JPH08231858A - Method of preparing flame-retardant silicone gel composition - Google Patents

Abstract

PURPOSE: To obtain a flame-retardant silicone gel composition by mixing a specified polyorganosiloxane with a specified polyorganosiloxane copolymer, a polyorganohydrogensiloxane and a platinum compound. CONSTITUTION: This composition is prepared by mixing 100 pts.wt. polyorganosiloxane (A) (wherein the content of the Si-bonded vinyl groups is 0.1-2.0 on the average per molecule, the organic groups which are other than the vinyl groups and bonded to Si atoms are monovalent hydrocarbon groups, and the viscosity is 50-100000cp) at 25 deg.C) with 0-200 pts.wt. polyorganosiloxane copolymer (B) (wherein the content of the Si-bonded vinyl groups is 2.5-10mol%, and the ratio of (R')3 SiO0.5 units to SiO2 units is 0.4-1 (wherein R' is a monovalent hydrocarbon group or vinyl group), a polyorganohydrogensiloxane (C) in such an amount that the number of the Si-bonded hydrogen atoms is 0.1 to 5.0 times as high as the total number of the Si-bonded vinyl groups of A and B, and 5-100ppm (in terms of Pt) of a platinum compound.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for preparing a flame retardant silicone gel composition.

[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 silicone gel composition which is cured by an addition reaction is widely used particularly in this field because of its characteristics such as rapid curing at room temperature or appropriate heating and no release of corrosive substances during the curing reaction. More specifically, in the electric and electronic fields, silicone gel is used for potting and encapsulating parts, especially for controlling control circuit elements such as power transistors, ICs, capacitors, etc. to protect 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, generally, in order to make the resin flame-retardant, it is known to blend an organic halogen-based flame retardant, but these have a problem that they generate a toxic gas of halogen at high temperature, It could not be applied in the case of silicone foam compositions. Therefore, the present applicant has proposed a silicone gel composition excellent in flame retardance, which contains a specific filler such as quartz as an essential component (JP-A-6-16937). Although such a silicone gel composition has excellent flame retardancy, subsequent studies have shown that silicone gels generally require a low viscosity. Problems such as sedimentation were considered, and the examples were examined only in the region where the amount of platinum added was small, and it was found that there was some difficulty in storage stability when the amount of platinum increased. Furthermore, since a filler such as quartz is an essential component,
There is also a problem that it cannot be applied to applications where the transparency of silicone gel is important.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been devised in view of the above problems of the prior art. The object of the present invention is to maintain the excellent properties of conventional silicone gels, while at the same time providing silicones excellent in flame retardancy. It is intended to provide a method for stably producing a gel composition.

[0004]

The present inventors have conducted extensive studies to obtain such a composition, and as a result, in a silicone composition, when a specific amount of a platinum compound was added to a specific silicone polymer of a specific type, the composition of a conventional silicone gel was improved. It was found that the characteristics are not impaired and the flame retardancy is excellent. In addition, in the one-component type composition, a remarkable decrease in curability due to decomposition of the crosslinking component was observed over time by adding a specific amount of the platinum compound, and in order to solve this, the crosslinking agent component It was found that the storage stability can be improved by adding a cross-linking agent component and adjusting the penetration degree after adding a part of the mixture and aging, and thus completed the present invention.

That is, according to the present invention, (A) a vinyl group bonded to a silicon atom is averaged in one molecule.
Polyesters having 0.1 to 2.0 units, the remaining organic groups 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, with or without (B) (R ') ₂ SiO unit, (R') ₃ SiO _0.5 unit and SiO ₂ unit (wherein R'does not contain aliphatic unsaturated bond 1
Represents a group selected from a valent hydrocarbon group and a vinyl group), 2.5 to 10 mol% of the silicon atom has 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 ), An amount of 0.1 to 5.0 per vinyl group bonded to the silicon atom of (B) (D) Platinum-based compound, (A), (B) and A method for preparing a flame-retardant silicone gel composition containing an amount of 5 ppm or more and 100 ppm or less based on the total amount of (C), wherein the total amount of (A) component and (B) component optionally blended. Alternatively, add a part of the (C) component in the coexistence with a part of the (D) component, and after aging treatment for 15 minutes to 24 hours at a temperature of 30 ° C or higher and 100 ° C or lower, while adjusting the penetration, the (C) component Is additionally added, which is a method for preparing a flame-retardant silicone gel composition.

First, each component constituting the present invention will be described below. The component (A), the polyorganosiloxane, has an average of 0.1 to 2.0 vinyl groups bonded to silicon atoms per molecule. When the amount of vinyl groups is less than 0.1, the amount of polyorganosiloxane that does not crosslink is increased, and the physical properties of the gelled product obtained by curing and the adhesiveness to the substrate are significantly reduced. If the amount of vinyl groups is more than 2.0, the softness of silicone gel cannot be exhibited. The remaining organic groups other than the vinyl group bonded to the silicon atom of the polyorganosiloxane of (A) are substituted or unsubstituted monovalent hydrocarbon groups containing no aliphatic unsaturated bond, and specifically, methyl groups. Group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, octyl group, decyl group, alkyl group such as dodecyl group, aryl group such as phenyl group, β-phenylethyl group, β-phenylpropyl group An aralkyl group such as and a chloromethyl group,
Substituted hydrocarbon groups such as cyanoethyl group and 3,3,3-trifluoropropyl group are exemplified, but they are easy to synthesize, easy to handle in an uncured state, and heat resistance and physical properties of gels. From the standpoint of physical properties, a methyl group is preferable. 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. The viscosity is selected from the range of 50 to 100,000 cP, preferably 100 to 5,000 cP at 25 ° C. 100 when used for potting
Most preferred is a range of up to 1,500 cP. If it is lower than 50 cP, it easily flows and the physical properties after the reaction are poor. Again 100,00
If it exceeds 0cP, the workability will deteriorate. The siloxane skeleton of the polyorganosiloxane (A) may be linear or branched, or may be a mixture of both, but it is easy to synthesize,
From the viewpoint of imparting appropriate softness to the gel-like material, it is preferably substantially linear. There is no problem even if a small amount of cyclic polyorganosiloxane coexists, but even if it has a vinyl group bonded to a silicon atom, the reactivity is low,
It 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 a polyorganosiloxane (A) requires, for example, a vinyl group-containing polyorganosiloxane having vinyl groups bonded to silicon atoms at both ends and a linear or branched polyorganosiloxane containing no vinyl group. If present, it is blended together with a polydiorganosiloxane not containing vinyl group so as to satisfy the above-mentioned viscosity range and the average molecular weight and the amount of the vinyl group, and an acid catalyst such as sulfuric acid, hydrochloric acid or activated clay, or potassium hydroxide. In the presence of an alkali catalyst such as tetramethylammonium hydroxide, siloxane is cleaved and equilibrated by a conventional method. in this case,
A cyclic polysiloxane, particularly 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 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. The silicon-bonded vinyl groups should be present in an amount equal to 2.5 to 10.0 mol% of silicon atoms in the copolymer component (B), regardless of where they are located in the copolymer. Copolymer component (B) is a solid resinous material, often produced as a solute 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 component (B) is 0 to 200 parts by weight, preferably 10 to 80 parts by weight, relative to 100 parts by weight of 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), it undergoes an addition reaction with the vinyl groups of the components (A) and (B) to form a gel. The polyorganohydrogensiloxane as the component (C) forms a network structure, so that the number of hydrogen atoms bonded to silicon atoms must be more than 2 on average in one molecule. Such a hydrogen atom in the component (C) may be bonded to any silicon atom at the terminal of the molecule or in the middle of the molecule. Examples of the organic group which can be bonded to the silicon atom of the component (C) include the same organic groups as those other than the vinyl group among the organic groups which can be bonded to the silicon atom of (A) and (B). The methyl group is preferred because of its ease of synthesis, heat resistance, and physical properties.
The siloxane skeleton may be linear, branched, cyclic or network. Although the viscosity of the component (C) is not particularly limited, it is preferably 10,000 cp or less in terms of workability and easiness of synthesis. The blending amount of the component (C) is the sum of the number of hydrogen atoms bonded to the silicon atom in the component (C) (hydrogen atom) to one vinyl group bonded to the silicon atom in the components (A) and (B). / Vinyl group)
Is 0.1 to 5.0, preferably 0.1 to 2.0. Further, as the component (C), in addition to the polyorganohydrogen siloxane (hereinafter referred to as (C-1)) in which the number of hydrogen atoms bonded to the silicon atom is more than 2 in one molecule on average, it is further directly reticulated. The average number of hydrogen atoms that can be bonded to silicon atoms in a molecule is 1
You may use together the polyorgano hydrogen siloxane controlled to 0.1-2 (henceforth (C-2)). When using component (A) with a relatively low degree of polymerization, (C-2)
By using 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
It is a component for promoting the addition reaction between the vinyl group of the components (A) and (B) and the hydrosilyl group of the component (C) and for imparting flame retardancy. Platinum compounds exemplified by alcohol-modified chloroplatinic acid, chloroplatinic acid, platinum-olefin complexes, platinum-ketone complexes, platinum-vinylsiloxane, platinum-phosphorus compounds, and the like.
The amount of platinum added is 5 ppm to 100 ppm as platinum based on the total amount of the components (A), (B) and (C), and there is no problem even if one kind or a mixture of two or more kinds is added. If it is less than 5 ppm, the flame retardance is poor, and if it is 100 ppm or more, not only the contribution to the flame retardancy is not increased, but also the transparency of the gel composition is remarkably lowered, and it cannot be used for applications requiring transparency.

When a large amount of platinum is contained, the action of eliminating the silicon-bonded hydrogen atom of polyorganohydrogensiloxane becomes remarkable. Further, even if the amount of platinum added is between 5 ppm and 100 ppm, if it is of a one-component type, the hydride cleavage reaction in the system will proceed and the silicone gel will not harden with time or the penetration will be remarkable. The phenomenon that it grows is confirmed. Therefore, in the present invention, the component (A) and optionally blended
The present invention is characterized in that a part of the component (C) is added in the coexistence of the component (B) and the component (D), and after aging treatment, the component (C) is additionally added while adjusting the penetration. More preferably here,
After adding a part of the component (D) to the total amount or part of the component (A) and optionally the component (B) and the component (D), the siloxane containing the hydride of the component (C) is added. Add a portion of the mixture and age it at a temperature of 30 ° C or higher and 100 ° C or lower for 15 minutes to 24 hours, then add the rest of the component (D) and
It is a method of adjusting the penetration with the component (C). The following is a summary of the above manufacturing method.
The following method is merely an example and does not limit the scope of the present invention.

[0011]

[Table 1]

Further, in order to suppress the reaction in the above composition, it is possible to add an acetylene-based inhibitor, an amine-based inhibitor, a carboxylic acid ester-based inhibitor or the like. Further, silica powder, carbon, metal oxide, etc. may be added as long as the characteristics of the present invention are not impaired.

[0013]

As described above, according to the method for preparing a flame-retardant silicone gel composition of the present invention, a silicone gel excellent in flame retardancy can be obtained, and in the case where a one-component composition is prepared. It is possible to provide a silicone gel composition that does not impair storage stability. 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 sealant such as a filter, etc. can get.

[0014]

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. Me and Vi represent a methyl group and a vinyl group, respectively. The materials described below were uniformly mixed according to the formulation shown in Table 2 to prepare the compositions of Examples and Comparative Examples, and the penetration and flame retardancy were evaluated. The penetration was measured using an ASTM D1403 1/4 cone consistency meter. The flame retardancy is measured by heating and curing the silicone gel composition to obtain a silicone gel molded product (20 mmφ,
2mm thick) is used as a test piece, which is fixed vertically without wind, and the lower end of the test piece slightly contacts the upper part of the inner flame of the Bunsen burner blue flame (internal flame 9.5mm, height 19mm). A flame was applied for 10 seconds to ignite, then the Bunsen burner was moved away, and the time (seconds) until quenching was measured. Here, the flame contact test was performed twice for each of the five test pieces, and the total
The flame retardancy data was obtained by summing 10 times (seconds). Polysiloxane I as component (A) I average formula

[0015]

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Polydimethylsiloxane containing a vinyl group represented by: Viscosity 400cP (A) Polysiloxane II as component

[0017]

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Polydimethylsiloxane containing vinyl group represented by: Viscosity 300 cP (A) Polysiloxane III as an average component

[0019]

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Polydimethylsiloxane containing vinyl group represented by: Viscosity 800 cP (B) 60 mol% SiO ₂ unit 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 a molecule as a component to bond with silicon atom Viscosity 30cP (C-1) ( C) as an ingredient

[0021]

[Chemical 4]

Polymethylhydrogensiloxane represented by: Viscosity 18 cP (C-2) (D) Platinum-1 as a component; obtained by heating chloroplatinic acid and tetramethyltetravinylcyclotetrasiloxane. Platinum content 1.8% by weight Platinum-2; Reaction product of chloroplatinic acid and tetrakistriphenylphosphite. Platinum content 6.0% by weight In addition, regarding the one-component type product form, since it is preferable to add a reaction inhibitor, 1-ethynyl-1
-Add cyclohexanol.

Example 1 To 100 parts by weight of the polysiloxane (I) as the component (A), 0.05 part by weight (10 ppm) of the platinum catalyst (D-1) as the component (D) and 0.05 part by weight of (D-2) ( 30 ppm) and 1-ethynyl-1-cyclohexanol (0.02 parts by weight) were added, and the mixture was thoroughly stirred. To this preparation
Add 5 parts by weight of component (C-2), then add (C-1) to 0.5.
Parts by weight were added, and the mixture was heated and stirred at 80 ° C / 2h. After cooling this preparation to room temperature, 0.3 part by weight of the component (C-1) was added so that the penetration was 50. The compounding amount of this composition and the evaluation results are shown in Table 2. Example 2 A composition was prepared in the same manner as in Example 1 except that the heating and stirring were changed to 30 ° C./24 h. Example 3 A composition was prepared in the same manner as in Example 1 except that heating and stirring were changed to 100 ° C./30 minutes. Example 4 100 parts by weight of the component (A) polysiloxane (II) to 12 parts by weight of the copolymer of the component (B), 0.05 parts by weight (10 ppm) of the platinum catalyst (D-1) of the component (D), D-2) 0.05 part by weight (30 ppm) and 1-
After adding 0.02 part by weight of ethynyl-1-cyclohexanol, the mixture was thoroughly stirred. Add (C-2) of component (C) to this preparation.
80 parts by weight (C-1) 0.4 parts by weight
The mixture was heated and stirred for h. After cooling the preparation to room temperature,
0.1 part by weight of component (C-1) was added so that the penetration was 50. The compounding amount of this composition and the evaluation results are shown in Table 2. Example 5 To 50 parts by weight of the polysiloxane (I) as the component (A) and 50 parts by weight of the polysiloxane (III), 0.25 parts of the platinum catalyst (D-1) as the component (D) was added.
Parts by weight (50 ppm), (D-2) 0.05 parts by weight (30 ppm) and 1
-Ethynyl-1-cyclohexanol was added in an amount of 0.02 part by weight and then sufficiently stirred. Add (C-1) of component (C) to this preparation.
Two parts by weight were added, and the mixture was heated and stirred at 80 ° C / 2h. After cooling this preparation to room temperature, adjust the penetration to 50 (C-1).
0.8 parts by weight of the ingredients were added. The compounding amount of this composition and the evaluation results are shown in Table 2. Comparative Examples 1 and 2 Compositions were prepared in the same manner as in Example 1 except that the type and blending amount of each component were changed as shown in Table 2. The compounding amount of this composition and the evaluation results are shown in Table 2.

[0024]

[Table 2]

Comparative Example 3 A composition was prepared in the same manner as in Example 1 except that the heating and stirring step was omitted. That is, 100 parts by weight of the component (A) polysiloxane (I), 0.05 parts by weight (10 ppm) of the platinum catalyst (D-1) of the component (D), and 0.05 parts by weight (30 ppm) of (D-2) and 1 −
After 0.02 part by weight of ethynyl-1-cyclohexanol was added, the mixture was thoroughly stirred, and then 5 parts by weight of component (C-2) (C) and 0.8 part by weight of (C-2) were added to this preparation. When this composition was cured at 150 ° C./1 h, the penetration was 53.
This composition was aged at 50 ℃ / 24h, then at 150 ℃
It was cured under the condition of / 1h, but the penetration was increased to 85, and it was confirmed that the curability was significantly lowered.

Claims (1)

[Claims] 1. (A) A substituted or non-substituted vinyl group bonded to a silicon atom is present on average in an amount of 0.1 to 2.0, 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 50 at 25 ° C.
100000 cP polyorganosiloxane, 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 the silicon atom has 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 ), An amount of 0.1 to 5.0 per vinyl group bonded to the silicon atom of (B) (D) Platinum-based compound, (A), (B) and A method for preparing a flame-retardant silicone gel composition containing an amount of 5 ppm or more and 100 ppm or less based on the total amount of (C), wherein the total amount of (A) component and (B) component optionally blended. Alternatively, add a part of the (C) component in the coexistence with a part of the (D) component, and after aging treatment for 15 minutes to 24 hours at a temperature of 30 ° C or higher and 100 ° C or lower, while adjusting the penetration, the (C) component A method for preparing a flame-retardant silicone gel composition, characterized in that: