JPS601894B2 - Flame retardant silicone rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a silicone rubber composition that has excellent flame retardancy and heat resistance, and does not adhere to metals.

The following methods have been proposed so far for imparting flame retardancy to heat-curable silicone rubber.

m Add rare earth metal oxide or hydroxide.

(Japanese Patent Publication No. 36-618y) [2' Add platinum and fumed titanium dioxide.

(Japanese Patent Publication No. 47-21826) {3} Add platinum and a rare metal oxide or hydroxide.

(Japanese Patent Publication No. 52-3671) 'Four Steps' Zinc carbonate and cerium oxide are added to so-called addition-type silicone rubber that is vulcanized with a platinum catalyst. (Tokuko Showa 53 Mountain 1350
5) (5} Titanium dioxide, carbon black,
Additives selected from the group consisting of Group 0 metal oxides, rare earth metal oxides (eg, cerium oxide), and rare metal hydroxides (eg, cerium hydroxide), platinum, and aromatic acids are added. (Unexamined Japanese Patent Publication No. 52-69464) {6}
Add platinum, carbon black, fumed titanium dioxide, and triazole compounds.

(Japanese Unexamined Patent Publication No. 52-15245) (7) Adding cerium hydroxide or cerium oxide to the addition type silicone rubber.

(Special Publication No. 53-11065) [8] Add platinum and cerium carbonate.

(Special Publication No. 53-11845) {9) Add platinum, basic zinc carbonate, and alkoxyvinylsilane.

(Japanese Unexamined Patent Publication No. 50-198961) On the other hand, when silicone rubber is brought into contact with metal and cured, it often adheres closely to the metal and becomes difficult to peel off.

For example, in the case of electric wires coated with silicone rubber, the core wire and the rubber stick together, making it difficult to peel off the rubber layer, which may cause problems during connection work. This core wire adhesion phenomenon is remarkable in annealed copper wire as a core wire and a metal wire obtained by plating this with tin or the like. A known method for preventing adhesion is to add fatty acid salts of metals such as zinc stearate and calcium stearate to silicone rubber (Japanese Patent Application Laid-open No. 124151/1983), but when this is used, the silicone rubber becomes flammable. This has the disadvantage that even if a component that imparts flame retardancy is added, no effect can be obtained, and the heat resistance of the silicone rubber decreases. In addition, the above-mentioned method for making chicks is of course intended only for making nada, and is not aimed at preventing core wire adhesion at all, and in fact, except for {4} and {9). There is no adhesion prevention effect. ■In the armpits, the core wires are more likely to stick together. '4- and [Although it has the effect of preventing core wire adhesion to the skin, in order to obtain sufficient flame retardancy with this method, a relatively large amount of basic zinc carbonate must be added as a base polymer, so the heat resistance is extremely low. It will drop. Other methods also have the problem that heat resistance decreases when the amount of each component is increased in order to obtain excellent flame retardancy. The present invention provides a silicone rubber composition that has excellent flame retardancy, heat resistance, and non-adhesion to metals. There are 1.98 to 2.002 organic groups per unit, 0.01 to 5 mol% of the total organic groups are Bjer groups, 50 mol% or more are methyl groups, and the remainder is one organic group that does not contain aliphatic unsaturation. 10 parts by weight of polyorganosiloxane having an average degree of polymerization of 1000 or more, {B} reinforcing silica 10 to 15
Parts by weight of [C} Compositional formula C8〇H) a
- Hydroxyl group-containing cerium compound expressed by mia≦4) 0
．． 05 to 5 parts by weight, blood Atomized titanium dioxide 0.1 to 5 parts by weight [E} Platinum or platinum compound, 2 to 200 ppm of platinum relative to wind components, 'F' average particle size 10r or less (
G) 0.1 to less than 5 parts by weight of basic zinc carbonate (excluding 0); and G) 0.1 to 5 parts by weight of an organic peroxide.

The polyorganosiloxane used in the present invention is generally linear, but may contain some branching. Examples of the organic group bonded to silicon include alkyl groups such as methyl group, ethyl group, and propyl group, phenyl group, and vinyl group, but 0.01 to 5 mol% of the total organic groups, preferably 0.03 ~0.5 mol% is pinyl group, 50
More than mol% is methyl group. If there are few vinyl groups, ■
If an organic peroxide other than penzoyl peroxide is used, the vulcanization will be insufficient, resulting in a lack of rubber properties, and if the amount is too large, the heat resistance will decrease. Moreover, if the methyl group content is less than 50 mol%, heat resistance will deteriorate. In order to obtain the best heat resistance and flame retardancy, it is preferable that all groups other than vinyl groups are methyl groups. The molecular terminal may be closed with any one of trimethylsilyl group, dimethylvinylsilyl group, alkoxy group, silanol group, etc. The amount of such silicon-bonded organic groups ranges from 1.98 to 2.002 per silicon atom.

If the amount is more than this, a satisfactory degree of polymerization cannot be obtained, and if it is less than this, a good rubber-like elastic body cannot be obtained. In addition, the average degree of polymerization of the polyorganosiloxane needs to be 1000 or more in order to obtain good mechanical properties, and considering the workability of the process of obtaining a homogeneous composition by kneading, it is 3000 to ZIOOOO. It is preferable that there be. [
The reinforcing silica (B) is a component for imparting strength to silicone rubber, and may be commonly used silica such as fumed silica, green method silica, dry method pulverized silica, and silica sol.

The blending amount is 10 to 15 parts by weight, preferably 20 to 8 parts by weight, per 10 parts by weight of the harmful component. If it is less than 1 part by weight, there will be no reinforcing effect, and if it exceeds 15 parts by weight, workability will deteriorate.

Such reinforcing silica may be used as is, but in order to improve the processability of the composition and to impart good electrical properties to the silicone rubber obtained by curing, the surface is coated with polydimethylsiloxane/octamethylcyclo. It is preferable to use one treated with an organosilicon compound such as tetracyclosane or hexamethyldisilazane. The cerium compound 'C) is a component that imparts flame retardancy and heat resistance to the composition.
In particular, excellent effects are exhibited by the synergistic action with ■} to {F}.

Its composition is the formula Ce(○H〉a○41a(0.1≦aS4
), but the closer a is to 4, that is, the closer to pure cerium hydroxide, the greater the effect.

The blending amount is 0.05 to 5 parts by weight, preferably 0.1 to 2 parts by weight, based on the weight of component 10. This is because if the amount is less than 0.05 parts by weight, flame retardancy and heat resistance will not be obtained, and if it exceeds 5 parts by weight, the heat resistance will deteriorate.

The atomized titanium dioxide of 'D} also contributes to improving flame retardancy and heat resistance, and the blending amount is 0.1 to 5 parts by weight, preferably 0.5 to 5 parts by weight, per 10 parts by weight of wind component. 5 parts by weight.

If it is less than 0.1 part by weight, there will be no effect, and if it is more than 5 parts by weight, the heat resistance will deteriorate.

The platinum or platinum compound in the legs imparts flame retardancy to the composition, and can be produced from simple platinum, platinum adsorbed onto a holding carrier, chloroplatinic acid, platinum-olefin body, white body and alcohol. Examples include platinum coordination compounds such as a collar body obtained from platinum and vinyl siloxane, a chain body obtained from platinum and vinyl siloxane, and a divalent platinum-phosphorus chain body.

The amount of platinum to be blended is 2 to 20 pm, preferably 5 to 10 pm, relative to component (1). If the amount is less than 20 pm, the flame retardancy is insufficient, and if it is more than 20 pm, it is not only disadvantageous in terms of cost, but also reduces heat resistance. 'F
) The basic zinc carbonate improves the flame retardancy of the composition and acts as a component that prevents adhesion to metals.

The chemical composition is ZnC03・father n(〇H)2. Day 20,
ZnC〇3. Gen n(〇H)2. It is represented by the Fukata compositional formula such as day 20. The average particle size must be 10r or less (excluding zero). This is because if the particle size is large, the mechanical properties of the rubber will be impaired and the flame retardance will be reduced. The compounding amount is
(2) The amount is 0.1 parts by weight or more and less than 5 parts by weight, preferably 0.1 to 2 parts by weight, per 100 parts by weight of component. If it is less than 0.1 parts by weight, flame retardancy and sufficient non-adhesion to metals cannot be obtained, and if it is more than 5 parts by weight, heat resistance and electrical properties will deteriorate. The organic peroxide in G) may be one used for the vulcanization of ordinary heat-curable silicone rubber, such as penzoyl peroxide, 2,4-dichloropenzoyl peroxide,
Dicumyl peroxide, 2,5-bis(t-butylberoxy)-2,5-dimethylhexane, 2,5-bis(t-butylberoxy)
-butylberoxy)-12,5-dimethylhexyne, di-t-butyl peroxide, and the like.

The amount added is 0.1 to 5 parts by weight, preferably 0.3 to 2 parts by weight, per 10 parts by weight of the wind component. This is because if it is too small, vulcanization becomes difficult, and if it is too large, heat resistance deteriorates. When a process of continuously coating with a silicone rubber composition and vulcanizing it in high temperature air for a short time without going through press vulcanization is used, such as coating electric wires, 2. Penzoyl 4-dichloroperoxide is suitable. In the composition of the present invention, in addition to the above-mentioned components, crushed quartz, diatomaceous earth, clay, talc, etc. may be used in combination as semi-reinforcing or non-reinforcing fillers.

Furthermore, iron oxide, ferrite, organic acid dilute metal salt, etc. may be used as a heat resistance improver, and a low molecular weight organosiloxane or silane having an alkoxy group or hydroxyl group at the terminal may be added. According to the present invention, a silicone rubber composition has been obtained which has a metal adhesion prevention effect equivalent to that of the prior art '4' and (2) mentioned above, and which is also excellent in flame retardancy and heat resistance.

The composition of the present invention is mainly used for covering electric wires that require flame retardancy and heat resistance, but it is also widely used for molded products such as tubes, and for insulating electrical parts that require flame retardancy. Among these, it is also suitable for applications that require easy peeling from the metal base due to workmanship.

Examples of the present invention will be shown below.

In the examples, all parts indicate parts by weight.
Example Z Surface treatment with 10 anchors of polyorganosiloxane and 2 polydimethylsiloxanes with a degree of polymerization of 5000, with one end closed with a trimethylsilyl group, containing 0.2 mol% of methylvinylsiloxy units, and the remainder being dimethylsiloxy groups. fumed silica 40 with an average particle size of 16 mm
Table 1 shows the hydroxyl group-containing cerium compound, atomized titanium dioxide, chloroplatinic acid, basic zinc carbonate, and organic peroxide of the formula CekuOH)a○oa (o.・mia≦4) Silicone rubber compositions were prepared by adding the amounts shown.

The amount of platinum in the table is based on the base polymer. These compositions were continuously coated on a core wire made of 7 tin-plated copper wires with a diameter of 0.26 ribs using an extruder so that the outer diameter was 5 and 2 strands, and heated at 450°C with sand heating at 3°C. It was vulcanized to make electric wires. Regarding these electric wires, flame retardant, core wire adhesion,
and heat resistance tests were conducted in the following manner. Second result
Shown in the table. Flame retardancy: Conduct a combustion test according to UL758, ignite five samples each five times, and record the maximum number of seconds of combustion.

However, if more than 6 seconds have elapsed since ignition and the fire does not show any tendency to extinguish, record the time of 60 seconds or more. Core wire adhesion; 150
The silicone rubber layer was peeled off after heating at 0.00°C for 6 hours.

Heat resistance: Remove the core wire from the wire and measure the physical properties of the silicone rubber.

The rate of change is determined by measuring under normal conditions and after heating at 250° C. for 7 days. Table 1 Table 2 Example 2 A composition was prepared by adding 100 parts of the same polyorganosiloxane as in Example 1 and 4 parts of fumed silica, and each component shown in Table 3 was added*, and the same test was conducted. Ta.

The results are shown in Table 4. Table 3 (Note) *Average particle size 5 Table 4 Example 3 The terminal is closed with a dimethylvinylsilyl group and contains 0.1 mol% of methylvinylsiloxy units, with the remainder being dimethylsiloxy units.Degree of polymerization: 7000 10 parts of polyorganosiloxane, 4 parts of fumed silica with a particle size of 16 mr,
1 part of hydroxyl group-containing cerium compound, 3 parts of fumed titanium dioxide
1 part, 30 ppm platinum based on the base polymer of the platinum compound obtained from tetramethyltetravinylcyclotetrasiloxane and chloroplatinic acid, 1 part of basic zinc carbonate with a particle size of 5 mm, and 0 parts of 2,4-dichloroperoxide penzoyl. .7
Composition 4 was prepared by mixing the following parts.

Table 5 shows the results of a test similar to Example 1 using this product. Example 4 Instead of the polyorganosiloxane used in Example 1, the terminal was closed with a trimethylsilyl group, and 0.2 mol% of methylvinylsiloxy units and 5% of diphenylsiloxy units were used.
Composition 5 was prepared using the same composition as Composition 1, except that the remainder was composed of dimethylsiloxy units and had a degree of polymerization of 5000.

Table 5 shows the results of a test similar to Example 1 using this product. Table 5 Example 5 Using the polyorganosiloxane and fumed silica used in Example 1, two compositions were prepared with the ingredients shown in Table 6.

The test results are shown in Table 7. 6th Table 7

Claims (1)

[Scope of Claims] 1 (A) There are 1.98 to 2.002 organic groups bonded to silicon atoms per silicon atom, and 0.01 to 5 mol% of the total organic groups are vinyl. 100 parts by weight of a polyorganosiloxane with an average degree of polymerization of 1000 or more, in which 50 mol% or more of the group is a methyl group and the remainder is a monovalent organic group containing no aliphatic unsaturation, (B) reinforcing silica 10 to 15
0 parts by weight, (C) 0.05 to 5 parts by weight of a hydroxyl group-containing cerium compound represented by the compositional formula ▲ Numerical formula, chemical formula, table, etc. ▼, (D) 0.1 to 5 parts by weight of fumed titanium dioxide,
(E) Platinum or a platinum compound, 200 ppm of platinum based on component (A), (F) 0.1 part by weight or more of basic zinc carbonate with an average particle size of 10 μ or less (excluding 0), 5
and (G) 0.1 to 5 parts by weight of an organic peroxide. 2. The composition according to claim 1, wherein (A) has an average degree of polymerization of 3,000 to 10,000. 3 The organic group bonded to the silicon atom in (A) is 0.03 to
A composition according to claim 1, comprising 0.5 mole % vinyl groups and the remainder methyl groups. 4. The composition according to claim 1, wherein (B) is reinforcing silica whose surface has been treated with an organosilicon compound. 5. The composition of claim 1, wherein (C) is 0.1 to 2 parts by weight. 6. The composition of claim 1, wherein (D) is 0.5 to 5 parts by weight. 7. The composition of claim 1, wherein (F) is 0.1 to 2 parts by weight. 8. The composition of claim 1, wherein (G) is 2,4-dichlorobenzoyl peroxide.