JPH111618A - Production of room-temperature-curing organopolysiloxane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition excellent in stability of storage under sealed conditions by mixing, in a step 1, a diorganopolysiloxane with a crosslinking agent being a silane compound having an alkyl group and a hydrolyzable group and mixing, in a step 2, the obtained mixture with a crosslinking agent being a silane compound having a vinyl group and a hydrolyzable group. SOLUTION: The diorganopolysiloxane (A) has at least two hydroxyl groups in the molecule and is represented by formula I: HO(R<3> 2 Si0)n H (R<3> is a 1-10C monovalent hydrocarbon group; and n is an integer of 10 or greater). The first crosslinking agent (B) is a silane compound represented by formula II (R is a 1-8C unsubstmtuted or alkoxyl-substiuted alkyl; R<1> is a 1-8 C alkyl; and a is 2 or 3) or a partial hydrolyzate thereof. The second crosslinking agent (C) is a silane compound represented by formula III (the symbols are as defined in formula II) or a partial hydrolyzate thereof. The mixing ratio is such that 100 pts.wt. component A is mixed with 0.5-30 pts.wt. component B and 0.5-30 pts.wt. component C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a room temperature-curable organopolysiloxane composition containing an organopolysiloxane containing a hydroxy group, an alkylalkoxysilane and a vinylalkoxysilane.

[0002]

2. Description of the Related Art Conventionally, a room temperature-curable (RTV) organopolysiloxane composition is easy to handle and has excellent weather resistance and electrical properties. It is applied in various fields such as adhesives in electric and electronic fields. In particular, dealcohol-type RTV silicone rubber compositions that cure by releasing alcohol do not corrode metals, adhere well to various adherends, and do not have an unpleasant odor. It is useful for adhesives in the field of electric and electronic devices. Such a composition is disclosed in JP-B-39-27.
No. 643, Japanese Patent Publication No. 55-43119, and Japanese Patent Publication No. 7-39547.

[0003] Further, regarding the production method, a production method using a devolatilizer extruder (Japanese Patent Laid-Open No. 59-9616).
No. 3), a continuous production method (Japanese Patent Application Laid-Open No. 62-167324).
JP-A-5-131516, and a continuous manufacturing method using a screw extruder (JP-A-5-131516).

Also, Japanese Patent Application Laid-Open Nos. 2-215862 and 5-287207 propose a room temperature-curable organopolysiloxane composition having improved storage stability using a cross-linking agent having different reactivity in combination. However, the curing type is not the dealcoholization type (the crosslinking agent is different from the present invention), and there is no suggestion about the silane compound represented by the formula (2) of the present invention. The room-temperature-curable organopolysiloxane composition using alkoxysilane as a cross-linking agent has a problem that the reactivity of the organopolysiloxane silanol and the alkoxysilane is inferior to other cross-linking agents, so that it is difficult to cure over time. A solution to the point was desired.

[0005]

Means for Solving the Problems and Embodiments of the Invention In view of such a background, the present inventors have intensively studied the production method of the composition of the organopolysiloxane composition curable at room temperature, and as a result, the final Even if the composition is the same,
The present inventors have found that the storage stability is dramatically improved by limiting the type of the crosslinking agent and the method of addition, and the present invention has been accomplished.

That is, the present invention provides the following components (I) and (I)
In the method for producing a room-temperature-curable organopolysiloxane composition containing (I) and (III), the first step (I)
Mixing a diorganopolysiloxane represented by the formula (II) and a crosslinking agent represented by the formula (II), and then mixing the crosslinking agent represented by the formula (III) in the second step. A manufacturing method is provided. (I) 100 parts by weight of an organopolysiloxane having at least two hydroxy groups in one molecule (II) A silane compound having an alkyl group and a hydrolyzable group represented by the following general formula (1) Or a partial hydrolyzate thereof 0.5 to 30 parts by weight (III) a silane compound having a vinyl group and a hydrolyzable group represented by the following general formula (2) or a partial hydrolyzate thereof 0.5 ~ 30 parts by weight

[0007]

Embedded image (Wherein R may be the same or different, and has 1 to 1 carbon atoms)
8 unsubstituted or alkoxy-substituted alkyl groups, R ¹ is an unsubstituted or substituted alkyl group having 1 to 8 carbon atoms, and a is 2 or 3. )

[0008]

Embedded image (In the formula, R and a have the same meaning as described above.)

According to the present invention, the components (I) and (I)
In the method for producing a room-temperature-curable organopolysiloxane composition comprising I) and (III), in the first step (I)
Is mixed with the crosslinking agent represented by (II), the hydroxy group at the terminal of the organopolysiloxane polymer is blocked with the crosslinking agent represented by (II), and further, in the second step, the compound represented by (III) By mixing the indicated cross-linking agent, the difference in the structure of the cross-linking agent mixed with the polymer end group gives a significant difference in the reactivity with the water generated during storage from the filler etc. Is an improvement of That is, when an organopolysiloxane polymer participates in a reaction with moisture generated during storage from a filler or the like in a dealcohol-type composition, a cross-linking reaction between the polymers proceeds to increase the viscosity, gelation or curing. The reaction with the catalyst causes depolymerization of the siloxane, and the siloxane is not cured. Therefore, in the present production method, the crosslinking agent (crosslinking agent (A)) used in the first step and the crosslinking agent (crosslinking agent (B)) used in the second step are superior in reactivity to moisture, and the crosslinking agent (A ) <When the crosslinking agent (B) is provided and the hydrolyzable functional group of the crosslinking agent is under the same conditions, the substituent bonded to the silicon atom is an alkyl group, Since B) is a vinyl group, the crosslinking agent (B) having a vinyl group having a high electron-withdrawing property has a higher reactivity with moisture, and by mixing this in the second step, the water content during storage can be reduced. To improve the storage stability. In this case, the crosslinking agent (B) is added before the crosslinking agent (A),
Even if they are added simultaneously, the object of the present invention cannot be achieved, as is apparent from the results of the comparative examples described later.

Hereinafter, the present invention will be described in more detail. The organopolysiloxane composition curable at room temperature according to the present invention comprises (I) an organopolysiloxane containing a hydroxy group, (II) a crosslinking agent (A), (III) ) It contains a crosslinking agent (B).

Here, the organopolysiloxane (I)
Is an organopolysiloxane having at least two hydroxy groups in one molecule. The organopolysiloxane may be a branched be linear, but are preferably the following general formula _{^{(4) HO (R 3 2}} SiO) n H (4) ( wherein, R ³ is a substituted or having from 1 to 10 carbon atoms An unsubstituted monovalent hydrocarbon group, and n is an integer of 10 or more.)

R ^3, which is a substituent on the main chain of the organopolysiloxane polymer, is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms, such as a methyl group, an ethyl group and a propyl group. An alkyl group, a cycloalkyl group such as cyclohexyl group, an alkenyl group such as vinyl group or allyl group, an aryl group such as phenyl group or tolyl group, or a hydrogen atom of these groups partially substituted with a halogen atom or the like 3, And a group such as a 3,3-trifluoropropyl group. Among them, methyl group, phenyl group, 3,3
A 3-trifluoropropyl group is preferred, and a methyl group is particularly preferred. R ³ may be the same or different groups, and n in the formula represents a viscosity at 25 ° C. of the diorganopolysiloxane of 25 to 500,00.
It is an integer of 10 or more such that it is in the range of 0 cSt.
The preferred viscosity is 100 to 100,000 cSt.
It is. If it is less than 25 cSt, the cured rubber becomes brittle, and if it is more than 500,000 cSt, the viscosity of the composition becomes too high, which may cause a disadvantage in workability.

In the present invention, the component (I) can be used in combination with a non-hydrolysable, non-condensable silicone oil to impart elasticity and the like. This silicone oil is a dimethylpolysiloxane (2) whose both terminals are blocked with a trimethylsiloxy group.
The viscosity at 5 ° C. is preferably from 25 to 500,000 cSt), and the compounding amount is from 0 to 100 parts by weight of the component (I).
100 parts by weight are preferred.

The cross-linking agents (A) and (B) which are features of the present invention are as follows. The cross-linking agent (A) has an alkyl group represented by the following general formula (1) and is hydrolyzable. Or a partial hydrolyzate thereof.

[0015]

Embedded image

Here, R is an alkyl group such as a methyl group, an ethyl group or a propyl group, which may be the same or different, or a group in which a hydrogen atom bonded to these groups is substituted with an alkoxy group. Ethyl groups are preferred. a is 2 or 3, and preferably 3.

R ¹ is bonded to a carbon atom of an alkyl group having 1 to 8 carbon atoms such as a methyl group, an ethyl group or a propyl group, or a C1 to C8 alkyl group such as a 3,3,3-trifluoropropyl group. Is a group in which a part or all of the hydrogen atoms described above are substituted with a halogen atom or the like, and a methyl group and an ethyl group are particularly preferable.

Specific examples of the crosslinking agent (A) include the following compounds or partial hydrolysates thereof.

[0019]

Embedded image

The crosslinking agent (B) is a silane compound having a vinyl group and a hydrolyzable group represented by the following general formula (2) or a partial hydrolyzate thereof.

[0021]

Embedded image (In the formula, R and a have the same meaning as described above. Note that R may be the same or different.)

Specific examples of the crosslinking agent (B) include the following compounds or partial hydrolysates thereof.

[0023]

Embedded image

The above crosslinking agents (A) and (B) are used in amounts of 0.5 to 30 parts by weight with respect to 100 parts by weight of component (I). Sufficient cross-linking cannot be obtained, the composition does not have the desired rubber elasticity, and if it exceeds 30 parts by weight, the mechanical properties are inferior. Preferably it is in the range of 1 to 15 parts by weight.

The composition of the present invention may further contain a curing catalyst. As the curing catalyst, a conventionally used condensation catalyst or a mixture thereof may be used. Examples thereof include organic titanium compounds such as tetraisopropoxytitanium, tetrabutoxytitanium, and titanium bisacetylacetonate.

The above curing catalyst is used in an amount of 0.01 to 10 parts by weight, particularly 0.1 to 5 parts by weight, based on 100 parts by weight of the component (I). If the amount is less than 0.01 part by weight, the curability of the composition is reduced and the workability is remarkably reduced. If the amount is more than 10 parts by weight, the curing speed becomes too fast, and the mechanical properties of the composition after curing. May also decrease.

The composition of the present invention may optionally contain a fumed silica-based filler in order to improve the mechanical properties of the obtained silicone rubber elastic material. It is also optional to add inorganic fillers such as calcium carbonate, zinc carbonate, titanium dioxide, zinc oxide, diatomaceous earth and the like. Further, for the purpose of adjusting the physical properties, it is optional to add a thixotropy-imparting agent, a heat-resistance improving agent, a coloring agent, a fungicide, an adhesion-imparting agent, and the like.

Thus, in the production method of the present invention, as the first step, the organopolysiloxane (I) and the crosslinking agent (A) are mixed. In this case, if necessary, an inorganic filler, a catalyst, and other auxiliaries may be added. The mixing is preferably performed under reduced pressure, under substantially anhydrous conditions,
What is necessary is just to carry out by a normal method using a planetary mixer or a kneader.

Next, in the second step, the above-mentioned crosslinking agent (B) is added to and mixed with the mixture obtained in the first step. In this case, a filler, a catalyst, and other auxiliaries can be added in this step. The mixing in the second step can also be performed using a usual mixer, but it is preferable to perform the mixing under a substantially anhydrous reduced pressure.

The organopolysiloxane composition curable at room temperature obtained in this manner, even if it has the same composition as the composition described above, is sealed compared with a composition different from the method of blending the crosslinking agents (A) and (B). It has excellent storage stability even under conditions, and is suitably used as a sealant, coating agent, potting agent, adhesive or the like for electric / electronic use.

[0031]

EXAMPLES The present invention will be described below in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1] 60 parts by weight of polydimethylsiloxane having a viscosity of 5,000 cSt capped at both ends with hydroxy groups and calcium carbonate 4 treated with disproportionated rosin acid
After adding 0 parts by weight and mixing with a mixer, 3 parts by weight of methyltrimethoxysilane and 2.5 parts by weight of diisopropoxy-bis (acetylacetone) titanium are added and mixed under reduced pressure. Sample 3 was obtained by adding 3 parts by weight of silane and mixing under reduced pressure.

Example 2 35 parts by weight of polydimethylsiloxane having a viscosity of 50,000 cSt blocked at both ends with hydroxy groups, 25 parts by weight of polydimethylsiloxane having a viscosity of 50 cSt blocked at both ends with trimethylsiloxy groups, After adding 40 parts by weight of calcium carbonate treated with a soaking rosin acid and mixing with a mixer, 3 parts by weight of methyltrimethoxysilane and 2.5 parts by weight of diisopropoxy-bis (acetylacetone) titanium were added, and the mixture was added under reduced pressure. Mix,
Thereafter, 3 parts by weight of vinyltrimethoxysilane was added,
Mixing was performed under reduced pressure to obtain Sample 2.

Comparative Example 1 35 parts by weight of a polydimethylsiloxane having a viscosity of 50,000 cSt and having both ends capped with a hydroxy group, 25 parts by weight of a polydimethylsiloxane having a viscosity of 50 cSt and having both ends capped with a trimethylsiloxy group. After adding 40 parts by weight of calcium carbonate treated with a soaking rosin acid and mixing with a mixer, 3 parts by weight of vinyltrimethoxysilane and 2.5 parts by weight of diisopropoxy-bis (acetylacetone) titanium are added, and the mixture is added under reduced pressure. Mix,
Thereafter, 3 parts by weight of methyltrimethoxysilane was added,
The mixture was mixed under reduced pressure to obtain Sample 3.

Comparative Example 2 35 parts by weight of a polydimethylsiloxane having a viscosity of 50,000 cSt blocked at both ends with hydroxy groups, 25 parts by weight of a polydimethylsiloxane having a viscosity of 50 cSt blocked at both ends with a trimethylsiloxy group, After adding 40 parts by weight of calcium carbonate treated with a leveled rosin acid and mixing with a mixer, 3 parts by weight of vinyltrimethoxysilane, 3 parts by weight of methyltrimethoxysilane and titanium diisopropoxy-bis (acetylacetone) 2.
5 parts by weight were added and mixed under reduced pressure to obtain Sample 4.

[Comparative Example 3] 60 parts by weight of a polydimethylsiloxane having a viscosity of 5,000 cSt capped at both ends with a hydroxy group, 25 parts by weight of a polydimethylsiloxane having a viscosity of 50 cSt capped at both ends with a trimethylsiloxy group, and After adding 40 parts by weight of calcium carbonate treated with a soaking rosin acid and mixing with a mixer, 3 parts by weight of methyltrimethoxysilane and 2.5 parts by weight of diisopropoxy-bis (acetylacetone) titanium were added, and the mixture was added under reduced pressure. After mixing, Sample 5 was obtained.

Next, using the above samples 1 to 5, 2 mm
A thick sheet was molded, cured at 20 ° C. and 55% RH for 7 days, and evaluated for physical properties in the following manner. Table 1 shows the results. Drying time to the touch: Measured according to the method specified in JIS A 5758. Hardness: Measured according to the method specified in JIS C 2123. Elongation: Measured according to the method specified in JIS K6301. Tensile strength: Measured according to the method specified in JIS K6301. Discharge amount: The moisture-proof film of the cartridge filled with the sample was removed, a nozzle cut to 5 mmφ was attached, the sample was set in an air gun, and the weight extruded at a pressure of 2 kgf / cm ² for 5 seconds was measured.

After storage, after curing under the following storage conditions,
The measurement was performed in the same manner as in the initial stage. Storage conditions: The sample was put in a tube, and allowed to stand in a drier at 70 ° C. for 5 days in a sealed state.

[0039]

[Table 1]

From the results shown in Table 1, it can be seen that according to the present invention, a room temperature-curable organopolysiloxane composition having excellent storage stability can be obtained.

[0041]

According to the present invention, a room temperature-curable organopolysiloxane composition having excellent storage stability under sealing can be produced.

Claims (1)

[Claims] 1. The following components (I), (II) and (III)
In the method for producing a room-temperature-curable organopolysiloxane composition containing (I), the diorganopolysiloxane represented by (I) and the crosslinking agent represented by (II) are mixed in the first step, and then (III) in the second step. A method for producing a room-temperature-curable organopolysiloxane composition, which comprises mixing a crosslinking agent represented by the formula (1). (I) 100 parts by weight of an organopolysiloxane having at least two hydroxy groups in one molecule (II) A silane compound having an alkyl group and a hydrolyzable group represented by the following general formula (1) Or its partial hydrolyzate 0.5 to 30 parts by weight (Wherein R may be the same or different, and is an unsubstituted or alkoxy-substituted alkyl group having 1 to 8 carbon atoms, R ¹ is an unsubstituted or substituted alkyl group having 1 to 8 carbon atoms, a is 2 or (III) (III) A silane compound having a vinyl group and having a hydrolyzable group represented by the following general formula (2) or a partial hydrolyzate thereof 0.5 to 30 parts by weight (In the formula, R and a have the same meaning as described above.)