JPS60251903A - Total heat exchange element - Google Patents

Abstract

PURPOSE:To obtain a total heat exchange element excellent in moisture permeability and gas barrier property, by using a moisture permeable film based on modified polyvinyl alcohol containing alkali metal carboxylate as a bonding group. CONSTITUTION:A hydroscopic substance such as LiCl2 is compounded with a solution of modified polyvinyl alcohol containing alkali metal carboxylate as a bonding group, which is prepared, for example, by copolymerizing acrylic acid with the high-molecular chain of polyvinyl alcohol and bonding an alkali metal to the carboxyl group of said acrylic acid to form a salt, in a solvent mixture of acetone/methanol. This is applied to a porous sheet such as base paper and dried. Thus obtained total heat exchange element has a good gas barrier property because modified polyvinyl alcohol has excellent film forming capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the invention Industrial field of application The present invention relates to a total heat exchanger. Recently, heat exchangers have come to be used as ventilation systems in homes and buildings.
In particular, total heat exchangers that perform not only sensible heat exchange but also latent heat exchange at the same time are becoming increasingly popular as extremely useful devices.

This total heat exchange is achieved by partitioning the two types of air streams to be heat exchanged by an element having thermal conductivity and moisture permeability. The present invention relates to this total heat exchange element.

Prior art As a conventional total heat exchange element, for example, the Japanese Patent Publication No. 52-15
As in Japanese Patent Publication No. 071, an air-permeable porous object is impregnated with or coated with a water-soluble polymer to which lithium halide is added, and as in Japanese Patent Publication No. 10214/1984, a hydrophilic polymer film is used alone. Thing, Japanese Unexamined Patent Publication No. 54-227
Polyviny 7 with a degree of polymerization of 1000 to 2ooo as disclosed in Publication No. 7
・An example is one in which a moisture absorbent is blended with real alcohol and impregnated or applied to the hydrophilic porous portion 4.
.

Problems to be solved by invention Many of these conventional technologies utilize water-soluble polymers such as polyvinyl alcohol, but this 7]! Even if lithium chloride, which is a hygroscopic substance, is added to libinyl alcohol, its moisture permeability is sufficiently improved; however, since the moisture permeability of libinyl alcohol itself is low, no substantial improvement can be expected by simply adding additives. It has become a thing. For example, a polyvinyl alcohol film with a saponification degree of 99 has a moisture permeability of 100 to 400 g/door/24 hours (40°0 RHO%/] RH 90%), and the saponification degree has decreased to 88. However, under the same measurement conditions, it has a value of 600~'foog/rd・24 hours, and has good moisture permeability.
There is a need for a modified polyvinyl alcohol having a moisture permeability of 0.00 g/z pi/24 hours.

Furthermore, when polyvinyl alcohol is processed into a porous sheet, it easily permeates into the sheet, resulting in a low film-forming ability and a major drawback in that gas barrier properties tend to deteriorate.

The present invention uses a film whose main component is modified polyvinyl alcohol, which has essentially improved the moisture permeability and film-forming ability of polyvinyl alcohol. ) is intended to provide a total heat exchange element that is also excellent.

Structure of the Invention The gist of the present invention is a total heat exchange element comprising a moisture-permeable film mainly composed of modified polyvinyl alcohol containing an alkali metal carboxylic acid salt as a bonding group. The modified polyvinyl alcohol has a degree of saponification in the range of 85 to 95%, and if necessary, a hygroscopic substance is blended with the modified polyvinyl alcohol, which is particularly suitable as a practical example. It is something that can be done.

Means to Solve the Intermediate Problem As mentioned above, there is a limit to the improvement of the moisture permeability of ordinary polyvinyl alcohol-based moisture permeable films, no matter how much you consider the additives and compounding agents. Since it was judged that it was necessary to improve the low gas barrier properties due to the ease with which it permeates into the sheet, we attempted to use various modified polyvinyl alcohols.

As a result, the modified polyvinyl alcohol containing an alkali metal carboxylic acid salt as a bonding group has excellent moisture permeability and excellent film-forming ability, so it has good gas barrier properties and Exchange element and 1.
I found it to be very useful and decided to do it.

This modified polyvinyl alcohol containing an alkali metal carboxylic acid salt as a bonding group is an example in which acrylic acid is copolymerized into the polymer chain of habovinyl alcohol, and 7) V is added to the carboxylic acid group of Examples include salt-forming bonds of metals. 1 -C in a polymer whose main component is polyvinyl alcohol! 0ON
A, -000, etc. contain bonding groups.

In the present invention, the amount of bonding with 100ONa is preferably 1 to 5 mole based on the hydroxyl group of polyvinyl alcohol, and if the amount of bonding increases by 1, water resistance decreases, causing problems in water resistant adhesion, etc. It is coming. On the other hand, if the amount of bonding is too small, no improvement in moisture permeability or film-forming ability can be expected.

The film made of modified polyvinyl alcohol produced by Ming Tono Kihashi has a moisture permeability of about 950 to 1000 under the same conditions as the moisture permeability measurement of normal polyvinyl alcohol mentioned above.
1100 g/y? ?・It has excellent moisture permeability for 24 hours.

The effect is particularly good when the degree of saponification of the modified polyvinyl alcohol in the present invention is 85 to 95%. In addition, it is preferable to add 5 to 20 parts of a water-soluble crosslinking agent such as melamine resin to the modified polyvinyl alcohol in order to improve the water-resistant adhesion of the moisture-permeable film of the present invention. It will be effective.

The moisture permeability of the device of the present invention can be improved simply by using this modified polyvinyl alcohol, but when a hygroscopic substance such as lithium chloride is blended with this modified polyvinyl alcohol, it exhibits even more suitable moisture permeability and is extremely excellent. This serves as a total heat exchange element.

There is no need to limit the amount of this hygroscopic substance, but
Normally, the solid content ratio is 10 to 10% in modified polyvinyl alcohol.
A suitable result can be obtained by adding 30 parts.

The device of the present invention is made by blending the above-mentioned hygroscopic substance with the above-mentioned water-soluble solvent solution of modified polyvinyl alcohol, coating the viscous liquid with the above-mentioned polyvinyl alcohol, and drying it to form a moisture-permeable film. In this case, a porous sheet such as base paper is treated to form a moisture-permeable film, and the resulting film is used in one piece. In addition, in the present invention, there is less penetration into porous sheets and better film-forming ability compared to conventional polyvinyl alcohol-based sheets, so there is no performance deterioration factor due to coating processing on this base paper etc. Therefore, it is particularly suitable to use it in combination with this base paper or the like.

For example, when a base paper with a size degree of 300 seconds is treated with one-component polyvinyl alcohol, a total heat exchange element with extremely excellent moisture permeability and gas barrier properties can be obtained with a small amount of coating, and a high total heat This indicates exchangeability.

Function The present invention is constructed as described above, and the moisture permeability and film-forming ability of the modified polyvinyl alcohol itself as a base material are greatly improved compared to conventional ordinary polyvinyl alcohol. By limiting the degree of saponification of polyvinyl alcohol to an appropriate range and adding a hygroscopic substance, its properties can be further improved, and a moisture-permeable film with these excellent properties can be formed on a porous sheet. If such a material is used as a total heat exchange element, both moisture permeability and gas barrier properties, which are the most important physical properties for a total heat exchange element, will be extremely high.

Example 1 Contains 3 molar groups of sodium carboxylate and has saponification degree of 9
In a solution of 3% modified lid polyvinyl alcohol (Nippon Reisei Kagaku Shigego-76-L T-350) dissolved in a mixed solvent of 1-1-ygo-7-methanol and 10 parts, lithium chloride was added to the solid content ratio of 80 to 80 of the former. This solution was applied to a base paper with a size degree of 300 seconds at a rate of 5 g/
nf was coated and dried at 20°C to obtain a sample.

Example 2 The same liquid mixture as in Example 1 was coated on the same base paper as in Example 1 to a coating weight of 4 g/nf and dried in the same manner to obtain a test piece.

Comparison side 1 To a solution of polyvinyl alcohol with a saponification degree of 99 dissolved in the same solvent as in Example 1, lithium chloride was blended at a solid content ratio of 20 to 80 of the former, and this solution was
A test piece was prepared by coating the same base paper as in Example 1 to a coating weight of 6 g/m and drying.

Comparative Example 2 Comparative Example] and [Comparative Example] and [Adhesion amount 5 p;
/77/ and dried to obtain a test piece.

Comparative Example 3 Using the same formulation as in Comparative Example 1, the adhesion amount was 4, g/
A test piece was prepared by coating and drying.

For each of the above test pieces, a total heat exchanger that exchanges total heat through the bellows-type partition surface was manufactured, and RH62 and 32
Counter-flow total heat exchange was carried out between outside air at RH 40°C and indoor air at RH 40°C, and the total heat exchange efficiency and carbon dioxide transfer rate (gas transferability) were measured, and the results shown in the following table were obtained. It was done.

From this table, both Examples have high total heat exchange efficiency and very good gas barrier properties, but in Comparative Example, the total heat exchange efficiency decreases and the amount of deposition decreases. When the amount decreases, the gas barrier properties deteriorate significantly. The comparative example has a slight drawback in that it is impossible to increase both the total heat exchange efficiency and the gas barrier property, but in the example according to the present invention, it is possible to increase both of them. ing.

C. Effects of the Invention As explained in detail above, the device of the present invention is made of a moisture-permeable film obtained by using modified polyvinyl alcohol having extremely high characteristics and blending a hygroscopic substance as necessary, It has excellent moisture permeability, gas/resistivity, and very suitable total heat exchange performance, making it highly useful as a total heat exchange element.

Claims (1)

[Scope of Claims] 1. A total heat exchange element comprising a moisture permeable film whose main component is modified polyvinyl alcohol containing an alkali metal carboxylic acid salt as a bonding group. 2. Saponification degree of modified polyvinyl alcohol 85-95
A total heat exchange element according to claim 1, which is the scope of the present invention. 3. The total heat exchange element according to claim 1 or 2, wherein a hygroscopic substance is blended as an additive in the modified polyvinyl alcohol. 4. The total heat exchange element according to claim 1, wherein a moisture permeable film is provided on the porous sheet.