JPH086040B2 - Organopolysiloxane composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Use) The present invention relates to an addition-curable organopolysiloxane composition excellent in storage stability at room temperature and a cured product thereof.

(Prior Art) In general, an addition-curable organopolysiloxane composition is mainly composed of an alkenyl group-containing organopolysiloxane, an organohydrogenpolysiloxane, and a platinum catalyst. This composition is required to be able to be stably stored at room temperature for a long time in a mixed form of all the components, and to be cured only when heated. For this reason, the composition is usually blended with a storage stabilizer for improving storage stability at room temperature.

(Problems to be Solved by the Invention) Examples of the storage stabilizer include benzotriazole (Japanese Patent Publication No. 40-25069), acetylene group-containing alcohol (Japanese Patent Publication No. 44-31476), and acrylonitrile (Japanese Patent Publication No. 45-2).
2018 publication) etc. are known. However, these storage stabilizers are insufficient in the intended stabilizing effect,
If the composition is stored at room temperature for a long time, problems such as thickening and gelation occur. Further, if a large amount of the above-mentioned storage stabilizer is blended in order to sufficiently suppress the increase in viscosity and the like, there arises a disadvantage that more heating or more time than necessary is required for heat curing. Further, since these storage stabilizers lack compatibility with polysiloxane, there is a problem that when they are mixed in a large amount, phase separation occurs during storage at room temperature. In particular, when a large amount of acetylene group-containing alcohol or acrylonitrile is added, if hot air curing is performed in a high temperature atmosphere of about 150 ° C, curing will occur only from the surface, so the surface of the cured product will have fine wrinkles or irregularities. However, there is a problem that the commercial value of the cured product is significantly impaired.

Further, it has been proposed to use an organopolysiloxane containing an alkenyloxy group as a storage stabilizer (Japanese Utility Model Publication No. 54-3774). In this case, the problem of phase separation and the problem of wrinkles or unevenness on the surface during hot air curing in a high temperature atmosphere are solved,
Under mild heating conditions of about 0 ° C., there are problems that it takes a long time to cure and the effect of suppressing thickening at room temperature is poor.

Furthermore, the following formula, A silane compound represented by the following formula has been proposed as a storage stabilizer (JP-B-53-35983 and JP-A-59-133252). With these storage stabilizers, the problems of thickening and phase separation at room temperature can be avoided. However, since these silane compounds have a relatively high vapor pressure, most of them volatilize during the vacuum degassing operation performed after kneading with other components, and the curability is constant. Further, when hot air curing is performed in a high temperature atmosphere, the inconvenience of wrinkling and unevenness on the surface of the cured product cannot be avoided.

Therefore, the object of the present invention is to improve the above-mentioned drawbacks of the prior art, to have excellent long-term storage stability at room temperature, and to uniformly and rapidly cure by heating under relatively mild conditions. An addition-curing organopolysiloxane composition and a cured product thereof that can be uniformly cured without generating wrinkles or irregularities on the surface even when hot-air curing is performed at a high temperature for shortening the time. Is to provide.

(Means for Solving the Problems) The present invention has succeeded in achieving the above objects by using an organosilicon compound having a specific structure having a SiCH _{2 n} Si bond in one molecule as a storage stabilizer. It is a thing.

That is, according to the present invention, (A) the following general formula [I], In the formula, R ¹ is an alkenyl group, R ² is a monovalent unsubstituted or substituted hydrocarbon group containing no aliphatic unsaturated group, a is an integer of 1 to 3, and b is , And an integer of 0 to 2 (where a + b is 1 to 3).
An alkenyl group-containing organopolysiloxane having a structural unit represented by: (B) the following general formula [II], In the formula, R ³ is a substituted or unsubstituted monovalent hydrocarbon group, c is an integer of 0 to 2, d is an integer of 1 to 3, (wherein c + d is 1 to 3). An organohydrogenpolysiloxane having a structural unit represented by: (C) a platinum group metal-based catalyst, (D) the following general formula [III], In the formula, R ⁴ and R ⁵ are each a substituted or unsubstituted monovalent hydrocarbon group, R ⁶ is a substituted or unsubstituted monovalent hydrocarbon group having a —C≡C- bond, and p is Is a number of 2 or 3, q is an integer of 0 to 3, and n is an integer of 2 to 10, a silane compound represented by: and an organopolysiloxane composition containing: The cured product is provided.

(A) Organopolysiloxane Used as a base polymer in the present invention (A)
The component alkenyl group-containing organopolysiloxane is represented by the above general formula [I], that is, (Wherein R ¹ , R ² , a, and b are as described above) as a constituent unit, and is composed of the constituent unit and another siloxane unit.

In this general formula [I], examples of the alkenyl group R ¹ include a vinyl group, an allyl group, a 1-butenyl group, a 1-hexenyl group and the like, and a vinyl group is most advantageous from the viewpoint of easy synthesis. . The monovalent hydrocarbon group R ² having no aliphatic unsaturated group has, for example, 1 to 1 carbon atoms.
Examples thereof include 12 groups, preferably groups having 1 to 10 carbon atoms, such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, pentyl group, hexyl group, octyl group, decyl group and dodecyl group. Alkyl group; cycloalkyl group such as cyclopentyl group, cyclohexyl group, cyclobutyl group; aryl group such as phenyl group, tolyl group, xylyl group, naphthyl group; aralkyl group such as benzyl group, phenylethyl group, phenylpropyl group; Groups in which some or all of the hydrogen atoms of these hydrocarbon groups are substituted with halogen atoms such as chlorine, fluorine, bromine, etc., cyano groups, etc., such as chloromethyl group, trifluoropropyl group,
Halogenated hydrocarbon groups such as chlorophenyl group, dibromophenyl group, tetrachlorophenyl group, difluorophenyl group, β-cyanoethyl group, γ-cyanopropyl group,
Examples thereof include cyanoalkyl groups such as β-cyanopropyl group. In the present invention, the group R ² is most preferably a methyl group because it is easy to synthesize and the resulting cured product has good heat resistance and physical properties.

In the present invention, it is preferable that the constitutional unit represented by the general formula [I] described above is contained in a ratio such that the number of alkenyl groups in the molecule is two or more. Further, the constituent unit may be present at either the molecular end or the molecular chain of the organopolysiloxane, or both, but in order to impart excellent mechanical strength to the composition after curing, at least the molecular end may be present. Is preferably present in.

Examples of the structural unit other than the above structural unit include a siloxane unit represented by the following formula in which the same hydrocarbon group as R ² is bonded to a silicon atom.

R ² ₃ SiO _1/2 , R ² ₂ SiO _2/2 , R ² SiO _{3/2 The} above-mentioned organopolysiloxane may be linear, branched or cyclic, or may be a mixture thereof. . The viscosity of this organopolysiloxane at 25 ° C is preferably in the range of 25 to 500,000 cSt.

Specific examples of the organopolysiloxane preferably used in the present invention are as follows, although not limited thereto.

(However, in the above formula, i is 1, 2 or 3, e, g, j and l are positive integers, and f, h, k and m are 0 or positive integers.) (B) Organohydrogen Polysiloxane The organohydrogenpolysiloxane of the component (B) used in the present invention has the general formula [II]: (In the formula, R ³ , c and d are as described above) and have a structural unit represented by the formula, and act as a crosslinking agent. That is, included in the above structural unit
The cured product is formed by the addition reaction of the SiH group with the alkenyl group in the organopolysiloxane (A).

In the above general formula [II], the substituted or unsubstituted monovalent hydrocarbon group R ³ is the group R ² in the above general formula [I].
Examples thereof include the same as, but a methyl group is most preferable from the viewpoint of ease of synthesis. Further, the constituent unit may be present either at the molecular end or in the middle of the molecular chain.

Further, as a structural unit other than the above structural unit, (A)
Structural units similar to the structural unit other than the general formula [I] in the component can be exemplified by the structural units represented by the following formulas.

R ² ₃ SiO _1/2 , R ² ₂ SiO _2/2 , R ² SiO _3/2 , SiO _{2 The} organohydrogenpolysiloxane having such a structural unit may be linear, branched or cyclic,
It may be a mixture thereof, and its viscosity at 25 ° C is preferably in the range of 0.5 to 10,000 cSt.

Specific examples of such an organohydrogenpolysiloxane include, but are not limited to, the following.

(A) A branched organohydrogenpolysiloxane composed of (CH ₃ ) ₂ HSiO _1/2 units and SiO ₂ units.

(B) The following formula, (In the formula, p is 3 to 300 and q is an integer of 0 to 100) A straight chain organohydrogenpolysiloxane represented by the formula:

(C) The following formula, (In the formula, p is an integer of 1 to 100 and q is an integer of 0 to 100) A linear organohydrogenpolysiloxane represented by the following formula.

The above-mentioned organohydrogenpolysiloxane is
Depending on the type of organopolysiloxane of component (A),
It is desirable to use one having a good compatibility with the organopolysiloxane.

In such an organohydrogenpolysiloxane, the SiH group has a SiH group content of 0.25 to 4.0 mol, particularly 0.3 to 1 mol, per mol of the alkenyl group of the organopolysiloxane of component (A).
It is preferably used in an amount such that it is 3.0 mol. By using such an amount of the organohydrogenpolysiloxane, curing of the composition is sufficiently advanced, and a cured product having preferable properties such as hardness and strength can be obtained.

(C) Platinum Group Metal Catalyst The component (C) platinum group metal catalyst used in the present invention is an addition between an alkenyl group of the component (A) and a hydrosilyl group (SiH group) of the component (B). It promotes the reaction, for example, simple substance of platinum (platinum black), chloroplatinic acid,
Platinum-olefin complex, platinum-alcohol complex, platinum coordination compound, or a carrier of platinum, such as alumina or silica, which holds a simple substance of platinum, and other palladium-based and rhodium-based ones are preferable, but platinum-based ones are preferable. Is. In particular, chloroplatinic acid or a platinum-olefin complex is preferably used after being dissolved in an alcohol solvent, a ketone solvent, an ether solvent, a hydrocarbon solvent, or the like. In addition, a solid substance needs to be finely pulverized to improve dispersibility, and a carrier to be used is preferably one having a small powder diameter and a large specific surface area.

Such a catalyst is usually used in terms of platinum with respect to the component (A).
It is blended at a ratio of 0.1 to 500 ppm. If the amount is less than this range, the desired addition reaction accelerating effect cannot be obtained, and even if it is used in a large amount, the curing rate cannot be improved beyond a certain level, which is only economically disadvantageous.

(D) Silane compound In the present invention, the silane compound used as the component (D) is represented by the general formula [III], that is, (In the formula, R ^{4 to} R ⁶ , p, q, n are as described above). As is clear from this general formula [III], this silane compound has a molecular structure in which a hydrocarbon group having a SiCH _{2 n} Si bond and a -C≡C- bond is bonded to a silicon atom through an oxygen atom. have. With respect to such a molecular structure, the silane compound acts as a storage stabilizer, imparts long-term storage stability at room temperature to the composition, and at the same time, makes the temperature dependence during heat curing extremely large. In addition, it provides uniform curability even in hot air curing at high temperatures. In particular, the SiCH _{2 n} Si bond contained in the molecule gives the composition a remarkable temperature dependence upon heat curing.

In the above general formula [III], p is a number of 2 or 3, and q is an integer of 0 to 3, but from the viewpoint of storage stability of the composition at room temperature, p = q = 3. Is preferred.

Further, n is an integer of 2 to 10, but it is most preferable that n = 2 from the viewpoint of easiness of synthesis of the siloxane compound and availability of raw materials for synthesis.

R ⁴ and R ⁵ are each a substituted or unsubstituted monovalent hydrocarbon group, particularly preferably those having 1 to 10 carbon atoms, for example, an alkyl group such as a methyl group, an ethyl group and a propyl group, a phenyl group. A group, an aryl group such as a tolyl group, an aralkyl group such as a 2-phenylethyl group, a 2-phenylpropyl group, and a part or all of the hydrogen atoms of these groups are substituted with a halogen atom such as a chlorine atom or a fluorine atom. The groups described above can be exemplified.

R ⁶ is a substituted or unsubstituted monovalent hydrocarbon group having a —C≡C— bond, for example, the following general formula In the formula, R ⁷ and R ⁸ each represent a lower alkyl group having 6 or less carbon atoms such as a methyl group or an ethyl group, or a phenyl group, which may be bonded to each other to form a ring. Examples of the group are as follows. Particularly preferred group
R ⁶ is as follows.

Specific examples of the silane compound used as the component (D) in the present invention are as follows, although not limited thereto.

These silane compounds are generally used in an amount of 2 to 1 with respect to 1 gram equivalent of the platinum group metal of the platinum group metal catalyst of component (C).
It is preferred to use an amount sufficient to give 0,000 gram equivalents of -C = C-bonds.

Other compounding agents In addition to the above components, various known compounding agents can be added to the composition of the present invention.

For example, by adding an inorganic filler as required, flowability, hardness after curing, tensile strength, elongation, modulus and the like suitable for the application can be provided. Examples of such an inorganic filler include fumed silica, silica airgel, precipitated silica, crushed silica, diatomaceous earth, iron oxide, zinc oxide, titanium oxide, calcium carbonate, magnesium carbonate, zinc carbonate, carbon black, and the like. It The blending amount of these inorganic fillers is arbitrary as long as the object of the present invention is not impaired.

If necessary, it is possible to add an appropriate pigment, dye or antioxidant.

Organopolysiloxane composition The organopolysiloxane composition of the present invention is easily prepared by uniformly mixing the above components, can be stably stored at room temperature for a long period of time, and at the time of heat curing,
Since the temperature dependence of curing is significantly higher than that of conventional compositions, it cures quickly by gentle heating, and even when hot air curing is performed at high temperature, the surface does not wrinkle or roughen It has the property that it can be cured uniformly from the inside to the inside.

This composition is useful as a so-called one-liquid type, but can also be used as a so-called multiple-liquid type in which each component is divided into a plurality of two or more liquids and mixed at the time of use.

The composition of the present invention is a potting material in the electric / electronic industry, a coating material, and a silicone rubber such as a dipping material in the general industry, a rubber material for a molding die, a molding material, a coating material for release paper, and a dental impression material. , Silicone gel, silicone resin, etc.

(Examples) In the following examples, all "parts" mean "parts by weight", and preparation of a mixture, defoaming operation and measurement of viscosity are 25
Performed at ° C.

Example 1 100 parts of dimethylpolysiloxane having a molecular end blocked with a vinyldimethylsilyl group (viscosity 1,000 cP) 100 parts Was mixed with 8 parts of methylhydrodiene siloxane, and 0.01 part of any one of the following silane compounds (a) to (d) was mixed to prepare four kinds of mixtures.

Then, a 2-ethylhexyl alcohol solution of chloroplatinic acid was added to each mixture so that the amount of platinum was 5 ppm with respect to the total amount, and the components were uniformly mixed to prepare compositions (a) to (d).

Further, the above compositions (a) to (d) were degassed by leaving them under a constant degree of reduced pressure for a certain period of time. After defoaming, 25 ℃
Table 1 shows the viscosities of the respective compositions after 30 minutes and 6 hours have passed since the respective compositions were allowed to stand in a thermostatic chamber. Table 2 shows the time required for curing when the above composition was heated to 150 ° C and the appearance after curing.

Comparative Example 1 In the same manner as in Example 1, except that the following silane compounds (e) to (g) were used in place of the silane compounds (a) to (d), the composition (e) to (G) was prepared.

For these compositions (e) to (g), the viscosity after defoaming under reduced pressure, the time required for heat curing and the appearance after curing were measured in the same manner as in Example 1, and the results are shown in Table 1 and Table 1. The results are shown in Table 2.

Comparative Example 2 In Example 1, a composition (h) was prepared without incorporating any of the silane compounds (a) to (d). This composition was cured at 25 ° C. 5 minutes after mixing the respective components and became a rubber.

(Effect of the Invention) According to the present invention, the storage stability of the addition-curable organopolysiloxane composition at room temperature is significantly improved,
In addition, even if curing is performed in a short period of time by heating under relatively mild conditions, and even if curing is performed with hot hot air to shorten the curing time, wrinkles and irregularities may occur on the surface. Therefore, it became possible to carry out uniform curing.

By using the organopolysiloxane composition of the present invention having the above characteristics, it is possible to shorten various manufacturing steps, extend the working time of the composition, and save energy by curing at low temperature.

Claims (2)

[Claims] 1. (A) The following general formula [I], In the formula, R ¹ is an alkenyl group, R ² is a monovalent unsubstituted or substituted hydrocarbon group containing no aliphatic unsaturated group, a is an integer of 1 to 3, and b is , An integer of 0 to 2 (where a + b is an integer of 1 to 3), an alkenyl group-containing organopolysiloxane having a structural unit represented by: (B) the following general formula [II], In the formula, R ³ is a substituted or unsubstituted monovalent hydrocarbon group, c is an integer of 0 to 2, d is an integer of 1 to 3, (wherein c + d is 1 to 3). An organohydrogenpolysiloxane having a structural unit represented by: (C) a platinum group metal-based catalyst, (D) the following general formula [III], In the formula, R ⁴ and R ⁵ are each a substituted or unsubstituted monovalent hydrocarbon group, R ⁶ is a substituted or unsubstituted monovalent hydrocarbon group having a —C≡C- bond, and p is Is a number of 2 or 3, q is an integer of 0 to 3, and n is an integer of 2 to 10. A silane compound represented by: 2. A cured product obtained by curing the composition according to claim 1.