JP3531426B2 - Method for producing room temperature curable organopolysiloxane composition - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, room temperature curable (RTV) organopolysiloxane compositions are easy to handle and have excellent weather resistance and electrical characteristics. It has been applied in various fields such as adhesives in electric and electronic fields. In particular, a dealcohol type RTV silicone rubber composition that releases alcohol and cures is not corrosive to metals, adheres well to various adherends, and does not have an unpleasant odor. It is said to be useful as an adhesive in the electric and electronic fields. Examples of such a composition include Japanese Patent Publication No. 39-27.
It is disclosed in Japanese Patent Publication No. 643, Japanese Patent Publication No. 55-43119, Japanese Patent Publication No. 7-39547 and the like.

Regarding the manufacturing method thereof, a manufacturing method using a devolatilizer extruder (Japanese Patent Laid-Open No. 59-9616).
No. 3), continuous manufacturing method (JP-A-62-167324).
Japanese Patent Laid-Open Publication No. 5-1315), a continuous manufacturing method using a screw extruder (Japanese Patent Laid-Open No. 5-131516), and the like, both of which are characterized by the apparatus.

Further, JP-A-2-215862 and JP-A-5-287207 propose room-temperature-curable organopolysiloxane compositions having improved storage stability in which different reactive crosslinking agents are used in combination. However, these are not a dealcohol type in the curing 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. In the room-temperature-curable organopolysiloxane composition using an alkoxysilane as a crosslinking agent, the reactivity of silanol and alkoxysilane of the organopolysiloxane is inferior to that of other crosslinking agents, and thus there is a problem that it tends to be difficult to cure over time. The solution of the point was desired.

[0005]

Means for Solving the Problems and Modes for Carrying Out the Invention Based on such a background, the inventors of the present invention have made earnest studies on a method for producing a room temperature-curable organopolysiloxane composition, Even if it has the same composition as
The present invention has been completed by finding that storage stability is dramatically improved by limiting the type of crosslinking agent and the method of addition.

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), in the first step, (I)
A diorganopolysiloxane represented by the formula (1) and a crosslinking agent represented by the formula (II) are mixed, and then in the second stage, the first step
There is provided a method for producing a room temperature curable organopolysiloxane composition, which comprises mixing the crosslinking agent represented by (III) with the mixture obtained in (3). (I) 100 parts by weight of 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 Partial hydrolyzate 0.5 to 30 parts by weight (III) Silane compound represented by the following general formula (2) and having a vinyl group and a hydrolyzable group or a partial hydrolyzate thereof 0.5 to 30 parts by weight

[0007]

[Chemical 3] (In the formula, R may be the same or different, and the number of carbon atoms is 1 to 1.
8 is an unsubstituted or alkoxy-substituted alkyl group, R ¹ is a C 1-8 unsubstituted or substituted alkyl group, and a is 2 or 3. )

[0008]

[Chemical 4] (In the formula, R and a have the same meanings as described above.)

According to the present invention, the above-mentioned components (I) and (I
I), (Oite to a method for producing a room temperature vulcanizable organopolysiloxane composition comprising III), organopolysiloxanes represented by a first step (I) (II)
By mixing the cross-linking agent represented by (1), blocking the hydroxy group at the end of the organopolysiloxane polymer with the cross-linking agent represented by (II), and further mixing the cross-linking agent represented by (III) in the second step, Due to the difference in the structure of the cross-linking agent mixed with the polymer end group, the reactivity with moisture generated from the filler during storage is significantly different, and the storage stability is improved. That is, in the dealcohol-type composition, when the organopolysiloxane polymer participates in the reaction with the water generated from the filler during storage, the crosslinking reaction between the polymers proceeds, resulting in thickening, gelation or curing. Depolymerization of siloxane occurs due to reaction with the catalyst, resulting in uncured. Therefore, in the present production method, the cross-linking agent (cross-linking agent (A)) used in the first step and the cross-linking agent (cross-linking agent (B)) used in the second step are superior in reactivity to moisture, and the cross-linking agent (A ) <Crosslinking agent (B) is added, and when the hydrolyzable functional groups of the crosslinking agent are under the same conditions, the substituent bonded to the silicon atom is a crosslinking agent (A) is an alkyl group, a crosslinking agent ( Since B) is a vinyl group, the cross-linking agent (B) having a vinyl group having a high electron-withdrawing property has higher reactivity with water, and by mixing this in the second step, the water content during storage can be increased. To improve the storage stability. In this case, the cross-linking agent (B) is added before the cross-linking agent (A),
Even if added at the same time, the object of the present invention cannot be achieved, as is apparent from the results of Comparative Examples described later.

The present invention will be described in more detail below. The room temperature-curable organopolysiloxane composition according to the present invention comprises (I) a hydroxy group-containing organopolysiloxane, (II) a cross-linking agent (A), and (III). ) Contains a crosslinking agent (B).

Here, the organopolysiloxane (I)
Is an organopolysiloxane having at least two or more hydroxy groups in one molecule. This organopolysiloxane may be linear or branched, but is preferably of the following general formula (4) HO (R ³ ₂ SiO) _n H (4) (wherein R ³ is a C 1-10 substituted or It is an unsubstituted monovalent hydrocarbon group, and n is an integer of 10 or more.).

[0012] R ³ is a substituent in the main chain of the organopolysiloxane polymer is a hydrocarbon group of a substituted or unsubstituted monovalent 1-10 carbon atoms, such as methyl group, ethyl group, such as propyl An alkyl group, a cycloalkyl group such as a cyclohexyl group, an alkenyl group such as a vinyl group or an allyl group, an aryl group such as a phenyl group or a tolyl group, or a hydrogen atom of these groups partially substituted with a halogen atom or the like 3, A group such as a 3,3-trifluoropropyl group. Among these, methyl group, phenyl group, 3,3
A 3-trifluoropropyl group is preferable, and a methyl group is particularly preferable. R ³ may be the same group or different groups, and n in the formula is such that the viscosity of the diorganopolysiloxane at 25 ° C. is 25 to 500,000.
It is an integer of 10 or more that is in the range of 0 cSt.
The preferable viscosity is 100 to 100,000 cSt.
Is. If it is less than 25 cSt, the rubber after curing will become brittle, and if it is more than 500,000 cSt, the viscosity of the composition will be too high, which may be disadvantageous in workability.

In the present invention, the component (I) can be used in combination with a non-hydrolyzable or non-condensable silicone oil to impart elasticity. This silicone oil contains dimethylpolysiloxane (2
The viscosity at 5 ° C is preferably 25 to 500,000 cSt), and the compounding amount is 0 to 100 parts by weight of the component (I).
100 parts by weight is preferred.

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

[0015]

[Chemical 5]

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

R ¹ is bonded to a carbon atom of an alkyl group having 1 to 8 carbon atoms such as methyl group, ethyl group and propyl group, and an alkyl group having 1 to 8 carbon atoms such as 3,3,3-trifluoropropyl group. The hydrogen atom is a group in which a part or all of the hydrogen atoms 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 and partial hydrolysates thereof.

[0019]

[Chemical 6]

The cross-linking 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]

[Chemical 7] (In the formula, R and a have the same meanings as described above. Note that R may be the same or different.)

Specific examples of the cross-linking agent (B) include the following compounds and partial hydrolysates thereof.

[0023]

[Chemical 8]

The cross-linking agents (A) and (B) are used in an amount of 0.5 to 30 parts by weight per 100 parts by weight of the 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 become poor. It is preferably in the range of 1 to 15 parts by weight.

A curing catalyst can be further added to the composition of the present invention. The curing catalyst may be a conventionally used condensation catalyst or a mixture thereof, for example, dimethyldimethoxytin, dibutyltin diacetate, dibutyltin dioctoate, dibutyltin dibenzylmalate, an organic tin compound such as dioctyltin diacetate, Examples include organic titanium compounds such as tetraisopropoxy titanium, tetrabutoxy titanium, 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 parts by weight, the curability of the composition is lowered and the workability is remarkably lowered. If the amount is used in excess of 10 parts by weight, the curing speed becomes too fast, and the mechanical properties of the composition after curing are increased. May also decrease.

A fumed silica-based filler may be added to the composition of the present invention, if necessary, in order to improve the mechanical properties of the resulting silicone rubber elastic body. 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 thereof, it is optional to add a thixotropy imparting agent, a heat resistance improver, a coloring agent, a fungicide, an adhesiveness imparting agent and the like.

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

Next, in the second step, the above crosslinking agent (B) is added and mixed to the mixture obtained in the first step. In this case, fillers, catalysts and other auxiliaries can also be added in this step. The mixing in the second step can also be carried out using an ordinary mixer, but it is preferably carried out under a substantially anhydrous reduced pressure.

The room-temperature-curable organopolysiloxane composition thus obtained has the same composition as that of a composition different from that of the above-mentioned cross-linking agents (A) and (B), but is hermetically sealed. It has excellent storage stability even under conditions, and is suitably used as a sealant, coating agent, potting agent, adhesive, etc. for electric and electronic applications.

[0031]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Example 1 60 parts by weight of polydimethylsiloxane having both ends blocked with hydroxy groups and a viscosity of 5,000 cSt, and calcium carbonate treated with disproportionated rosin acid 4
After adding 0 part by weight 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 mixed under reduced pressure, and then vinyltrimethoxy. 3 parts by weight of silane was added and mixed under reduced pressure to obtain sample 1.

Example 2 35 parts by weight of polydimethylsiloxane having both ends blocked with hydroxy groups and a viscosity of 50,000 cSt, 25 parts by weight of polydimethylsiloxane having both ends blocked with trimethylsiloxy groups and having a viscosity of 50 cSt, and After adding 40 parts by weight of calcium carbonate treated with homogenized 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 and
Then add 3 parts by weight of vinyltrimethoxysilane,
Mixing under reduced pressure gave sample 2.

Comparative Example 1 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, and After adding 40 parts by weight of homogenized rosin acid-treated calcium carbonate and mixing with a mixer, 3 parts by weight of vinyltrimethoxysilane and 2.5 parts by weight of diisopropoxy-bis (acetylacetone) titanium were added, and the mixture was added under reduced pressure. Mix and
Then add 3 parts by weight of methyltrimethoxysilane,
The mixture was mixed under reduced pressure to obtain Sample 3.

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

Comparative Example 3 60 parts by weight of polydimethylsiloxane having both ends blocked with hydroxy groups and a viscosity of 5,000 cSt, 25 parts by weight of polydimethylsiloxane having both ends blocked with trimethylsiloxy groups and having a viscosity of 50 cSt, and After adding 40 parts by weight of calcium carbonate treated with homogenized 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. Mixed to obtain sample 5.

Next, using the above samples 1 to 5, 2 mm
A thick sheet was molded and cured at 20 ° C. and 55% RH for 7 days, and the physical properties were evaluated in the following manner. The results are shown in Table 1. Touch-free time: 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 K 6301. Discharge amount: The moisture-proof film of the cartridge filled with the sample was removed, a nozzle cut to 5 mmφ was attached, the nozzle was set on an air gun, and the weight was extruded at a pressure of 2 kgf / cm ² for 5 seconds, and the weight was measured.

After storage, after curing under the following storage conditions,
It measured like the initial stage. Storage conditions: The sample was put in a tube, and left to stand in a dryer at 70 ° C for 5 days under a closed condition.

[0039]

[Table 1]

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

[0041]

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

Continuation of front page (56) Reference JP-A-1-306469 (JP, A) JP-A-61-247756 (JP, A) JP-A-9-118827 (JP, A) JP-A-5-287207 (JP , A) JP 8-143775 (JP, A) JP 8-269334 (JP, A) JP 62-43460 (JP, A) JP 4-366171 (JP, A) JP 64-14272 (JP, A) JP-A-10-316858 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08L 83/00-83/16 CA (STN) REGISTRY (STN )

Claims (4)

(57) [Claims] 1. The following components (I), (II) and (III)
In the method for producing a room temperature-curable organopolysiloxane composition containing, a diorganopolysiloxane represented by (I) and a crosslinking agent represented by (II) are mixed in the first step, and then the second step is performed . Mixture obtained in one step
A method for producing a room-temperature-curable organopolysiloxane composition, which comprises mixing the crosslinking agent represented by (III) with (I) 100 parts by weight of 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 Partial hydrolyzate 0.5-
30 parts by weight [Chemical formula 1] (In the formula, R may be the same or different, and the number of carbon atoms is 1 to 1.
8 is an unsubstituted or alkoxy-substituted alkyl group, R ¹ is a C 1-8 unsubstituted or substituted alkyl group, and a is 2 or 3. ) (III) Silane compound having a vinyl group and having a hydrolyzable group or a partial hydrolyzate thereof represented by the following general formula (2) 0.5 to
30 parts by weight [Chemical formula 2] (In the formula, R and a have the same meanings as described above.) 2. A non-hydrolyzable, non-condensable silicone oil, which is a diorganopolysiloxane represented by (I), has a dimethylpolysiloxane whose both ends are blocked with trimethylsiloxy groups (having a viscosity at 25 ° C. of 25). ~ 50
The method for producing a room temperature-curable organopolysiloxane composition according to claim 1, wherein the organopolysiloxane composition is used together. 3. The curing catalyst is mixed in the first step.
Alternatively, the method for producing a room temperature curable organopolysiloxane composition according to item 2. 4. The method for producing a room temperature curable organopolysiloxane composition according to claim 1, 2 or 3, wherein an inorganic filler is mixed in the first step.