JP6927969B2 - Total heat exchange element paper - Google Patents

Description

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

In recent years, with the widespread use of air conditioners such as cooling and heating, ventilation heat exchangers capable of recovering temperature and humidity by exchanging heat between supply air and exhaust air during ventilation have been used.
This heat exchanger consists of a flat plate-shaped partition plate having heat transfer property and moisture permeability and an interval plate sandwiched between two partition plates to secure an air flow path, and the partition plate and the interval plate are laminated in a plurality of layers. It has a basic structure. The spacing plate is a corrugated plate formed into a sawtooth or sinusoidal corrugation, and is sandwiched between the partition plates by alternately changing the forming direction of the corrugation in the orthogonal direction. As a result, the fluid passages of the two systems are configured to be orthogonal to each other alternately between the layers composed of the spacing plate and the partition plate.

The partition plate separates the air supply path that introduces fresh outdoor air into the room and the exhaust path that discharges dirty indoor air to the outside, and exchanges latent heat at the same time as sensible heat between the supply air and exhaust. It has a function to perform. For this reason, the partition plate is indispensable for heat transfer and water vapor permeability indicated by humidity permeability, and in addition, flame retardancy and air shielding property so that air supply and exhaust do not mix are required.

Total heat exchange element paper is used as a material for a partition plate that can meet such demands, and the following conventional techniques are disclosed.
Patent Document 1 discloses a total heat exchanger element paper having hygroscopicity and air shielding properties obtained by impregnating or applying a mixed solution of a hygroscopic agent and a water-soluble polymer substance to a porous substrate. There is.
Patent Document 2 describes a total heat exchange element paper having excellent air shielding and hygroscopic properties without using a water-soluble polymer substance by applying a hygroscopic agent to a base paper made from a raw material having a high beating degree. Is disclosed to be obtained.
Patent Document 3 describes a partition member for a heat exchanger having a thickness of 10 to 50 microns and excellent air shielding property, in which an alkali metal salt is mixed with a hygroscopic agent.
Patent Document 4 discloses a total heat exchanger paper having moisture absorption / desorption properties, which is obtained by blending microfibrillated cellulose with moisture absorbing / releasing powders such as silica gel and aluminum hydroxide in papermaking fibers.
Patent Document 5 discloses a total heat exchanger paper using a paper base material containing calcium chloride as a hygroscopic agent and a blocking inhibitor.

Special Publication No. 58-46325 International Publication No. 2002/099193 Japanese Unexamined Patent Publication No. 2003-148892 Japanese Unexamined Patent Publication No. 11-189999 Japanese Unexamined Patent Publication No. 2007-119969

Conventionally, as the total heat exchange element paper, a paper obtained by impregnating or applying a mixed solution of a hygroscopic agent and a water-soluble polymer substance to a porous base material as described in Patent Document 1 has been used for a partition member. Under high temperature and humidity conditions such as summer, a phenomenon occurs in which a part of the water-soluble polymer substance melts and blocks due to moisture absorption, and when corrugating in the element manufacturing process, when rewinding the base paper winding work There is a problem that work efficiency is lowered due to breakage or sticking of the corrugator to the press roll.

Further, in the paper in which a hygroscopic agent is added to a base paper having improved air shielding property by using a raw material having a high beating degree as described in Patent Document 2 and Patent Document 3, the base paper is dense and air permeates. Since it is difficult, it is not necessary to impregnate or coat a water-soluble polymer substance to impart air shielding properties, and by impregnating or coating a chemical solution consisting of a hygroscopic agent or a flame retardant, it has hygroscopic and air shielding properties. Total heat exchange element paper can be obtained. However, if the base paper has a high beating degree, the water squeezing during papermaking will deteriorate and the production efficiency will decrease, and the obtained base paper will be fragile and easily torn, resulting in a decrease in workability when producing a heat exchange unit. There is a problem.

As described in Patent Document 4, a total heat exchange element paper containing silica gel or aluminum hydroxide, which are water-insoluble moisture-absorbing and desorbing powders, and adding microfibrillated cellulose as a sealing material, has moisture-absorbing and desorbing properties. However, even if the basis weight is increased to 120 g / m ^{2, the} air permeation resistance is as low as 200 seconds, and a high degree of air shielding property cannot be obtained.

As described in Patent Document 5, the raw material in which the pulp constituting the base material is beaten to 200 to 600 ml with irregular freeness (according to JIS P8121 except that the pulp sampling amount is 0.3 g) is normal freeness. Since the beating is so high that it is difficult to measure with the measuring method, the water squeezing during papermaking deteriorates and the production efficiency decreases, and the obtained base paper becomes fragile and easily torn, so that it is easy to process when producing a heat exchange unit. May decrease.

As described above, the total heat exchange element paper obtained by impregnating or coating the base paper with a hygroscopic agent and a water-soluble polymer substance is easy to block, while the high-beating base paper is impregnated or coated with a hygroscopic agent. The total heat exchange element paper to which moisture absorption and desorption and air shielding properties are imparted by the work has a problem that the production efficiency at the time of papermaking and the workability at the time of heat exchange unit production may decrease.

An object of the present invention is to provide a total heat exchange element paper having high production efficiency during papermaking, less likely to cause problems such as paper breakage during element processing, and high moisture absorption / desorption and air shielding properties.

As a result of diligent research, the present inventors have developed a new total heat exchange element paper that solves the above problems.
The means for solving the problem of the present invention is as follows.
1. 1. Total heat exchange element paper characterized by containing fibers for papermaking, a hygroscopic agent, and cellulose nanofibers.
2. 1. The papermaking fiber is a cellulose fiber. The total heat exchange element paper described in.
3. 3. 1. The cellulose nanofiber is at least one of a carboxymethylated cellulose nanofiber, a carboxylated cellulose nanofiber, a cationized cellulose nanofiber, and an esterified cellulose nanofiber. Or 2. The total heat exchange element paper described in.
4. 1. The hygroscopic agent is either an alkali metal salt or an alkaline earth metal salt. ~ 3. The total heat exchange element paper according to any one of.
5. 1. The air permeability resistance is 700 seconds or more. ~ 4. The total heat exchange element paper according to any one of.
6. A method for producing total heat exchange element paper, which comprises applying a chemical solution containing a hygroscopic agent and cellulose nanofibers to at least one side of a base paper made of papermaking fibers.

The total heat exchange element paper of the present invention has excellent air permeation resistance and moisture permeation by blending cellulose nanofibers, and can be suitably used for a heat exchanger. Since it is not necessary to use a high-beating base paper for the total heat exchange element paper of the present invention, it is possible to prevent a decrease in production efficiency during papermaking and a weakening of the base paper due to the high-beating base paper. can. Further, the total heat exchange element paper of the present invention can reduce the amount of the water-soluble polymer substance applied, and in some cases, the water-soluble polymer substance is unnecessary, so that blocking is unlikely to occur, and the handling and processing Excellent in sex.

Hereinafter, embodiments of the present invention will be described in detail.
(1) Paper-making fibers The paper-making fibers used as raw materials for the total heat exchange element paper of the present invention are obtained from wood pulps such as coniferous pulp and broadleaf pulp, and non-wood raw materials such as flax, abaca, kenaf, bamboo and bagas. Examples thereof include cellulose fibers obtained from non-wood pulp and the like. The method of cooking the cellulose fibers, the presence or absence of bleaching, and the bleaching method are not particularly limited. In addition to cellulose fibers, synthetic fibers such as polyester fibers, nylon fibers, rayon fibers, and lyocell fibers and semi-synthetic fibers can be blended for the purpose of improving adhesiveness, dimensional stability, and shapeability.

The pulp used in the present invention is beaten to a range of 100 ml CSF or more and 500 ml CSF or less, and more preferably 200 ml CSF or more and 300 ml CSF or less at the Canadian standard freeness described in JIS P8121. When the Canadian standard freshness is less than 100 ml CSF, the paper particles become denser and the voids are reduced, and when used as the base paper for the total heat exchange element paper, the coating agent does not easily penetrate into the paper and the base paper. It is not preferable because problems such as easy blocking due to localization of a hygroscopic agent or the like on the surface and an increase in the amount of expansion and contraction due to a change in humidity occur. Further, if the Canadian standard free water content exceeds 500 ml CSF, the amount of voids and the diameter of the voids of the paper increase, and the air shielding effect of the cellulose nanofibers becomes insufficient, which is not preferable. For beating pulp, a general beating device such as a beater or a refiner can be used, and there are no particular restrictions on the beating device and the beating method.

As the paper material for papermaking, synthetic or semi-synthetic fibers, fillers, colorants, paper strength enhancers, wet paper strength enhancers, aluminum sulfate bands, cationized starch, yield improvers, etc. are added to the beaten pulp as necessary. Is trained.

The above paper charges are made by a general paper making method using a long net type paper machine, a circular net type paper machine, a short net type paper machine, a twin wire type paper machine or a paper machine combining them, and the paper making machine. There are no particular restrictions on the papermaking method. In addition, if necessary, impregnate flame retardant, rust preventive, blocking inhibitor, etc. with an on-machine coating device such as a size press or roll coater, and perform calendar processing with a machine calendar, super calendar, soft nip calendar, etc. Then, the base paper is obtained.

The air permeability resistance of the base paper is improved by the sealing action of the cellulose nanofibers impregnated or coated on the base paper, but in order to fully exert the effect, the air permeability resistance of the base paper itself is set to 50 seconds. It is necessary that the time is 650 seconds or less, preferably 150 seconds or more and 600 seconds or less, and more preferably 200 seconds or more and 500 seconds or less. If the air permeability resistance of the base paper is less than 50 seconds, even if cellulose nanofibers are added by impregnation or coating, the increase in air permeability resistance after the addition is small, and the air shielding property of the total heat exchange element paper is insufficient. .. If the air permeation resistance of the base paper exceeds 650 seconds, it becomes difficult for the impregnated or coated chemical solution to permeate into the inside of the base paper, and blocking by the chemical solution component near the surface of the base paper is likely to occur, which is not preferable. The air permeation resistance of the base paper can be adjusted by ordinary papermaking techniques by changing the degree of beating of the pulp blended as the fiber for papermaking and the basis weight of the base paper.

The total heat exchange element paper of the present invention is obtained by impregnating the base paper with a chemical solution containing cellulose nanofibers and a hygroscopic agent or coating it on at least one side.

(2) Cellulose Nanofibers Cellulose nanofibers are fine fibers obtained by subjecting a cellulose raw material to a chemical modification treatment, if necessary, and then a defibration treatment. The average fiber diameter of cellulose nanofibers is usually about 3 nm or more and 500 nm or less. The average fiber diameter and average fiber length can be obtained by averaging the fiber diameter and fiber length obtained from the results of observing 30 or more fibers using a field emission scanning electron microscope (FE-SEM). ..
The average aspect ratio of cellulose nanofibers 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 by 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 of cellulose nanofibers, is not particularly limited, but for example, plants (for example, wood, bamboo, hemp, jute, kenaf, farmland waste, cloth, pulp (coniferous tree). Unbleached kraft pulp (NUKP), coniferous bleached kraft pulp (NBKP), broadleaf unbleached kraft pulp (LUKP), broadleaf bleached kraft pulp (LBKP), conifer unbleached sulphite pulp (NUSP), conifer bleached sulphite pulp (NBSP) ), Thermomechanical pulp (TMP), recycled pulp, used paper, etc.), animals (for example, squirrels), algae, microorganisms (for example, acetic acid bacteria (acetobacter)), etc. The cellulose raw materials used in the present invention are these. It may be either one or a combination of two or more kinds, but it is preferably a pulp raw material derived from a plant or a microorganism (for example, cellulose fiber), and more preferably a cellulose raw material derived from a plant (for example, cellulose). Fiber).
The number average fiber diameter of the cellulose raw material is not particularly limited, but is about 30 μm or more and 60 μm or less in the case of coniferous kraft pulp, which is a general pulp, and about 10 μm or more and 30 μm or less in the case of hardwood kraft pulp. In the case of other pulp, the one that has undergone general purification is about 50 μm. For example, when a chip or the like having a size of several cm is purified, it is preferable to perform mechanical treatment with a dissociator such as a refiner or a beater to adjust the size to about 50 μm.

(2-2) The modified cellulose raw material has 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 when the chemical modification treatment is performed, the finer fibers are sufficiently refined and a uniform fiber length and fiber diameter can be obtained. Be done.
The modification method for modifying the cellulose raw material is not particularly limited, and for example, chemical modification such as oxidation (carboxylation), etherification (carboxymethylation), cationization, esterification, phosphorylation, silane coupling, and fluorination. Can be mentioned. Of these, oxidation (carboxylation), etherification (carboxymethylation), cationization, and esterification are preferable, and detailed methods thereof will be described below.

(2-2-1) Oxidation (carboxylation) Cellulose Nanofibers When the cellulose raw material is modified by oxidation, the amount of carboxyl groups with respect to the absolute dry weight of the obtained cellulose oxide or cellulose nanofibers is preferably 0.5 mmol / g. As mentioned 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, still more preferably 2.0 mmol / g or less. Therefore, 0.5 mmol / g or more and 3.0 mmol / g or less is preferable, 0.8 mmol / g or more and 2.5 mmol / g or less is more preferable, and 1.0 mmol / g or more and 2.0 mmol / g or less is further preferable.
The method of oxidation is not particularly limited, but one example is cellulose in water using an oxidizing agent in the presence of an N-oxyl compound and a substance selected from the group consisting of bromide, iodide or a mixture thereof. Examples include a method of oxidizing a raw material. According to this method, the primary hydroxyl group at the C6 position of the glucopyranose ring on the surface of cellulose is selectively oxidized to generate a group selected from the group consisting of an aldehyde group, a carboxyl group, and a carboxylate group. 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 is a compound capable of generating a nitroxy radical. Examples of the nitroxy radical include 2,2,6,6-tetramethylpiperidin 1-oxyl (TEMPO). As the N-oxyl compound, any compound can be used as long as it is a compound that 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 capable of oxidizing cellulose as a raw material. For example, 0.01 mmol or more is preferable, and 0.02 mmol or more is more preferable with respect to 1 g of cellulose that has been completely dried. 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, still more preferably 0.02 mmol or more and 0.5 mmol or less, based on 1 g of dry cellulose.

The bromide is a compound containing bromine, and examples thereof include alkali metals bromide that can be dissociated and ionized in water, such as sodium bromide. Further, the iodide is a compound containing iodine, and examples thereof include an alkali metal iodide. The amount of bromide or iodide to be used may be selected within a range in which the oxidation reaction can be promoted. The total amount of bromide and iodide is preferably 0.1 mmol or more, more preferably 0.5 mmol or more, based on 1 g of 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 with respect to 1 g of dry cellulose.

The oxidizing agent is not particularly limited, and examples thereof include halogens, hypohalogenic acids, subhalogenic acids, perhalogenic acids, salts thereof, halogen oxides, and peroxides. Among them, hypochlorous acid or a salt thereof is preferable, hypochlorous acid or a salt thereof is more preferable, and sodium hypochlorite is further preferable because it is inexpensive and has a small environmental load. The amount of the oxidizing agent used is preferably 0.5 mmol or more, more preferably 1 mmol or more, still more preferably 3 mmol or more, based on 1 g of the dry cellulose. The upper limit is preferably 500 mmol or less, more preferably 50 mmol or less, further 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, still more preferably 1 mmol or more and 25 mmol or less, and most preferably 3 mmol or more and 10 mmol or less with respect to 1 g of dry cellulose. preferable. When an N-oxyl compound is used, the amount of the oxidizing agent used is preferably 1 mol or more with respect to 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 with respect to 1 mol of the N-oxyl compound.

Conditions such as pH and temperature during the oxidation reaction are not particularly limited, and in general, the oxidation reaction 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 lower, more preferably 30 ° C. or lower. 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 more, more preferably 10 or more. The upper limit is preferably 12 or less, more preferably 11 or less. Therefore, the pH of the reaction solution is preferably 8 or more and 12 or less, and more preferably 10 or more and 11 or less. Usually, the pH of the reaction solution tends to decrease because a carboxyl group is generated in the cellulose as the oxidation reaction progresses. 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 in the above range. Water is preferable as the reaction medium for oxidation because it is easy to handle and side reactions are unlikely to occur.

The reaction time in 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 in 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.
Oxidation may be carried out in two or more steps. For example, by oxidizing the oxidized cellulose obtained by filtration after the completion of the first-step reaction again under the same or different reaction conditions, the efficiency is not affected by the reaction inhibition by the salt produced as a by-product in the first-step reaction. Can be oxidized well.

Another example of the carboxylation (oxidation) method is a method of oxidizing by ozone treatment. By this oxidation reaction, the hydroxyl groups at at least the 2nd and 6th positions of the glucopyranose ring constituting the cellulose are oxidized, and the cellulose chain is decomposed. Ozone treatment is usually carried out by bringing a gas containing ozone into contact with a 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, and ^{more preferably 220 g / m 3} or less. Therefore, the ozone concentration in the gas is preferably at most 50 g / ^{m 3} or more 250 g / ^{m 3,} more preferably at most 50 g / ^{m 3} or more 220 g / ^{m 3.} 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, and 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 lower. Therefore, the ozone treatment temperature is usually 0 ° C. or higher and 50 ° C. or lower, and 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, it is possible to prevent the cellulose from being excessively oxidized and decomposed, and the yield of the oxidized cellulose becomes good.

The result obtained after the ozone treatment may be further subjected to a post-oxidation treatment using an oxidizing agent. The oxidizing agent used for the additional oxidation treatment is not particularly limited, and examples thereof include chlorine compounds such as chlorine dioxide and sodium chlorite; oxygen, hydrogen peroxide, persulfate, and peracetic acid. Examples of the method of the additional oxidation treatment include a method of dissolving these oxidizing agents in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and immersing the cellulose raw material in the oxidizing agent solution.

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

(2-2-2) Etherealization (carboxymethylation) Cellulose nanofibers As etherification, carboxymethyl (ether) formation, methyl (ether) conversion, ethyl (ether) conversion, cyanoethyl (ether) conversion, hydroxyethyl (ether) Examples thereof include etherification, hydroxypropyl (ether) conversion, ethyl hydroxyethyl (ether) conversion, and hydroxypropylmethyl (ether) conversion. The method of carboxymethylation will be described below as an example.
When the cellulose raw material is modified by carboxymethylation, the degree of carboxymethyl group substitution per anhydrous glucose unit in the obtained carboxymethylated cellulose or cellulose nanofiber is preferably 0.01 or more, more preferably 0.05 or more. It is more preferably 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 further preferably 0.10 or more and 0.35 or less.

The method of carboxymethylation is not particularly limited, and examples thereof include a method of marcelifying a cellulose raw material as a bottoming raw material and then etherifying it. Examples of the solvent used in the carboxymethylation reaction include water, alcohol (for example, 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 the 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 by weight with respect to the cellulose raw material. The upper limit is not particularly limited, but is 20 times by weight. Therefore, the amount of the solvent is preferably 3 times by weight or more and 20 times by weight or less.

Mercerization is usually carried out by mixing a bottoming material and a mercerizing agent. Examples of the mercerizing agent include alkali metals hydroxide such as sodium hydroxide and potassium hydroxide. The amount of the mercerizing agent used is preferably 0.5 times by mole or more, more preferably 1.0 times by mole or more, and further preferably 1.5 times by mole or more per anhydrous glucose residue of the bottoming material. The upper limit is usually 20 times or less, preferably 10 times or less, and more preferably 5 times or less. Therefore, 0.5-fold molars or more and 20-fold molars or less are preferable, 1.0-fold molars or more and 10-fold molars or less are more preferable, and 1.5-fold molars or more and 5-fold molars or less are further preferable.
The reaction temperature for mercerization is usually 0 ° C. or higher, preferably 10 ° C. or higher. The upper limit is usually 70 ° C. or lower, preferably 60 ° C. or lower. 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 longer, preferably 30 minutes or longer. The upper limit is usually 8 hours or less, preferably 7 hours or less. Therefore, it 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 the carboxymethylating agent include sodium monochloroacetate. The amount of the carboxymethylating agent added is usually preferably 0.05 times by mole or more, more preferably 0.5 times by mole or more, and further preferably 0.8 times by mole or more per glucose residue of the cellulose raw material. The upper limit is usually 10.0 times or less, preferably 5 times or less, more preferably 3 times or less, and therefore preferably 0.05 times or more and 10.0 times or less, more preferably. It is 0.5 times by mole or more and 5 times by mole or less, and more preferably 0.8 times by mole or more and 3 times by 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 higher and 90 ° C. or lower, preferably 40 ° C. or higher and 80 ° C. or lower. 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. If necessary, the reaction solution may be stirred during the carboxymethylation reaction.

The degree of carboxymethyl substitution per glucose unit of carboxymethylated cellulose nanofibers may be measured, for example, by the following method. That is, 1) Approximately 2.0 g of carboxymethylated cellulose (absolutely dried) is precisely weighed and placed in an Erlenmeyer flask with a 300 mL stopper. 2) Add 100 mL of a solution prepared by adding 100 mL of special grade concentrated nitric acid to 1000 mL of methanol nitrate, and shake for 3 hours to convert the carboxymethyl cellulose salt (carboxymethylated cellulose) into hydrogen-type carboxymethylated cellulose. 3) Weigh 1.5 to 2.0 g of hydrogen-type carboxymethylated cellulose (absolutely dry) and put it in an Erlenmeyer flask with a 300 mL stopper. 4) Wet hydrogen-type carboxymethylated cellulose with 15 mL of 80% methanol, add 100 mL of 0.1 N NaOH, and shake at room temperature for 3 hours. 5) Using phenolphthalein as an indicator, back titrate excess NaOH with _{0.1 N H 2} SO _4. 6) Calculate the degree of carboxymethyl substitution (DS) 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 1 g of hydrogen-type carboxymethylated cellulose
Amount of NaOH (mL)
F': 0.1N H ₂ SO ₄ factor F: 0.1N NaOH factor

(2-2-3) Cationized Cellular Nanofibers When a cellulose raw material is modified by cationization, the obtained cationized cellulose nanofibers have a cation such as ammonium, phosphonium, or sulfonium, or a group having the cation in the molecule. It may be included. The cationized cellulose nanofibers preferably contain a group having ammonium, and more preferably contain a group having quaternary ammonium.

The cationization method is not particularly limited, and examples thereof include a method in which a cationizing agent and a catalyst are reacted with a cellulose raw material in the presence of water and / or alcohol. Examples of the cationizing agent include glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrialkylammonium hydrite (eg, 3-chloro-2-hydroxypropyltrimethylammonium hydrite), and halohydrin forms thereof. By using any of these, cationized cellulose having a group containing quaternary ammonium can be obtained. Examples of the catalyst include alkali metals hydroxide 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 the catalyst is preferably 0.5% by weight or more, more preferably 1% by weight or more, based on 100% by weight of the 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 the 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. If necessary, the reaction solution may be stirred 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 cation substitution indicates the number of introduced substituents per unit structure (glucopyranose ring) constituting cellulose. In other words, the degree of cation substitution is defined as "the value obtained by dividing the number of moles of introduced substituents by the total number of moles of hydroxyl groups of 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, still 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 further preferably 0.03 or more and 0.20 or less. By introducing a cationic substituent into cellulose, the celluloses are electrically repelled from each other. Therefore, cellulose into which a cation substituent has been introduced can be easily nano-defibrated. When the degree of cation substitution per glucose unit is 0.01 or more, nano-defibration can be sufficiently performed. On the other hand, when the degree of cation substitution per glucose unit is 0.40 or less, swelling or dissolution can be suppressed, whereby the fiber morphology can be maintained, and a situation that cannot be obtained as nanofibers can be prevented. be able to.

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

(2-2-4) Esterified Cellulose Nanofiber The method of esterification is not particularly limited, and examples thereof include a method of reacting the following compound A with a cellulose raw material. Examples of the method of reacting the compound A with the cellulose raw material include a method of mixing the powder or the aqueous solution of the compound A with the cellulose raw material, a method of adding the aqueous solution of the compound A to the slurry of the cellulose raw material, and the like. Of these, a method of mixing an aqueous solution of compound A with a cellulose raw material or a slurry thereof is preferable because the uniformity of the reaction is increased and the esterification efficiency is increased.

Examples of the compound A include phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphoric acid, and esters thereof. Compound A may be in the form of a salt. Among the above, a phosphoric acid-based compound is preferable because it is low in cost, easy to handle, and the phosphoric acid group can be introduced into the cellulose of the pulp fiber to improve the defibration efficiency. The phosphoric acid-based compound may be a compound having a phosphoric acid group, for example, phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, diphosphate. Examples thereof include potassium hydrogen hydrogen, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium metaphosphate and the like. .. The phosphoric acid-based compound used may be one kind or a combination of two or more kinds. Of these, from the viewpoints of high efficiency of introducing phosphoric acid groups, easy defibration in the following defibration steps, and easy industrial application, phosphoric acid, sodium phosphate of phosphoric acid, potassium salt of phosphoric acid, and phosphoric acid The ammonium salt of is preferable, and sodium dihydrogen phosphate and disodium hydrogen phosphate are more preferable. Further, since the uniformity of the reaction is enhanced and the efficiency of introducing a phosphoric acid group is increased, it is preferable to use an aqueous solution of a phosphoric acid-based compound for esterification. The pH of the aqueous solution of the phosphoric acid-based compound is preferably 7 or less because the efficiency of introducing the phosphoric acid group is high, and more preferably 3 or more from the viewpoint of suppressing the hydrolysis of pulp fibers.

Examples of the esterification method include the following methods. Compound A is added to a suspension of a cellulose raw material (for example, a solid content concentration of 0.1 to 10% by weight) with stirring to introduce a phosphate group into cellulose. When the cellulose raw material is 100 parts by weight and the compound A is a phosphoric acid-based compound, the amount of the compound A added is preferably 0.2 parts by weight or more and more preferably 1 part by weight or more as the amount of phosphorus element. Thereby, the yield of the 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. As a result, 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, and more preferably 1 part by weight or more and 400 parts by weight or less.

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

Compound B is a nitrogen-containing compound that exhibits basicity. "Exhibiting basicity" usually means that the aqueous solution of Compound B exhibits a pink to red color in the presence of a phenolphthalein indicator, or that the pH of the aqueous solution of Compound B is greater than 7. The nitrogen-containing compound exhibiting basicity is not particularly limited as long as the effects of the present invention are exhibited, but a compound having an amino group is preferable. For example, urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine and the like can be mentioned. Of these, urea is preferable because it is low in 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, and more preferably 100 parts by weight or more and 700 parts by weight or less when the cellulose raw material is 100 parts by weight. The reaction temperature is preferably 0 ° C. or higher and 95 ° C. or lower, and 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 conditions of the esterification reaction are within any of these ranges, it is possible to prevent the cellulose from being excessively esterified and easily dissolved, and it is possible to improve the yield of the phosphate esterified cellulose. ..

After reacting the cellulose raw material with compound A, an esterified cellulose suspension is usually obtained. It is preferable that the esterified cellulose suspension is dehydrated if necessary, and heat treatment is performed after the dehydration. As a result, 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 contained during the heat treatment, and after removing the water, 100 ° C. or higher and 170 ° C. It is more preferable to heat-treat at ° C. or lower.

In phosphoric acid esterified cellulose, a phosphate group substituent is introduced into the cellulose raw material, and the celluloses electrically repel each other. Therefore, the phosphate esterified cellulose can be easily nano-defibrated. The degree of phosphoric acid group substitution per glucose unit of the phosphoric acid esterified cellulose is preferably 0.001 or more. As a result, sufficient defibration (for example, nano-defibration) can be carried out. The upper limit is preferably 0.40. This makes it possible to prevent the swelling or dissolution of the phosphate esterified cellulose and prevent the situation where nanofibers cannot be obtained. Therefore, it is preferably 0.001 or more and 0.40 or less. It is preferable that the phosphoric acid esterified cellulose is subjected to a washing treatment such as washing with cold water after boiling. As a result, defibration can be performed efficiently.

(2-3) Defibering The defibration of the cellulose raw material may be performed before or after the modification treatment of the cellulose raw material. Further, the defibration may be performed at one time or a plurality of times. In the case of multiple times, the timing of each defibration may be any time.
The device used for defibration is not particularly limited, and examples thereof include high-speed rotary type, colloid mill type, high pressure type, roll mill type, ultrasonic type and the like, and a high pressure or ultrahigh pressure homogenizer is preferable, and a wet high pressure type is preferable. Alternatively, an ultrahigh pressure homogenizer is more preferable. The apparatus is preferably one capable of applying a strong shearing force to a cellulose raw material or a modified cellulose (usually a dispersion liquid). The pressure that can be applied by the device is preferably 50 MPa or more, more preferably 100 MPa or more, and even more preferably 140 MPa or more. The apparatus is preferably a wet high-pressure or ultra-high-pressure homogenizer capable of applying the above pressure to a cellulose raw material or modified cellulose (usually a dispersion) and applying a strong shearing force. As a result, defibration can be performed efficiently.

When defibration is performed on a dispersion of a cellulose raw material, the solid content concentration of the cellulose raw material in the dispersion is usually 0.1% by weight or more, preferably 0.2% by weight or more, more preferably 0.3. Weight% or more. As a result, the amount of liquid becomes appropriate with respect to the amount of the cellulose fiber raw material, which is efficient. The upper limit is usually 10% by weight or less, preferably 6% by weight or less. This makes it possible to maintain liquidity.
Prior to defibration (preferably defibration with a high-pressure homogenizer) or, if necessary, a dispersion treatment before defibration, pretreatment may be performed if necessary. The pretreatment may be performed using a mixing, stirring, emulsifying, or dispersing device such as a high-speed shear mixer.

(2-4) Cellulose Nanofibers In the present invention, the cellulose nanofibers may be used as the dispersion liquid as it is, but by performing a drying treatment as necessary, the solvent is partially or completely removed to obtain a wet solid. It may be used as a substance or a dry solid substance. Here, the wet solid is a solid in an intermediate mode between the dispersion and the dry solid.
When performing the drying treatment, in order to improve the redispersibility, the water-soluble polymer may be mixed in advance with the dispersion liquid of the cellulose nanofibers, and then the drying treatment may be performed. Examples of the water-soluble polymer include cellulose derivatives (carboxymethyl cellulose and its salts, methyl cellulose, hydroxypropyl cellulose, ethyl cellulose), xanthan gum, xyloglucan, dextrin, dextran, carrageenan, locust bean gum, alginic acid, alginate, purulan, starch, and the like. Carrageenan, waste powder, positive starch, phosphorylated starch, corn starch, gum arabic, locust bean gum, gellan gum, gellan gum, polydexstrose, pectin, chitin, water-soluble chitin, chitosan, casein, albumin, soybean protein lysate, peptone, polyvinyl Alcohol, polyacrylamide, sodium polyacrylate, polyvinylpyrrolidone, vinylacetate, polyamino acid, polylactic acid, polyapple acid, polyglycerin, latex, rosin-based sizing agent, petroleum resin-based sizing agent, urea resin, melamine resin, epoxy resin , Polyamide resin, polyamide / polyamine resin, polyethyleneimine, polyamine, vegetable gum, polyethylene oxide, hydrophilic cross-linked polymer, polyacrylic acid salt, starch polyacrylic acid copolymer, tamarind gum, gellan gum, pectin, guar gum and colloidal silica. Examples include one or more mixtures thereof. Among these, it is preferable to use carboxymethyl cellulose and a salt thereof from the viewpoint of compatibility.

The dry solids and wet solids of cellulose nanofibers may be prepared by drying a dispersion of cellulose nanofibers or a mixed solution of cellulose nanofibers and a water-soluble polymer. The drying method is not particularly limited, and examples thereof include spray drying, squeezing, air drying, hot air drying, and vacuum drying. Examples of the drying device include a continuous tunnel drying device, a band drying device, a vertical drying device, a vertical turbo drying device, a multi-stage disk drying device, an aeration drying device, a rotary drying device, an air flow drying device, and a spray dryer drying device. , Spray drying device, Cylindrical drying device, Drum drying device, Screw conveyor drying device, Rotating drying device with heating tube, Vibration transport drying device, etc., Batch type box drying device, Vacuum box type drying device, Stirring drying device, 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. As a result, heat energy can be uniformly supplied directly to the object to be dried, so that energy efficiency can be improved. In addition, the object to be dried can be recovered immediately without applying heat more than necessary.

Since the cellulose nanofibers used in the present invention are excellent in fluidity and gas barrier properties, the air shielding property can be enhanced by impregnating or coating the base paper.

The preferable coating amount of the cellulose nanofibers is 0.2 g / m ² or more and 5.0 g / m ² or less, and preferably 0.5 g / m ² or more and 3.0 g / m as the solid content coating amount per one side. ^{It is 2} or less. If the coating amount of the cellulose nanofibers ^{is less than 0.2 g / m 2} , the improvement in air permeation resistance is small and the air shielding property is insufficient. If the coating amount ^{exceeds 5.0 g / m 2} , the moisture permeability is lowered, which is not preferable.

(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, and guanidine sulfamate. A guanidine salt such as guanidine hydrochloride can be used, and calcium chloride, which has excellent hygroscopicity and is inexpensive, can be preferably used. These compounds may be used alone or in admixture of two or more. Further, among the hygroscopic agents, those that can be used as a flame retardant can also be blended to impart flame retardancy to the base paper.

The preferable coating amount of the hygroscopic agent is 0.5 g / m ² or more and 20 g / m ² or less, and preferably 1.0 g / m ² or more and 15 g / m ² or less. If the amount of the hygroscopic agent applied ^{is less than 0.5 g / m 2} , the moisture permeability will be insufficient. Further, if the coating amount ^{exceeds 20 g / m 2} , the amount of moisture absorbed becomes excessive, and in an environment of high temperature and high humidity, there is a risk of dew condensation and outflow of the hygroscopic agent, which is not preferable. The hygroscopic agent may be impregnated on the entire base paper or may be applied on one side or both sides as long as it is within the above coating amount.

(4) Total heat exchange element paper The total heat exchange element paper of the present invention is obtained by impregnating or coating a base paper made of papermaking fibers with a chemical solution containing cellulose nanofibers and a chemical solution containing a hygroscopic agent. Can be manufactured by
It is preferable that the chemical solution containing the cellulose nanofibers and the chemical solution containing the hygroscopic agent are the same chemical solution because the coating amount of each component can be accurately estimated. A chemical solution containing cellulose nanofibers and a hygroscopic agent can be obtained by adding a hygroscopic agent to a dispersion of cellulose nanofibers. The ratio of the hygroscopic agent added to the cellulose nanofiber dispersion is 2 parts by mass or more and 30 parts by mass or less, preferably 5 parts by mass or more and 20 parts by mass or less of the hygroscopic agent with respect to 1 part by mass of the cellulose nanofibers in terms of solid content. Mix. If the amount of the hygroscopic agent is less than 2 parts by mass, sufficient moisture permeability cannot be obtained. Further, if the blending ratio of the hygroscopic agent exceeds 30 parts by mass, the air permeation resistance is insufficient, which is not preferable.

Various commonly used functional aids such as water resistant 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. .. When the chemical solution is applied to the base paper, it is applied to at least one side, but when it is applied to both sides, the same chemical solution may be used on both sides, and chemical solutions having different formulations and compositions may be used on each side.

The total heat exchange element paper of the present invention can exhibit excellent air permeation resistance by applying cellulose nanofibers. The water-soluble polymer substance can be added within a range in which blocking does not occur, but the amount thereof is preferably less than ^{2.0 g / m 2} , and more preferably less than ^{0.5 g / m 2.} preferable. Examples of the water-soluble polymer substance include polyvinyl alcohol, starch, starch derivatives, polyethylene oxide, alginate, carboxymethyl cellulose salt, methyl cellulose, hydroxyethyl cellulose and the like.

As a method of applying the chemical solution containing the cellulose nanofibers prepared as described above to the base paper, a rod coater, a die coater, a curtain coater, a two-roll size press, a rod metering size press, a gate roll coater, and a blade Examples thereof include a method of applying with a coating machine such as a coater and a method of impregnating.

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, and an infrared heater dryer can be used alone or in combination. ..

The obtained coated paper may be subjected to calendar processing with a super calendar, a thermal pressure roll, or the like, if necessary. By applying the calendar treatment, the thickness is reduced and the thermal conductivity in the thickness direction is improved, and by increasing the density, the air permeation resistance is increased and the air shielding property is improved.

Thus, a paper containing a papermaking fiber, a hygroscopic agent, and cellulose nanofibers can be obtained, and the 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 70 g / m ² or less, more preferably 15 g / m ² or more and 40 g / m ² or less, and most preferably 20 g / m ² or more and 35 g / m ^2. It is as follows. If the basis weight is ^{less than 10 g / m 2} , the strength is remarkably lowered and the workability when processing into a total heat exchange element is lowered. If the basis weight exceeds 70 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 8 μm or more and 80 μm or less, and within this range, the thinner the total heat exchange element paper, the higher the total heat exchange efficiency tends to be, which is more preferable. If the thickness is less than 8 μm, the strength is remarkably lowered and the workability when processing into a total heat exchange element is lowered. Further, if the thickness exceeds 80 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 is preferably 700 seconds or more. If the air permeation resistance is less than 700 seconds, there is not much difference from the air permeation resistance of the base paper, and there is no point in applying cellulose nanofibers. When the air permeation resistance of the heat exchange element paper used in the heat exchange ventilator becomes high, it becomes difficult for air to mix between the fresh air supply and the dirty exhaust gas, and in particular, the carbon dioxide gas transfer rate decreases. The air shielding property that separates air and exhaust is improved. According to Patent Document 3, the carbon dioxide transfer rate can be suppressed to 5% or less when the air permeation resistance is 200 seconds or more, and the carbon dioxide transfer rate can be suppressed to 1% or less when the air permeation resistance is 5000 seconds or more. Is disclosed, and Patent Document 5 states that it can be used as a total heat exchange element paper if the air permeation resistance is 500 seconds or more.

Moisture permeability of the total heat exchange element sheet is preferably at least 800g ^/ m 2 · 24hr, further preferably 1000g ^/ m 2 · 24hr or more. The moisture permeability is effective as an indicator of the latent heat exchange efficiency of the total heat exchange element sheets, the moisture permeability is higher latent heat exchange efficiency is high, whereas, latent heat moisture permeability is required is less than 800g / m 2 ^· 24hr Exchange efficiency cannot be obtained.

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

[Measuring method]
(1) Basis weight A sample having a size of 250 mm × 200 mm is placed in a weighing bottle of known weight, dried at 105 ° C. for 2 hours, then weighed, and the absolute dry weight per square meter of the sample is calculated. The amount was (g / m ² ).

(2) Adhesion amount The wet weight of the coating liquid applied per 1 square meter of the base paper was multiplied by the solid content concentration of the coating liquid to obtain the total adhesion amount (g / m ² ). In addition, the total adhesion amount is divided according to the solid content composition ratio of the cellulose nanofibers contained in the coating liquid and the hygroscopic agent, and the cellulose nanofiber adhesion amount (g / m ² ) and the hygroscopic agent adhesion amount (g / m ² ). Was calculated.

(3) Thickness After harmonizing the sample in a constant temperature and humidity chamber at 25 ° C. and 35% RH for 1 hour, measure the thickness of 5 points with a hybrid paper thickness gauge, calculate the average value, and calculate the thickness (thickness). μm).

(4) Moisture Permeability The measurement was performed by changing the temperature and humidity conditions of the measurement environment using the instruments specified in JIS Z0208 (1976) Permeability (cup method). A moisture permeable cup equipped with a test piece was allowed to stand in a constant temperature and humidity chamber set at 20 ° C. and 65% RH for 24 hours to measure the weight increase, and the weight change per 1 square meter of measurement area was calculated for 24 hours. and the moisture permeability ^(g / m 2 · 24hr) Te.

(5) Air permeability resistance JIS P8117 (2009) Air permeability resistance (King) The average value of 5 measurements was calculated in accordance with the Wang Lab test machine method described in Air permeability and air permeability resistance. Lab) (seconds).

[Manufacturing of base paper]
40% by mass of coniferous bleached kraft pulp and 60% by mass of broadleaf bleached kraft pulp are mixed and beaten so as to have a Canadian standard freshness of 250 ml CSF. Product name: WS-535) is added in an absolute dry amount of 0.25% by mass to prepare the pulp making material, and after papermaking with a long net paper machine, super calendar processing is performed to produce a basis weight of 32 g / m ² (absolutely dry). Weight) coating base paper was obtained.

[Manufacture of carboxymethylated cellulose nanofibers]
In a stirrer capable of mixing pulp, 200 g of coniferous bleached kraft pulp (manufactured by Nippon Paper Industries, Ltd.) by dry mass and 111 g of sodium hydroxide by dry mass (2.25 times mol per anhydrous glucose residue of the base material). ) Was added, and water was added so that the pulp solid content was 20% (w / v). Then, after stirring at 30 ° C. for 30 minutes, 216 g of sodium monochloroacetate (in terms of active ingredient, 1.5 times by mole per glucose residue of pulp) was added. After stirring for 30 minutes, the temperature was raised to 70 ° C. and the mixture was stirred for 1 hour. Then, the reaction product was taken out, neutralized and washed to obtain a carboxymethylated pulp having a carboxymethyl substitution degree of 0.25 per glucose unit. This was made into a solid content of 1.2% with water, and defibrated by treating with a high-pressure homogenizer at a pressure of 20 ° C. and 150 MPa five times to obtain carboxymethylated cellulose nanofibers (hereinafter referred to as CM-CNF). The average fiber diameter was 15 nm and the aspect ratio was 50.

<Example 1>
45 parts by mass of water and 17.6 parts by mass of calcium chloride (manufactured by Central Glass Co., Ltd.) are added to 90 parts by mass of an aqueous dispersion of CM-CNF (solid content concentration 1.2% by mass) and dispersed with a winged stirrer. , Dissolved to prepare a coating solution. The above coating liquid was applied to one side of the base paper with a Meyer bar and dried to obtain the total heat exchange element paper of the present invention. The amount of adhesion, air permeability resistance, and moisture permeability of this paper were measured. The results are shown in Table 1.

<Example 2>
Add 5.52 parts by mass of calcium chloride (manufactured by Central Glass Co., Ltd.) to 90 parts by mass of an aqueous dispersion of CM-CNF (solid content concentration 1.2% by mass), disperse and dissolve with a winged stirrer, and apply. The liquid was prepared. The coating liquid was applied to one side of the base paper with a Meyer bar and dried to obtain the total heat exchange element paper of the present invention. The amount of adhesion, air permeability resistance, and moisture permeability of this paper were measured. The results are shown in Table 1.

<Example 3>
The total heat exchange element paper of the present invention was obtained in the same manner as in Example 2 except that the compounding portion of calcium chloride was 11.7 parts by mass. The amount of adhesion, air permeability resistance, and moisture permeability of this paper were measured. The results are shown in Table 1.

<Example 4>
Add 30 parts by mass of water and 11.7 parts by mass of calcium chloride (manufactured by Central Glass Co., Ltd.) to 60 parts by mass of an aqueous dispersion of CM-CNF (solid content concentration 1.2% by mass) and disperse with a winged stirrer. , Dissolved to prepare a coating solution. The coating liquid was applied to one side of the base paper with a Meyer bar and dried to obtain the total heat exchange element paper of the present invention. The amount of adhesion, air permeability resistance, and moisture permeability of this paper were measured and shown in Table 1.

[Manufacturing of carboxylated cellulose nanofibers]
5.00 g (absolutely dry) of bleached unbeaten kraft pulp (whiteness 85%) derived from coniferous trees, 39 mg (0.05 mmol per 1 g of absolute dry cellulose) of TEMPO (Sigma Aldrich) and 514 mg of sodium bromide (absolutely dry). It was added to 500 ml of an aqueous solution in which 1.0 mmol) was dissolved in 1 g of cellulose, and the mixture was stirred until the pulp was uniformly dispersed. An aqueous sodium hypochlorite solution was added to the reaction system so that the sodium hypochlorite content was 5.5 mmol / g, and the oxidation reaction was started at room temperature. Although the pH in the system decreased during the reaction, a 3M aqueous sodium hydroxide solution was sequentially added to adjust the pH to 10. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system did not change.
The mixture after the reaction was filtered through a glass filter to separate the pulp, and the pulp was thoroughly washed with water to obtain oxidized pulp (carboxylated cellulose). The pulp yield at this time was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.6 mmol / g. This is adjusted to 1.1% (w / v) with water, treated three times with an ultra-high pressure homogenizer (20 ° C., 150 MPa), and an aqueous dispersion of carboxylated cellulose nanofibers (hereinafter referred to as T-CNF). Got The average fiber diameter was 3 nm and the aspect ratio was 250.

<Example 5>
60 parts by mass of water and 25.2 parts by mass of calcium chloride (manufactured by Central Glass Co., Ltd.) are added to 120 parts by mass of an aqueous dispersion of T-CNF (solid content concentration 1.1% by mass) and dispersed with a winged stirrer. , Dissolved to prepare a coating solution. The coating liquid was applied to one side of the base paper with a Meyer bar and dried to obtain a single-sided coated paper of T-CNF and calcium chloride. On the opposite side of this single-sided coated paper, Meyer added 45 parts by mass of water to 90 parts by mass of the aqueous dispersion of T-CNF (solid content concentration 1.1% by mass) and dispersed it with a winged stirrer. After coating with a bar, it was dried to obtain a total heat exchange element paper of the present invention coated on both sides. The amount of adhesion, air permeability resistance, and moisture permeability of this paper were measured. The results are shown in Table 1.

[Manufacture of cationized cellulose nanofibers]
To a pulper capable of stirring pulp, add 200 g of softwood bleached kraft pulp (manufactured by Nippon Paper Industries, Ltd.) by dry weight and 24 g of sodium hydroxide by dry weight, and add water so that the pulp solid concentration becomes 15%. rice field. Then, after stirring at 30 ° C. for 30 minutes, the temperature was raised to 70 ° C., and 200 g (in terms of active ingredient) of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added as a cationizing agent. After reacting for 1 hour, the reactants were taken out, neutralized and washed to give a cation-modified pulp with a cation substitution degree of 0.05 per glucose unit. This was set to a solid concentration of 1.2% and treated twice with a high-pressure homogenizer at a pressure of 20 ° C. and 140 MPa to obtain cationized cellulose nanofibers (hereinafter referred to as C-CNF). The average fiber diameter was 25 nm and the aspect ratio was 50.

<Example 6>
45 parts by mass of water and 17.6 parts by mass of calcium chloride (manufactured by Central Glass Co., Ltd.) are added to 90 parts by mass of an aqueous dispersion of C-CNF (solid content concentration 1.2% by mass) and dispersed with a winged stirrer. , Dissolved to prepare a coating solution. The coating liquid was applied to one side of the base paper with a Meyer bar and dried to obtain a single-sided coated paper of C-CNF and calcium chloride. On the opposite side of this single-sided coated paper, Meyer added 45 parts by mass of water to 90 parts by mass of an aqueous dispersion of C-CNF (solid content concentration 1.2% by mass) and dispersed it with a winged stirrer. The total heat exchange element paper of the present invention was obtained by coating with a bar and drying to obtain coating on both sides. The amount of adhesion, air permeability resistance, and moisture permeability of this paper were measured. The results are shown in Table 1.

<Example 7>
45 parts by mass of water and 17.6 parts by mass of calcium chloride (manufactured by Central Glass Co., Ltd.) are added to 90 parts by mass of an aqueous dispersion of CM-CNF (solid content concentration 1.2% by mass) and dispersed with a winged stirrer. , Dissolved to prepare a coating solution. The coating liquid was applied to one side of the base paper with a Meyer bar and dried to obtain a single-sided coated paper of CM-CNF and calcium chloride. On the opposite side of this single-sided coated paper, Meyer added 30 parts by mass of water to 60 parts by mass of the aqueous dispersion of CM-CNF (solid content concentration 1.2% by mass) and dispersed it with a winged stirrer. The total heat exchange element paper of the present invention was obtained by coating with a bar and drying to obtain coating on both sides. The amount of adhesion, air permeability resistance, and moisture permeability of this paper were measured. The results are shown in Table 1.

<Example 8>
Add 30 parts by mass of water and 3.6 parts by mass of potassium acetate (manufactured by Wako Pure Chemical Industries, Ltd.) to 60 parts by mass of the aqueous dispersion of CM-CNF (solid content concentration 1.2% by mass), and stirrer with wings. The coating liquid was prepared by dispersing and dissolving in. The coating liquid was applied to one side of the base paper with a Meyer bar and dried to obtain the total heat exchange element paper of the present invention. The amount of adhesion, air permeability resistance, and moisture permeability of this paper were measured.
The results are shown in Table 1.

<Example 9>
A stirrer with wings by adding 30 parts by mass of water and 3.6 parts by mass of lithium chloride (manufactured by Wako Pure Chemical Industries, Ltd.) to 60 parts by mass of the aqueous dispersion (solid content concentration 1.2% by mass) of CM-CNF. The coating liquid was prepared by dispersing and dissolving in. The coating liquid was applied to one side of the base paper with a Meyer bar and dried to obtain the total heat exchange element paper of the present invention. The amount of adhesion, air permeability resistance, and moisture permeability of this paper were measured. The results are shown in Table 1.

<Evaluation of blocking property>
Two 50 mm × 80 mm test pieces were cut out from the double-sided coated paper of Example 5, and the F surface (felt surface) side and the W surface (wire surface) side were overlapped in a constant temperature and humidity chamber at 20 ° C. and 75% RH. After harmonizing for 15 minutes, the two test pieces were crimped through a 1-nip type calendar device (manufactured by Yuri Roll Machinery Co., Ltd.) having a roll temperature of 90 ° C. and a roll wire pressure of 40 kg / cm. Peel off one end of the crimped test piece in the longitudinal direction, and sandwich one end between the sample grips attached to the digital force gauge (manufactured by Nidec-Shimpo Co., Ltd., device name: FGP-0.5 type). The other end was grasped by hand and pulled, peeled by about 70 mm in the longitudinal direction, and the maximum value of the peel resistance was read to obtain the peel resistance per sample width of 5 cm. The peeling resistance of the test piece forcibly crimped using the thermal pressure roll was 50 g / 5 cm or less, and the blocking property was evaluated to be extremely weak.
Further, also in the blocking property of the other examples, the crimped part did not peel off and the base material was not destroyed.

<Comparative example 1>
The total heat exchange element paper of the present invention was obtained in the same manner as in Example 1 except that CM-CNF was not blended. The amount of adhesion, air permeability resistance, and moisture permeability of this paper were measured. The results are shown in Table 1. The base paper had a thin paper thickness and high air permeability resistance due to the high density in the calendar processing, but the density, thickness, and air permeability resistance were calendar processed due to the wetting and drying action of the coating process. It returned to a state close to the previous state, the paper thickness was thick, and the air permeability resistance was low.
<Comparative example 2>
A total heat exchange element paper was obtained in the same manner as in Example 1 except that calcium chloride was not blended and the amount of CM-CNF adhered was 0.3 g / m ^2. The amount of adhesion, air permeability resistance, and moisture permeability of this paper were measured. The results are shown in Table 1.
<Comparative example 3>
The air permeability resistance and moisture permeability of the uncoated base paper were measured. The results are shown in Table 1.

<Comparative example 4>
On one side of flame-retardant paper (air permeability resistance 4 seconds) with a basis weight of 55 g / m ² , 14 parts by mass of polyvinyl alcohol (manufactured by Kuraray Co., Ltd.) and lithium chloride (manufactured by Wako Pure Chemical Industries, Ltd.) 10 in terms of solid content. A coating liquid consisting of 76 parts by mass and 76 parts by mass of water was applied and dried to prepare a total heat exchange element paper coated with a water-soluble polymer layer containing a hygroscopic agent on one side. The amount of the hygroscopic agent applied to this paper was 2.5 g / m ² in terms of solid content, and the amount of polyvinyl alcohol applied was 3.5 g / m ² in terms of solid content. The air resistance is 23000 seconds, the moisture permeability is 1200g ^/ m 2 · 24hr, had sufficient air shielding properties and moisture permeability as the total heat exchange element sheets.
This paper was subjected to a forced crimping test using a thermal pressure roll in the same manner as the blocking property evaluation, and the peeling resistance was measured. Since the material was broken, it was evaluated that the blocking property was very strong.

As is clear from Examples 1 to 9, even if a base paper made of a raw material that does not be beaten highly is used, by providing a coating layer containing cellulose nanofibers, the air permeability resistance is maintained without lowering the moisture permeability. Can be enhanced. Further, even when double-sided coating is applied, the moisture permeability of single-sided coating can be maintained and the air permeability resistance can be significantly increased.

Claims (4)

A base paper containing pulp of 100 ml CSF or more and 500 ml CSF or less as fibers for papermaking, and
A coating layer containing a hygroscopic agent and cellulose nanofibers on at least one surface of the base paper,
Have,
The hygroscopic agent is any one of an alkali metal salt, an alkaline earth metal salt, an ammonium salt, and a guanidine salt.
Total heat exchange element paper characterized by an air permeation resistance of 700 seconds or more. The total heat exchange element paper according to claim 1, wherein the papermaking fiber is a cellulose fiber. The total heat according to claim 1 or 2, wherein the cellulose nanofiber is at least one of a carboxymethylated cellulose nanofiber, a carboxylated cellulose nanofiber, a cationized cellulose nanofiber, and an esterified cellulose nanofiber. Interchangeable element paper. A chemical solution containing a hygroscopic agent and cellulose nanofibers is applied to at least one side of a base paper containing pulp of 100 ml CSF or more and 500 ml CSF or less as a papermaking fiber.
The desiccant, alkali metal salts, alkaline earth metal salts, ammonium salts, manufacturing method of a total heat exchange element sheets characterized by either Der Rukoto guanidine salt.