JP6648849B1 - Sheet for total heat exchanger, element for total heat exchanger, and total heat exchanger - Google Patents

Abstract

An object of the present invention is to provide a sheet for a total heat exchanger having high moisture permeability and air permeability and excellent carbon dioxide barrier properties, an element for a total heat exchanger having the sheet for a total heat exchanger, and an element for the total heat exchanger. It is an object to provide a total heat exchanger comprising: The sheet for a total heat exchanger of the present invention has a base layer and a fiber layer provided on the base layer, and the fiber layer has a fiber width of 1,000 nm or less. It contains fine cellulose fibers having a group, and has a water content of 8% by mass or more. [Selection diagram] None

Description

  The present invention relates to a sheet for a total heat exchanger, an element for a total heat exchanger, and a total heat exchanger.

2. Description of the Related Art Conventionally, as a device capable of ventilation without impairing the effects of cooling and heating, a heat exchange ventilator (heat exchanger) for exchanging heat between air supply and exhaust during ventilation has been proposed. As this heat exchanger, a plurality of partition plates (liners) are stacked via a spacer, and an air supply path for introducing outdoor air into the room and an exhaust path for discharging indoor air to the outside are defined. A total heat exchanger that performs heat exchange of latent heat (humidity) at the same time as sensible heat (temperature) is widely used.
Patent Literature 1 discloses a fine cellulose fiber nonwoven fabric layer made of fine cellulose fibers for the purpose of providing a multilayer structure having high air permeability and high moisture permeability and high suitability as a sheet for a total heat exchanger. A multilayer structure comprising at least one layer is described.

International Publication No. WO 2014/014099

  The present invention provides a sheet for a total heat exchanger having high moisture permeability and air permeability, and also excellent in carbon dioxide barrier properties, a device for a total heat exchanger having the sheet for a total heat exchanger, and a device including the element for a total heat exchanger. It is intended to provide a heat exchanger.

The present inventors, in a sheet for a total heat exchanger provided with a fiber layer containing fine cellulose fibers having a phosphite group, by setting the water content to a specific content, air permeability and moisture permeability are high, It has been found that a sheet for a total heat exchanger having excellent carbon dioxide barrier properties can be obtained.
That is, the present invention relates to the following <1> to <17>.
<1> It has a base material layer and a fiber layer provided on the base material layer, and the fiber layer contains fine cellulose fibers having a phosphite group having a fiber width of 1,000 nm or less, and contains water. A sheet for a total heat exchanger having a content of 8% by mass or more.
<2> The sheet for a total heat exchanger according to <1>, further comprising a moisture absorbent.
<3> The hygroscopic agent is at least one (preferably a metal halide) selected from a metal halide salt, a metal sulfate, a metal acetate, an amine salt, a phosphate compound, a guanidine salt, and a metal hydroxide. <2>, more preferably an alkali metal halide, an alkaline earth metal halide, and still more preferably at least one selected from the group consisting of lithium chloride and calcium chloride.
<4> The sheet for a total heat exchanger according to <2> or <3>, wherein the content of the moisture absorbent is 100 parts by mass or more based on 100 parts by mass of the fine cellulose fibers.
<5> The sheet for a total heat exchanger according to any one of <1> to <4>, wherein a contact angle of water on the surface on the fiber layer side is 50 ° or more.
<6> When the contact angle of water on one surface of the sheet for a total heat exchanger is D1 and the contact angle of water on the other surface is D2, D1 / D2 is 0.25 or more and 4 or less. <1> The sheet for a total heat exchanger according to any one of to <5>.
<7> The sheet for a total heat exchanger according to any one of <1> to <6>, wherein the fine cellulose fiber has a fiber width of 30 nm or less.
<8> The sheet for a total heat exchanger according to any one of <1> to <7>, wherein the basis weight of the fine cellulose fibers is 0.1 g / m ² or more and 3 g / m ² or less.
<9> The sheet for a total heat exchanger according to any one of <1> to <8>, having one layer of the base material and one fiber layer provided on the base material layer.
<10> The sheet for a total heat exchanger according to any one of <1> to <9>, wherein the water content is 25% by mass or less.
<11> The composition further contains a moisture absorbent, and the basis weight of the moisture absorbent is 1 g / m ² or more and 20 g / m ² or less, preferably 3 g / m ² or more and 15 g / m ² or less, more preferably 5 g / m ² or more and 12 g / m ² or more. m is ² or less, <1> the total heat exchanger sheet according to any one of 1 to <10>.
<12> The sheet for a total heat exchanger according to any one of <1> to <11>, wherein the base material layer and the fiber layer contain a moisture absorbent.
<13> Density of 0.65 g / cm ³ or more and 1.3 g / cm ³ or less (preferably 0.7 g / cm ³ or more and 1.3 g / cm ³ or less, more preferably 0.75 g / cm ³ or more and 1.0 g or less) / Cm ³ or less), the sheet for a total heat exchanger according to any one of <1> to <12>.
<14> The sheet for a total heat exchanger according to any one of <1> to <13>, wherein the sheet has a thickness of 20 μm or more and 150 μm or less (preferably 20 μm or more and 120 μm or less, more preferably 30 μm or more and 100 μm or less).
<15> The basis weight is 10 g / m ² or more and 300 g / m ² or less (preferably 10 g / m ² or more and 200 g / m ² or less, more preferably 30 g / m ² or more and 100 g / m ² or less, and still more preferably 30 g / m ² or less. a m ² or more 80 g / ^{m 2} or less), <1> the total heat exchanger sheet according to any one of 1 to <14>.
<16> An element for a total heat exchanger, comprising the sheet for a total heat exchanger according to any one of <1> to <15>.
<17> A total heat exchanger including the total heat exchanger element according to <16>.

  According to the present invention, a sheet for a total heat exchanger having high moisture permeability and air permeability, and also excellent in carbon dioxide barrier properties, an element for a total heat exchanger having the sheet for a total heat exchanger, and an element for a total heat exchanger are provided. A total heat exchanger is provided.

FIG. 1 is a graph showing the relationship between the dropping amount of NaOH and the pH for a slurry containing fine cellulose fibers having a phosphorus oxo acid group.

[Seat for total heat exchanger]
The sheet for a total heat exchanger of the present invention has a base material layer and a fiber layer provided on the base material layer, and the fiber layer has a fine particle width of 1,000 nm or less having a phosphite group. It contains cellulose fibers (hereinafter also simply referred to as fine cellulose fibers), and has a water content of 8% by mass or more.
The total heat exchanger supplies fresh outside air and performs heat exchange when exhausting dirty air in the room. At this time, from the viewpoint of improving the heat exchange efficiency, the sheet for the total heat exchanger is required to be able to move sensible heat (temperature) and also to move latent heat (humidity) by passing moisture. Can be Therefore, moisture permeability and heat conductivity are required.
In addition, high gas barrier properties (mainly, carbon dioxide barrier properties) are required so that air supply and exhaust air do not mix through the sheet for the total heat exchanger.

Patent Literature 1 describes that a multilayer structure having a high air resistance (air permeability) can be obtained by providing a fine cellulose fiber nonwoven fabric layer, but the effect of the moisture content of the multilayer structure is described. Has not been considered.
ADVANTAGE OF THE INVENTION According to this invention, the moisture content of a sheet for total heat exchangers is made into a specific range, and the sheet for total heat exchangers which has high moisture permeability and air permeability, and also is excellent in carbon dioxide barrier property is obtained. The detailed mechanism of action for obtaining the above-mentioned effects is unknown, but some are considered as follows.
That is, by providing a fiber layer containing fine cellulose fibers, high air permeability and carbon dioxide barrier properties can be obtained. However, by setting the water content of the total heat exchanger sheet to 8% by mass or more, the permeability can be improved. It is considered that the humidity was improved. This is because when the moisture content of the sheet for total heat exchanger is 8% by mass or more, the sheet for total heat exchanger becomes more hydrophilic and the moisture permeability is improved as compared with the case where the moisture content is less than 8% by mass. It is presumed to have been done.
Hereinafter, the present invention will be described in more detail.

<Base layer>
The sheet for a total heat exchanger of the present invention has a substrate layer and a fiber layer provided on the substrate layer.
The substrate constituting the substrate layer is not particularly limited, and is preferably exemplified by a substrate selected from a nonwoven fabric, a porous film, and a fabric.
The sheet for a total heat exchanger of the present invention preferably forms a fibrous layer containing fine cellulose on a substrate and further contains a moisture absorbent, as described later. At this time, the “substrate” means the substrate itself forming the substrate layer before containing the hygroscopic agent, and the “substrate layer” refers to the support of the fiber layer in the sheet for total heat exchanger. Means the entire substrate layer including the base material itself and the hygroscopic agent.
Examples of the nonwoven fabric include a nonwoven fabric composed of at least one selected from natural cellulose fibers, nylon fibers, polyester fibers, and polyolefin fibers.
Examples of the porous membrane include olefin resins such as polyethylene and polypropylene; polysulfone; fluorine-based resins such as polytetrafluoroethylene, polyvinyl fluoride and polyvinylidene fluoride; polycarbonate; nylon-based resins such as 6-nylon and 6,6-nylon. A porous film composed of an acrylic resin such as polymethyl methacrylate; a polyketone such as poly (1-oxytrimethylene); a polyether ether ketone;
Examples of the cloth include cellulosic fibers containing cellulose derivative fibers, nylon fibers, polyurethane fibers, and cloths (including cross-woven cloths) made of blended yarns of these. Examples of the cellulose fibers include plant-derived fibers, animal-derived fibers, and microorganism-derived fibers.
These can be applied alone or in combination of two or more.

Among these, the substrate is preferably a nonwoven fabric, more preferably a plant pulp fiber such as natural cellulose, from the viewpoint of obtaining a desired fiber content and a desired amount of water, and is classified as “paper”. Nonwoven fabric.
The pulp used as the raw material for the base material may be either softwood pulp or hardwood pulp, and the cooking method and the bleaching method are not particularly limited. It is preferable to use softwood bleached kraft pulp (NBKP) from the viewpoint of the strength of the base material and the carbon dioxide barrier property, and it is more preferable to use NBKP as a main raw material. In addition to wood pulp, non-wood pulp such as hemp pulp, kenaf, bamboo, straw, bagasse may be used, and recovered paper pulp such as recovered paper and waste paper may be used. Materials other than pulp fibers, such as nylon fibers, nylon fibers, and other heat-sealing fibers, may be blended as auxiliary materials.
The content of the pulp in the base material is preferably 95% by mass or more, more preferably 98% by mass or more, and 100% by mass, from the viewpoint of easy formation of a fiber layer and obtaining a desired water content. Is also good.
Examples of paper include uncoated printing paper such as high-quality paper and medium-quality paper, information paper such as copy paper, and high-pressure processed glassine paper (measured by Canadian Standard Freeness Test (CSF) specified in JIS P 8121). And a semi-glassine paper having a degree of freeness lower than that of glassine paper (the degree of beating is about 100 to 200 ml).
Among them, high quality paper or semi-glassine paper is more preferable, and semi-glassine paper is further more preferable.

  The air permeability of the substrate is not particularly limited, but is preferably 5 seconds or more, more preferably 10 seconds or more, and still more preferably 30 seconds or more, from the viewpoint of increasing the air permeability of the obtained sheet for a total heat exchanger. In addition, from the viewpoint of economy, the time is preferably 1,000 seconds or less, more preferably 500 seconds or less, and still more preferably 200 seconds or less. The air permeability is measured by the method described in the examples.

The basis weight of the substrate is not particularly limited, but is preferably 5 g / m ² or more, more preferably 10 g / m ² or more, and still more preferably, from the viewpoint of setting the basis weight of the obtained sheet for a total heat exchanger to a desired range. is 20 g / ^{m 2} or more, even more preferably 25 g / ^{m 2} or more, still more preferably 30 g / ^{m 2} or more, even more preferably at 35 g / ^{m 2} or more, and preferably 200 g / ^{m 2} or less, more preferably 150 g / ^{m 2} or less, more preferably 100 g / ^{m 2} or less, still more preferably 70 g / ^{m 2} or less. Basis weight is measured by the method described in the examples.

  The thickness of the substrate is not particularly limited, but is preferably 10 μm or more, more preferably 20 μm or more, from the viewpoint of obtaining strength as a support, and from the viewpoint of reducing the thickness of the entire heat exchanger sheet as a whole. It is preferably 150 μm or less, more preferably 120 μm or less, still more preferably 100 μm or less, still more preferably 90 μm or less, and still more preferably 65 μm or less. The thickness is measured by the method described in the examples.

The density of the substrate is not particularly limited, but is preferably 0.3 g / cm ³ or more, more preferably 0.5 g / cm ³ or more, and still more preferably, from the viewpoint of setting the density of the sheet for a total heat exchanger to a desired range. 0.6 g / cm ³ or more, more preferably 0.65 g / cm ³ or more, and preferably 1.3 g from the viewpoint of availability, economy, and suppressing the mass of the entire heat exchanger as a whole. / Cm ³ or less, more preferably 1.0 g / cm ³ or less, still more preferably 0.85 g / cm ³ or less, and still more preferably 0.80 g / cm ³ or less. The density is measured by the method described in the examples.

<Fiber layer>
The sheet for a total heat exchanger of the present invention has a fiber layer, and the fiber layer contains fine cellulose fibers having a phosphite group having a fiber width of 1,000 nm or less. The fiber width of the fine cellulose fiber can be read by, for example, an electron microscope.
The average fiber width of the fine cellulose fibers is preferably 1,000 nm or less, more preferably 400 nm or less, still more preferably 100 nm or less, and still more preferably, from the viewpoint of obtaining a sheet for a total heat exchanger having excellent air permeability and moisture permeability. Is 30 nm or less, more preferably 10 nm or less, even more preferably 8 nm or less. The average fiber width of the fine cellulose fibers is preferably at least 2 nm, more preferably at least 3 nm. By setting the average fiber width of the fine cellulose fibers to 2 nm or more, dissolution in water as cellulose molecules is suppressed, and the effect of improving the air permeability and moisture permeability by the fine cellulose fibers is easily exhibited. The fine cellulose fiber is, for example, a monofilament cellulose.

The average fiber width of the cellulose fiber is measured using an electron microscope observation as follows.
First, an aqueous suspension of cellulose fibers having a concentration of 0.05% by mass or more and 0.1% by mass or less was prepared, and this suspension was cast on a carbon film-coated grid subjected to hydrophilization treatment to prepare a TEM observation sample. I do. In the case of including a wide fiber, an SEM image of a surface cast on glass may be observed.
Next, observation with an electron microscope image is performed at a magnification of 1,000 times, 5,000 times, 10,000 times, or 50,000 times depending on the width of the fiber to be observed. However, the sample, observation conditions and magnification are adjusted so as to satisfy the following conditions.
(1) One straight line X is drawn at an arbitrary position in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y perpendicular to the straight line is drawn in the same image, and 20 or more fibers intersect the straight line Y.
With respect to the observed image satisfying the above conditions, the width of the fiber intersecting with the straight lines X and Y is visually read. In this way, at least three or more sets of observation images of the surface portions that do not overlap each other are obtained. Next, the width of the fiber intersecting the straight line X and the straight line Y is read for each image. Thereby, the fiber width of at least 20 fibers × 2 × 3 = 120 fibers is read. Then, the average value of the read fiber width is defined as the average fiber width of the cellulose fibers.

The fiber length of the fine cellulose fiber is not particularly limited, but is preferably 0.1 μm or more, and is preferably 1,000 μm or less, more preferably 800 μm or less, and still more preferably 600 μm or less. By setting the fiber length of the fine cellulose fiber within the above range, destruction of the crystal region of the fine cellulose fiber can be suppressed. Further, the slurry viscosity of the fine cellulose fibers can be set in an appropriate range, and the formation of the fiber layer becomes easy.
The fiber length of the fine cellulose fiber can be determined by, for example, image analysis using TEM, SEM, or AFM.

The fine cellulose fiber preferably has an I-type crystal structure. Here, the fact that the fine cellulose fiber has the type I crystal structure can be identified in a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418 °) monochromated with graphite. Specifically, it can be identified by having typical peaks at two positions near 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less.
The proportion of the type I crystal structure in the fine cellulose fibers is preferably 30% or more, more preferably 40% or more, and further preferably 50% or more. This is preferable because a fiber layer having excellent strength can be obtained. The crystallinity can be determined by measuring the X-ray diffraction profile and using a pattern thereof according to a conventional method (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959).
The crystallinity of the fine cellulose fiber is preferably 30% or more, more preferably 40% or more, further preferably 50% or more, and preferably 100% or less, more preferably 95% or less, and still more preferably. Is 90% or less.

  The axial ratio (fiber length / fiber width) of the fine cellulose fiber is not particularly limited, but is preferably 20 or more, more preferably 50 or more, and preferably 10,000 or less, more preferably 1,000 or less. is there. By setting the axial ratio in the above range, a slurry viscosity suitable for forming a fiber layer can be obtained.

In the present invention, the basis weight (coating amount) of the fine cellulose fibers is preferably 0.1 g / m ² or more, more preferably 0.2 g / m ² or more, from the viewpoint of obtaining high air permeability and moisture permeability. It is preferably 0.3 g / m ² or more, and preferably 20 g / m ² or less, more preferably 10 g, from the viewpoint of setting the sheet thickness as a sheet for a total heat exchanger in a desired range and from the viewpoint of economy. / M ² or less, more preferably 3 g / m ² or less, even more preferably 1 g / m ² or less.

  The fine cellulose fiber has a phosphite group or a substituent derived from a phosphite group (also simply referred to as a phosphite group). In the present invention, the phosphite group or a substituent derived from the phosphite group is, for example, a substituent represented by the following formula (1).

In the formula (1), b is a natural number, m ₁ is an arbitrary number, and b × m ₁ = 1. α ₁ is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, an unsaturated-branched hydrocarbon. Group, unsaturated-cyclic hydrocarbon group, aromatic group, or a derivative thereof. Among them, α ₁ is particularly preferably a hydrogen atom. Note that α ₁ in the formula (1) does not include a group derived from a cellulose molecular chain.

Examples of the saturated-linear hydrocarbon group represented by α ₁ in the formula (1) include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group, but are not particularly limited. Examples of the saturated-branched hydrocarbon group include an i-propyl group and a t-butyl group, but are not particularly limited. Examples of the saturated-cyclic hydrocarbon group include a cyclopentyl group and a cyclohexyl group, but are not particularly limited. Examples of the unsaturated-linear hydrocarbon group include a vinyl group and an allyl group, but are not particularly limited. Examples of the unsaturated-branched hydrocarbon group include an i-propenyl group and a 3-butenyl group, but are not particularly limited. Examples of the unsaturated-cyclic hydrocarbon group include a cyclopentenyl group and a cyclohexenyl group, but are not particularly limited. Examples of the aromatic group include a phenyl group and a naphthyl group, but are not particularly limited.

As the derivative groups in alpha _1, to the main chain or side chain of the various hydrocarbon group, a carboxy group, among the functional groups such as hydroxy group, or amino group, in a state where at least one has been added or substituted Although a functional group is mentioned, it is not particularly limited. The number of carbon atoms constituting the main chain of α ₁ is not particularly limited, but is preferably 20 or less, more preferably 10 or less. By the above range the number of carbon atoms constituting the main chain of the alpha _1, the molecular weight of the phosphorous acid group can be any suitable range, to facilitate penetration of the fiber material, the yield of fine cellulose fibers Can also be increased.

Β ₁ ^{b +} in the formula (1) is a monovalent or higher cation composed of an organic substance or an inorganic substance. Examples of the monovalent or higher cation composed of an organic substance include aliphatic ammonium and aromatic ammonium. Examples of the monovalent or higher cation composed of an inorganic substance include sodium, potassium, and ions of an alkali metal such as lithium, Examples thereof include cations of divalent metals such as calcium and magnesium, and hydrogen ions, but are not particularly limited. These can be applied alone or in combination of two or more. The monovalent or more cations consisting of organic or inorganic, hardly yellowing upon heating the fiber material containing beta _1, also sodium easily industrially utilized, or ions are preferred potassium is not particularly limited .

  The fine cellulose fiber may further have a phosphate group or a group derived from a phosphate group in addition to the phosphite group or a substituent derived from the phosphite group. The phosphate group or a group derived from the phosphate group may be, for example, a substituent represented by the following formula (2) or (3). The phosphate group or a group derived from the phosphate group may be a condensed phosphorus oxo acid group represented by the following formula (3).

In the formula (2), a and b ′ are natural numbers, and m ₂ is an arbitrary number (however, a = b ′ × m ₂ ). Of α ₂ and α ₂ ′, a is O ⁻ , and the rest are OR. Here, R is a hydrogen atom, a saturated-straight-chain hydrocarbon group, a saturated-branched-chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-straight-chain hydrocarbon group, an unsaturated-branched-chain It is a hydrocarbon group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or a derivative group thereof. Note that α ₂ in the formula (2) may be a group derived from a cellulose molecular chain.

In the formula (3), a and b ″ are natural numbers, m ₃ is an arbitrary number, and n is a natural number of 2 or more (where a = b ″ × m ₃ ). ^{_{α 3 1, α 3 2,}} ···, a number of the alpha ₃ ⁿ and alpha ₃ 'is O ^- a and the remainder is either R or OR. Here, R is a hydrogen atom, a saturated-straight-chain hydrocarbon group, a saturated-branched-chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-straight-chain hydrocarbon group, an unsaturated-branched-chain It is a hydrocarbon group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or a derivative group thereof. Note that α ₃ in the formula (3) may be a group derived from a cellulose molecular chain.

Specific examples of each group in Formulas (2) and (3) are the same as the specific examples of each group in Formula (1). Further, specific ^{examples' +} a ^'beta ₃ ^b in ⁺ and Equation ^(3)' Equation (2) beta ₂ ^b in are the same as specific examples of beta ₁ ^{b +} in formula (1).

The fact that the fine cellulose fiber has a phosphite group as a substituent means that an infrared absorption spectrum of a dispersion containing the fine cellulose fiber is measured, and a phosphonite that is a tautomer of a phosphite group is detected at around 1210 cm ^−1. It can be confirmed by observing the absorption based on P = O of the acid group. In addition, the fact that the fine cellulose fiber has a phosphate group as a substituent means that an infrared absorption spectrum of a dispersion containing the fine cellulose fiber is measured, and the absorption based on P = O of the phosphate group near 1230 cm ^{−1 is} measured. It can be confirmed by observation. Further, the fact that the fine cellulose fiber has a phosphite group or a phosphate group as a substituent can also be confirmed by a method of confirming a chemical shift using NMR or a method of combining titration with elemental analysis.

  The amount of the phosphite group introduced into the fine cellulose fiber is preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, further preferably 0.50 mmol / g or more per 1 g (mass) of the fine cellulose fiber. And still more preferably 1.00 mmol / g or more. Further, the amount of the phosphite group introduced into the fine cellulose fiber is preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less, and still more preferably 3.50 mmol / g per 1 g (mass) of the fine cellulose fiber. g, more preferably 3.00 mmol / g or less. By setting the amount of the phosphite group to be in the above range, the fiber raw material can be easily made finer, and the stability of the fine cellulose fiber can be increased. By setting the amount of the phosphite group to be in the above range, the fibrillation becomes easier.

  The amount of phosphite groups introduced into the fine cellulose fibers can be measured, for example, by a neutralization titration method. In the measurement by the neutralization titration method, the amount of introduction is measured by obtaining a change in pH while adding an alkali such as an aqueous solution of sodium hydroxide to the obtained slurry containing the fine cellulose fibers.

  The amount of phosphorus oxoacid groups (including phosphite groups) introduced into the fine cellulose fibers can be measured, for example, by a neutralization titration method. In the measurement by the neutralization titration method, the amount of introduction is measured by obtaining a change in pH while adding an alkali such as an aqueous sodium hydroxide solution to the obtained slurry containing fine cellulose fibers.

FIG. 1 is a graph showing the relationship between the dropping amount of NaOH and the pH of a slurry containing fine cellulose fibers having a phosphorus oxo acid group. The amount of the phosphorus oxo acid group introduced into the fine cellulose fiber is measured, for example, as follows.
First, a slurry containing fine cellulose fibers is treated with a strongly acidic ion exchange resin. If necessary, before the treatment with the strongly acidic ion exchange resin, a fibrillation treatment similar to the fibrillation treatment step described later may be performed on the measurement target.
Then, a change in pH is observed while adding an aqueous sodium hydroxide solution, and a titration curve as shown in the upper part of FIG. 1 is obtained. In the titration curve shown in the upper part of FIG. 1, the measured pH is plotted against the amount of alkali added, and in the titration curve shown in the lower part of FIG. The increment (differential value) (1 / mmol) is plotted. In the neutralization titration, two points at which the increment (differential value of pH with respect to the amount of alkali added) is maximized are found in a curve in which the measured pH is plotted against the amount of alkali added. Among these, the maximum point of the increment obtained first by adding the alkali is called a first end point, and the maximum point of the increment obtained next is called a second end point. The amount of alkali required from the start of the titration to the first end point is equal to the amount of the first dissociated acid of the fine cellulose fibers contained in the slurry used for the titration, and the alkali required from the first end point to the second end point. The amount is equal to the amount of the second dissociated acid of the fine cellulose fibers contained in the slurry used for the titration, and the amount of alkali required from the start of the titration to the second end point is the fine cellulose fibers contained in the slurry used for the titration Of the total dissociated acid. Then, the value obtained by dividing the amount of alkali required from the start of titration to the first end point by the solid content (g) in the slurry to be titrated is the amount of introduced phosphorus oxo acid groups (mmol / g). In addition, when simply saying the amount of introduced phosphorus oxo acid groups (or the amount of phosphorus oxo acid groups), it indicates the first dissociated acid amount.
In FIG. 1, the area from the start of titration to the first end point is called a first area, and the area from the first end point to the second end point is called a second area. For example, when the phosphorus oxo acid group is a phosphoric acid group and the phosphoric acid group causes condensation, the amount of the weakly acidic group in the phosphorus oxo acid group (also referred to as the amount of the second dissociated acid in the present specification) is apparently reduced. Thus, the amount of alkali required for the second region is smaller than the amount of alkali required for the first region. On the other hand, the amount of the strongly acidic group in the phosphorus oxo acid group (also referred to as the first amount of dissociated acid in the present specification) matches the amount of the phosphorus atom regardless of the presence or absence of condensation. Further, when the phosphorus oxo acid group is a phosphite group, since the weakly acidic group does not exist in the phosphorus oxo acid group, the amount of alkali required for the second region is reduced or the amount of alkali required for the second region is reduced. May be zero. In this case, the titration curve has only one point where the increment of the pH becomes maximum.

The amount of introduced phosphorus oxo acid groups (mmol / g) is defined as “amount of phosphorus oxo acid groups in acid type cellulose fibers” (hereinafter, “g” in the denominator is the mass of acid type fine cellulose fibers). (Referred to as the amount of phosphorus oxo acid group (acid type)). Here, when the proton of the phosphorus oxo acid group is substituted by an arbitrary cation C so as to have a charge equivalent, the denominator “g” is set to the mass of the cellulose fiber when the cation C is a counter ion. By performing the conversion, “the amount of phosphorus oxo acid groups of the cellulose fiber having the cation C as a counter ion” (hereinafter, the amount of phosphorus oxo acid groups (C type)) can be obtained.
That is, it is calculated by the following formula.
Amount of oxophosphate group (C type) = Amount of phosphorus oxo acid group (acid type) / {1+ (W-1) × A / 1000}
Here, A [mmol / g]: the total amount of anions derived from the phosphorus oxo acid group of the cellulose fiber (the total amount of dissociated acid obtained by adding the amount of the strongly acidic group and the amount of the weakly acidic group of the phosphorus oxo acid group)
W: Formula weight per cation C (for example, Na is 23 and Al is 9).

  In addition, in the measurement of the amount of phosphorus oxo acid groups by the titration method, when the amount of one drop of the aqueous sodium hydroxide solution is too large, or when the titration interval is too short, an accurate value such as a lower amount of phosphorus oxo acid groups than originally expected is obtained. May not be obtained. As an appropriate drop amount and a titration interval, for example, it is desirable to titrate 10 to 50 μL of a 0.1N sodium hydroxide aqueous solution every 5 to 30 seconds. Further, in order to eliminate the influence of carbon dioxide dissolved in the fine cellulose fiber-containing slurry, for example, it is desirable to perform measurement while blowing an inert gas such as nitrogen gas into the slurry from 15 minutes before the start of titration to the end of titration. .

  In addition, in addition to the phosphite group, a phosphoric acid group, which one or both of the condensed phosphoric acid group is detected phosphorus oxoacid is derived from phosphorous acid, phosphoric acid, condensed phosphoric acid Examples of the method of distinction include, for example, a method of performing the above-described titration operation after performing a process of cutting a condensation structure such as acid hydrolysis, and a process of converting a phosphite group to a phosphate group such as an oxidation process. And then performing the above-mentioned titration operation.

[Method for producing fine cellulose fiber]
In order to obtain the above-mentioned fine cellulose fibers having a phosphite group introduced therein, a phosphite group introduction step of introducing a phosphite group into a fiber raw material, a washing step, an alkali treatment step (neutralization step), It is preferable to have a textile processing step in this order.
A pretreatment step may be provided before the phosphite group introduction step. Further, an acid treatment step may be provided instead of or in addition to the washing step.
Hereinafter, the fiber raw material and each step will be described.

<Raw material containing cellulose>
The fine cellulose fiber is manufactured from a fiber material containing cellulose (hereinafter, also simply referred to as “fiber material”).
The fiber material containing cellulose is not particularly limited, but pulp is preferably used because it is easily available and inexpensive. Pulp includes, for example, wood pulp, non-wood pulp, and deinked pulp. The wood pulp is not particularly limited. For example, hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP) ) And chemical pulp such as oxygen bleached kraft pulp (OKP), semi-chemical pulp such as semi-chemical pulp (SCP) and chemical ground wood pulp (CGP), groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP). And mechanical pulp. Non-wood pulp includes, but is not limited to, cotton pulp such as cotton linter and cotton lint, and non-wood pulp such as hemp, straw and bagasse. Examples of the deinked pulp include, but are not particularly limited to, deinked pulp made from waste paper. As the pulp of this embodiment, one of the above-mentioned types may be used alone, or two or more types may be used in combination.
Among the above pulp, for example, wood pulp and deinked pulp are preferable from the viewpoint of availability. In addition, among the wood pulp, from the viewpoint that the cellulose ratio is large and the yield of fine cellulose fibers at the time of defibration is high, and from the viewpoint that cellulose in the pulp is decomposed and long cellulose fibers having a large axial ratio are obtained. For example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are still more preferable. In addition, when a fine cellulose fiber of a long fiber having a large axial ratio is used, the viscosity tends to increase.

As the fiber raw material containing cellulose, for example, cellulose contained in ascidians or bacterial cellulose produced by acetic acid bacteria can be used.
In addition, instead of a fiber material containing cellulose, a fiber formed by a linear nitrogen-containing polysaccharide polymer such as chitin or chitosan can be used as a part thereof.

<Phosphite group introduction step>
The step of introducing a phosphite group into the cellulose fiber (phosphite group introduction step) will be described below.
In the phosphite group introduction step, at least one compound selected from compounds capable of introducing a phosphite group by reacting with a hydroxyl group of a fiber material containing cellulose (hereinafter, also referred to as “compound A”) is converted into cellulose. This is a step of acting on a fiber raw material containing.
In the phosphite group introduction step, the reaction between the fiber material containing cellulose and the compound A may be performed in the presence of at least one selected from urea and its derivatives (hereinafter, also referred to as “compound B”). . On the other hand, the reaction between the fiber material containing cellulose and the compound A may be performed in a state where the compound B is not present.

  As an example of a method of causing the compound A to act on the fiber material in the presence of the compound B, a method of mixing the compound A and the compound B with the fiber material in a dry state, a wet state, or a slurry state can be mentioned. Among them, it is preferable to use a fiber material in a dry state or a wet state, and particularly to use a fiber material in a dry state, because of high uniformity of the reaction. The form of the fiber raw material is not particularly limited, but is preferably, for example, cotton or a thin sheet. Examples of the method for adding the compound A and the compound B include a method of adding the compound A and the compound B to a fiber raw material in the form of a powder, a solution dissolved in a solvent, or a state of being heated to a melting point or higher and melted. Among these, it is preferable to add in the form of a solution dissolved in a solvent, particularly in the form of an aqueous solution, because of high reaction uniformity. Further, the compound A and the compound B may be added simultaneously to the fiber raw material, may be added separately, or may be added as a mixture. The method of adding the compound A and the compound B is not particularly limited, but when the compound A and the compound B are in a solution state, the fiber raw material may be immersed in the solution, absorbed and then taken out. May be added dropwise to the solution. In addition, the necessary amount of compound A and compound B may be added to the fiber raw material, or the excessive amount of compound A and compound B may be added to the fiber raw material, respectively, and then the excess compound A and compound B may be squeezed or filtered. It may be removed.

  The compound A used in the present embodiment is at least one selected from a compound having a phosphite group and a salt thereof. Examples of the compound having a phosphite group include phosphorous acid, and examples of the phosphorous acid include 99% phosphorous acid (phosphonic acid). Examples of the salt of the compound having a phosphite group include a lithium salt, a sodium salt, a potassium salt, and an ammonium salt of phosphorous acid, and these can have various degrees of neutralization. Among these, from the viewpoint of the introduction efficiency of the phosphorus oxo acid group being high, the defibration efficiency being more easily improved in the defibration treatment step described later, the low cost, and the ease of industrial application, phosphorous acid, A sodium salt of phosphoric acid, a potassium salt of phosphorous acid, or an ammonium salt of phosphorous acid is preferably used.

  The amount of the compound A added to the fiber raw material is not particularly limited. When the amount of the compound A added is converted into the phosphorus atom weight, the amount of the phosphorus atom added to 100 parts by mass of the fiber raw material (absolute dry mass) is preferably 0. 0.5 parts by mass or more, more preferably 1 part by mass or more, still more preferably 2 parts by mass or more, and preferably 100 parts by mass or less, more preferably 50 parts by mass or less, and still more preferably 30 parts by mass or less. . By setting the amount of phosphorus atoms added to the fiber raw material within the above range, the yield of fine cellulose fibers can be further improved. On the other hand, by setting the amount of phosphorus atoms added to the fiber raw material to be equal to or less than the upper limit, it is possible to balance the effect of improving yield and cost.

The compound B used in this embodiment is at least one selected from urea and its derivatives as described above. Compound B includes urea, thiourea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, and 1-ethylurea, dimethylurea, diethylurea, tetramethylurea and the like. These can be applied alone or in combination of two or more.
From the viewpoint of improving the uniformity of the reaction, the compound B is preferably used as an aqueous solution. From the viewpoint of further improving the uniformity of the reaction, it is preferable to use an aqueous solution in which both the compound A and the compound B are dissolved.

  The amount of the compound B to be added to 100 parts by mass of the fiber raw material (absolute dry mass) is not particularly limited, but is preferably 1 part by mass or more, more preferably 10 parts by mass or more, even more preferably 100 parts by mass or more, and Preferably it is 500 parts by mass or less, more preferably 400 parts by mass or less, further preferably 350 parts by mass or less.

  In the reaction between the fiber material containing cellulose and the compound A, an amide or an amine may be contained in the reaction system in addition to the compound B. Examples of the amide include formamide, dimethylformamide, acetamide, dimethylacetamide and the like. Examples of the amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Among these, it is known that triethylamine particularly works as a good reaction catalyst.

In the phosphite group introduction step, it is preferable to heat-treat the fiber material after adding or mixing the compound A or the like to the fiber material. As the heat treatment temperature, it is preferable to select a temperature at which a phosphite group can be efficiently introduced while suppressing thermal decomposition and hydrolysis of the fiber. The heat treatment temperature is preferably 50 ° C. or higher, more preferably 100 ° C. or higher, further preferably 130 ° C. or higher, and preferably 300 ° C. or lower, more preferably 250 ° C. or lower, and further preferably 200 ° C. or lower. .
In addition, equipment having various heat media can be used for the heat treatment, and a stirring drying device, a rotary drying device, a disk drying device, a roll heating device, a plate heating device, a fluidized bed drying device, a flash drying device , A reduced-pressure drying device, an infrared heating device, a far-infrared heating device, a microwave heating device, and a high-frequency drying device.
In the heat treatment, for example, a method in which compound A is added to a thin sheet-like fiber material by impregnation or the like and then heated, or a method in which the fiber material and compound A are heated and dried while kneading or stirring with a kneader or the like is adopted. can do. Thereby, it becomes possible to suppress the concentration unevenness of the compound A in the fiber raw material and more uniformly introduce the phosphite group to the surface of the cellulose fiber contained in the fiber raw material. This is because when the water molecules move to the surface of the fiber material with drying, the dissolved compound A is attracted to the water molecules by the surface tension and moves to the surface of the fiber material (that is, the concentration unevenness of the compound A occurs. This is considered to be due to the fact that it can be suppressed.

  In addition, the heating device used for the heat treatment is always a device that constantly generates the water retained by the slurry and the water generated by the dehydration condensation (phosphite esterification) reaction between Compound A and the hydroxyl group contained in cellulose or the like in the fiber raw material. It is preferable that the device can be discharged out of the system. As such a heating device, for example, an air-blowing oven or the like can be mentioned. By constantly discharging the water in the device system, the hydrolysis reaction of the phosphite bond, which is the reverse reaction of the phosphite esterification, can be suppressed, and in addition, the acid hydrolysis of the sugar chain in the fiber is suppressed. You can also. For this reason, it is possible to obtain fine fibers having a desired axial ratio.

  The time of the heat treatment is preferably at least 1 second, more preferably at least 10 seconds, and preferably at most 300 minutes, more preferably at most 1,000 seconds, after water is substantially removed from the fiber raw material. , More preferably 800 seconds or less. By setting the heating temperature and the heating time in an appropriate range, the amount of the phosphite group to be introduced can be within a preferable range.

  The phosphite group introduction step may be performed at least once, but may be repeated twice or more. By performing the phosphite group introduction step two or more times, many phosphite groups can be introduced into the fiber raw material. In the present invention, as one example of a preferred embodiment, a case where the phosphite group introduction step is performed twice is exemplified.

  The amount of the phosphite group introduced per 1 g (mass) of the fine cellulose fiber is preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, still more preferably 0.50 mmol / g or more, and still more preferably. Is 1.00 mmol / g or more. Further, the amount of phosphite groups introduced per 1 g (mass) of the fine cellulose fiber is preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less, and still more preferably 3.00 mmol / g or less. . It is preferable to introduce a phosphite group into the fiber raw material such that the amount of the phosphite group introduced into the fine cellulose fiber is within the above range. By setting the amount of the phosphite group to be in the above range, the fiber material can be easily refined, and the stability of the fine cellulose fiber can be increased.

<Washing process>
In order to reduce the amount of the alkali solution used in the alkali treatment step, the phosphite group-introduced fiber may be washed with water or an organic solvent after the phosphite group introduction step and before the alkali treatment step. After the alkali treatment step and before the fibrillation treatment step, it is preferable to wash the alkali-treated phosphite group-introduced fiber with water or an organic solvent from the viewpoint of improving the handleability.
In the washing step, it is preferable to repeat the operation of filtering after dispersing the phosphite group-introduced fiber in water or an organic solvent, and to control the progress of the washing step by adjusting the electric conductivity of the filtrate to a desired range. be able to. The washing step is performed so that the electric conductivity of the filtrate is preferably 10,000 μS / cm or less, more preferably 1,000 μS / cm or less, still more preferably 300 μS / cm or less, and still more preferably 150 μS / cm. Is preferred.

<Alkali treatment step (neutralization step)>
When producing fine cellulose fibers, between the phosphite group introduction step and the defibration treatment step described below, an alkali treatment is performed on the fiber raw material to neutralize the phosphite groups. (Neutralization step). The method of the alkali treatment is not particularly limited, but includes, for example, a method of immersing the phosphite group-introduced fiber in an alkaline solution.
The alkali compound contained in the alkali solution is not particularly limited, and may be an inorganic alkali compound or an organic alkali compound. In the present invention, sodium hydroxide or potassium hydroxide is preferably used as the alkali compound because of high versatility. The solvent contained in the alkaline solution may be either water or an organic solvent. The solvent contained in the alkali solution is preferably a polar solvent containing water or a polar organic solvent exemplified by alcohol, and more preferably an aqueous solvent containing at least water. As the alkaline solution, a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution is preferable because of high versatility.

The temperature of the alkali solution in the alkali treatment step is not particularly limited, but is preferably 5 ° C. or higher, more preferably 10 ° C. or higher, and is preferably 80 ° C. or lower, more preferably 60 ° C. or lower. The immersion time of the ionic group-introduced fiber in the alkali solution in the alkali treatment step is not particularly limited, but is preferably 5 minutes or more, more preferably 10 minutes or more, and preferably 30 minutes or less, more preferably 20 minutes or less. Minutes or less.
The amount of the alkaline solution used in the alkali treatment is not particularly limited, but is preferably at least 100 parts by mass, more preferably at least 1,000 parts by mass, based on 100 parts by mass of the absolute dry mass of the phosphite group-introduced fiber. And preferably not more than 100,000 parts by mass, more preferably not more than 10,000 parts by mass.

  In order to reduce the amount of the alkali solution used in the alkali treatment step, the phosphite group-introduced fiber may be washed with water or an organic solvent after the phosphite group introduction step and before the alkali treatment step. After the alkali treatment step and before the fibrillation treatment step, it is preferable to wash the alkali-treated phosphite group-introduced fiber with water or an organic solvent from the viewpoint of improving the handleability.

In the alkali treatment, the alkali solution is gradually added to the dispersion in which the phosphite group-introduced fiber is dispersed, and the pH in the system is preferably 10 or more, more preferably 11 or more, still more preferably 12 or more, and It is preferable to add an alkaline solution so that the concentration is preferably 14 or less, more preferably 13.5 or less, and still more preferably 13 or less.
By setting the addition amount of the alkali solution in the above range, the fibrillation treatment can be more easily performed, and fine cellulose fibers having a small fiber width can be easily obtained.

<Acid treatment step>
In the production of the fine cellulose fiber, an acid treatment may be performed on the phosphite group-introduced fiber raw material between the phosphite group-introducing step and the defibration step described below. As an example of a method for producing a fine cellulose fiber, there is an embodiment in which a phosphite group introduction step, an acid treatment step, an alkali treatment step, and a defibration treatment step are performed in this order.
The method of the acid treatment is not particularly limited, and a method of immersing the fiber raw material in an acid-containing acid solution can be used. The concentration of the acidic liquid used is not particularly limited, but is preferably 10% by mass or less, more preferably 5% by mass or less. The pH of the acidic liquid used is not particularly limited, but is preferably 0 or more, more preferably 1 or more, and is preferably 4 or less, more preferably 3 or less.

Examples of the acid contained in the acidic liquid include inorganic acids, sulfonic acids, carboxylic acids, and the like.
Examples of the inorganic acid include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, phosphoric acid, and boric acid.
Examples of the sulfonic acid include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid.
Examples of the carboxylic acid include formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, tartaric acid, and the like.
Among these, it is particularly preferable to use hydrochloric acid or sulfuric acid.

The temperature of the acid solution in the acid treatment is not particularly limited, but is preferably 5 ° C. or higher, more preferably 20 ° C. or higher, and is preferably 100 ° C. or lower, more preferably 90 ° C. or lower.
The immersion time in the acid solution in the acid treatment is not particularly limited, but is preferably 5 minutes or more, more preferably 10 minutes or more, and is preferably 120 minutes or less, more preferably 60 minutes or less.
The amount of the acid solution used in the acid treatment is not particularly limited, but is preferably 100 parts by mass or more, more preferably 1,000 parts by mass or more based on 100 parts by mass of the absolute dry mass (absolute dry mass) of the fiber raw material. And preferably not more than 100,000 parts by mass, more preferably not more than 10,000 parts by mass.

<Fibrillation process>
Fine cellulose fibers are obtained by defibrating the phosphite group-introduced fiber in the defibration process.
In the defibrating process, a defibrating device can be used. The defibrating apparatus is not particularly limited, but includes a high-speed defibrating machine, a grinder (stone mill type crusher), a high-pressure homogenizer or an ultra-high-pressure homogenizer, a high-pressure collision type crusher, a ball mill, a bead mill, a disk type refiner, a conical refiner, and a twin-screw kneader. A vibrating machine, a vibration mill, a homomixer under high-speed rotation, an ultrasonic disperser, a beater, or the like can be used, and the solid content concentration of the fine cellulose fibers at the time of the defibration treatment can be appropriately set. Among the above defibration apparatuses, it is more preferable to use a high-speed defibrator, a high-pressure homogenizer, or an ultra-high-pressure homogenizer that is less affected by the pulverized media and less likely to cause contamination.

In the defibration treatment step, the phosphite group-introduced fiber is preferably diluted with a dispersion medium to form a slurry. As the dispersion medium, one or more selected from water and an organic solvent such as a polar organic solvent can be used.
Although it does not specifically limit as a polar organic solvent, Alcohols, polyhydric alcohols, ketones, ethers, esters, aprotic polar solvents, etc. are preferably exemplified.
Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, isobutyl alcohol and the like. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, glycerin and the like. Examples of ketones include acetone and methyl ethyl ketone (MEK). Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, and propylene glycol monomethyl ether. Examples of the esters include ethyl acetate and butyl acetate. Examples of the aprotic polar solvent include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), and N-methyl-2-pyrrolidinone (NMP).

  The solid content concentration of the fine cellulose fibers during the defibration treatment can be set as appropriate. Further, the slurry obtained by dispersing the phosphite group-introduced fiber in the dispersion medium may contain a solid content other than the phosphite group-introduced fiber such as hydrogen-bonding urea.

<Coarse cellulose fiber>
As described above, the step of obtaining fine cellulose fibers includes a step of refining the fiber raw material (coarse cellulose fibers). At this time, most of the coarse cellulose fibers are refined, but a part thereof may remain without being refined. In such a case, the fiber layer contains coarse cellulose fibers.
In the present invention, the coarse cellulose fibers contained in the cellulose fiber-containing composition are obtained by adjusting a cellulose dispersion to a solid content concentration of 0.2% by mass and cooling a high-speed centrifuge (Kokusan Co., Ltd., H-2000B). Is a cellulose fiber that precipitates when centrifuged at 12,000 G for 10 minutes.
The low sedimentation component means that the yield of the supernatant liquid after centrifugation is high. The supernatant yield after this centrifugation is preferably 80% by mass or more based on the total mass of the cellulose fibers. The supernatant yield after centrifugation is more preferably 90% by mass or more, further preferably 95% by mass or more, and particularly preferably 99% by mass or more. The supernatant yield after centrifugation of the above fine cellulose fiber dispersion can be measured in the present specification by the following method.
The supernatant yield after centrifuging the fine cellulose fiber dispersion was measured by the method described below. The supernatant yield after centrifugation is an indicator of the yield of fine cellulose fibers, and the higher the supernatant yield, the higher the yield of fine cellulose fibers.
The fine cellulose fiber dispersion is adjusted to a solid content concentration of 0.2% by mass and centrifuged at 12,000 G for 10 minutes using a cooling high-speed centrifuge (Kokusan, H-2000B). The obtained supernatant was collected and the solid content concentration of the supernatant was measured. The yield of the fine cellulose fiber is determined based on the following equation.
Yield (%) of fine cellulose fiber = solid content concentration of supernatant (%) / 0.2 × 100

<Method of forming fiber layer>
In the present invention, the method of providing the fiber layer on the substrate is not particularly limited, and may be formed by a papermaking method, or after applying fine cellulose fibers on the substrate by coating, spraying, etc., and then drying. A fibrous layer may be formed.
The concentration of the fine cellulose fiber dispersion used for papermaking or application of the fine cellulose fibers is not particularly limited, but is preferably 10% by mass or less, more preferably 5% by mass or less, further preferably from the viewpoint of suppressing an increase in viscosity. 3% by mass or less, more preferably 1.5% by mass or less, still more preferably 1% by mass or less, and preferably 0.05% by mass or more from the viewpoint of efficiently applying fine cellulose fibers to the substrate. , More preferably 0.1% by mass or more, further preferably 0.3% by mass or more, and still more preferably 0.5% by mass or more.
The concentration of the fine cellulose fiber dispersion and the amount of the fine cellulose fiber dispersion applied to the substrate may be appropriately adjusted so that the basis weight (coating amount) of the fine cellulose fibers after drying falls within the desired range described above.

<Moisture content>
The sheet for a total heat exchanger of the present invention has a water content of 8% by mass or more. If the water content is less than 8% by mass, it is difficult to obtain high moisture permeability.
The water content can be adjusted by highly controlling the manufacturing process of the sheet for the total heat exchanger. According to the present inventors, it is presumed that, for example, the type, blending amount, addition method, and the like of the fine cellulose fibers and the moisture absorbent constituting the sheet affect the water content.
The moisture content of the sheet for the total heat exchanger is preferably 9% by mass or more, more preferably 10% by mass or more, still more preferably 12% by mass or more, and still more preferably 15% by mass or more from the viewpoint of obtaining high moisture permeability. It is. In addition, from the viewpoint of preventing dew condensation and increasing the strength of the sheet for total heat exchange, the moisture content of the sheet for total heat exchanger is preferably 30% by mass or less, more preferably 25% by mass or less, and still more preferably. 20 mass% or less.
The water content (water content) of the sheet for the total heat exchanger is measured by the method described in Examples.

(Hygroscopic agent)
The sheet for a total heat exchanger of the present invention preferably contains a moisture absorbent in order to obtain a desired moisture content. The hygroscopic agent may be contained in any one of the base material layer and the fiber layer, or may be contained in both the base material layer and the fiber layer. It is preferable that both the base material layer and the fiber layer contain the same from the viewpoint of increasing the contact angle on the surface of the base material. Note that, as described later, it is preferable that the contact angle be high.
The hygroscopic agent is not particularly limited as long as it is a conventionally known hygroscopic agent, and may be appropriately selected and used. Specifically, at least one selected from a metal halide salt, a metal lactate, a metal sulfate, a metal acetate, an amine salt, a phosphate compound, a guanidine salt, and a metal hydroxide is preferable.
Examples of the metal halide salt include lithium chloride, sodium chloride, calcium chloride, magnesium chloride, aluminum chloride, and zinc chloride. Examples of the metal lactate include sodium lactate. Examples of the metal sulfate include sodium sulfate. , Calcium sulfate, magnesium sulfate, zinc sulfate and the like, and as the metal acetate, potassium acetate and the like.
Examples of the amine salt include dimethylamine hydrochloride and the like, examples of the phosphoric acid compound include orthophosphoric acid, and examples of the guanidine salt include guanidine hydrochloride, guanidine phosphate, and guanidine sulfamate. Further, examples of the metal hydroxide include potassium hydroxide, sodium hydroxide, magnesium hydroxide and the like.
Furthermore, a water-soluble polymer, which is a hygroscopic polymer, or a hydrophilic polymer having a hydrogel-forming ability, may be used as the hygroscopic agent.
Among these, from the viewpoint of excellent hygroscopicity and handleability, and from the viewpoint of increasing the contact angle with water, the hygroscopic agent is preferably a metal salt, more preferably a metal halide salt, and an alkali metal halide. And more preferably an alkaline earth metal halide, and even more preferably at least one selected from the group consisting of lithium chloride and calcium chloride.
The present inventors initially anticipated that adding a moisture absorbent to the sheet for the total heat exchanger would increase the hydrophilicity of the sheet for the total heat exchanger and, as a result, lower the contact angle of water. However, when the moisture absorbent is a metal salt and the fine cellulose fibers have a phosphite group, the contact angle of water on the surface of the fiber layer increases as an unexpected effect. Although the detailed reason is unknown, a quasi-crosslinked structure is formed by the phosphite group contained in the fine cellulose fiber and the metal atom of the hygroscopic agent, and as a result, the surface becomes hydrophobic and water It is considered that the contact angle with respect to increases.
From the above viewpoint, an embodiment in which the fine cellulose fibers have a phosphite group and the moisture absorbent contains lithium chloride or calcium chloride is particularly preferable.

The content of the moisture absorbent in the sheet for total heat exchanger is preferably 100 parts by mass or more, more preferably 100 parts by mass or more, with respect to 100 parts by mass of fine cellulose fibers, from the viewpoint of setting the moisture content of the sheet for total heat exchanger to a desired range. Is 300 parts by mass or more, still more preferably 500 parts by mass or more, still more preferably 600 parts by mass or more, and preferably 10,000 parts by mass or less, more preferably 5,000 parts by mass or less, and further preferably 2 parts by mass or less. , 500 parts by mass or less.
The basis weight (coating amount) of the moisture absorbent in the sheet for total heat exchanger is preferably 1 g / m ² or more, more preferably 3 g / m ² or more, from the viewpoint of setting the moisture content of the sheet for total heat exchanger to a desired range. And more preferably 5 g / m ² or more, and preferably 20 g / m ² or less, more preferably 15 g / m ² or less, and still more preferably 12 g / m ² or less.

The method of causing the sheet for a total heat exchanger to contain a moisture absorbent is not particularly limited, but from the viewpoint of increasing the contact angle of water on the surface of the fiber layer, it is preferable to contain the moisture absorbent after the formation of the fiber layer. A method of spraying and applying an aqueous solution in which a moisture absorbent is dissolved after forming the layer, and a method of dipping in an aqueous solution in which the moisture absorbent is dissolved are preferably exemplified.
According to this method, the contact angle of water on the surface on the fiber layer side can be further improved as compared with the method of forming the fiber layer after applying the moisture absorbent to the base material layer in advance. Moreover, aggregation of the fine cellulose fibers in the dispersion liquid can be more effectively suppressed as compared with a method in which a moisture absorbent is added to the fine cellulose fiber dispersion liquid and applied to the substrate.

[Seat for total heat exchanger]
Hereinafter, preferred embodiments of the sheet for a total heat exchanger of the present invention will be described.
The sheet for a total heat exchanger of the present invention is not particularly limited as long as it has at least one base layer and at least one fiber layer. It may have a three-layer structure of a material layer / fiber layer, or may have a two-layer structure of a fiber layer / base layer having a fiber layer on one surface, and is not particularly limited.
Among them, a two-layer structure of a fiber layer and a base material layer is preferred from the viewpoints of ease of production and sufficient moisture permeability and air permeability and a carbon dioxide barrier property with a single fiber layer.

The density of the sheet for a total heat exchanger of the present invention is preferably 0.65 g / cm ³ or more, more preferably 0.7 g / cm ³ or more, and still more preferably 0.75 g / cm ³ , from the viewpoint of improving heat conductivity. That is all. The upper limit of the density is not particularly limited, but is preferably 1.3 g / cm ³ or less, more preferably 1.0 g / cm ³ or less, from the viewpoint of suppressing the mass of the entire heat exchanger.
The density of the sheet for the total heat exchanger is measured by the method described in the examples.

The thickness of the sheet for total heat exchanger of the present invention is preferably thinner from the viewpoint that many sheets can be arranged in the total heat exchanger, specifically, preferably 150 μm or less, more preferably 120 μm or less, furthermore Preferably it is 100 μm or less.
In addition, from the viewpoint of maintaining the strength required for a sheet for a total heat exchanger, the thickness is preferably 20 μm or more, more preferably 30 μm or more.

The basis weight of the sheet for a total heat exchanger of the present invention is preferably 10 g / m ² or more, more preferably 30 g / m ² or more, and preferably 300 g / m ² from the viewpoint of obtaining a desired density and thickness. Or less, more preferably 200 g / m ² or less, still more preferably 100 g / m ² or less, and still more preferably 80 g / m ² or less.

When the sheet for a total heat exchanger of the present invention has a fiber layer on at least one outer surface, the contact angle of water on the surface on the fiber layer side is preferably 50 ° or more. When the contact angle of water is 50 ° or more, when the spacer and the liner are bonded and assembled as a total heat exchanger element, the spread of the adhesive is suppressed, and the effective area of the total heat exchanger sheet (liner) is reduced. The decrease is suppressed, and high moisture permeability and air permeability are maintained even after processing into a total heat exchanger element.
The contact angle of water on the surface on the fiber layer side is more preferably 55 ° or more, and further preferably 60 ° or more.
The upper limit of the contact angle is not particularly limited, but is preferably 150 ° or less, more preferably 130 ° or less, and further preferably 110 ° or less, from the viewpoint of applicability of the adhesive.
The contact angle means a contact angle with water 0.1 second after dropping, and is measured by the method described in Examples.

When a fiber layer containing fine cellulose fibers is provided, the contact angle of water on the surface on the fiber layer side is generally less than 50 ° unless a metal-containing compound such as a hygroscopic agent is contained. This is probably because the contact angle of water decreases due to the capillary action of the fine cellulose fibers.
In order to set the contact angle of water on the surface of the fiber layer to the above range, the fine cellulose fiber has a phosphite group as described above, and the fiber layer has a crosslinked structure with the phosphite group. It is preferable to contain a hygroscopic agent having a metal atom capable of forming (including a pseudo-crosslinked structure).
Thereby, a crosslinked structure (including a pseudo crosslinked structure) is formed, and as a result, the surface becomes hydrophobic, and it is presumed that the contact angle is improved.

When the contact angle of water on one surface of the sheet for a total heat exchanger is D1 and the contact angle of water on the other surface is D2, the ratio D1 / D2 is preferably 0.25 or more. Or less, more preferably 0.3 or more and 3 or less, still more preferably 0.5 or more and 2 or less.
When D1 / D2 is within the above range, the difference in contact angle between water on one surface and the other surface is small, and it is easy to assemble the element for a total heat exchanger.
When the total heat exchange sheet uses paper as the base material and has a two-layer structure of the base material layer and the fiber layer, the contact angle of the surface on the fiber layer side is generally small, and Surface has large contact angle.

The air permeability of the sheet for a total heat exchanger of the present invention is preferably high from the viewpoint of separating air supply and exhaust, preferably 500 sec or more, more preferably 1,000 sec or more, and still more preferably 3,000 sec or more. , More preferably 10,000 sec or more, even more preferably 25,000 sec or more.
The air permeability is measured by the method described in the examples.

The moisture permeability of the sheet for a total heat exchanger of the present invention is preferably high from the viewpoint of promoting the transfer of latent heat and improving heat transfer, preferably 2,800 g / (m ² · 24 hr) or more, more preferably. 3,000g ^/ (m 2 · 24hr) or more, still more preferably 3,500g ^/ (m 2 · 24hr) or more.
The moisture permeability is measured by the method described in the examples.

The sheet for a total heat exchanger of the present invention preferably has a high carbon dioxide barrier property (CO ₂ barrier property) from the viewpoint of suppressing carbon dioxide in the exhaust gas from being mixed into the air supply, and is described in Examples. Is preferably 1.3% or less, more preferably 1.0% or less, still more preferably 0.8% or less, even more preferably 0.5% or less. More preferably, it is at most 0.3%.

The sheet for a total heat exchanger of the present invention may contain other components in the base material layer or the fiber layer, and specifically includes a sizing agent, a wet strength agent, a surfactant, and a flame retardant. Agents, fungicides, rust inhibitors, anti-blocking agents and the like.
The fiber layer may contain the other components described above, but the total content of the fine cellulose fibers, the hygroscopic agent, and the moisture in the fiber layer is preferably based on the total mass of the fiber layer. It is 90% by mass or more, more preferably 95% by mass or more, still more preferably 97% by mass or more, and may be 100% by mass.

Surfactants include anionic surfactants such as alkyl sulfates, polyoxyethylene alkyl sulfates, alkylbenzene sulfonates, α-olefin sulfonates, alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, benzalcoyl chloride And amphoteric surfactants such as trimethylglycine, alkyldimethylaminoacetic acid betaine and alkylamidodimethylaminoacetic acid betaine, and nonionic surfactants such as alkylpolyoxyethylene ether and fatty acid glycerol ester.
Examples of the flame retardant include halogen-based flame retardants, red phosphorus, melamine phosphate, ammonium polyphosphate, melamine polyphosphate, melamine pyrophosphate, piperazine polyphosphate, piperazine pyrophosphate, guanidine phosphate, guanidine sulfamate, (condensation) Examples include phosphorus-based flame retardants such as phosphate ester compounds and phosphazene compounds, nitrogen-based flame retardants such as melamine cyanurate, metal hydroxides such as magnesium hydroxide and aluminum hydroxide, phosphinates and diphosphinates.

Examples of the fungicide include benzimidazole compounds, pyrithione compounds, iodopropenylbutyl carbamate compounds, isothiazolone compounds, and organic nitrogen sulfur compounds.
As the rust preventive, a water-soluble rust preventive is preferable, and examples thereof include alkali metal salts of aliphatic carboxylic acids and piperazine derivatives such as monohydroxymonoethylpiperazine.
Examples of the anti-blocking agent include polyethylene wax, zinc stearate, polyethylene wax emulsion, polyethylene oxide wax, waxes selected from paraffin wax and the like, and silicone soaps and metal soaps such as calcium salts of higher fatty acids. Can be

When manufacturing the sheet for a total heat exchanger of the present invention, a post-processing as a coating treatment or a chemical treatment, and a calendering step for the purpose of adjusting the average thickness or thinning may be further provided as necessary.
In the post-processing step, for example, a step of preparing a coating liquid of a flame retardant and applying and drying the coating liquid in a step such as spray coating, a printing method, or a coating method is exemplified.
In addition, the obtained total heat exchanger sheet may be provided with a calendering step for smoothing or thinning the sheet with a calendering device, so that the average thickness can be adjusted or the density can be further improved. Examples of the calendering device include a normal calendering device using a single press roll and a super calendering device having a multi-stage structure. It is preferable to select the material (material hardness) and the linear pressure of each of these devices and both sides during calendering according to the purpose. Specifically, the material of the roll may be appropriately selected such as a combination of a metal roll and a high-hardness resin roll, a combination of a metal roll and a cotton roll, and a combination of a metal roll and an amide roll.

[Total heat exchanger element and total heat exchanger]
The element for a total heat exchanger of the present invention has the above-described sheet for a total heat exchanger of the present invention, and particularly has it as a liner of the element for a total heat exchanger.
More specifically, the total heat exchanger element is configured such that a spacer constituting a flow path is sandwiched between each sheet of a plurality of total heat exchanger sheets (liners), and the spacer and the sheet Is adhered with an adhesive or the like.
Further, a total heat exchanger of the present invention includes the element for a total heat exchanger of the present invention. An example of a preferably used total heat exchanger is a static total heat exchanger. The stationary total heat exchanger may be a cross-flow type or a counter-current type, and is not particularly limited. The stationary total heat exchanger is provided with an air supply fan and an exhaust gas, which are separated by the total heat exchanger sheet (liner) of the present invention and have a structure in which two independent flow paths are alternately stacked. Composed of fans.
The supply gas, such as the outside air, is sucked into the total heat exchanger element by the air supply fan, and comes into contact with the total heat exchanger sheet incorporated in the total heat exchanger element. On the other hand, exhaust gas such as room air is sucked into the element for total heat exchanger by the exhaust fan, and similarly comes into contact with the sheet for total heat exchanger.
The supply gas and exhaust gas contacted via the total heat exchanger sheet exchange heat through temperature and humidity. The heat-exchanged supply gas is blown into an air supply fan, and is taken into, for example, a room. On the other hand, the exhaust gas that has undergone heat exchange is blown into an exhaust fan and is exhausted, for example, outdoors.
The sheet for a total heat exchanger of the present invention has high moisture permeability and air permeability, and furthermore has excellent carbon dioxide barrier properties, so it is excellent not only in sensible heat but also in latent heat exchange, and has high heat conductivity. Furthermore, mixing of the supply air and the exhaust air is suppressed. Therefore, the total heat exchanger provided with the sheet for a total heat exchanger of the present invention is capable of efficient heat exchange. That is, while suppressing the release of heat or cold heat in the building, it is possible to perform ventilation for discharging the air with an increased carbon dioxide concentration, thereby further increasing the efficiency of the total heat exchanger that maintains the heat effect of cooling and heating. be able to.

  Hereinafter, features of the present invention will be described more specifically with reference to Examples and Comparative Examples. Materials, usage amounts, ratios, processing contents, processing procedures, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples described below.

[Example 1]
<Production of fine cellulose fiber>
(Phosphite group introduction step)
As a raw material pulp, softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solid content: 93% by mass, basis weight: 245 g / m ² sheet, defibrated and measured by Canadian standard freeness (measured according to JIS P 8121: 2012) CSF) was used.
This raw material pulp was subjected to a phosphorylation treatment as follows.
First, a mixed aqueous solution of phosphorous acid (phosphonic acid) and urea was added to the raw material pulp, and 33 parts by mass of phosphorous acid, 120 parts by mass of urea, and 100 parts by mass (absolute dry mass) of the raw material pulp. Water was adjusted to be 150 parts by mass to obtain a chemical-impregnated pulp. Next, the obtained chemical-impregnated pulp was heated with a hot air drier at 165 ° C. for 250 seconds to introduce phosphite groups into cellulose in the pulp to obtain a phosphite-pulp.

(Washing process)
Next, the obtained phosphorylated pulp was subjected to a washing treatment.
The washing treatment is to repeat the operation of pouring 10 L of ion-exchanged water to 100 g of phosphorylated pulp (absolute dry mass), stirring the pulp so as to be uniformly dispersed, obtaining a pulp dispersion, and then filtering and dewatering. Was performed. When the electric conductivity of the filtrate became 100 μS / cm or less, it was regarded as the washing end point.

(Alkali treatment step)
Next, alkali treatment (neutralization treatment) was performed on the phosphorylated pulp after washing as follows.
First, the phosphorylated pulp slurry having a pH of 12 or more and 13 or less is diluted by diluting the washed phosphorylated pulp with 10 L of ion-exchanged water, and gradually adding a 1N aqueous sodium hydroxide solution with stirring. Obtained. Next, the phosphorylated pulp slurry was dehydrated to obtain a phosphorylated pulp subjected to an alkali treatment (neutralization treatment).
Next, the washing treatment was performed on the phosphorylated pulp after the alkali treatment.
The infrared absorption spectrum of the phosphorylated pulp thus obtained after the alkali treatment was measured using FT-IR. As a result, an absorption based on the phosphonic acid group PＯO, which is a tautomer of the phosphite group, was observed around 1210 cm ⁻¹ , indicating that a phosphite group (phosphonate group) was added to the pulp. confirmed.
In addition, the obtained phosphorylated pulp was tested and analyzed by an X-ray diffractometer. As a result, two positions, 2θ = around 14 ° to 17 ° and 2θ = around 22 ° to 23 °, were found. In addition, a peak typical of cellulose I-type crystals was confirmed, and it was confirmed that cellulose I-type crystals were present.
The obtained phosphorylated pulp had a phosphite group content (first dissociated acid content) of 1.51 mmol / g measured by a measurement method described later. In addition, the total amount of dissociated acids was 1.54 mmol / g.

(Fibrillation process)
Ion-exchanged water was added to the phosphorylated pulp obtained through the alkali treatment step and stirred to prepare a slurry having a solid concentration of 2% by mass. This slurry was treated twice at a pressure of 200 MPa with a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine cellulose fiber dispersion containing fine cellulose fibers. X-ray diffraction confirmed that the fine cellulose fibers maintained cellulose type I crystals. Moreover, when the fiber width of the fine cellulose fiber was measured using a transmission electron microscope, it was 3 to 5 nm.

<Preparation of sheet for total heat exchanger>
Pulp prepared by blending NBKP (softwood bleached kraft pulp: Needle Bleached Kraft Pulp) and LBKP (hardwood bleached kraft pulp) at a ratio of 65:35 (mass ratio) was beaten to 450 ml with Canadian Standard Freeness and aluminum sulfate. 1.0 part by mass and 0.01 part by mass of an alkyl ketene dimer (size pine K-903-20, manufactured by Arakawa Chemical Industries, Ltd.) as a sizing agent were added to 100 parts by mass of pulp. Using this stock, high-quality paper having a basis weight of 60 g / m ^{2 was} produced by a fourdrinier multi-cylinder paper machine.
Then, the fine paper obtained above is used as a base material, and the fine cellulose fiber dispersion liquid obtained above is dried with a Mayer bar on one surface of the base material, and the basis weight of fine cellulose fibers (hereinafter, CNF) is applied ( (Coating amount) was 0.4 g / m ² to form a fiber layer.
Subsequently, lithium chloride (manufactured by Wako Pure Chemical Industries, Ltd.) as a moisture absorbent was impregnated and dried so that the basis weight (coating amount) after drying with mangle roll was 5.1 g / m ² . A sheet for a total heat exchanger was prepared. The total heat exchanger sheet had a basis weight of 72 g / m ² and a water content of 10% by mass.

[Example 2]
Example 1 was repeated except that in place of lithium chloride, calcium chloride (manufactured by Wako Pure Chemical Industries, Ltd.) was impregnated and dried so that the coating amount after drying was 5.1 g / m ^2. Similarly, a sheet for a total heat exchanger was produced. The total heat exchanger sheet had a basis weight of 74 g / m ² and a water content of 11% by mass.

[Example 3]
In Example 1, the fine cellulose fiber dispersion was applied so that the coating amount of the fine cellulose fibers (CNF) after drying was 0.8 g / m ^2, and then lithium chloride (Wako Pure Chemical Industries, Ltd.) was used as a moisture absorbent. A sheet for a total heat exchanger was prepared in the same manner as in Example 1, except that the dried product was impregnated and dried so that the mass after drying was 5.3 g / m ² . The total heat exchanger sheet had a basis weight of 78 g / m ² and a water content of 12% by mass.

[Example 4]
Example 3 was repeated except that calcium chloride (manufactured by Wako Pure Chemical Industries, Ltd.) was impregnated and dried so that the coating amount after drying was 5.0 g / m ^{2 in place of} lithium chloride. Similarly, a sheet for a total heat exchanger was produced. The sheet for total heat exchanger had a basis weight of 76 g / m ² and a water content of 10% by mass.

[Example 5]
A pulp prepared by mixing NBKP and LBKP at a ratio of 50:50 (mass ratio) was beaten to 170 ml with a Canadian standard freeness, and 1.0 part of aluminum sulfate and 0.01 part of an alkyl ketene dimer as a sizing agent (size pine K-903-) were used. 20, Arakawa Chemical Industry Co., Ltd.) and 0.15 parts of wet paper strength agent (Alafix 255, Arakawa Chemical Industry Co., Ltd.) were added to 100 parts by mass of pulp. Using this stock, semi-glassine paper having a basis weight of 40 g / m ² was formed by a fourdrinier multi-cylinder paper machine.
Next, using the semi-glassine paper obtained above as a base material, a fine cellulose fiber dispersion was dried on one surface of the base material with a Mayer bar in the same manner as in Example 1 after drying the fine cellulose fibers (CNF). Coating was performed so that the coating amount was 0.4 g / m ² to form a fiber layer.
Next, lithium chloride (manufactured by Wako Pure Chemical Industries, Ltd.) was impregnated and dried with a mangle roll such that the coating amount after drying was 5.4 g / m ² to prepare a sheet for a total heat exchanger. did. The total heat exchanger sheet had a basis weight of 58 g / m ² and a water content of 16% by mass.

[Example 6]
Example 5 was repeated except that calcium chloride (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of lithium chloride and impregnated and dried so that the coating amount after drying was 5.1 g / m ^2. Similarly, a sheet for a total heat exchanger was produced. The total heat exchanger sheet had a basis weight of 58 g / m ² and a water content of 17% by mass.

[Comparative Example 1]
A sheet for a total heat exchanger was prepared in the same manner as in Example 1 except that water was applied and impregnated in place of the fine cellulose fiber dispersion and the moisture absorbent. The total heat exchanger sheet had a basis weight of 60 g / m ² and a water content of 5% by mass.

[Comparative Example 2]
A sheet for a total heat exchanger was prepared in the same manner as in Example 1 except that water was impregnated in place of the hygroscopic agent. The total heat exchanger sheet had a basis weight of 63 g / m ² and a water content of 4% by mass.

[Comparative Example 3]
A sheet for a total heat exchanger was prepared in the same manner as in Example 5 except that water was applied and impregnated in place of the fine cellulose fiber dispersion and the moisture absorbent in Example 5. The total heat exchanger sheet had a basis weight of 40 g / m ² and a water content of 5% by mass.

[Comparative Example 4]
A sheet for a total heat exchanger was prepared in the same manner as in Example 5, except that water was impregnated in place of the moisture absorbent in Example 5. The total heat exchanger sheet had a basis weight of 41 g / m ² and a water content of 3% by mass.

[Evaluation and analysis]
<Measurement of phosphorus oxo acid group content>
The phosphite group content of the fine cellulose fiber dispersion is determined by diluting the phosphite-pulp pulp with ion-exchanged water so that the content becomes 0.2% by mass. After performing the treatment process according to above, the measurement was performed by performing titration using an alkali.
In the treatment step using an ion-exchange resin, 1/10 by volume of a strongly acidic ion-exchange resin (Amberjet 1024; manufactured by Organo Co., Ltd., conditioned) is added to the fine cellulose fiber-containing slurry, followed by shaking for 1 hour. After that, the mixture was poured onto a mesh having a mesh size of 90 μm to separate the resin and the slurry, thereby converting the phosphorus oxo acid group into an acid form.
In addition, titration using an alkali measures a change in the pH value of the slurry while adding 10 μL of a 0.1N sodium hydroxide aqueous solution to the slurry containing fine cellulose fibers after treatment with an ion-exchange resin in 5 seconds. It was done by doing. The titration was performed 15 minutes before the start of the titration while blowing nitrogen gas into the slurry.
In the neutralization titration, two points at which the increment (differential value of the pH with respect to the amount of alkali added) is maximum are given on a curve in which the measured pH is plotted against the amount of alkali added. Among these, the maximum point of the increment obtained first by adding the alkali is called a first end point, and the maximum point of the increment obtained next is called a second end point. The amount of alkali required from the start of the titration to the first end point is equal to the amount of the first dissociated acid in the slurry used for the titration. In addition, the amount of alkali required from the start of titration to the second end point is equal to the total amount of dissociated acid in the slurry used for titration. The amount of first dissociated acid (mmol / g) obtained by dividing the amount of alkali (mmol) required from the start of titration to the first end point by the solid content (g) in the slurry to be titrated is converted to a phosphite group. (Mmol / g). The value obtained by dividing the amount of alkali (mmol) required from the start of titration to the second end point by the solid content (g) in the slurry to be titrated was defined as the total amount of dissociated acid (mmol / g).

<Moisture content (moisture content)>
The moisture content (hereinafter, also simply referred to as moisture content) of the substrate and the obtained sheet for total heat exchanger was measured in accordance with JIS P 8127: 2010.

<Basic weight>
The basis weight of the sheet for the total heat exchanger was measured according to JIS P 8124: 2011.

<Thickness>
The thickness of the sheet for total heat exchanger was measured in accordance with JIS P 8118: 2014.

<Density>
The density of the sheet for the total heat exchanger was calculated from the basis weight and the paper thickness obtained by the above-described measurement method.

<Water contact angle>
According to JIS R 3257: 1999, using a dynamic water contact angle tester (1100 DAT, manufactured by Fibro), 4 μL of distilled water was dropped on the surface of the sheet for the total heat exchanger, and 0.1 second after the dropping, The contact angle was measured. The measurement was performed on each of the fiber layer-side surface (CNF surface) and the base material layer-side surface (back surface).

<Air permeability>
JAPAN TAPPI Paper Pulp Test Method No. 5-2: The air permeability of the sheet for the total heat exchanger was measured in accordance with the Oken type air permeability method of 2000.

<Carbon dioxide barrier property>
A measuring apparatus in which a carbon dioxide (CO ₂ ) analyzer is installed inside an acrylic cubic container having a square window of 20 cm on each side at the center of each of four side surfaces and one upper surface. And
In a state in which a 25 cm square sheet for a total heat exchanger was stuck to each window of the measuring apparatus, 5,000 ppm of carbon dioxide was sealed in the container, and the concentration of CO ₂ was reduced to 15 at 20 ° C. × 65%. Measurements were taken four times every minute for a total of one hour.
After 15 minutes, 30 minutes, 45 minutes, and 60 minutes, the reduction rate of the carbon dioxide concentration at each time point is determined from the measured values after 60 minutes, and the average is further determined to be the carbon dioxide concentration reduction rate of the measured sample. . The lower the rate of decrease in carbon dioxide concentration, the more excellent the heat exchanger sheet is in the carbon dioxide (CO ₂ ) barrier properties.
A sheet having a carbon dioxide concentration reduction rate of 1.3% or less is suitably used as a sheet for a total heat exchanger.

<Moisture permeability>
It was measured under the conditions of 20 ° C. and 65% RH in accordance with JIS Z 0208: 1976.
However, the moisture permeability was calculated as follows.
The mass increment (g) one hour after the start of the test is A, the mass increment (g) from one hour to two hours after the start of the test is B, and the mass increment C per hour is calculated by the following equation (1). Was. This value was converted into a value per 1 m ^{2 of} the moisture-permeable sheet per 24 hours to obtain the moisture permeability (g / (m ² · 24h)).
Mass increment per hour C = (A + B) / 2 (1)
The results of Examples and Comparative Examples are shown in Table 1 below.

  The sheet for a total heat exchanger of the present invention has high moisture permeability and air permeability, and is also excellent in carbon dioxide barrier properties. Therefore, a total heat exchanger that is suitably used as a liner of a total heat exchanger element and that is configured using the total heat exchanger element has high carbon dioxide barrier properties and heat exchange properties.

Claims (11)

A base material layer,
Having a fiber layer provided on the base material layer,
The fiber layer contains fine cellulose fibers having a phosphite group having a fiber width of 1,000 nm or less,
The water content is 8% by mass or more;
Further comprises a moisture absorbent, absorbing moisture agent, Ri metal halide der,
Ru Der moisture permeability of 2,800g ^/ (m 2 · 24hr) or more,
Sheet for total heat exchanger.   The sheet for a total heat exchanger according to claim 1, wherein the moisture absorbent is at least one selected from the group consisting of lithium chloride and calcium chloride.   The sheet for a total heat exchanger according to claim 1 or 2, wherein the content of the moisture absorbent is 100 parts by mass or more based on 100 parts by mass of the fine cellulose fibers.   The sheet for a total heat exchanger according to any one of claims 1 to 3, wherein a contact angle of water on the surface on the fiber layer side is 50 ° or more.   D1 / D2 is 0.25 or more and 4 or less when the contact angle of water on one surface of the sheet for a total heat exchanger is D1 and the contact angle of water on the other surface is D2. The sheet for a total heat exchanger according to any one of the above.   The sheet for a total heat exchanger according to any one of claims 1 to 5, wherein the fine cellulose fiber has a fiber width of 30 nm or less. The sheet for a total heat exchanger according to any one of claims 1 to 6, wherein the basis weight of the fine cellulose fibers is 0.1 g / m ² or more and 3 g / m ² or less. The sheet for a total heat exchanger according to any one of claims 1 to 7, wherein the sheet has a thickness of 20 µm or more and 150 µm or less. Basis weight is 10g / m ² More than 300g / m ² The sheet for a total heat exchanger according to any one of claims 1 to 8, which is: Total heat having exchanger sheet, total heat exchanger element according to any one of claims 1-9. A total heat exchanger comprising the total heat exchanger element according to claim 10 .