JPS6217625B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to curable silicone compositions, and more particularly to curable silicone compositions containing fine powders of transition metals such as tungsten and silver. Silicone, particularly silicone rubber, has excellent thermal stability and cold resistance, and has characteristics such as electrical insulation, weather resistance, and low toxicity, and is therefore widely used as an electrical insulating material and a medical material. It has long been proposed that by blending various metal fine powders with this material, it can be used as a conductive material or for special purposes. For example, those containing fine powders of silver and copper are expected to be used as conductive materials, and those containing fine powders of tungsten are useful as X-ray shielding materials, contrast materials, vibration-proofing materials, etc. - Publication No. 19878 describes that it has the advantage of not causing blood coagulation when used as a contrast material in blood vessels. However, silicone rubber containing a large amount of transition metals such as silver and tungsten cannot be stably produced industrially by the methods proposed so far. There are two methods for curing silicone rubber by heating. The first is a curing method by heating a polyorganosiloxane, preferably a polyorganosiloxane in which a vinyl group bonded to a silicon atom is present, in the presence of an organic peroxide,
The second method is to prepare a polyorganosiloxane in which at least two vinyl groups are bonded to silicon atoms in one molecule in the presence of a platinum catalyst, and the average number of hydrogen atoms bonded to silicon atoms exceeds two in one molecule. This method involves heating together with the polyorganohydrodiene siloxane present. However, taking the above-mentioned fine tungsten powder as an example, the method using an organic peroxide results in insufficient curing, making it impossible to obtain a rubber elastic body with satisfactory mechanical properties. Also,
Even in methods using platinum catalysts, most platinum causes poor curing due to poisoning by transition metals. For example, the composition described in the above-mentioned Japanese Patent Publication No. 19878 did not cure at all even when using chloroplatinic acid or an organic peroxide, or the catalyst was poisoned during standing and hardened. On the other hand, it is extremely unstable and hardens even at room temperature in a short period of time, resulting in poor workability and impractical properties. This also applies to silicone rubbers containing silver and other transition metals. As a result of repeated research in order to solve the problems of poor curing and scorch, the inventors of the present invention have found that
By carrying out the above-mentioned second curing method using a platinum complex that does not contain a chlorine atom in the molecule, such as a (0)valent platinum-phosphorus complex or a platinum-acetylacetonate complex, as a catalyst. It was discovered that a silicone rubber containing fine powder of a transition metal can be obtained (Japanese Patent Application No. 121403-1983). Although these complexes are excellent catalysts for industrially producing silicone rubber containing transition metals such as tungsten and silver, they do not have sufficient storage stability, and unblended catalysts must be stored frozen. , or must be sealed in a nitrogen stream. Therefore, the development of a catalyst system that is suitable for obtaining silicone rubber by curing a silicone rubber compound containing transition metals, does not lose catalytic activity due to transition metals, and has excellent storage stability remains an issue. It was done. As a result of further research to solve this problem, the present inventors discovered a catalyst system in which the above-mentioned platinum complex containing no chlorine atom was blended with an organic peroxide containing no hydroperoxy bond, or a catalyst system in which both were reacted. By using the product obtained as a curing catalyst, a catalyst system with extremely excellent storage stability can be obtained.
It was discovered that this catalyst system can cure a silicone rubber compound to form a silicone rubber even in the presence of fine powder of transition metals such as tungsten, in the same way as using the above-mentioned platinum complex alone. I was able to accomplish this. That is, the present invention provides (A) 100 parts by weight of a polyorganosiloxane in which at least two vinyl groups bonded to silicon atoms exist in one molecule, and (B) an average of 2 hydrogen atoms bonded to silicon atoms in one molecule. (C) 5 to 500 parts by weight of transition metal fine powder, and (D) (1) (a) a platinum complex containing no halogen atoms in the molecule; (b) a catalyst composition comprising an organic peroxide in which no hydroperoxy bond is present in the molecule; and (2) a catalyst system or catalyst selected from the group consisting of the reaction product of (a) and (b). A curable composition comprising: The polyorganosiloxane (A) used in the present invention may have a linear, branched, or cyclic siloxane skeleton, but in order to be cured by the platinum catalyst (A), silicon It is necessary that at least two vinyl groups bonded to atoms exist in one molecule. Examples of organic groups bonded to silicon atoms include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, and dodecyl, aryl groups such as phenyl, and β-phenylethyl. Examples thereof include aralkyl groups such as 3,3,3-trifluoropropyl groups, and substituted hydrocarbon groups such as 3,3,3-trifluoropropyl groups. Furthermore, the presence of a hydroxyl group at the end of the molecule is also allowed.
Among the organic groups other than the vinyl group mentioned above, good heat resistance and mechanical properties are obtained, and raw materials are easily available.
In addition, since it is easy to synthesize, it is preferable to use a combination of a methyl group and a phenyl group, or only a methyl group. In particular, when the cured product is a rubber-like elastic body, it is preferable to use only methyl groups, unless properties such as cold resistance or radiation resistance are required. When the cured product is resin-like, the average degree of polymerization is 2.
A relatively low range of ~40 is sufficient, but when the cured product is a rubber-like elastic body, the average degree of polymerization needs to be 100 or more in order to obtain good rubber elasticity. Among these, the uncured composition is fluid and has a low average degree of polymerization for use in casting, potting, etc.
The range is preferably from 100 to 1000, and the siloxane skeleton is linear or branched. In particular, for ease of synthesis and for the cured product to have good mechanical properties, it is preferred that the molecular terminals be capped with a dimethylvinylsiloxy group and that the organic groups in the other siloxy units be methyl groups. In order for the uncured composition to be in solid form and to be molded by press vulcanization or extrusion, and for the cured product to have high mechanical properties,
It is preferable that the siloxane skeleton has an average degree of polymerization of 1000 to 10000 and is substantially linear, and 3000 to 10000.
More preferably, it is in the range of 10,000. When the average degree of polymerization exceeds 10,000, it becomes difficult to blend (C) transition metal fine powder, reinforcing filler, and the like. The amount of vinyl groups bonded to silicon atoms ranges on average from 0.005 to 0.5% of the total organic groups. This is because if the amount of vinyl groups is less than 0.005%, good mechanical properties cannot be obtained, and if it exceeds 0.5%, heat resistance decreases. The polyorganohydrodiene siloxane (B) used in the present invention is a crosslinking agent for the polyorganosiloxane (A), and may have a chain, branched, or cyclic siloxane skeleton, but by crosslinking, a network In order to form a structure, it is necessary that the number of hydrogen atoms bonded to silicon atoms be more than two on average in one molecule. Examples of the organic group bonded to the silicon atom include those similar to the polyorganosiloxane (A) and a vinyl group, but a methyl group is preferred from the viewpoint of ease of synthesis and heat resistance of the cured product. Although the average degree of polymerization is not particularly limited, it is generally in the range of 4 to 3,000 and preferably. Those with an average degree of polymerization of less than 4 are highly volatile and difficult to handle, while those with an average degree of polymerization of over 3000 are difficult to synthesize. The blending amount of (B) is the polyorganosiloxane of (A).
The amount is 0.1 to 10 parts by weight per 100 parts by weight. The transition metal fine powder (C) used in the present invention is used to impart conductivity, X-ray shielding properties, and other properties suitable for special uses of the cured product, and the atomic number 21 (Sc) to 29 (Cu), 39 (Y) to 47 (Ag), and 57
Elements from (Ia) to 79 (An) are applicable, and examples include iron, cobalt, nickel, copper, molybdenum, silver, and tungsten. The blending amount of (C) is the polyorganosiloxane of (A).
5 to 500 parts by weight per 100 parts by weight, preferably 5
~100 parts by weight. This is because if the amount is less than 5 parts by weight, the intended properties of each transition metal added will not be sufficiently expressed, and if it exceeds 500 parts by weight, the mechanical properties will deteriorate. The catalyst system (D) used in the present invention is (1) (a) described below.
and (b), or (2) a reaction product of both. The platinum complex (a) used in the present invention does not contain a halogen atom in its molecule, and has a (0) valent platinum complex.
Examples include phosphorus complexes and platinum-acetylacetonate complexes. Platinum with a chlorine atom in the molecule, such as chloroplatinic acid commonly used in this type of reaction, complexes obtained from it and alcohols, olefins, and vinyl group-containing siloxanes, and divalent platinum-phosphorus complexes. Catalysts are not used in the present invention because they inhibit vulcanization and cause scorch in the presence of fine transition metal powder. The (0)-valent platinum-phosphorus complex has the general formula Pt[PR ₃ ] ₄ (where R represents a monovalent group selected from the group consisting of a monovalent hydrocarbon group, an alkoxy group, and an aryloxy group). ), tetrakis (triethylphosphine) platinum, tetrakis (tributylphosphine) platinum,
Examples include tetrakis(triphenylphosphine)platinum, tetrakis(trimethylphosphite)platinum, tetrakis(triethylphosphite)platinum, tetrakis(tributylphosphite)platinum, and tetrakis(triphenylphosphite)platinum. The platinum-acetylacetonate complex is Pt
(acac) ₂ (acac indicates acetylacetonate). These platinum complexes may be used as they are, or may be used after being dissolved in an organic solvent such as ethylene glycol dimethyl ether, ethanol, or isopropanol. The curable composition of the present invention can be obtained by using a platinum complex alone, but in that case, the complex itself gradually decomposes in air at room temperature, so it is usually stored in a freezer or sealed under a nitrogen atmosphere. It must be stored in a tube and used. The organic peroxide (b) of the present invention is added precisely to increase the stability of this platinum complex. Addition of this component enables storage at room temperature in air, prevents destabilization of catalyst activity caused by catalyst decomposition, and ensures stable vulcanization molding. Moreover, even when component (a) was used after reacting with component (b) in advance, its vulcanization properties did not change at all, and the stability of the catalyst at room temperature was also extremely good. Examples of this organic peroxide include di-t-butyl peroxide, 2,5-
Dimethyl-2,5-di(t-butylperoxy)
Hexane, 2,5-dimethyl-2,5-di(t-
butylperoxy)hexyne-3, dicumyl peroxide, t-butylcumyl peroxide, α,
Dialkyl peroxides such as α′-bis(t-butylperoxy)isopropylbenzene, or derivatives thereof, benzoyl peroxide, p-
Diacyl peroxides such as chlorobenzoyl peroxide, m-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, peracid esters such as t-butyl perbenzoate, diisopropyl perdicarbonate, di-2 perdicarbonate - peroxydicardonates such as ethylhexyl, peroxyketals such as 1,1,-di(t-butylperoxy)cyclohexane, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, etc. is exemplified. In addition, those in which a hydroperoxy bond is present in the molecule are not suitable for the purpose of the present invention because they foam when the composition is heated and cured. The amount of (A) is an effective amount as a catalyst.
0.1~ for polyorganosiloxane
A range of 1000 ppm is recommended, but there is an appropriate range depending on the type and amount of transition metal fine powder to be blended, so it must be selected carefully. It is recommended that the amount of organic peroxide in (B) be less than 0.1 to 1000 ppm based on the polyorganosiloxane in (A), but within this range, it should be It is preferably 2 to 1000 equivalents, more preferably 10
~200 equivalents. If the amount is less than 2 equivalents, the catalyst will not be sufficiently stabilized, and if it is more than 1000 equivalents, harmful peroxide decomposition products will remain in the system, which is also economically unfavorable. The composition of the present invention is characterized in that it is obtained by blending (B) to (D) with (A), but if mechanical properties are required, other inorganic fine powders may be added. is preferred. As the inorganic fine powder, fine powdered silica is preferable because it has a large reinforcing effect and has no effect on the platinum catalyst. Examples of fine powder silica include fumed silica, precipitated silica, and calcined silica. These finely powdered silicas have an adverse effect on the processability of the composition and the electrical and mechanical properties of the cured product due to the polarity and hydrophilic nature of the large amount of silanol groups present on the surface. Therefore, depending on the purpose of use, it is recommended that the surface of these finely powdered silicas be treated with an organosilicon compound such as a chain polyorganosiloxane, a cyclic polyorganosiloxane, or hexamethyldisilazane. Further, when a reinforcing effect is not necessarily required and only hardness is to be increased, a material having a relatively large particle size such as crushed quartz may be used. The amount of finely powdered silica added is 100% of the polyorganosiloxane (A).
A range of 10 to 100 parts by weight is preferred. If it is less than 10 parts by weight, no reinforcing effect can be obtained;
This is because if the amount exceeds 1 part by weight, it will be difficult to blend and the cured product will become too hard. In addition, a processing aid such as a low molecular weight polyorganosiloxane having a hydroxyl group or an alkoxy group at the terminal may be added to the composition of the present invention. According to the present invention, it has become possible to industrially produce a cured silicone material containing fine powder of transition metals such as silver and tungsten. That is, the composition of the present invention is stable even when stored for a long time, and can be cured by heating for a short time to obtain a cured silicone product containing a resinous or rubbery transition metal fine powder. The composition of the present invention includes conductive silicone rubber, silicone rubber, silicone resin, X-ray shielding plate,
It can be used as a contrast catheter or other contrast material. Hereinafter, the present invention will be explained with reference to Examples. In the examples, all parts represent parts by weight. Also,
For simplicity, the following abbreviations are used: Et: ethyl group Bu: butyl group Ph: phenyl group acac: acetylacetonate Example 1 The terminal is blocked with a trimethylsilyl group, and the average degree of polymerization is 7000, consisting of 0.2 mol% methylvinylsiloxy units and 99.8 mol% dimethylsiloxane units.
A base compound was obtained by kneading 100 parts of polyorganosiloxane, 50 parts of fumed silica whose surface was treated with siloxane, and 15 parts of fine tungsten powder having an average particle size of 2 microns using a dough mixer. 100 parts of this base compound, terminal-capped with trimethylsiloxy units, consisting of 90 mol% methylhydrogensiloxy units and 40 mol% dimethylsiloxy units, has a viscosity at 25°C.
One part of 30 cSt polymethylhydrogensiloxy was roll blended to prepare a sample. Compositions 11 to 20 were prepared by adding the catalyst systems shown in Table 1 to this,
The following experiment was conducted. However, compositions 11, 12, 15 and 16 are comparative examples that do not contain organic peroxides, of which compositions 11 and 15 contain the platinum complex immediately after synthesis, and compositions 12 and 16 contain the same platinum complex at 50°C. It was used as a catalyst system after being left for one or two months. Changes in the state during blending with a roll were observed. For the plasticized material that was masticated with a roll, T ₉₀ torque was measured at a temperature of 170° C. using a JSR model Kyulastometer (trade name, manufactured by Imanaka Kikai Kogyo Co., Ltd.). After blending, the mixture was left at room temperature and changes in state were observed. After blending, the mixture was left at 50°C, and T ₉₀ and torque were measured in the same manner as above. Press vulcanization was performed at a temperature of 170°C for 10 minutes. Hot air vulcanization was performed at a temperature of 250°C for 5 minutes. The physical properties of the press-cured materials were measured. (Only for compositions according to the present invention) The results of the experiments are shown in Table 2, and the results of the experiments are shown in Table 3.

【table】

【table】

【table】

[Table] From the above results, compositions 13, 14 and
In Nos. 17 to 20, the state of the catalyst system after mixing was normal, the curing property was good, and rubber elastic bodies were obtained. On the other hand, in the compositions of comparative examples, when platinum complexes immediately after synthesis (11 and 15) were used, there was almost no difference from the compositions of the present invention, but when the platinum complexes were left at 50°C for one or two months, In cases (12 and 16), 3 to 4
It gelled over time and also gelled in the extruder during the extrusion operation.

[Table] Example 2 The end is blocked with dimethylvinylsiloxy group,
0.05 mol% dimethylvinylsiloxy units and
100 parts of a polyorganosiloxane with an average degree of polymerization of 5000, consisting of 99.95 mol% dimethylsiloxy units;
40 parts of fumed silica whose surface was treated with hexamethyldisilazane, 15 parts of fine tungsten powder with an average particle size of 5 microns, and 3 parts of polydimethylsiloxane end-blocked with methoxy groups and having a viscosity of 30 cSt at a temperature of 25°C were added. A base compound was obtained by kneading with a mixer. To this base compound, 1.2 parts of poly(methylhydrodiene siloxane) end-capped with dimethylhydrodiene siloxy groups and having a viscosity of 15 cSt at 25°C and the catalyst shown in Table 4 are roll mixed to form a composition. was prepared. However, the platinum complex used was freshly synthesized. These compositions were left at a temperature of 50°C for one day and then extruded into a tube shape with an outer diameter of 8 mm and an inner diameter of 6 mm using an extruder and hot air vulcanized at a temperature of 250°C. As shown in Table 4, A good silicone tube was obtained.

[Table] Example 3 A base compound was obtained in the same manner as in Example 2, except that 60 parts of fine silver powder with an average particle size of 10 microns was used instead of fine Tandasten powder. To this base compound, 1.5 parts of the polymethylhydrodiene siloxane used in Example 1 was added and kneaded, and then Pt[P(OPh) ₃ ] ₄ and 50 times the amount of 2,5-dimethyl-(2, 70 by pre-mixing 5-di-t-butylperoxy)hexyne-3.
A composition was obtained by blending 250 ppm with the catalyst and polyorganosiloxane, which were reacted at ℃ for 6 hours and stored at room temperature for 1 month, using a roll. After this composition was left at a temperature of 50° C. for 3 days, it was extruded and hot-air vulcanized in the same manner as in Example 2, and a good silicone rubber tube was obtained. Also, at a temperature of 170℃
The silicone rubber obtained by press vulcanization for 10 minutes and then auto-vulcanization at 200° C. for 4 hours had a volume resistivity of 2×10 ⁻³ Ω·cm. Example 4 100 parts of polydimethylsiloxane whose ends are capped with dimethylvinylsiloxy units and has a viscosity of 2000 cSt at 25°C, 10 parts of fumed silica whose surface has been treated with siloxane, 100 parts of quartz fine powder, and then 2 micron average particle size. 20 parts of fine tungsten powder was added and kneaded using a universal kneader to obtain a base compound. This base compound contains 60 mol% dimethylhydrodiene siloxane units, 30 mol%
Compositions 41-44 were prepared by blending 3.5 parts of SiO ₂ units and 100 silicon average methylhydrodiene siloxane consisting of 10 mole percent dimethylsiloxy units, and the catalyst shown in Table 5. However, compositions 41 and 42 are comparative compositions. The gelation times of these compositions at 25°C were measured and are shown in Table 5.

[Table] After this gelation test, compositions 43 and 44 showed 150
When heated for 10 minutes in a dryer at ℃, it was cured and a good silicone rubber was obtained. Example 5 A polyorganosiloxane with an average degree of polymerization of 6000, which is terminally closed with a hydroxyl group and consists of 0.2 mol% methylvinylsiloxy units, 3 mol% diphenylsiloxy units, and the remaining dimethylsiloxy units, was used. A base compound was obtained in the same manner as in Example 2, except for the following. In this base compound, the terminal is capped with a trimethylsilyl group and consists of 60 mol% methylhydrodiene siloxane units and the remainder dimethylsiloxy units.
0.8 parts of polymethylhydrodienesiloxane with a viscosity of 10 cSt at 25°C, 20 ppm of fresh [(PhO) ₃ P] ₄ Pt and 200 ppm of 2,5-dimethyl-2,5-di( t
-butylperoxy)hexyne-3 was added and gelation at room temperature was measured, and gelation did not occur even after one month. After that, T ₉₀ and torque at 170℃ were measured using a JSR type Curlastometer (trade name of Imanaka Kikai Kogyo Co., Ltd.), and it was found that T _{90 was} 1 minute 30.
Second, the torque value was 43.2Kg・cm. In addition, it is extruded into a tube shape with an outer diameter of 20 mm and an inner diameter of 14 mm using an extruder.
When hot air vulcanization was performed at 350°C for 1 minute, a good silicone rubber tube was obtained. In addition, this platinum complex and organic peroxide may be mixed in advance.
When a silicone rubber tube that had been left for a month was used, a good silicone rubber tube was obtained in the same manner.

Claims (1)

[Scope of Claims] 1 (A) 100 parts by weight of a polyorganosiloxane in which at least two vinyl groups bonded to silicon atoms exist in one molecule; (B) an average of hydrogen atoms bonded to silicon atoms in one molecule; 0.1 to 10 parts by weight of polyorganohydrodiene siloxane present in a number exceeding 2, (C) 5 to 500 parts by weight of transition metal fine powder, and (D) (1) (a) Platinum containing no halogen atoms in the molecule A catalyst system and amount of catalyst selected from the group consisting of a complex, (b) an organic peroxide in which no hydroperoxy bond is present in the molecule, and (2) a reaction product of (a) and (b). A curable composition comprising: 2. The composition according to claim 1, which provides a rubber-like elastic body when cured. 3. The organic group bonded to the silicon atom of the polyorganosiloxane (A) consists of a methyl group and a vinyl group.
A composition according to claim 1. 4. The composition according to claim 1, wherein an average of 0.005 to 0.5% of the organic groups bonded to the silicon atoms of the polyorganosiloxane (A) is a vinyl group. 5 The average degree of polymerization of the polyorganosiloxane (A) is
10. A composition according to claim 1, which has a molecular weight ranging from 100 to 10,000. 6. The composition according to claim 1, wherein the terminals of the polyorganosiloxane (A) are capped with dimethylvinylsiloxy groups. 7. The composition according to claim 1, wherein the transition metal powder (C) is a tungsten powder. 8. The composition according to claim 1, wherein the transition metal powder (C) is a silver powder. 9. The composition according to claim 1, wherein the amount of the platinum complex (A) added is 0.1 to 1000 ppm based on the polyorganosiloxane (A). 10 The platinum complex of (a) is represented by the general formula Pt[PR ₃ ] ₄ (wherein R represents a monovalent group selected from the group consisting of a monovalent hydrocarbon group, an alkoxy group, and an aryloxy group). The composition according to claim 1, which is a (0)valent platinum-phosphorus complex. 11 The platinum complex in (a) is Pt(acac) ₂ (however, acac
2. The composition according to claim 1, which is a platinum-acetylacetonate complex represented by: acetylacetonate. 12. The composition according to claim 1, wherein (b) is 2 to 1000 equivalents of (a). 13. The composition according to claim 1 contains 10
A composition according to claim 1, comprising the addition of ~100 parts by weight of finely powdered silica. 14. The composition according to claim 13, wherein the surface of the finely powdered silica is treated with an organosilicon compound selected from the group consisting of polyorganosiloxane and hexamethyldisilazane.