JPH04311764A - Curable organopolysiloxane composition - Google Patents

Abstract

PURPOSE:To obtain a curable organopolysiloxane composition suitable for electrolysis and electronic decomposition, extremely suppressing a low-molecular weight siloxane component content to a small amount and not causing contact disorder resulting from volatile low-molecular weight siloxanes without damaging curing characteristics. CONSTITUTION:A composition obtained by blending (A) an organopolysiloxane (e.g. compound shown by formula III) which is prepared by chain length extension by reacting an organopolysiloxane shown by formula I (R is 2-6C alkenyl; R<1> to R<4> are 1-10C hydrocarbon group) with an organopolysiloxane shown by formula II and subjecting to chain length extension with an organopolysiloxane containing two SiH groups in one molecule and has an alkenyl group at the ends of molecular chain with (B) an organohydrogen polysiloxane containing two or more SiH groups in one molecule and (C) a catalyst of platinum group metal, having <=100ppm content of low-molecular weight siloxane component having <=20 degree of polymerization.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an addition-curable curable organopolysiloxane composition containing no volatile low-molecular-weight siloxane.

0002

[Prior art] A curable organopolysiloxane in which an organopolysiloxane having alkenyl groups at both ends of the molecular chain and an organopolysiloxane having two or more SiH groups in one molecule are cured using a Pt-based hydrosilylation catalyst. The composition is already known and used for various purposes such as potting for electric/electronic parts, adhesives, and roll material for office machines. Recently, curable organopolysiloxane compositions have come to be used in large quantities in the electrical and electronic fields. Accordingly, there has been a need to prevent contact failure caused by volatile low-molecular-weight siloxanes contained in curable organopolysiloxane compositions.

0003

[Problems to be Solved by the Invention] Originally, if an organopolysiloxane containing no volatile low-molecular-weight siloxane was used as a raw material, it would be possible to prevent contact failure caused by low-molecular-weight siloxane. In order to make the polysiloxane composition excellent in physical properties such as strength, it is necessary to use a high molecular weight organopolysiloxane having alkenyl groups at both ends of the molecular chain used as a raw material. Removing low-molecular-weight siloxanes from high-molecular-weight organopolysiloxane polymers usually requires a long treatment process at high temperatures and reduced pressure, but it is possible to completely remove low-molecular-weight siloxanes from high-molecular-weight organopolysiloxanes. is economically disadvantageous, and it is difficult to treat at high temperatures for long periods of time, considering the stability of the vinyl groups contained in high molecular weight organopolysiloxanes.

[0004] Accordingly, an object of the present invention is to provide a curable organopolysiloxane composition in which the content of volatile low-molecular-weight siloxane is suppressed to a significantly small amount.

[0005]

[Means for achieving the object] According to the present invention, (A)
Organopolysiloxane whose chain length is extended by organopolysiloxane having two SiH groups in one molecule and which has alkenyl groups at both ends of the molecular chain; (B) organopolysiloxane having two or more SiH groups in one molecule; A curable organopolysiloxane composition containing a hydrogen polysiloxane and (C) a platinum group metal catalyst, and in which the content of each low molecular siloxane component with a degree of polymerization of 20 or less is suppressed to 100 ppm or less. provided. In this specification, the degree of polymerization refers to - contained in the molecule.
Refers to the number of Si-O- bonds.

(A) Organopolysiloxane In the present invention, the component (A) organopolysiloxane used as a base polymer has alkenyl groups at both ends of the molecular chain, and has two SiH groups in one molecule. The chain length has been extended by organopolysiloxane. By using such an organopolysiloxane as a base component, the degree of polymerization can be increased to 20% in the composition.
It becomes possible to suppress the content of each of the low molecular weight siloxane components (ie, 20-mer) or less to the order of 100 ppm or less.

The organopolysiloxane (a-1) used as a starting material for synthesizing the organopolysiloxane (A) is, for example, represented by the following general formula (1).

[Chemical formula 1]

In the above formula, R is an alkenyl group having 2 to 6 carbon atoms such as vinyl group, allyl group, isopropenyl group,
Preferably it is a vinyl group. That is, this alkenyl group present at the end of the molecule undergoes an addition reaction (hydrosilylation) with the SiH group in the organohydrodiene polysiloxane to elongate the chain.

[0009] R1 to R4 are the same or different unsubstituted or substituted monovalent hydrocarbon groups having 1 to 10 carbon atoms;
6 is preferred. Specifically, alkyl groups such as methyl group, ethyl group, propyl group, butyl group, cycloalkyl groups such as cyclohexyl group, aryl groups such as phenyl group and tolyl group, aralkyl groups such as benzyl group and phenylethyl group, and Groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms, etc., such as chloromethyl groups,
Examples include 3,3,3-trifluoropropyl group.

In the present invention, it is particularly preferable that the organopolysiloxane (a-1) whose chain length is to be extended has a viscosity in the range of 100 to 10,000 cSt at 25°C, and has the general formula ( In 1), m is
It is preferable to set the number such that the viscosity falls within the above range. That is, the volatile low-molecular-weight siloxane contained in the organopolysiloxane (a-1) having such a molecular weight range can be easily removed, for example, at a high temperature (usually 200
~300℃), reduced pressure (usually 0.1~10mmHg)
By carrying out the treatment under these conditions for a short time (usually 1 to 5 hours), each component of the low molecular weight siloxane having a degree of polymerization of 20 or less can be removed to an order of 100 ppm or less. Therefore, when removing low-molecular-weight siloxane, it is possible to effectively prevent adverse effects on the alkenyl groups at both ends of the molecular chain, which is extremely advantageous.

In the present invention, the organopolysiloxane (a-2) used as a chain extender for the organopolysiloxane (a-1) is represented by the following formula (2):

[
A linear organopolysiloxane represented by the following formula (3),

Examples include cyclic organopolysiloxanes represented by the following formula. In these formulas, R1 to R4 are each as described above, n is an integer of 0 to 20, and p is 1, 2 or 3.

That is, these organopolysiloxanes (
a-2) has two SiH groups in the molecule, and the chain length is extended by a hydrosilylation reaction between these SiH groups and the alkenyl group in the organopolysiloxane (a-1). It is.

In the present invention, the linear organopolysiloxane represented by the above formula (2) is represented by the following formula (4).
,

Dimethylpolysiloxanes of the formula ##STR4## are most commonly used.

Further, specific examples of the cyclic organopolysiloxane represented by the above formula (3) include the following formula (5),
Examples include those shown in (6), (7), and (8).

[C5]

[C6]

[C7]

[Chemical formula 8]

In these formulas, Me represents a methyl group and Pr represents a propyl group. Generally speaking, the amount of these organopolysiloxanes (a-2) used for chain lengthening is based on the alkenyl group of the organopolysiloxane (a-1) and the SiH group of the organopolysiloxane (a-2). It is desirable that the molar ratio between the two is in the range of 1 or more and less than 2.

[0016] Also, organopolysiloxane (a-1)
The hydrosilylation reaction between Platinic acid catalyst (U.S. Patent No. 2,823,218
(see US Pat. No. 3,159,601 and US Pat. No. 3,159,662), platinum-hydrocarbon complex compounds (see US Pat.
(see specification, etc.), chloroplatinic acid-olefin complex compound (
(see U.S. Pat. No. 3,516,946, etc.), platinum-vinylsiloxane complex (U.S. Pat. No. 3,775,4)
(See No. 52 and specification of No. 3,814,780, etc.)
This is carried out using platinum-based catalysts such as, palladium-based catalysts, rhodium-based catalysts, etc. Generally, platinum-based catalysts are particularly suitable as such catalysts, and the amount used is as follows:
It is preferably in the range of 0.1 to 1,000 ppm, particularly 1 to 100 ppm in terms of platinum group metal. The hydrosilylation reaction using such a catalyst is usually carried out at a temperature of 60 to 200°C for 0.5 to 5 hours.

In the present invention, an organopolysiloxane (A) whose chain length has been extended by such a hydrosilylation reaction is used as a base polymer. This organopolysiloxane (A) is represented by, for example, the following formula (9) or (10).

[Chemical formula 9]

[Chemical formula 10]

In these equations (9) and (10),
R, R1 to R4, m, n, and p are as described above, q is an integer of 2 to 6, r is an integer of 1 to 5, and x is an integer of 0 to 2 smaller than p.

(B) Organohydrodiene polysiloxane In the present invention, the organohydrodiene polysiloxane of component (B) acts as a crosslinking agent, and two or more SiH groups contained therein act as a crosslinking agent. A rubber elastic cured product is formed by addition reaction (hydrosilylation reaction) to the alkenyl groups at both ends of the molecule of the organopolysiloxane of A). This organohydrodiene polysiloxane may have a linear, cyclic, branched, or network structure as long as it has two or more SiH groups, and the SiH group may have a molecular chain. It may exist at the end of the chain, or it may exist in the middle of the molecular chain. In the present invention, the organohydrodiene polysiloxane commonly used has, for example, the following average composition formula: or an unsubstituted hydrocarbon group, b and c are each positive numbers, and b+
c is a number satisfying 0.6 to 3.0, and has at least two silicon-hydrogen bonds in the molecule. In this average compositional formula, suitable examples of the group R include R1 to R1 in the component (A) above.
Examples of groups similar to R4 include alkyl groups such as methyl, ethyl, propyl, and butyl, aryl groups such as phenyl and tolyl, and 3,3,3-trifluoropropyl groups. . Specific examples of such organohydrodiene polysiloxanes include the following formula (11):
- (18) can be exemplified.

[0020]

[Chemical formula 11]

[Chemical formula 12]

[Image Omitted] In the above formula, b, c, d, e, f, g, i
represents 0 or a positive integer, h represents an integer of 2 or more, and the number of silicon atoms in the molecule is usually 400 or less.

[0021]

[Chemical formula 14]

[Chemical formula 15]

[Chemical formula 16]

[Chemical formula 17]

embedded image In the above formula, R5 represents a hydrogen atom, a methyl group, a propyl group or a trimethylsiloxy group.

[0022] These organohydrodiene polysiloxanes have a SiH group of 1 mole of alkenyl group contained in the organopolysiloxane of component (A),
It is used in a proportion of 0.5 to 3.0 mol, especially 1.0 to 2.0 mol. These may be used alone or in combination.
Can be used in combination of more than one species.

(C) Platinum Group Metal Catalyst In the present invention, a platinum group metal catalyst is used to accelerate curing by the above-mentioned hydrosilylation reaction. As this catalyst, catalysts similar to those used for chain length extension by the hydrosilylation reaction described above can be used alone or in combination of two or more types, but platinum-based catalysts are particularly preferably used. can.

These platinum group metal catalysts contain component (A)
0.1 to 1,000 ppm, especially 1 in terms of platinum group metal, based on the total amount of the organopolysiloxane of Component (B) and the organohydrodiene polysiloxane of Component (B).
It is preferably used in a proportion of ~100 ppm.

Other compounding agents In addition to the above-mentioned components (A) to (C), the composition of the present invention may contain, for example, methyl vinylcyclo to ensure storage stability at room temperature and an appropriate pot life. A reaction control agent such as tetrasiloxane or acetylene alcohol may be appropriately blended.

[0026]Furthermore, fillers may be added to the composition of the present invention for the purpose of reinforcement or weight increase, if necessary. Known fillers are used, such as fumed silica, precipitated silica, ground silica, finely powdered silica such as fused silica powder, diatomaceous earth, iron oxide, zinc oxide, titanium oxide, carbon black, barium oxide, and oxidized silica. Metal oxides such as magnesium, metal carbonates such as cerium hydroxide, calcium carbonate, magnesium carbonate, zinc carbonate, asbestos, glass wool, glass fiber, fine mica, carbon black, or chain organopolysiloxane , cyclic organopolysiloxane, hexamethyldisilazane, etc. to make the surface hydrophobic. Furthermore, if necessary, thixotropic agents such as polyethylene glycol and its derivatives, pigments, dyes, antiaging agents, antioxidants, antistatic agents, flame retardants such as antimony oxide and chlorinated paraffin, boron nitride, aluminum oxide, It is optional to add thermal conductivity improvers such as Various conventionally known additives such as additives may be mixed.

[0027] Furthermore, plasticizers, anti-sagging agents, antifouling agents, preservatives, bactericidal agents, antifungal agents, and the like may be added.

Preparation of Composition The curable organopolysiloxane composition of the present invention is prepared by preparing the organopolysiloxane of component (A) in advance by preparing 2
00-300 °C, especially 230-280 °C, and 1
Heat treatment is performed under conditions of 0 mmHg or less, especially 3 mmHg or less, and the content of each component of the low molecular weight siloxane with a degree of polymerization of 20 or less is adjusted to 100 ppm or less, and after this, component (A) and other components are uniformly mixed. Obtained by mixing. In this case, if the heat treatment temperature is higher than the above range, the stability of the alkenyl group at the end of the molecule will be impaired, making it difficult to obtain a cured product with good physical properties. In addition, when the heat treatment temperature is lower than the above range or when the reduced pressure condition is higher than the above range, the content of each component of the low molecular weight siloxane with a degree of polymerization of 20 or less is 100 ppm.
It becomes difficult to adjust the following. According to the present invention, by performing heat treatment under the above conditions, for example,
It becomes possible to adjust the content of the low-molecular-weight siloxane component within a treatment time of about 5 hours, thereby effectively maintaining the stability of the alkenyl groups present at both ends of the molecular chain.

Further, uniform mixing of each component is carried out using various kneading machines such as a Banbury mixer, an extruder, and a kneader.
This is done by mixing at a temperature of 200°C.

Curable organopolysiloxane composition The composition of the present invention obtained as described above has a curable organopolysiloxane composition of 60 to 20
A cured product of the rubber elastic body is formed by heating at a temperature of 0° C. for 0.5 to 5 hours. The composition of the present invention has a content of low molecular weight siloxane with a degree of polymerization of 20 or less of 100 p.
pm or less, and as a result, when used in the electrical and electronic fields, it has the remarkable advantage of not causing contact failure problems.

The composition of the present invention can be diluted with a hydrocarbon solvent such as toluene, xylene, or petroleum ether, or a solvent such as ketones or esters in order to coat it on a suitable substrate. It is also possible to provide

[0032]

[Example] Synthesis Example 1 18.6 g of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane and 2960 g of octamethyltetrasiloxane were charged into a flask, and further,
2 g of siliconate containing 10% K was added as a catalyst, and the mixture was reacted at 150°C for 5 hours. Next, after cooling to 80° C., carbon dioxide gas was blown into the reactor to neutralize the catalyst. The obtained silicone oil was heated to 250℃,
It is treated under conditions of 3 mmHg to remove volatile components, contains vinyl groups at both ends, and has a viscosity of 5,500 cS at 25°C.
It is t. Dimethylpolysiloxane was obtained. The vinyl group content of this dimethylpolysiloxane is 0.0068 m
ol/100g, and the amount of low molecular weight siloxane with a low degree of polymerization contained therein was as follows (measured by gas chromatography). Degree of polymerization: 3-15; each component: 10 ppm or less Degree of polymerization: 15-17; each component: 20 ppm
Polymerization degree below: 18-20; 30 ppm for each component
Below, add 1000g of this dimethylpolysiloxane,
HMe2 SiO(Me2 SiO)10SiMe2
After adding 30 g of H and 30 ppm of chloroplatinic acid (in terms of platinum) and reacting at 100 to 120 °C for 5 hours, the mixture was treated at 150 °C and 3 mmHg for 2 hours to give a viscosity of 55,000 cSt (at 25 °C). A dimethylpolysiloxane (polymer (a)) with an extended chain length was obtained. The content of low molecular weight siloxane in this product was as follows. Degree of polymerization: 3-15; each component: 10 ppm or less Degree of polymerization: 15-17; each component: 20 ppm
Polymerization degree below: 18-20; 30 ppm for each component
Below, the vinyl group content is 0.0033 mol/
It was 100g.

Synthesis Example 2 The same procedure as Synthesis Example 1 was carried out except that the amount of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane used was changed to 9.3 g. A dimethyl polysiloxane (polymer (b)) having a viscosity of 60,000 cSt (25° C.) before chain length extension was obtained. The vinyl group content was 0.0034 mol/100g, and the low molecular weight siloxane content was as follows. Degree of polymerization: 3 to 10; each component: 10 ppm or less Degree of polymerization: 11 to 14; each component: 30 ppm
Polymerization degree below: 15-17; 50 ppm for each component
Polymerization degree below: 18-20; each component: 150p
pm~100ppm

Examples and Comparative Examples For 100 parts by weight of each of polymers (a) and (b) obtained in the synthesis example above, the specific surface area was 200 m2/
25 parts by weight of dry silica of 1 g was mixed in a kneader.
Heat treated at 50°C for 3 hours to form base compound (A)
and (b) were prepared. These base compounds
100g of the following formula Me3SiO(Me2Si
O) Organohydrodiene polysiloxane represented by 10(MeHSiO)5 SiMe3 9.8
g and 100 ppm (in terms of platinum) of chloroplatinic acid were added, and the mixture was cured at 120° C. for 30 minutes to prepare a 2 mm thick cured rubber sheet. This cured sheet is JI
When the physical properties were measured according to SK-6301, the results were as shown in Table 1. Further, 5 g of these cured rubber sheets were swollen in 100 g of toluene to extract the low molecular weight siloxane contained therein, and then analyzed by gas chromatography. The results are also shown in Table 1.

[0035]

[Table 1]

[0036]

According to the present invention, it is possible to suppress the content of the low molecular weight siloxane component in the curable organopolysiloxane composition to 100 ppm or less without impairing the curing properties or the like. This composition does not cause contact failure and
Effectively used in electrical and electronic fields.

Claims (2)

[Claims] Claim 1: (A) The chain length is extended by an organopolysiloxane having two SiH groups in one molecule, and
An organopolysiloxane having alkenyl groups at both ends of the molecular chain, (B) an organohydrodiene polysiloxane having two or more SiH groups in one molecule, and (C) containing a platinum group metal catalyst and having a polymerization degree A curable organopolysiloxane composition in which the content of each low molecular weight siloxane component of 20 or less is suppressed to 100 ppm or less. 2. A cured product obtained by curing the composition of claim 1.