 days at room temperature revealed that the surface of the silicone rubber sheet had dissolved and changed into a muddy state.

Examples 3 to 4 and Comparative Examples 1 to 3 Methyl orthoformate, methanol, water and sulfuric acid were weighed in glass containers to prepare mixed solutions. A dropper cap weight of 1.8 g, which is a molded product of vulcanized silicone rubber, is dipped in these mixed liquids and allowed to stand at room temperature for 2
Left for days. The results are as shown in Table 1.

Table 1 Examples Comparative Examples 3 4 1 2 3 Methyl orthodiate (g) 21.8 21.2 21.3--(mol) 0.21 0.20 0.20--Methanol (g) 6.4--24.8-(mol) 0.20--0.77 -Water (g)-1.8--29.8 (mol)-0.10--1.6 Sulfuric acid (mg) 23 23 23 23 23 (mmol) 0.23 0.23 0.23 0.23 0.23 Room temperature immersion No prototype 50% of prototype No change No change No change 2 days later complete collapse collapse

Example 5 Methylhydrogin polysiloxane (K, manufactured by Shin-Etsu Chemical Co., Ltd.)
F99) 10.09g (0.157mo in SiH conversion)
l) is methyl orthoformate 8.41 g (79.2 mmo)
l), 5.21 g (0.163 mol) of methanol, and 20 mg (0.20 mmol) of sulfuric acid were added, and the mixture was stirred at room temperature. After 1 hour, 3.88 g of dimethoxymethylsilane (36.
5 mmol, 23% yield based on Si-H). When measured 21 hours later, the dimethoxymethylsilane was 5.28 g (49.7 mmol, 32 based on Si-H standard).
% Yield). For gas chromatography,
A component of 1,3-dimethoxy, 1,3 dimethytyldisiloxane (dimer) was observed. Moreover, the gas chromatography peak estimated to correspond to a trimer and a tetramer was seen.

Example 6 2.96 g (44.1 m) of powder of ladder-type polysiloxane (polysilsesquioxane, glass resin GR650)
mol, Si standard), methyl orthoformate 7.33 g
(69.1 mmol), 3.98 g of methanol (124
mmol) and sulfuric acid 0.06 g (0.6 mmol) were added and dissolved to obtain a uniform solution. The reaction did not proceed after 1 day at room temperature, but methyltrimethoxysilane was found to be 3.
90 g (28.6 mmol, 65% yield based on Si) was produced. It was estimated from gas chromatography that the remaining components were mostly dimers.

Example 7 3.20 g (24.8 m) of powder of ladder-type polysiloxane (polysilsesquioxane, glass resin GR950)
mol, Si standard) 4.11 g of methyl orthoformate (3
8.7 mmol), 2.41 g of methanol (75.2 m)
mol) and 0.04 g (0.4 mmol) of sulfuric acid were added and dissolved to obtain a uniform solution. This was left at room temperature, and 22 days later, when measured by gas chromatography,
21.2g (10.7m) of phenyltrimethoxysilane
mol, 43% yield based on Si).

[0019]

The decomposition by the composition of the present invention has an excellent effect that polysiloxane can be decomposed without using an alkali or an acid at a high temperature because the decomposition proceeds even at room temperature. Therefore, by the decomposition method under mild conditions by the composition of the present invention, reuse of silicone rubber,
It is possible to exert excellent effects such as removal of the polysiloxane thin film on the base material and surface modification by partial decomposition of the silicon surface.

Claims (6)

[Claims] 1. A composition for decomposing a polysiloxane, which comprises a mixture of an orthoester, an active hydrogen group-containing compound and an acid catalyst. 2. The polysiloxane decomposing composition according to claim 1, wherein the orthoester is an orthomethyl ester. 3. The active hydrogen group-containing compound is an alcohol,
Water or carboxylic acid, Claims 1 and 2 characterized by the above-mentioned.
The composition for decomposing a polysiloxane according to 1. 4. The polysiloxane decomposing composition according to claim 1, wherein the alcohol is methyl alcohol. 5. The composition for decomposing polysiloxane according to claim 1, wherein the acid is sulfuric acid. 6. A method for decomposing a polysiloxane, which comprises contacting the polysiloxane with a mixture of an orthoester, an active hydrogen group-containing compound and an acid catalyst.