JPH06293862A - Flame retardant silicone gel composition and its cured product - Google Patents

Abstract

PURPOSE:To obtain the subject composition, comprising an organo(hydrogen) siloxane (co)polymer, a metallic catalyst and cerium compound, capable of maintaining heat resistance, moistureproofness, electrical insulating properties, etc., excellent in flame retardancy and useful for sealing electronic parts, etc. CONSTITUTION:This silicone gel composition comprises (A) 100 pts.wt. polyorganosiloxane having 50-100000cP viscosity at 25 deg.C and vinyl group bound to silicon, (B) 0-200 pts.wt. polyorganosiloxane copolymer, composed of units expressed by the formulas (R')2SiO [R' is monovalent hydrocarbon, etc.], (R')3SiO1/2 and SiO2 and having vinyl group bound to silicon, (C) an organohydrogensiloxane in an amount so as to obtain 0.1-5.0 sum total of hydrogen atoms bound to silicon atom based on one vinyl group bound to the silicon, (D) a platinum-based, a palladium-based or rhodium-based catalyst in an amount of 0.01-100ppm based on the components (A), (B) and (C) expressed in teams of a metallic element and (E) cerium acetylacetate, cerium octylate or cerium hydroxide.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a flame-retardant silicone gel composition and a cured product thereof.

[0002]

TECHNICAL BACKGROUND AND PROBLEMS OF THE INVENTION Silicone gel is
It has excellent properties such as electrical insulation, heat resistance, moisture resistance, electrical properties, stability, and flexibility, so it can be used as a coating agent or potting agent in the fields of electrical and electronic fields, optical and optoelectronics, and sensors. Widely used. Furthermore, it has been used as a sealing material for filters in the field of construction. Among them, the silicol gel composition which is cured by an addition reaction is widely used particularly in this field because of its characteristics such that it cures rapidly at room temperature or appropriate heating, and no corrosive substance is released during the curing reaction. More specifically, in the electrical and electronic fields, Silicol gel coats control circuit elements such as power transistors, ICs and capacitors for potting and encapsulating parts, and protects them from thermal and mechanical damage. It is used as a coating material for By the way, in recent years, these components are becoming smaller and larger in capacity. Along with this, the load applied to these electric and electronic parts is also increasing, and when an excessive load is applied, there is a problem that ignition and combustion of parts are likely to occur due to energization of a large capacity. Further, even in the case of being used in the field of construction, fireproof / flame retardant materials are desired. However, at present, almost no gel-like silicone composition capable of addressing such a problem has been provided. That is, in general, silicone gel has a drawback that it has many crosslinking points and is inherently easy to burn as compared with other cured products. Here, conventionally, in order to make the resin flame-retardant, it is known to mix an organic halogen-based flame retardant,
Since these have a problem that they generate a toxic gas of halogen at a high temperature, they cannot be applied in the case of a gel silicone composition. On the other hand, Japanese Patent Application Laid-Open No. 54-146897 discloses a technique of adding a cerium compound for the purpose of imparting flame retardancy to an addition reaction type composition. However, this forms a rubber film by curing,
In the composition which hardens into a gel, the optimum compounding amount and the like cannot be directly applied. In order to solve the above problems, the inventor of the present invention has an appropriate amount of one or more inorganic fillers selected from crushed quartz, metal carbonates such as zinc carbonate and calcium carbonate, and carbon black in a composition that hardens to form a gel. It was found that excellent flame retardancy can be imparted by compounding an agent and applied for a patent (Japanese Patent Application No. 4-173292).
issue). However, according to this method, since a powder having a large specific gravity or a black powder such as carbon black is used, it becomes unsuitable depending on the place of use, and further measures have been required.

[0003]

OBJECT OF THE INVENTION It is an object of the present invention to provide a silicone gel composition which maintains the excellent properties of conventional silicone gels and is also excellent in flame retardancy.

[0004]

The present inventor has conducted extensive studies to obtain such a composition, and as a result, in the silicone gel composition,
A specific silicone composition containing a specific amount of a specific cerium compound does not impair the characteristics of conventional silicone gels,
Moreover, they have found that they have excellent flame retardancy, and have reached the present invention. In the present invention, (A) a vinyl group bonded to a silicon atom is averaged in one molecule.
Polyesters having 0.1 to 10 residues, the remaining organic groups to be bonded to silicon atoms are substituted or unsubstituted monovalent hydrocarbon groups containing no aliphatic unsaturated bond, and having a viscosity at 25 ° C of 50 to 100,000 cP. Organosiloxane, 100 parts by weight (B) with or without (R ′) ₂ SiO unit, (R ′) ₃ SiO _0.5 unit and SiO ₂ unit (wherein R ′ does not contain an aliphatic unsaturated bond 1
Represents a group selected from a valent hydrocarbon group and a vinyl group), 2.5 to 10 mol% of silicon atoms have a vinyl group directly bonded to the silicon atom, (R ') ₃ SiO _0.5 unit: SiO ₂ Polyorganosiloxane copolymer having a unit ratio of 0.4: 1 to 1: 1, 0 to 200 parts by weight (C) An average of 2 hydrogen atoms bonded to silicon atoms in one molecule.
More than 1, and the remaining organic groups bonded to silicon atoms are substituted or unsubstituted monovalent hydrocarbon groups, polyorganohydrogensiloxane, the sum of the number of hydrogen atoms bonded to silicon atoms is (A ), (B) 0.1 to 5.0 per vinyl group bonded to the silicon atom (D) A catalyst selected from the group consisting of platinum-based catalysts, palladium-based catalysts and rhodium-based catalysts, (A) , (B), an amount of 0.01 to 100 ppm as the amount of catalytic metal element relative to the total amount of (C) (E) cerium acetyl acetate or cerium octylate; 0.001 to 0.7 parts by weight in terms of metallic cerium,
And / or cerium oxide or cerium hydroxide; a flame-retardant silicone gel composition containing 0.005 to 5 parts by weight in terms of metal cerium.

Each component of the present invention will be described below. (A)
The component polyorganosiloxane contains an average of 0.1 to 10 vinyl groups bonded to silicon atoms in one molecule. If the amount of vinyl groups is less than 0.1, the amount of polyorganoshirosaquine that does not participate in crosslinking will increase, and the physical properties of the gel product obtained by curing and the adhesiveness to the substrate will significantly decrease. . If the amount of vinyl groups is more than 10, the softness of silicone gel cannot be exhibited. The remaining organic groups other than the vinyl group bonded to the silicon atom of the polyorganoshirosaquine (A) are substituted or unsubstituted monovalent hydrocarbon groups containing no aliphatic unsaturated bond, and specifically, Is a methyl group, ethyl group, propyl group, butyl group, amino group, hexyl group, octyl group, decyl group, alkyl group such as dodecyl group, aryl group such as phenyl group, β
An aralkyl group such as a phenylethyl group and a β-phenylpropyl group, and a chloromethyl group, a cyanoethyl group,
Substituted hydrocarbon groups such as 3,3,3-trifluoropropyl group are exemplified, but they are easy to synthesize, easy to handle in an uncured state, and heat-resistant and physical properties of the gel. It is preferably a methyl group. When cold resistance is required, up to 8 mol% of all organic groups, and when particularly high heat resistance, radiation resistance or high refractive index is required, up to 50 mol% of phenyl groups in all organic groups. It is recommended to introduce. Viscosity is 50-100,000cP at 25 ℃
, Preferably selected from the range of 100 to 5,000 cP. When used for potting, the range of 100-1,500 cP is most preferred. If it is lower than 50 cP, it easily flows and the physical properties after the reaction are poor. If it exceeds 100,000cP, the workability will deteriorate. The siloxane skeleton of the polyorganosiloxane (A) may be linear or branched, or may be a mixture of the two, but it is substantially synthesized because it is easy to synthesize and gives a gel-like material with appropriate softness. It is preferably linear. A small amount of cyclic polyorganosiloxane may coexist, but even if it has a vinyl group bonded to a silicon atom, it has low reactivity and does not contribute to the formation of a sticky gel. The vinyl group in the polyorganosiloxane may be bonded to either a silicon atom in the middle of the molecule or a terminal silicon atom, but it is bonded to the terminal silicon atom due to the reaction rate and the effect of forming a gel by the reaction. It is preferable. Such polyorganosiloxane (A) is, for example, a vinyl group-containing polyorganosiloxane having a vinyl group bonded to a silicon atom at both ends,
A linear or branched polyorganosiloxane that does not contain a vinyl group is used together with a polydiorganosiloxane that does not contain a vinyl group so that the average molecular weight and the amount of the vinyl group that achieve the above-mentioned viscosity range are satisfied. Blended, sulfuric acid,
It is synthesized by cleaving and equilibrating siloxane by a conventional method in the presence of an acid catalyst such as hydrochloric acid or activated clay, or an alkali catalyst such as potassium hydroxide or tetramethylammonium hydroxide. In this case, a cyclic polysiloxane, especially a cyclic polysiloxane containing no vinyl group, may be used in combination as a part of the raw material. After equilibration, the catalyst is removed by a conventional method, and the mixture is heated under reduced pressure to remove by-produced or unreacted low molecular weight polyorganosiloxane for purification.

The polyorganosiloxane copolymer of the component (B) in the present invention is a component for imparting sufficient strength to the composition without containing a reinforcing filler and does not contain an aliphatic unsaturated bond. Monovalent hydrocarbon group or vinyl group
It is a polyorganosiloxane copolymer having R'groups and at least the above-mentioned ratio of R'groups is a vinyl group. Non-vinyl R'groups are within the same range as the R groups of component (A) and similar groups, and a preferred embodiment thereof is that all monovalent hydrocarbon groups containing no aliphatic unsaturation are methyl. This is the case of the base. The vinyl group can be present as part of the (R ′) ₃ SiO _0.5 group, or as part of the (R ′) ₂ SiO group, or both. The various siloxane units in the copolymer component (B) are (R ') ₃ SiO _0.5
The unit: SiO ₂ unit ratio is chosen to be between 0.4: 1 and 1: 1. If the ratio of (R ') ₃ SiO _0.5 units is less than 0.4, the composition is
The stability of (B) is poor and it is difficult to synthesize it with good control. If it exceeds 1, good mechanical strength cannot be given to the cured product. The (R ') ₂ SiO units are present in an amount equal to 0 to 10 mol% based on the total number of siloxane units in the copolymer. Regardless of where the silicon-bonded vinyl groups are located in the copolymer, the silicon-bonded vinyl groups should be present in an amount equal to 2.5 to 10.0 mol% of the copolymer component (B). The copolymer component (B) is a solid resinous material, often prepared as a solvent in a solvent such as xylene or toluene, and generally as a 30-75 wt% solution. To facilitate the handling of the composition, this solution of the copolymer component (B) is usually dissolved in part or all of the vinyl chain end polysiloxane component (A), and the solvent is distilled off from the resulting solution. Then, a mixture of the component (A) and the copolymer component (B) may be prepared, or the component (B) from which the solvent has been removed beforehand may be used. The amount of the component (B) is 0 to 200 parts by weight based on 100 parts by weight of the component (A).

The polyorganohydrogensiloxane as the component (C) in the present invention acts as a crosslinking agent. That is, the hydrogen atom bonded to the silicon atom of component (C) is
In the presence of the catalyst of the component (D), the vinyl group of the components (A) and (B) undergoes an addition reaction to form a gel. Component (C), the polyorganohydrogensiloxane, forms a network structure, so the number of hydrogen atoms bonded to silicon atoms is 2 on average in one molecule.
There must be more than one. Such a hydrogen atom in the component (C) may be bonded to any silicon atom in the middle of the molecule terminal molecule. The organic group that can be bonded to the silicon atom of the component (C) is the same as the organic groups that are bonded to the silicon atom of (A) and (B) other than the vinyl group. However, a methyl group is preferable from the viewpoint of easy synthesis, heat resistance and physical properties. The siloxane skeleton may be linear, branched, cyclic or network. The viscosity of the component (C) is not particularly limited, but it is 10000 cp because of workability and ease of synthesis.
The following are preferred. The blending amount of the component (C) is such that the sum of the number of hydrogen atoms bonded to the silicon atom in the component (C) is 0.1 to 1 vinyl group bonded to the silicon atom in the components (A) and (B). 5.0
The number is preferably 0.1 to 2.0.

Further, as the component (C), a polyorganohydrogensiloxane (hereinafter, referred to as (C-
1)) and polyorganohydrogensiloxane in which the number of hydrogen atoms bonded to silicon atoms is controlled to be 0.1 to 2 on average in one molecule (hereinafter, (( (C-2)) may be used together. When using component (A) with a relatively low degree of polymerization,
By using (C-2) together, the flexibility of the silicone gel can be maintained. Here, even when (C-2) is used in combination, the total amount with (C-1) must satisfy the above range.

The component (D) catalyst used in the present invention is
(A), for promoting the addition reaction between the vinyl group of the component (B) and the hydrosilyl group of the component (C), chloroplatinic acid,
Platinum catalysts exemplified by alcohol-modified chloroplatinic acid, platinum-olefin complexes, platinum-ketone complexes, platinum-vinylsiloxane complexes, tetrakis (triphenylphosphine) palladium, palladium black and triphenyl. Palladium-based catalysts such as a mixture with phosphine or rhodium-based catalysts can be used, but platinum-based catalysts are preferred because of their catalytic effect and ease of handling. The blending amount of the component (D) is such that the amount of the catalytic metal element is in the range of 0.01 to 100 ppm, preferably 1 to 30 ppm, based on the total amount of (A), (B) and (C). .

The cerium compound as the component (E) in the present invention imparts flame retardancy to the silicone gel composition comprising (A) to (D). As such, cerium acetyl acetate, cerium oxide, cerium octylate and cerium hydroxide can be selectively mentioned. The reason is that these are physically and chemically stable among cerium compounds and are easy to handle. In addition, the amount added is also important, in terms of metallic cerium (A)
Cerium acetyl acetate or cerium octylate; 0.001 to 0.7 parts by weight, and / or cerium oxide or cerium hydroxide; 0.005 per 100 parts by weight of the component
~ 5 parts by weight. If the amount is less than the lower limit, flame retardancy cannot be imparted, and if the amount exceeds the upper limit, the flame retardancy and the gel properties are adversely affected.

The composition of the present invention may further contain a reinforcing filler such as fumed silica, precipitated silica, silica airgel, pyrogenic silica, fumed titanium oxide,
In a single container, a acetylene-based compound, an amine compound, diallyl maleate, triallyl isocyanurate, a coexistence of a reaction inhibitor such as a nitrile compound or an organic peroxide, or a platinum-based catalyst having low activity at room temperature can be used. Alternatively, the components including the component (C) and the component (D) may be separately stored, and both components may be uniformly mixed immediately before use.

[0012]

EFFECTS OF THE INVENTION According to the flame-retardant silicone gel composition of the present invention described above, a gel cured product having excellent flame retardancy can be obtained. Therefore, by forming the flame-retardant gel cured product of the present invention on the surface of electric, electronic parts, semiconductor elements, etc., and by forming it on a sealing agent such as a filter, etc., it does not burn even if it ignites. Lei parts are obtained. Further, although high transparency may be required depending on the use of the silicone gel, the flame-retardant silicone gel composition of the present invention has appropriate transparency.

[0013]

EXAMPLES Examples of the present invention will be shown below. In the examples, "parts" means "parts by weight", and "viscosity" means viscosity at 25 ° C. The symbols Me and Vi represent a methyl group and a vinyl group, respectively. Examples 1 to 11 and Comparative Examples 1 to 7 The materials described below were uniformly mixed according to the formulations shown in Tables 1 and 2 to prepare the compositions of Examples 1 to 11 and Comparative Examples 1 to 7, The penetration and flame retardancy were evaluated. Penetration is measured by AS
Performed using a TM D 1403 1/4 cone consistency meter. The flame retardancy was measured by setting a silicone gel molded product (100 mm x 10 mm x 2 mm) obtained by heating and curing a silicone gel composition as a test piece, and fixing it vertically without wind, and the lower end of the test piece Bunsen burner blue flame (internal flame 9.5 mm, height 19 mm)
The flame was ignited by applying a flame for 10 seconds at a position slightly in contact with the upper part of the internal flame, and the time (seconds) until quenching was measured. The results are shown in Tables 1 and 2. Polysiloxane I as the component (A) I average formula

[0014]

[Chemical 1]

Polydimethylsiloxane containing vinyl group represented by: Viscosity 800cP (A) Polysiloxane II as a component Average formula

[0016]

[Chemical 2]

Vinyl group-containing polydimethylsiloxane represented by: Viscosity 1000 cP (B) 60 mol% SiO ₂ units as component, 37.2 mol% Me ₃ S
Copolymer consisting of _0.5 units of iO and 2.8 mol% MeViSiO ₂ unit (C) Polymethylhydrogensiloxane having 8 hydrogen atoms in one molecule that can be bonded to silicon atom as component (C) Component to be used in combination with viscosity 30 cP As

[0018]

[Chemical 3]

Polymethylhydrogen siloxane represented by: Viscosity 18 cP (D) as component Platinum-1: one obtained by heating chloroplatinic acid and tetramethyltetravinylcyclotetrasiloxane. Platinum content: 2.0% by weight of platinum (E) As a component, cerium acetylacetate, cerium oxide, cerium octylate, and cerium hydroxide (the compounding amounts in the table are values converted to metallic cerium).

[0020]

[Table 1]

[0021]

[Table 2]

Claims (2)

[Claims] 1. A substituted or unsubstituted (A) silicon atom-bonded vinyl group is present on average in an amount of 0.1 to 10 and the remaining organic group bonded to the silicon atom does not contain an aliphatic unsaturated bond. Is a monovalent hydrocarbon group having a viscosity of 50 to 10 at 25 ° C.
Polyorganosiloxane of 0000 cP, 100 parts by weight (B) with or without (R ') ₂ SiO unit, (R') ₃ SiO _0.5 unit and SiO ₂ unit (wherein R'is an aliphatic unsaturated bond) Does not contain 1
Represents a group selected from a valent hydrocarbon group and a vinyl group), 2.5 to 10 mol% of silicon atoms have a vinyl group directly bonded to the silicon atom, (R ') ₃ SiO _0.5 unit: SiO ₂ Polyorganosiloxane copolymer having a unit ratio of 0.4: 1 to 1: 1, 0 to 200 parts by weight (C) An average of 2 hydrogen atoms bonded to silicon atoms in one molecule.
More than 1, and the remaining organic groups bonded to silicon atoms are substituted or unsubstituted monovalent hydrocarbon groups, polyorganohydrogensiloxane, the sum of the number of hydrogen atoms bonded to silicon atoms is (A ), (B) 0.1 to 5.0 per vinyl group bonded to the silicon atom (D) A catalyst selected from the group consisting of platinum-based catalysts, palladium-based catalysts and rhodium-based catalysts, (A) , (B), an amount of 0.01 to 100 ppm as the amount of catalytic metal element relative to the total amount of (C) (E) cerium acetyl acetate or cerium octylate; 0.001 to 0.7 parts by weight in terms of metallic cerium,
And / or cerium oxide or cerium hydroxide; a flame-retardant silicone gel composition containing 0.005 to 5 parts by weight in terms of metallic cerium. 2. A cured product obtained by curing the flame-retardant silicone gel composition according to claim 1.