JPH10147750A - Preparation of partial condensate of alkyl silicate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-molecular-weight condensate of a lower alkyl silicate in the form of a stable liquid. SOLUTION: The preparation method comprises subjecting 1mol of an alkyl silicate monomer to hydrolysis and condensation in the presence of 0.70-1.25mol of water, a solvent (e.g. an alcohol) and an acid catalyst to form a condensate of a partial hydrolyzate, removing the alcohol as a by-product and the added solvent from the reaction solution, alkalifying the residual reaction solution, mixing it under agitation and removing a lower alkyl silicate monomer from the solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a partially condensed product of a lower alkyl silicate, which is widely used as an additive for paint, a binder in precision casting, and the like.

[0002]

2. Description of the Related Art Partial condensates such as lower alkyl silicates, for example, methyl silicate, ethyl silicate and propyl silicate, are prepared by adding a predetermined amount of water to a monomer, and in many cases, an acid catalyst such as hydrochloric acid, sulfuric acid or nitric acid. The hydrolysis and the condensation reaction are allowed to proceed in the presence of to produce a partial condensate called methyl silicate 51 or ethyl silicate 40 or the like.

[0003] These partial condensates are usually a mixture of a monomer to a multimer of about 7-mers, and such a mixture is characterized by enhancing the reactivity and the performance as a binder. However, in some cases, it is desirable that the molecular weight be as uniform as possible for a specific application. In addition, if the amount of water to be added is increased to obtain a condensate having a high degree of condensation, the reaction solution tends to gel and becomes extremely unstable.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to obtain an alkyl silicate partial condensate having a uniform molecular weight and a relatively high molecular weight stable partial condensate.

[0005]

According to the present invention, in preparing a partial condensate of a lower alkyl silicate, first, in the presence of a solvent and an acid catalyst, 0.70 to 1.25 per mole of an alkyl silicate monomer is used. After the hydrolysis and condensation reaction are caused by adding moles of water, and then the alcohol and by-products produced as by-products are removed from the reaction solution, the mixture is made alkaline, stirred, aged, and the lower alkyl formed by the disproportionation reaction. A method for producing the alkylate partial condensate, which comprises removing silicate by distillation. Hereinafter, the technical contents of the present invention will be described in detail.

As the lower alkyl silicate used in the present invention, methyl, ethyl, propyl silicate and the like are used. Sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid and the like can be used as the acid catalyst to be used, and its use ratio is suitably 0.001 to 0.1% by weight based on the raw material alkyl silicate.
The amount of water added depends on the desired condensate,
It is necessary that the generated partial condensate is in a range in which the liquid is maintained without gelling in a state where no solvent is added. For example, in the case of a methyl silicate monomer (tetramethyl orthosilicate), 0.70
Suitably, from mole to 1.1 mole of water is added. If too much water is added, partial hydrolysis will proceed too much and can no longer be present in a homogeneous liquid in the absence of solvent. In the case of ethyl silicate (tetraethyl orthosilicate), it is appropriate to add 0.75 mol to 1.25 mol of water to 1 mol of the monomer. 1.25
If water is added in excess of moles, partial hydrolysis will proceed too much in the same manner as described above, and it will no longer be possible to exist as a uniform liquid in the absence of a solvent.

The temperature at which the alkyl silicate is partially hydrolyzed in the presence of an acid catalyst is from room temperature to the boiling point of the solvent used. Water may be added all at once or added dropwise. Alcohol is most suitable as the solvent to be used, and for example, methanol can be used for methyl silicate, and ethanol can be used for ethyl silicate.
The reaction time is suitably from 90 minutes to 3 hours. The reaction solution obtained here is a transparent alkyl silicate partial hydrolyzate containing alcohol and the like generated as a result of hydrolysis, and is a mixture of dimer to heptamer condensate of alkyl silicate. A small amount of unhydrolyzed monomer may remain. The solvent used as a diluent when adding by-product alcohol and / or water for hydrolysis is removed from the reaction solution. Further, the acid used as a catalyst contained in the reaction solution can be removed by a neutralization method or a method of passing through an ion exchange resin layer or the like, which may be performed before or after removing the alcohol or the solvent. When the salt formed by the neutralization method is harmless, the neutralization method is simple.

In the present invention, an alkali is further added to the neutralized partial hydrolyzate to make it an alkali side, and the mixture is aged at room temperature to 140 ° C. with stirring and ripening. In this process, a kind of disproportionation reaction occurs, and the amount of the alkyl silicate monomer in the reaction solution increases, while the amount of the higher molecular weight condensate also increases. As a result, if the monomer is removed from the reaction solution by distillation or the like, a low molecular weight condensate or a high molecular weight condensate having few cyclic condensates can be obtained in a stable state. This condensate is a transparent liquid without any solvent, and does not gel for a long time. Hereinafter, specific examples will be described. Parts and% are parts by weight and% by weight unless otherwise specified.

Example 1 Methyl silicate (tetramethyl orthosilicate) 1
To 00 parts, 12 parts of methanol and 0.01% sulfuric acid catalyst were added as a solvent, and 8.9 parts of ion-exchanged water (0.75 mol per 1 mol of monomer) was added dropwise over 3 hours. Stirred for hours. Thereafter, the alcohol by-produced and the added alcohol were distilled off. The obtained partially hydrolyzed condensate was deoxidized through an ion exchange resin layer. The number average molecular weight of the obtained partial condensate was 332. In this case, the content of the methyl silicate monomer was 5.0 area%.
(GLC). Triethylamine (1.0%) was added to the partially hydrolyzed condensate, and the mixture was stirred at 110 ° C. for 3 hours, and low-boiling substances were distilled off under reduced pressure. The number average molecular weight of the obtained condensate was 555, which was considerably higher than that of the initially obtained condensate. However, the solution was stable and no tendency to gel was observed.

Example 2 In the same manner as in Example 1, a partially hydrolyzed condensate of methyl silicate having a number average molecular weight of 332 was obtained. 1.1.
1.0% of a × 10 −3 mol / l sodium methylate methanol solution was added, and the mixture was stirred at 95 ° C. for 3 hours. Then, low-boiling substances were distilled off under reduced pressure. The obtained condensate had a number average molecular weight of 856, which was considerably higher than that of the initially obtained condensate, but the solution was stable without any solvent addition, and no tendency to gel was observed. .

Example 3 Ethyl silicate (tetraethyl orthosilicate) 1
In 100 parts, 10.9 parts of ethanol and 0.0
A 2% sulfuric acid catalyst was added, and 6.7 parts of ion-exchanged water (0.78 mol per 1 mol of monomer) was added dropwise over 3 hours and 30 minutes, and the mixture was further stirred for 30 minutes. Thereafter, the alcohol by-produced and the added alcohol were distilled off. The obtained partial hydrolyzate was deoxidized through an ion exchange resin layer. The number average molecular weight was 788. At this time, the content of the ethyl silicate monomer was 4.1 area% (GLC). 2.6% of triethylamine was added to the partially hydrolyzed condensate, and the mixture was stirred at 100 ° C. for 3 hours. afterwards,
Low boiling substances were distilled off under reduced pressure. The pressure reduction condition was 6.7 × 10 −7 Pa, and the bath temperature was 150 ° C. The number average molecular weight of the obtained condensate was 924, which was considerably higher than that of the initially obtained condensate. However, the solution was stable and no tendency to gel was observed.

Example 4 In the same manner as in Example 2, a partially hydrolyzed condensate of ethyl silicate having a number average molecular weight of 788 was obtained. To this partial hydrolyzate, 1.0% of a solution of 1.1 × 10 −4 mol / l sodium ethylate in ethanol was added, and the mixture was stirred at 100 ° C. for 3 hours. . The number average molecular weight of the obtained condensate was 1510, which was considerably higher than that of the initially obtained condensate, but the liquid was stable without any solvent addition, and no tendency to gel was observed. .

According to the present invention, a high molecular weight condensate of a lower alkyl silicate can be produced in a stable state without gelling without other solvents. Such a high molecular weight condensate is suitable for a special paint, a binder thereof, or a silicone raw material.

Claims (5)

[Claims] In preparing a partial condensate of a lower alkyl silicate, water is first added by adding 0.70 to 1.25 mol of water to 1 mol of an alkyl silicate monomer in the presence of a solvent and an acid catalyst. After causing decomposition and condensation reactions, and then removing alcohol and solvent by-produced from the reaction solution,
A method for producing the alkylate partial condensate, which comprises making the mixture alkaline, stirring and aging it, and distilling off lower alkyl silicate produced by the disproportionation reaction. 2. The method according to claim 1, wherein an amine compound is used as a compound for making the reaction solution alkaline. 3. The process according to claim 1, wherein sodium alcoholate is used as the compound for making the reaction solution alkaline. 4. The process according to claim 1, wherein the acid catalyst is removed from the solution after the hydrolysis and condensation reaction, and then an amine compound is added to make the solution alkaline. 5. The method according to claim 1, wherein the acid catalyst is removed from the solution after the hydrolysis and condensation reaction, and then sodium alcoholate is added to make the solution alkaline.