JP7400160B2 - Total heat exchange element paper - Google Patents

Description

The present invention relates to a total heat exchange element paper used in a ventilation heat exchanger that exchanges both sensible heat and latent heat in a heat exchange ventilation device with a laminated structure used in the air conditioning field.

BACKGROUND ART In recent years, with the spread of air conditioning equipment such as air conditioners and heaters, ventilation heat exchangers that can recover temperature and humidity by exchanging heat between supply air and exhaust air during ventilation have been used.
This heat exchanger consists of a flat partition plate that has heat conductivity and moisture permeability, and a spacer plate that is sandwiched between the two partition plates to ensure an air flow path, and the partition plates and spacer plates are stacked in multiple layers. It has a basic structure. The spacing plate is a corrugated plate formed into a sawtooth or sinusoidal waveform, and is sandwiched between the partition plates with the direction of the waveform formed alternately in the orthogonal direction. As a result, two systems of fluid passages are configured to alternately intersect at right angles every other layer between each layer constituted by the spacing plate and the partition plate.

The partition plate separates the air supply path that brings fresh air from outside into the room and the exhaust path that exhausts dirty indoor air outside, allowing heat exchange of both sensible heat and latent heat between the air supply and exhaust air. It has the function of For this reason, the partition plate is required to have heat conductivity and water vapor permeability as indicated by moisture permeability, flame retardancy, and air shielding ability to prevent supply air and exhaust air from mixing.

Total heat exchange element paper is used as a material for partition plates that can meet such requirements, and the applicant of the present application has disclosed in Patent Document 1 that paper is being used as a total heat exchange element paper with high moisture absorption and desorption properties and air shielding properties. We are proposing a total heat exchange element paper containing fibers for use in the manufacturing process, a moisture absorbent, and cellulose nanofibers.

International Publication No. 2018/003492

As a total heat exchange element paper, a porous base material made of papermaking fibers that is not subjected to high beating as described in Patent Document 1 is coated or impregnated with a solution of cellulose nanofibers and a moisture absorbent (hereinafter referred to in particular). Unless otherwise specified, "coated" is used to include "impregnated"), the total heat exchange element paper has a coating layer with fine voids formed by fine cellulose nanofibers, which reduces moisture permeability. It is possible to increase the air permeability resistance without causing any damage.
In order to coat a mixed solution of cellulose nanofibers and a moisture absorbent at once and obtain paper with high air permeation resistance that lasts for more than tens of thousands of seconds, it is necessary to increase the amount of the mixed solution applied. However, there is a problem in that not only does the moisture permeation performance deteriorate due to an increase in the thickness of the coating layer and the length of the moisture permeation path, but also a significant increase in cost due to the increase in the amount of expensive cellulose nanofibers.

An object of the present invention is to provide a total heat exchange element paper that has high production efficiency during paper making and coating, and has high moisture permeability and air shielding properties in both high-humidity and low-humidity environments.

The present inventors have discovered that when a large amount of alkali metal salt or alkaline earth metal salt is added as a hygroscopic agent to an aqueous dispersion of cellulose nanofibers that have been chemically modified such as carboxymethylation or carboxylation, they cause aggregation and absorption. The dispersibility of cellulose nanofibers contained in the mixed solution tends to decrease due to the formation of liquid gel, and when a mixed solution with reduced dispersibility of cellulose nanofibers is applied to a porous substrate and dried, moisture permeability increases. It was confirmed that there was almost no increase in the air permeability resistance. In addition, a mixture of an aqueous solution of a water-soluble polymer such as a carboxymethylcellulose salt and an alkali metal salt or an alkaline earth metal salt does not cause aggregation or liquid-absorbing gel, and when this mixture is applied to a porous substrate. It was confirmed that while the air permeability resistance increased significantly when the material was washed and dried, the moisture permeability tended to decrease.

Based on the above two findings, as a result of intensive studies on means to solve the problems of the present invention, we found that a coating layer containing a combination of cellulose nanofibers and a water-soluble polymer and a moisture absorbent added thereto was applied to a porous base material. The present invention was completed based on the discovery that a total heat exchange element paper having high air permeability and excellent moisture permeability, especially in a low humidity environment, can be obtained by providing a total heat exchange element paper with an unexpectedly high moisture permeability.

That is, the means for solving the problems of the present invention are as follows.
1. A total heat exchange element paper containing paper-making fibers, cellulose nanofibers, a moisture absorbent, and a water-soluble polymer, and having an air permeability resistance of 10,000 seconds or more.
2. The papermaking fiber is a cellulose fiber,
1. The water-soluble polymer is a carboxyalkyl cellulose salt. Total heat exchange element paper described in .
3. 1. The cellulose nanofiber is at least one of carboxymethylated cellulose nanofibers, carboxylated cellulose nanofibers, cationized cellulose nanofibers, and esterified cellulose nanofibers. or 2. Total heat exchange element paper described in .
4. 1. The moisture absorbent is calcium chloride. ~3. Total heat exchange element paper according to any of the above.
5. 1. Basis weight is 10 g/m ² or more and 40 g/m ² or less. ~4. Total heat exchange element paper according to any of the above.
6. The moisture permeability measured using a measuring instrument according to JIS Z0208 and using magnesium chloride hexahydrate as the moisture absorbing agent under high humidity environmental conditions of 25°C and 75% relative humidity is 1300 g/m ² 24 hours or more. 1. Using lithium chloride as a moisture absorbent, the moisture permeability measured under low humidity environmental conditions of 25° C. and 35% relative humidity is 550 g/m ² ·24 h or more. ~5. Total heat exchange element paper according to any of the above.
7. A method for producing total heat exchange element paper, which comprises coating at least one side of a base paper containing paper-making fibers with a chemical solution containing a moisture absorbent, cellulose nanofibers, and a water-soluble polymer.

The total heat exchange element paper of the present invention has excellent air shielding properties by providing a porous base material with a coating layer containing cellulose nanofibers, a water-soluble polymer, and a moisture absorbent. Further, the total heat exchange element paper of the present invention is characterized in that it exhibits particularly excellent moisture permeability not only in high humidity environments but also in low humidity environments. Therefore, it can be used under a wide range of environments, from high-humidity summer conditions to low-humidity winter conditions and air-conditioning conditions.

The total heat exchange element paper of the present invention has a thin coating layer made of cellulose nanofibers, a water-soluble polymer, and a moisture absorbent that performs most of the air-shielding properties and moisture permeability that conventionally were provided by thick base papers. As a result, even if a thin base paper with a small basis weight is used, high air shielding properties and moisture permeability can be maintained, and the heat exchanger can be made smaller and lighter. Furthermore, since the coating layer containing cellulose nanofibers, water-soluble polymer, and moisture absorbent can be applied in one step, production efficiency can be increased and costs can be reduced.

The total heat exchange element paper of the present invention contains paper-making fibers, cellulose nanofibers, a moisture absorbent, and a water-soluble polymer, and is characterized by having an air permeability resistance of 10,000 seconds or more.
This total heat exchange element paper is manufactured by coating at least one side of a base paper containing papermaking fibers with a chemical solution containing cellulose nanofibers, a moisture absorbent, and a water-soluble polymer.
Embodiments of the present invention will be described in detail below.

(1) Fiber for paper manufacturing The fiber for paper manufacturing used as a raw material for the total heat exchange element paper of the present invention is obtained from wood pulp such as softwood pulp and hardwood pulp, and non-wood raw materials such as flax, abaca, kenaf, bamboo, and bagasse. Examples include cellulose fibers obtained from non-wood pulp and the like. The method of cooking cellulose fibers, whether or not to bleach them, and the method of bleaching are not particularly limited. In addition to cellulose fibers, synthetic fibers or semi-synthetic fibers such as polyester fibers, nylon fibers, rayon fibers, and lyocell fibers can be blended for the purpose of improving adhesion, dimensional stability, and shapeability.

The pulp used in the present invention is refined to a freeness of 68°SR or more and 78°SR or less using the modified Schopper-Riegler method (according to P 8121-1:2012, except that the amount of pulp collected was 0.5g). However, it is more preferably used after being beaten to a range of 69°SR or more and 75°SR or less. Irregular Schopper Riegler method When the freeness exceeds 78°SR, the paper web becomes dense and there are fewer voids, making it difficult for chemical solutions to penetrate into the paper when used as a base paper for total heat exchange element paper. This is undesirable because problems such as hygroscopic agents and the like being localized on the surface of the base paper may cause blocking, and the amount of expansion and contraction due to changes in humidity may increase. In addition, when the irregular Shopper Riegler method freeness is less than 68°SR, the amount of voids and the void diameter of the paper web increase, and the air shielding effect of the cellulose nanofibers may become insufficient. For beating the pulp, general beating devices such as beaters and refiners can be used, and there are no particular restrictions on the beating device or the beating method.

The paper stock for papermaking is made by blending synthetic or semi-synthetic fibers, fillers, colorants, paper strength enhancers, wet paper strength enhancers, band sulfate, cationized starch, retention improvers, etc. to the above-mentioned beaten pulp as necessary. It is prepared by

The paper stock mentioned above is made by a general paper making method using a fourdrinier paper machine, cylinder paper machine, short wire paper machine, twin wire paper machine, or a paper machine that combines these. There are no particular restrictions on the paper making method. In addition, if necessary, impregnate flame retardant, rust preventive agent, anti-blocking agent, etc. with on-machine coating equipment such as size press or roll coater, and perform calender treatment with machine calender, super calender, soft nip calender, etc. Then, the base paper is obtained.

The air permeability resistance of the base paper is improved by the sealing effect of the chemical solution applied to the base paper, but in order to fully demonstrate its effect, the air permeation resistance of the base paper itself is preferably increased for 50 seconds or more and 2000 seconds. Hereinafter, the time period is more preferably 600 seconds or more and 1800 seconds or less, and even more preferably 800 seconds or more and 1500 seconds or less. If the air permeability resistance of the base paper is less than 50 seconds, even if cellulose nanofibers are added, the increase in air permeability after addition is small, and the air shielding properties of the total heat exchange element paper may be insufficient. When the air permeability resistance of the base paper exceeds 2000 seconds, it becomes difficult for the applied chemical solution to penetrate into the inside of the base paper, and blocking due to chemical components near the surface of the base paper may easily occur. The air permeability resistance of the base paper can be adjusted using ordinary papermaking techniques by changing the degree of beating of the pulp blended as papermaking fibers and the basis weight of the base paper.

The total heat exchange element paper of the present invention can exhibit high air shielding properties due to the excellent sealing effect of the chemical solution containing cellulose nanofibers, moisture absorbers, and water-soluble polymers, so it can be used as a base paper with a small basis weight. Can be used. Specifically, the basis weight of the base paper used in the present invention is preferably 8 g/m ² or more and 30 g/m ² or less, more preferably 9 g/m ² or more and 25 g/m ² or less, It is more preferably 10 g/m ² or more and 20 g/m ² or less.

(2) Cellulose Nanofiber Cellulose nanofiber (hereinafter also referred to as CNF) is a fine fiber obtained by subjecting a cellulose raw material to a chemical modification treatment if necessary and then to a fibrillation treatment. The average fiber diameter of CNF is usually about 3 nm or more and 500 nm or less. The average fiber diameter and average fiber length of CNFs were randomly selected using atomic force microscopy (AFM) if the diameter was less than 20 nm, and field emission scanning electron microscopy (FE-SEM) if the diameter was 20 nm or more. It can be obtained by analyzing 200 fibers and calculating the average.
The average aspect ratio of CNF is usually 10 or more. The upper limit is not particularly limited, but is usually 1000 or less. The average aspect ratio can be calculated using the following formula.
Average aspect ratio = average fiber length / average fiber diameter

(2-1) Cellulose raw material The origin of the cellulose raw material, which is the raw material for CNF, is not particularly limited, but includes, for example, plants (for example, wood, bamboo, hemp, jute, kenaf, agricultural residues, cloth, pulp (coniferous unbleached Kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP), Examples include thermomechanical pulp (TMP), recycled pulp, waste paper, etc.), animals (eg, ascidians), algae, and microorganisms (eg, acetic acid bacteria). The cellulose raw material used in the present invention may be any one of these or a combination of two or more types, but is preferably a cellulose raw material derived from plants or microorganisms (e.g., cellulose fiber), and more preferably is a plant-derived cellulose raw material (eg, cellulose fiber).
The number average fiber diameter of the cellulose raw material is not particularly limited, but in the case of softwood kraft pulp, which is a common pulp, it is about 30 μm or more and 60 μm or less, and in the case of hardwood kraft pulp, it is about 10 μm or more and 30 μm or less. In the case of other pulps, those that have undergone general refining have a diameter of about 50 μm. For example, in the case of refined chips or the like that are several centimeters in size, it is preferable to mechanically process them using a disintegrator such as a refiner or a beater to adjust the size to about 50 μm.

(2-2) Modification Cellulose raw materials have three hydroxyl groups per glucose unit, and can be subjected to various chemical modification treatments. In the present invention, these may or may not be modified, but it is better to chemically modify the fibers so that the fibers become finer and uniform in length and diameter. It will be done.
Modification methods for modifying cellulose raw materials are not particularly limited, but include chemical modifications such as oxidation (carboxylation), etherification (carboxymethylation), cationization, esterification, phosphorylation, silane coupling, and fluorination. can be mentioned. Among these, oxidation (carboxylation), etherification (carboxymethylation), cationization, and esterification are preferred, and detailed methods thereof will be described below.

(2-2-1) Oxidized (carboxylated) cellulose nanofibers When modifying cellulose raw materials by oxidation, the amount of carboxyl groups based on the absolute dry weight of the resulting oxidized cellulose or cellulose nanofibers is preferably 0.5 mmol/g. Above, it is more preferably 0.8 mmol/g or more, still more preferably 1.0 mmol/g or more. The upper limit is preferably 3.0 mmol/g or less, more preferably 2.5 mmol/g or less, even more preferably 2.0 mmol/g or less. Therefore, it is preferably 0.5 mmol/g or more and 3.0 mmol/g or less, more preferably 0.8 mmol/g or more and 2.5 mmol/g or less, and even more preferably 1.0 mmol/g or more and 2.0 mmol/g or less.
The method of oxidation is not particularly limited, but one example is to oxidize cellulose in water using an oxidizing agent in the presence of an N-oxyl compound and a substance selected from the group consisting of bromides, iodides, or mixtures thereof. Examples include methods of oxidizing raw materials. According to this method, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized to produce a group selected from the group consisting of aldehyde groups, carboxyl groups, and carboxylate groups. The concentration of the cellulose raw material during the reaction is not particularly limited, but is preferably 5% by weight or less.

The N-oxyl compound refers to a compound capable of generating nitroxy radicals. Examples of nitroxy radicals include 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO). As the N-oxyl compound, any compound can be used as long as it promotes the desired oxidation reaction.
The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount that can oxidize cellulose as a raw material. For example, it is preferably 0.01 mmol or more, more preferably 0.02 mmol or more, per 1 g of bone dry cellulose. The upper limit is preferably 10 mmol or less, more preferably 1 mmol or less, and even more preferably 0.5 mmol or less. Therefore, the amount of the N-oxyl compound used is preferably 0.01 mmol or more and 10 mmol or less, more preferably 0.01 mmol or more and 1 mmol or less, and even more preferably 0.02 mmol or more and 0.5 mmol or less, per 1 g of bone-dry cellulose.

Bromide is a compound containing bromine, and includes, for example, an alkali metal bromide that can be dissociated and ionized in water, such as sodium bromide. Moreover, iodide is a compound containing iodine, and includes, for example, alkali metal iodide. The amount of bromide or iodide used may be selected within a range that can promote the oxidation reaction. The total amount of bromide and iodide is preferably 0.1 mmol or more, more preferably 0.5 mmol or more, per 1 g of bone-dry cellulose. The upper limit is preferably 100 mmol or less, more preferably 10 mmol or less, and even more preferably 5 mmol or less. Therefore, the total amount of bromide and iodide is preferably 0.1 mmol or more and 100 mmol or less, more preferably 0.1 mmol or more and 10 mmol or less, and even more preferably 0.5 mmol or more and 5 mmol or less, per 1 g of bone-dry cellulose.

Examples of the oxidizing agent include, but are not limited to, halogen, hypohalous acid, halous acid, perhalogenic acid, salts thereof, halogen oxides, peroxides, and the like. Among these, hypohalous acid or its salt is preferred, hypochlorous acid or its salt is more preferred, and sodium hypochlorite is even more preferred because it is inexpensive and has little environmental impact. The amount of the oxidizing agent used is preferably 0.5 mmol or more, more preferably 1 mmol or more, and even more preferably 3 mmol or more, per 1 g of bone-dry cellulose. The upper limit is preferably 500 mmol or less, more preferably 50 mmol or less, even more preferably 25 mmol or less, and most preferably 10 mmol or less. Therefore, the amount of the oxidizing agent used is preferably 0.5 mmol or more and 500 mmol or less, more preferably 0.5 mmol or more and 50 mmol or less, even more preferably 1 mmol or more and 25 mmol or less, and most preferably 3 mmol or more and 10 mmol or less, per 1 g of bone-dry cellulose. preferable. When using an N-oxyl compound, the amount of the oxidizing agent used is preferably 1 mol or more per 1 mol of the N-oxyl compound. The upper limit is preferably 40 mol or less. Therefore, the amount of the oxidizing agent used is preferably 1 mol or more and 40 mol or less per 1 mol of the N-oxyl compound.

Conditions such as pH and temperature during the oxidation reaction are not particularly limited, and the oxidation reaction generally proceeds efficiently even under relatively mild conditions. The reaction temperature is preferably 4°C or higher, more preferably 15°C or higher. The upper limit is preferably 40°C or less, more preferably 30°C or less. Therefore, the temperature is preferably 4° C. or higher and 40° C. or lower, and may be 15° C. or higher and 30° C. or lower, that is, room temperature. The pH of the reaction solution is preferably 8 or higher, more preferably 10 or higher. The upper limit is preferably 12 or less, more preferably 11 or less. Therefore, the pH of the reaction solution is preferably about 8 or more and 12 or less, more preferably about 10 or more and 11 or less. Usually, as carboxyl groups are generated in cellulose as the oxidation reaction progresses, the pH of the reaction solution tends to decrease. Therefore, in order to allow the oxidation reaction to proceed efficiently, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution within the above range. Water is preferable as the reaction medium for oxidation because it is easy to handle and does not easily cause side reactions.

The reaction time for oxidation can be appropriately set according to the degree of progress of oxidation, and is usually 0.5 hours or more. The upper limit is usually 6 hours or less, preferably 4 hours or less. Therefore, the reaction time for oxidation is usually 0.5 hours or more and 6 hours or less, for example 0.5 hours or more and 4 hours or less.
The oxidation may be carried out in two or more reaction steps. For example, by oxidizing the oxidized cellulose obtained by filtration after the completion of the first-stage reaction again under the same or different reaction conditions, the efficiency can be improved without being inhibited by the salt produced as a by-product in the first-stage reaction. Can be oxidized well.

Another example of the carboxylation (oxidation) method is a method of oxidizing by ozone treatment. This oxidation reaction oxidizes at least the 2- and 6-position hydroxyl groups of the glucopyranose rings constituting cellulose, and causes decomposition of the cellulose chain. Ozone treatment is usually performed by bringing a gas containing ozone into contact with the cellulose raw material. The ozone concentration in the gas is preferably 50 g/m ³ or more. The upper limit is preferably 250 g/m ³ or less, more preferably 220 g/m ³ or less. Therefore, the ozone concentration in the gas is preferably 50 g/m ³ or more and 250 g/m ³ or less, more preferably 50 g/m ³ or more and 220 g/m ³ or less. The amount of ozone added is preferably 0.1% by weight or more, more preferably 5% by weight or more, based on 100% by weight of the solid content of the cellulose raw material. The upper limit is usually 30% by weight or less. Therefore, the amount of ozone added is preferably 0.1% by weight or more and 30% by weight or less, more preferably 5% by weight or more and 30% by weight or less, based on 100% by weight of the solid content of the cellulose raw material. The ozone treatment temperature is usually 0°C or higher, preferably 20°C or higher. The upper limit is usually 50°C or less. Therefore, the ozone treatment temperature is usually 0°C or higher and 50°C or lower, preferably 20°C or higher and 50°C or lower. The ozone treatment time is usually 1 minute or more, preferably 30 minutes or more. The upper limit is usually 360 minutes or less. Therefore, the ozone treatment time is usually 1 minute or more and 360 minutes or less, preferably 30 minutes or more and 360 minutes or less. When the ozone treatment conditions are within the above range, excessive oxidation and decomposition of cellulose can be prevented, and the yield of oxidized cellulose can be improved.

The resulting product obtained after the ozone treatment may be further subjected to additional oxidation treatment using an oxidizing agent. The oxidizing agent used in the additional oxidation treatment is not particularly limited, but includes, for example, chlorine-based compounds such as chlorine dioxide and sodium chlorite; oxygen, hydrogen peroxide, persulfuric acid, and peracetic acid. Examples of methods for the additional oxidation treatment include a method in which an oxidizing agent solution is prepared by dissolving these oxidizing agents in a polar organic solvent such as water or alcohol, and the cellulose raw material is immersed in the oxidizing agent solution.

The amount of carboxyl groups, carboxylate groups, and aldehyde groups contained in the oxidized cellulose nanofibers can be adjusted by controlling oxidation conditions such as the amount of oxidizing agent added and reaction time.
An example of a method for measuring the amount of carboxyl groups will be explained below. Prepare 60 ml of 0.5% by weight slurry (aqueous dispersion) of oxidized cellulose, add 0.1M hydrochloric acid aqueous solution to adjust the pH to 2.5, and then dropwise add 0.05N sodium hydroxide aqueous solution to bring the pH to 11. Measure the electrical conductivity until the The amount of carboxyl groups can be calculated from the amount of sodium hydroxide (a [ml]) consumed in the neutralization stage of the weak acid where the electrical conductivity changes slowly using the following formula:
Amount of carboxyl group [mmol/g oxidized cellulose or cellulose nanofiber] = a [ml] x 0.05/weight of oxidized cellulose [g]

(2-2-2) Etherification (carboxymethylation) cellulose nanofiber Etherification includes carboxymethyl (ether) conversion, methyl (ether) conversion, ethyl (ether) conversion, cyanoethylation (ether), hydroxyethyl ( (ether), hydroxypropyl (ether), ethylhydroxyethyl (ether), hydroxypropylmethyl (ether), and the like. As an example of these methods, the method of carboxymethylation will be described below.
When modifying a cellulose raw material by carboxymethylation, the degree of carboxymethyl group substitution per anhydroglucose unit in the obtained carboxymethylated cellulose or cellulose nanofiber is preferably 0.01 or more, more preferably 0.05 or more, More preferably, it is 0.10 or more. The upper limit is preferably 0.50 or less, more preferably 0.40 or less, and even more preferably 0.35 or less. Therefore, the degree of carboxymethyl group substitution is preferably 0.01 or more and 0.50 or less, more preferably 0.05 or more and 0.40 or less, and even more preferably 0.10 or more and 0.35 or less.

Although the method of carboxymethylation is not particularly limited, for example, a method of mercerizing a cellulose raw material as a bottom forming raw material and then etherifying it can be mentioned. Examples of the solvent used in the carboxymethylation reaction include water, alcohol (eg, lower alcohol), and a mixed solvent thereof. Examples of the lower alcohol include methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, and tertiary butanol. The mixing ratio of lower alcohol in the mixed solvent is usually 60% by weight or more and 95% by weight or less. The amount of solvent is usually 3 times the weight of the cellulose raw material. The upper limit is not particularly limited, but is 20 times the weight. Therefore, the amount of the solvent is preferably 3 times or more and 20 times or less by weight.

Mercerization is usually performed by mixing the bottom forming raw material and a mercerizing agent. Examples of the mercerizing agent include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. The amount of the mercerizing agent to be used is preferably 0.5 times or more, more preferably 1.0 times or more, and even more preferably 1.5 times or more by mole per anhydroglucose residue in the bottom raw material. The upper limit is usually 20 times the mole or less, preferably 10 times the mole or less, and more preferably 5 times the mole or less. Therefore, it is preferably 0.5 times mole or more and 20 times mole or less, more preferably 1.0 times mole or more and 10 times mole or less, and even more preferably 1.5 times mole or more and 5 times mole or less.
The reaction temperature for mercerization is usually 0°C or higher, preferably 10°C or higher. The upper limit is usually 70°C or less, preferably 60°C or less. Therefore, the reaction temperature is usually 0°C or higher and 70°C or lower, preferably 10°C or higher and 60°C or lower. The reaction time is usually 15 minutes or more, preferably 30 minutes or more. The upper limit is usually 8 hours or less, preferably 7 hours or less. Therefore, the time is usually 15 minutes or more and 8 hours or less, preferably 30 minutes or more and 7 hours or less.

The etherification reaction is usually carried out by adding a carboxymethylating agent to the reaction system after mercerization. Examples of carboxymethylating agents include sodium monochloroacetate. The amount of the carboxymethylating agent added is usually preferably 0.05 times or more, more preferably 0.5 times or more, and even more preferably 0.8 times or more by mole per glucose residue in the cellulose raw material. The upper limit is usually 10.0 times the mole or less, preferably 5 times the mole or less, more preferably 3 times the mole or less, therefore, preferably 0.05 times the mole or more and 10.0 times the mole or less, more preferably It is 0.5 times mole or more and 5 times mole or less, and more preferably 0.8 times mole or more and 3 times mole or less. The reaction temperature is usually 30°C or higher, preferably 40°C or higher, and the upper limit is usually 90°C or lower, preferably 80°C or lower. Therefore, the reaction temperature is usually 30°C or more and 90°C or less, preferably 40°C or more and 80°C or less. The reaction time is usually 30 minutes or more, preferably 1 hour or more. The upper limit is usually 10 hours or less, preferably 4 hours or less. Therefore, the reaction time is usually 30 minutes or more and 10 hours or less, preferably 1 hour or more and 4 hours or less. The reaction solution may be stirred as necessary during the carboxymethylation reaction.

The degree of carboxymethyl group substitution per glucose unit of carboxymethylated cellulose nanofibers may be measured, for example, by the following method. That is, 1) Accurately weigh about 2.0 g of carboxymethylated cellulose (absolutely dried) and place it in a 300 mL Erlenmeyer flask with a stopper. 2) Add 100 mL of methanol nitrate obtained by adding 100 mL of special grade concentrated nitric acid to 1000 mL of methanol, and shake for 3 hours to convert carboxymethylcellulose salt (carboxymethylated cellulose) into hydrogen-type carboxymethylated cellulose. 3) Accurately weigh 1.5 to 2.0 g of hydrogen-type carboxymethylated cellulose (absolutely dried) and place it in a 300 mL Erlenmeyer flask with a stopper. 4) Wet hydrogen carboxymethylated cellulose with 15 mL of 80% methanol, add 100 mL of 0.1N NaOH, and shake at room temperature for 3 hours. 5) Back titrate excess NaOH with 0.1N H ₂ SO ₄ using phenolphthalein as indicator. 6) The degree of carboxymethyl group substitution (DS) is calculated by the following formula:
A=[(100×F'-(0.1N H ₂ SO ₄ )(mL)×F)×0.1]
/(absolute dry mass (g) of hydrogen-type carboxymethylated cellulose)
DS=0.162×A/(1-0.058×A)
A: 1N required to neutralize 1g of hydrogen-type carboxymethylated cellulose
Amount of NaOH (mL)
F': Factor of 0.1N H ₂ SO ₄ F: Factor of 0.1N NaOH

(2-2-3) Cationized cellulose nanofibers When cellulose raw materials are modified by cationization, the resulting cationized cellulose nanofibers contain cations such as ammonium, phosphonium, sulfonium, or groups containing such cations in the molecule. It is sufficient if it is included. The cationized cellulose nanofiber preferably contains a group containing ammonium, and more preferably contains a group containing quaternary ammonium.

The method of cationization is not particularly limited, but for example, a method of reacting a cationization agent and a catalyst with a cellulose raw material in the presence of water and/or alcohol can be mentioned. Examples of the cationizing agent include glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrialkylammonium hydrate (e.g. 3-chloro-2-hydroxypropyltrimethylammonium hydrate), and halohydrin types thereof. By using any of these, cationized cellulose having a group containing quaternary ammonium can be obtained. Examples of the catalyst include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. Examples of the alcohol include alcohols having 1 to 4 carbon atoms. The amount of the cationizing agent is preferably 5% by weight or more, more preferably 10% by weight or more based on 100% by weight of the cellulose raw material. The upper limit is usually 800% by weight or less, preferably 500% by weight or less. The amount of catalyst is preferably 0.5% by weight or more, more preferably 1% by weight or more based on 100% by weight of cellulose fibers. The upper limit is usually 7% by weight or less, preferably 3% by weight or less. The amount of alcohol is preferably 50% by weight or more, more preferably 100% by weight or more based on 100% by weight of cellulose fibers. The upper limit is usually 50,000% by weight or less, preferably 500% by weight or less.

The reaction temperature during cationization is usually 10°C or higher, preferably 30°C or higher, and the upper limit is usually 90°C or lower, preferably 80°C or lower. The reaction time is usually 10 minutes or more, preferably 30 minutes or more. The upper limit is usually 10 hours or less, preferably 5 hours or less. The reaction solution may be stirred as necessary during the cationization reaction.
The degree of cation substitution per glucose unit of cationized cellulose can be adjusted by controlling the amount of cationizing agent added and the composition ratio of water and/or alcohol. The degree of cationic substitution refers to the number of substituents introduced per unit structure (glucopyranose ring) constituting cellulose. In other words, the degree of cationic substitution is defined as "the value obtained by dividing the number of moles of the introduced substituent by the total number of moles of hydroxyl groups in the glucopyranose ring." Since pure cellulose has three substitutable hydroxyl groups per unit structure (glucopyranose ring), the theoretical maximum value of the degree of cation substitution is 3 (minimum value is 0).

The degree of cation substitution per glucose unit of the cationized cellulose nanofiber is preferably 0.01 or more, more preferably 0.02 or more, and even more preferably 0.03 or more. The upper limit is preferably 0.40 or less, more preferably 0.30 or less, and even more preferably 0.20 or less. Therefore, it is preferably 0.01 or more and 0.40 or less, more preferably 0.02 or more and 0.30 or less, and even more preferably 0.03 or more and 0.20 or less. By introducing cationic substituents into cellulose, the cells electrically repel each other. Therefore, cellulose into which cationic substituents have been introduced can be easily nano-fibrillated. When the degree of cation substitution per glucose unit is 0.01 or more, sufficient nanofibrillation can be achieved. On the other hand, by having a degree of cation substitution per glucose unit of 0.40 or less, swelling or dissolution can be suppressed, thereby maintaining the fiber morphology and preventing a situation where the nanofiber cannot be obtained. be able to.

An example of a method for measuring the degree of cation substitution per glucose unit will be described below. After drying the sample (cationized cellulose), the nitrogen content is measured using a total nitrogen analyzer TN-10 (manufactured by Mitsubishi Chemical Corporation), and the degree of cation substitution is calculated using the following formula. The degree of cationic substitution here is the average number of moles of substituents per mole of anhydroglucose unit.
Degree of cation substitution = (162×N)/(1-151.6×N)
N: Nitrogen content

(2-2-4) Esterified cellulose nanofiber The method of esterification is not particularly limited, but includes, for example, a method of reacting the following compound A with a cellulose raw material. Examples of methods for reacting compound A with cellulose raw material include a method of mixing powder or aqueous solution of compound A with cellulose raw material, a method of adding an aqueous solution of compound A to a slurry of cellulose raw material, and the like. Among these methods, the method of mixing an aqueous solution of Compound A with the cellulose raw material or its slurry is preferred because it increases the uniformity of the reaction and the esterification efficiency.

Examples of the compound A include phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid, and esters thereof. Compound A may be in the form of a salt. Among the above, phosphoric acid compounds are preferred because they are low in cost, easy to handle, and can introduce phosphoric acid groups into the cellulose of pulp fibers to improve defibration efficiency. The phosphoric acid compound may be any compound having a phosphoric acid group, such as phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, dihydrogen phosphate, etc. Potassium hydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium metaphosphate, etc. . The phosphoric acid compounds used may be one type or a combination of two or more types. Among these, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, phosphoric acid The ammonium salt of is preferred, and sodium dihydrogen phosphate and disodium hydrogen phosphate are more preferred. Furthermore, it is preferable to use an aqueous solution of a phosphoric acid compound in the esterification because it increases the uniformity of the reaction and increases the efficiency of introducing a phosphoric acid group. The pH of the aqueous solution of the phosphoric acid compound is preferably 7 or less, since this increases the efficiency of introducing phosphoric acid groups, and more preferably 3 or more, from the viewpoint of suppressing hydrolysis of pulp fibers.

Examples of the esterification method include the following methods. Compound A is added to a suspension of cellulose raw material (for example, solid content concentration 0.1 to 10% by weight) with stirring to introduce phosphoric acid groups into cellulose. When the cellulose raw material is 100 parts by weight, when Compound A is a phosphoric acid compound, the amount of Compound A added is preferably 0.2 parts by weight or more, more preferably 1 part by weight or more as the amount of phosphorus element. Thereby, the yield of fine fibrous cellulose can be further improved. The upper limit is preferably 500 parts by weight or less, more preferably 400 parts by weight or less. Thereby, a yield commensurate with the amount of compound A used can be efficiently obtained. Therefore, it is preferably 0.2 parts by weight or more and 500 parts by weight or less, more preferably 1 part by weight or more and 400 parts by weight or less.

When reacting Compound A with the cellulose raw material, the following Compound B may be further added to the reaction system. Examples of the method for adding compound B to the reaction system include adding it to a slurry of cellulose raw materials, an aqueous solution of compound A, or a slurry of cellulose raw materials and compound A.

Compound B is a nitrogen-containing compound that exhibits basicity. "Exhibiting basicity" usually means that an aqueous solution of Compound B exhibits a pink to red color in the presence of a phenolphthalein indicator, or that the pH of an aqueous solution of Compound B is greater than 7. The basic nitrogen-containing compound is not particularly limited as long as it achieves the effects of the present invention, but compounds having an amino group are preferred. Examples include urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine, and the like. Among these, urea is preferred because it is low cost and easy to handle. The amount of compound B added is preferably 2 parts by weight or more and 1000 parts by weight or less, more preferably 100 parts by weight or more and 700 parts by weight or less, based on 100 parts by weight of the cellulose raw material. The reaction temperature is preferably 0°C or higher and 95°C or lower, more preferably 30°C or higher and 90°C or lower. The reaction time is not particularly limited, but is usually about 1 minute or more and 600 minutes or less, preferably 30 minutes or more and 480 minutes or less. When the esterification reaction conditions are within any of these ranges, it is possible to prevent cellulose from being excessively esterified and become easily dissolved, and it is possible to improve the yield of phosphoesterified cellulose. .

After reacting the cellulose raw material with compound A, an esterified cellulose suspension is usually obtained. The esterified cellulose suspension is dehydrated if necessary, and it is preferable to perform a heat treatment after dehydration. Thereby, hydrolysis of the cellulose raw material can be suppressed. The heating temperature is preferably 100°C or higher and 170°C or lower, and is heated at 130°C or lower (more preferably 110°C or lower) while water is present during the heat treatment, and heated at 100°C or higher and 170°C or lower after removing water. It is more preferable to perform the heat treatment at a temperature below .degree.

In phosphoric acid esterified cellulose, a phosphoric acid group substituent is introduced into the cellulose raw material, and the cellulose cells electrically repel each other. Therefore, phosphoric acid esterified cellulose can be easily nano-fibrillated. The degree of phosphoric acid group substitution per glucose unit of the phosphoric acid esterified cellulose is preferably 0.001 or more. Thereby, sufficient defibration (for example, nano-defibration) can be performed. The upper limit is preferably 0.40. Thereby, swelling or dissolution of the phosphoric acid esterified cellulose can be prevented, and a situation in which nanofibers cannot be obtained can be prevented. Therefore, it is preferably 0.001 or more and 0.40 or less. The phosphoric acid esterified cellulose is preferably subjected to a washing treatment such as washing with cold water after boiling. This allows efficient defibration.

(2-3) Defibration Defibration of the cellulose raw material may be performed before or after the modification treatment of the cellulose raw material. Further, defibration may be performed at once or multiple times. In the case of multiple defibrations, each defibration can be performed at any time.
The device used for defibration is not particularly limited, but examples include high-speed rotation type, colloid mill type, high pressure type, roll mill type, and ultrasonic type devices. High pressure or ultra-high pressure homogenizers are preferred, and wet high pressure homogenizers are preferred. Or an ultra-high pressure homogenizer is more preferable. The device is preferably one that can apply strong shearing force to the cellulose raw material or modified cellulose (usually a dispersion). The pressure that can be applied by the device is preferably 50 MPa or more, more preferably 100 MPa or more, and still more preferably 140 MPa or more. The device is preferably a wet high-pressure or ultra-high-pressure homogenizer that can apply the above pressure to the cellulose raw material or modified cellulose (usually a dispersion) and can also apply a strong shearing force. Thereby, defibration can be performed efficiently.

When defibrating a dispersion of cellulose raw materials, the solid content concentration of the cellulose raw materials in the dispersion is usually 0.1% by weight or more, preferably 0.2% by weight or more, and more preferably 0.3% by weight. % by weight or more. As a result, the amount of liquid is appropriate for the amount of cellulose fiber raw material, which is efficient. The upper limit is usually 10% by weight or less, preferably 6% by weight or less. This allows fluidity to be maintained.
Prior to defibration (preferably defibration using a high-pressure homogenizer) or dispersion treatment performed before defibration as necessary, a preliminary treatment may be performed as necessary. The pretreatment may be performed using a mixing, stirring, emulsifying, dispersing device such as a high-speed shear mixer.

(2-4) Cellulose nanofibers In the present invention, at least one of the above-mentioned carboxylated cellulose nanofibers, carboxymethylated cellulose nanofibers, cationized cellulose nanofibers, and esterified cellulose nanofibers can be used as the CNF. .
Although CNF may be used as a dispersion, it may be used as a wet solid or a dry solid after the solvent is partially or completely removed by drying if necessary. A wet solid is a solid that is intermediate in form between a dispersion and a dry solid.
When performing the drying process, in order to improve redispersibility, a water-soluble polymer may be mixed in advance into the CNF dispersion before the drying process is performed. Examples of water-soluble polymers include cellulose derivatives (carboxymethylcellulose and its salts, methylcellulose, hydroxypropylcellulose, ethylcellulose), xanthan gum, xyloglucan, dextrin, dextran, carrageenan, locust bean gum, alginic acid, alginate, pullulan, starch, Katakuri flour, kudzu flour, positive starch, phosphorylated starch, corn starch, gum arabic, gellan gum, polydextrose, pectin, chitin, water-soluble chitin, chitosan, casein, albumin, soybean protein solution, peptone, polyvinyl alcohol, polyacrylamide, polyester Sodium acrylate, polyvinylpyrrolidone, polyvinyl acetate, polyamino acid, polylactic acid, polymalic acid, polyglycerin, latex, rosin-based sizing agent, petroleum resin-based sizing agent, urea resin, melamine resin, epoxy resin, polyamide resin, polyamide resin Included are polyamine resins, polyethyleneimines, polyamines, vegetable gums, polyethylene oxides, hydrophilic crosslinked polymers, polyacrylates, starch polyacrylic acid copolymers, tamarind gum, guar gum and colloidal silica, and mixtures of one or more thereof. Among these, it is preferable to use carboxymethyl cellulose and its salts from the viewpoint of compatibility.

Dry solids and wet solids of CNF may be prepared by drying a dispersion of CNF or a mixture of CNF and a water-soluble polymer. The drying method is not particularly limited, and examples include spray drying, compression, air drying, hot air drying, and vacuum drying. Examples of drying equipment include continuous tunnel drying equipment, band drying equipment, vertical drying equipment, vertical turbo drying equipment, multistage disk drying equipment, ventilation drying equipment, rotary drying equipment, flash drying equipment, and spray dryer drying equipment. , spray drying equipment, cylindrical drying equipment, drum drying equipment, screw conveyor drying equipment, rotary drying equipment with heating tubes, vibration transport drying equipment, etc., batch-type box drying equipment, vacuum box drying equipment, agitation drying equipment, etc. can be mentioned. These drying devices may be used alone or in combination of two or more. The drying device is preferably a drum drying device. Thereby, thermal energy can be uniformly and directly supplied to the material to be dried, thereby improving energy efficiency. Further, the dried material can be immediately collected without applying more heat than necessary.

Since the CNF used in the present invention has excellent fluidity and gas barrier properties, it is possible to improve air shielding properties by coating it on a base paper.
The preferred coating amount of CNF is 0.1 g/m ² or more and 2.0 g/m 2 or less, preferably 0.2 g/m ² or more and 1.5 g/m ^{2 or} less as solid content coating amount per one side. It is. If the coating amount of CNF is less than 0.1 g/m ² , the improvement in air permeability resistance is small and air shielding properties may be insufficient. If the coating amount exceeds 2.0 g/m ² , moisture permeability may decrease.

(3) Hygroscopic agents Hygroscopic agents include alkali metal salts such as lithium chloride and sodium lactate, alkaline earth metal salts such as calcium chloride and magnesium chloride, ammonium salts such as ammonium phosphate and ammonium sulfamate, guanidine sulfamate, etc. Guanidine salts such as guanidine hydrochloride can be used, and especially calcium chloride, which has excellent hygroscopicity and is inexpensive, can be used suitably. These compounds may be used alone or in combination of two or more. Furthermore, moisture absorbents that can be used as flame retardants can also be blended in order to impart flame retardancy to the base paper.

The preferred coating amount of the moisture absorbent is 0.5 g/m ² or more and 15 g/m ² or less, preferably 1 g/m ² or more and 10 g/m ² or less. If the coating amount of the moisture absorbent is less than 0.5 g/m ² , moisture permeability may be insufficient. Furthermore, if the coating amount exceeds 15 g/m ² , the amount of moisture absorbed will be excessive, and dew condensation or run-off of the moisture absorbent may occur in a high temperature and high humidity environment. The moisture absorbent may be impregnated into the entire base paper, or may be coated on one or both sides.

(4) Water-soluble polymer In the present invention, the water-soluble polymer refers to a polymer compound that dissolves 0.1 g or more in 100 g of water at 20° C. and has a film-forming effect. Examples include water-soluble polysaccharides such as carboxyalkylcellulose salts, hydroxyethylcellulose, methylcellulose, polyethylene oxide, and guar gum. Among these, carboxyalkylcellulose salts are preferred because they have excellent compatibility with CNF. Further, examples of the carboxyalkylcellulose salt include alkali metal salts such as carboxymethylcellulose and carboxyethylcellulose, calcium salts, magnesium salts, ammonium salts, etc., and alkali metal salts of carboxymethylcellulose are preferred because they have excellent film-forming properties.

When a carboxymethyl cellulose salt (hereinafter also referred to as CMC) is formed alone, it forms a uniform film with excellent air shielding properties. Furthermore, even when mixed with moisture absorbing agents such as calcium chloride and lithium chloride, an aqueous solution of CMC does not easily aggregate or form liquid-absorbing gels, does not reduce coating suitability, and forms a film with high air-shielding properties. . However, CMC films tend to reduce moisture permeability, and there is a concern that the coated paper winding will block if coated in large quantities on the base paper. It was hardly used. When CMC is used as the water-soluble polymer, CMC is blended within a range that does not impair the moisture permeability of the cellulose nanofiber layer (CNF layer), taking advantage of the air shielding effect of CMC.

CMC is preferably a sodium salt, a potassium salt, or a lithium salt, and the sodium salt is preferably used from the viewpoint of versatility. The carboxymethyl group substitution degree of CMC is preferably 0.55 or more and 1.6 or less, more preferably 0.6 or more and 1.2 or less. If the carboxymethyl group substitution degree is less than 0.55, the viscosity tends to be reduced by a moisture absorbent, and coating suitability and air shielding properties tend to decrease, while if it exceeds 1.6, the cost increases and is not preferred.

The viscosity of CMC is a type B viscosity of a 1% aqueous solution, and is preferably 1,000 mPa·s or more and 20,000 mPa·s or less. If the viscosity of type B is less than 1,000 mPa·s, the viscosity becomes low when a moisture absorbent is mixed, resulting in a decrease in coating suitability. Further, if the B type viscosity exceeds 20,000 mPa·s, the entire coating liquid becomes highly viscous, making coating difficult.

CMC, like CNF, has a sealing effect. By applying a chemical solution containing a mixture of both CMC and CNF with a moisture absorbent, air shielding properties and moisture permeability are improved compared to applying a chemical solution containing CMC or CNF alone as a moisture absorbent. An improved heat exchange element paper can be obtained. In particular, according to the research conducted by the present inventors, by mixing CMC and CNF and using a moisture absorbent in combination, moisture permeability in a low humidity environment can be significantly improved without reducing air shielding properties. This is new knowledge that has not been previously known.
The preferred coating amount of CMC is 0.05 g/m ² or more and 1.0 g/m ² or less, preferably 0.1 g/m ² or more and 0.8 g/m ² or less as solid content coating amount per one side. It is. If the coating amount of CMC is less than 0.05 g/m ² , the improvement in air permeability resistance is small and air shielding properties may be insufficient. If the coating amount exceeds 1.0 g/m ² , moisture permeability may decrease.

(5) Total heat exchange element paper The total heat exchange element paper of the present invention is produced by applying a chemical solution containing at least CNF, a moisture absorbent, and a water-soluble polymer to a base paper containing papermaking fibers. be able to. These can be applied to the base paper with the same or different chemical solutions, but it is preferable to apply the same chemical solution because the amount of each component to be coated can be estimated accurately. At this time, in order to prevent undissolved portions and gelation, it is preferable to make an aqueous solution in advance and mix it together.

The chemical solution preferably contains a total of 3 parts by mass or more and 40 parts by mass or less of CNF and a water-soluble polymer per 100 parts by mass of the moisture absorbent (hereinafter, means solid content parts by mass unless otherwise specified), and 5 parts by mass or less of CNF and water-soluble polymer. It is more preferable to contain 35 parts by mass or more and 35 parts by mass or less. If the total amount of CNF and water-soluble polymer is less than 3 parts by mass, the resulting total heat exchange element paper may lack air shielding properties, and if it exceeds 40 parts by mass, the viscosity of the chemical solution increases and ease of handling decreases. There are cases where
Further, the ratio of CNF to water-soluble polymer in the chemical solution is preferably 40:60 to 80:20 in terms of solid content, and more preferably 50:50 to 75:25. If the blending ratio of CNF is smaller than the above range, the moisture permeability of the obtained total heat exchange element paper may be insufficient, and if the blending ratio of CNF is larger than the above range, the air shielding of the obtained total heat exchange element paper may be insufficient. There may be a lack of sex.

Various commonly used functional auxiliaries such as waterproofing agents, flame retardants, rust preventives, antibacterial agents, antibacterial agents, and antiblocking agents may be added to the chemical solution of the present invention, if necessary. . Furthermore, when applying a chemical to the base paper, it is applied to at least one side, but when applying to both sides, the same chemical may be used on both sides, or a chemical with a different formulation or composition may be used for each side.

The method for coating the base paper with the chemical solution prepared as described above includes coating machines such as a rod coater, die coater, curtain coater, two-roll size press, rod metering size press, gate roll coater, and blade coater. Examples include a coating method and an impregnating method.

The method for drying the wet coating layer is not particularly limited, and various methods such as a steam heating cylinder, a hot air air dryer, a gas heater dryer, an electric heater dryer, an infrared heater dryer, etc. can be used alone or in combination. .

The obtained coated paper may be subjected to calender treatment using a super calender, a hot pressure roll, etc., if necessary. By calendering, the thickness is reduced and the thermal conductivity in the thickness direction is improved, and by increasing the density, the air permeability is increased and the air shielding property is improved.

In this way, a paper containing papermaking fibers, CNF, a moisture absorbent, and a water-soluble polymer is obtained, and this paper has both air-shielding properties and moisture permeability, and can be suitably used as a total heat exchange element paper.

The basis weight of the total heat exchange element paper is preferably 10 g/m ² or more and 40 g/m ² or less, more preferably 15 g/m ² or more and 35 g/m ² or less, and most preferably 20 g/m ² or more and 30 g/m ^{2 or less.} It is as follows. If the basis weight is less than 10 g/m ² , the strength will be significantly reduced and the workability during processing into a total heat exchange element will be reduced. If the basis weight exceeds 40 g/m ² , the total heat exchange efficiency in the thickness direction decreases, which is not preferable.

The thickness of the total heat exchange element paper is preferably 15 μm or more and 50 μm or less, and within this range, the thinner the paper, the more preferable it is because the total heat exchange efficiency tends to be higher. If the thickness is less than 15 μm, the strength will be significantly reduced and the workability during processing into a total heat exchange element will be reduced. Moreover, if the thickness exceeds 50 μm, the total heat exchange efficiency in the thickness direction decreases, which is not preferable.

The air permeability resistance of the total heat exchange element paper of the present invention is 10,000 seconds or more. Since the total heat exchange element paper of the present invention has a high air permeation resistance of 10,000 seconds or more, it is difficult for air to mix between fresh supply air and dirty exhaust air, and the carbon dioxide transfer rate is particularly low. , has excellent air shielding properties that separate air supply and exhaust air. The air permeation resistance is more preferably 20,000 seconds or more, even more preferably 30,000 seconds or more, and most preferably 50,000 seconds or more.

The total heat exchange element paper of the present invention has a moisture permeability measured using a measuring instrument according to JIS Z0208, using magnesium chloride hexahydrate as the moisture absorbing agent, and under high humidity environmental conditions of 25°C and 75% relative humidity. (hereinafter referred to as high moisture permeability) is preferably 1300 g/m ^2.24 h or more, more preferably 1400 g/m ^2.24 h or more, and even more preferably 1500 g/m ^2.24 h or more. . In addition, the water vapor permeability (hereinafter referred to as low moisture vapor permeability) measured using a measuring instrument according to JIS Z0208, using lithium chloride as a moisture absorbing agent, and under low humidity environmental conditions of 25°C and 35% relative humidity was 550g/ It is preferably at least m ² ·24 h, more preferably at least 600 g/m ² ·24 h, even more preferably at least 650 g/m ² ·24 h. Total heat exchange element paper with high moisture permeability and low moisture permeability exceeding the above values can be suitably used not only in summer and humid areas, but also in winter, under air-conditioning conditions, and in low humidity areas. , can be used as is in many parts of the world.

The present invention will be explained in more detail with reference to Examples below. The definition and measurement method of each characteristic in the present invention are as follows.

[Measuring method]
(1) Basis weight Put a sample with a size of 210 mm x 160 mm into a weighing bottle with a known weight, measure the weight after drying at 110°C for 10 minutes, calculate the absolute dry weight per square meter of the sample, and amount (g/m ² ).
(2) Thickness The thickness was measured at 5 points using a Takahashi thickness gauge, and the average value was calculated to be the thickness (μm).

(3) Amount of adhesion A 5×5 cm sample was immersed in 60 ml of deionized water and stirred for 5 minutes. Next, 9.6 ml of 10% KOH solution was added, 0.04 g of NN reagent as an indicator was added, and titration was performed with 0.01 M/L EDTA standard solution, and the solution completely changed from reddish-purple to light blue. was the end point. The amount of CaCl ₂ attached was calculated from the following formula.
Furthermore, the amount of CNF adhesion and the amount of CMC adhesion were calculated from the amount of CaCl ₂ adhesion and the solid content composition of the chemical solution.
・_CaCl2 adhesion amount (g/m ² ) = 0.01M EDTA titration amount (ml)
×0.0011099(g)÷25( ^cm2 )
(Here, 1 ml of 0.01 M/L EDTA standard solution = 0.0011099 g of CaCl ₂ (anhydrous))

(4) Moisture Permeability Measurements were carried out using an instrument specified in JIS Z0208 (1976) Moisture Permeability (cup method), changing the temperature and humidity conditions of the measurement environment and the type of moisture absorbent.
When performing measurements at 25°C and 75% RH, put 10g of magnesium chloride hexahydrate and 15g of magnesium chloride hexahydrate saturated solution in a moisture-permeable cup, and after attaching the test piece, place the cup at room temperature of 23°C and humidity of 50%. The cup was left standing in a constant humidity room for 10 minutes, and the weight of the cup was measured. After that, it was left standing in a constant temperature and humidity chamber set at 25°C and 75% RH for 20 minutes and 2 hours (the time when the moisture permeable cup was first placed is 0 minutes), and the weight increase was measured. The weight increase per square meter per 24 hours was calculated and defined as high moisture permeability (g/m ² ·24 hours).
When performing measurements at 25°C and 35% RH, put 10g of lithium chloride and 15g of saturated lithium chloride solution in a moisture-permeable cup, attach the test piece, and leave it for 10 minutes in a constant humidity room at a room temperature of 23°C and humidity of 50%. The weight of the cup was then measured. After that, the weight increase was measured by leaving it in a constant temperature and humidity chamber set at 25°C and 35% RH for 2 hours, and calculating the weight increase per 24 hours for a measurement area of 1 square meter. / ^m2・24h).

(5) Air permeability resistance The average value of four measurements was calculated based on the Ohken test machine method described in JIS P8117 (2009) Air permeability and air resistance. ken) (second). Note that the measurement range of the air permeability resistance using the Oken type air permeability tester (model KG1 manufactured by Asahi Seiko Co., Ltd.) used is 250 to 100,000 seconds.

<Example 1>
25.8 parts by mass (in form) of a carboxymethylated CNF aqueous dispersion (solid concentration 3.72 mass%) was added to an aqueous solution of powdered CMC-Na salt (Sunrose F350HC manufactured by Nippon Paper Industries Co., Ltd.) (solid concentration 3. After adding 13.0 parts by mass (in form) of calcium chloride (manufactured by Tokuyama Corporation, absolutely dry) (solid content concentration 6.4 parts by mass), 39.7 parts by mass (in form) of calcium chloride (solid content 6.4 parts by mass) ) was added and dispersed and dissolved using a homomixer to prepare a drug solution. The total solid content of CNF and CMC is 21.1 parts by mass with respect to 100 parts by mass of the solid content of the moisture absorbent in this chemical solution, and the solid content ratio of CNF and CMC is 70:30.
A chemical solution was applied to one side of a base paper (air permeability resistance 1000 seconds) having an absolute dry basis weight of 14.5 g/m ² and a thickness of 1000 seconds using a Mayer bar and dried to obtain a total heat exchange element paper.

<Examples 2 to 4>
A total heat exchange element paper was obtained in the same manner as in Example 1, except that the chemical solution having the composition shown in Table 1 was used.
<Comparative Examples 1 to 3>
A total heat exchange element paper was obtained in the same manner as in Example 1, except that the chemical solution having the composition shown in Table 1 was used.

<Examples 5 to 7>
The same procedure as in Example 1 was carried out, except that the chemical solution having the composition shown in Table 1 was applied to a base paper with an absolute dry basis weight of 18.0 g/m ² and a thickness of 35 μm (air permeability resistance of 1800 seconds). A heat exchange element paper was obtained.
<Comparative example 4>
A total heat exchange element paper was obtained in the same manner as in Example 5, except that the chemical solution having the composition shown in Table 1 was used.

<Examples 8 to 10>
A total heat exchange element paper was obtained in the same manner as in Example 1, except that the chemical solution having the composition shown in Table 1 was used.
<Example 11>
A total heat exchange element paper was obtained in the same manner as in Example 1, except that carboxylated CNF was used as the cellulose nanofiber and a chemical solution having the composition shown in Table 1 was used.
<Comparative example 5>
A total heat exchange element paper was obtained in the same manner as in Example 11, except that the chemical solution having the composition shown in Table 1 was used.

The total heat exchange element paper manufactured in the example of the present invention had an air permeability resistance of 10,000 seconds or more and was excellent in air shielding properties. It was also confirmed that it has excellent high moisture permeability and low moisture permeability, and can be used in a wide range of environments.

Claims (6)

Contains paper-making fibers, cellulose nanofibers, moisture absorbers, and water-soluble polymers, and has an air permeability resistance of 10,000 seconds or more,
The moisture permeability measured using a measuring instrument according to JIS Z0208 and using magnesium chloride hexahydrate as the moisture absorbent under high humidity environmental conditions of 25°C and 75% relative humidity is 1300 g/m 2.24 h or ^more . A total heat exchange element paper using lithium chloride as a moisture absorbent and having a moisture permeability of 550 g/m ² ·24 h or more when measured under low humidity environmental conditions of 25° C. and 35% relative humidity. The papermaking fiber is a cellulose fiber,
The total heat exchange element paper according to claim 1, wherein the water-soluble polymer is a carboxyalkyl cellulose salt. The total heat according to claim 1 or 2, wherein the cellulose nanofiber is at least one of carboxymethylated cellulose nanofiber, carboxylated cellulose nanofiber, cationized cellulose nanofiber, and esterified cellulose nanofiber. Replacement element paper. The total heat exchange element paper according to any one of claims 1 to 3, wherein the moisture absorbent is calcium chloride. The total heat exchange element paper according to any one of claims 1 to 4, having a basis weight of 10 g/m ² or more and 40 g/m ² or less. A method for producing total heat exchange element paper, comprising applying a chemical solution containing a moisture absorbent, cellulose nanofibers, and a water-soluble polymer to at least one side of a base paper containing papermaking fibers, the method comprising:
The obtained total heat exchange element paper has an air permeability resistance of 10,000 seconds or more,
The moisture permeability measured using a measuring instrument according to JIS Z0208 and using magnesium chloride hexahydrate as the moisture absorbent under high humidity environmental conditions of 25°C and 75% relative humidity is 1300 g/m 2.24 h or ^more . A method for producing a total heat exchange element paper, characterized in that lithium chloride is used as a moisture absorbent and the moisture permeability measured under low humidity environmental conditions of 25° C. and 35% relative humidity is 550 g/m ² · 24 h or more. .