JPS60173051A - Polyorganosiloxane composition - Google Patents

Abstract

PURPOSE:To provide the titled compsn. which can be continuously used at a temp. of as high as 300 deg.C over a long period of time and is suitable for use in the production of a heat-resisting sealing material, etc., by blending Fe2O3 and a quartz inorg. filler with a polyorganosiloxane compsn. CONSTITUTION:The titled compsn. is obtd. by incorporating 10-200pts.wt. crushed quartz, fused quartz or mixture thereof (A) and 20-200pts.wt. Fe2O3 (B) in a compsn. contg. 100pts.wt. vinyl group-contg. polyorganosiloxane (C) contg. at least two vinyl groups attached to the silicon atom and an average of at least 50 siloxane units per molecule, a polyorganohydrogensiloxane (D) contg. an average of more than two hydrogen atoms attached to the silicon atom corresponding to a quantity of 0.5-10 hydrogen atoms attached to the silicon atom per vinyl group attached to the silicon atom in component C and a catalytic quantity of platinum (compd.) in such a proportion that the quantity of component B is less than that of component A. The silicone rubber elastomer prepd. from the compsn. can retain its rubber elasticity even after it is continuously used at 300 deg.C for 5 days or longer, and hence, it is useful as a heat-resisting sealing material, etc.

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 its problems] In the presence of platinum or a platinum compound, a vinyl group bonded to a silicon atom forms H1! i! It is known that a cured silicone rubber can be obtained by reacting the vinyl group-containing polyorganosiloxane present above with a polyorganohydrodiene siloxane. The obtained silicone rubber is also recognized to have superior heat resistance compared to general organic synthetic rubber and natural rubber, 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 has been proposed in which a heat stabilizer is added to the composition as shown below. For example, the method of adding iron oxide (U.S. Pat. No. 335
No. 2781) method of adding oxides and hydroxides of lanthanum-based rare earth metals (Japanese Patent Publication No. 36-6189), method of adding allyl urethane (Japanese Patent Publication No. 38-198)
6771), a method of adding polyethynylpyridine (Japanese Patent Publication No. 49-1.5047), and a method for manufacturing the metal oxide to be added (Japanese Patent Publication No. 47-47238). . With these,
Although the heat resistance of the polyorganosiloxane compositions is improved, if they are used for a long time at a high temperature of 300° C., 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 systems containing only iron sesquioxide,
The mechanical properties of the rubber after curing are weak and it 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 it is difficult to use continuously for a long time at a high temperature of 300 ° C. I found that I couldn't stand it.

[Object of the invention] Furthermore, the present inventor has added to the polyorganosiloxane composition,
It was discovered that by blending iron sesquioxide and crushed quartz, fused quartz, or a mixture thereof as an inorganic filler serving as a reinforcing agent, continuous use for a long time at a high temperature of 300°C is possible, and the present invention is based on this discovery. It's arrived.

That is, an object of the present invention is to provide a composition that yields a silicone rubber with higher heat resistance than the 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) 100 parts by weight of a vinyl group-containing polyorganosiloxane having at least two vinyl groups bonded to a silicon atom in the molecule and having an average of 50 or more siloxane units. Polyorganohydrodiene siloxane with an average of more than two hydrogen atoms bonded to silicon atoms in one molecule
Contains (A) an amount corresponding to 0.5 to 10 hydrogen atoms bonded to a silicon atom per vinyl group bonded to a silicon atom, and (C) a catalytic amount of platinum or a platinum compound. Further, (D) crushed quartz, fused quartz, or a mixture thereof, 10 to 2
00 parts by weight, and (E) 20 to 300 parts by weight of iron sesquioxide, and the content of (E) is not less than the content of (D). be.

Component (A) used in the present invention is an addition reaction type liquid silicone rubber pace polymer, and in order to form a network structure by addition reaction, the vinyl group bonded to a silicon atom is present in one molecule at least 21 [1i1 Must exist. Other organic groups bonded to silicon atoms include:
Alkyl groups such as methyl group, ethyl group, propyl group, butyl group, amyl group, hexyl group, octyl group, decyl group, dodecyl group; Aryl group such as phenyl group; hensyl group, β-phenylethyl aralkyl groups such as β-phenylpropyl groups; substituted hydrocarbon groups such as chloromethyl groups, chlorophenyl groups, β-cyanoethyl groups, and 3,3.3-1-lifluoropropyl groups; Methyl groups are most preferred because of their ease of synthesis and the balance of heat resistance, mechanical properties, and fluidity of the composition before curing, and phenyl groups are particularly preferred when cold resistance or radiation resistance is required. It is preferable to use them together. 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). The degree of polymerization is not particularly limited, but it is difficult to synthesize one in which 2 (Ili) or more hydrogen atoms are bonded to the same silicon atom, and in that sense it is preferable to consist of 3 or more siloxane units.The siloxane skeleton is linear , may be circular 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. 1.
The amount ranges from 5 to 5 pieces. 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), and includes platinum black, platinum black held on a carrier, platinum tetrachloride, Examples include 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. The blending amount of component (C) is the amount that causes an addition reaction between component (A) and component (B),
1 to 100 ppm of platinum atoms is sufficient based on the total amount of components (A) and (B).

(D) component is crushed quartz, fused quartz or a mixture thereof;
It imparts mechanical strength to the silicone rubber obtained by curing, and also contributes to improving heat resistance by being used together with iron sesquioxide as component (E). . Among silica-based fillers, those with a large specific surface area such as fumed silica and precipitated silica, and diatomaceous earth, are silicone rubbers that have lower heat resistance than the aforementioned quartzes listed as component (D). give.

The blending amount of component (D) in the present invention is 100% of component (A).
10 to 200 parts by weight, preferably 10 to 200 parts by weight
It is 100 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 becomes too hard and has no elasticity, making it unusable.

Iron sesquioxide as component (E) is so-called hengara, which has been commonly 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 together with component (D), it imparts even more excellent heat resistance. The amount of iron sesquioxide is in the range of 20 to 300 parts by weight, preferably 40 to 200 parts by weight, per 100 parts by weight of component (A). If the amount is less than 20 parts by weight, sufficient heat resistance cannot be obtained, and if it exceeds 300 parts by weight, the cured silicone rubber loses its elasticity and cannot be used. In addition, it is necessary that the amount of component (E) is not less than the amount of component (D), and in order to obtain excellent heat resistance, it is preferably 1.5 to 1.5 of the amount of component (D).
1O times, more preferably 2.5 to 6 times 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 at 100-200°C for 1 hour or more.
Generally, it is cured by heating for 15 minutes.

[Effect of the invention] The silicone rubber elastic body obtained by the present invention has a
It can maintain its rubber elasticity even when used continuously for 5 days or more at high temperatures of °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 explained 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 Linear polydimethylsiloxane 1 closed at both ends with vinyldimethylsiloxy units and having a viscosity of 10,000 cP
00 parts, 50 parts of iron sesquioxide and 20 parts of crushed quartz were thoroughly mixed. This mixture has Si −
Is the number of 11 connections 0.0111? 0.99 part of the polymethylhydrodiene siloxane of a and 0.05 part of a platinum-vinylsiloxane complex having a platinum content of 2% were added and mixed to obtain a uniform composition A.

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 was obtained in the same manner as in Example 1, except that the same amount of surface-treated fumed silica was used in place of the crushed 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.

[Heat resistance evaluation 1] Compositions A-G obtained from Examples 1 to 3 and Comparative Examples 1 to 4
were poured into molds each having a thickness of two fins, and held in a heated drying oven at 150° C. for 30 minutes to harden. After processing the obtained rubber sheet under the following two conditions, the hardness, tensile strength,
It started to grow.

The results are shown in Table 1.

Condition 1: Left at room temperature of 25℃ for 24 hours Condition 2: 30
The compositions according to Examples 1 to 3 had a
It maintains its performance as a rubber elastic body even after being heated at ℃ 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 rubber sheet with a thickness of 2 mm was prepared by the method of evaluation 1 of heat resistance, and the following conditions 3 were prepared.
, 4, and then the hardness, tensile strength, and elongation were measured using samples punched into JIS K2SO3 No. 2 Danher. The results are shown in Table 2. The results of processing under condition 1.2 in heat resistance evaluation 1 are also shown.

Condition 3: After being left under heating at 330°C for 168 hours, 25
Condition 4: After being left at room temperature for 24 hours at 350°C for 100 hours,
The composition according to the present invention was left at room temperature of 330°C for 24 hours.
It can be used for a long time even under severe heating of 50°C.

Example 4 Linear polydimethylsiloxane 1 closed at both ends with vinyldimethylsiloxane units and having a viscosity of 3.000 cP
00 parts, 60 parts of iron sesquioxide and 10 parts of crushed quartz were sufficiently mixed, and the mixture was heated and treated under reduced pressure.

To this mixture, 0.15 parts of polymethylhydrogensiloxane containing 0.01 5i-H per 1 g;
0.0 platinum-vinylsiloxane complex with platinum content of 2%
Three parts were added and mixed to obtain a uniform composition H.

[Evaluation of heat resistance 3] Regarding composition H obtained in Example 4, evaluation of heat resistance 1
A rubber sheet with a thickness of 2 square meters was prepared using the method described above, and after being treated under the following three conditions, the hardness, tensile strength, and elongation were measured using samples punched into JIS K 6301 No. 2 dumbbells. The results are shown in Table 3.

Condition 1: Left at room temperature of 25℃ for 24 hours Condition 2: 30
After being left under heating at 0°C for 168 hours, left at room temperature at 25°C for 24 hours Condition 5: After being left under heating at 300°C for 720 hours, 25 hours
Table 3 The results show that the composition retains its performance as a rubber elastic body even after being heated at 300°C for about one month.

Example 5 Straight-chain polydimethylsiloxane 1 with both ends closed with vinyldimethylsiloxane units and a viscosity of 3,0OOcP
00 parts, 176 parts of iron sesquioxide and 100 parts of crushed quartz were thoroughly mixed. This mixture contains Si per part
Composition J was obtained by adding 1.5 parts of polymethylhydrodienesiloxane having 0.01 -if groups and 0.05 parts of platinum-vinylsiloxane complex having a platinum content of 2%.

[Evaluation of Heat Resistance 4] Composition J obtained in Example 5 was poured into a 2-inch thick mold and held in a heating drying oven at 150° C. for 60 minutes to be cured. The obtained rubber sheet was treated under the following two conditions, and then the hardness, tensile strength, and elongation were measured using samples punched into JIS K 6301 No. 2 dumbbells. The results are shown in Table 4.

Condition 1: Left at room temperature of 25℃ for 24 hours Condition 2: 30
After being left under heating at 0°C for 168 hours, left at room temperature at 25°C for 24 hours Table 4 Example 6 The amounts of crushed quartz and iron sesquioxide were changed as shown in Table 5. Compositions L and M were obtained using the same method as in Example 1.

[Heat Resistance Evaluation 5] The composition obtained in Example 6 was evaluated for L and M in the same manner as in Heat Resistance Evaluation 1. The results are shown in Table 5.

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 average number of siloxane units is 50 or more (B) silicon atoms Polyorganohydrodiene siloxane with an average of more than two hydrogen atoms bonded to one molecule
The number of hydrogen atoms bonded to silicon atoms is 0.5 to 1 for 1.111 J of vinyl groups bonded to silicon atoms in (A).
and (C) a catalytic amount of platinum or a platinum compound, further comprising (D> crushed quartz, fused quartz, or a mixture thereof 10 to 2
00 parts by weight, and (B) 20 to 300 parts by weight of iron sesquioxide, and the amount of (E) is not less than the amount of (D). 2. A patent in which the blending amount of (B) is equivalent to 1.5 to 5 hydrogen atoms bonded to silicon atoms per 1 vinyl group (flit) bonded to silicon atoms in (A). The polyorganosiloxane composition according to claim 1. 3 The polyolkalisiloxane composition according to claim 1, wherein (C) is a platinum complex. 4 The blending amount of (C) is equal to (A). The polyorganosiloxane composition according to claim 1, wherein the amount of platinum atoms is 1 to 100 ppm based on a total of 81 parts by weight of (B). te1
The polyorganosiloxane composition according to claim 1, which contains 0 to 100 parts by weight. 6 The blending amount of (E) is 4 per 100 parts by weight of (A)
The polyorganosiloxane composition according to claim 1, which contains 0 to 200 parts by weight. 7. The polyorganosiloxane composition according to claim 1, wherein the amount of (E) is 1.5 to 10 times the amount of (D).