JPS6213048B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention provides a moisture-permeable gas shield used for partition plates of total heat exchangers of air conditioners (hereinafter referred to as air conditioning) equipment, and in particular has improved gas selective permeability and flame retardancy. It relates to a moisture permeable gas shield.

In recent years, as air conditioning equipment such as heating and cooling equipment has developed and become more widespread, and the living spaces using these equipment have expanded, there has been an increasing demand for total heat exchangers for air conditioning that can recover temperature and humidity during ventilation. ing. The characteristics of a member used as a partition plate of such a total heat exchanger for air conditioning are required to have low air permeability, high moisture permeability, and flame retardancy. This prevents the fresh air that is drawn into the room from the outdoors and the dirty air that is discharged from the room to the outdoors during use, and also generates latent heat (heat of vaporization of water vapor) at the same time as sensible heat. This is because water vapor must be efficiently transferred between intake air and exhaust air to enable heat exchange, and the components of such air conditioning equipment are required to be flame retardant under the Fire Service Act. be.

In order to meet such demands, the present inventors have already developed water-soluble polymeric substances containing lithium halide and optionally flame retardants as moisture absorbers, such as paper, cloth, nonwoven fabric, asbestos paper, or ceramics. We have invented a gas shield with improved moisture permeability, which has low air permeability and high permeability by impregnating or coating a porous member such as a thin plate (Patent No. 888975).

The moisture permeability coefficient (quantitative value of moisture permeability) and the air permeability coefficient (quantitative value of air permeability) of this moisture-permeable gas shield depend on the content of the moisture absorbent and the water-soluble polymer substance,
The moisture permeability coefficient mainly increases with an increase in the content of the moisture absorbent, and the air permeability coefficient mainly decreases with an increase in the content of the water-soluble polymeric substance. However, the moisture permeability coefficient and the air permeability coefficient of a moisture-permeable gas shield do not change independently, but when the content of water-soluble polymeric substances is increased to reduce the air permeability coefficient, the moisture permeability coefficient also increases. becomes smaller. Furthermore, if the content of the moisture absorbent is increased in order to increase the moisture permeability coefficient, a problem arises in that drainage occurs at high humidity. Even in mass production processing, an increase in the content of moisture absorbers and water-soluble polymer substances reduces the flexibility of the moisture-permeable gas shield that is dried after impregnating them, causing the shield to bend or break when wound up. When unwinding the wound moisture-permeable gas shield, a problem arises in that the chemical that has absorbed moisture adheres to the wound surface, making it impossible to unwind it. For the above reasons, it is not possible to arbitrarily increase the content of the drug, ie, the moisture absorbent and the polymeric substance.

As materials for moisture-permeable gas shields, fibrous porous members such as paper, cloth, nonwoven fabric, and asbestos paper are often used in terms of performance, processability, and cost.
Therefore, in order to find a method for improving the gas selective permeability of a moisture-permeable gas shield without increasing the drug content, the present inventors investigated the moisture permeability coefficient PH of a fibrous porous member. The relationship between the air permeability coefficient Pco ₂ , which is representative of ₂ O and carbon dioxide gas, and the constituent factors of these members was investigated in detail. As a result, it was found that the air permeability coefficient Pco ₂ of a fibrous porous member can be expressed as a function of the porosity of the member ε and the tortuosity q of the void as shown in the following equation.

Pco ₂ = (ε/q ² )・Pco ₂ ...(1) However, P゜co ₂ represents the air permeability coefficient of carbon dioxide gas in the air, which is 1.41×10 ^-3 Kg/mhcm at 25℃.
It has a value of Hg.

In addition, the moisture permeability coefficient PH ₂ O is calculated as the sum of the component that permeates as water vapor and the component Pl, which is liquid water that aggregates after being adsorbed on the surface of the member, passes through the back surface by capillary action, and vaporizes again, as shown in the following equation. I also found out how to express it.

PH ₂ O=(ε/q ² )・P゜H ₂ O＋Pl ...(2) However, P゜H ₂ O represents the moisture permeability coefficient in air, which is 8.94×10 ^-4 Kg/mhcmHg at 25℃. has value.

From equations (1) and (2) above, if the porosity and curvature of the material are determined, the first terms of the air permeability coefficient and moisture permeability coefficient are determined, and the selective permeability of gas to the material becomes better as Pl increases. I understand. Of the drugs, the water-soluble polymer compound acts to reduce the porosity and increase the tortuosity, and the moisture absorbent acts to increase Pl.

As a result of measuring the flexural index of the material of the fibrous porous member, it was found that the smaller the fiber diameter and the more complex the spatial distribution, the larger the fiber diameter. In addition, Pl is considered to be a function of the water content of the material and capillary force, and it was found that the higher the hygroscopicity and the more closely intertwined the fine fibers, the higher the value. In other words, if you select a material with a narrow fiber diameter and a complex spatial distribution, you can eliminate the need to increase the drug content.
It has become clear that the selective permeability of gas to a moisture-permeable gas shield can be improved.

Based on this knowledge, we have developed a fibrous porous member with a fiber diameter of 5 μm that satisfies the above-mentioned requirements.
We developed a glass fiber mixed paper made by mixing the following glass fibers and cellulose fibers, and impregnated this mixed paper with water-soluble polymeric substances containing moisture absorbers and flame retardants (as necessary) to various contents. As a result of manufacturing a moisture-permeable gas shield and measuring its moisture permeability coefficient and air permeability coefficient, we found that a high degree of gas selective permeability and flame retardance could be achieved even with a low drug content. The invention was completed.

In this invention, the glass fiber preferably has a fiber diameter of 5 μm or less, particularly 0.1 to 5 μm.
A material with a diameter of 1.0 μm is preferable because it has excellent moisture permeability and air permeability. Cellulose fibers include long fiber hemp, kozo,
Cotton fibers or pulp are used.

As the hygroscopic agent, halogen compounds, oxides, salts, hydroxides, hygroscopic substances or polyhydric alcohols, which are generally used as drying agents, can be used, and lithium chloride is particularly suitable.

As the flame retardant, guanidine salts, which are generally used as flame retardants for paper, are used, but guanidine hydrochloride is particularly suitable because it has strong hygroscopicity and also serves as a hygroscopic agent.

As the water-soluble polymer substance, commonly used water-soluble polymer resins, natural resins, or mixtures thereof, such as polyvinyl alcohol resins, polyvinyl methyl ether resins, polyacrylic acid resins, polymethacrylic acid resins, methyl cellulose, etc. are used. . Particularly suitable are polyvinyl alcohol or hydroxyethyl cellulose.

When the fibrous porous member contains a polymeric substance containing a moisture absorbent, an aqueous solution containing 1 to 5% by weight of the moisture absorbent and 5 to 20% by weight of a water-soluble polymeric substance, or 10 to 20% by weight of a flame retardant as necessary. A fibrous porous member is impregnated or coated with this aqueous solution. At this time, it is preferable that the content of these drugs is 10 to 90% by weight based on the fibrous porous member. If the content is less than 10% by weight, the air permeability coefficient will be too high, and if it is more than 90% by weight, it will not only cause problems such as a decrease in the moisture permeability coefficient and the occurrence of drainage at high humidity, but also be difficult to wind during mass production. , which is not preferable because rewinding becomes difficult.

The relationship between tensile strength as an index of mechanical strength of glass fiber mixed paper and glass mixing ratio is shown in Figure 1. Since 1Kg/15mm or more is required in mass production processing, the glass fiber mixing ratio is preferably 80% or less.

The oxygen index (JIS
Figures 2 and 3 show the glass fiber mixing ratio dependence of the test method for which the test method is specified in K7201, respectively. Curve A in Figure 2 is the moisture permeability coefficient under low humidity conditions of 60% relative humidity and curve B is 20% relative humidity.

From FIG. 2, it can be seen that the moisture permeable gas shield having a higher glass fiber mixing ratio is less affected by humidity, and can maintain a high moisture permeability coefficient even under low humidity conditions. Also, the moisture permeability coefficient is 1× at relative humidity of 60%.
A suitable value of 10 ^-4 Kg/mhcmHg or more can be obtained when the glass fiber mixing ratio is 30% or more.

On the other hand, curve A in FIG. 3 is the oxygen index of the above sample, and curve B is the oxygen index of the sample obtained by removing the flame retardant from the chemical. From this, it can be seen that the oxygen index increases rapidly as the paper mixing ratio increases. In the case of curve A, the oxygen index of Nomex sheet, which has excellent flame resistance, is over 30 at a mixing ratio of 10% or more.

As mentioned above, as a result of examining the dependence of various properties of fibrous porous members and moisture permeable gas shields on the glass fiber mixing ratio, it was found that the properties are effective in the range of glass fiber mixing ratio of 10% to 90%, and that the properties are effective in the range of glass fiber mixing ratio of 30% to 80%. % is a particularly preferred characteristic.

In the moisture-permeable gas shield according to the present invention, gases such as air and carbon dioxide are blocked by the thin film of dense polymer material formed between the fibers, making it almost impossible for them to pass through. Since the fibers and thin film have hygroscopic properties, it is adsorbed on their surfaces, aggregates, becomes liquid water, moves through the capillaries existing between the fine fibers by capillary action, and vaporizes on the back surface. Transmitted by. Additionally, the liquid water that fills the capillaries prevents gas from permeating through these capillaries, providing a high degree of gas selective permselectivity. Furthermore, since nonflammable glass fiber is mixed as a material, the overall flame retardance is greatly improved.

This type of gas shield is used, for example, in total heat exchangers for air conditioning equipment, either as is or in layers, but due to its characteristics, fresh air is taken in from the outdoors into the indoors, and fresh air is discharged from the indoors to the outdoors. Heat exchange and the latent heat of water vapor can be performed without mixing with dirty air. This not only increases the heat recovery rate of the total heat exchanger, but also reduces indoor humidity changes, which is extremely beneficial from a sanitary management perspective. In addition, because it has a high degree of flame retardancy, it can meet the provisions of the Fire Service Act and is safe.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the tensile strength of the glass fiber mixed paper that is the material of the moisture permeable gas shield according to the present invention and the glass fiber mixing ratio, and Fig. 2 is a diagram showing the relationship between the moisture permeability coefficient of the gas shield and the glass fiber blending ratio. FIG. 3 is a diagram showing the relationship between the oxygen index of the gas shield and the glass fiber mixing ratio.

Claims (1)

[Scope of Claims] 1 A fibrous porous material made by mixing glass fibers and cellulose fibers with a fiber diameter of 5 μm or less is impregnated or coated with a polymeric substance containing at least a hygroscopic agent among a hygroscopic agent and a flame retardant. A moisture permeable gas shield characterized by containing: 2. The moisture-permeable gas shield according to claim 1, wherein the glass fiber mixing ratio is 10 to 90%. 3. The moisture-permeable gas shield according to claim 1, wherein long-fiber hemp, mulberry, cotton fiber, or wood pulp is used as the cellulose fiber. 4. The moisture-permeable gas shield according to claim 1, wherein lithium chloride is used as the moisture absorbent. 5. The moisture permeable gas shield according to claim 1, which uses guanidine salts as the flame retardant. 6. The moisture-permeable gas shield according to claim 1, in which water-soluble polyvinyl alcohol is used as the polymeric substance.