JP6480760B2 - Coolant and cold pack - Google Patents

Description

  The present invention relates to a cryogen and a cryogen pack.

  In order to prevent the temperature rise of fresh foods, pharmaceuticals, etc., the cryogen pack is used by being packed together with these items during transportation. Since it is packed with fresh foods, pharmaceuticals, etc., the cryopreservation pack needs to consider safety in addition to the cold storage capacity. As this cold-reserving agent pack, a container in which a cold-retaining agent obtained by mixing a water-retaining material such as a water-absorbing resin in water is packed is commercially available. The cold-reserving agent pack keeps the temperature of the object to be kept near the melting temperature of water by utilizing the fact that water solidified in advance at a low temperature melts at a constant temperature. At this time, the water retention material has an effect of increasing the time until the water is completely melted (cold retention time) by fixing the water molecules and suppressing the diffusion of heat of the water molecules.

  As such a water retaining material, for example, carboxymethyl cellulose (CMC) is known. When this CMC is mixed with water as it is, the CMC is not sufficiently dissolved and easily settles, so that the CMC is unevenly distributed when the cooling agent is solidified, and sufficient cooling time cannot be obtained. For this reason, it is necessary to improve the dispersibility of CMC. As a method for improving the dispersibility of CMC, a method of granulating CMC by granulation or surface treatment with a crosslinking agent, a surfactant or the like has been proposed (see JP 2009-298955 A). ).

  However, in the CMC processed as described above, there is a risk that the CMC's original cold-retaining ability may not be sufficiently exerted due to its shape and surface properties, and the cold-retention time of the conventional cold-retaining agent using such a CMC is It is not long enough.

JP 2009-298955 A

  The present invention has been made on the basis of the above-mentioned circumstances, has a high safety, a high water dispersibility of the water retaining material, and has a long cooling time, and a cryogen pack using the cold retaining agent. It is intended to provide.

  The present inventors diligently studied the long-time cold-retaining agent. As the volume-average particle diameter measured by the laser diffraction method in the water-dispersed state of the fine cellulose fiber is reduced by beating, the water of the fine cellulose fiber is reduced. It has been found that the dispersibility with respect to water increases, and the cooling time of the cooling agent increases. On the other hand, when the volume average particle diameter of the fine cellulose fiber is further reduced, it has been found that the effect of suppressing the heat diffusion of water molecules of the fine cellulose fiber is lowered. In other words, by using fine cellulose fibers with a volume average particle diameter of fine cellulose fibers within a certain range by moderate beating as a water retention material, water dispersibility of the water retention material is increased and drastically cooled by the cold insulation agent. The inventors have found that the time can be increased and have completed the present invention.

  That is, the cold-reserving agent according to the present invention made to solve the above-mentioned problems is a cold-retaining agent containing water and a water-retaining material dispersed in the water, and the main component of the water-retaining material is fine cellulose fibers. The volume average particle diameter measured by a laser diffraction method in the water-dispersed state of the fine cellulose fiber is 20 μm or more and 175 μm or less.

  Since the cold-retaining agent contains fine cellulose fibers having a volume average particle diameter within the above range, the water-retaining material has high dispersibility in water and has a long cold-retaining time. In addition, the fine cellulose fiber is made from natural plants, and is excellent in safety against fresh foods and pharmaceuticals.

  In addition, the present inventor has a fine cellulose fiber having a large volume average particle diameter and a long fiber length by moderate beating, and a fine cellulose fiber having a small volume average particle diameter and a short fiber length by further beating. It has been found that the use of a mixed water retention material can further improve the water dispersibility of the water retention material and further improve the cold retention time of the cold insulation agent. Although it is not clear why the use of a water retention material in which two types of fine cellulose fibers having different volume average particle diameters are mixed increases the water dispersibility of the water retention material and increases the cold retention time of the cryogen. Guesses as follows. First, it is considered that the first fine cellulose fiber having a relatively long fiber length is easy to fix water molecules by forming a hydrophilic three-dimensional network, and has a high effect of suppressing heat diffusion of water molecules. . And since the fiber length of the 2nd fine cellulose fiber is shorter than the 1st fine cellulose fiber, the dispersibility with respect to water is higher than the 1st fine cellulose fiber. Therefore, the 2nd fine cellulose fiber can prevent that the 1st fine cellulose fiber settles by constituting a three-dimensional network with the 1st fine cellulose fiber, and can improve the dispersibility of the whole water retention material. . From the above, it is considered that the water dispersibility of the water-retaining material is increased by the synergistic effect of the first fine cellulose fiber and the second fine cellulose fiber, and the cold keeping time of the cold-retaining agent is increased.

  That is, the fine cellulose fiber preferably includes a first fine cellulose fiber and a second fine cellulose fiber, and the volume average particle diameter measured by a laser diffraction method in the water dispersion state of the first fine cellulose fiber is 140 μm or more and 200 μm or less is preferable, and the volume average particle diameter measured by a laser diffraction method in the water dispersion state of the second fine cellulose fiber is preferably 15 μm or more and less than 140 μm. Thus, the volume average particle diameter is within the above range, and the first fine cellulose fiber having a relatively long fiber length is included as a water retention material, so that the effect of the water retention material that suppresses the diffusion of heat of water molecules is obtained. can get. Moreover, the dispersibility with respect to the water of a water retention material is acquired by including the 2nd fine cellulose fiber whose said volume average particle diameter is in the said range and whose fiber length is shorter than a 1st fine cellulose fiber as a water retention material. . For this reason, the dispersibility with respect to the water of a water retention material and the cold retention time of a cold insulating agent can be improved by the above-mentioned synergistic effect by including a 1st fine cellulose fiber and a 2nd fine cellulose fiber as a water retention material. .

  As content of the said 1st fine cellulose fiber with respect to the whole said fine cellulose fiber, 20 mass% or more and 95 mass% or less are preferable. Thus, by making content of the said 1st fine cellulose fiber with respect to the whole said fine cellulose fiber into the said range, a water molecule can be fixed more reliably, maintaining the dispersibility of the whole water retention material. For this reason, the effect of increasing the cooling time is further enhanced.

  The first fine cellulose fiber may have three peaks in a pseudo particle size distribution curve measured by a laser diffraction method in an aqueous dispersion state. Thus, the content rate of the cellulose of the pulp fiber which has not progressed refinement | miniaturization of a fiber increases by making the 1st fine cellulose fiber into the fine cellulose fiber which has three peaks in the said pseudo particle size distribution curve. For this reason, the 1st fine cellulose fiber can comprise a stronger hydrophilic three-dimensional network, and it is easy to fix a water molecule further. Therefore, the cold insulation time can be further increased.

  The second fine cellulose fiber may have three peaks in a pseudo particle size distribution curve measured by a laser diffraction method in an aqueous dispersion state. Thus, by making the 2nd fine cellulose fiber into the fine cellulose fiber which has three peaks in the said pseudo particle size distribution curve, the content rate of the cellulose of the pulp fiber which has not progressed refinement | miniaturization of a fiber increases. For this reason, it is easy for the second fine cellulose fiber to form a hydrophilic three-dimensional network together with the first fine cellulose fiber, and water molecules are more easily fixed. Therefore, it is possible to further increase the cooling time of the cold-retaining agent while maintaining the water dispersibility of the water-retaining material.

  The second fine cellulose fiber may have one peak in a pseudo particle size distribution curve measured by a laser diffraction method in an aqueous dispersion state. Thus, by making the 2nd fine cellulose fiber into the fine cellulose fiber which has one peak in the said pseudo particle size distribution curve, refinement | miniaturization advances and the content rate of the cellulose whose fiber length is shorter than the 1st fine cellulose fiber Will increase. For this reason, it can prevent more reliably that a 1st fine cellulose fiber settles with a 2nd fine cellulose fiber, and the dispersibility of the whole water retention material further increases. Therefore, since the water retention material can fix more water molecules, the effect of increasing the cold retention time is further enhanced.

  The present invention includes a cryogen pack that includes a bag and the cryogen encapsulated in the bag. Since the cold-reserving agent pack has the cold-retaining agent, the cold-retaining time is long. Therefore, it can be suitably used for preventing temperature rise of fresh foods, pharmaceuticals and the like.

Here, the “main component” means a component having the highest content, for example, a component having a content of 50% by mass or more. In addition, “water retention” refers to JAPAN-TAPPI-No. It is a value measured according to 26: 2000. The “pseudo particle size distribution curve” is a curve showing a volume-based particle size distribution measured using a particle size distribution measuring device (for example, “Microtrac MT-3000II” of Nikkiso Co., Ltd.) in accordance with ISO-13320 (2009). The “volume average particle diameter” is an average particle diameter weighted by volume, and the following formula (1) is used by using the individual particle diameter di and the particle volume Vi measured by the particle size distribution measuring device. ) Means the average value MV calculated.
Volume average particle diameter MV = Σ (di × Vi) / ΣVi (1)

  As described above, the cold-retaining agent of the present invention is excellent in safety, has high water dispersibility in the water-retaining material, and has a long cold-retaining time. Therefore, the said cryogen can be used suitably as a cryogen pack which prevents the temperature rise, such as fresh food and a pharmaceutical.

[First embodiment]
Hereinafter, the cryogen and the cryogen pack of the first embodiment of the present invention will be described.

[ice pack]
The said cold-retaining agent mainly contains water and the water-retaining material disperse | distributed to this water.

<Water>
Water has a relatively large latent heat of melting and is excellent in cooling effect. As a minimum of the content rate of water in a cooling agent, 90 mass% is preferred and 95 mass% is more preferred. On the other hand, as an upper limit of the content rate of the water in a cooling agent, 99.995 mass% is preferable and 99.95 mass% is more preferable. When the content rate of the water in a cold insulating agent is less than the said minimum, there exists a possibility that the cooling effect of a cold insulating agent may become inadequate. On the other hand, when the content of water in the cryogen exceeds the above upper limit, water molecules are not sufficiently fixed by the water-retaining material, and there is a possibility that the cool-in time of the cryogen is shortened.

<Water retention material>
The main component of the water retention material is fine cellulose fibers. The fine cellulose fiber is a fine fiber that does not require defibration among fibers obtained by appropriate defibration of wood-derived pulp or wood-derived pulp.

  The pulp that is the raw material for the fine cellulose fibers is not particularly limited, but is broad-leaved tree bleached kraft pulp (LBKP), hardwood unbleached kraft pulp (LUKP), softwood bleached kraft pulp (NBKP), conifer unbleached kraft pulp (NUKP), Examples thereof include softwood bleached sulfite pulp (NBSP). Among these, LBKP and NBKP, which have a relatively strong tendency to increase the water retention level due to defibrating treatment, are preferred, and LBKP is more preferred. The reason why LBKP is more preferable is as follows. In general, a pulp having a low water retention has more hydrogen bonds between cellulose fibers than a pulp having a high water retention. For example, a wet pulp having no drying history has a high water retention level due to hydrogen bonding of hydroxyl groups on the surface of the pulp with surrounding water molecules. On the other hand, pulp having a drying history brings the cellulose fibers of the pulp closer to each other due to the evaporation of water during drying, and many hydrogen bonds are formed between the cellulose fibers, resulting in fewer hydrogen bonds with water molecules. Therefore, the water retention is lowered. Therefore, in the production of fine cellulose fibers, LBKP having a small hydrogen bond between cellulose fibers, that is, having a high water retention is suitable.

  Furthermore, the present inventor has found that a method of performing a mechanical beating treatment using LBKP having a water retention of 90% or less is preferable as a method for producing fine cellulose fibers. Thus, by using LBKP having a water retention level equal to or lower than the above upper limit and performing a mechanical beating process, it is easy to obtain a water retention material having a relatively high water dispersibility and a relatively long cold retention time when used as a cold insulation agent. The reason is not clear, but the present inventor speculates as follows. In other words, by using mechanical beating as a means for defibrating the cellulose fibers that constitute the pulp, unlike the means for defibration by chemical treatment or enzyme treatment, the treatment is performed without chemically dividing cellulose polymerization. It can be performed. For this reason, it becomes easy to obtain a fine cellulose fiber with a long fiber length, and it is considered that the dispersibility with respect to water and the cold insulation time when used as a cold insulation agent are easy to improve. Examples of such mechanical beating treatment include known methods such as a grinder (stone mill type grinder), a high-pressure homogenizer, and an underwater collision.

  Further, the present inventor has found that when the volume average particle diameter of the fine cellulose fibers is reduced by beating, the dispersibility of the fine cellulose fibers in water is increased and the cold keeping time of the cold-retaining agent is increased. On the other hand, when the volume average particle diameter of the fine cellulose fiber is further reduced, it has been found that the effect of suppressing the heat diffusion of water molecules of the fine cellulose fiber is lowered. In other words, by using fine cellulose fibers with a volume average particle diameter of fine cellulose fibers within a certain range by moderate beating as a water retention material, water dispersibility of the water retention material is increased and drastically cooled by the cold insulation agent. The inventors have found that the time can be increased and have completed the present invention. That is, the lower limit of the volume average particle diameter of the fine cellulose fibers is 20 μm, more preferably 30 μm, still more preferably 70 μm, and particularly preferably 100 μm. On the other hand, the upper limit of the volume average particle diameter of the fine cellulose fibers is 175 μm, more preferably 160 μm, and even more preferably 150 μm. When the volume average particle diameter of the fine cellulose fibers is less than the above lower limit, the fiber length of the fine cellulose fibers is shortened, so the effect of suppressing the heat diffusion of water molecules is reduced, and the cooling time of the cryogen is reduced. There is a risk. On the contrary, when the volume average particle diameter of the fine cellulose fiber exceeds the above upper limit, the water-retaining property of the water-retaining material is insufficient, so that the cold-retaining time of the cold-retaining agent may be reduced.

  As a minimum of the water retention of the said fine cellulose fiber, 220% is preferable, 230% is more preferable, and 280% is further more preferable. On the other hand, the upper limit of the water retention of the fine cellulose fiber is preferably 380%, more preferably 335%, and further preferably 320%. When the water retention of the fine cellulose fiber is less than the lower limit, the effect of increasing the cool time may be insufficient. On the other hand, when the water retention of the fine cellulose fiber exceeds the upper limit, the fine cellulose is defibrated too much and the fine cellulose fiber may be shortened. For this reason, a hydrophilic three-dimensional network cannot be fully constructed, and there is a possibility that the effect of suppressing the heat diffusion of water molecules will be insufficient.

  As a minimum of the content rate of the water retention material in a cooling agent, 0.005 mass% is preferable and 0.05 mass% is more preferable. On the other hand, as an upper limit of the content rate of the said water retention material, 10 mass% is preferable and 5 mass% is more preferable. When the content rate of the water retention material is less than the lower limit, water molecules are not sufficiently fixed by the water retention material, and the cold retention time of the cold insulation agent may be shortened. On the contrary, when the content rate of the water-retaining material exceeds the upper limit, the water content rate in the cold-retaining agent is decreased, so that the cooling effect of the cold-retaining agent may be insufficient.

  The lower limit of the B-type viscosity of the aqueous dispersion having a water content of 1% by mass is preferably 10 cps. On the other hand, the upper limit of the B-type viscosity is preferably 5000 cps, more preferably 4000 cps, and still more preferably 3500 cps. When the B-type viscosity is less than the lower limit, the fine cellulose fibers are difficult to form a three-dimensional network, and the effect of suppressing the heat diffusion of water molecules may be insufficient. On the other hand, when the B-type viscosity exceeds the upper limit, the viscosity may make it difficult to fill the bag body or the cold container. Here, “B-type viscosity” is a value measured according to JIS-Z8803 (2011).

  Moreover, as a minimum of the pulp viscosity of a fine cellulose fiber, 1.5 cps is preferable and 3.6 cps is more preferable. On the other hand, the upper limit of the pulp viscosity is preferably 8.5 cps, and more preferably 6.5 cps. When the said pulp viscosity is less than the said minimum, there exists a possibility that it may become difficult to intertwine fine cellulose fibers. On the contrary, when the pulp viscosity exceeds the upper limit, aggregation of fine cellulose fibers may not be sufficiently controlled. In any case, it becomes difficult for the fine cellulose fibers to form a three-dimensional network, and there is a possibility that the effect of suppressing the heat diffusion of water molecules will be insufficient. The “pulp viscosity” is a value measured according to JIS-P8215 (1998).

<Other ingredients>
The cryogen is preferably in the form of a gel so as not to contaminate the items packed together even when the bag body or the cryogen container enclosing the cryogen is damaged. In order to make the cooling agent into a gel, for example, a crosslinking agent may be added. As such a crosslinking agent, for example, a polyvalent metal salt can be used. As the polyvalent metal salt, a divalent or trivalent metal salt is preferably used. Potash alum, aluminum sulfate, aluminum hydroxide, ferrous sulfate, ferrous chloride, zinc sulfate, barium chloride, chromium nitrate, acetic acid Lead, cupric chloride, tin chloride, silver nitrate and the like can be mentioned. Among these, potash alum, which has good tactile sensation during use, is preferable. As an upper limit of the addition amount of potash alum, 0.6 mass part is preferable with respect to 100 mass parts of water. When the added amount of potash alum exceeds the above upper limit, it becomes difficult for the water-retaining material to take in water, and the effect of increasing the cooling time of the cold-retaining agent may be insufficient.

  Moreover, a freezing point depressant may be added to the cryogen. By adding a freezing point depressant, the cool temperature of the cool agent can be lowered. As the freezing point depressant, a food or food additive is preferable from the viewpoint of safety. Such foods or food additives include ethanol, sodium chloride, sodium nitrite, sodium hydrogen sulfite, crystalline sodium sulfite, ammonium chloride, glycerin, potassium nitrate, sodium nitrate, ammonium carbonate, anhydrous potassium carbonate, ammonium hydrogen carbonate, carbonate Sodium hydrogen, crystalline sodium carbonate, anhydrous sodium sulfate, crystalline magnesium sulfate, monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, crystalline monosodium phosphate, anhydrous monosodium phosphate, crystalline disodium phosphate, anhydrous phosphorus Examples thereof include disodium acid, crystalline trisodium phosphate, and anhydrous trisodium phosphate. Among these, ethanol and glycerin are preferable, and glycerin is more preferable from the viewpoint of the flexibility of the cryogen.

  In addition to the components described above, components generally used for the cryogen can be added to the cryogen. Examples of such components include water-soluble polymers such as guar gum, polyvinyl alcohol and starch, polyhydric alcohols such as ethylene glycol, propylene glycol, glycerin and sorbitol for adjusting the freezing temperature, sodium chloride, potassium chloride and sodium nitrate. And salts such as sodium sulfate, preservatives, colorants and the like.

<Method for producing cryogen>
The said cold-retaining agent can be manufactured with a manufacturing method provided with the process of obtaining a fine cellulose fiber by defibration of a pulp fiber, and the process of mixing and preparing the said fine cellulose fiber and water, for example.

(Fine cellulose fiber acquisition process)
In the fine cellulose fiber acquisition step, the pulp fiber is defibrated by a known method for producing fine cellulose using pulp fiber as a raw material, for example, beating treatment of the pulp fiber raw material by a Niagara beater. Although content of the pulp fiber in the said pulp fiber raw material is not specifically limited, For example, it can be 1 mass% or more and 3 mass% or less. The beating process time can be, for example, 20 minutes to 160 minutes. Furthermore, the fine cellulose fibers subjected to the beating treatment may be subjected to a refining treatment by, for example, a method using a grinder (stone mill type grinder), a high-pressure homogenizer, an underwater facing collision, or the like. This miniaturization process may be performed a plurality of times as necessary. The number of repetitions when performing the miniaturization treatment is preferably 1 or more and less than 10 times. In this way, fine cellulose fibers having a desired volume average particle diameter are obtained.

(Mixing preparation process)
In the mixing and preparing step, a cold-retaining agent is obtained by mixing and preparing the fine cellulose fibers obtained in the fine cellulose fiber obtaining step and water. The procedure for mixing and preparing is not particularly limited as long as the desired mixing ratio is obtained. For example, fine cellulose fibers are dispersed in water and mixed and prepared so as to obtain a desired concentration.

<Coolant pack>
The cryogen pack includes a bag and the cryogen enclosed in the bag.

  As a material of the bag, a flexible film or sheet is preferable. Thus, by making the material of a bag into a flexible film or sheet, the cold-reservoir pack can have flexibility and adhesion to goods such as food. As a material of such a bag body, a polymer material generally used for a cryogen pack can be used. Specific examples include polyethylene, polypropylene, polyurethane, polystyrene, polyethylene terephthalate, polyester, polyethylene vinyl acetate, polyvinyl chloride, and nylon. The film or sheet constituting the bag body may have a single layer structure or a multilayer structure in which two or more layers are laminated.

  The lower limit of the average thickness of the bag (in the case of a multilayer structure, the average thickness of the entire layer) is preferably 200 μm, and more preferably 300 μm. On the other hand, the upper limit of the average thickness of the bag is preferably 800 μm and more preferably 600 μm. When the average thickness of the bag body is less than the lower limit, the strength of the bag body is insufficient, and the cold pack may be easily damaged. On the contrary, when the average thickness of the bag body exceeds the upper limit, the flexibility necessary for the cold pack may not be ensured.

  Moreover, the said cryogen pack may have the coating layer which covers all or one part of the outer surface. Thus, by covering the outer surface of the cryogen pack with the coating layer, breakage of the cryogen pack can be prevented. Examples of the material of the coating layer include artificial fibers, natural fibers, woven fabrics, synthetic resins, and buffer materials.

<Advantages>
Since the cold-retaining agent contains fine cellulose fibers having a volume average particle diameter within the above range, the water-retaining material has high dispersibility in water and has a long cold-retaining time. In addition, the fine cellulose fiber is made from natural plants, and is excellent in safety against fresh foods and pharmaceuticals.

  Therefore, the cryogen pack provided with the cryogen can be suitably used to prevent temperature rise of fresh foods, pharmaceuticals and the like.

[Second Embodiment]
Hereinafter, the cryogen of the second embodiment of the present invention will be described.

  The said cold-retaining agent mainly contains water and the water-retaining material disperse | distributed to this water. The main component of the water retention material is fine cellulose fibers. Moreover, the fine cellulose fiber in the second embodiment includes a first fine cellulose fiber and a second fine cellulose fiber having a volume average particle diameter smaller than that of the first fine cellulose fiber and a shortened fiber length. Including. Among these, since water is the same as that of 1st embodiment, description is abbreviate | omitted.

[Water retention material]
Since it is the same as that of 1st embodiment as a pulp which is a raw material of the fine cellulose fiber which is a main component of a water retention material, description is abbreviate | omitted.

(First fine cellulose fiber)
The first fine cellulose fiber has a volume average particle diameter larger than that of the second fine cellulose fiber. The lower limit of the volume average particle diameter of the first fine cellulose fiber is preferably 140 μm, and more preferably 160 μm. On the other hand, the upper limit of the volume average particle diameter of the first fine cellulose fiber is preferably 200 μm, and more preferably 190 μm. When the volume average particle diameter of the first fine cellulose fiber is less than the lower limit, the fine cellulose is defibrated too much, and the first fine cellulose fiber may be shortened. For this reason, a hydrophilic three-dimensional network cannot be fully constructed, and there is a possibility that the effect of suppressing the heat diffusion of water molecules will be insufficient. On the other hand, when the volume average particle diameter of the first fine cellulose fiber exceeds the upper limit, the effect of increasing the cooling time may be insufficient.

  The lower limit of the water retention of the first fine cellulose fiber is preferably 80%, more preferably 90%, and even more preferably 100%. On the other hand, the upper limit of the water retention of the first fine cellulose fiber is preferably 280%, more preferably 200%, and even more preferably 150%. When the water retention of the first fine cellulose fiber is less than the lower limit, the effect of increasing the cold insulation time may be insufficient. On the other hand, when the water retention of the first fine cellulose fiber exceeds the upper limit, the fine cellulose defibration process may proceed excessively and the first fine cellulose fiber may be shortened. For this reason, a hydrophilic three-dimensional network cannot be fully constructed, and there is a possibility that the effect of suppressing the heat diffusion of water molecules will be insufficient.

  As a minimum of content of the 1st above-mentioned fine cellulose fiber to the whole above-mentioned fine cellulose fiber, 20 mass% is preferred and 25 mass% is more preferred. On the other hand, the upper limit of the content of the first fine cellulose fiber is preferably 95% by mass, more preferably 65% by mass, and further preferably 45% by mass. When the content of the first fine cellulose fiber is less than the lower limit, the hydrophilic three-dimensional network cannot be sufficiently formed, and the effect of suppressing the heat diffusion of water molecules may be insufficient. . On the contrary, when the content of the first fine cellulose fiber exceeds the upper limit, the content of the second fine cellulose fiber described later may be insufficient, so that the dispersibility of the entire water retaining material may not be maintained. is there.

  The first fine cellulose fiber may have three peaks in a pseudo particle size distribution curve measured by a laser diffraction method in an aqueous dispersion state. By making the first fine cellulose fiber into a fine cellulose fiber having three peaks in the pseudo particle size distribution curve, the cellulose content of the pulp fiber in which fiber refinement has not progressed in the first fine cellulose fiber. Rise. By using such a first fine cellulose fiber, the water retention material can form a stronger hydrophilic three-dimensional network, and can easily fix water molecules. Therefore, it is possible to further increase the cooling time of the cold-retaining agent.

(Second fine cellulose fiber)
The second fine cellulose fiber has a volume average particle size smaller than that of the first fine cellulose fiber. As a minimum of the volume average particle diameter of the said 2nd fine cellulose fiber, 15 micrometers is preferable and 17 micrometers is more preferable. On the other hand, the volume average particle diameter of the second fine cellulose fiber is preferably less than 140 μm, and more preferably less than 100 μm. When the volume average particle diameter of the second fine cellulose fiber is less than the lower limit, the time for the defibrating treatment becomes longer and the production cost may increase. Conversely, when the volume average particle diameter of the second fine cellulose fiber is not less than the above upper limit, the dispersibility of the second fine cellulose fiber in water is insufficient, and the sedimentation of the first fine cellulose fiber cannot be sufficiently prevented. Since there exists a possibility, there exists a possibility that the increase effect of the cool keeping time of the said cold insulating agent may become inadequate.

  The lower limit of the water retention of the second fine cellulose fiber is preferably 300%, more preferably 3400%, and even more preferably 380%. When the water retention of the second fine cellulose fiber is less than the lower limit, the dispersibility of the second fine cellulose fiber in water is insufficient, and the sedimentation of the first fine cellulose fiber may not be sufficiently prevented. There is a possibility that the effect of increasing the cooling time of the cold-retaining agent may be insufficient. On the other hand, the upper limit of the water retention of the second fine cellulose fiber is not particularly limited, but can be, for example, 500%.

  The second fine cellulose fiber may have three peaks in a pseudo particle size distribution curve measured by a laser diffraction method in an aqueous dispersion state. By making the second fine cellulose fiber into a fine cellulose fiber having three peaks in the pseudo particle size distribution curve, the cellulose content of the pulp fiber in which fiber refinement has not progressed in the second fine cellulose fiber. Rise. By using such second fine cellulose fibers, the second fine cellulose fibers can easily form a hydrophilic three-dimensional network together with the first fine cellulose fibers, and water molecules can be more easily fixed. Therefore, the cold-retaining agent can further increase the cold-retaining time while maintaining the dispersibility of the water-retaining material in water.

  Further, the second fine cellulose fiber may have one peak in a pseudo particle size distribution curve measured by a laser diffraction method in a water dispersion state. By making a 2nd fine cellulose fiber into the fine cellulose fiber which has one peak in the said pseudo particle size distribution curve, refinement | miniaturization advances in a 2nd fine cellulose fiber, and fiber length is shorter than a 1st fine cellulose fiber. Cellulose content increases. By using such second fine cellulose fibers, the second fine cellulose fibers can more reliably prevent the first fine cellulose fibers from settling, and the dispersibility of the entire water retaining material is further enhanced. Therefore, since the water retention material can fix more water molecules, the effect of increasing the cold retention time is further enhanced.

  The volume average particle diameter of the whole fine cellulose fiber (first fine cellulose fiber and second fine cellulose fiber), the water retention of the whole fine cellulose fiber, the content of the water retention material in the cold insulation agent, and the content of the water retention material is 1 mass. The B-type viscosity of the% aqueous dispersion and the pulp viscosity of the fine cellulose fibers can be the same as in the first embodiment, and thus detailed description thereof is omitted.

  Moreover, you may add the component similar to 1st embodiment as another component to the said cold insulating agent.

<Method for producing cryogen>
The cryogen includes, for example, a step of obtaining first fine cellulose fibers by defibration of pulp fibers, a step of obtaining second fine cellulose fibers by defibration of pulp fibers, the first fine cellulose fibers, and the first 2 and a step of mixing and preparing fine cellulose fibers and water.

(First fine cellulose fiber acquisition step)
Since the 1st fine cellulose fiber acquisition process is the same as the fine cellulose fiber acquisition process in 1st embodiment, description is abbreviate | omitted. In addition, as a 1st fine cellulose fiber, the fine thing which does not require defibration among pulp derived from wood can also be used.

(Second fine cellulose fiber acquisition step)
In the second fine cellulose fiber acquisition step, defibration progresses more than the first fine cellulose fiber, and a fine cellulose fiber with a reduced volume average particle diameter is obtained. Although it does not specifically limit as a method of obtaining a 2nd fine cellulose fiber, For example, it uses by using the same pulp raw material as a 1st fine cellulose fiber, and making it a longer beating process time, for example, 30 minutes or more and less than 200 minutes Examples thereof include a method and a method obtained by further refining a part of the first fine cellulose fiber.

(Mixing preparation process)
In the mixing preparation step, the first fine cellulose fiber obtained in the first fine cellulose fiber acquisition step, the second fine cellulose fiber obtained in the second fine cellulose fiber acquisition step, and water are mixed and prepared. By doing so, a cold insulation agent is obtained. The procedure for preparing the mixture is not particularly limited as long as the desired mixing ratio is obtained, and examples thereof include the following procedures. First, a 1st fine cellulose fiber and a 2nd fine cellulose fiber are mixed so that it may become a desired ratio, and a water retention material is obtained. Next, the water retaining material is dispersed in water and mixed and prepared to have a desired concentration.

<Advantages>
The cold-retaining agent includes a first fine cellulose fiber having a volume average particle diameter within the above-described range and a relatively long fiber length as a water-retaining material, thereby preventing water from being diffused by water molecules. An effect is obtained. Moreover, the said cold-retaining agent contains the 2nd fine cellulose fiber whose said volume average particle diameter is in the said range, and whose fiber length is shorter than a 1st fine cellulose fiber as a water retention material, and with respect to the water of a water retention material. Dispersibility is obtained. For this reason, the said cold-retaining agent contains the 1st fine cellulose fiber and the 2nd fine cellulose fiber as a water-retaining material, and improves the dispersibility with respect to the water of a water-retaining material and the cold-retaining time of a cold-retaining agent by the synergistic effect. can do.

[Other Embodiments]
The cryogen of the present invention is not limited to the above embodiment.

  In the above-described embodiment, the case of the cold-retaining agent including water and the water-retaining material has been described. However, a cold-retaining agent including water, alcohol, and the water-retaining material may be used. Examples of such alcohols include monoalcohols such as methyl alcohol and ethyl alcohol, and polyhydric alcohols such as propylene glycol and glycerin.

  These alcohols are also effective as cryogens and can be selected so that the cryogen has a desired melting temperature. When alcohol is used as a cryogen, a polyhydric alcohol having flexibility even in a cooled and solidified state and having a freezing point of −20 ° C. or lower is preferable. Furthermore, among the polyhydric alcohols, propylene glycol having a freezing point (−59 ° C.) sufficiently lower than the cooling temperature of the freezer of the household refrigerator is more preferable.

  As an upper limit of content of the said alcohol with respect to 100 mass parts of water, 60 mass parts is preferable. When the content of the alcohol exceeds the above upper limit, the latent heat of fusion of the whole cryogen is insufficient, and the effect of increasing the cool time may be insufficient.

  The content of the water-retaining material with respect to the whole cold-retaining agent including water, alcohol and water-retaining material can be the same as in the case of the cold-retaining agent including water and the water-retaining material.

  Moreover, as a minimum of the content rate of the water with respect to the whole cooling agent containing water, alcohol, and a water retention material, 60 mass% is preferable and 65 mass% is more preferable. On the other hand, the upper limit of the water content is preferably 99.99 mass%, more preferably 99.9 mass%. When the content rate of the water is less than the lower limit, the cooling effect of the cooling agent may be insufficient. On the contrary, when the content rate of the water exceeds the upper limit, water molecules are not sufficiently fixed by the water-retaining material, and the cold-retaining time of the cold-retaining agent may be shortened.

  Moreover, the said cryogen pack is not limited to the use which prevents a temperature rise, such as fresh food and a pharmaceutical, but can be used also for another use as long as a cold preservation and cooling are required. For example, it may be used to cool or cool a specific part of the body.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. In Examples and Comparative Examples, measurement was performed by the following method.

<Water retention level>
JAPAN-TAPPI-No. The water retention of the first fine cellulose fibers and the second fine cellulose fibers was measured by a method for measuring the water retention based on 26: 2000.

<Volume average particle diameter>
In accordance with ISO-13320 (2009), the volume average of fine cellulose fibers from the volume-based particle size distribution in an aqueous dispersion of fine cellulose fibers using a particle size distribution measuring device (“Microtrac MT-3000II” of Nikkiso Co., Ltd.) The particle size was obtained. Moreover, about Examples 9-13 which mixed two types of fine cellulose fibers, each fineness was based on the volume reference | standard particle size distribution in the aqueous dispersion of a 1st fine cellulose fiber, and the aqueous dispersion of a 2nd fine cellulose fiber. The volume average particle diameter of the cellulose fiber was also acquired.

<Durability of the cold insulation effect>
The sustainability of the cooling effect was measured by the following method. First, 10 g of a cryogen stored at a temperature of −20 ° C. for 16 hours or more was prepared. Next, this cold-retaining agent was allowed to stand in a constant temperature and humidity environment at a temperature of 23 ° C. and a humidity of 50%, and the residual solid content after 60 minutes was determined. The residual solid content (% by mass) is a value calculated as a ratio by subtracting the mass of the residual solid after 60 minutes from the mass immediately before standing in a constant temperature and humidity environment. When this residual solid content exceeds 26% by mass, it can be determined that the sustainability of the cooling effect is excellent.

Example 1
As fine cellulose fibers, a pulp raw material containing 2% by mass of LBKP was fibrillated by beating for 30 minutes with a Niagara beater and prepared as a water retention material. Water was added so that the content of the water-retaining material was 1.0% by mass, and the cold-retaining agent of Example 1 was obtained.

(Examples 2 to 5, Comparative Example 1)
Except having changed the beating time of Example 1 as shown in Table 1, the cold insulating agents of Examples 2 to 5 and Comparative Example 1 were obtained in the same manner as Example 1.

(Examples 6 to 8, Comparative Example 2)
A pulp raw material containing 2% by mass of LBKP as fine cellulose fibers was beaten with a Niagara beater for 150 minutes. Then, what was defibrated by grinding according to the number of times of miniaturization shown in Table 1 using a “supermass colloider 10 inch” of Masuko Sangyo Co., Ltd., which is a millstone mill, was prepared as a water retention material. It prepared by adding water so that content of this water retention material might be 1.0 mass%, and the refrigerant | coolant of Examples 6-8 and the comparative example 2 was obtained.

(Examples 9 to 13)
The fine cellulose fiber of Comparative Example 1 was prepared as the first fine cellulose fiber, and the fine cellulose fiber of Comparative Example 2 was prepared as the second fine cellulose fiber. Next, it mixed so that ratio of content of the 1st fine cellulose fiber and the 2nd fine cellulose fiber might become the mixing ratio shown in Table 1, and the water retention material was obtained. Furthermore, it prepared by adding water so that content of this water retention material might be 1.0 mass%, and the cold-retaining agent of Examples 9-13 was obtained.

(Comparative Example 3)
As Comparative Example 3, carboxymethyl cellulose (CMC) used for a commercially available cold-retaining agent was prepared. The content of the water retaining material is 1.0% by mass.

  In Table 1, “-” means that there is no data because the cryogen does not have the corresponding fine cellulose fiber. The beating time of 0 minutes means that no beating is performed.

  As shown in the results of Table 1, the cryogens of Examples 1 to 13 have a larger amount of residual solid after 60 minutes than the cryogens of Comparative Examples 1 to 3. It can be seen that the cold-retaining agents of Examples 1 to 13 are excellent in sustainability of the cold-retaining effect because the main component of the water-retaining material is fine cellulose fibers and the volume average particle diameter is within a predetermined range. On the other hand, since the volume average particle diameter of the fine cellulose fibers exceeds the upper limit of the above predetermined range and the fiber length of the fine cellulose fibers is long, the water retaining material of Comparative Example 1 is insufficient in water dispersibility. However, it is speculated that the sustainability of the cooling effect is inferior. Moreover, since the volume average particle diameter of the fine cellulose fiber is less than the lower limit of the predetermined range and the fiber length of the fine cellulose fiber is short, the cryogen of Comparative Example 2 has an effect of suppressing the heat diffusion of water molecules. It is presumed that the sustainability of the cooling effect is inferior. Furthermore, since the cold-retaining agent of Comparative Example 3 does not use fine cellulose fibers as the water-retaining material, it is considered that the sustainability of the cold-retaining effect is inferior.

  When it sees in more detail, the refrigerant | coolant of Examples 9-13 which mixed the fine cellulose fiber of the comparative example 1 and the comparative example 2 and made the water retention material 60 minutes later than the refrigerant | coolant of the comparative example 1 and the comparative example 2 There are many residual solids. For example, when Example 6 and Example 10 in which the volume average particle diameter of the whole fine cellulose fiber is substantially equal are compared, Example 10 using a water retention material in which two kinds of fine cellulose fibers are mixed is 60 minutes. There is much residual solid content after the passage. For this reason, a water retention material in which a first fine cellulose fiber having a volume average particle diameter of 140 μm or more and 200 μm or less and a second fine cellulose fiber having a volume average particle diameter of 15 μm or more and less than 140 μm is used. Thus, it can be seen that the synergistic effect improves the cooling time of the cryogen.

  As described above, the cold-retaining agent of the present invention has high water-dispersibility of the water-retaining material and a long cold-retaining time. Therefore, the said cryogen can be used suitably as a cryogen pack which prevents the temperature rise, such as fresh food and a pharmaceutical.

Claims (7)

A cryogen containing water and a water retention material dispersed in the water,
The main component of the water retention material is fine cellulose fiber,
A cryogenic agent having a volume average particle diameter of 20 μm or more and 175 μm or less measured by a laser diffraction method in a water-dispersed state of the fine cellulose fiber. The fine cellulose fiber includes a first fine cellulose fiber and a second fine cellulose fiber,
The volume average particle diameter measured by a laser diffraction method in an aqueous dispersion state of the first fine cellulose fiber is 140 μm or more and 200 μm or less,
The cold-retaining agent according to claim 1, wherein a volume average particle diameter measured by a laser diffraction method in the water-dispersed state of the second fine cellulose fiber is 15 µm or more and less than 140 µm.   The cold-retaining agent according to claim 2, wherein the content of the first fine cellulose fiber with respect to the whole fine cellulose fiber is 20% by mass or more and 95% by mass or less.   The cold-retaining agent according to claim 2 or 3, wherein the first fine cellulose fiber has three peaks in a pseudo particle size distribution curve measured by a laser diffraction method in an aqueous dispersion state.   The cryogen according to claim 2, 3 or 4, wherein the second fine cellulose fiber has three peaks in a pseudo particle size distribution curve measured by a laser diffraction method in an aqueous dispersion state.   The cold-retaining agent according to claim 2, 3 or 4, wherein the second fine cellulose fiber has one peak in a pseudo particle size distribution curve measured by a laser diffraction method in an aqueous dispersion state.   A cryogen pack comprising a bag and the cold insulator according to any one of claims 1 to 6 enclosed in the bag.