JPH05287086A - Production of fire-resistant silicone rubber - Google Patents

Abstract

PURPOSE:To produce a silicone rubber excellent in fire resistance by a process with excellent roll processibility and extrusion moldability. CONSTITUTION:A compsn. comprising a diorganopolysiloxane having the mean compsn. formula: R<1>SiO(4-n)/2 (wherein R<1> denotes an optionally substd. monovalent hydrocarbon group provided that each R<2> may be the same as or different from other R<1> s; and n is 1.95-2.05), a reinforcing silica powder having a specific surface area of 100 m<2>/g or higher, a fire-resistant filler, and a crosslinker is diluted by mixing with a diluent comprising a cyclic or linear organopolysiloxane having a degree of polymn. of 10 or lower. The diluent is removed from the mixture during or after extrusion molding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a refractory silicone rubber which is excellent in fire resistance and is therefore capable of industrially advantageously producing a refractory silicone rubber suitable for fire resistant electric wires and the like with excellent roll workability and extrusion moldability. Manufacturing method.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
The fire-resistant portion of the fire-resistant wire is wrapped with a mica impregnated with varnish or the like in the form of a ribbon. However, this ribbon winding has a drawback that the work is complicated and requires labor. Therefore, extrusion molding of the fire resistance-imparting composition is desired, and in particular, an extrusion molding method using a composition in which a fire resistance-imparting filler is mixed with silicone rubber is desired.

However, when a fire resistance-imparting filler such as mica or sericite is added in order to impart a fire resistance to the silicone rubber, the fire resistance is improved as the amount of the filler is increased. There is a problem that the kneading work and the extrusion molding become difficult and finally the work becomes impossible.

Therefore, it is desired to develop a method for industrially producing a refractory silicone rubber which has a good roll workability and an extrusion moldability and is highly filled with a refractory-imparting filler.

[0005]

Means and Actions for Solving the Problems As a result of extensive studies conducted by the present inventor in order to meet the above demand, (A) a diorganopolysiloxane represented by the following average composition formula (1) and a (B) ratio A reinforcing silica powder having a surface area of 100 m ² / g or more, (C) a refractory filler such as mica or celite, and (D) a cross-linking agent (E) a cyclic or linear chain having a polymerization degree of 10 or less. Dilute with organopolysiloxane and mix,
It has been found that a refractory silicone rubber having excellent properties can be produced by a simple operation by removing the component (E) during or after extrusion molding.

R ¹ _n SiO _{(4-n) / 2} (1) (wherein R ¹ is the same or different and is unsubstituted or substituted 1
It is a valent hydrocarbon group, and n is a number from 1.95 to 2.05. )

That is, in the above method, since the organopolysiloxane of the component (E) is used as a diluent, a large amount of a refractory filler capable of imparting fire resistance to a silicone rubber such as mica or celite is blended. However, there is almost no decline in roll workability and extrusion moldability, and therefore it has excellent fire resistance, and it can maintain its original dimensions and shape even after burning after cross-linking molding. The present invention has been accomplished by finding that a suitable fire resistant silicone rubber can be industrially advantageously manufactured with good roll workability and extrusion moldability.

The present invention will be described in more detail below. The component (A) of the present invention is a component that serves as a base material for the refractory silicone rubber, and has a linear or partial structure represented by the following average composition formula (1). Is a branched linear diorganopolysiloxane.

R ¹ _n SiO _{(4-n) / 2} (1) (wherein R ¹ is the same or different and is unsubstituted or substituted 1
It is a valent hydrocarbon group, and n is a number from 1.95 to 2.05. )

In the formula, R ¹ is the same or different, unsubstituted or substituted monovalent hydrocarbon group, and particularly preferably a monovalent hydrocarbon group having 1 to 8 carbon atoms, for example, a methyl group, Alkyl group such as ethyl group, propyl group, butyl group,
Alkenyl group such as vinyl group, allyl group, butenyl group, aryl group such as phenyl group and tolyl group, and chloro group in which some or all of hydrogen atoms bonded to carbon atoms of these groups are substituted with halogen atom, cyano group, etc. A group selected from a methyl group, a trifluoropropyl group, a cyanoethyl group and the like is preferable. Further, n is 1.95 to 2.05, and preferably 1.98 to 2.02. This diorganopolysiloxane has a viscosity of 100 cs at 25 ° C.
Above all, particularly preferably 10,000 to 10,000,000, and if it is less than 100 cs, the rubber after curing may become brittle.

Next, the reinforcing silica powder as the component (B) imparts an appropriate hardness to the silicone rubber and improves the mechanical strength such as tensile strength, and has a specific surface area of 100 m ² / g or more, preferably 100 to 400 m ² / g
Silica powder is used.

As such a reinforcing silica powder, it is preferable to use fumed silica, calcined silica, precipitated silica, etc. either individually or in combination of two or more. The reinforcing silica powder may be surface-treated with a chain organopolysiloxane, a cyclic organopolysiloxane, hexamethyldisilazane, dichlorodimethylsilane, or the like.

The amount of the reinforcing silica powder compounded is 10 with respect to 100 parts by weight of the diorganopolysiloxane of the component (A).
The range of -100 to 100 parts by weight, particularly 10 to 70 parts by weight is preferable. If the compounding amount is more than 100 parts by weight, the rubber strength may be rather lowered or the compression set may be increased, and if it is less than 10 parts by weight, sufficient mechanical strength may not be obtained.

The (C) component refractory filler used in the present invention is capable of imparting fire resistance to silicone rubber, and reduces thermal expansion and shrinkage changes at high temperatures of about 400 ° C to 600 ° C. The crack occurrence rate is greatly reduced.

In this case, examples of the refractory fillers include mica such as muscovite (mascobite), biotite (biotact) and phlogopite (floccobite), and sericite as non-mica.

In all of these refractory fillers, the higher the aspect ratio, the better the reinforcing effect.
Since the change in thermal expansion and contraction at high temperatures of up to about 600 ° C is small, the aspect ratio is 10 or more, especially 5 from the practical point of view.
It is preferably 0 or more.

The amount of component (C) added is 100 parts of component (A).
30 to 500 parts by weight, especially 40 to 150 parts by weight
The range of parts by weight is preferable, and if it is less than 30 parts by weight, sufficient fire resistance may not be obtained, and if it exceeds 500 parts by weight, the silicone rubber becomes brittle and flexibility is not obtained, resulting in poor practicality. There are cases.

Next, the crosslinking agent of the component (D) used in the present invention is for curing the component (A) into a rubber in the presence or absence of a catalyst, which depends on the crosslinking method. Specifically, heat-curable organic peroxides, addition reaction-type organohydrogenpolysiloxanes, and the like are preferably used.

The organic peroxide can be used without any particular limitation as long as it is usually used for curing a peroxide-curable silicone rubber, and examples thereof include benzoyl peroxide and bis (2,4-). Dichlorobenzoyl) peroxide, di-t-butyl peroxide, 2,5-dimethyl-di-t-butylperoxyhexane, t-butylperbenzoate, t-butylperoxyisopropyl carbonate, dicumyl peroxide and the like. Be done. These may be used alone or in combination of two or more. Further, the organic peroxide is
The component (A) is usually used in the range of 0.3 to 6 parts by weight based on 100 parts by weight.

Further, the organohydrogenpolysiloxane may be any organopolysiloxane having two or more SiH groups in one molecule, and may be linear, cyclic or branched. In addition, such Si
The H group may be at the end of the polysiloxane chain or may be in the middle thereof. The above organohydrogenpolysiloxane is preferably used in a ratio such that the SiH group is 0.5 to 10 mol, and particularly 1 to 5 mol per 1 mol of the alkenyl group of the diorganopolysiloxane of the component (A).

When an organohydrogenpolysiloxane is used as a crosslinking agent, a platinum group metal compound is required as an addition reaction catalyst. This platinum group metal-based catalyst acts as a catalyst for the hydrosilylation reaction between the alkenyl group in the (A) component diorganopolysiloxane and the SiH group in the organohydrogenpolysiloxane as a crosslinking agent.

Examples of platinum group metal catalysts include fine powder metal platinum catalysts described in US Pat. No. 2,970,150 and chloroplatinic acid catalysts described in US Pat. No. 2,823,218. U.S. Pat. No. 3,159,601
And the platinum described in No. 3,159,662.
Hydrocarbon complex compounds, chloroplatinic acid-olefin complex compounds described in U.S. Pat. Nos. 3,516,946, and platinum described in U.S. Pat. Nos. 3,775,452 and 3,814,780. -Vinyl siloxane complexes and the like can be used.

The platinum group metal-based catalyst may be used in an amount sufficient to cure the silicone rubber composition, but in order to obtain an economical viewpoint and a good cured state, the amount of diamine of the component (A) should be adjusted. The total amount of the organopolysiloxane and the organohydrogenpolysiloxane as a cross-linking agent is 0.
It is preferably used in the range of 1 to 1,000 ppm, especially 1 to 100 ppm (as platinum metal).

In the present invention, a cyclic or linear organopolysiloxane having a degree of polymerization of 10 or less is blended as the component (E). In this case, the organopolysiloxane as the component (E) is used as a diluent for blending a large amount of the refractory filler, but if it is present in the silicone rubber, it may be a physical problem. Since it is a large amount, it needs to be removed during or after extrusion molding, and thus it is desirable that it is relatively volatile. For this reason, the degree of polymerization of the organopolysiloxane must be 10 or less, and it must be cyclic or linear. Of these, the degree of polymerization of 2 to 8 is preferably linear or 4 to 8. It is a cyclic one, and from the viewpoint of moderate volatility, a cyclic one is particularly preferably used. The component (E) is (A)
It is preferable that they have no reactivity with the component or the component (D) or have poor reactivity, and these may be used as a mixture of two or more kinds.

Here, in the organopolysiloxane of the component (E), the organic group directly connected to the silicon atom in the molecule is, for example, methyl group, ethyl group, propyl group, octyl group, vinyl group, phenyl group, 3,3. , 3-trifluoropropyl group and the like are preferable, and a methyl group is most preferable from the viewpoint of volatility. In the case of a straight chain, one having a molecular end blocked with a triorganosilyl group, particularly a trimethylsilyl group, is preferable. Therefore, those represented by the following general formula are preferably used.

[0026]

[Chemical 1]

If the volatility of the component (E) is too large, it scatters during kneading and the diluting effect is weakened. If the volatility is too small, it is difficult to remove the organopolysiloxane. Among them, octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane having appropriate volatility are preferably used.

Further, the addition amount of the component (E) is (B),
Depending on the amount of the component (C) blended, it is usually 5 to 200 parts by weight, particularly 10 to 10 parts by weight per 100 parts by weight of the component (A).
It is preferably used in the range of 0 parts by weight. If the amount is less than 5 parts by weight, the effect as a diluent is small, so that the component (C) may not be sufficiently blended, and if it exceeds 200 parts by weight, it tends to be uneconomical.

In the silicone rubber of the present invention, in addition to the components (A) to (E), if necessary, for example, pigments, dyes, antioxidants, antioxidants, flame retardants such as antimony oxide and paraffin chloride, A thermal conductivity improver such as boron nitride or aluminum oxide may be blended. Further, rubber compounding agents known per se that are appropriately blended with silicone rubber, such as ground silica, diatomaceous earth, iron oxide, zinc oxide, titanium oxide, carbon black, barium oxide, magnesium oxide, cerium hydroxide, calcium carbonate, Magnesium oxide, zinc carbonate, glass wool, fused silica powder and the like may be added and blended unless the object of the present invention is impaired.

In the method for producing a refractory silicone rubber of the present invention, the component (E) is used as a diluent when the components (A) to (E) are mixed by roll mixing or a kneader. These components are mixed uniformly to remove the component (E) after extrusion or molding. As a result, a large amount of the component (C) can be easily mixed with the component (A) and extrusion molding can be performed, and a silicone rubber having fire resistance that has not been obtained can be easily obtained. ..

In this case, although the components (A) to (E) may be mixed at the same time, depending on the type of the component (D), the curing reaction starts simultaneously with the addition, so the component (D) should be mixed last. You can Further, the component (C) and the component (E) may be mixed at one time, but it is preferable to add them in several times.

There is no particular limitation on the removal of the component (E), but it is preferable to remove it at room temperature to 400 ° C. under normal pressure or reduced pressure. Further, the type of the component (E) used and the state of the silicone rubber are used. Depending on the temperature, it is usually 150 ℃ -300 ℃ under an inert gas stream such as nitrogen gas or helium gas.
It can be removed by heating. Also,
When the component (E) having a high boiling point is used, it may be removed by heating under reduced pressure.

[0033]

Industrial Applicability According to the production method of the present invention, a refractory silicone rubber highly filled with a refractory filler and having excellent fire resistance is industrially produced with excellent roll workability and extrusion moldability. can do. Since this fire resistant silicone rubber has the above-mentioned characteristics and can maintain its original size and shape even after burning after being crosslinked and molded, it can be effectively used as a fire resistant electric wire or the like.

[0034]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 1 to 4, Comparative Examples 1 and 2] Dimethylsiloxane unit 94.825 mol%, methylvinylsiloxane unit 0.15 mol%, diphenylsiloxane unit 5 mol%, dimethylvinylsiloxane unit 0.025 mol% %, 100 parts by weight of a gum-like organopolysiloxane having an average degree of polymerization of 5,000, 3 parts by weight of diphenylsilanediol as a dispersant, 4 parts by weight of a terminal silanol group-containing dimethylpolysiloxane (average degree of polymerization 10) and Aerosil. 40 parts by weight of 200 [fumed silica manufactured by Nippon Aerosil Co., Ltd.] was added, kneaded with two rolls, and then heat-treated at 150 ° C. for 4 hours to prepare a base compound I.

The dimethylsiloxane unit 99.82
Diphenylsilanediol as a dispersant was added to 100 parts by weight of a gum-like organopolysiloxane having an average degree of polymerization of 8,000 consisting of 5 mol%, methylvinylsiloxane unit 0.15 mol% and dimethylvinylsiloxane unit 0.025 mol%. 1 part by weight, 5 parts by weight of terminal silanol group-containing dimethylpolysiloxane (average degree of polymerization: 10) and 50 parts by weight of Aerosil 200 were added, kneaded with two rolls, and then heat-treated at 150 ° C. for 4 hours to obtain a base compound II. Was prepared.

Next, as shown in Table 1, in these base compounds, the amounts of mica, quartz powder, diluent (octamethylcyclotetrasiloxane) shown in Table 1 and an alcohol solution of chloroplatinic acid (Pt concentration) were used. 2%) 0.1 part by weight and 0.7 parts by weight of 2,4-dichlorobenzoyl peroxide as a curing agent were kneaded with a two-roll mill. After kneading uniformly, pressure molding was performed at 120 ° C. for 10 minutes to prepare a rubber sheet having a thickness of 2 mm, which was further heat-treated for 4 hours in a dryer at 200 ° C. in which nitrogen gas was flowed to remove the diluent. Various physical properties of this sheet were measured. Further, the silicone rubber compound was supplied to an extruder equipped with a die having an outer diameter of 10 mm and a cylinder diameter of 40 mm, a ratio of the cylinder length L to the diameter D of L / D = 12, and the extrudability was observed. Further, the extruded round bar-shaped rubber was flushed with nitrogen gas.
Cracking after burning the cured round bar-shaped rubber for 3 hours in an electric furnace at 600 ° C in order to remove the diluent and to see the fire resistance at the same time by heating and curing in a dryer at 50 ° C for 4 hours. Was observed. The above results are shown in Table 1.

[0038]

[Table 1]

From the results shown in Table 1, it was confirmed that the silicone rubber produced by the method of the present invention has excellent fire resistance, roll workability and extrusion moldability. Against these,
The silicone rubber produced without adding octamethyltetrasiloxane as a diluent (Comparative Example 1) could not be molded, and fire resistance was not obtained without mica compounding, and all were impractical.

Continuation of front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location // B29C 47/00 7717-4F (72) Inventor Terukazu Sato 1 Hitomi, Oita, Matsuida-cho, Usui District, Gunma Prefecture 10 Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Research Laboratory

Claims (1)

[Claims] 1. (A) A diorganopolysiloxane represented by the following average composition formula (1): R ¹ _n SiO _{(4-n) / 2} (1) (wherein R ¹ is the same or different from each other). Substitution or substitution 1
It is a valent hydrocarbon group, and n is a number from 1.95 to 2.05. ) (B) Reinforcing silica powder having a specific surface area of 100 m ² / g or more (C) Refractory filler and (D) Crosslinking agent (E) Cyclic or linear organopolysiloxane having a degree of polymerization of 10 or less A method for producing a refractory silicone rubber, which comprises diluting and mixing, and removing the component (E) during or after extrusion molding.