JPH02199077A - Microporous material - Google Patents

Abstract

PURPOSE:To obtain microporous material having sufficient mechanical strength and excellent handling properties with keeping excellent heat insulating properties by dispersing fiber of thermoplastic resin into microporous material and mutually fusing fiber with fiber and fiber with ultrafine particle. CONSTITUTION:In a microporous material obtained by molding of ultrafine granular powder, fiber of thermoplastic resin is dispersed and fiber with fiber, and fiber with ultrafine particle are mutually fused to form a microporous material. In said microporous material, volume of the resin component is small in comparison with ultrafine particles of the heat insulating material and almost constructing microporous material as aggregate of ultrafine particle, thus heat insulating property is extremely high. Besides, said resin fiber is bonded by fusion and area of bonded part (adhered area) is extremely, thus increase of heat conduction in solid is small as the resin is a material having relatively small thermal conductivity. Therefore, traditional properties are able to be nearly kept with regard to heat insulating properties and area of the bonded part (adhered area) is extremely small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a microporous material used for heat insulating materials and the like.

[Conventional technology]

Conventional microporous bodies made of fine particle aggregates (fine particle compacts) are high-performance heat insulating materials with extremely low thermal conductivity, but their weak strength makes them difficult to handle (processability, large size). ) was limited, and there was a female in practical use. For example, in order to increase the strength of the molded product, inorganic fibers such as ceramic fibers are mixed and the entanglement of the fibers is utilized, or a bag is filled with insulating material powder made of fine particles and then molded. However, the ease of handling has not been satisfactory in either method.

Above, Japanese Patent Publication No. 51-40088, Japanese Patent Application Publication No. 57-1
See JP-A No. 73689, JP-A-58-45154, and JP-A-60-33479.

On the other hand, in order to increase the strength of the microporous material, a method using a general binder such as a low melting point glass or a low melting point inorganic compound has been considered.

According to this method, the binder is melted and aggregates of fine particles are combined to solidify the binder, so that the strength and handleability of the microporous body are improved.

[Problem to be solved by the invention]

However, when the binder is used, aggregates of fine particles are bound together by the binder, so conduction through the solid becomes thick, and as a result of filling minute voids, the thermal conductivity becomes high. Its performance as a heat insulator was significantly reduced.

In view of the above-mentioned circumstances, it is an object of the present invention to provide a microporous material that has sufficient mechanical strength and is easy to handle while maintaining the excellent heat insulating properties of an aggregate of microparticles.

[Means to solve the problem]

In order to solve the above problems, the microporous body according to the claimed invention is formed by molding fine particle powder, in which fibers made of thermoplastic resin (hereinafter referred to as "resin fibers") are dispersed, and resin fibers are dispersed therein. It is characterized in that the fibers and the resin fibers and the fine particles are fused to each other.

[For production]

The microporous body of the present invention is composed of an aggregate of fine particles of a heat insulating material and a framework of resin fibers that are fused together. The resin component has a smaller capacity than the fine particles of the heat insulating material, and is mostly a microporous body made up of aggregates of fine particles, so it has extremely high heat insulation properties. In addition, since the resin fibers are bonded by fusion, the area of the bonded part (adhesion area)
becomes very small, and the resin itself is a material with relatively low thermal conductivity, so the increase in solid conduction is small. Therefore, the heat insulation performance can maintain almost the same as the conventional performance.

As for strength, since the resin fiber framework surrounds the fine particle aggregates with low bonding strength, the mechanical strength increases and the handleability becomes good.

〔Example〕

Hereinafter, examples of the microporous body according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the microporous material of the present invention. Fig. 1 (18) is a schematic diagram of the entire microporous material, Fig. 1 (b) is an enlarged view of the case where resin fibers are used as the resin solid, and Fig. 2 is an enlarged view of the case where resin fibers are used as the resin solid. FIG. 3 is an enlarged view of another example in which fine resin particles and resin particles are used together.

As shown in these figures, in the microporous body 1, the voids S constituted by a large number of fine particles 2 are, for example, 1
There are very small voids of ~60 nm, and the fine particles 2 are microporous bodies that undergo IJiS due to cohesive force (Van der Waalska).

The resin portion is uniformly dispersed throughout, and there is a portion M where the resin fibers 3 are partially in contact with each other, or a portion M where the resin fibers 3 and the fine particles 2 of the heat insulating material are partially in contact with each other.・・・
In the embodiment shown in FIG. 2 in which the resin fibers 3 are bonded to each other, the resin fibers 3 and the heat insulating material fine particles 2 are bonded together, and the resin fibers 3 and the resin fine particles 4 are bonded to each other. The fine particles 2 of the heat insulating material and the fine resin particles 4 are fused and bonded to each other at portions M where they are partially in contact with each other.

The microporous body of the present invention is manufactured, for example, as follows, but the manufacturing method is not limited to the following method. Fine particles of heat insulating material are mixed in advance to form a mixed powder, and resin solids (resin fibers or
(resin fibers and resin particles) are mixed and dispersed uniformly. A mold is then filled with this mixture and compression molded. At this time, the fine particles of the heat insulating material are formed into a microporous body with sufficiently small voids (preferably 1 to 60 na+), and the resin content is uniformly dispersed in a part of the porous body. There is. Next 1. While this molded body is compressed, the resin is heated to a temperature above its melting point to fuse it, and then cooled to a temperature below its melting point to harden (solidify) the resin. After cooling, it is removed from the mold to form a molded microporous body.

The microporous material according to the present invention has high mechanical strength and can be processed by cutting, etc., so it is easy to handle, and it also maintains sufficient heat insulation properties. For this reason,
This microporous body can be used as a heat insulating material (insulating body). However, the use of the microporous material of the present invention is not limited to heat insulating materials.

The fine particles of the heat insulating material are ultrafine particles A (silica, surface treated particles, etc.) and fine particles B (particles with a radiation prevention effect such as TiOx), and in addition to these, inorganic fibers (silica alumina fibers, etc.) are mixed. You can.

In this invention, as the fine particles, it is preferable to use at least ultrafine particles A out of the following ultrafine particles A and fine particles B, and, if necessary, to use the following fine particles B and/or inorganic fibers together with the ultrafine particles B. This is because if only fine particles B and/or inorganic fibers are used as a heat insulating material, the voids formed will become large and a sufficient heat insulating effect cannot be obtained, but when ultrafine particles A are used, the voids formed will be small (for example, , 1 to 60 nm), and a high-performance heat insulating material can be obtained.

When ultrafine particles A are used together with fine particles B and/or ta-free fibers, the ratio of these uses varies depending on the usage temperature, handling conditions, etc., but for example, if ultrafine particles A are used in
It is preferable that the amount of fine particles B be 0 to 100% by weight, the amount of fine particles B be 0 to 70% by weight, and the amount of inorganic fiber be 5 to 20% by weight.For inorganic fibers, if the amount is out of this range, problems may occur in strength and heat insulation. There is.

An example of the ultrafine particles A is ultrafine silica produced by a dry manufacturing method or a wet manufacturing method. The ultrafine silica particles may be treated to prevent agglomeration if necessary. The particle size of the ultrafine particles A is preferably about 1 to 20 n-
Those with a diameter of 0 nm or less, and those with a diameter of 3 to 8 nanometers are more preferable.

When using the ultrafine silica powder, it is preferable to select its particle size, and the preferable particle size is that the specific surface area of the untreated ultrafine silica powder is 400 rrf/g or more, or the particle size is 60 Å or less. .

The surface treatment agent used in the above-mentioned W sludge prevention treatment includes one that binds to the OH of the silanol group on the particle surface to prevent the generation of hydrogen bonds, and one that provides repulsion between particles and directly prevents particle aggregation. Examples include things to do. Examples include organic silane compounds such as alkoxysilane compounds such as trimethylmethoxysilane, dimethyljethoxysilane, and methyltrimethoxysilane; chlorosilane compounds such as dimethyldichlorosilane, trimethylchlorosilane, and triphenylchlorosilane; hexamethyldisilazane; Examples include, but are not limited to, silazane compounds such as dimethyltrimethylsilylamine.

In addition, when using a solvent for treatment with a surface treatment agent, examples of the solvent include benzene, water, toluene, etc.
The ultrafine particles are not limited to these as long as they can be easily dispersed.

When performing agglomeration prevention treatment using a surface treatment agent, the degree of the treatment may be controlled. Here, the degree of treatment refers to the amount of hydrophobic groups (groups derived from the surface treatment agent) bonded to the surface of the ultrafine particles, and refers to the carbon content (wt%) in the treated particles. (hereinafter referred to as "M value") and the degree of hydrophobicity of the surface-treated particles (hereinafter referred to as "M value").

The above M value is determined by adding 0.2 g of the treated product to 50 cc of water and
It is expressed as the volume % of MeOH consumed when all treated products are wetted with water by dropping e OH, and can be determined by the following formula.

The degree of surface treatment can be changed depending on the treatment conditions according to the C value and M value assumed in advance. Note that the C value and M value differ depending on the treatment system (combination of ultrafine particles and surface treatment agent). By controlling the degree of surface treatment in this way, it is possible to avoid excessive treatment (, weak treatment (C value,
It becomes possible to effectively achieve effective agglomeration prevention treatment with a small M value).

In this invention, the ultrafine particles A are used alone or may be mixed with one or more types of other fine particles B having a larger primary particle size than the ultrafine particles A. By molding such a mixture, It is possible to improve moldability and reduce manufacturing costs.

When ultrafine particles A and other fine particles B having a larger primary particle size are mixed and molded, the large voids between the fine particles B having a larger particle size are filled with the ultrafine particles A having a smaller particle size. Therefore, the voids within the microporous body can be essentially considered to be voids between the ultrafine particles A. For this reason,
It becomes possible to form fine voids that are not affected by the thermal conductivity of still air. In such a structure, moldability is improved by including fine particles B having a large particle size. This is thought to be because the fine particles B, which have a large particle size, and the ultrafine particles A, which have a small particle size, disperse and absorb the molding pressure with each other, thereby maintaining the molding pressure uniformly.

Fine particles B having a larger primary particle diameter than ultrafine particles A include finely pulverized pearlite and shirasu balloons, soot, cordierite, inorganic layered compounds such as clay, diatomaceous earth, calcium silicate, carbon black, SiC, Ti0
g, ZrO, Crow, FesO4, CuS
%CuOIMnOt,SiOx,A1
Examples include fine particles such as 10x, Coo, and LitOlCaO. All of these materials have a high thermal emissivity, and preferably have a thermal emissivity of 0.8 or more in the infrared region with a wavelength of 3 μ or more. The reason why a material with a large thermal emissivity is preferable is as follows. In other words, heat transfer due to radiation cannot be prevented by ultrafine particles A (
However, the fine particles B with good thermal emissivity are
It works by converting radiant energy into heat and preventing it from passing through. Once the radiant energy is converted into thermal energy in this way, the microporous material according to the present invention has excellent heat insulation properties, so that it can easily be used for the purpose of heat transfer by conduction. can be achieved. However, in this invention, the type of fine particles B with a large -order particle size is not limited to those with a large thermal emissivity as described above, and any fine particles with a particle size of about 5 to 10,000 n- may be used. It may even be something. In addition,
Although the preferable particle size ranges of ultrafine particles A and fine particles B partially overlap, when ultrafine particles A and fine particles B are used together, it is recommended to use particles with a larger particle size than ultrafine particles A. Fine particles B are selected as appropriate.

In this invention, in order to further improve the handling properties of the microporous molded product, inorganic fibers may be mixed with the fine particle powder and molded. In this case, examples of the inorganic fibers include ceramic fibers, glass fibers, rock wool fibers, asbestos fibers, carbon fibers, and aramid fibers. The amount added is 20% of the weight of the fine particles of the insulation material.
The following are preferred. The fiber diameter of the inorganic fiber is preferably 30n or less, more preferably 5μ or less. The fiber length is preferably 30 m, more preferably 201 m or less, but a fiber length of about 50 m can also be used.

The method for molding the microporous body is not particularly limited in the present invention, and a method that is normally used for molding such a porous body, such as a pressure molding method, may be used as is.

In addition, when the ultrafine particles A are, for example, ultrafine particle silica produced by a dry process or a wet process, and are dispersed in a solvent to perform an agglomeration prevention treatment, the above-mentioned silane compound that reacts with silanol groups may be used as a surface treatment agent. By doing so, it is possible to prevent agglomeration and at the same time impart water repellency to the particle surface, and it is possible to produce a microporous body with excellent heat insulation properties that hardly changes over time due to adsorption of water in the air.

The resin fibers 3 and the resin particles 4 are each made of a thermoplastic resin that can be fused by heating. Examples of the thermoplastic resin include polyethylene, polypropylene, thermoplastic polyester, polyacrylate, polyvinyl chloride, and polyvinyl chloride. Acrylonitrile synthetic resins, synthetic polyamides, composites thereof, etc. are used. As mentioned above, the shape of the thermoplastic resin is fibrous or 1. It is a fine particle. In this invention, at least resin fibers out of resin fibers and resin fine particles are always used. this is,
This is because the addition of fibers creates intertwining of the fibers, so the strength can be improved with a small amount compared to the case of powder alone.

The resin fiber preferably has a diameter of about 0 to 50 μm and a length of about 1 to 5 μm, and is preferably a straight fiber. This is because if the fibers are long or have crimps (irregularities), they may become tangled and cannot be uniformly dispersed.

Further, the resin fine particles have a particle size of IOpm or less (,
More preferably, it is 1 p or less.

Regarding the mixing method, when mixing heat insulating materials, it is mixed using a high-speed mixer, but when mixing with resin, it is best to incorporate enough gas such as air to make the powder fluid and mix. good. For example, mixing using a fluidized bed is preferable. In the case of rapid mixing, heat is generated locally, which causes some of the resin parts to fuse together, making it difficult to disperse uniformly.

The amount of the resin added layer is preferably 1 to 10% (more preferably 2 to 5%) based on the weight of the heat insulating material (fine particles), although this varies depending on the type.

The molding pressure is preferably 10 to 30 kg/cflI, and the heating temperature is preferably 30 to 60° C. higher than the melting point of the resin.

Note that this invention is not applicable to what is illustrated in FIGS. 1 and 2. Ultrafine particles A are treated to prevent aggregation,
Any untreated material may be used.

More specific examples and comparative examples of the present invention will be described below, including the manufacturing process, but the invention is not limited to the following examples.

Example 1 ~ As a heat insulating material, ultrafine silica surface treated with hexamethyldisilazane (manufactured by Tokuyama Soda ■, custom made product, average particle size 8 nm), Tiot rutile powder (FR manufactured by Furukawa Mining ■)
-41, particle size 0.2x) in a weight ratio of 3:1, and to this, polyester fiber (manufactured by Toyobo, PETw!i fiber, diameter 1
Add air to the insulating material powder to make it fluid so that the weight ratio of the insulating material powder is 5% by weight to the insulating material, then add it little by little, and stir slowly to make it uniform. Next, this mixed powder was poured into a mold and left to stand for 5 minutes to allow natural degassing.Then, the upper mold was placed on the mold.
While pressing with a direct press at a molding pressure of 20 kg/cJ, the mold temperature was set at 220° C. and held for 30 minutes after the temperature became constant. Next, the mold was transferred to another press and cooled while keeping the molding pressure at 20 kg/-. After cooling, the microporous body is removed from the mold and formed into a plate shape (
A heat insulator) was obtained. The external dimensions of the microporous body are 80 mm in diameter.
The surface-treated ultrafine particle silica had a particle size of about 7 mm when untreated.
ntm, specific surface! The particle size of 1,380ml/g was surface-treated to have a particle size of 8 to 9 nm and a specific surface area of 300 rrr/g.
, C value was 2.8 wt%, and M value was 60 volχ.・On the other hand, apart from this, the particle size is 5 nm when untreated.
, which had a specific surface area of 480+vr/g, was surface-treated to have a particle size of 7 nm, a specific surface area of 350 rrr/g, and a C value of 2.
8 wt%, M value of 60 vol.
I got it.

Example 2 - Polyester fiber coated with polyethylene (manufactured by Toyobo, PE-PET fiber, diameter 15
Except that μ■, length 2■1) was mixed so that the weight ratio was 3% of the insulation material, and the heating temperature was 180℃.
A microporous body (insulating body) was obtained in the same manner as in Example 1.

Example 3 - Polyethylene fine particles (Shorex P235WH-2 manufactured by Showa Denko ■, average particle size 50 to 70 μm) and the PE-PET fibers used in Example 2 were used as the resin, and each A microporous body (insulating body) was obtained in the same manner as in Example 1, except that the components were mixed at a weight ratio of 3% and the heating temperature was 180°C.

Example 4 As a heat insulating material, the surface treated silica used in Example 1, T
i0 = In addition to powder, inorganic ceramic fiber (
Made by Nippon Steel Chemical ■, SC bulk #111, diameter 2.8n,
5 m in length), and the blending ratio by weight was: Surface treated silica: Troz powder: Ceraminokutsu iber = 1
The ratio was set to 1:0.2. A microporous body (insulating body) was obtained in the same manner as in Example 1 except for the above.

Example 5 - A microporous material (insulating material) was obtained in the same manner as in Example 2, except that the material used in Example 4 was used as the heat insulating material.

Comparative Example 1 Only the heat insulating material used in Example 1 was molded under a molding pressure of 20 kg.
/ctA for 5 minutes to obtain a microporous body (insulating body).

- Comparative Example 2 Only the heat insulating material used in Example 4 was used at a molding pressure of 20 kg/
A fine porous body (insulating body) was obtained by pressing with CD for 5 minutes.

Thermal conductivity and bending strength of the microporous bodies of Examples 1 to 5 and Comparative Examples 1 to 2 were measured.

The results are shown in Table 1.

The thermal conductivity was measured using a thermal conductivity measuring device manufactured by English-French Seiki Oki in accordance with ASTM-C518, and the bending strength was measured in accordance with JIS-A9510. .

As shown in Table 1, the microporous material of the example is different from that of the comparative example. It can be seen that although the thermal conductivity of all the li fine and porous bodies is slightly higher, they have a sufficient heat insulating effect and have much greater mechanical strength.

〔Effect of the invention〕

As described above, the microporous material according to the present invention has high mechanical strength and excellent handling properties, and also maintains sufficient heat insulation properties, so it is highly practical.

[Brief explanation of the drawing]

FIG. 1 (al is a schematic diagram showing one embodiment of the microporous material of the present invention, FIG. 1 (bl is an enlarged schematic diagram showing the state of fusion, and FIG. 2 is another embodiment) It is an enlarged schematic diagram showing the state of fusion. 1... Fine porous body 2... Fine particles (of the heat insulating material) 3
... Resin fiber 4 ... Resin fine particle agent Patent attorney
Takehiko Matsumoto

Claims (1)

[Claims] 1. In a microporous body formed by molding fine particle powder,
A microporous body characterized in that fibers made of a thermoplastic resin are dispersed, and the fibers and the fine particles are fused to each other.