JPWO2018003492A1 - Total heat exchange element paper - Google Patents

Abstract

It is an object of the present invention to provide a total heat exchange element sheet which has high production efficiency at the time of paper making, hardly causes problems such as paper breakage at the time of element processing, and has high moisture absorption and release properties and air shielding properties. As a solution, a total heat exchange element paper containing papermaking fibers, a hygroscopic agent, and cellulose nanofibers is provided.

Description

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

In recent years, with the spread of air conditioning equipment such as cooling and heating, a ventilation heat exchanger that can exchange heat between supply air and exhaust air to recover temperature and humidity during ventilation has been used.
This heat exchanger is composed of a flat partition plate having heat conductivity and moisture permeability and a spacer plate which secures an air flow path by being sandwiched between two partition plates, and the partition plates and spacer plates are stacked in multiple layers. Have a basic structure. The spacer plate is a corrugated plate formed into a sawtooth-like or sinusoidal waveform, and the forming direction of the waveform is alternately changed in the orthogonal direction and sandwiched between the partition plates. Thus, between the layers formed of the spacer plate and the partition plate, the two systems of fluid passages are alternately arranged alternately at every other layer.

  The partition plate separates an air supply path for introducing fresh air into the room from the outside and an exhaust path for discharging dirty room air to the room outside, and heat exchange of latent heat simultaneously with sensible heat between the air supply and the exhaust. It has a function to perform. For this reason, the partition plate is required to have water vapor permeability indicated by heat conductivity and moisture permeability, and additionally, it is necessary to have flame retardancy and air shielding property so that the air supply and the exhaust are not mixed.

A total heat exchange element sheet is used as a material of a partition plate capable of meeting such requirements, and the following prior art is disclosed.
Patent Document 1 discloses a total heat exchanger element paper having moisture absorption and release properties and air shielding properties obtained by impregnating or coating a porous substrate with a mixed solution of a hygroscopic agent and a water-soluble polymer substance. There is.
In Patent Document 2, a total heat exchange element paper having excellent air shielding properties and hygroscopicity without using a water-soluble polymer substance by coating and using a hygroscopic agent on a base paper made of a material having a high degree of freeness. It is disclosed that can be obtained.
Patent Document 3 describes a partition member for a heat exchanger having a thickness of 10 to 50 microns and having excellent air shielding properties, in which an alkali metal salt is mixed with a hygroscopic agent.
Patent Document 4 discloses a moisture absorbing and desorbable total heat exchanger paper formed by blending microfibrillated cellulose and silica gel and aluminum hydroxide which are moisture absorbing and desorbing powders with papermaking fibers.
Patent Document 5 discloses a total heat exchanger paper using a paper base using calcium chloride as a moisture absorbent and blending an antiblocking agent.

Japanese Patent Publication No. 58-46325 International Publication No. 2002/099193 JP 2003-148892 Japanese Patent Application Laid-Open No. 11-189999 JP 2007-119969 A

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

  In addition, in the case of a paper in which a hygroscopic agent is added to a base paper having an enhanced air shielding property using a raw material having a high freeness as described in Patent Document 2 and Patent Document 3, the base paper is dense and air is transmitted. There is no need to impregnate or coat a water-soluble polymer substance to provide air shielding properties, and it has moisture absorbing and releasing properties and air shielding properties by impregnating or coating a chemical solution consisting of a hygroscopic agent and a flame retardant. Total heat exchange element paper is obtained. However, if the base paper has a high degree of refining, the water squeezing ability at the time of paper making is deteriorated and the production efficiency is lowered, and the obtained base paper is fragile and easily torn, and the processability is lowered when producing the heat exchange unit. There is a problem of

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

  As described in Patent Document 5, the raw material which beats the pulp constituting the base material to 200 to 600 ml with anomalous freeness (according to JIS P8121 except that the amount of pulp collected is 0.3 g) is ordinary freeness The measurement method is so high that it is difficult to measure, so the water squeezing ability at the time of papermaking is deteriorated and the production efficiency is lowered, and the obtained base paper is fragile and easily torn, and the processability at the time of producing the heat exchange unit May decrease.

  As described above, the total heat exchange element paper obtained by impregnating or coating the hygroscopic agent and the water-soluble polymer substance on the base paper is easily blocked, while the high retabilized base paper is impregnated or coated with the hygroscopic agent. There is a problem that the total heat exchange element paper provided with the moisture absorption and release property and the air shielding property by processing has a possibility that the production efficiency at the time of paper making and the processability at the time of heat exchange unit production may deteriorate.

  An object of the present invention is to provide a total heat exchange element sheet which is high in production efficiency at the time of paper making, hardly causes problems such as paper breakage at the time of element processing, and has high moisture absorbability and air shielding properties.

As a result of earnest research, the present inventors have developed a novel total heat exchange element paper in which the above-mentioned problems are solved.
The means for solving the problems of the present invention are as follows.
1. A total heat exchange element paper comprising a papermaking fiber, a hygroscopic agent, and cellulose nanofibers.
2. The papermaking fiber is a cellulose fiber. Total heat exchange element paper described in.
3. The cellulose nanofibers are characterized in that they are 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. The hygroscopic agent is any one of an alkali metal salt and an alkaline earth metal salt. ~ 3. Total heat exchange element paper according to any of the above.
5. The air resistance is 700 seconds or more. ~ 4. Total heat exchange element paper according to any of the above.
6. A method for producing a total heat exchange element sheet, comprising applying a chemical solution containing a hygroscopic agent and cellulose nanofibers on at least one side of a base paper comprising papermaking fibers.

  The total heat exchange element paper of the present invention has excellent air permeability resistance and moisture permeability by blending cellulose nanofibers, and can be suitably used for a heat exchanger. Since the total heat exchange element paper of the present invention does not need to use a highly beatable base paper, it is possible to prevent a decrease in production efficiency at paper making and a weakening of the base paper by making the base paper highly beaten. it can. Further, the total heat exchange element paper of the present invention can reduce the coating amount of the water-soluble polymer substance, and in some cases, the water-soluble polymer substance is unnecessary, so blocking does not easily occur, and the handling property and processing Excellent in quality.

Hereinafter, embodiments of the present invention will be described in detail.
(1) Fiber for papermaking The fiber for papermaking used as a raw material of the total heat exchange element paper of the present invention is obtained from non-wood raw materials such as softwood pulp, wood pulp such as hardwood pulp, flax, abaca, kenaf, bamboo, bagasse Cellulose fibers obtained from non-wood pulp etc. There are no particular limitations on the method of cooking cellulose fiber, the presence or absence of bleaching, and the method of bleaching. In addition to cellulose fibers, polyester fibers, nylon fibers, rayon fibers, synthetic fibers such as lyocell fibers, and semi-synthetic fibers can be blended for the purpose of improving adhesiveness, dimensional stability, shapeability and the like.

  The pulp used in the present invention is beaten in the range of 100 ml CSF to 500 ml CSF with Canadian standard freeness according to JIS P8121, and more preferably 200 ml CSF to 300 ml CSF. When the standard freeness of Canada is less than 100 ml CSF, the paper is densified to reduce voids, and when used as a base paper of the total heat exchange element paper, the coating agent hardly penetrates into the paper and the base paper It is not preferable because problems such as easy blocking due to localization of the hygroscopic agent etc. on the surface and increase in the amount of expansion and contraction due to humidity change occur. In addition, when the standard freeness of Canada exceeds 500 ml CSF, the amount of voids and the diameter of voids of the paper are increased, which is not preferable because the air shielding effect by the cellulose nanofibers becomes insufficient. As for the beating of pulp, a general beating apparatus such as a beater or refiner can be used, and there is no particular limitation on the beating apparatus and the beating method.

  The papermaking paper stock is blended with synthetic or semi-synthetic fibers, fillers, colorants, paper strength agents, wet paper strength agents, sulfate bands, cationized starch, retention aids, etc., as necessary. Are prepared.

  The above stock is formed by a general paper making method using a long mesh paper machine, a circular mesh paper machine, a short mesh paper machine, a twin wire paper machine or a paper machine combining them, etc. There is no particular limitation on the paper making method. If necessary, impregnate flame retardants, rust inhibitors, antiblocking agents, etc. with an on-machine coating device such as a size press or roll coater, and perform calendering with a machine calender, super calender, soft nip calender, etc. The base paper is obtained.

  The air resistance of the base paper is improved by the sealing function of the cellulose nanofibers impregnated or coated on the base paper, but in order to exert its effect sufficiently, the air resistance of the base paper itself is 50 seconds. It is required to be 650 seconds or less, preferably 150 seconds or more and 600 seconds or less, more preferably 200 seconds or more and 500 seconds or less. When the air permeability of the base paper is less than 50 seconds, the increase in air permeability after addition is small even if the cellulose nanofibers are added by impregnation or coating, and the air shielding properties of all heat exchange element paper are insufficient . When the air resistance of the base paper exceeds 650 seconds, the impregnated or coated chemical solution hardly penetrates into the interior of the base paper, and blocking by the chemical solution component in the vicinity of the surface of the base paper tends to occur, which is not preferable. The air resistance of the base paper can be adjusted by ordinary paper making technology 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 is obtained by impregnating or coating at least one side of a solution containing cellulose nanofibers and a hygroscopic agent on the base paper.

(2) Cellulose Nanofibers Cellulose nanofibers are fine fibers obtained by subjecting a cellulose raw material to chemical modification treatment as necessary, followed by defibration treatment. The average fiber diameter of cellulose nanofibers is usually about 3 nm or more and 500 nm or less. Average fiber diameter and average fiber length can be obtained by averaging the fiber diameter and fiber length obtained from the result 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 equation.
Average aspect ratio = average fiber length / average fiber diameter

(2-1) Cellulose raw material Although the origin of the cellulose raw material which is a raw material of cellulose nanofiber is not specifically limited, For example, plant (For example, wood, bamboo, hemp, jute, kenaf, farmland waste, cloth, pulp (conifer) 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) And thermomechanical pulp (TMP), regenerated pulp, used paper, etc.), animals (eg, ascidians), algae, microorganisms (eg, acetic acid bacteria (acetobacter)), etc. The cellulose raw materials used in the present invention are Either one or a combination of two or more may be used. Preferably, it is a cellulose raw material (for example, cellulose fiber) derived from a plant or microorganism, and more preferably a cellulose raw material (for example, cellulose fiber) derived from a plant.
The number average fiber diameter of the cellulose raw material is not particularly limited, but is about 30 μm to 60 μm in the case of softwood kraft pulp which is a general pulp, and about 10 μm to 30 μm in the case of hardwood kraft pulp. In the case of other pulps, those after general refining are about 50 μm. For example, in the case where a chip or the like having a size of several centimeters is purified, it is preferable to perform mechanical processing with a disintegrator such as a refiner or beater to adjust to about 50 μm.

(2-2) Modified Cellulose raw material has three hydroxyl groups per glucose unit, and can be subjected to various types of chemical modification treatment. In the present invention, these may or may not be modified. However, if chemical modification treatment is carried out, the fineness of the fiber will be sufficiently advanced and uniform fiber length and diameter can be obtained. Be
The modification method for modifying the cellulose raw material is not particularly limited, but, for example, chemical modification such as oxidation (carboxylation), etherification (carboxymethylation), cationization, esterification, phosphorylation, silane coupling, fluorination, etc. Can be mentioned. Among them, oxidation (carboxylation), etherification (carboxymethylation), cationization and esterification are preferable, and in the following, these detailed methods will be described.

(2-2-1) Oxidized (Carboxylated) Cellulose Nanofiber In the case of modifying a cellulose raw material by oxidation, the amount of carboxyl group relative to the dry weight of the obtained oxidized cellulose or cellulose nanofiber is preferably 0.5 mmol / g Or more, more preferably 0.8 mmol / g or more, further 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, and still more preferably 2.0 mmol / g or less. Therefore, 0.5 mmol / g or more and 3.0 mmol / g or less are preferable, 0.8 mmol / g or more and 2.5 mmol / g or less are more preferable, and 1.0 mmol / g or more and 2.0 mmol / g or less are more 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 The method of oxidizing a raw material is mentioned. According to this method, the primary hydroxyl group at the C6 position of the glucopyranose ring of the cellulose surface is selectively oxidized to form 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 at the time of reaction is not particularly limited, but is preferably 5% by weight or less.

The N-oxyl compound refers to a compound capable of generating a nitroxy radical. Examples of the nitroxy radical 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 target 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 the cellulose serving as the raw material. For example, 0.01 mmol or more is preferable with respect to 1 g of absolutely dried cellulose, and 0.02 mmol or more is more preferable. The upper limit is preferably 10 mmol or less, more preferably 1 mmol or less, and still more preferably 0.5 mmol or less. Accordingly, 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 still more preferably 0.02 mmol or more and 0.5 mmol or less, with respect to 1 g of absolutely dried cellulose.

  The bromide is a compound containing bromine, and examples thereof include alkali metal bromides which can be dissociated and ionized in water, such as sodium bromide and the like. In addition, iodide is a compound containing iodine, and examples thereof include alkali metal iodides. The amount of bromide or iodide used may be selected within the range capable of promoting the oxidation reaction. The total amount of bromide and iodide is preferably 0.1 mmol or more, more preferably 0.5 mmol or more, to 1 g of cellulose which is absolutely dry. The upper limit is preferably 100 mmol or less, more preferably 10 mmol or less, and still more preferably 5 mmol or less. Accordingly, the total amount of the bromide and the iodide is preferably 0.1 mmol to 100 mmol, more preferably 0.1 mmol to 10 mmol, and still more preferably 0.5 mmol to 5 mmol with respect to 1 g of cellulose which is extremely dry.

  The oxidizing agent is not particularly limited, and examples thereof include halogens, hypohalous acids, subhalic acids, perhalogen acids, salts thereof, halogen oxides, peroxides and the like. Among them, hypohalous acid or a salt thereof is preferable, hypochlorous acid or a salt thereof is more preferable, and sodium hypochlorite is further preferable, because the cost and environmental load are small. The amount of the oxidizing agent used is preferably 0.5 mmol or more, more preferably 1 mmol or more, and still more preferably 3 mmol or more, with respect to 1 g of absolutely dried cellulose. The upper limit is preferably 500 mmol or less, more preferably 50 mmol or less, still 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 to 500 mmol, more preferably 0.5 mmol to 50 mmol, still more preferably 1 mmol to 25 mmol, and most preferably 3 mmol to 10 mmol per 1 g of cellulose. preferable. When an N-oxyl compound is used, 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. Accordingly, 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.

  The conditions such as pH and temperature at the time of 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 more, more preferably 15 ° C. or more. The upper limit is preferably 40 ° C. or less, more preferably 30 ° C. or less. Accordingly, the temperature is preferably 4 ° C. or more and 40 ° C. or less, and may be 15 ° C. or more and 30 ° C. or less, 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, more preferably 10 or more and 11 or less. Generally, the pH of the reaction solution tends to decrease because carboxyl groups are formed in cellulose as the oxidation reaction proceeds. Therefore, in order to allow the oxidation reaction to proceed efficiently, it is preferable to add an alkaline solution such as an aqueous solution of sodium hydroxide to maintain the pH of the reaction solution in the above range. The reaction medium for oxidation is preferably water because of the ease of handling and the fact that side reactions are less likely to occur.

The reaction time in the oxidation can be appropriately set according to the degree of progress of the 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 the oxidation is usually 0.5 hours to 6 hours, for example, 0.5 hours to 4 hours.
The oxidation may be carried out in two or more stages of reaction. For example, by oxidizing oxidized cellulose obtained by filtration after completion of the first step reaction again under the same or different reaction conditions, the efficiency of the reaction can be increased without the reaction inhibition by sodium chloride by-produced in the first step reaction. It can be oxidized well.

Another example of the carboxylation (oxidation) method is a method of oxidation by ozone treatment. This oxidation reaction oxidizes at least the 2- and 6-position hydroxyl groups of the glucopyranose ring constituting the cellulose and causes the decomposition of the cellulose chain. The ozone treatment is usually performed by contacting a gas containing ozone 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, 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 to 30% by weight, and more preferably 5% by weight to 30% by weight, based on 100% by weight of the solid content of the cellulose raw material. The ozone treatment temperature is usually 0 ° C. or more, preferably 20 ° C. or more. The upper limit is usually 50 ° C. or less. Therefore, the ozone treatment temperature is usually 0 ° C. or more and 50 ° C. or less, and preferably 20 ° C. or more and 50 ° C. or less. 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 conditions of the ozone treatment are within the above-mentioned range, excessive oxidation and decomposition of cellulose can be prevented, and the yield of oxidized cellulose becomes good.

  The resulting product obtained after the ozone treatment may be further subjected to an additional oxidation treatment using an oxidizing agent. The oxidizing agent used for the additional oxidation treatment is not particularly limited, and examples thereof include chlorine based compounds such as chlorine dioxide and sodium chlorite; oxygen, hydrogen peroxide, persulfuric acid, peracetic acid and the like. 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, the carboxylate group and the aldehyde group contained in the oxidized cellulose nanofibers can be adjusted by controlling the oxidation conditions such as the addition amount of the oxidizing agent and the reaction time.
An example of the method of measuring the amount of carboxyl groups is described below. After preparing 60 ml of 0.5 wt% slurry (water dispersion liquid) of oxidized cellulose and adding 0.1 M hydrochloric acid aqueous solution to adjust to pH 2.5, 0.05 N aqueous sodium hydroxide solution is dropped to adjust pH 11 Measure the conductivity until From the amount of sodium hydroxide (a [ml]) consumed in the step of neutralization of a weak acid in which the change in electrical conductivity is gradual, the amount of carboxyl groups can be calculated using the following formula:
Carboxyl group [mmol / g oxidized cellulose or cellulose nanofiber] = a [ml] x 0.05 / oxidized cellulose weight [g]

(2-2-2) Etherified (Carboxymethylated) Cellulose Nanofiber As etherification, carboxymethylated (ether), methyl (etherified), ethyl (etherified), cyanoethyl (etherified), hydroxyethyl (ether) And ether), hydroxypropyl (ether), ethyl hydroxyethyl (ether), hydroxypropyl methyl (ether) and the like. The method of carboxymethylation is demonstrated below as an example out of this.
When modifying a cellulose raw material by carboxymethylation, the degree of carboxymethyl group substitution per anhydroglucose unit in the carboxymethylated cellulose or cellulose nanofiber obtained 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 still more preferably 0.35 or less. Accordingly, 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 still 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 bottoming raw material and then etherifying it can be mentioned. As a solvent used for a carboxymethylation reaction, water, alcohol (for example, lower alcohol), and these mixed solvents are mentioned, for example. Examples of lower alcohols 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 to the cellulose raw material. Although the upper limit is not particularly limited, it is 20 times by weight. Therefore, the amount of the solvent is preferably 3 to 20 times by weight.

Mercerization is usually carried out by mixing the bottom raw material and the mercerizing agent. Examples of mercerizing agents include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. The amount of the mercerizing agent used is preferably 0.5 times mol or more, more preferably 1.0 times mol or more, and still more preferably 1.5 times mol or more per anhydroglucose residue of the base 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 times mole or more and 20 times mole or less are preferable, 1.0 times mole or more and 10 times mole or less are more preferable, and 1.5 times mole or more and 5 times mole or less are more 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 less, preferably 60 ° C. or less. Therefore, the reaction temperature is generally 0 ° C. or more and 70 ° C. or less, preferably 10 ° C. or more and 60 ° C. or less. 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, 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. Carboxymethylating agents include, for example, sodium monochloroacetate. The amount of addition of the carboxymethylating agent is preferably 0.05 or more moles, more preferably 0.5 or more moles, and even more preferably 0.8 or more moles per glucose residue of the cellulose raw material. The upper limit is usually 10.0 times mol or less, preferably 5 times mol or less, more preferably 3 times mol or less, therefore preferably 0.05 times mol to 10.0 times mol, more preferably It is 0.5 times mole to 5 times mole, and more preferably 0.8 times mole to 3 times mole. The reaction temperature is usually 30 ° C. or more, preferably 40 ° C. or more, and the upper limit is usually 90 ° C. or less, preferably 80 ° C. or less. 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 from 30 minutes to 10 hours, preferably from 1 hour to 4 hours. The reaction solution may be stirred, if necessary, during the carboxymethylation reaction.

The degree of carboxymethyl substitution per glucose unit of carboxymethyl cellulose nanofibers may be measured, for example, by the following method. Specifically, 1) Approximately 2.0 g of carboxymethylated cellulose (absolutely dry) is precisely weighed and placed in a 300 mL stoppered Erlenmeyer flask. 2) 100 mL of a solution obtained by adding 100 mL of special grade concentrated nitric acid to 1000 mL of nitric acid methanol is added, and shaken 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 dry), and place in a 300 mL stoppered Erlenmeyer flask. 4) Wet the hydrogenated 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) Back titrate excess NaOH with 0.1 N H ₂ SO ₄ using phenolphthalein as indicator. 6) Calculate the carboxymethyl substitution degree (DS) by the following formula:
A = [(100 × F ' - (H 2 SO 4 in 0.1N) (mL) × F) × 0.
1] / (absolute dry mass (g) of hydrogen-type carboxymethylated cellulose)
DS = 0.162 × A / (1−0.058 × A)
A: 1 N required to neutralize 1 g of hydrogen-type carboxymethylated cellulose
Amount of NaOH (mL)
F ': factor of 0.1 N H ₂ SO ₄ F: factor of 0.1 N NaOH

(2-2-3) Cationic cellulose nanofiber When the cellulose raw material is modified by cationizing, the cationic cellulose nanofiber obtained has a cation such as ammonium, phosphonium, sulfonium or a group having the cation in the molecule. It should be included. The cationized cellulose nanofibers preferably include a group having ammonium, and more preferably include a group having quaternary ammonium.

  Although the method of cationization is not particularly limited, for example, a method of reacting a cellulose raw material with a cationizing agent and a catalyst in the presence of water and / or an alcohol can be mentioned. As the cationizing agent, for example, glycidyl trimethyl ammonium chloride, 3-chloro-2-hydroxypropyl trialkyl ammonium hydride (eg 3-chloro-2-hydroxypropyl trimethyl ammonium hydroxide) or their halohydrin type and the like can be mentioned. 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. As alcohol, a C1-C4 alcohol is mentioned, for example. 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, and more preferably 1% by weight or more based on 100% by weight of the cellulose fiber. The upper limit is usually 7% by weight or less, preferably 3% by weight or less. The amount of alcohol is preferably at least 50% by weight, more preferably at least 100% by weight, based on 100% by weight of the cellulose fiber. The upper limit is usually 50000% by weight or less, preferably 500% by weight or less.

The reaction temperature for cationization is usually 10 ° C. or more, preferably 30 ° C. or more, and the upper limit is usually 90 ° C. or less, preferably 80 ° C. or less. 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, if necessary, during the cationization reaction.
The degree of cation substitution per glucose unit of cationized cellulose can be adjusted by control of the addition amount of the cationizing agent, 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 number of moles of introduced substituent divided by the total number of moles of hydroxyl groups of the glucopyranose ring". Since pure cellulose has 3 substitutable hydroxyl groups per unit structure (glucopyranose ring), the theoretical maximum value of the degree of cation substitution is 3 (minimum value is 0).

  0.01 or more is preferable, as for the cation substitution degree per glucose unit of a cationization cellulose nanofiber, 0.02 or more is more preferable, and 0.03 or more is more preferable. The upper limit is preferably 0.40 or less, more preferably 0.30 or less, and still 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 still more preferably 0.03 or more and 0.20 or less. By introducing a cationic substituent into cellulose, the celluloses electrically repel each other. For this reason, the cellulose which introduce | transduced the cation substituent can be easily nano-fibrillated. When the degree of cation substitution per glucose unit is 0.01 or more, nano disintegration can be sufficiently achieved. 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 form can be maintained and the situation where it can not be obtained as nanofibers is prevented. be able to.

An example of the method of measuring the degree of cation substitution per glucose unit is described below. After drying the sample (cationized cellulose), the nitrogen content is measured by a total nitrogen analyzer TN-10 (manufactured by Mitsubishi Chemical Corporation), and the degree of cation substitution is calculated by the following equation. The degree of cation substitution as used herein is an average value of the 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. For example, a method of reacting the following compound A with a cellulose raw material can be mentioned. 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, and a method of adding the aqueous solution of the compound A into the slurry of the cellulose raw material. Among these, the method of mixing the aqueous solution of the compound A with the cellulose raw material or the slurry thereof is preferable because the uniformity of the reaction is enhanced and the esterification efficiency is enhanced.

  As the compound A, for example, phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid, esters thereof and the like can be mentioned. Compound A may be in the form of a salt. Among the above, phosphoric acid based compounds are preferable because they are low in cost and easy to handle, and phosphoric acid groups can be introduced into cellulose of pulp fibers to improve the disaggregation efficiency. The phosphoric acid-based compound may be any compound having a phosphoric acid group, for example, phosphoric acid, sodium dihydrogenphosphate, disodium hydrogenphosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, diphosphate Potassium hydrogen, dipotassium hydrogen phosphate, potassium triphosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, ammonium dihydrogen phosphate, ammonium triphosphate, ammonium pyrophosphate, ammonium metaphosphate and the like can be mentioned. . The phosphoric acid compound to be used may be one kind or a combination of two or more kinds. Among these, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, phosphoric acid, from the viewpoint of high efficiency of phosphate group introduction, easy disaggregation in the following fibrillation step, and industrial application. Of ammonium salts are preferable, and sodium dihydrogen phosphate and disodium hydrogen phosphate are more preferable. In addition, it is preferable to use an aqueous solution of a phosphoric acid-based compound in esterification because the uniformity of the reaction is increased and the efficiency of introducing a phosphoric acid group is increased. The pH of the aqueous solution of the phosphoric acid-based compound is preferably 7 or less, because the efficiency of the introduction of the phosphate group is high, and the pH is preferably 3 or more from the viewpoint of suppressing the hydrolysis of pulp fibers.

  Examples of the method of esterification include the following methods. Compound A is added to a suspension of a cellulose raw material (for example, solid concentration 0.1 to 10% by weight) while stirring to introduce a phosphate group to cellulose. When the compound A is a phosphoric acid compound when the amount of the cellulose raw material is 100 parts by weight, the addition amount of the compound A is preferably 0.2 parts by weight or more, more preferably 1 part by weight or more, as a phosphorus element amount. 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. This makes it possible to efficiently obtain a yield commensurate with the amount of compound A used. Therefore, 0.2 parts by weight or more and 500 parts by weight or less are preferable, and 1 parts by weight or more and 400 parts by weight or less are more preferable.

  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 to a slurry of a cellulose raw material, an aqueous solution of the compound A, or a slurry of a cellulose raw material and the compound A.

  Compound B is a nitrogen-containing compound that exhibits basicity. The term "showing 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. Among these, urea is preferable in terms of low cost and easy handling. The amount of the 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, based on 100 parts by weight of the cellulose raw material. The reaction temperature is preferably 0 ° C. or more and 95 ° C. or less, and more preferably 30 ° C. or more and 90 ° C. or less. The reaction time is not particularly limited, but is usually about 1 to 600 minutes, preferably 30 to 480 minutes. 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 phosphated cellulose. .

  After reacting the compound A with the cellulose raw material, an esterified cellulose suspension is usually obtained. It is preferable that the esterified cellulose suspension is dehydrated as required, and heat treatment is performed after dehydration. Thereby, hydrolysis of the cellulose raw material can be suppressed. The heating temperature is preferably 100 ° C. or more and 170 ° C. or less, and during the heat treatment, while water is contained, heating is performed at 130 ° C. or less (more preferably 110 ° C. or less) and 100 ° C. or more 170 after water is removed. It is more preferable to heat-treat below ° C.

  In the phosphated cellulose, a phosphoric acid group substituent is introduced into the cellulose raw material, and the celluloses electrically repel each other. Therefore, phosphated cellulose can be easily nano-fibrillated. The degree of substitution of phosphate groups per glucose unit of the phosphated cellulose is preferably 0.001 or more. Thereby, sufficient disintegration (for example, nano disintegration) can be implemented. The upper limit is preferably 0.40. Thereby, swelling or dissolution of the phosphated cellulose can be prevented, and a situation where nanofibers can not be obtained can be prevented. Therefore, it is preferable that it is 0.001 or more and 0.40 or less. The phosphated cellulose is preferably subjected to washing treatment such as boiling and washing with cold water. This enables efficient defibration.

(2-3) Pulverization Pulverization of the cellulose raw material may be performed before or after the cellulose raw material is subjected to a modification treatment. The defibration may be carried out at one time or several times. In the case of multiple times, the timing of each disintegration may be any time.
The apparatus used for disintegration is not particularly limited, and examples thereof include high-speed rotation type, colloid mill type, high pressure type, roll mill type, ultrasonic type and the like, high pressure or ultra high pressure homogenizer is preferable, and wet high pressure Or the ultrahigh pressure homogenizer is more preferable. The apparatus is preferably one capable of applying a strong shear force to the cellulose raw material or the modified cellulose (usually a dispersion). The pressure to which the device can be applied is preferably 50 MPa or more, more preferably 100 MPa or more, and still 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 the cellulose raw material or the modified cellulose (usually a dispersion) and applying a strong shear force. Thereby, disintegration can be performed efficiently.

When disintegration is performed on a dispersion of a cellulose material, the solid content concentration of the cellulose material 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 or more. As a result, the amount of liquid relative to the amount of cellulose fiber raw material becomes appropriate and efficient. The upper limit is usually 10% by weight or less, preferably 6% by weight or less. This allows the liquidity to be maintained.
Prior to disintegration (preferably disintegration with a high-pressure homogenizer) or, if necessary, dispersion treatment prior to disintegration, pretreatment may be performed as necessary. The pretreatment may be performed using a mixing, stirring, emulsification, or dispersing device such as a high-speed shear mixer.

(2-4) Cellulose Nanofiber In the present invention, although the cellulose nanofiber may be used as it is in the dispersion liquid, the solvent may be partially or completely removed by carrying out a drying treatment as necessary to obtain a wet solid. It may be used as a solid or a dry solid. Here, the wet solid is a solid in an intermediate aspect between the dispersion and the dry solid.
When the drying process is performed, the water-soluble polymer may be mixed with the dispersion of the cellulose nanofibers in advance to improve the redispersibility, and then the drying process may be performed. Examples of water-soluble polymers include cellulose derivatives (carboxymethylcellulose and salts thereof, methylcellulose, hydroxypropylcellulose, ethylcellulose), xanthan gum, xyloglucan, dextrin, dextran, carrageenan, locust bean gum, alginic acid, alginate, pullulan, starch, Potato flour, mulberry flour, positive starch, phosphorylated starch, corn starch, gum arabic, locust bean gum, gellan gum, gellan gum, polydextrose, pectin, chitin, water soluble chitin, chitosan, casein, albumin, soy protein lysate, peptone, polyvinyl Alcohol, polyacrylamide, sodium polyacrylate, polyvinyl pyrrolidone, polyvinyl acetate, polyamino acid, polylactic acid, polymalic acid, polyg Serine, latex, rosin type sizing agent, petroleum resin type sizing agent, urea resin, melamine resin, epoxy resin, polyamide resin, polyamide / polyamine resin, polyethylene imine, polyamine, plant gum, polyethylene oxide, hydrophilic crosslinked polymer, polyacrylic Acid salts, starch polyacrylic acid copolymers, tamarind gum, gellan gum, pectin, guar gum and colloidal silica and mixtures of one or more thereof. Among these, it is preferable to use carboxymethylcellulose and a salt thereof from the viewpoint of compatibility.

  The dried solids and the wet solids of cellulose nanofibers may be prepared by drying a dispersion of cellulose nanofibers or a mixture 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. As a drying apparatus, for example, a continuous tunnel drying apparatus, a band drying apparatus, a vertical drying apparatus, a vertical turbo drying apparatus, a multi-stage disc drying apparatus, a through-flow drying apparatus, a rotary drying apparatus, a flash drying apparatus, a spray dryer drying apparatus Spray dryer, cylindrical dryer, drum dryer, screw conveyor dryer, rotary dryer with heating tube, vibration transport dryer, etc. Batch box dryer, vacuum box dryer, stirring dryer, etc. Can be mentioned. These drying devices may be used alone or in combination of two or more. The dryer is preferably a drum dryer. As a result, thermal energy can be directly supplied to the material to be dried uniformly, and energy efficiency can be enhanced. Also, the material to be dried can be recovered immediately without applying heat more than necessary.

  The cellulose nanofibers used in the present invention are excellent in flowability and gas barrier properties, so that the air shielding properties can be enhanced by impregnating or coating the base paper.

The preferable coating amount of the cellulose nanofiber is 0.2 g / m ² or more and 5.0 g / m ² or less as a solid content coating amount per one side, preferably 0.5 g / m ² or more and 3.0 g / m ^{2 2} or less. When the coating amount of the cellulose nanofibers is less than 0.2 g / m ² , the improvement of the air resistance is small, and the air shielding property is insufficient. If the coating amount exceeds 5.0 g / m ² , the moisture permeability is unfavorably lowered.

(3) Hygroscopic agent The hygroscopic agent is an alkali metal salt such as lithium chloride or sodium lactate, an alkaline earth metal salt such as calcium chloride or magnesium chloride, an ammonium salt such as ammonium phosphate or ammonium sulfamate, guanidine guanidine sulfamate or the like A guanidine salt such as guanidine hydrochloride can be used, and calcium chloride which is particularly excellent in hygroscopicity and inexpensive can be suitably used. These compounds may be used alone or in combination of two or more. Among the moisture absorbents, those which 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, preferably 1.0 g / m ² or more and 15 g / m ² or less. If the coating amount of the hygroscopic agent is less than 0.5 g / m ² , the moisture permeability is insufficient. Further, if the coating amount exceeds 20 g / m ² , the moisture absorption amount is excessive, and in an environment of high temperature and high humidity, there is a risk of causing condensation and the flow of the hygroscopic agent, which is not preferable. The hygroscopic agent may be impregnated on the entire base paper, or may be coated on one side or both sides, as long as it is within the range of the coating amount.

(4) Total Heat Exchanger Element Paper In the total heat exchange element paper of the present invention, a solution containing cellulose nanofibers and a solution containing a hygroscopic agent are impregnated or coated on a base paper comprising papermaking fibers. It can be manufactured by
It is preferable to use the same drug solution as the drug solution containing cellulose nanofibers and the drug solution containing a hygroscopic agent, because the coating amount of each component can be accurately estimated. A drug solution containing cellulose nanofibers and a hygroscopic agent can be obtained by adding a hygroscopic agent to a dispersion of cellulose nanofibers. The proportion 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 based on 1 part by mass of the cellulose nanofibers Mix. If the content of the hygroscopic agent is less than 2 parts by mass, sufficient moisture permeability can not be obtained. If the proportion of the hygroscopic agent exceeds 30 parts by mass, the air resistance is insufficient, which is not preferable.

  The chemical solution of the present invention may be added with various functional aids usually used, such as water resistance agents, flame retardants, rust inhibitors, antibacterial agents, bacteriostatic agents, antiblocking agents, etc., if necessary. . Moreover, when applying a chemical | medical solution to a base paper, although it apply | coats to at least single side | surface, when apply | coating on both surfaces, the same chemical | medical solution may be sufficient as both surfaces, You may use a chemical | medical solution from which a combination and composition differ in each surface.

The total heat exchange element paper of the present invention can exhibit excellent air permeability resistance by applying cellulose nanofibers. The water-soluble polymer substance can be added in a range in which blocking does not occur, but the amount is preferably less than 2.0 g / m ² and further 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.

  A rod coater, a die coater, a curtain coater, a two-roll size press, a rod metering size press, a gate roll coater, a blade can be used as a method of applying a chemical solution containing cellulose nanofibers prepared as described above to a base paper. A method of coating by a coating machine such as a coater or a method of impregnating can be mentioned.

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

  The obtained coated paper may be subjected to a calendering treatment with a super calender, a hot pressure roll, etc., if necessary. The calendering reduces the thickness to improve the thermal conductivity in the thickness direction, and the densification increases the air resistance and the air shielding property.

  Thus, a sheet containing papermaking fibers, a hygroscopic agent, and cellulose nanofibers is obtained. The sheet has both air shielding properties and moisture permeability, and can be suitably used as a total heat exchange element sheet.

The basis weight of the total heat exchange element paper is preferably 10 g / m ^{2 to} 70 g / m ² , more preferably 15 g / m ^{2 to} 40 g / m ² , and most preferably 20 g / m ^{2 to} 35 g / m ² It is below. If the basis weight is less than 10 g / m ² , the strength is significantly reduced and the workability at the time of processing into the total heat exchange element is reduced. When the basis weight exceeds 70 g / m ² , the total heat exchange efficiency in the thickness direction is unfavorably reduced.

  The thickness of the total heat exchange element sheet is preferably 8 μm or more and 80 μm or less. Within this range, it is more preferable that the thickness is thinner since the total heat exchange efficiency tends to be higher. If the thickness is less than 8 μm, the strength is significantly reduced, and the workability at the time of processing into the total heat exchange element is reduced. If the thickness exceeds 80 μm, the total heat exchange efficiency in the thickness direction is unfavorably reduced.

  The air resistance of the total heat exchange element paper is preferably 700 seconds or more. If the air resistance is less than 700 seconds, there is no significant difference from the air resistance of the base paper, and it is meaningless to coat the cellulose nanofibers. When the air resistance of the heat exchange element paper used in the heat exchange ventilator increases, it becomes difficult to mix the air between the fresh air supply and the dirty exhaust, and in particular, the carbon dioxide gas transfer rate is lowered. The air shielding ability to separate air and exhaust air is improved. According to Patent Document 3, when the air resistance is 200 seconds or more, the carbon dioxide gas transfer rate is 5% or less, and when the air resistance is 5000 seconds or more, the carbon dioxide gas transfer rate can be suppressed to 1% or less. Patent Document 5 discloses that if the air resistance is 500 seconds or more, it can be used as a total heat exchange element sheet.

The moisture permeability of the total heat exchange element paper is preferably 800 g / m ² · 24 hr or more, more preferably 1000 g / m ² · 24 hr or more. The moisture permeability is effective as an index of the latent heat exchange efficiency of the total heat exchange element paper, the higher the moisture permeability the higher the latent heat exchange efficiency, while the latent heat required when the moisture permeability is less than 800 g / m ² · 24 hr. Exchange efficiency can not be obtained.

  The present invention will be described in more detail by way of the following examples. The definition and measurement method of each characteristic in the present invention are as follows.

[Measuring method]
(1) Basic weight A sample with a size of 250 mm × 200 mm is placed in a weighing bottle of known weight, and the weight after drying at 105 ° C. for 2 hours is measured, and the bone-dry weight per square meter of sample is calculated. Amount (g / m ² ).

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

(3) Thickness After conditioning 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 μm).

(4) Moisture Permeability Measurement was carried out using an apparatus specified in JIS Z0208 (1976) moisture permeability (cup method), changing the temperature and humidity conditions of the measurement environment. Place the test piece on the moisture-permeable cup for 24 hours in a constant temperature and humidity chamber set at 20 ° C and 65% RH to measure the increase in weight, and calculate the change in weight per 24 hours of the measurement area per square meter. The moisture permeability (g / m ² · 24 hr).

(5) Air resistance The average value of five measurements was calculated according to the Oken type test method described in JIS P8117 (2009) Air permeability and air resistance, and Research) (seconds).

[Production of base paper]
40% by mass of softwood bleached kraft pulp and 60% by mass of hardwood bleached kraft pulp are mixed and refined to a Canadian standard freeness of 250 ml CSF, and polyamidepolyamine epichlorohydrin-based wet paper strength agent (manufactured by Hoshimitsu PMC Co., Ltd.) Brand name: WS-535) is added at an absolute dry weight of 0.25% by mass to prepare a papermaking material, and after making a paper with a Fourdrinier paper machine, super calendered to a basis weight of 32 g / m ² (absolutely dry) (By weight) was obtained.

[Production of Carboxymethylated Cellulose Nanofiber]
In a stirrer capable of mixing pulp, 200 g dry weight of softwood bleached kraft pulp (manufactured by Nippon Paper Industries Co., Ltd.) and 111 g dry weight of sodium hydroxide (2.25 moles per base anhydrous glucose residue of base material) ) And water was added to make the pulp solids 20% (w / v). Then, after stirring for 30 minutes at 30 ° C., 216 g of sodium monochloroacetate (in terms of active ingredient, 1.5 mol per glucose residue of pulp) was added. After stirring for 30 minutes, the temperature was raised to 70 ° C. and stirred for 1 hour. The reaction was then withdrawn, neutralized and washed to obtain carboxymethylated pulp with a degree of carboxymethyl substitution of 0.25 per glucose unit. The solid content was adjusted to 1.2% with water and treated 5 times with a high pressure homogenizer at 20 ° C. and a pressure of 150 MPa to defibrillate and obtain carboxymethyl 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 The solution was dissolved to prepare a coating solution. The above coating solution was coated on one side of a base paper with a Mayer bar and dried to obtain a total heat exchange element paper of the present invention. The amount of adhesion, the degree of air resistance, and the moisture permeability were measured for this sheet. The results are shown in Table 1.

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

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

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

[Manufacture of carboxylated cellulose nanofibers]
Softwood bleached unbeaten kraft pulp (whiteness 85%) 5.00 g (absolutely dry), TEMPO (Sigma Aldrich) 39 mg (0.05 mmol relative to 1 gram of absolute dry cellulose) and sodium bromide 514 mg (absolutely dry) The solution was added to 500 ml of an aqueous solution of 1.0 mmol) dissolved in 1 g of cellulose and stirred until the pulp was uniformly dispersed. An aqueous solution of sodium hypochlorite was added to the reaction system so that the concentration of sodium hypochlorite was 5.5 mmol / g, and an oxidation reaction was initiated at room temperature. During the reaction, the pH in the system decreased, but 3M aqueous sodium hydroxide solution was sequentially added to adjust to pH 10. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system did not change.
The mixture after reaction was filtered through a glass filter for pulp separation, 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 and treated three times with an ultrahigh pressure homogenizer (20 ° C., 150 Mpa) to obtain an aqueous dispersion of carboxylated cellulose nanofibers (hereinafter referred to as T-CNF). I 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 (solid content concentration: 1.1% by mass) of T-CNF and dispersed with a winged stirrer The solution was dissolved to prepare a coating solution. The coating solution was coated on one side of a base paper with a Mayer bar and dried to obtain a single-sided coated paper of T-CNF and calcium chloride. On the other side of this single-sided coated paper, 45 parts by mass of water is added to 90 parts by mass of a T-CNF aqueous dispersion (solid content concentration: 1.1% by mass), and the coating liquid dispersed by a winged stirrer is 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, the degree of air resistance, and the moisture permeability were measured for this sheet. The results are shown in Table 1.

[Manufacture of cationized cellulose nanofibers]
To a pulper capable of stirring pulp, 200 g of softwood bleached kraft pulp (manufactured by Nippon Paper Industries Co., Ltd.) by dry weight and 24 g of sodium hydroxide by dry weight are added, and water is added so that the pulp solid concentration is 15%. The Then, after stirring at 30 ° C. for 30 minutes, the temperature was raised to 70 ° C., and 200 g of 3-chloro-2-hydroxypropyltrimethylammonium chloride (in terms of active ingredient) was added as a cationizing agent. After reacting for 1 hour, the reaction product was taken out, neutralized, and washed to obtain a cation-modified pulp having a degree of cation substitution of 0.05 per glucose unit. The solid concentration was adjusted to 1.2%, and the mixture was treated twice with a high pressure homogenizer at 20 ° C. and a pressure of 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 a C-CNF aqueous dispersion (solid content concentration: 1.2% by mass) and dispersed with a winged stirrer The solution was dissolved to prepare a coating solution. The coating solution was coated on one side of the base paper with a Mayer bar and dried to obtain a single-sided coated paper of C-CNF and calcium chloride. On the other side of this single-sided coated paper, 45 parts by mass of water is added to 90 parts by mass of a C-CNF aqueous dispersion (solid content concentration 1.2% by mass), and the coating liquid dispersed with a winged stirrer is Coating with a bar and drying gave a total heat exchange element paper of the present invention coated on both sides. The amount of adhesion, the degree of air resistance, and the moisture permeability were measured for this sheet. 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 The solution was dissolved to prepare a coating solution. The above coating solution was coated on one side of a base paper with a Mayer bar and dried to obtain a single side coated paper of CM-CNF and calcium chloride. On the other side of this single-sided coated paper, 30 parts by mass of water was added to 60 parts by mass of a CM-CNF aqueous dispersion (solid content concentration: 1.2% by mass), and the coating liquid was dispersed by a winged stirrer. Coating with a bar and drying gave a total heat exchange element paper of the present invention coated on both sides. The amount of adhesion, the degree of air resistance, and the moisture permeability were measured for this sheet. The results are shown in Table 1.

Example 8
30 parts by mass of water and 3.6 parts by mass of potassium acetate (manufactured by Wako Pure Chemical Industries, Ltd.) are added to 60 parts by mass of an aqueous dispersion of CM-CNF (solid content concentration: 1.2% by mass) and a stirrer with a wing The mixture was dispersed and dissolved to prepare a coating solution. The coating solution was coated on one side of the base paper with a Meyer bar and dried to obtain a total heat exchange element paper of the present invention. The amount of adhesion, the degree of air resistance, and the moisture permeability were measured for this sheet.
The results are shown in Table 1.

Example 9
30 parts by mass of water and 3.6 parts by mass of lithium chloride (manufactured by Wako Pure Chemical Industries, Ltd.) are added to 60 parts by mass of an aqueous dispersion of CM-CNF (solid content concentration: 1.2% by mass) and a stirrer with a wing The mixture was dispersed and dissolved to prepare a coating solution. The coating solution was coated on one side of the base paper with a Meyer bar and dried to obtain a total heat exchange element paper of the present invention. The amount of adhesion, the degree of air resistance, and the moisture permeability were measured for this sheet. The results are shown in Table 1.

<Blocking evaluation>
Two 50 mm × 80 mm test pieces are 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 are overlapped, and the inside of a constant temperature and humidity chamber of 20 ° C. and 75% RH. After conditioning for 15 minutes, the two test pieces were crimped through a 1-nip calendar device (manufactured by Yuri Roll Machinery Co., Ltd.) with a roll temperature of 90 ° C. and a roll linear pressure of 40 kg / cm. Remove one end of the crimped test piece in the longitudinal direction, and place one end of it in a sample grip attached to a digital force gauge (Nidec-Shimpo Co., Ltd., device name: FGP-0.5 type), The other end of the sheet was grasped by hand and pulled, and peeled about 70 mm in the longitudinal direction to read the maximum value of the peeling resistance, and the peeling resistance per 5 cm of the sample width was taken as the peeling resistance. The peeling resistance of the test piece forcedly pressure-bonded using the hot pressure roll was 50 g / 5 cm or less, and the blocking property was evaluated as extremely weak.
Also in the blocking properties of the other examples, the crimped part did not peel off and the base material was not broken.

Comparative Example 1
A total heat exchange element paper of the present invention was obtained in the same manner as in Example 1 except that no CM-CNF was blended. The amount of adhesion, the degree of air resistance, and the moisture permeability were measured for this sheet. The results are shown in Table 1. The base paper had a small thickness and high air resistance due to high density in the calendering process, but the density, thickness and air resistance were calendered due to the wetting and drying actions in the coating process. It returned to the near state before, the paper thickness was thick, and the air resistance became low.
Comparative Example 2
Total heat exchange element paper was obtained in the same manner as in Example 1 except that calcium chloride was not blended and CM-CNF adhesion amount was 0.3 g / m ² . The amount of adhesion, the degree of air resistance, and the moisture permeability were measured for this sheet. The results are shown in Table 1.
Comparative Example 3
The air resistance and the moisture permeability were measured for the base paper which was not coated. The results are shown in Table 1.

Comparative Example 4
14 parts by mass of polyvinyl alcohol (manufactured by Kuraray Co., Ltd.) in terms of solid content, lithium chloride (manufactured by Wako Pure Chemical Industries, Ltd.) 10 on one side of a flame-retardant paper (aeration resistance 4 seconds) with a basis weight of 55 g / m ² A coating solution consisting of parts by mass and 76 parts by mass of water was applied and dried to prepare a total heat exchange element sheet coated with a water-soluble polymer layer containing a hygroscopic agent on one side. The hygroscopic agent application amount of this paper was 2.5 g / m ^{2 in} terms of solid content, and the polyvinyl alcohol application amount was 3.5 g / m ² in terms of solid content. The air resistance was 23000 seconds, and the moisture permeability was 1200 g / m ² · 24 hr, and had sufficient air shielding properties and moisture permeability as a total heat exchange element paper.
The paper was subjected to a forced pressure bonding test using a hot pressure roll in the same manner as in the evaluation of the blocking property, and the peel resistance was measured. As a result, the peel resistance was extremely large at 300 g / cm or more. It was evaluated that the blocking property was very strong because the material was broken.

  As is clear from Examples 1 to 9, even when using a base paper made of a raw material that is not highly beaten, by providing a coated layer containing cellulose nanofibers, the air permeability can be reduced without lowering the moisture permeability. It can be enhanced. In addition, even in the case of double-sided coating, it is possible to maintain the moisture permeability of single-sided coating and to greatly increase the air resistance.

Claims (6)

  A total heat exchange element paper comprising a papermaking fiber, a hygroscopic agent, and cellulose nanofibers.   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 nanofibers are at least one of carboxymethylated cellulose nanofibers, carboxylated cellulose nanofibers, cationized cellulose nanofibers, and esterified cellulose nanofibers. Replacement element paper.   The total heat exchange element paper according to any one of claims 1 to 3, wherein the hygroscopic agent is any one of an alkali metal salt and an alkaline earth metal salt.   The total heat exchange element sheet according to any one of claims 1 to 4, having an air resistance of 700 seconds or more. A method for producing a total heat exchange element sheet, comprising applying a chemical solution containing a hygroscopic agent and cellulose nanofibers on at least one side of a base paper comprising papermaking fibers.