JPH0218451A - Polyorganosiloxane composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition having excellent storage stability at room temperature, crosslinkable and curable in extremely short time with heat by addition reaction and suitable as a potting material, etc., by compounding a specific polyorganohydrogensiloxane and a platinum-based catalyst. CONSTITUTION:(A) An alkenyl-containing polyorganosiloxane having the constituent unit of formula I [R<1> is alkenyl; R<2> is (substituted)univalent hydrocarbon group free from aliphatic unsaturated bond; a is 1-3; b is 0-2; a+b is 1-3] with (B) a polyorganohydrogensiloxane having a constituent unit of formula II [R<3> is (substituted)univalent hydrocarbon group; c is 0-2; d is 1-3; c+d is 1-3] and (C) a platinum-based catalyst which is a mixture of one or more components selected from platinum group metals and platinum group compounds and benzonitrile and/or a benzonitrile complex of the above components.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention relates to a polyorganosiloxane composition, which has particularly excellent storage stability at room temperature, and when heated, it undergoes an addition reaction in an extremely short period of time. The present invention relates to a polyorganosiloxane composition that is crosslinked and cured.

(Prior Art and Problems to be Solved by the Invention) Addition reaction curable compositions containing alkenyl group-containing polyorganosiloxanes, polyorganohydrodiene siloxanes, and platinum-based catalysts as main components are conventionally known. However, if these compositions are stored at room temperature for a long period of time, they may become inconvenient, such as thickening or gelling. Therefore, in practical use, these compositions can be stored stably at room temperature for a long period of time in the form of a mixture of their components, and they cannot be heated. There has been a demand for something that will only harden when it is cured.

Various compositions containing additives for imparting storage stability at room temperature have been proposed.
25069), acetylene-containing alcohol (Japanese Patent Publication No. 44-31476), acrylonitrile (Japanese Patent Publication No. 45-22018), and 2-pentenenitrile (Japanese Patent Publication No. 61-211364). However, these storage stabilizers do not have sufficient stabilizing effects, and the compositions tend to thicken or gel when stored at room temperature for a long time.

Therefore, if a large amount of these storage stabilizers is used to sufficiently suppress this thickening, heat curing may require high temperatures or a long time, or the storage stabilizers may not be compatible with polysiloxane. However, it has the disadvantage of phase separation during storage at room temperature. Furthermore, when a large amount of acetylene group-containing alcohol or acrylonitrile is added, if hot air curing is performed in an atmosphere at a high temperature of about 150°C, curing progresses from the surface, resulting in fine wrinkles and unevenness on the surface. However, there was a drawback that the commercial value of the cured product was significantly reduced.

In this way, with conventional technology, thickening and gelation are suppressed during long-term storage at room temperature, and during heat curing, it is cured uniformly in a short time by relatively gentle heating, and it is cured using high-temperature hot air. However, an addition reaction type polyorganosiloxane composition that could be uniformly cured without causing wrinkles or unevenness on the surface could not be obtained.

The present invention solves the drawbacks of the prior art, has excellent long-term storage stability, cures uniformly in a short time by relatively gentle heating, and uses high-temperature hot air to shorten the time. An object of the present invention is to provide an addition reaction type polyorganosiloxane composition that can be uniformly cured without causing wrinkles, unevenness, etc. on the surface even when cured.

[Structure of the Invention] (Means and Effects for Solving the Problems) As a result of extensive studies to achieve the above object, the present inventors have discovered that benzonitrile is an additive for addition reaction type polyorganosiloxane compositions. The present invention has been achieved based on the discovery that it is extremely effective to use a polyorganosiloxane composition, and that it is even more effective to coordinate benzonitrile to platinum or a platinum compound in an addition reaction type polyorganosiloxane composition.

That is, the polyorganosiloxane composition of the present invention has the following formula: ; a represents an integer of 1 to 3; b represents an integer of θ to 2; a+b represents an integer of 1 to 3), an alkenyl group-containing polyorganosiloxane, (B) General formula % formula % [] (wherein R3 represents a substituted or unsubstituted monovalent hydrocarbon group; C represents an integer of O to 2; d represents an integer of 1 to 3; c+d represents 1 to 3 (representing an integer of It is characterized by being a mixture with a nitrile and/or a benzonitrile complex.

The alkenyl group-containing polyorganosiloxane as component (A) used in the present invention has an alkenyl group directly bonded to a silicon atom, and may be either linear or branched, or a mixture thereof. Good too.

Examples of the alkenyl group represented by R1 in the above-mentioned -sludge [II include vinyl group, allyl group, l-butenyl group, 1-hexenyl group, etc., but vinyl group is the most advantageous from the viewpoint of ease of synthesis. .

Substituted or unsubstituted hydrocarbon groups bonded to the silicon atom of R2 and other siloxane units include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl groups; such as phenyl groups; Aryl group;
Examples include aralkyl groups such as 2-phenylethyl group and 2-phenylpropyl group, and furthermore, chloromethyl group,
3.3.3-) Substituted hydrocarbon groups such as the trifluoropropyl group may also be mentioned by way of example. Among these, the methyl group is most preferred because it is easy to synthesize, has the degree of polymerization of the polyorganosiloxane necessary to maintain good physical properties after curing, and maintains a low viscosity before curing.

In addition, if it is necessary for the cured product to become a rubber elastic body,
The number of alkenyl groups is preferably two or more bonded in one molecule of (A), and the unit represented by formula [II may be present either at the end or in the middle of the molecular chain of the polyorganosiloxane. , or both, but in order to impart excellent mechanical properties to the cured composition, it is preferable that it be present at least at the ends.

The viscosity of this component (A) is not particularly defined, but when it is used as a base polymer for an addition reaction type composition, it is preferably 20 cSt or more at 25°C.

The polyorganohydrodiene siloxane (B) component used in the present invention is an essential component that turns the composition into a rubber elastic body or gel-like material through an addition reaction with (A) m component.

The substituted or unsubstituted hydrocarbon group bonded to the silicon atom of R3 and other siloxane units in the above formula [II] include R2. in the above-mentioned component (A). The same polyorganohydrodiene siloxanes are exemplified, but from the viewpoint of ease of synthesis, a methyl group is most preferred.The polyorganohydrodiene siloxane may be linear, branched or cyclic. , or a mixture thereof.

Specific examples of component (B) include the following.

a, (CH3)2H3i03. A branched polyorganohydrodiene siloxane 50-order formula consisting of : (where p is l-100 and q is an integer from θ to 100)
The amount is such that the number of hydrogen atoms bonded to silicon atoms in component (B) is 0.2 to 10, preferably 0.2 to 5.

0.2 to 0 if you want to obtain a gel-like cured product with buffering properties.
．． The number of hydrogen atoms is preferably in the range of 8, and when it is desired to obtain a rubber-like elastic body, the number is preferably in the range of 0.8 to 5.0.
If the number of hydrogen atoms is less than 2, the curing of the composition will not proceed sufficiently because the crosslinking density will be too low, and the physical properties such as fluidity will deteriorate even after curing, which is undesirable. It is not preferable because it tends to foam during curing and the heat resistance of the cured product decreases.

Next, component (C), which is a feature of the present invention, will be described.

The platinum-based catalyst as component (C) is a mixture and/or benzonitrile complex of one or more selected from platinum-based metals and platinum-based compounds and benzonitrile.

Here, platinum-based metals include simple platinum (platinum black), simple palladium (palladium black), and simple rhodium.
In addition, platinum-based compounds include chloroplatinic acid, platinum-olefin complexes, platinum-alcohol complexes, platinum-ketone complexes, platinum-vinylsiloxane complexes, tetrakis(triphenylphosphine)platinum, tetrakis(triphenylphosphine)platinum, phosphine) palladium, etc. Among these, it is preferable to use chloroplatinic acid or a platinum-olefin complex dissolved in an alcohol solvent, a ketone solvent, an ether solvent, a hydrocarbon solvent, etc.; It is necessary to finely grind the particles to improve the quality of the particles, and it is preferable that the carrier used has a small particle size and a large specific surface area.

The benzonitrile used in the present invention imparts storage stability to the composition of the present invention at room temperature, and at the same time makes temperature dependence extremely large during heat curing, and also provides uniform curability even in hot air curing at high temperatures. It is a characteristic ingredient that gives

Benzonitrile may be used as it is by mixing with the platinum-based metal or platinum-based compound described above, but the effects of the present invention are further exhibited when used in the form of a complex thereof. Such complexes include Pt (Ca Hs CN) 2 C12, H2Pt
(Co Hs CN) 2 C12 etc. are exemplified. These can be purchased as commercial products, but they can also be obtained by heating a platinum-based metal or a platinum-based compound at about 100° C. for several hours.

The amount of component (C) used is 0.1 to 500 ppm as the amount of platinum atoms and 0.1 to 11,000 ppm as the amount of benzonitrile relative to component (A).

If the amount of platinum atoms is less than 0.1 ppm, the curability of the composition is insufficient, while if it exceeds 500 ppm, it will adversely affect the properties after curing.
A 0.3 to 200 pp layer is preferred.

Furthermore, if the amount of benzonitrile is less than 0.1 pp layer, the curing suppressing effect at room temperature will not be exhibited;
The amount of benzonitrile that exceeds ppm causes poor curing, and is preferably 0.3 to 200 ppm.

The composition of the present invention includes each component (A) to (C),
By adding an inorganic filler as necessary, it is possible to provide flowability, hardness after curing, tensile strength, elongation, modulus, etc. suitable for the application. Such inorganic fillers typically include fumed silica, silica aerogel, precipitated silica, ground silica, silica, iron oxide, zinc oxide, titanium oxide, calcium carbonate, magnesium charcoal, zinc carbonate, carbon black, etc. is exemplified. The amount of these fillers to be used is arbitrary as long as the purpose of the present invention is not impaired. Further, appropriate pigments, dyes, adhesion aids, fungicides, heat resistance improvers, flame retardants, or antioxidants may be added if necessary. Furthermore, when carrying out the present invention, the composition of the present invention may be used after being dispersed or dissolved in a suitable organic solvent such as toluene or xylene, depending on the use.

[Effects of the Invention] The polyorganosiloxane composition of the present invention can be stored stably at room temperature for a long period of time, and when heat-cured, the temperature dependence of curing is significantly greater than in the past, so it can be cured quickly by gentle heating. , and even when hot air curing is performed at high temperatures, it can be uniformly cured from one surface to the inside without causing wrinkles or unevenness on the surface.

Therefore, by using the polyorganosiloxane composition of the present invention, it is possible to shorten the manufacturing process of products using it, and it is also possible to extend the working time for handling these products. Furthermore, energy saving is possible by low temperature heat curing.

The polyorganosiloxane composition of the present invention can be used as a botting material and coating material in the electrical and electronic industries, as well as a dipping material in general industry, a rubber material for molding molds, a molding material, a coating material for release paper, and a dental material. It is suitable for a wide range of applications such as addition reaction type silicone rubber such as impression materials, silicone gel, etc., and its usefulness is great.

(Example) The present invention will be explained below with reference to Examples. In addition, in the examples, all parts indicate parts by weight.

All viscosities refer to viscosity at 25°C.

Example 1 100 parts of polydimethylsiloxane having a viscosity of 350 cP and having both molecular chain ends capped with dimethylvinylsilyl groups, both molecular chain ends being capped with trimethylsilyl groups, and the main chain having 60 mol% of methylhydrodienesiloxane units and the remainder. 4 parts of polymethylhydrodiene siloxane with a viscosity of 10 cP and an average particle size of 5 gm.
A base composition was obtained by uniformly mixing 150 parts of pulverized silica.

To 254 parts of this base composition, 0.0025 parts of an octatool complex containing 3.6% by weight of platinum and 0.00 parts of benzonitrile were added.
．． 0065 parts were added thereto and stirred and mixed to obtain a composition AI of the present invention.

This composition was left at 25°C and the change in viscosity was measured. In addition, this composition was cured by heating at 100' for 0.30 minutes, and 5' in hot air at 150°C.
The surface conditions after curing were observed for those cured by heating for a minute, and the results are shown in Table 1.

Comparative Example 1 Composition B1 was obtained in the same manner as in Example 1 except that benzonitrile was not used. This composition was evaluated in the same manner as in Example 1, and the results are also listed in Table 1.

Comparative example 2 0.00 acrylonitrile instead of benzonitrile
Composition B was prepared in the same manner as in Example 1 except that 30 parts were used.
2 was obtained, and this composition was evaluated in the same manner as in Example 1, and the results are also listed in Table 1.

Comparative Example 3 0.2-pentenenitrile was used instead of benzonitrile.
Composition B3 was obtained in the same manner as in Example 1, except that 0.050 parts of the composition was used. This composition was evaluated in the same manner as in Example 1, and the results are also shown in Table 1.

Example 2 100 parts of platinum chloride and 1400 parts of benzonitrile were placed in a flask equipped with a thermometer, a stirrer, and a reflux tube, the inside was purged with nitrogen, and the mixture was heated and stirred at 100°C for 2 hours. Next, n-hexane was added to the reaction mixture cooled to 30° C. or below while stirring slowly to completely precipitate the benzonitrile complex of platinum chloride. The precipitate was suction filtered using a glass filter, washed with n-hexane, and then dried to obtain 170 parts (yield: 95%) of a benzonitrile complex of platinum chloride in the form of a yellow powder.

The benzonitrile complex of platinum chloride thus obtained was added to a mixed solution of 200 parts of triphenylphosphine and 500 parts of isopropanol in an amount giving a platinum concentration of 5% by weight, and stirred at 80°C for 1 hour. A benzonitrile complex solution of platinum chloride (platinum amount: 5.0% by weight) was obtained.

0.002 part of the complex solution (platinum content: 5.0% by weight) obtained as described above was added to the base composition 2 obtained in Example 1.
The mixture was added to 54 parts and mixed with stirring to obtain Composition A2 of the present invention.

This composition A2 was evaluated in the same manner as in Example 1,
The results are also listed in Table 1.

Claims (1)

[Claims] (A) General formula (R^1)_a(R^2)_bSiO_{_4_-_(
_a_+_b_)_}_/_2 (wherein, R^1 represents an alkenyl group; R^2 represents a substituted or unsubstituted monovalent hydrocarbon group that does not contain an aliphatic unsaturated bond; a is 1- 3
b represents an integer from 0 to 2; a+b represents an integer from 1 to
An alkenyl group-containing polyorganosiloxane having a structural unit represented by (B) the general formula (R^3)_cH_dSiO_{_4_-_(_c_+
_d_)_}_/_2 (wherein, R^3 represents a substituted or unsubstituted monovalent hydrocarbon group; c represents an integer of 0 to 2; d represents an integer of 1 to 3; c+d represents an integer of 1 to 3), and (C) a platinum-based catalyst, where (C) is one or two selected from platinum-based metals and platinum-based compounds. A polyorganosiloxane composition characterized in that it is a mixture of at least one species with benzonitrile and/or a benzonitrile complex.