JPS6261614B2 - - Google Patents

Description

[Detailed description of the invention]

SILICONE RUBBER COMPOSITIONS FIELD OF THE INVENTION This invention relates to silicone rubber compositions with improved flame retardancy. Although silicone elastomers have various excellent properties, they have the disadvantage of being flammable, and various methods of making them flame retardant have been proposed. For example, as a typical example, a silicone rubber compound mixed with a platinum-containing material (Japanese Patent Publication No. 2591/1983) is known.
However, since platinum-containing materials alone do not have sufficient self-extinguishing properties, many studies have been conducted to improve self-extinguishing properties by combining platinum-containing materials with other compounds. For example, a silicone rubber compound mixed with a platinum compound and hume titanium dioxide (Tokuko Showa)
47-21826), a silicone rubber compound mixed with a platinum compound and finely powdered manganese carbonate (Special Publication No. _51-23979 ), a silicone rubber compound mixed with a platinum compound and ( _Feo ) , in which the ratio of x and y is 0.05 to 1.0) (Japanese Patent Publication No. 51-35501) is known. However, these known products do not exhibit sufficiently satisfactory self-extinguishing properties, and those containing the platinum compound and humid titanium dioxide deteriorate the electrical properties of the silicone elastomer due to moisture. When an acyl organic peroxide was used as a vulcanizing agent, vulcanization was _inhibited and the product was not _vulcanized sufficiently. However, unless the amount of (FeO)x(Fe ₂ O ₃ )y added is increased, the self-extinguishing effect will be weak, and if the amount added is increased, the mechanical properties of the silicone elastomer will deteriorate. The present invention aims to provide a flame-retardant silicone rubber composition which improves these conventional drawbacks and provides molded articles with excellent mechanical strength and heat resistance. That is, the present invention provides (A) 100 parts by weight of an organopolysiloxane represented by the average unit formula RaSiO4-a/2 (wherein R is a substituted or unsubstituted monovalent hydrocarbon group, a=1.95 to 2.05) (B ) Fine powder silica filler 10-150 parts by weight (C) 2-200 ppm of platinum based on component (1) or a platinum compound containing the same amount of platinum (D) Titanium dioxide 0.5-20 parts by weight (E) Carbon atoms The present invention relates to a flame-retardant silicone rubber composition comprising 0.05 to 3 parts by weight (F) of several dozen or more fatty acids and/or metal salts of fatty acids, and 0.1 to 5 parts by weight of an organic peroxide. The organopolysiloxane as component (A) used in the present invention has an average unit formula of RaSiO4-a/2 (R is a methyl group, an ethyl group, a propyl group, a phenyl group and their halogen-substituted hydrocarbon groups, a vinyl group, It is a mainly linear diorganopolysiloxane represented by a substituted or unsubstituted monovalent hydrocarbon group selected from an allyl group (a=1.95 to 2.05).
Specific examples of units constituting the diorganopolysiloxane include dimethylsiloxane, methylphenylsiloxane, diphenylsiloxane, methylvinylsiloxane, and phenylvinylsiloxane. The diorganopolysiloxane preferably has a high molecular weight and is called silicone raw rubber, but it is not limited to this and may be in a liquid state at room temperature. Component (A) is a homopolymer, a copolymer, or a mixture of these polymers. In addition, a small amount of RsiO _1.5 (R is the same _as above) units may be contained in these structures, and the molecular chain terminal is a hydroxy group, an alkoxy group, a trimethylsilyl group, a dimethylvinylsilyl group, or a methyldiphenyl group. Examples include a silyl group, a methylphenylvinylsilyl group, and the like are not particularly limited. The fine powder silica filler as component (B) used in the present invention may be those conventionally used in silicone elastomers, and examples include fumed silica, precipitated silica, fine quartz powder, and diatomaceous earth. Ru. These are preferably in the form of fine powder with a particle size of 50 microns or less and a specific surface area of 100 m ² /g or more, and are either untreated or pre-surfaced with an organosilicon compound such as organosilane, organosiloxane, or organosilazane. Any processed material may be used. If the amount of component (B) is too high or low, the mechanical properties of the silicone elastomer obtained by vulcanization will deteriorate. do. The component (C) used in the present invention is 2 times the component (A).
It is a platinum-based compound containing ~200 ppm, preferably 5-100 ppm of platinum, or the same amount of platinum, and is an essential component that imparts flame retardancy to silicone elastomers. Platinum includes fine platinum powder or platinum powder supported on a carrier such as alumina, silica gel, asbestos, etc. Platinum compounds include chloroplatinic acid, or complexes of chloroplatinic acid and alcohol, ether, aldehyde, vinyl siloxane, etc. is exemplified. It is important to uniformly disperse these platinum or platinum-based compounds in a silicone rubber composition in order to impart flame retardancy to the silicone elastomer obtained by vulcanizing it, and for this purpose, isopropyl alcohol, ethanol,
Organic solvents such as benzene, toluene, xylene,
Alternatively, it may be used after being dissolved or dispersed in organopolysiloxane oil. Titanium dioxide as component (D) used in the present invention is an important component that imparts self-extinguishing properties to silicone elastomers through a synergistic effect with component (C) described above and component (E) described below. . This titanium dioxide may be one that has been conventionally used as a pigment or a heat-resistant agent, but in particular, the average particle size produced industrially by fuming hydrolysis of titanium tetrachloride is
The use of fumed titanium dioxide of 0.1 micron or less is preferred. Titanium dioxide as component (D) may be treated with an organosilane, an organosiloxane, an organosilazane or an organic compound. The amount of titanium dioxide blended is in the range of 0.5 to 20 parts by weight per 100 parts by weight of component (A). If it is less than 0.5 parts, the self-extinguishing effect will be weak, and if it is more than 20 parts by weight, the silicone rubber composition will Since processability and various physical properties of the silicone elastomer obtained by vulcanization are deteriorated, it is preferable to add 1 to 10 parts by weight. Number of carbon atoms as component (E) used in the present invention
10 or more fatty acids and/or metal salts of fatty acids have a synergistic effect with the above-mentioned components (D) and (D),
This is a component that further improves the flame retardancy of silicone rubber. The number of carbon atoms of 10 or more refers to the number of carbon atoms in the hydrocarbon portion (including 10 atoms), and does not include carbon atoms in carboxylic acid. As for the hydrocarbon portion, not only normal ones but also those having isomers, substituents and unsaturated groups can be used. Further, the carboxylic acid portion may be a monovalent carboxylic acid or a polyvalent carboxylic acid. Specific examples of fatty acids include undecylenic acid, lauric acid, tridecylenic acid, myristic acid, pentadecylenic acid, palmitic acid,
margaric acid, stearic acid, nonadecylenic acid,
Monovalent carboxylic acids such as aragic acid, heneicosanoic acid, behenic acid, tricosanoic acid, lignoceric acid, cerotic acid, montanic acid, melisic acid, dodecanedioic acid, heptadecanedioic acid, icosanoic acid,
Trichosandioic acid, triacontandioic acid, HOOC
(CH ₂ ) ₁₀ CH (COOH) ₂ , HOOC (CH ₂ ) ₂ CH
Examples include polyhydric carboxylic acids such as (COOH)(CH ₂ ) ₁₂ COOH. Metal salts of fatty acids are those in which the hydrogen atoms of the carboxylic acids of the fatty acids mentioned above are substituted with metal atoms, and are called metal soaps.These metals include magnesium, calcium, aluminum, lithium, barium, and strontium. , zinc, cadmium, lead, etc., but are not particularly limited. However, it is better to use commercially available products due to their simplicity. Commercially available metal soaps include magnesium stearate, aluminum stearate, calcium stearate, lithium stearate, zinc stearate, strontium stearate, lead stearate, barium stearate, cadmium stearate, calcium chlorostearate, and chlorostearate. Examples include barium, cadmium chlorostearate, zinc laurate, barium laurate, cadmium laurate, magnesium laurate, zinc myristate, aluminum myristate, barium ricinoleate, zinc ricinoleate, cadmium ricinoleate, etc., but lead Fatty acid salts of , cadmium, and barium are toxic and should be avoided as much as possible. These metal soaps are made of e.g. Al(OH)
Basic salts such as (C ₁₇ H ₃₅ COO) ₂ and Al(OH) ₂ (C ₁₇ H ₃₅ COO) can also be used. Furthermore, two or more of these fatty acids or metal salts of fatty acids may be used in combination. Too little or too much component (E) will actually reduce the flame retardancy of silicone rubber, so it should be used in a range of 0.05 to 3 parts by weight per 100 parts by weight of component (A). be. The organic peroxide component (F) is a curing agent for this composition, and includes benzoyl peroxide, 2.4-
Examples include dichlor, benzoyl peroxide, 2.5-bis(t-butylperoxy)-2.5-dimethylhexane, dicumyl peroxide, monochlorobenzoyl peroxide, and t-butyl perbenzoate, which can be selected as appropriate depending on the application. used. The amount added is in the range of 0.1 to 5 parts by weight per 100 parts by weight of component (A). In addition to the above-mentioned components (A) to (F), the flame-retardant silicone rubber composition of the present invention may optionally contain low-molecular-weight substances such as dimethylsiloxane, diphenylsilanediol, and alkoxysilane having a hydroxyl group at the terminal. An organic silicon compound may also be blended. Also finely powdered copper, calcium carbonate, calcium zirconate, zirconium silicate, cobalt salts of organic acids, organic phosphorus compounds, azo and triazole compounds, essentially sulfur-free carbon black, metal carbonates, γ-Fe ₂ O _3. Pigments, heat-resistant agents such as cerium oxide and cerium hydroxide, antioxidants, etc. may be added. These compounds are mixed uniformly using a roll kneader or kneader mixer, and then heated at 100 to 450℃ for several seconds.
A silicone rubber product with excellent flame retardancy can be obtained by heating under pressure or non-pressure for 1 hour and, if necessary, secondary heating at 200 to 250°C for 1 to 48 hours. Next, the present invention will be described with reference to Examples, where "Example Middle" indicates parts by weight. The flame retardancy was measured using silicone rubber obtained by heating and curing with a length of 130 mm, a width of 13 mm, and a thickness of 2 mm.
Cut the test piece into a test piece, fix it vertically under no wind, and make sure that the lower end of the test piece is close to the Bunsen burner flame (flame diameter
11mm, inner flame height 20mm, outer flame height 40mm).A flame was applied for 15 seconds at a position slightly touching the top of the inner flame, and then the Bunsen burner was moved away, and the time (seconds) until the flame extinguished was measured. . The flame contact test was performed twice on each of the five test pieces, and the average value (in seconds) of the total of 10 tests was taken as flame retardant data. Example 1 100 parts of organopolysiloxane raw rubber (degree of polymerization 3000) consisting of 99.8 mol% dimethylsiloxane units and 0.2 mol% methylvinylsiloxane units, 5 parts dimethylpolysiloxane having hydroxyl groups at both ends (degree of polymerization 10), diphenyl Silanediol 3
50 parts of fumed silica (Aerosil 200) having a specific surface area of 200 m ² /g were kneaded until uniform, and the mixture was heat-treated at 150° C. for 2 hours to obtain a base compound. To 100 parts of this base compound were added 0.8 parts of 2.4-dichlorobenzoyl peroxide, 5 parts of humid titanium dioxide (Titanoxide P-25), 0.17 parts of a 2% isopropyl alcohol solution of chloroplatinic acid, and 0.5 parts of the fatty acids shown in Table 1. After uniformly mixing with two rolls, heat at 120℃ for 5 minutes at 30Kg/cm ²
The flame retardancy test was carried out under the conditions described above on a 2 mm thick sheet formed by vulcanization under the pressure of . In addition, as a comparative example, any one or two components of fumed titanium dioxide, a 2% isopropyl alcohol solution of chloroplatinic acid, and fatty acids were tested.
A flame retardant test was conducted under the same conditions on a sheet made with the added ingredients under the same conditions.
The results are summarized in Table 1. As shown in Table 1, titanium dioxide alone, fatty acids alone, and the combination of titanium dioxide and fatty acids have no flame retardancy, while platinum alone, the combination of platinum and titanium dioxide, and the combination of platinum and fatty acids have sufficient flame retardancy. Although flame retardance cannot be obtained, the combination of platinum, titanium dioxide, and fatty acids greatly improves flame retardancy. In addition, experiments were also conducted with liquid paraffin and castor oil, but they had almost no effect on flame retardancy.

[Table] Example 2 Using the same base compound as Example 1,
A silicone rubber sheet was prepared under the same conditions as in Example 1 except that a metal salt of a fatty acid was used instead of a fatty acid, and a flame retardancy test was conducted on this sheet. As a comparative example, a silicone rubber sheet was prepared under the same conditions by adding one or two of the following: fumed titanium dioxide, a 2% isopropyl alcohol solution of chloroplatinic acid, and a fatty acid metal salt. Flame retardancy tests were conducted under the following conditions. The results are shown in Table 2. As shown in Table 2, titanium dioxide alone, fatty acid metal salt alone, and the combination of titanium dioxide and fatty acid metal salt have no flame retardancy, while platinum alone, the combination of platinum and titanium dioxide, and the combination of platinum and fatty acid metal salt However, by combining platinum, titanium dioxide, and a fatty acid metal salt, the flame retardance is greatly improved.

[Table] Example 3 Using the same base compound as Example 1,
A silicone rubber sheet was prepared under the same conditions as in Example 1 except that both a fatty acid and a metal salt of a fatty acid were blended, and a flame retardancy test was conducted on this sheet. The results are shown in Table 3. Although there is no synergistic effect even when a fatty acid and a metal salt of a fatty acid are blended, they each have a flame retardant effect comparable to that of each alone.

[Table] Example 4 100 parts of organopolysiloxane raw rubber (degree of polymerization 3500) consisting of 96.5 mol% dimethylsiloxane units, 0.5 mol% methylvinylsiloxane units, and 3 mol% methylphenylsiloxane units, dimethyl having hydroxyl groups at both ends Polysiloxane (degree of polymerization
10) 5 parts of diphenylsilanediol and 55 parts of fumed silica (Aerosil 200) with a specific surface area of 200 m ² /g were kneaded until uniform, and the mixture was treated at 150° C. for 2 hours to obtain a base compound. 0.8 parts of 2.4-dichlorobenzoyl peroxide was added to 100 parts of this base compound, and the components shown in Table 4 were further added, and the mixture was uniformly mixed using two rolls, and then vulcanized in the same manner as in Example 1 to form silicone. A rubber sheet was prepared and a flame retardancy test was conducted on it. The results are shown in Table 4. Note that the same titanium dioxide as used in Example 1 was used.

【table】

Claims (1)

[Scope of Claims] 1 (A) 100 parts by weight of an organopolysiloxane having the average unit formula RaSiO4-a/2 (wherein R is a substituted or unsubstituted monovalent hydrocarbon group, a=1.95-2.05) B) Fine powder silica filler 10-150 parts by weight (C) 2-200 ppm of platinum based on component (1) or a platinum compound containing the same amount of platinum (D) Titanium dioxide 0.5-20 parts by weight (E) Carbon A flame-retardant silicone rubber composition comprising 0.05 to 3 parts by weight of a fatty acid having 10 or more atoms and/or a metal salt of a fatty acid (F) and 0.1 to 5 parts by weight of an organic peroxide.