JPH06107950A - Heat curable organopolysiloxane composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition being stable for a long period at ambient temperature and capable of rapidly and uniformly providing a cured product by including an organopolysiloxane and a specific hydrodiene polysiloxane-containing capsule and a platinum metal-based catalyst. CONSTITUTION:The objective composition contains (A) an organopolysiloxane having 2 alkenyl groups in one molecule, e.g. a compound of formula I or formula II [(s) is positive integer; (t) is >=0; (p) is 2 or 3; (u) is same as (s); (v) is same as (t)], (B) a hydrodienepolysiloxane-containing capsule consisting of (i) hydrodienepolysiloxane having >=2 hydrogen atoms bound to silicon in one molecule and (ii) a thermoplastic resin (preferably silicone resin) having 40-200 deg.C softening point or glass transition point and forming a mononucleus or a polynucleus in the component (i) and forming a wall material in the component (ii) and (C) a platinum metal based catalyst (preferably carrying a solid platinum on a support such as alumina).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat-curable organopolysiloxane composition which is cured by a hydrosilylation reaction. More particularly, it relates to a heat-curable organopolysiloxane composition having excellent storage stability near room temperature and rapidly curing at high temperatures.

[0002]

2. Description of the Related Art Addition type organopolysiloxane compositions using a hydrosilylation reaction have a feature that they are rapidly cured to a deep portion without a reaction by-product, so that they are used as adhesive sealing materials, potting materials and coatings for electric and electronic parts. It is used in a wide range of fields such as materials, seal adhesive gaskets used in factory construction, and release coating materials for paper and films. However, this type of organopolysiloxane composition has a very poor storage stability and cannot be stored by enclosing it in a single container, and therefore, it is usually necessary to separate the constituent components of the composition. There is a problem in that it must be stored separately in a container, and in use, a two-component or three-component composition must be weighed, mixed and degassed.

[0003]

In order to solve this problem, a method for controlling the catalytic activity of a hydrosilylation reaction catalyst, particularly a platinum-based catalyst, has been proposed. One of the methods is to use an additive having the function of controlling the catalytic activity of a platinum-based catalyst, such as an acetylene-based compound (US Pat.
No. 5,420) Organosiloxane containing CH ₂ ═CHRSiO unit (R is a monovalent hydrocarbon group not containing unsaturated aliphatic hydrocarbon) (see Japanese Patent Publication No. Sho 48-10947), ionic compound of heavy metal (US Pat. No. 3,532,649), benzotriazole compounds, hydroperoxide compounds and the like have been proposed. However, these methods have drawbacks such as a decrease in curing property and an increase in the time required for curing when an attempt is made to obtain long-term storage stability.

The second method is to isolate the hydrosilylation reaction catalyst from other reactive components in the composition until heat curing. That is, a method of encapsulating a hydrosilylation catalyst such as a 2-ethylhexanol solution of chloroplatinic acid or a platinum alkenyl siloxane catalyst in a mononuclear or polynuclear encapsulation with a thermoplastic resin having a softening point and separating it from other reactive components is proposed. (Japanese Patent Publication No. 53-41707, Japanese Patent Laid-Open No. 64-
47442, Japanese Patent Publication No. 4-46962).

However, even with such a method, if the capsule wall material is a resin that is poorly compatible with silicone, the peripheral portion of the catalyst capsule has good curability at the time of heating, but the curing is weak at a portion apart from it. A uniform cured product cannot be obtained. If the wall material is a silicone resin that has a softening point that makes it compatible with silicone when heated, it may gel around the catalyst capsule when stored at room temperature for a long time due to the sustained release characteristic of silicone. It often happened. In addition, the capsule of hydrosilylation reaction catalyst is difficult to uniformly disperse because the absolute amount relative to the composition is small, the crosslinking does not proceed uniformly even after heating, the hardness is low, the compression set of the molded product is large, etc. There were many inconveniences.

Therefore, an object of the present invention is to provide a heat-curable organopolysiloxane composition which is excellent in long-term storage stability at room temperature, has a rapid curing rate at high temperature, and can be uniformly crosslinked. To provide.

[0007]

According to the invention, (A) an organopolysiloxane having at least two alkenyl groups in the molecule (B) (B-1) at least two silicons in one molecule. Hydrogen polysiloxane having a hydrogen atom bonded to the atom and (B-2) a softening point or a thermoplastic resin having a glass transition point of 40 to 200 ° C. (B-1) is mononuclear or polynuclear. There is provided a heat-curable organopolysiloxane composition containing a hydrogen polysiloxane-containing capsule in which (B-2) is a wall material, and (C) a platinum group metal-based catalyst.

That is, the present invention uses the above-mentioned as a crosslinking agent component.
The use of the capsule containing the hydrogen polysiloxane of (B) is a remarkable feature, and by doing so, the above-mentioned object was successfully achieved. That is, in the composition of the present invention, by heating this, the wall material in the capsule of (B) is dissolved and the core hydrogen polysiloxane (B-1) which is a crosslinking agent is eluted, and this is )
And crosslinking proceeds by contact with the component (C).

(A) Alkenyl Group-Containing Organopolysiloxane In the composition of the present invention, the organopolysiloxane of component (A), which is the base component, has at least two alkenyl groups in one molecule. The alkenyl group is bonded to a silicon atom in the molecule, and examples thereof include a lower alkenyl group such as vinyl group, allyl group, methallyl group and hexenyl group. These alkenyl groups may be present at the ends of the molecular chain or may be present in the middle of the molecular chain.

Further, an organic group other than the alkenyl group is also bonded to the silicon atom, and the organic group has 1 to 1 carbon atoms.
Examples thereof include an unsubstituted or substituted monovalent hydrocarbon group having 10, preferably 1 to 8 carbon atoms. Specific examples of the hydrocarbon group include alkyl groups such as methyl group, ethyl group, propyl group and butyl group; cycloalkyl groups such as cyclohexyl group; aryl groups such as phenyl group and tolyl group; benzyl group, phenylethyl group Aralkyl groups such as;
And groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms, such as chloromethyl groups, 3,3,3
-A trifluoropropyl group etc. can be mentioned.

This organopolysiloxane has a temperature of 25 ° C.
It is preferable that the viscosity at 100 is in the range of 100 to 200,000 cSt, and the polymerization degree corresponding thereto is obtained. That is, if the viscosity is higher than the above range, the workability of the composition may be impaired, and if it is lower than the range, the properties of the cured product may be inconvenient.

In the present invention, the above-mentioned organopolysiloxane may be used alone or in combination of two or more kinds. The molecular structure is preferably linear, but may be partially branched.
Suitable examples of the organopolysiloxane of the component (A) are typically those represented by the following formulas (1) to (3).

[Chemical 1]

[Chemical 2]

[Chemical 3] In the above formula, p is 2 or 3, s, u and w are positive integers,
t, v and x represent 0 or a positive integer.

(B) Hydrogen-Polysiloxane-Containing Capsule In the present invention, the component (B) contains the hydrogen-polysiloxane (B-1) as a core and has a softening point or a glass transition point of 40 to 200 ° C. A capsule containing a plastic resin (B-2) as a wall material.

The hydrogen polysiloxane as the component (B-1) acts as a cross-linking agent for the alkenyl group-containing organopolysiloxane of the component (A).
Those having two or more hydrogen atoms bonded to silicon atoms in one molecule are used. That is, the adhesive cured product of the rubber elastic body is formed by the addition reaction of the alkenyl group in the component (A) and the SiH group in the component (B-1).

In this organohydrogenpolysiloxane, the hydrogen atom may be bonded to any silicon atom at the molecular end or in the middle of the molecular chain. Examples of the organic group bonded to the silicon atom include groups other than the alkenyl group exemplified in the organopolysiloxane of the component (A). The organohydrogenpolysiloxane may have a linear, branched or cyclic structure, or may be a mixture thereof. The degree of polymerization of these organohydrogenpolysiloxanes is preferably 300 or less. A suitable example is shown below.

[0016]

[Chemical 4] (In the above formula, b, c, d, e, f, g, i represent 0 or a positive integer, and h represents an integer of 2 or more.)

[Chemical 5] (In the above formula, R ¹ represents a hydrogen atom, a methyl group, a propyl group or a trimethylsiloxy group.)

This organohydrogenpolysiloxane is in an amount sufficient to supply 0.6 to 6.0 hydrogen atoms bonded to silicon atoms per one alkenyl group contained in the organopolysiloxane as the component (A). ,
Preferably, the molar ratio of SiH group to alkenyl group is 1.2 to 4.
It is used in such a ratio that it becomes 0.

The thermoplastic resin as the component (B-2) has a softening point or a glass transition point of 40 to 200 ° C., and the hydrogen polysiloxane (B-1) substantially permeates at least during storage. Any resin can be used as long as it is not dissolved and is not substantially dissolved in the organopolysiloxane of the component (A). This softening point is the temperature at which the resin begins to flow due to its own weight or its surface tension, and can be easily known by observing the crushed particles with a microscope while raising the temperature at a constant rate. The glass transition point is DSC (differential
You can find out by measuring with a scanning calorimeter). In the present invention, it can be used if either the softening point or the glass transition point is in the range of 40 to 200 ° C. When the softening point or the glass transition point is lower than 40 ° C, the storage stability of the composition is significantly lowered, and when it is higher than 200 ° C, a sufficient heat curing rate cannot be obtained.

In the present invention, preferred examples of the thermoplastic resin that can be used as the component (B-2) include silicone resin, polysilane resin, polystyrene resin, acrylic resin, methyl cellulose resin, etc. Considering the uniformity in the composition, the silicone resin is most suitable. The silicone resin is not particularly limited in its composition as long as the softening point or the glass transition point is within the above range, and any resin having a siloxane skeleton as a main component can be used, for example, (Me ₃ Si
Although it is possible to use a thermoplastic silicone composed of (O _1/2 ) unit and (SiO _4/2 ) unit, generally, a main component is a monophenylsiloxane unit (PhSiO _3/2 ),
Diphenylsiloxane unit (Ph ₂ SiO), dimethylsiloxane unit (Me ₂ SiO), methylsiloxane unit (MeSiO _3/2 )
, PhSi [theta] _3/2 from the relationship of preferably silicone resin, in particular the softening point comprising a methyl vinyl siloxane units (MeViSiO)
Units and MeSiO _3/2 units total 20-80 mol%, Ph ₂ SiO
A silicone resin having a total of 80 to 20 mol% of units, Me ₂ SiO units and MeViSiO units is preferable (in the above, Me represents a methyl group, Ph represents a phenyl group, and Vi represents a vinyl group).

Such a thermoplastic fine particle capsule containing an organohydrogenpolysiloxane can be prepared by the interfacial polymerization method or i
It can be manufactured by chemical methods such as n-situ polymerization method, physicochemical methods such as coacervation method and in-liquid drying method, and physical and mechanical methods such as spray drying method. The in-liquid drying method and the spray drying method are preferable because fine particles having a distribution can be obtained relatively easily.

The organohydrogenpolysiloxane-containing thermoplastic fine particle capsules obtained by these methods can be used as it is as the component (B), but this is washed with a suitable washing solvent to remove the organohydrogenpolysiloxane attached to the surface thereof. Removal of hydrogen polysiloxane is desirable to obtain a heat-curable organopolysiloxane composition having excellent storage stability. A suitable cleaning solvent does not dissolve the thermoplastic resin, but has a property of dissolving the organohydrogenpolysiloxane. Optimally, low molecular weight organopolysiloxanes such as hexamethyldisiloxane,

[Chemical 6] Is desirable. However, unlike the case of encapsulating a platinum-based catalyst, in the present invention, even if a small amount of organohydrogenpolysiloxane is attached due to insufficient cleaning, it is compatible with the alkenylpolysiloxane of the component (A). Since it is diffused into the composition to have a low concentration, it is possible to substantially suppress the formation of an elastomer due to the progress of crosslinking at room temperature, which is also an advantage of the present invention.

In the capsule of the component (B), the (B
The ratio of -1) is preferably 0.05% by weight or more, and particularly preferably 5 to 60% by weight. If it is less than 0.05% by weight, the proportion of the thermoplastic resin in the composition of the present invention becomes too high, and the physical properties after curing may be impaired.

In the present invention, the amount of the component (B) blended is such that the amount of the organohydrogenpolysiloxane of the component (B-1) bound to the silicon atom per alkenyl group of the component (A). It is determined to be an amount sufficient to supply 0.6 to 6.0 hydrogen atoms.

(C) Platinum Group Metal Catalyst The component (C), which is a platinum group metal catalyst, comprises the alkenyl group and Si
It is a catalyst for addition reaction with H groups and acts as a curing accelerator. Such catalysts include platinum-based, palladium-based, and rhodium-based catalysts, and any of these can be used. In the present invention, a platinum-based catalyst is particularly suitable, but is not limited to, for example, platinum black,
Solid platinum supported on a carrier such as alumina or silica, chloroplatinic acid, alcohol-modified chloroplatinic acid, and a complex of chloroplatinic acid and an olefin can be preferably used.

When using these catalysts, when they are solid catalysts, it is preferable that they are finely crushed to improve dispersibility, or that the carrier has a small particle size and a large specific surface area. Further, regarding the complex of chloroplatinic acid and olefin, it is desirable to use these after dissolving them in a solvent such as alcohol, ketone, ether or hydrocarbon type. The amount of these catalysts used is a so-called catalyst amount to obtain a desired curing rate, but from the economical viewpoint or in order to obtain a good cured product, it is preferable to use the following ratios. That is, for those that are compatible with the siloxane component, such as chloroplatinic acid,
0.1 to 100 ppm (platinum equivalent) based on the total amount of components (A) and (B), and 20 to 50 for solid catalysts such as platinum black.
It is recommended to set the range to 0 ppm (platinum equivalent).

Other Components The adhesive organopolysiloxane composition of the present invention can be obtained by uniformly mixing the predetermined amounts of the above-mentioned components (A) to (C), depending on the application. Fillers and other compounding agents may be added.

For example, as the filler, any of those usually used for addition type silicone rubber compositions can be used, and specifically, fumed silica, precipitable silica, hydrophobized silica, and dioxide. Titanium, ferric oxide, aluminum oxide, zinc oxide, quartz powder, diatomaceous earth, calcium silicate, talc, bentonite, asbestos, glass fiber, organic fiber and the like are used alone or in combination of two or more kinds. The amount of such a filler to be compounded is arbitrary as long as the object of the present invention is not impaired, but is generally 600 parts by weight or less per 100 parts by weight of the organopolysiloxane of component (A). Of these, fumed silica is preferably 25 parts by weight or less, and in the case of alumina or the like, the range of 300 to 500 parts by weight is preferable, and it is preferable depending on the oil absorption of the filler, surface area, and specific gravity. The addition amount is different.

In order to reinforce the strength of the cured product, S
Resin structure containing iO ₂ unit, Vi (R ') ₂ -SiO _0.5 unit and R' ₃ -SiO _0.5 unit (Vi is vinyl group, R'is monovalent hydrocarbon group not containing unsaturated aliphatic group) Organopolysiloxane (see JP-B-38-26771, JP-B-45-9476, etc.) can also be added. Further, for the purpose of controlling the curing rate of the composition, an organopolysiloxane having Vi (R ') SiO units (R' is the same as above) (see Japanese Patent Publication No. 48-10947, etc.), U.S. Pat. No. 3,445,420 The acetylene compounds disclosed in US Pat. No. 3,532,649 and the heavy metal ionic compounds disclosed in U.S. Pat. Functional organopolysiloxanes may also be included.

Further, heat resistance improvers such as cerium oxide, flame retardants such as titanium oxide, benzotriazole, zinc carbonate and manganese carbonate, addition reaction control agents such as vinyl group-containing siloxanes and acetylenic compounds, foaming agents, etc. It can be blended appropriately.

Since the composition of the present invention is excellent in storage stability near room temperature, it can be stored for a long period of time as a one-component organopolysiloxane composition, and it is a thermoplastic resin which is a wall material of the capsule. When heated in accordance with the softening point or glass transition point of the resin, it rapidly cures to form a cured product and therefore has excellent heat-curing properties. Therefore, silicone for pressure molding such as press molding, transfer molding, injection molding, etc. Useful as an elastomer composition,
It is also useful as a liquid potting, a silicone elastomer as a sealing material, and a silicone gel, and is expected to be widely used in the field of construction materials including electric and electronic.

[0031]

[Examples] Examples and comparative examples of the present invention will now be described. In the examples, parts are parts by weight, and viscosities are measured values at 25 ° C.

Reference Example 1 Preparation of Hydrogen Polysiloxane-Containing Capsule A In a 5 liter flask equipped with a stirrer, 20 mol% (M
e) ₂ SiO _2/2 units, 20 mol% of (Ph) ₂ SiO _2/2 units and
350 g of a thermoplastic silicone resin (softening point 92 ° C.) consisting of 60 mol% (Ph) SiO _3/2 units was homogeneously dissolved in 250 g of toluene and 450 g of methylene chloride. Then the formula:

[Chemical 7] A uniform solution was obtained by dissolving 100 g of hydrogen polysiloxane represented by Next, this solution was continuously sprayed into a spray dryer tank using nitrogen gas, and 425 g of polynuclear capsule fine particles containing hydrogen polysiloxane were collected by a bag filter. This was further washed with 500 g of hexadimethyldisiloxane and 418 g of polynuclear capsule A containing hydrogen polysiloxane was collected.
The content of the above hydrogen polysiloxane in this capsule A was 18% as measured by the amount of SiH.

Reference Example 2 Preparation of Hydrogen Polysiloxane-Containing Capsule B The hydrogen polysiloxane used in Reference Example 1 (100
g) is the following formula:

[Chemical 8] 402 g of Capsule B was collected in the same manner as in Reference Example 1 except that the hydrogen polysiloxane (100 g) represented by The content of hydrogen polysiloxane in this capsule B was 16%.

Reference Example 3 Preparation of Hydrogen Polysiloxane-Containing Capsules C In the same apparatus as in Reference Example 1, 55 mol% (Me) ₃ SiO _1/2 units and 45 mol% SiO _4/2 units were used. 350 g of the thermoplastic silicone resin (softening point 87 ° C.) was uniformly dissolved in 200 g of toluene and 600 g of methylene chloride. Then the formula:

[Chemical 9] A uniform solution was obtained by dissolving 100 g of hydrogen polysiloxane represented by Then, this solution was sprayed with a spray dryer in the same manner as in Reference Example 1, fine particles were collected with a bag filter, and this was further washed with hexadimethyldisiloxane to collect 431 g of hydrogen polysiloxane-containing polynuclear capsule C. . The content of hydrogen polysiloxane in the capsule C was 20%.

Example 1 Both ends of the molecular chain were blocked with dimethylvinyl groups, and the viscosity was
100 parts of 5,000cs dimethylpolysiloxane and a specific surface area of 200m ² / whose surface is hydrophobized with trimethylsilyl groups
20 parts of fumed silica (g) was heat treated for 2 hours under heating at 160 ° C. After cooling to room temperature, 0.02 parts of an octanol solution of chloroplatinic acid containing 2% by weight of platinum was added and mixed uniformly, and further 8.3 parts of hydrogen polysiloxane-containing capsule A and hydrogen polysiloxane were added. 7.5 parts of Capsule C was added and mixed to prepare a curable composition. The composition thus obtained was treated at 120 ° C × 10
Table 1 shows the physical properties of the sheet, which was press-molded for minutes and post-cured in an oven at 120 ° C for 50 minutes. Also this composition 25
Table 1 shows the viscosity and the sheet physical properties after being left for 1 month at ℃.

Comparative Example 1 100 parts of dimethylpolysiloxane having a dimethylvinyl group blocked at both ends of the same molecular chain as that used in Example 1 and 20 parts of the hydrophobic silica used in Example 1 were heat treated and cooled and then platinum was added. 0.02 parts of the compound was added and mixed uniformly. Up to this point, the procedure is the same as in the first embodiment. After that, a considerable amount of hydrogen siloxane contained in Example 1 (1.5 parts of the hydrogen siloxane used in Reference Example 1 and 1.0 part of the hydrogen siloxane used in Reference Example 3) was added and mixed. However, gelation progressed during mixing, and uniform mixing was impossible.

[0037]

[Table 1]

Example 2 Both ends of the molecular chain were blocked with dimethylvinyl groups, and the viscosity was 3
100 parts of 0000cs dimethylpolysiloxane, heavy silica powder
110 parts, 2 parts of fumed silica having a specific surface area of 200 m ² / g whose surface was hydrophobized with merimethylsilyl groups, and 0.1 part of an octanol solution of chloroplatinic acid containing 2% by weight of platinum were uniformly mixed. Further, 13.1 g of the capsule B containing hydrogen polysiloxane was added and uniformly mixed. Table 2 shows the initial physical properties of this material and the physical properties after 2 months at 25 ° C.

[0039]

[Table 2]

[0040]

The organopolysiloxane composition of the present invention is excellent in storage stability at room temperature for a long period of time, and when it is heated, it is rapidly and uniformly crosslinked to form a cured product.

Claims (2)

[Claims] 1. (A) Organopolysiloxane having at least two alkenyl groups in one molecule (B) (B-1) Hydrogen having at least two hydrogen atoms bonded to silicon atoms in one molecule It is composed of polysiloxane and (B-2) a thermoplastic resin having a softening point or glass transition point of 40 to 200 ° C. (B-1) is mononuclear or polynuclear and (B-2) is a wall material. And a heat-curable organopolysiloxane composition containing a platinum group metal-based catalyst (C). 2. A cured product obtained by curing the composition according to claim 1.