JP2002241500A - Process for curing of organopolysiloxane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easily conductible curing process in which curing speed is rapid, and viscosity does not increase so much, and provide forth a catalyst. SOLUTION: The process for curing organopolysiloxane, conducted by condensation reaction of an organopolysiloxane having hydroxy groups at the both molecular ends with a curing agent, is characterized by using as the curing catalyst a titanium chelate compound and a divalent tin compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for curing an organopolysiloxane and a catalyst for curing the same.

[0002]

2. Description of the Related Art When an organopolysiloxane is cured at room temperature with a curing agent to obtain a rubber elastic body, there are typically a condensation reaction type and an addition reaction type due to its reaction mechanism. Among them, in the condensation reaction type, the curing reaction proceeds by contact with moisture in the air in the presence of a catalyst. The resulting room-temperature-curable liquid rubber (RTV silicone rubber) is widely used as an elastic adhesive or a coating agent in the electric / electronics and automotive industries, or as a sealing agent for building materials and the like.

In this condensation reaction, an alkyltin compound such as dibutyltin dilaurate (DBTDL) is usually used. The alkyltin compound is a compound in which tin and carbon are directly bonded, and tributyltin is known as a toxic substance which is likely to cause an abnormality in an ecosystem, and its use is prohibited. On the other hand, alkyltin compounds such as dibutyltin dilaurate have a problem that a small amount of tributyltin or the like is contained as an impurity in the synthesis process.

As a curing catalyst other than tin, a titanium catalyst may be used, but the curing speed is slower and more expensive than the alkyltin catalyst. Further, metal carboxylate salts other than tin and titanium may be used, but they have a disadvantage that the curing rate is lower than that of alkyltin compounds and titanium-based catalysts. Under these circumstances, it has been proposed to use a tin-based catalyst and an alkoxytitanium in combination as a catalyst system in which a plurality of metal compounds are used in combination in order to accelerate the curing rate (Japanese Patent Laid-Open No. 11-6110).
No. 0). However, this catalyst system can improve the curing rate, but when mixed with the reaction components, organopolysiloxane and alkoxysilane, the viscosity of the solution increases rapidly (thickening). There is a difficult point that it is very difficult to use in the work of injecting into a mold or a mold.

[0005]

Accordingly, the present inventors have conducted various studies in order to find a curing method and a catalyst which have a high curing speed, are less thickened, and are easy to carry out.

[0006]

According to the present invention, a titanium chelate compound and a divalent tin compound are used in combination as a curing catalyst when an organopolysiloxane having hydroxyl groups at both molecular terminals is condensed with a curing agent and cured. A method for curing an organopolysiloxane, and a catalyst for curing an organopolysiloxane comprising a titanium chelate compound and a divalent tin compound.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
Examples of the organopolysiloxane used in the present invention include organopolysiloxanes having hydroxyl groups at both molecular ends, and having two or more hydroxyl groups in the molecule, such as α, ω-dihydroxypolydimethylsiloxane, α , Ω-dihydroxypolydivinylsiloxane, α, ω-dihydroxypolydiphenylsiloxane, α, ω-dihydroxypolydifluoromethylsiloxane, and the like.

On the other hand, the curing agent that undergoes a condensation reaction with the above-mentioned organopolysiloxane can be selected from known curing agents of dealcohol type, deacetic acid type, deoxime type, deacetone type or deamide type. The dealcoholated type is most suitable in the present invention because it is inherently slow in curing but is non-toxic / odorless and non-corrosive. In this case, an alkoxysilane is used, and an alkoxysilane having three or four alkoxy groups bonded to a silicon atom in one molecule is preferable. For example, methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, Methyltriethoxysilane, ethyltrimethoxysilane,
Octyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane and the like can be mentioned.

In the present invention, a titanium chelate compound and a divalent tin compound are used in combination as a curing catalyst when the above organopolysiloxane is condensed with the above curing agent and cured. As the titanium chelate compound, a compound having a titanium atom as a ligand with β-diketones, β-ketoesters and / or oxycarboxylic acids as ligands is suitable. Such compounds include, for example, diisopropoxytitanium bis (ethylacetoacetate), triisopropoxytitanium ethylacetoacetate, diisopropoxytitanium bis (methylacetoacetate), triisopropoxytitanium methylacetoacetate, diisopropoxytitanium bis (acetylacetoacetate) Nitrate), triisopropoxytitanium acetylacetonate, dibutoxytitanium bis (ethylacetoacetate), tributoxytitanium ethylacetoacetate, dibutoxytitanium bis (methylacetoacetate), tryptoxytitanium methylacetoacetate, dibutoxytitanium bis (acetyltoacetate) Nitrate), tributoxytitanium acetylacetonate, dichlorotitanium bis (ethyl acetoacetate), dichlorotitanium bis Methyl acetoacetate), diisopropoxy bis (ethyl tartrate), diisopropoxy bis (ethyl lactate), diisopropoxy bis (triethyl citrate)
And the like. Among these, a titanium compound obtained by reacting an alkoxytitanium with a β-ketoester is particularly preferably used.

On the other hand, as the divalent tin compound, a tin (II) carboxylate compound is suitably used and usually has 2 to 24 carbon atoms, preferably 6 to 18 carbon atoms. Examples of such compounds include tin octylate, tin caprylate, tin laurate, tin stearate, tin oleate, tin linoleate, tin linolenate, and tin naphthenate.

In the present invention, when the organopolysiloxane is cured by a condensation reaction with a curing agent, the curing agent is used in an amount of 1 to 10 parts by mass and the curing catalyst is used in an amount of 0.01 to 10 parts by mass based on 100 parts by mass of the organopolysiloxane. It is preferable to use about 2 parts by mass. The mass ratio of the titanium chelate compound and the divalent tin compound used together as the curing catalyst is
Usually 1:10 to 1: 0.01, preferably 1: 1 to 1:
Selected from 0.05. If the mass ratio of the divalent tin compound is less than 0.01, the curing rate tends to be slow, while if it exceeds 10, thickening immediately after mixing tends to be recognized.

As described above, in the method of the present invention, an organopolysiloxane curing catalyst containing the above-mentioned titanium chelate compound and divalent tin compound is used as a curing catalyst. The titanium chelate compound and the divalent tin compound can be produced by a conventional method, and the mass ratio is usually 1:10 to 1: 0.01. The organopolysiloxane curing catalyst comprising the titanium chelate compound and the divalent tin compound may be mixed in advance or may be mixed at the time of use.

[0013]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.
In addition, the compounding in an Example and a comparative example shows a mass part. Examples 1 to 13 and Comparative Examples 1 to 6 Organopolysiloxane was put in a 200 mL container under an atmosphere of 25 ° C. and a relative humidity of 50% according to the formulation shown in Table 1, and the curing agent was mixed in advance. And a curing catalyst were added and mixed with a stir bar for 5 seconds to cure the organopolysiloxane. The change in viscosity at that time was observed, and those with little increase in viscosity were rated as ○, those with some increase in viscosity were rated as △, and those with large increase in viscosity were rated as x. Then, after the completion of the mixing, the mixture was allowed to stand in an atmosphere of 25 ° C. and 50% relative humidity to obtain a silicone rubber. In this case, the time when it was confirmed that the surface was in a dry state by touching the surface with a finger was defined as a finger touch drying time (minute) and was used as an index of a curing speed. Table 1 also shows the results.

Similarly, a curing reaction was carried out for Comparative Examples 1 to 6 according to the formulation shown in Table 1, and the results were combined with the results shown in Table 2.
Shown in

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

According to the method for curing an organopolysiloxane according to the present invention, the following effects can be achieved. (1) Do not use an alkyltin compound that is concerned about environmental problems. (2) A curing speed equivalent to the conventional method using an alkyltin compound as a curing catalyst can be obtained.

(3) Since there is almost no increase in viscosity at the time of mixing, it is very easy to use in the production process of the silicone sealant and the injection process into the window frame or mold.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J035 BA01 CA05N CA05U CA051 CA14U CA142 FB05 LB02 LB03

Claims (8)

[Claims] 1. An organopolysiloxane comprising a combination of a titanium chelate compound and a divalent tin compound as a curing catalyst when an organopolysiloxane having hydroxyl groups at both molecular terminals is condensed with a curing agent and cured. Curing method. 2. The method according to claim 1, wherein the curing agent is a dealcohol type, a deacetic acid type,
The method for curing an organopolysiloxane according to claim 1, wherein the curing agent is selected from a deoxime-type, deacetone-type, or deamidation-type curing agent. 3. The method for curing an organopolysiloxane according to claim 2, wherein the dealcoholated curing agent is an alkoxysilane having three or four alkoxy groups bonded to a silicon atom in one molecule. 4. The method for curing an organopolysiloxane according to claim 1, wherein the titanium chelate compound has β-diketones, β-ketoesters and / or oxycarboxylic acids as ligands at the titanium atom. 5. The method for curing an organopolysiloxane according to claim 1, wherein the divalent tin compound is a tin (II) carboxylate compound. 6. The mass ratio of the titanium chelate compound to the divalent tin compound is from 1:10 to 1: 0.01.
A method for curing the organopolysiloxane according to the above. 7. An organopolysiloxane curing catalyst comprising a titanium chelate compound and a divalent tin compound. 8. The mass ratio of the titanium chelate compound to the divalent tin compound is from 1:10 to 1: 0.01.
The catalyst for curing the organopolysiloxane according to the above.