JP2000129127A - Porous silica-silicone composite material and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composite material having high insulating effect, capable of manifesting excellent mechanical characteristics by drying a gelatinized product of an alkoxide of silicon or a derivative thereof, with a polyalkylsiloxane derivative. SOLUTION: A gelatinized product of (A) an alkoxide of silicon or a derivative thereof, with (B) a polyalkylsiloxane derivative is dried to provide the objective composite material. The composite material preferably comprises 30-99 pts.wt. component A and 1-70 pts.wt. component B. The composite material preferably has 0.01-0.5 g/cm3 bulk density. The composite material is obtained by adding the component B to a diluted solution of the component A, adding water to the obtained mixture to hydrolyze the components, dipping the wet gel formed by the hydrolysis into an organic solvent to age the gel, and drying the aged gel. As a result, the composite material is expected to have insulation properties the same as that of an aerogel, further to have flexibility superior to the aerogel, to be excellent in processability and to provide an insulating material having good operability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous silica / silicone composite which can be used as a heat insulating material, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a silica-based heat insulating material, a fibrous porous body or a porous body formed of silica-based particles has been mainly used. Silica-based fibrous porous materials are particularly suitable for high-temperature heat insulating materials and houses because of their relatively low thermal conductivity, flexibility, high heat resistance, relatively low cost, and good workability. Widely used as a sound-absorbing heat insulating material for building materials such as buildings. Further, porous silica-based particles have been used as furnace materials because of their high strength and high heat resistance. However, these conventional porous bodies also have drawbacks such as dust being generated and being harmful to the human body, and having a higher thermal conductivity near room temperature than plastic foam insulation materials.

On the other hand, in recent years, a material called aerogel has been developed as a new type of heat insulating material. Airgel is a method of hydrolyzing, polymerizing, or the like a metal alkoxide or halide, or an organic compound to form an alcogel, and replacing the organic phase in the alcogel with a solvent such as alcohol or carbon dioxide gas. A substance obtained by extracting a solvent in a supercritical state and being a porous body having an aggregate of fine particles as a skeleton.
Airgel production methods were described in the early 1930s by S.A. S.
It was first reported in Nature by Kistler. Kistler produced aerogels by adding hydrochloric acid to an aqueous solution of sodium silicate to cause gelation, washing this with water and alcohol, and removing the alcohol in a supercritical state. This method took several weeks to manufacture, but in the early 1960s S.M. J. Teshne et al. Reported a method for producing an alcogel by hydrolyzing tetramethoxysilane, and the production time was greatly reduced. Then A. J. Hunt et al. Reported a method using tetraethoxysilane instead of toxic tetramethoxysilane, and a method using carbon dioxide gas instead of explosive alcohol during supercritical drying. This airgel is known as a new heat insulating material having characteristics such as thermal conductivity similar to that of plastic foam, light weight, nonflammability, no generation of dust, and light transmissivity.

[0004]

However, aerogels have problems such as brittleness, poor workability, and high manufacturing cost, and have not been widely used. Airgel is brittle because the porosity is as high as 90% or more and the solid content is low, the bond of -O-Si-O- that forms the skeleton of the aerogel is amorphous and relatively weak, and -O-Si Because the -O- bond has a three-dimensional structure, the lattice is strongly restrained and the flexibility is low.

The present invention has been made in view of the above circumstances, and has as its object to provide a porous silica-silicone composite material having not only a high heat insulating effect but also excellent mechanical properties. .

[0006]

In order to achieve the above-mentioned object, the present invention provides a porous material obtained by drying a gelled product of an alkoxide of silicon or a derivative thereof and a polyalkylsiloxane derivative. Provide a porous silica-silicone composite. The present invention also provides a method for producing a porous silica / silicone composite material, which comprises gelling and drying a silicon alkoxide or a derivative thereof and a polyalkylsiloxane derivative.

[0007] The porous silica-silicone composite material comprises:
Flexible silicone is compounded in the skeleton of silica.It has the same heat insulation performance as airgel, and has much better mechanical properties than airgel. Excellent.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
I do. The porous silica-silicone composite material of the present invention is
Alkoxide or derivative thereof and polyalkylsilo
A xan derivative is used as a starting material. Alkoxide of silicon
Is represented by the general formula Si (OR¹)_Four(R¹Is an alkyl group)
Derivatives of the general formula R^TwoSi (OR¹)_ThreeOr R^TwoR^ThreeS
i (OR¹)_TwoOr R^TwoR^ThreeR^FourSiOR ¹(R^Two, R^Three, R^FourIs German
Alkyl groups, vinyl groups, epoxy groups, amino groups,
Kuryl group, methacryloxy group, chloropropyl group, mel
Displays capto group, isocyanate group, halogen atom, etc.
The compound represented by formula (1) can be suitably used.
Such silicon alkoxides include, for example, tetra
Methoxysilane, tetraethoxysilane, etc.
Conductors include vinyltrimethoxysilane and vinyltrie
Toxic silane, vinyl tris (β-methoxyethoxy)
Orchid, β- (3,4 epoxycyclohexyl) ethyltrime
Toxysilane, γ-glycidoxypropyltrimethoxy
Silane, γ-glycidoxypropylmethyldiethoxy
Orchid, γ-methacryloxypropyltrimethoxysila
Γ-methacryloxypropyltriethoxysilane,
γ-methacryloxypropylmethyldimethoxysilane,
γ-methacryloxypropylmethyldiethoxysilane, N
-β (aminoethyl) γ-aminopropylmethyl dimethoxy
Sisilane, N-β (aminoethyl) γ-aminopropyl
Limethoxysilane, N-β (aminoethyl) γ-aminop
Ropirtriethoxysilane, γ-aminopropyltrime
Toxysilane, γ-aminopropyltriethoxysila
, N-phenyl-γ-aminopropyltrimethoxysila
, Γ-chloropropyltrimethoxysilane, γ-merca
Ptopropyltrimethoxysilane, γ-isocyanate
And propyltriethoxysilane. Also,
These silicon alkoxides and derivatives thereof are hydrophilic.
Used after dilution with an organic solvent. Hydrophilic used at that time
Organic solvents such as methanol, ethanol,
Alcohols such as pananol and butanol, and tetrahydrides
Lofuran, dioxane and the like are preferred.

On the other hand, as the polyalkylsiloxane derivative, a compound represented by the general formula R ⁵ [R ⁶ R ⁷ SiO] _n SiR ⁸ (R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represents an alkyl group, a hydroxyl group, an epoxy group, Amino group, mercapto group, carboxyl group, carbinol group,
A compound represented by a methacryl group, a phenol group, an alkoxy group, a polyether group, a halogen atom, and the like, and n represents 5-1000) can be preferably used. As the polyalkylsiloxane derivative, a modified silicone oil having each of the above organic functional groups is suitable for performing a hydrolysis reaction with silicon alkoxide or a derivative thereof. By appropriately selecting the type of the introduced organic functional group, the position of introduction into the siloxane, and the molecular weight of the modified silicone oil, a good silica-silicone composite can be obtained.

In producing the porous silica / silicone composite material of the present invention, first, a polyalkylsiloxane derivative is added to a dilute solution of silicon alkoxide or a derivative thereof, and water is added to hydrolyze. At this time, a catalyst is added as necessary to promote the chemical reaction of hydrolysis. Both basic and acidic catalysts can be used as the catalyst. As the basic catalyst, for example, ammonia, sodium hydroxide, potassium hydroxide or a salt thereof with a weak acid,
Examples of the acidic catalyst include hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid and salts of these with a weak alkali. These amounts are arbitrary and not particularly limited, but silicon alkoxide or its derivative 30 to 99 wt%, polyalkylsiloxane derivative 1 to 7
About 0 wt% is preferable. The amount of the organic solvent is preferably diluted so that the total amount of the silicon alkoxide or its derivative and the polyalkylsiloxane derivative is about 1 to 40% by weight of the total mixture. The amount of water is preferably at least the theoretical amount required for hydrolysis.

The above hydrolysis reaction produces a wet gel. The gel thus formed is dipped in an organic solvent, aged, dried, and dried to obtain the porous silica of the present invention.
A silicone composite is obtained. The drying method is supercritical drying, vacuum freeze drying, vacuum drying, hot air drying, high frequency drying,
Methods such as natural drying are possible. However, in the present invention, since the wet gel is a composite of flexible silicone in the skeleton of silica and silicone absorbs strain such as shrinkage during drying, and has a feature that cracks are unlikely to occur. It is not necessary to perform supercritical drying unlike airgel, and a good porous body can be obtained by freeze vacuum drying or natural drying. These drying methods are very simple and inexpensive methods that do not use a pressure vessel for high pressure unlike supercritical drying, and can greatly reduce the manufacturing cost.

In the above series of production methods, a skeleton formed by silica and silicone formed by a combination of an alkoxy group or an organic functional group of a silicon alkoxide or a derivative thereof and an organic functional group of a polyalkylsiloxane derivative. Are different. The following is a typical example. For example, when the alkoxy group of silicon alkoxide or its derivative and the organic functional group of the polyalkylsiloxane derivative are alkoxy groups, it is considered that a skeleton is formed by the following reaction.

[0013]

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When the organic functional group of the silicon alkoxide derivative is an isocyanate group and the organic functional group of the polyalkylsiloxane derivative is a carbinol group,

[0015]

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When the organic functional group of the silicon alkoxide derivative is an amino group and the organic functional group of the polyalkylsiloxane derivative is an epoxy group,

[0017]

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When the organic functional group of the silicon alkoxide derivative is an epoxy group and the organic functional group of the polyalkylsiloxane derivative is a carboxyl group,

[0019]

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Each of the above reactions forms a respective skeleton. The porous silica / silicone composite material obtained in this manner is a material having high flexibility and good workability that has solved the problems of aerogel.

[0021]

The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereto. (Example 1) 4.0 g of γ-isocyanatopropyltriethoxysilane (A-1310 manufactured by Nippon Unicar) and 11.8 g of 1,4-dioxane were added and stirred well. To this, aqueous ammonia (2.0 mol / l) and aqueous ammonium fluoride (0.2 mol / l) were added dropwise, and the mixture was further stirred and reacted for 24 hours. To this amino-modified silicone oil (KF-8012 made by Shin-Etsu Silicone)
2.0 g and 78.0 g of 1,4-dioxane were added and stirred, and aqueous ammonia and aqueous ammonium fluoride were mixed and added. The total amount of ammonia water and ammonium fluoride water is 2.16 each
Adjusted to g. After thoroughly stirring the mixture,
The gel was allowed to stand in a 5 ° C. atmosphere. Remove the completed wet gel from the container, immerse in 1,4-dioxane at 25 ° C
Cured. After the water content in the wet gel became 2 wt% or less, the sample was frozen in a freezer at −20 ° C. Place the frozen sample in a vacuum dryer and heat it to 5 ° C for 1,4
-Dioxane was sublimated to obtain a porous silica / silicone composite material. The porous silica-silicone composite material thus produced is a marshmallow-like flexible material having a bulk density of 0.06 g / cm ³ and a thermal conductivity (measured by a flat plate comparison method) of 0.0
26 W / mK, specific surface area (measured by BET method) was 86 m ² / g.

(Examples 2 to 4, Comparative Example 1) Examples 2 to 4 were conducted in the same manner as in Example 1 except that the types and amounts of silicon alkoxide derivatives and polyalkylsiloxane derivatives were changed.
As shown in Table 1. In addition, a case where a gel obtained from only an alkoxide derivative of silicon was prepared by the same method is shown in the same table as Comparative Example 1.

[0023]

[Table 1]

Example 5 γ-Aminopropyltriet
8.0 g of xysilane (KBE903 made by Shin-Etsu Silicone), Cal
Binol-modified silicone oil (Shin-Etsu Silicone X-
22-160AS) 2.0 g, add 85.2 g of tetrahydrofuran
Stirred well. To this, 4.8 g of water was added dropwise and further stirred.
Thereafter, the mixture was allowed to stand in an atmosphere at 25 ° C. to be gelled. The finished wetness
Remove the wet gel from the container and soak it in tetrahydrofuran.
And cured at 25 ° C. The water content in the wet gel drops below 2 wt%
After placing the sample in the critical point drier,
Was. CO in this_TwoTo liquefy under pressure,
Lofran CO_TwoSpread in CO _TwoWith critical point dryer
Discharged outside. After the discharge is completed, close the critical point dryer
Heating, pressurizing, and reducing temperature and pressure to CO_TwoCritical point of
That's it. Then lower the pressure, lower the temperature, and return to normal pressure and normal temperature.
And take out the dried gel, and use porous silica / silicone composite
Wood was obtained. The porous silica and silicon
Cone composite is a marshmallow-like flexible material that
Degree is 0.08g / cm^Three, Thermal conductivity (measured by flat plate comparison method) 0.028
W / mK, specific surface area (measured by BET method) 71m^Two/ g.

(Examples 6 to 8, Comparative Example 2) In the same manner as in Example 5, the cases where the types and amounts of the silicon alkoxide derivative and the polyalkylsiloxane derivative were changed were used.
As shown in Table 2. In addition, a case where a gel obtained from only an alkoxide derivative of silicon was prepared by the same method is shown in the same table as Comparative Example 2.

[0026]

[Table 2]

Example 9 4.0 g of γ-glycidoxypropyltriethoxysilane (KBE-403 manufactured by Shin-Etsu Silicone) as an alkoxide or a derivative thereof, and 4.0 g of tetraethoxysilane as an alkoxide or a derivative thereof
Then, 23.3 g of 1,4-dioxane was added thereto, followed by thorough stirring. To this, aqueous ammonia (2.0 mol / l) and aqueous ammonium fluoride (0.2 mol / l) were added dropwise, and the mixture was further stirred and reacted for 24 hours. To this, 1.0 g of carbinol-modified silicone oil (X22-160AS manufactured by Shin-Etsu Silicone) and 65.5 g of 1,4-dioxane were added, stirred, and mixed with aqueous ammonia and aqueous ammonium fluoride. Ammonia water and aqueous ammonia fluoride were adjusted so that the total amount was 2.2 g each. After the obtained mixed solution was sufficiently mixed, the mixture was allowed to stand in a 25 ° C. atmosphere to gel. The completed wet gel was removed from the container, immersed in 1,4-dioxane, and cured at 50 ° C. After the water content in the wet gel became 2% by weight or less, the sample was taken out of the solution and allowed to stand at atmospheric pressure to vaporize 1,4-dioxane, thereby obtaining a porous silica / silicone composite material. The porous silica / silicone composite material thus produced has a styrofoam-like elasticity, a bulk density of 0.11 g / cm ³ ,
The thermal conductivity (measured by the flat plate comparison method) was 0.032 W / mK, and the specific surface area (measured by the BET method) was 45 m ² / g.

(Examples 10 to 12, Comparative Example 3) Example 9
Example 1 was conducted in the same manner as in Example 1 except that the types and amounts of the silicon alkoxide derivative and the polyalkylsiloxane derivative were changed.
The results are shown in Table 3 as 0 to 12. In addition, a case where a gel obtained from only an alkoxide derivative of silicon was prepared by the same method is shown in the same table as Comparative Example 3.

[0029]

[Table 3]

In the above, the evaluation of the brittleness was evaluated as “◎” when the product after drying was almost completely restored even if the thickness was reduced to １ ／, and also compressed to 同 じ く. Even when the stress is almost completely restored, "○" is given, and when a stress is applied to cause cracking and breakage, "x" is given.
It can be seen that in each of the examples, the thermal conductivity was equal to that of the comparative example, but excellent evaluation results were obtained in terms of brittleness. This indicates that the silica / silicone composite material of the present invention has excellent flexibility and good workability.

[0031]

As described above, the porous silica / silicone composite material of the present invention is a composite of flexible silicone in a silica skeleton and has the same heat insulation performance as airgel. It has much better mechanical properties than airgel, especially flexibility, and is also excellent in workability. For example, when it is used as a heat insulating material, good workability can be obtained.

Claims (4)

[Claims] An alkoxide of silicon or a derivative thereof,
A porous silica / silicone composite material obtained by drying a gelled product with a polyalkylsiloxane derivative. 2. An alkoxide of silicon or a derivative thereof.
For 99 parts by weight, polyalkylsiloxane derivatives 1 to 70
The porous silica / silicone composite material according to claim 1, wherein the porous silica / silicone composite material is blended in parts by weight. 3. The porous silica / silicone composite according to claim 1, wherein the bulk density is 0.01 to 0.5 g / cm ³ . 4. An alkoxide of silicon or a derivative thereof,
A method for producing a porous silica / silicone composite material, comprising gelling a polyalkylsiloxane derivative and drying.