JPH0940867A - Flame retardant silicone composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stable flame retardant silicone composition capable of providing a silicone excellent in flame retardance without using a platinum compound as a flame retardant by blending a polyorganosiloxane as a base polymer with a microencapsulated organic phosphoric ester. SOLUTION: This flame retardant silicone composition is obtained by blending a silicone composition containing a polyorganosiloxane as a base polymer with an organic phosphoric ester (e.g. a triaryl phosphate such as triphenyl phosphate) which is a core substance so as to provide preferably 0.5-10 pts.wt. phosphoric ester based on 100 pts.wt. polyorganosiloxane. A polyurethane, etc., are preferred as a coating material for a microcapsule. When magnesium hydroxide having <=1.5μm average particle diameter is further blended, the flame retardance is preferably further improved. A cross-linking means according to a cross- linking mechanisnl is blended in the objective composition; however, an organic peroxide, e.g. dicumyl peroxide is cited as the cross-linking means.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composition capable of forming a flame-retardant silicone, and more particularly to a composition capable of forming a flame-retardant silicone rubber, silicone gel, silicone resin and the like. More specifically, it relates to a composition capable of forming the above-mentioned silicone having excellent flame retardancy without containing a platinum compound for imparting flame retardancy.

[0002]

BACKGROUND OF THE INVENTION Silicone compositions that cure to form silicone rubber are well known in the art. Silicone rubber is widely used for potting materials, coating materials, molding materials, wire coating materials, etc. for electric and electronic parts by taking advantage of its excellent properties such as excellent heat resistance, electrical insulation and weather resistance. There is. These silicone rubbers are
Since it continues to burn once ignited, there has been proposed a method of blending various flame retardants to obtain a flame-retardant silicone rubber.

Platinum compounds are known as flame retardants that are specifically effective for rubbers using linear polydiorganosiloxane as a base polymer, such as silicone rubber (Japanese Patent Publication No. 44-2591). Publication, Japanese Patent Laid-Open No. 4
No. 8-92452, No. 48-20839, No. 49-356). In order to impart more excellent flame retardancy to silicone rubber, it has been proposed to use such a platinum-based compound in combination with a metal oxide or the like (JP-A-48).
-96650, 48-96651, 4
No. 9-67933, No. 50-97644, No. 50-98961, No. 52-14654.
No. 53-110650, No. 56-5851, No. 56-106957, No. 57-10545.
No. 5, etc.), in particular, many flame-retardant silicone rubber compositions in which a platinum compound is used in combination with titanium oxide, zirconium oxide, zinc oxide, etc. (JP-A-62-13).
No. 453, No. 62-882098, and Japanese Unexamined Patent Publication No. Hei 2
-115268 publication etc.).

It has also been proposed to use a platinum compound and carbon black in combination (JP-A-53-13).
0753, 54-53164, etc.).

On the other hand, a method of blending an organic halogen compound is known as a technique for imparting flame retardancy to a silicone rubber without using the above-mentioned platinum compound (JP-A-55-108454). 58-149948, etc.).

However, among these methods, in the case of the flame-retardant technology in which only the platinum-based compound is blended or in which it is used in combination with other substances, if the blending amount is increased, the characteristics such as heat resistance are deteriorated. May have an adverse effect. In addition, platinum compounds are expensive, and their use not only raises the manufacturing cost, but also has resource limitations. Technology has come to be required.

On the other hand, the one using an organic halogen compound requires a large amount of the organic halogen compound in order to impart flame retardancy to the composition. There is a problem that it adversely affects the properties of rubber and the surrounding atmosphere. Further, since the organic halogen compound is decomposed,
Flame retardance cannot be maintained for a long time. Furthermore, depending on the type and amount of the organic halide to be blended, there is a problem that the heat resistance characteristic of silicone is significantly lowered.

Organic phosphoric acid esters are widely used as flame retardants for plastics and organic rubber. As for silicone, a fireproof airtight sealant containing an organic phosphoric acid ester has been proposed (JP-A-57-1414).
No. 76). However, when such an organic phosphate ester is applied to the flame retardant of silicone, the solubility index (SP value) of polydiorganosiloxane, which is the base polymer of silicone rubber, is 7.3, whereas that of the organic phosphate ester is SP. Since the value is around 10, the organophosphate ester compounded in the silicone bleeds over time, and the flame retardancy of the silicone decreases during storage and use.

In addition, in the case of an addition reaction type silicone which uses a platinum compound as a curing catalyst, the compounded organic phosphate ester acts as a catalyst poison for the platinum catalyst, which causes curing inhibition. There are also problems.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the silicone flame retardant technology. In other words, it causes an increase in manufacturing cost,
Without using platinum-based compounds that are resource-problematic,
Also, without adversely affecting the characteristics and atmosphere of the product,
An object of the present invention is to provide a composition capable of forming a silicone having excellent flame retardancy which does not change with time.

[0011]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that by encapsulating an organic phosphoric acid ester into a silicone composition by microencapsulation, It was found that the above-mentioned object can be achieved without causing a decrease in flame retardancy or inhibition of curing, and further that the effect is more remarkably exhibited by blending a specific magnesium hydroxide. As a result, the present invention has been completed.

That is, according to the present invention, a silicone composition containing (A) a polyorganosiloxane as a base polymer contains (B) a microencapsulated organic phosphoric acid ester, and preferably further has an average crystal particle diameter. Relates to a flame-retardant silicone composition characterized by containing magnesium hydroxide of 1.5 μm or less.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The flame-retardant silicone composition of the present invention is a composition capable of forming a flame-retardant silicone by a reaction. Examples of the flame-retardant silicone include flame-retardant silicone rubber and flame-retardant silicone rubber. Examples include silicone gel and flame-retardant silicone resin. INDUSTRIAL APPLICABILITY The present invention is particularly useful in the field of silicone rubber and silicone gel, which have not been able to obtain excellent flame retardancy without using a platinum compound.

The silicone composition to which the present invention is applied is
The silicone rubber composition, the silicone gel composition, and the silicone resin composition are roughly classified according to the form of the silicone finally used, but are not limited thereto.

The silicone rubber composition comprises a polydiorganosiloxane which is a base polymer, and a crosslinking means for crosslinking it, and if necessary, a filler and other additives are mixed therein, and the crosslinking mechanism thereof is used. as,
An organic peroxide cross-linking type in which an organic peroxide is used as a cross-linking means and a vinyl group bonded to a silicon atom of a base polymer and a methyl group or methyl groups are reacted; a hydroxyl group bonded to a silicon atom as a base polymer or hydrolysis Condensation reaction type using a polydiorganosiloxane having a functional group and a silane or siloxane having a silicon functional group as a cross-linking agent, generally together with a catalyst;
And a polydiorganosiloxane having a vinyl group bonded to a silicon atom as a base polymer, and optionally a branched polyorganosiloxane, and a polyorganohydrogensiloxane as a cross-linking agent together with a platinum-based catalyst. Are known and are not limited to these.

The silicone gel composition forms the polysiloxane chain formed by the crosslinking reaction in the above silicone rubber composition by extremely reducing the crosslink density or forming an intermeshed polysiloxane chain. It forms the resulting soft solid and is generally formed by the same addition reaction as in the silicone rubber composition described above.

The silicone resin composition is composed of a polydiorganosiloxane having a high degree of polymerization having a hydroxyl group condensed on silicon atoms at both ends, a triorganosiloxy unit and a SiO _4/2 unit, and if necessary, a small amount of diene. A composition containing a polyorganosiloxane which may contain an organosiloxane unit, has a branched or network siloxane skeleton, and is obtained by condensing a polyorganosiloxane having a hydroxyl group bonded to a silicon atom; A composition containing a relatively low molecular weight polyorganosiloxane having a silicon functional group such as a bound hydroxyl group and / or an alkoxy group and capable of forming a network polymer by its polycondensation reaction; and the above silicone rubber composition. Polio forming a reticulated polysiloxane skeleton by an addition reaction similar to that in An example is a luganosiloxane composition, and if necessary, a solvent and / or a filler and other additives are added.

The polyorganosiloxane (A) in these silicone compositions is generally a chain polydiorganosiloxane, depending on the type of silicone, or a mixture of it with a branched or reticulated polyorganosiloxane or a condensation product. However, it is not particularly limited.
Examples of the organic group bonded to the silicon atom include a chain or branched alkyl group such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl and dodecyl; a cycloalkyl group such as cyclohexyl; vinyl, allyl, 1 -Alkenyl groups such as butenyl; aryl groups such as phenyl and tolyl; 2-phenylethyl, 2
An aralkyl group such as phenylpropyl; a halogen-substituted hydrocarbon group such as chloromethyl, 3-chloropropyl, 3,3,3-trifluoropropyl, p-chlorophenyl; a cyano-substituted hydrocarbon group such as 3-cyanopropyl; and Examples thereof include alkoxy-substituted hydrocarbon groups such as 3-methoxypropyl, which may be the same or different. The composition before curing has a viscosity range that is easy to handle, and the composition after curing has excellent physical properties, for example, silicone rubber has excellent rubber elasticity, and heat resistance which is a characteristic of polyorganosiloxane, Since it typically shows various properties such as cold resistance and weather resistance, 90% or more is preferably a methyl group, and it is more preferable that substantially all are a methyl group. Further, when heat resistance, cold resistance and / or radiation resistance are required, a phenyl group is used. When solvent resistance is required, 3,
A 3,3-trifluoropropyl group can be appropriately introduced as at least a part.

In the polyorganosiloxane, the group participating in the reaction is bonded to the silicon atom, as described above, depending on the reaction (crosslinking) mechanism. That is, in the organic peroxide cross-linking type, only a methyl group may be present as a group that participates in the reaction, but a small amount of the organic peroxide causes the cross-linking reaction to proceed in a chain manner, and the acyl-based peroxide alone However, since a wide range of other organic peroxides are used, it is preferable to have a vinyl group as a part of the organic group. The amount of vinyl groups is preferably 0.02 to 8 mol%, and particularly preferably 0.05 to 0.2 mol%, based on all organic groups. The vinyl group may be bonded to the silicon atom at either the molecular end or the molecular middle part.

The condensation reaction type of (1) has a hydroxyl group or a hydrolyzable group which participates in the condensation reaction. Hydrolyzable groups include alkoxy groups such as methoxy and ethoxy; enoxy groups such as isopropenyloxy; acyloxy groups such as acetoxy; ketooxymato groups such as acetone oximato and methyl ethyl ketoximato; diethylaminoxy and the like. Examples thereof include diorganoaminoxy group. It is preferable that such a group be bonded to a silicon atom at the terminal of the molecule in terms of easy synthesis, reactivity and physical properties of the silicone after crosslinking.

The addition reaction type of (1) has a vinyl group for reacting with the hydrosilyl group of the crosslinking agent. The vinyl group may be bonded to any silicon atom at the molecular end or in the middle part of the molecule, but at least a part thereof is bonded to the silicon atom at the molecular end due to excellent reactivity and physical properties of the silicone after the reaction. It is preferable that Further, in the case of a silicone rubber composition based on this type of crosslinking mechanism, in order to obtain particularly excellent mechanical properties, in addition to the linear polydiorganosiloxane, a branched polyorganosiloxane is used in combination as a part of the base polymer. You may.

The degree of polymerization of the polyorganosiloxane (A) also varies depending on the form of use. In the case of silicone rubber, in a form of use in which a solid composition containing a filler is masticated with a roll and then molded, and crosslinked, or dissolved or dispersed in a solvent and applied to a glass fiber sleeve or the like, Usually, those having a polymerization degree of 3,000 to 10,000, preferably 5,000 to 8,000 are used. On the other hand, when a composition having fluidity or extrudability is used for casting, potting, coating, sealing, etc., the polydiorganosiloxane of 2 is used.
The viscosity at 5 ° C is usually selected to be 300 to 200,000 cP, preferably 2,000 to 100,000 cP. Further, in order to control the fluidity and workability of the composition and to give a silicone obtained by curing a surface having a high lubricity, a polydiorganosiloxane such as a non-reactive polydimethylsiloxane may be added. Good.

The (B) microencapsulated organic phosphoric acid ester uses an organic phosphoric acid ester as a core substance, and this is subjected to a well-known chemical, physicochemical or mechanical / physical microencapsulation method. It is microencapsulated by using.

The organic phosphate used in the present invention is
Orthophosphoric acid, metaphosphoric acid, and polyphosphoric acid are compounds in which some or all of the hydrogen atoms are substituted with a hydrocarbon group or a halogenated hydrocarbon group, and examples include phosphoric acid triaryl esters, phosphoric acid diarylalkyl esters, and phosphoric acid. Examples thereof include aryl dialkyl esters, phosphoric acid trialkyl esters, acidic phosphoric acid esters, condensation type phosphoric acid esters, halogen-containing phosphoric acid esters and the like. These are disclosed in JP-A-52-48628 and JP-A-5-48628.
It is described in JP-A-7-141476 and JP-A-2-59040.

Specific examples of the phosphoric acid triaryl ester include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, phenyl dicresyl phosphate, trixylenyl phosphate, xylenyl diphenyl phosphate, phenyl dixylenyl. Phosphate, (ethylphenyl) diphenylphosphate, bis (ethylphenyl) phenylphosphate, (triisopropylphenyl) (diisopropylphenyl) phenylphosphate, dicumenyl (triisopropylphenyl) phosphate, cumenyl (triisopropylphenyl) phenylphosphate, (triisopropylphenyl) ) Diphenyl phosphate, cumenyl bis (diisopropylphenyl) phosphate, bis (diisopropylpropionate) Phenyl) phenyl phosphate,
Dicumenyl (diisopropylphenyl) phosphate,
Cumenyl (diisopropylphenyl) phenylphosphate, (diisopropylphenyl) diphenylphosphate, tricumenylphosphate, dicumenylphenylphosphate, cumenyldiphenylphosphate, tris (tert-butylphenyl) phosphate, (tert-butylphenyl) diphenylphosphate, bis (tert) −
Butylphenyl) phenyl phosphate and the like are exemplified.

As the phosphoric acid diaryl alkyl ester, butyl diphenyl phosphate, octyl diphenyl phosphate, nonyl diphenyl phosphate, lauryl diphenyl phosphate, butyl dicresyl phosphate, octyl dicresyl phosphate, nonyl dicresyl phosphate, lauryl dicresyl phosphate, butyl dixylyl ester. Nyl phosphate, octyl dixylenyl phosphate, nonyl dixylenyl phosphate, lauryl dixylenyl phosphate, butyl bis (isopropylphenyl) phosphate, octyl bis (isopropylphenyl) phosphate, nonyl bis (isopropylphenyl) phosphate, lauryl bis (isopropylphenyl) phosphate, butyl Phenylcresyl phosphate, Chill phenyl carboxymethyl les sulfonyl phosphate, butylphenyl (isopropylphenyl)
Phosphate etc. are illustrated.

Examples of the aryl dialkyl phosphate include dibutylphenyl phosphate, dioctylphenyl phosphate, dinonylphenyl phosphate, dilaurylphenyl phosphate, butyloctylphenyl phosphate, octylnonylcresyl phosphate and the like.

Examples of the phosphoric acid trialkyl ester include trimethyl phosphate, triethyl phosphate, tri (n-propyl) phosphate, tri (isopropyl).
Examples thereof include phosphate, tri (n-butyl) phosphate, tri (sec-butyl) phosphate, tri (isobutyl) phosphate, tri (2-ethylhexyl) phosphate, tridecylphosphate, tristearylphosphate and the like.

Examples of the acidic phosphoric acid ester include methyl phosphate, dimethyl phosphate, ethyl phosphate, diethyl phosphate, n-propyl phosphate, di (n-propyl) phosphate, isopropyl phosphate, di (isopropyl) phosphate, n-butyl phosphate, diphosphate. (N-butyl) phosphate, se
c-Butyl phosphate, di (sec-butyl) phosphate, isobutyl phosphate, di (isobutyl) phosphate, 2-ethylhexyl phosphate, bis (2
-Ethylhexyl) phosphate, decyl phosphate, didecyl phosphate, stearyl phosphate,
Distearyl phosphate, phenyl phosphate, diphenyl phosphate, cresyl phosphate, dicresyl phosphate, xylenyl phosphate, dixylenyl phosphate, (ethylphenyl) phosphate,
Bis (ethylphenyl) phosphate, isopropylphenylphosphate, bis (isopropylphenyl) phosphate, (diisopropylphenyl) phosphate, bis (diisopropylphenyl) phosphate,
Examples thereof include (tert-butylphenyl) phosphate, bis (tert-butylphenyl) phosphate, phenylcresyl phosphate, phenylxylenyl phosphate, phenylcumenyl phosphate, phenyl (tert-butylphenyl) phosphate.

Examples of the condensed type phosphoric acid ester include resorcinol bis (diphenyl phosphate), resorcinol bis (dicresyl phosphate), resorcinol bis (dixylenyl phosphate), bisphenol A bis (diphenyl phosphate), bisphenol A.
Examples thereof include bis (dicresyl phosphate), bisphenol A bis (dixylenyl phosphate), hydroquinone bis (diphenyl phosphate), hydroquinone bis (dicresyl phosphate), and hydroquinone bis (dixylenyl phosphate).

Examples of the halogen-containing phosphate ester include tris (2-chloroethyl) phosphate and tris (1,3
-Dichloropropyl) phosphate, tris (2-chloropropyl) phosphate, tris (2-bromoethyl) phosphate, tris (1,3-dibromopropyl) phosphate, tris (2-bromopropyl) phosphate, tris (2,4-dibromo) Examples include phenyl) phosphate, tris (2,4,6-tribromophenyl) phosphate, tris (tribromoneopentyl) phosphate, and the like.

These organic phosphoric acid esters may be used alone or as a mixture of two or more kinds.

Specific examples of the microencapsulation method of the organic phosphate ester include interfacial polycondensation method, in situ polymerization method, in-liquid curing coating method as a chemical method, and a simple physicochemical method as a physicochemical method. There are a coacervation method, a complex coacervation method, an interfacial precipitation method, an interfacial concentration method, an interfacial precipitation method, and the like. Further, as a mechanical / physical method, there are a spray drying method and a dry mixing method. More specific preparation examples are disclosed in JP-A-50-105555 and JP-A-61-2.
54388, JP-A-62-161706,
It is described in JP-A-2-59040. As the coating substance, cross-linked gelatin, melamine-formaldehyde resin, polyurea, polyurethane, polystyrene,
Examples thereof include polyester and epoxy resin, and among them, melamine-formaldehyde resin, polyurea and polyurethane are preferable. The average particle size of the microcapsules can be adjusted to 1 to 2,000 μm, but from the viewpoint of dispersibility in the resin, it is preferably 100 μm or less.

The ratio of the organic phosphoric acid ester, which is the core substance, in the microcapsules to the coating substance is usually 0.1 to 200% by weight, preferably 0.1 to 200% by weight, based on the organic phosphoric acid ester in the coating substance. Is about 20% by weight. If this proportion is less than 0.1% by weight, the coating becomes thin and it becomes difficult to prepare stable microcapsules. In addition, this ratio is 200
If the content exceeds 100% by weight, the content of the organic phosphate ester in the microcapsules becomes low, and a large amount of microcapsules must be added to obtain the desired flame retardancy, which is a cost disadvantage. , The physical properties of the obtained silicone may be adversely affected.

The compounding amount of the (B) microencapsulated organic phosphoric acid ester is 0.1 to 20 parts by weight of the phosphoric acid ester as a core substance with respect to 100 parts by weight of the polyorganosiloxane of (A). Is preferably 0.5 to
An amount of 10 parts by weight is more preferable. This amount is 0.1
If it is less than 10 parts by weight, the flame retardancy of the silicone after crosslinking is not sufficient, and if it exceeds 20 parts by weight, its mechanical properties may deteriorate.

The flame-retardant silicone composition of the present invention comprises
In addition to (A) polyorganosiloxane and (B) microencapsulated organic phosphate ester, a crosslinking means and, if necessary, a filler, a solvent and / or various additives may be added depending on the above-mentioned crosslinking mechanism. Be compounded.

As a crosslinking means, in the case of an organic peroxide crosslinking type, as a curing agent (also referred to as a vulcanizing agent), benzoyl peroxide, p-chlorobenzoyl peroxide,
Acyl-based peroxides such as 2,4-dichlorobenzoyl peroxide; and di-tert-butyl peroxide, cumyl-tert-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di-tert-butylperoxyhexane, etc. Various organic peroxides, such as the alkyl peroxides of ## STR3 ## are used and give a particularly low compression set, so that cumyl-tert-butyl peroxide, dicumyl peroxide and 2,5-dimethyl-2,5-dioxide are used. -Tert-Butylperoxyhexane is preferred. These organic peroxides may be used alone or in combination of two or more.

The amount of the organic peroxide compounded is 0.05 to 15 with respect to 100 parts by weight of the polyorganosiloxane (A).
A range of parts by weight is preferred. The amount of organic peroxide blended is 0.
If the amount is less than 05 parts by weight, crosslinking will not be sufficiently carried out, and if the amount is more than 15 parts by weight, not only there will be no particular effect but also the physical properties of the obtained silicone rubber molded product may be adversely affected.

In the condensation reaction type, as a crosslinking agent, ethyl silicate, propyl silicate, methyltrimethoxysilane, vinyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, methyltris (2-methoxyethoxy) silane, vinyltris ( 2-
Silane containing a substituted or unsubstituted alkoxy group such as methoxyethoxy) silane; silane containing an enoxy group such as methyltriisopropenyloxysilane; methyltriacetoxysilane, vinyltriacetoxysilane, di-
Acyloxy group-containing silanes such as tert-butoxydiacetoxysilane; oximato group-containing silanes such as methyltris (acetoneoxymato) silane, vinyltris (acetoneoxymato) silane, methyltris (methylethylketoximato) silane, vinyltris (methylethylketoximato) silane And as well as their partial hydrolysis-condensation products. Further, hexamethylbis (diethylaminoxy) cyclotetrasiloxane, tetramethyldibutylbis (diethylaminoxy) cyclotetrasiloxane, pentamethyltris (diethylaminoxy) cyclotetrasiloxane, hexamethylbis (methylethylaminoxy) cyclotetrasiloxane, penta A cyclic siloxane containing a diorganoaminoxy group such as methylbis (diethylaminoxy) mono (methylethylaminoxy) cyclotetrasiloxane is also exemplified. These crosslinking agents may be used alone or in combination of two or more. Further, a part or all of these cross-linking agents may be reacted with the terminal hydroxyl group of the base polymer α, ω-dihydroxypolydiorganosiloxane to be used as the base polymer.

The compounding amount of the crosslinking agent is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the polyorganosiloxane (A). If the amount is less than 0.1 parts by weight, the rubber after curing cannot obtain sufficient mechanical properties except for the type in which the above-mentioned cross-linking agent is reacted with the terminal groups of the base polymer in advance, and exceeds 20 parts by weight. Then, the obtained rubber becomes brittle.

Further, in such a condensation reaction type,
A curing catalyst for accelerating the crosslinking reaction is used except when a siloxane having a diorganoaminoxy group is used as the crosslinking agent. As the curing catalyst, iron octoate, cobalt octoate, manganese octoate, tin octoate, tin naphthenate, tin caprylate, tin oleate and other carboxylic acid metal salts; and dimethyltin monooleate, dibutyltin diacetate, dibutyltin dioctoate, Dibutyltin dilaurate,
Examples of organic tin compounds such as dibutyltin dioleate, diphenyltin diacetate, dibutyltin oxide, dibutyltin dimethoxide, dibutylbis (triethoxysiloxy) tin, and dioctyltin dilaurate, and excellent curability are obtained, so dibutyltin diacetate, Dibutyltin dioctoate and dibutyltin dilaurate are preferred.

The compounding amount of the curing catalyst is preferably in the range of 0.01 to 5 parts by weight with respect to 100 parts by weight of (A) polyorganosiloxane. If it is less than 0.01 parts by weight, it takes a long time to cure, and the curing in the interior far from the contact surface with air becomes insufficient. On the other hand, if it exceeds 5 parts by weight, the storage stability is poor. A more preferable range of the compounding amount is 0.1 to 3 parts by weight.

The addition reaction type crosslinking mechanism of (3) is used not only in silicone rubber compositions but also in silicone gel compositions and silicone resin compositions, and has a very wide range of applications. In addition, in some silicone gels, polydiorganosiloxane having a vinyl group only at one end is used as a base polymer to form an extremely branched polysiloxane by an addition reaction, and the gel is formed by entanglement of molecular chains. Some are present, but for convenience, they are treated in the same way as crosslinking in this specification.

As the addition reaction type cross-linking agent, a polyorganohydrogensiloxane having an average of more than two hydrogen atoms bonded to silicon atoms in one molecule is used. The siloxane skeleton of the polyorganohydrogensiloxane may be linear, branched, cyclic, or branched cyclic, or a mixture thereof.
The viscosity is preferably in the range of 5 to 500 cP at 25 ° C. If it is less than 5 cP, it is volatile and cannot be used stably.
When it exceeds 00 cP, workability such as mixing is deteriorated.

The amount of the cross-linking agent to be blended is preferably such that 0.5 to 4.0 hydrogen atoms bonded to silicon atoms in the cross-linking agent per one vinyl group in the component (A). 1.
The amount is preferably 0 to 3.0. If the number of hydrogen atoms is less than 0.5, the composition will not be sufficiently cured, and the composition will have a low hardness. If the number of hydrogen atoms exceeds 4.0, the physical properties and heat resistance of the composition after curing will deteriorate.

Further, in the addition reaction type, a trace amount of platinum-based catalyst is used as a catalyst for promoting the hydrosilylation reaction. Examples of such a platinum catalyst include chloroplatinic acid, a complex obtained from chloroplatinic acid and an alcohol such as octyl alcohol, a platinum olefin complex, a platinum vinylsiloxane complex, and platinum black.

The amount of the curing catalyst compounded is 0.1 to 1, as the amount of platinum atom based on the polyorganosiloxane (A).
Quantities in the range of 000 ppm are preferred, 0.5-200
ppm is more preferred. If this amount is less than 0.1 ppm, curing will not proceed sufficiently, and if it exceeds 1,000 ppm, no particular improvement in the curing rate can be expected.

In order to impart desired physical properties to the flame-retardant silicone composition of the present invention, various fillers may be added in appropriate amounts, if necessary. As the filler used, fine powder silica, silica airgel, precipitated silica, diatomaceous earth, ground quartz, fused silica, aluminum oxide,
Oxides such as iron oxide, zinc oxide, titanium oxide, and cerium oxide; hydroxides such as magnesium hydroxide and aluminum hydroxide; carbonates such as calcium carbonate, magnesium carbonate, zinc carbonate; talc, clay, glass beads, mica Complex oxides such as fine powders; those whose surface has been treated with a hydrophobizing agent such as trimethylchlorosilane, dimethyldichlorosilane, hexamethyldisilazane or octamethylcyclotetrasiloxane; carbon black, copper powder, nickel Conductive fillers such as powders; and polymethylsilsesquioxane powders are exemplified.

Among these, the inventors have found that the flame retardancy of the silicone composition can be further improved by adding magnesium hydroxide having an average particle diameter of 1.5 μm or less. Generally, magnesium hydroxide forms colloidal crystals, and the average particle size is usually 3 μm or more. Such magnesium hydroxide has a strong cohesive property between particles, and when compounded in a silicone composition, it is difficult to uniformly disperse it in the composition by a kneading operation. Therefore, a silicone composition containing such magnesium hydroxide cannot have good physical properties after the crosslinking reaction. In the present invention, by blending magnesium hydroxide having an average particle diameter of 1.5 μm or less, it becomes possible to disperse the particles uniformly in the silicone composition, and in combination with the effect of the component (B), after the crosslinking reaction. The flame retardancy of the silicone composition can be further improved. The magnesium hydroxide having an average crystal grain size of 1.5 μm or less used here exists substantially in a single crystal state.

The compounding amount of such magnesium hydroxide varies depending on the kind of the silicone composition and the required flame retardancy, but it is (A) polyorganosiloxane 100.
A range of 5 to 200 parts by weight is preferable with respect to parts by weight, and 1
0 to 50 parts by weight is more preferable. If the amount is less than 5 parts by weight, the effect is small, and if the amount is more than 200 parts by weight, the mechanical properties of the silicone obtained by crosslinking are deteriorated.

Further, if necessary, the composition of the present invention may contain pigments, dyes, heat resistance improvers, thermal conductivity improvers, adhesion improvers, thixotropy imparting agents, curing retardants, processing aids, and the like. You may mix | blend. Dilute with a hydrocarbon solvent such as toluene, xylene, petroleum ether, gasoline, benzine, kerosene; a ketone solvent such as acetone or methyl ethyl ketone; or an organic solvent typified by an ester solvent such as ethyl acetate or butyl acetate. You may use it.

The feature of the silicone composition of the present invention is that excellent flame retardancy can be obtained without using a platinum compound. However, the present invention is based on the platinum compound used in the conventional flame retardant technology. Does not prevent the catalyst used for the hydrosilylation reaction from remaining in the composition and contributing as a flame retardant. Examples of the platinum compound used as the flame retardant include chloroplatinic acid and the like, those exemplified as the catalyst earlier, and platinum triphenylphosphine complex and the like.

The composition of the present invention can be prepared by kneading, mixing and the like by a known method depending on the kind of the base polymer, the crosslinking mechanism and the shape of the composition. Depending on the crosslinking mechanism, when a composition containing the base polymer and the crosslinking means is prepared, the crosslinking reaction proceeds even at room temperature. Therefore, in such a system, at least one component constituting the base polymer and the crosslinking means is placed in a separate container. Save it
Mixing the synthetic components immediately before use; storing in the presence of a curing retarder; or storing in a moisture-tight container so as to block moisture in the air involved in the crosslinking reaction and extruding immediately before use, etc. The method of can be adopted. The crosslinking reaction is
Depending on the crosslinking mechanism, it can proceed at room temperature or by heating to a known predetermined temperature.

[0054]

According to the present invention, a stable composition capable of forming a silicone having excellent flame retardancy can be obtained without using a platinum compound as a flame retardant. From the silicone composition obtained by the present invention, by a crosslinking reaction,
Silicone rubber, silicone gel, silicone resin, etc. having outstanding flame retardancy, such as silicone rubber conforming to UL94V-0, can be obtained, and these are mounted on vehicles, ships, household electrical appliances, etc. that require flame retardancy. It is extremely useful as a material for parts and equipment used, and as an adhesive / sealant used therefor.

[0055]

The present invention will be described more specifically with reference to the following examples and comparative examples. In these examples, parts indicate parts by weight, and all physical properties such as viscosity are values at 25 ° C. The invention is not limited by these examples. The following abbreviations are used in the chemical formulas of polyorganosiloxanes and their explanations. Me: methyl group; Vi: vinyl group

Example 1 By the coacervation method, microcapsules containing 67% of tricumenyl phosphate and coated with a cross-linked gelatin film and having an average particle size of 10 μm were prepared.

That is, 80 parts of a 5% aqueous solution of gelatin was kept at 50 ° C. and stirred, and 30 parts of tricumenyl phosphate was added dropwise. Then, 80 parts of a 5% aqueous solution of gum arabic was added dropwise, 100 parts of water was added, and then acetic acid was added dropwise to adjust the pH to 4. 10 ℃
The mixture was cooled to 3 parts, and 3 parts of a 37% aqueous solution of formaldehyde was added dropwise. After completion of the addition, stirring was continued for 1 hour to crosslink the gelatin, and the mixture was filtered to give microcapsules M- coated with tricumenyl phosphate with crosslinked gelatin.
1 was obtained.

Average formula:

Embedded image And 100 parts by weight of a vinyl group-containing polydimethylsiloxane having a viscosity of 700 cP,
-1, which is obtained by heating 3.0 parts of chloroplatinic acid and tetramethyltetravinylcyclotetrasiloxane,
Platinum complex containing 2.0% of platinum as platinum atom 0.0
And 3 parts were added and stirred with a mixer. While continuing stirring, average formula:

Embedded image And 0.45 parts by weight of polymethylhydrogen siloxane having a viscosity of 50 cP (however, the average formula represents a ratio of siloxane units and is a random polymer) is added to prepare a uniform composition. did.

Comparative Example 1 A composition was obtained in the same manner as in Example 1 except that microcapsules were not added.

Evaluation Example 1 (Silicone Gel) Each of the molds obtained in Example 1 and Comparative Example 1 was molded into a mold having a cavity having a length of 100 mm, a width of 10 mm, and a thickness of 2 mm, the surface of which was coated with polytetrafluoroethylene. All the compositions were injected immediately after preparation, charged in an open at 150 ° C. and heated for 2 hours to obtain gel-like test pieces.

A burner flame having an outer flame length of 5 cm and a closed flame length of 3 cm was produced using a burner using propane gas as a fuel. Each test piece was subjected to indirect flame under the burner flame for 30 seconds, and the generation of flame from the test piece and the combustion state after being separated from the burner flame were observed. The results were as shown in Table 1.

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[Table 1]

Example 2 Microcapsules containing 75% tricresyl phosphate and coated with a melamine-formaldehyde resin film and having an average particle size of 0.5 μm were prepared by an in situ polymerization method.

That is, 30 parts of tricresyl phosphate was added to 150 parts of a 3% aqueous solution of polyvinyl alcohol, and 15 parts of a melamine-formaldehyde initial condensate was added with stirring. Raise the temperature to 70 ° C and use acetic acid
The initial condensate was further condensed by adjusting the pH to 3.5 to 4.0 and further stirring for 3 hours to obtain microcapsules M-2 in which tricresyl phosphate was coated with a melamine-formaldehyde resin. Obtained.

Methyl vinyl siloxane unit 0.2 mol%
And the remaining dimethylsiloxane units, the end groups are blocked with trimethylsiloxy units, and the average degree of polymerization is 7,000.
100 parts of polydiorganosiloxane of 0, 1.5 parts of low molecular weight polymethylphenylsiloxane, average particle size of 3
2.0 parts of rutile titanium dioxide with a specific surface area of 2
Twenty-five parts of 00 m ² / g fumed silica was kneaded with a kneader, and then 3.0 parts of the above-mentioned microcapsules M-2 were added to continue kneading to obtain a silicone rubber mixture. In addition to this, using a two-roll mill, 2,5-dimethyl-2,5-di-
Knead 0.5 parts of tert-butyl peroxyhexane,
A silicone rubber composition was obtained.

Example 3 During kneading with a kneader, an average crystal grain size of 0.
A silicone rubber mixture was obtained in the same manner as in Example 2 except that 20 parts of 7 μm magnesium hydroxide was added. The same organic peroxide as in Example 2 was kneaded in the same manner to obtain a silicone rubber composition.

Example 4 A silicone rubber composition was obtained in the same manner as in Example 3 except that 20 parts of magnesium hydroxide having an average particle size of 15 μm was added instead of magnesium hydroxide having an average crystal particle size of 0.7 μm. It was

Comparative Example 2 A silicone rubber composition was prepared in the same manner as in Example 2 except that the microcapsules M-2 were not added.

Evaluation Example 2 (Organic Peroxide Crosslinking Silicone Rubber) Each of the silicone rubber compositions obtained in Examples 2 to 4 and Comparative Example 2 was molded into a sheet having a thickness of 1 mm and a thickness of 2 mm. After press vulcanization at 10 ° C for 10 minutes, 2
Hot air vulcanization was performed at 00 ° C. for 4 hours, and the temperature was returned to room temperature to produce each silicone rubber sheet.

The silicone rubber sheet thus obtained was tested for flame retardancy based on UL94.
The results were as shown in Table 2.

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[Table 2]

Example 5 Tricumenyl phosphate was added to 60 by the interfacial polymerization method.
% And coated with polyurea, the average particle size is 1.
2 μm microcapsules were prepared.

That is, while stirring 150 parts of a 3% aqueous solution of polyvinyl alcohol, 3% of 1,3-bis (hydrazinocarboethyl) -5-isopropylhydantoin was added.
20 parts of aqueous solution was added. While continuing stirring at 50 ° C, 30 parts of tricumenyl phosphate and biuret-type hexamethylene diisocyanate (Sumitomo Bayer Urethane Co., Ltd.)
Manufactured by Sumidule N-75) and 2 parts of the mixture,
At the interface between the tricumenyl phosphate phase and the aqueous phase, the hydrazine compound and the isocyanate compound are reacted to form polyurea, whereby the microcapsules M- coated with tricumenyl phosphate by polyurea are formed.
3 was obtained.

The terminal is blocked with a silanol group and the viscosity is 1
A surface area of 200 parts obtained by surface-treating dimethyldichlorosilane with 100 parts of 9000 cP polydimethylsiloxane.
fumed silica 14 parts of m ² / g, the microcapsule M
3-10 parts, methyltris (methylethylketoximato) silane 8 parts, and dibutyltin dilaurate 0.
Two parts were dried and kneaded uniformly using a moisture-proof mixer to prepare a paste-like silicone rubber composition, which was stored in a moisture-impermeable container.

Example 6 A silicone rubber composition was prepared in the same manner as in Example 5 except that 15 parts of magnesium hydroxide having an average crystal particle size of 0.7 μm was further added to the composition used in Example 5. , Stored in a similar container.

Comparative Example 3 A silicone rubber composition was prepared in the same manner as in Example 5 except that the microcapsules M-3 were not blended and stored in the same container.

Comparative Example 4 In the same manner as in Example 5 except that tricumenyl phosphate was directly blended in place of the microcapsule M-3,
A silicone rubber composition was prepared and stored in a similar container.

Evaluation Example 3 (condensation reaction type silicone rubber) The silicone rubber compositions obtained in Examples 5 and 6 and Comparative Examples 3 and 4 were extruded into sheets having a thickness of 1 mm and 2 mm, respectively, and the temperature was 25 ° C. By standing in a thermo-hygrostat with a relative humidity of 90% for 7 days, the crosslinking reaction is completed,
A cured silicone rubber sheet was prepared.

The thus obtained silicone rubber sheet was tested for flame retardancy based on UL94.
The results were as shown in Table 3.

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[Table 3]

The surface of the silicone rubber sheet obtained by crosslinking the sample obtained from the composition of Comparative Example 4 in a thermo-hygrostat was wet. When the liquid adhering to the surface was analyzed, it was confirmed that it was the blended tricumenyl phosphate. As described above, even if an organic phosphate ester that is not microencapsulated is blended, it does not stably exist in the composition and bleeds, which does not contribute to the improvement of the flame retardancy of silicone. confirmed.

Example 7 100 parts of polydimethylsiloxane having both ends blocked with dimethylvinylsilyl groups and having a viscosity of 3,000 cP, trimethylsiloxy units, dimethylvinylsiloxy units and SiO _4/2 units, the molar ratio of which is Is 3.5:
1.5: 5 branched polymethylvinyl siloxane 1
30 parts of fumed silica having a specific surface area of 200 m ² / g, 8 parts of rutile titanium dioxide having an average particle diameter of 3 μm, 3.0 parts of microcapsules M-3, and silicon atoms. Containing 0.9% by weight of bonded hydrogen atoms,
Viscosity 20 cP with both ends blocked by trimethylsilyl groups
3.0 parts of the linear polymethyl hydrogen siloxane of (1) was sequentially added and kneaded until uniform, to obtain a mixture. Then, as a catalyst, an isopropyl alcohol solution containing 1% by weight of chloroplatinic acid was added to the above mixture in an amount of 20 ppm as platinum atoms, kneaded and uniformly dispersed to obtain a silicone rubber having a high fluidity. A composition was prepared.

Comparative Example 5 A silicone rubber composition was prepared in the same manner as in Example 7, except that the microcapsule M-1 was not added.

Evaluation Example 4 (Addition Reaction Type Silicone Rubber) The silicone rubber compositions obtained in Example 7 and Comparative Example 5 were respectively poured into molds having a thickness of 1 mm and 2 mm and left for 24 hours, then, 60 It heated at 60 degreeC for 60 minutes, and produced the silicone rubber sheet.

The thus obtained silicone rubber sheet was tested for flame retardancy based on UL94.
The results are shown in Table 4.

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[Table 4]

Claims (2)

[Claims] 1. A flame-retardant silicone composition comprising a polyorganosiloxane as a base polymer and a microencapsulated organophosphate ester. 2. The flame-retardant silicone composition according to claim 1, which further contains magnesium hydroxide having an average crystal particle size of 1.5 μm or less.