JPS6352060B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD OF THE INVENTION The present invention relates to polyorganosiloxane compositions with improved heat resistance. More particularly, the present invention relates to polyorganosiloxane compositions containing iron sesquioxide and ground quartz, fused quartz, or mixtures thereof, which are curable by an addition reaction, and which have improved resistance to long-term use at elevated temperatures. [Technical background of the invention and problems thereof] A vinyl group-containing polyorganosiloxane in which two or more vinyl groups bonded to a silicon atom are present in one molecule in the presence of platinum or a platinum compound, and a polyorganohydrodiene siloxane. It is known to obtain cured silicone rubber by reacting . In addition, the obtained silicone rubber has a
It is also recognized to have excellent resistance to heat, and has been used for many purposes. In order to further increase the heat resistance of the rubber-like cured product of this polyorganosiloxane composition,
A method of adding a heat stabilizer to a composition has been proposed as shown below. For example, a method of adding iron oxide (US Pat. No. 3,352,781), a method of adding lanthanum-based rare earth metal oxides and hydroxides (Japanese Patent Publication No. 36-6189), a method of adding allyl urethane ( (Japanese Patent Publication No. 38-16771), the method of adding polyethynylpyridine (Japanese Patent Publication No. 16771-1983),
15047), and there are also proposals regarding the manufacturing method of metal oxides to be added (Tokuko Sho
47-47238). These improve the heat resistance of polyorganosiloxane compositions, but when used at high temperatures of 300° C. for long periods of time, thermal deterioration is significant and they cannot be used in such applications.
As an effective method here, a method of blending iron sesquioxide into polyorganosiloxane to improve resistance to thermal deterioration is known, but detailed studies regarding this have not been sufficiently conducted. In a system containing only iron sesquioxide, the mechanical properties of the rubber after curing are weak and cannot withstand use as a rubber. Therefore, fine powdered silica is generally used as a reinforcing agent. The present inventor found that when fumed silica or precipitated silica is added, the mechanical properties of the rubber after curing can be obtained, but the resistance to heat aging is significantly reduced, and long-term continuous use at high temperatures of 300 ° C. I found that I couldn't stand it. [Object of the Invention] Furthermore, the present inventor has found that by blending iron sesquioxide and a reinforcing inorganic filler such as crushed quartz, fused quartz, or a mixture thereof into a polyorganosiloxane composition, We discovered that it is possible to use it continuously for a long time,
The present invention has now been accomplished. That is, an object of the present invention is to provide a composition that yields a silicone rubber with higher heat resistance than conventional silicone rubber obtained by the reaction of a vinyl group-containing polyorganosiloxane and a polyorganohydrodiene siloxane. . [Summary of the Invention] That is, the present invention provides (A) at least two vinyl groups bonded to silicon atoms in one molecule, and an average number of siloxane units.
50 or more vinyl group-containing polyorganosiloxane 100 parts by weight (B) Polyorganohydrodiene siloxane with an average of more than 2 hydrogen atoms bonded to silicon atoms per molecule (A) Vinyl group bonded to silicon atoms 1 and (C) a catalytic amount of platinum or a platinum compound, further comprising: (D) ground quartz, fused Quartz, or mixtures thereof 10
~200 parts by weight, and (E) 20 to 300 parts by weight of iron sesquioxide, and the amount of (E) is not less than the amount of (D). It is. Component (A) used in the present invention is a base polymer of addition reaction type liquid silicone rubber, and at least two vinyl groups bonded to silicon atoms are present in one molecule in order to form a network structure by addition reaction. Must. Other organic groups bonded to silicon atoms include alkyl groups such as methyl, ethyl, propyl, butyl, amyl, hexyl, octyl, decyl, and dodecyl; aryl such as phenyl; group; aralkyl group such as benzyl group, β-phenylethyl group, β-phenylpropyl group; chloromethyl group, chlorophenyl group, β-cyanoethyl group, 3,3,
Substituted hydrocarbon groups such as 3-trifluoropropyl group are examples, but methyl group is the most preferred because of ease of synthesis and balance of heat resistance, mechanical properties, and fluidity of the composition before curing. Preferably, and especially when cold resistance or radiation resistance is required, it is preferable to use a phenyl group in combination. The siloxane skeleton may be linear or branched, and the siloxane unit containing a vinyl group may be at the end or middle of the molecular chain. Regarding the degree of polymerization, in order to obtain a rubber-like elastic body after curing, it is necessary that the number of siloxane units is 50 or more on average. The polyorganohydrodiene siloxane of component (B) acts as a crosslinking agent for component (A), and in order for the composition to form a network structure, the hydrogen atoms bonded to silicon atoms must be on average per molecule. There must be more than two. Examples of the organic group bonded to the silicon atom include those exemplified in component (A), and a methyl group is preferred for the same reason as component (A). Although the degree of polymerization is not particularly limited, it is difficult to synthesize one in which two or more hydrogen atoms are bonded to the same silicon atom, and in this sense it is preferable to have three or more siloxane units. The siloxane skeleton may be linear, cyclic, or branched. The blending amount of component (B) is such that the number of hydrogen atoms bonded to silicon atoms in component (B) is 0.5 to 10 per vinyl group bonded to silicon atom in component (A), preferably 0.5 to 10.
The amount ranges from 1.5 to 5. If it is less than 0.5, there will be insufficient crosslinking agent, resulting in poor curing, and if it exceeds 10, there will be a problem that the rubber will foam. Component (C) is a curing catalyst for providing a rubber-like elastic body through the addition reaction of components (A) and (B),
Examples include platinum black, platinum black supported on a carrier, platinum tetrachloride, chloroplatinic acid and its alkali metal salts, alcohol modified products of chloroplatinic acid, platinum-olefin complexes, and platinum-vinylsiloxane complexes. Among these, platinum complexes are preferred because curing progresses with a small amount of use and excellent heat resistance can be obtained. There are no particular restrictions on the amount of component (C), but
This is the amount that causes an addition reaction between components (A) and (B), and 1 to 100 ppm of platinum atoms is sufficient based on the total amount of components (A) and (B). Component (D) is crushed quartz, fused quartz, or a mixture thereof, which provides mechanical strength to the silicone rubber obtained by curing, and when used together with component (E) iron sesquioxide, improves heat resistance. It is something that contributes. Even with silica-based fillers, fumed silica,
Precipitated silica with a large specific surface area and diatomaceous earth provide silicone rubber with inferior heat resistance compared to the above-mentioned quartzes listed as component (D). The blending amount of component (D) in the present invention is 10 to 200 parts by weight, preferably 10 to 100 parts by weight, per 100 parts by weight of component (A).
Parts by weight. If the amount is less than 10 parts by weight, the strength of the resulting silicone rubber will be extremely low and it will not be usable. If the amount exceeds 200 parts by weight, the resulting cured product will be too hard and lack elasticity, making it unusable. Iron sesquioxide as component (E) is so-called red iron oxide, which has been widely used in pigments and the like, and is generally in the form of a fine powder with a particle size of 50 μm or less. This iron sesquioxide imparts heat resistance to silicone rubber, and when used in combination with component (D), even better heat resistance is imparted. The blending amount of iron sesquioxide is 20 parts by weight per 100 parts by weight of component (A).
-300 parts by weight, preferably 40-200 parts by weight. If the amount is less than 20 parts by weight, sufficient heat resistance will not be obtained, and if it exceeds 300 parts by weight, the cured silicone rubber will lose its elasticity and cannot be used. In addition, the amount of component (E) must be not less than the amount of component (D), and in order to obtain excellent heat resistance, it is preferably 1.5 to 10 times the amount of component (D), and more preferably. is 2.5 to 6 times higher, depending on the hardness of the silicone rubber obtained by curing. If the amount of component (E) is less than the amount of component (D), sufficient heat resistance cannot be obtained. The composition according to the present invention becomes a silicone rubber elastic body at room temperature or by heating, but is generally cured by heating at 100 to 200°C for about 1 hour to 15 minutes. [Effects of the Invention] The silicone rubber elastic body obtained by the present invention can maintain its rubber elasticity even when used continuously for a long period of 5 days or more at a high temperature of 300°C. The present invention provides such a super heat-resistant silicone rubber elastic body, which is widely used in heat-resistant sealing materials and the like under high temperatures. [Examples of the Invention] The present invention will be described below with reference to Examples. In the examples, all parts represent parts by weight, and all characteristic values are values measured at 25°C. Example 1 50 parts of iron sesquioxide and 20 parts of crushed quartz were added to 100 parts of a linear polydimethylsiloxane whose ends were closed with vinyl dimethylsiloxy units and whose viscosity was 10,000 cp.
parts were mixed thoroughly. To this mixture, 0.99 parts of polymethylhydrodiene siloxane with a Si-H bond number of 0.01 per gram and 0.05 parts of a platinum-vinylsiloxane complex with a platinum content of 2% are added and mixed to form a uniform composition A. I got it. Example 2 A uniform composition B was obtained in the same manner as in Example 1, except that the same amount of fused quartz was used instead of crushed quartz. Comparative Example 1 A uniform composition C was obtained in the same manner as in Example 1, except that the same amount of fumed silica was used instead of crushed quartz. Comparative Example 2 A uniform composition D was obtained in the same manner as in Example 1, except that the same amount of surface-treated fumed silica was used instead of ground quartz. Comparative Example 3 A uniform composition E was obtained in the same manner as in Example 1, except that the same amount of precipitated silica was used instead of crushed quartz. Comparative Example 4 A uniform composition F was obtained in the same manner as in Example 1, except that the same amount of diatomaceous earth was used instead of crushed quartz. Example 3 A uniform composition G was obtained in the same manner as in Example 1, except that 10 parts of crushed quartz and 10 parts of fused quartz were used instead of 20 parts of crushed quartz. [Evaluation of heat resistance 1] Compositions A to G obtained from Examples 1 to 3 and Comparative Examples 1 to 4 were each poured into a 2 mm thick mold and heated at 150°C.
It was held in a heating drying oven for 30 minutes to harden it. After processing the obtained rubber sheet under the following two conditions,
Hardness, tensile strength, and elongation were determined using samples punched into JIS K6301 No. 2 dumbbells. The results are shown in Table 1. Condition 1: Leave at room temperature of 25℃ for 24 hours Condition 2: Leave at 300℃ for 168 hours, then leave at 25℃
Leave it for 24 hours at room temperature.

[Table] Note) - cannot be measured. From these results, the compositions according to Examples 1 to 3 maintain their performance as rubber elastic bodies even when heated at 300° C. for one week. The compositions according to Comparative Examples 1 to 3 cannot maintain rubber elasticity, and the composition according to Comparative Example 4 also shows a remarkable increase in hardness and decrease in elongation. [Evaluation of heat resistance 2] Regarding the composition A obtained in Example 1, a 2 mm thick rubber sheet was prepared by the method of evaluation 1 of heat resistance,
After processing under the following conditions 3 and 4, the hardness,
Tensile strength and elongation were determined. The results are shown in Table 2. In addition, the results of processing under conditions 1 and 2 performed in heat resistance evaluation 1 are also shown. Condition 3: After heating at 330℃ for 168 hours, 25℃
Condition 4: After being left at room temperature for 100 hours at 350°C, at 25°C
Leave it for 24 hours at room temperature.

[Table] From this result, the composition according to the present invention can be heated at 330℃,
It can be used for a long time even under severe heating conditions of 350℃. Example 4 60 parts of iron sesquioxide and crushed quartz were added to 100 parts of a linear polydimethylsiloxane with a viscosity of 3000 cp and closed at both ends with vinyl dimethylsiloxane units.
10 parts were thoroughly mixed and heated under reduced pressure. To this mixture, 0.15 parts of polymethylhydrodiene siloxane with a Si-H number of 0.01 per gram and 0.03 parts of a platinum-vinylsiloxane complex with a platinum content of 2% were added.
1 part and mixed to obtain a uniform composition H. [Evaluation of heat resistance 3] Regarding the composition H obtained in Example 4, a 2 mm thick rubber sheet was prepared by the method of evaluation 1 of heat resistance,
After processing under the following three conditions, hardness, tensile strength, and elongation were determined using samples punched into JIS K6301 No. 2 dumbbells. The results are shown in Table 3. Condition 1: Leave at room temperature at 25℃ for 24 hours Condition 2: Leave at room temperature at 300℃ for 168 hours, then leave at 25℃
Condition 5: After being left at room temperature for 720 hours at 300°C, at 25°C
Leave it for 24 hours at room temperature.

[Table] The results show that this composition maintains its performance as a rubber elastic body even after heating at 300°C for about one month. Example 5 176 parts of iron sesquioxide and crushed quartz were added to 100 parts of a linear polydimethylsiloxane with a viscosity of 3000 cp and closed at both ends with vinyl dimethylsiloxane units.
100 parts were mixed thoroughly. To this mixture were added 1.5 parts of polymethylhydrodiene siloxane having 0.01 Si--H groups per gram and 0.05 parts of platinum-vinylsiloxane complex having a platinum content of 2% to obtain Composition J. [Evaluation of Heat Resistance 4] Composition J obtained in Example 5 was poured into a 2 mm thick mold and held in a heating drying oven at 150° C. for 60 minutes to be cured. After processing the obtained rubber sheet under the following two conditions, hardness, tensile strength, and elongation were determined using a sample punched into a JIS K6301 No. 2 dumbbell. The results are shown in Table 4. Condition 1: Leave at room temperature of 25℃ for 24 hours Condition 2: Leave at 300℃ for 168 hours, then leave at 25℃
Leave it for 24 hours at room temperature.

[Table] Example 6 Compositions K, L, and M were obtained in the same manner as in Example 1, except that the amounts of crushed quartz and iron sesquioxide were changed as shown in Table 5. [Heat Resistance Evaluation 5] Compositions K, L, and M obtained in Example 6 were evaluated in the same manner as in Heat Resistance Evaluation 1. The results are shown in Table 5.

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Claims (1)

[Scope of Claims] 1 (A) 100 parts by weight of a vinyl group-containing polyorganosiloxane in which at least two vinyl groups bonded to silicon atoms exist in one molecule and the number of siloxane units is 50 or more on average (B) Silicon atoms The number of hydrogen atoms bonded to silicon atoms is 0.5 to 10 per vinyl group bonded to silicon atom of polyorganohydrodienesiloxane (A) in which the average number of hydrogen atoms bonded to exceeds 2 per molecule. and (C) a catalytic amount of platinum or a platinum compound, further comprising: (D) ground quartz, fused quartz, or a mixture thereof.
200 parts by weight, and (E) 20 to 300 parts by weight of iron sesquioxide, and the amount of (E) is not less than the amount of (D). 2. Claims in which the amount of (B) is equivalent to 1.5 to 5 hydrogen atoms bonded to silicon atoms per one vinyl group bonded to silicon atoms in (A) 2. The polyorganosiloxane composition according to item 1. 3. The polyorganosiloxane composition according to claim 1, wherein (C) is a platinum complex. 4. Claim 1 in which the content of (C) is 1 to 100 ppm as platinum atoms based on the total amount of (A) and (B).
The polyorganosiloxane composition described in . 5. The polyorganosiloxane composition according to claim 1, wherein the amount of (D) is 10 to 100 parts by weight per 100 parts by weight of (A). 6. The polyorganosiloxane composition according to claim 1, wherein the amount of (E) is 40 to 200 parts by weight per 100 parts by weight of (A). 7. The polyorganosiloxane composition according to claim 1, wherein the amount of (E) is 1.5 to 10 times the amount of (D).