JP2020134009A - Total heat exchanging element paper and total heat exchanging element - Google Patents

Abstract

To provide a total heat exchanging element paper that is excellent in thermal conductivity, moisture permeability, and paper strength.SOLUTION: A total heat exchanging element paper has beaten cellulose fiber, synthetic fiber and a moisture absorbent. The total heat exchanging element paper contains, as the synthetic fiber, 2-25 mass% of a sheath-core type composite fiber that has a resin with a melting point of 160°C or higher as a core component and polyethylene as a sheath component, with a fiber diameter of 6.0 μm or less.SELECTED DRAWING: None

Description

The present invention is a total heat exchange element of a total heat exchanger that exchanges sensible heat (temperature) and latent heat (humidity) when supplying fresh outside air and discharging dirty air in the room. It relates to total heat exchange element paper used for the element.

In an air-to-air heat exchanger that exchanges heat, the total heat exchange element used in the total heat exchanger that also exchanges latent heat (humidity) as well as visible heat (temperature) sandwiches the total heat exchange element paper. , The supply airflow and the exhaust flow are formed by independent flow paths, and total heat exchange is performed between them. If the room is ventilated with a total heat exchanger provided with such a total heat exchange element, the cooling and heating efficiency can be greatly suppressed.

The total heat exchange element paper needs to have both thermal conductivity and moisture permeability. In order to increase the heat exchange efficiency of sensible heat, it is effective to reduce the thickness of the total heat exchange element paper, and therefore, the basis weight of the paper is reduced or a pressurization treatment such as a super calendar is performed. Further, in order to increase the heat exchange efficiency of latent heat, a moisture absorbent or the like is added to a porous base paper (Japanese paper, kraft paper, etc.) mainly composed of cellulose fibers to impart moisture permeability.

When the basis weight of the total heat exchange element paper is reduced, the number of cellulose fibers constituting the member is reduced, so that the paper strength is further reduced. On the other hand, if the beating process of the cellulose fibers is excessively advanced in order to increase the number of the cellulose fibers, the fiber length of the cellulose fibers becomes short, and there is a problem that the paper strength is rather lowered. In addition, there is a problem that the cellulose fibers are damaged by the pressure treatment of the super calendar or the like, and as a result, the paper strength is lowered.

There are two types of total heat exchange elements, a orthogonal flow type and a countercurrent type, which are manufactured by processing total heat exchange element paper. Both are manufactured using a dedicated machine, but especially in the case of the countercurrent type, the process of attaching a resin frame to secure the flow path for passing indoor and outdoor air to the total heat exchange element paper is is there. An injection molding machine is generally used in this process from the viewpoint of work efficiency. At this time, if the paper strength is insufficient, the total heat exchange element paper is torn by the pressure of the injected resin. Therefore, there is a problem that the total heat exchange element does not function at all.

Patent Document 1 proposes a total heat exchange paper characterized in that the opening diameter on the high humidity air flow side of the total heat exchange element paper is made larger than the opening diameter on the low humidity air flow side. By making a difference in the opening diameters on both sides of the paper, it is expected that the moisture permeability will be improved, but since the paper strength is still insufficient, there is a problem that further improvement is required.

Patent Document 2 proposes a moisture-permeable sheet having a parchment-treated fiber base material and a hygroscopic agent. Since the cellulose fibers of the moisture-permeable sheet are treated with sulfuric acid, the cellulose fibers deteriorate with the passage of time, and sufficient paper strength cannot be maintained. Therefore, there is a problem that further improvement is required. there were.

Japanese Unexamined Patent Publication No. 2013-242130 Japanese Unexamined Patent Publication No. 2016-108704

An object of the present invention is to provide a total heat exchange element paper having excellent thermal conductivity, moisture permeability and paper strength in order to produce a total heat exchange element having excellent total heat exchange efficiency.

As a result of diligent studies to solve the above problems, the following inventions were found.

(1) A total heat exchange element paper containing beaten cellulose fibers, synthetic fibers, and a hygroscopic agent. As the synthetic fibers, a fiber diameter 6 containing a resin having a melting point of 160 ° C. or higher as a core component and polyethylene as a sheath component. A total heat exchange element paper containing 2 to 25% by mass of core-sheath type composite fibers of 0.0 μm or less.

(2) A total heat exchange element according to the above (1), wherein the total heat exchange element paper is used.

Since the total heat exchange element paper of the present invention contains beaten cellulose fibers, specific synthetic fibers, and a hygroscopic agent, it is possible to obtain good total heat exchange element paper having excellent thermal conductivity, moisture permeability, and paper strength. be able to.

The total heat exchange element paper of the present invention contains a beaten cellulose fiber, a synthetic fiber, and a hygroscopic agent, and contains a base paper containing the beaten cellulose fiber and the synthetic fiber, and a hygroscopic agent applied to the base paper. ..

The base paper in the present invention will be described. The base paper in the present invention contains beaten cellulose fibers and synthetic fibers, and is preferably produced by a wet method. As the cellulose fiber, it is preferable to use natural pulp. Natural pulp includes broad-leaved bleached kraft pulp (LBKP), coniferous bleached kraft pulp (NBKP), broad-leaved bleached sulphite pulp (LBSP), coniferous bleached sulphite pulp (NBSP), coniferous unbleached kraft pulp (NUKP), and broad-leaved unbleached kraft pulp. It is preferable to use wood pulp fibers such as bleached kraft pulp (LUKP) individually or in combination. In addition, plant fibers such as cotton, cotton linter, hemp, bamboo, sugar cane, corn, and kenaf; animal fibers such as wool and silk; and cellulose regenerated fibers such as rayon, cupra, and lyocell should be used alone or in combination. You can also.

As an index of beating of cellulose fibers, the freeness specified in JIS P 812-1: 2012 can be applied. In the present invention, the freeness specified in JIS P 812-1: 2012 is not particularly limited, but it is preferable to use cellulose fibers beaten to 60 ° SR or higher. The base paper containing relatively fine cellulose fibers of 60 ° SR or more will form a dense structure while maintaining its affinity with water, and will provide moisture permeability and gas shielding properties, as well as the base paper. The core-sheath type composite fiber contained is uniformly present in the base paper, and as a result, the paper strength is improved.

The total heat exchange element paper of the present invention contains 5 to 15% by mass of core-sheath type composite fibers having a fiber diameter of 6.0 μm or less and having a resin having a melting point of 160 ° C. or higher as a core component and polyethylene as a sheath component as synthetic fibers. It is characterized by that. Hereinafter, unless otherwise specified, "core-sheath-type composite fiber having a resin having a melting point of 160 ° C. or higher as a core component and polyethylene as a sheath component and having a fiber diameter of 6.0 μm or less" is abbreviated as "core-sheath-type composite fiber". In some cases.

In the present invention, the ratio of the core-sheath type composite fiber to the total heat exchange element paper is 2 to 25% by mass, more preferably 5 to 20% by mass, and further preferably 7 to 15% by mass. preferable. When the total heat exchange element paper contains core-sheath type composite fibers, the fusion of the core-sheath type composite fibers strengthens the adhesion points between the fibers, which has the effect of improving the paper strength of the total heat exchange element paper. can get.

When the ratio of the core-sheath type composite fiber is less than 2% by mass, the bonding points between the fibers do not increase, so that the effect of improving the paper strength is not exhibited. Further, when the ratio of the core-sheath type composite fiber is more than 25% by mass, the adhesion points between the fibers increase, but since the core-sheath type composite fiber has a larger fiber diameter than the cellulose fiber, the sheet itself is less likely to be clogged. Therefore, the thermal conductivity may be inferior.

In the present invention, the resin having a melting point of 160 ° C. or higher used as the core component of the core-sheath type composite fiber includes polyester, acrylic, polypropylene, total aromatic polyester, total aromatic polyesteramide, polyamide, semi-aromatic polyamide, and total aromatic. Group polyamide, total aromatic polyether, total aromatic polycarbonate, polyimide, polyamideimide (PAI), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), poly-p-phenylene benzobisoxazole (PBO), polybenzo Examples thereof include resins such as imidazole (PBI), polytetrafluoroethylene (PTFE), and ethylene-vinyl alcohol copolymer.

These core-sheath type composite fibers may be used alone or in combination of two or more types. Among these, polyester, acrylic, polypropylene (PP), total aromatic polyester, total aromatic polyesteramide, polyamide, semi-aromatic polyamide, and total aromatic polyamide are preferable, and polyester, acrylic, and polypropylene are more preferable.

When the melting point of the resin used as the core component is 160 ° C. or higher, the core portion can maintain its shape. The melting point of the resin used as the core component is more preferably 163 ° C. or higher. In the present invention, the melting point is a value measured according to JIS K 7121: 2012.

The melting point of polyethylene as a sheath component is preferably 115 ° C. or higher from the viewpoint of moisture permeability, and 140 ° C. or lower is preferable from the viewpoint of the effect of developing sufficient paper strength.

When the fiber diameter of the core-sheath type composite fiber is 6.0 μm or less, the total heat exchange element paper can be made as thin as desired, and the thermal conductivity can be made sufficient. The fiber diameter of the core-sheath type composite fiber can be measured by observing the cross section of the total heat exchange element paper with a scanning electron microscope.

The total heat exchange element paper of the present invention has heavy calcium carbonate, light calcium carbonate, kaolin, talc, clay, titanium dioxide, aluminum hydroxide in order to obtain the required density, smoothness, air permeability, and strength. , Various fillers such as silica, alumina, and organic pigments, adhesives, sizing agents, fixing agents, yield agents, and various compounding agents such as paper strength enhancers can be appropriately contained.

Examples of the method for producing the base paper in the present invention include a method of forming cellulose fibers and synthetic fibers into a sheet using a general long net paper machine, a round net paper machine, or the like.

The total heat exchange element paper of the present invention may be subjected to a surface size press using a size press, a roll coater, etc. installed in a paper machine in order to obtain the required density, smoothness, air permeability, and strength. Good. The components of the surface size press solution include starch purified from natural plants, hydroxyethylated starch, oxidized starch, etherified starch, phosphoric acid esterified starch, enzyme-modified starch and cold water-soluble starch obtained by flush-drying them. Various synthetic binders such as polyvinyl alcohol can be appropriately used.

The total heat exchange element paper of the present invention may be subjected to calendar processing in order to obtain the required density, smoothness, air permeability, and strength. As the calendar device, a device having one or more combination rolls selected from the group consisting of hard rolls, elastic rolls, and a combination of hard rolls and elastic rolls is preferably used. Specifically, a machine calendar, a soft nip calendar, a super calendar, a multi-stage calendar, a multi-nip calendar, or the like can be used.

The total heat exchange element paper of the present invention is not particularly limited in terms of basis weight, thickness, density, etc., but from the viewpoint of exchange efficiency, it is preferable that the basis weight is low, the thickness is thin, and the density is high. The basis weight is preferably in the range of 20 to 80 g / ^{m 2,} the range of 30~70g / ^{m 2} is more preferable. The thickness is preferably in the range of 20 to 80 μm, more preferably in the range of 30 to 60 μm. Density is preferably in the range of 0.7~1.1g / cm ^3, a range of 0.9~1.1g / cm ³ is more preferable.

A flame retardant can be attached to the total heat exchange element paper of the present invention for the purpose of imparting flame retardancy. Examples of the flame retardant include an inorganic flame retardant, an inorganic phosphorus compound, a nitrogen-containing compound, a chlorine compound, and a bromine compound. For example, a mixture of boric acid and boric acid, aluminum hydroxide, antimony trioxide, ammonium phosphate, ammonium polyphosphate, ammonium sulfamate, guanidine sulfamate, guanidine phosphate, phosphate amide, chlorinated polyolefin, ammonium bromide, Examples thereof include a flame retardant that can be dispersed in an aqueous solution such as a non-ether type polybromocyclic compound or water. As for the level of flame retardancy, it is preferable that the carbonization length measured by JIS A 1322: 1966 is less than 10 cm. The coating weight of the flame retardant is not particularly limited, depending on the flame retardant to be used is preferably in the range of ^{5g / m 2 ~10g / m 2} . More than 10 g / m ² may be attached, but the effect will level off.

An antifungal agent can be attached to the total heat exchange element paper of the present invention for the purpose of imparting antifungal properties. As the fungicide, commercially available fungicide can be generally used. Examples thereof include organic nitrogen compounds, sulfur compounds, organic acid esters, organic iodine imidazole compounds, and benzazole compounds. As the level of antifungal property, it is preferable that the growth of hyphae measured by JIS Z 2911: 2010 is not observed. The adhesion amount of antifungal agent is preferably in the range of ^{0.5g / m 2 ~5g / m 2} . More than 5 g / m ² may be attached, but the effect will level off.

The hygroscopic agent in the total heat exchange element paper of the present invention will be described. The hygroscopic agent is applied or impregnated on the base paper in order to increase the efficiency of heat exchange. Examples of the hygroscopic agent include inorganic acid salts, organic acid salts, inorganic fillers, polyhydric alcohols, ureas, and hygroscopic (water-absorbing) polymers.

For example, the inorganic acid salt includes lithium chloride, calcium chloride, magnesium chloride and the like. Examples of the organic acid salt include sodium lactate, calcium lactate, sodium pyrrolidone carboxylate and the like. Examples of the inorganic filler include aluminum hydroxide, calcium carbonate, aluminum silicate, magnesium silicate, talc, clay, zeolite, diatomaceous earth, sepiolite, silica gel, and activated charcoal. Examples of the polyhydric alcohol include glycerin, ethylene glycol, triethylene glycol, and polyglycerin. Examples of ureas include urea and hydroxyethyl urea.

Examples of the moisture-absorbing (water-absorbing) polymer include polyaspartic acid, polyacrylic acid, polyglutamic acid, polylysine, alginic acid, carboxymethyl cellulose, hydroxyalkyl cellulose and their salts or crosslinked products, carrageenan, pectin, gellan gum, agar, xanthan gum, hyaluron. Acids, guar gum, gum arabic, starch and their crosslinks, polyethylene glycol, polypropylene glycol, collagen, acrylic nitrile polymer saponification, starch / acrylate graft copolymer, vinyl acetate / acrylate copolymer ken Compounds, starch / acrylic nitrile graft copolymer, acrylate / acrylamide copolymer, polyvinyl alcohol / maleic anhydride copolymer, polyethylene oxide-based, isobutylene-maleic anhydride copolymer, polysaccharide / acrylate graft There are self-crosslinked bodies and the like. It is used by selecting the type and the amount of adhesion according to the target moisture permeability.

In the present invention, it is preferable to use one or more hygroscopic agents selected from the group of calcium chloride, lithium chloride and magnesium chloride from the viewpoint of cost and moisture permeability. A particularly preferred hygroscopic agent is calcium chloride. Calcium chloride may be used in combination with other hygroscopic agents.

The amount of the hygroscopic agent attached is not particularly limited. Depending on the type of desiccant to be used, JIS Z 0208: using the evaluation method 1976, 23 ° C., the moisture permeability measured at 50% relative humidity is not less 300g ^/ m 2 · 24h or more preferable. Within this range, a total heat exchange element having excellent wet heat exchange performance can be obtained. The adhesion amount of hygroscopic agent, that depending on the type of desiccant to be used, it is also there, the range of 3g / m ² ~15g / m ² to wet heat exchange performance level off from certain coating weight ^preferably, and more preferably in the range of ^{4g / m 2 ~10g / m 2} . It is preferably in the range of ^{300g / m 2 · 24h~1500g / m} 2 · 24h as moisture ^{permeability,} the range of ^{400g / m 2 · 24h~1000g / m} 2 · 24h , more preferred.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the present examples. Unless otherwise specified, all parts and percentages in the examples are based on mass.

<Breaking pulp>
After decoupling the softwood bleached kraft pulp (NBKP) at a concentration of 3%, the pulp beaten until the freeness of the shopper-rigra method reached 70 ° SR using a double disc refiner was used as beaten pulp.

<Synthetic fiber 1>
Synthetic fiber 1 was a core-sheath type composite fiber having a core component of polypropylene resin (melting point 160 ° C.) and a sheath component of polyethylene resin, having a fiber diameter of 5.2 μm and a fiber length of 3 mm.

<Synthetic fiber 2>
Synthetic fiber 2 was a core-sheath type composite fiber having a core component of polypropylene resin (melting point 160 ° C.) and a sheath component of polyethylene resin, having a fiber diameter of 10.4 μm and a fiber length of 5 mm.

<Synthetic fiber 3>
A single fiber made of polypropylene resin having a fiber diameter of 3.9 μm and a fiber length of 3 mm was designated as synthetic fiber 3.

<Synthetic fiber 4>
Synthetic fiber 4 is a core-sheath type composite fiber having a fiber diameter of 2.4 μm and a fiber length of 3 mm in which the core component is a polyester resin (melting point 255 ° C., PET) and the sheath component is a modified polyester resin (melting point 110 ° C., modified PET). ..

The total heat exchange element papers of Examples 1 to 3 and Comparative Examples 1 to 6 were produced by the following steps.

(Preparation of total heat exchange element papers of Examples 1 to 3 and Comparative Examples 1 to 6)
After pouring water into a 2 m ³ dispersion tank, the beaten pulp and synthetic fibers that had been sufficiently dissociated were mixed so as to have the blending ratio shown in Table 1, and dispersed at a dispersion concentration of 0.2% for 5 minutes. The paper was made with a net paper machine to obtain base paper for the total heat exchange element papers of Examples 1 to 3 and Comparative Examples 1 to 6 having a basis weight of 35 g / m ² . Lithium chloride was added to the base paper as a hygroscopic agent by an impregnation processing machine so as to have the addition ratio to the base paper shown in Table 1. After that, calendar processing was performed to obtain total heat exchange element papers of Examples 1 to 3 and Comparative Examples 1 to 6 having a thickness of 32 μm.

The total heat exchange element papers of Examples 1 to 3 and Comparative Examples 1 to 6 obtained as described above were measured and evaluated for the following items.

(Humidity permeability)
The moisture permeability was measured under the conditions of a temperature of 20 ° C. and a relative humidity of 65% according to the moisture permeability test method specified in JIS Z 0208: 1976.

(Thermal conductivity)
The total heat exchange element paper is set vertically in a room having a temperature of 20 ° C., irradiated with an infrared lamp (500 W) from a distance of 30 cm on the surface side thereof, and the surface temperature of the total heat exchange element paper 10 minutes after the start of measurement. And the backside temperature was measured with an infrared radiation thermometer.

〇: The temperature difference between the front surface and the back surface is less than 5 ° C, and the thermal conductivity is excellent. Δ: The temperature difference between the front surface and the back surface is 5 to 10 ° C, and the thermal conductivity is slightly excellent. The temperature difference from the back surface is over 10 ° C, and the thermal conductivity is inferior.

(Tensile strength)
With respect to the produced total heat exchange element paper, the tensile strength in the vertical direction was measured using a desktop material tester (manufactured by Orientec Co., Ltd., trade name STA-116750) according to JIS P 8113: 2006. The size of the test piece was 250 mm in the vertical direction and 50 mm in width, the distance between the two grippers was 100 mm, and the tensile speed was 200 mm / min.

◯: Tensile strength is 1000 N / m or more and paper strength is excellent Δ: Tensile strength is 400 N / m or more and less than 1000 N / m and paper strength is slightly excellent ×: Tensile strength is less than 400 n / m , Paper strength is inferior

From Table 2, it was confirmed that the total heat exchange element paper of the example was not only excellent in moisture permeability and thermal conductivity, but also in paper strength. On the other hand, none of the total heat exchange element papers of the comparative example was excellent in all of the moisture permeability, thermal conductivity and paper strength.

Comparing Example 1 and Comparative Example 1, since Comparative Example 1 uses a core-sheath type composite fiber having a fiber diameter of 6.0 μm or more, Example 1 has better tensile strength. I understand. Comparing Example 1 and Comparative Example 2, since Comparative Example 2 uses a single fiber made of only polypropylene resin, Example 1 has better tensile strength, and Comparative Example 2 has better tensile strength. moisture permeability is understood to be inferior and 900g ^/ m 2 · 24h. Comparing Example 1 and Comparative Example 3, since Comparative Example 3 uses a core-sheath type composite fiber in which the core component is a polyester resin and the sheath component is a modified polyester resin, the tensile strength of Example 1 is higher. is good, also it can be seen that the moisture permeability of Comparative example 3 is inferior and 800g ^/ m 2 · 24h. Comparing Example 1 and Comparative Example 4, Comparative Example 4 does not use the core-sheath type composite fiber of the present invention and contains only beaten pulp as a fiber component, so that Example 1 is more tensile. It can be seen that the strength is good. Comparing Example 1 and Comparative Example 5, it can be seen that the total heat exchange element paper of Comparative Example 5 does not contain a hygroscopic agent, so that Example 1 has better moisture permeability. Comparing Example 3 and Comparative Example 6, since the total heat exchange element paper of Comparative Example 6 has a core-sheath type composite fiber content of more than 25% by mass, the moisture permeability and heat conduction of Example 3 are higher. It can be seen that the sex is good.

Based on these facts, it is a total heat exchange element paper containing a beaten cellulose fiber, a synthetic fiber, and a hygroscopic agent, and the synthetic fiber is a fiber having a resin having a melting point of 160 ° C. or higher as a core component and polyethylene as a sheath component. It was confirmed that the total heat exchange element paper containing 2 to 25% by mass of core-sheath type composite fibers having a diameter of 6.0 μm or less is excellent in thermal conductivity, moisture permeability, and paper strength and is effective.

The total heat exchange element paper of the present invention is a total heat exchange element of a total heat exchanger that supplies fresh outside air and exchanges latent heat (humidity) with sensible heat (temperature) when discharging dirty air in the room. Used for.

Claims (2)

A total heat exchange element paper containing a beaten cellulose fiber, a synthetic fiber, and a hygroscopic agent. The synthetic fiber has a fiber diameter of 6.0 μm or less, which contains a resin having a melting point of 160 ° C. or higher as a core component and polyethylene as a sheath component. A total heat exchange element paper containing 2 to 25% by mass of core-sheath type composite fibers. A total heat exchange element according to claim 1, wherein the total heat exchange element paper is used.