JP2001018246A - Porous composite and its preparation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous composite wherein a molded body of powder or granule hardly contains air and a method for preparing it. SOLUTION: Air in a highly heat insulating gas atmosphere is replaced with a highly heat insulating gas by using an aerogel under the highly heat insulating gas atmosphere. In addition, a mixing process of this with a urethane raw material and a foaming process are performed under the highly heat insulating gas atmosphere to obtain a porous composite which hardly contains highly heat insulating air. As the result, heat insulating performance is improved and ratios of oxygen and nitrogen in the gas in the porous composite are at most 1%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous composite used as a heat insulating material, a sound insulating material and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, it has been proposed to mix and foam heat-insulating porous granules or powders with a foamed resin raw material so as to easily use amorphous and difficult-to-handle materials. ing. For example, it has been proposed that urethane foam used for a heat insulating material of a refrigerator is pulverized into granules, and then reshaped and used. Further, a method for producing dry gel particles having high heat insulation and mainly using a silica-based material called aerogel is disclosed in, for example, a US patent. Further, it has been proposed to produce a highly heat-insulating molded body by mixing and foaming a dry gel particle with a urethane raw material (Japanese Patent Laid-Open No. Hei 7-316328).

[0003]

When a granule or powder is molded and mixed and foamed with a foamed resin raw material and molded, air is contained in the pores in the granule or powder. Air also remains in the porous composite. Since this air has a high thermal conductivity, there is a problem that the heat insulation of the porous composite does not sufficiently decrease.

The present invention has been made in view of the above-mentioned problems of the conventional method for producing a porous composite, and has developed a porous composite and a method for producing the same in which there is almost no air in a powder or granule compact. The purpose is to provide.

[0005]

Means for Solving the Problems In order to solve the above problems, the porous composite of the present invention has a porous structure having a pore diameter of 1 mm or less and a density of 0.02 g / cm ³ or more and 0.3 g / cm ³ or less. A composite comprising a strip and a porous binder for bonding the porous strip, wherein the volume of the porous strip occupies 20% or more of the volume of the composite, The composition is such that the total partial pressure of oxygen and nitrogen present as gas in the hole is 0.05 atm or less, and the total pressure in the hole is 0.1 atm or more.

In this case, it is preferable that the porous strip is a dry gel strip having a communication hole.

It is preferable that the porous binder is a resin foam, and the pores of the resin foam are composed of closed cells.

It is preferable that the dried gel strip having the communicating hole is an organic dry gel strip and the resin foam is polyurethane.

Further, the molecular weight in the pores of the porous composite is
44 or more gases are present in at least one kind, and the total partial pressure of the at least one kind of gas is 10 times the total partial pressure of nitrogen and oxygen present as gas in the pores of the porous composite. It is preferable that it is above.

The method for producing a porous composite according to the present invention is characterized in that the pores of the porous strip are filled with a substance having a molecular weight of 44 or more, and the porous strip and the resin are filled in a gas atmosphere having a molecular weight of 44 or more. After mixing with a foam raw material, it is formed by foam molding.

In this case, the substance filling the pores of the porous strip is preferably one of carbon dioxide, pentane and hexane or a mixture thereof.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the porous composite of the present invention. This is a cross-sectional view when the porous composite 2 is molded in the container 1. The porous composite 2 has a pore 3 formed of a porous binder and a porous composite having pores therein. It is composed of strips 4. The porous binder shown by the thick solid line forms the holes 3, and the connection of the holes 3 is formed by supporting the porous strips 4, thereby forming the porous composite 2. However, as shown in FIG. 1, there may be a region where the porous strips 4 are partially gathered and a region where the pores 3 formed by the porous binder are continuously present.

The first characteristic of the structure of the porous composite of the present invention is that, although the porous strip containing a large amount of air occupies more than 20% by volume during the usual production, the pores 3 That is, in the pores 3 of the porous binder, the pores in the porous strip 4 or the pores formed from the gaps between them, oxygen,
Nitrogen is contained in a total of only 0.05 atm or less, and the total pressure in the pores is 0.1 atm or more. Since there are few air components such as oxygen and nitrogen having high thermal conductivity, the thermal conductivity of the entire porous composite can be reduced. In addition, the diameter of the pores of the porous strip is 1 mm or less and convection of gas is small enough to be ignored, and the density is 0.02 g / cm ³ or more and 0.3 g / cm ³ or less. The thermal conductivity of the porous strip itself is low. This also contributes to lowering the thermal conductivity of the porous composite.

Here, the porous strip is a small strip having the above-mentioned pore diameter and density, and its shape includes a flat strip, a granule, and a powder, and the size is about 1 cm or less. Means From the viewpoint of handling, those having a size of several mm to several μm are preferable.

The porous strip is preferably a porous strip made of a dried gel. This is because the dried gel has a small pore diameter of several tens of nm or less, and high heat insulation can be obtained. Examples of the dry gel include an aerogel obtained by supercritical drying of a wet gel, a cryogel obtained by freeze-drying, and a xerogel obtained by drying while maintaining a gas-liquid interface. Further, as such a gel material, a silica gel, a phenol gel, a melamine gel, an isocyanate gel, a urethane gel, and the like are known, and are configured using these. In addition, there are a polyvinyl alcohol-based gel and a polyacrylic acid gel-based gel.

On the other hand, examples of the porous binder include the above-mentioned various dry gels having pores of several tens of nm and resin foams having pores of usually several mm to several tens of μm. For this reason, a resin foam is preferred. Particularly, as the resin foam, in addition to urethane and isocyanurate, a polyolefin resin foam such as polyethylene, polypropylene, and ethylene vinyl acetate is preferable. As other resin foams, polycarbonate, polysulfone,
Poly (phenylene oxide), polymethyl methacrylate, polyimide, polyamide, polymethacrylamide,
There are resin foams such as epoxy, silicone, phenol, melamine-formaldehyde, and polyvinyl chloride. The resin foam preferably forms closed cells, in which case the porous strip contains a small amount of air, and even if the porous strip has communication holes, the porous strip is Since the cells are confined in the closed cells, diffusion of the air into adjacent cells is suppressed, and a decrease in thermal conductivity is suppressed. Further, intrusion of air from the outside can be suppressed.

In the porous composite of the present invention,
It is preferable that an organic dry gel such as a phenol-based gel, a melamine-based gel, an isocyanate-based gel, or a urethane-based gel is used as a porous strip, and a urethane resin foam or an isocyanurate resin foam is used as a porous binder.
This is because the strength of the porous composite is increased by bonding a hydroxyl group, an amino group, and the like of the organic gel with a resin foam, such as polyurethane and isocyanurate, a raw material of isocyanurate. Of course, it is also possible to make isocyanate-reactive by modifying a gel having no isocyanate-reactive functional group.

Further, the pores in the porous composite have a molecular weight of 4
It is filled with four or more gases, and the sum of the partial pressures of this gas is 10 times the sum of the partial pressures of the nitrogen and oxygen components in the same hole.
It is preferably at least two times. Since the gas filling the pores has a molecular weight of 44 or more, its thermal conductivity is smaller than that of carbon dioxide and is about 60% or less of the air component. Moreover, since the amount of the air component is 10 times or more that of the air component such as oxygen and nitrogen and the proportion of the air component is small, the thermal conductivity is significantly reduced. The gas having a molecular weight of 44 or more includes hydrocarbons such as butane, pentane, and hexane having a relatively high vapor pressure at room temperature, in addition to carbon dioxide, krypton, and xenon. As for butane, pentane and hexane, their isomers are of course included, but among them, cyclopentane and cyclohexane having a low thermal conductivity and a relatively low boiling point are preferred. Of course, other organic substances such as ethers, alcohols and esters can also be used as long as they have a boiling point of about 100 ° C. or lower.

Next, a method for producing the porous composite of the present invention will be described.

The manufacturing method of the present invention is characterized in that, first, pores in a porous strip whose pores are usually filled with air are:
After replacing with a substance having a molecular weight of 44 or more, the porous composite and the foamed resin material are mixed and foamed in a gas atmosphere having a molecular weight of 44 or more. By doing so, in the porous composite, air having a high thermal conductivity is excluded, and the porous material is filled with a gas having a molecular weight of 44 or more and a thermal conductivity lower than that of carbon dioxide. A porous composite is obtained.

The gas having a molecular weight of 44 or more used herein includes carbon dioxide, krypton,
Xenon, hydrocarbons such as butane, pentane, and hexane, which have relatively high vapor pressures at room temperature, as well as organic substances such as ethers, alcohols, and esters having a boiling point of about 80 ° C or less and a saturated vapor pressure of 0.1 atm or more at room temperature are used. However, krypton, xenon, carbon dioxide, pentane, and hexane are preferred in consideration of low thermal conductivity, high saturation vapor pressure in the case of a liquid at room temperature, and low toxicity. Among the isomers of pentane and hexane, cyclopentane and cyclohexane having low thermal conductivity are particularly preferable.

In the above manufacturing method, when the pores of the porous strip are replaced with a substance having a molecular weight of 44, when the substance is a gas at room temperature, the replacement is performed by placing the substance in the gas atmosphere for a certain period of time. However, in the case of carbon dioxide or the like, it is also possible to liquefy by applying high pressure and impregnate it. When the substance is liquid at normal temperature, the substance can be replaced as a gas in an atmosphere in which the vapor pressure is increased to near 1 atm by raising the temperature. When the pores of the porous strip are filled with a liquid, it can be used as a foaming agent.

As the foam molding method, a conventional method can be applied except that it is performed in the above-mentioned gaseous atmosphere (for example, "Detailed techniques of foam molding of various polymers" published by Technical Information Association, 1993). Hydrocarbons such as carbon dioxide and pentane are preferably used as the foaming agent. In the case of a urethane blowing agent, water or a carboxylic acid is also used as a chemical blowing agent that generates carbon dioxide by reacting with isocyanate.

[0025]

Embodiments of the present invention will be described below. In the examples shown here, a urethane resin foam having closed cells was used as the porous binder. As raw materials, the urethane catalyst is Kaolyzer NO1 (manufactured by Kao Corporation), the foam stabilizer is TY-19 (manufactured by Kao Corporation), and the polyol is an aromatic amine polyether polyol with a hydroxyl value of 500 mg kOH /
g, isocyanate used was a polyisocyanate having an amine equivalent of 170.

(Example 1) In this example, a polyurethane resin foam molded article having a density of 0.030 g / cm ³ and open cells having a pore diameter of about 200 μm was crushed to a diameter of 2 to 5 mm as a porous strip. Granules were used. Further, as the porous binder, a polyurethane resin foam having the above-mentioned closed cells was used.

First, 100 g of the above-mentioned granules were conveyed under the pressure of carbon dioxide and charged into a carbon dioxide-substituted iron container. Further, 10 g of cyclopentane was absorbed into the granules. Next, a mixture of 100 g of a polyol, 3 g of a foam stabilizer, 2 g of a urethane catalyst, 1 g of water, and 7 g of cyclopentane was charged into this container and stirred, and then 160 g of polyisocyanate was added and stirred. This started foaming and was shaped into a container to produce a porous composite. The volume of the granules was about 30% of the entire porous composite. The ratio of oxygen and nitrogen in the gas in the porous composite was 1% or less.

For the sake of comparison, the above-mentioned expanded porous granules were left in an air atmosphere, charged into an iron container at a nitrogen pressure, and then foamed and formed in a nitrogen atmosphere in the same manner as in the example. A porous composite was obtained. The thermal conductivity of the porous composite thus obtained was measured by a parallel plate method.
It was about 20% higher than the thermal conductivity of the example. The ratio of oxygen and nitrogen in the gas in the porous composite was about 20%.

As described above, the thermal conductivity was low in the examples because the porous strip having open cells in the comparative example was infiltrated with air having high thermal conductivity, whereas the examples were low in the thermal conductivity. This is because the granules were filled with carbon dioxide and cyclopentane and did not contain air.

Example 2 In this example, a silica xerogel having a density of 0.1 g / cm ³ was used as a porous strip. The particle size was 0.1-1 mm. In SEM observation, continuous pores of several tens of nm were observed. Silica xerogel is prepared by a known method (for example, “Journal of the Korean Ceramic Society”, Vol. 33, No. 12, P. 1394-140).
2, 1996) and obtained by grinding. Further, a polyurethane resin foam having closed cells was used as the porous binder.

First, 400 g of the above-mentioned porous strip was conveyed under the pressure of carbon dioxide and charged into an iron container replaced with carbon dioxide. Thereafter, a porous composite was produced in the same manner as in Example 1. However, the amount of cyclopentane is 0 g and the amount of water is 3
g. At this time, the volume of the porous strip was about 35% of the porous composite. The ratio of oxygen and nitrogen in the gas in the porous composite was 1% or less.

For comparison, the porous strip was left in an air atmosphere, charged into an iron container at a nitrogen pressure, and then foamed and molded in a nitrogen atmosphere in the same manner as in the example to form a porous composite. Obtained. The thermal conductivity of the porous composite thus obtained was measured by the parallel plate method, and was about 10% higher than the thermal conductivity of the example.This value does not include the porous strip. , About the thermal conductivity of polyurethane foam
It was 10% lower.

This is because, in the embodiment, the porous strip and the porous binder are both filled with carbon dioxide without containing air, and the thermal conductivity of the porous strip is higher than that of the porous binder. Is also low.

Example 3 In this example, resorcinol / formaldehyde aerogel particles, which are organic dry gel particles, were used as the porous particles. Density is 0.1g / c
m ³ , the particle size was 0.1 to 1 mm, and continuous pores of several tens of nm were observed by SEM observation. The airgel granules were produced according to a known method (for example, US Pat. No. 5,508,341) and obtained by pulverization. Further, a polyurethane resin foam having closed cells was used as the porous binder.

First, 400 g of the above-mentioned porous strip was conveyed under the pressure of carbon dioxide and placed in an iron container replaced with carbon dioxide. Thereafter, a porous composite was produced in the same manner as in Example 2. At this time, the volume of the porous strip was about 35% of the porous composite. The ratio of oxygen and nitrogen in the gas in the porous composite was 1% or less.

For comparison, the porous strip was left in an air atmosphere, charged into an iron container at a nitrogen pressure, and then foamed and molded in a nitrogen atmosphere in the same manner as in the example to form a porous composite. Obtained. The thermal conductivity of the porous composite thus obtained was about 10% higher than that of the example.This value was about 10% higher than the thermal conductivity of the polyurethane resin foam containing no porous strip. The value was 20% lower.

This is because, in this embodiment, the porous strip and the porous binder are both filled with carbon dioxide without containing air, and the thermal conductivity of the porous strip is different from that of the porous binder. By lower than.

Further, the porous composite obtained in Examples 2 and 3 was cut into 1 cm × 1 cm × 5 cm, and the side surfaces were overlaid and compressed little by little from above and below. The porous composite deformed. Thus, the strength of Example 3 is high because the used porous strip is a strip of an organic dry gel. In this case, the porous strip reacts with the isocyanate of the porous binder raw material and the hydroxyl group of the gel. It is considered that the bonding increased the bonding force with the porous binder.

In the above embodiment, a newly manufactured porous strip was used. However, it is of course possible to pulverize and reshape various used foams, dried gels and the like. .

[0040]

As described above, the porous composite of the present invention is formed by forming highly heat-insulating porous strips such as resin foam particles and airgel particles. The feature is that the amount is very small, and there is an effect that high heat insulating performance can be obtained because there is little air. Further, since the performance can be improved by pulverizing and molding the waste resin foam or aerogel, it can be said that there is also an effect of improving the recyclability.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a cross section when a porous composite according to an embodiment of the present invention is molded in a container.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container 2 Porous composite 3 Porous binder hole 4 Porous strip

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F074 AA78 BA32 BA39 DA12 DA32 DA59 4F212 AA42 AE02 AE06 AG20 AR02 AR15 UA05 UA06 UB01 UC01 UC06 UG02

Claims (8)

[Claims] 1. The possessed hole diameter is 1mm or less and the density is 0.02g / c.
and m ³ or more 0.3 g / cm ³ or less porous strip, a porous composite having a porous binder for binding the porous strip, said in volume of the porous composite Volume of porous strip is 2
Porosity, wherein the total partial pressure of oxygen and nitrogen present as gas in the pores of the porous composite is 0.05 atm or less, and the total pressure in the pores is 0.1 atm or more. Complex. 2. The porous composite according to claim 1, wherein the porous strip is a dried gel strip having communicating holes. 3. The porous composite according to claim 1, wherein the porous binder is a resin foam, and the pores of the resin foam are composed of closed cells. 4. The porous composite according to claim 2, wherein the dried gel flakes having the communication holes are organic dry gel flakes. 5. The porous composite according to claim 3, wherein the resin foam is polyurethane. 6. At least one kind of gas having a molecular weight of 44 or more is present in the pores of the porous composite, and the total partial pressure of the at least one kind of gas is equal to or less than 1 of the sum of the partial pressures of nitrogen and oxygen existing as gases
A porous composite that is at least 0 times. 7. Filling the pores of the porous strip with a substance having a molecular weight of 44 or more, and mixing the porous strip with a resin foam raw material in an atmosphere of a gas having a molecular weight of 44 or more. A method for producing a porous composite, which comprises molding. 8. The method according to claim 7, wherein the substance filling the pores of the porous strip is one of carbon dioxide, pentane, and hexane or a mixture thereof.