JP5216979B2 - desiccant - Google Patents

Description

  The present invention relates to a desiccant.

  When transporting freight such as electronic parts, precision equipment, machine tools, industrial machinery, etc., due to recent developments in aviation conditions, if it can be transported by air mail, the transportation time will be short, so it will be within the environment surrounding the cargo. The adverse effects on cargo caused by moisture are not particularly problematic.

  However, there is a problem that the cargo cannot be loaded on an airplane due to the size of the cargo, etc., and even if it can be loaded on an airplane, there is a problem that the transportation cost is higher than shipping. Is still generally transported by sea.

  In the case of transport by sea, those cargos are exposed to moisture for a long time. In addition, depending on the ship's route, the temperature difference between the surroundings of the cargo increases, so condensation may occur on the ceiling surface in the container in which the cargo is stored, and water droplets may drop on the cargo. There is a problem that the cargo is polluted or rust is generated by the drip of moisture or water drops.

  In order to deal with such problems, conventional measures such as packing these cargoes with packing materials such as vinyl and cardboard, or covering them with a dew condensation prevention sheet have been adopted. I was trying to protect against dripping.

  However, packing the cargo with packing materials such as vinyl and cardboard can solve the problem of dripping water caused by condensation, but it will still pack the cargo with air containing moisture at the time of packing. Humidity in the air inside the cargo package becomes a problem. For this reason, desiccant is packed together with the cargo in order to reduce the influence of moisture in the environment around the cargo.

  Other uses of such desiccants include freeze-dried foods such as dried vegetables and dried meat, instant coffee, grilled laver, seasoned laver, arabe, rice crackers, biscuits, dried noodles, cookies, and other foods. It is used by installing in display windows, empty houses, villas, museums, museums, etc., closets, closets, cupboards, shoe boxes, pianos, under floors, ceilings, etc. Has been.

  The food is often affected by the presence of a small amount of water, and the presence of such a small amount of water immediately causes a change in quality or a decrease in quality, or a decrease in taste or texture. Also, due to the presence of moisture, mold, bacteria, etc. are generated and propagated in the food, the contents in the closet, the exhibits, the floor, the back of the ceiling, etc., which is not preferable from the viewpoint of hygiene, health and environment. .

  Examples of desiccants having such uses include deliquescent inorganic salts such as calcium chloride, magnesium chloride, and aluminum chloride; water retention products such as kaolin, bentonite, zeolite, starch, carboxymethylcellulose, and sodium acrylate-acrylamide copolymer; And the desiccant which consists of hydrated hardened | cured materials, such as calcium silicate, hydraulic cement, hydraulic lime, gypsum, is proposed (refer patent document 1).

  Examples of the starch used in such a desiccant include modified starch (modified starch) such as pregelatinized starch, crosslinked starch, esterified starch, and etherified starch, and roasted dextrin, enzyme-modified dextrin, A starch decomposition product such as acid-decomposing dextrin is known (see Patent Document 2).

  Furthermore, a technique using two or more kinds of starches in combination with calcium chloride is also known. For example, it contains oxidized starch, enzyme-converted starch, and functional groups such as hydroxyl group, carbonyl group and amino group. A desiccant comprising a starch composition in which two or more kinds of modified starch are mixed and calcium chloride is known (see Patent Document 3).

  Such a desiccant is usually used in a state of being stored in a packaging container. However, a necessary property as a desiccant used in such a state is that a moisture absorbent such as calcium chloride absorbs moisture. The water retention ability of the water retention agent for retaining the water (calcium chloride aqueous solution) generated by the water, the gelation capability of the retained water retention agent, the ability to prevent water separation from the retained water retention agent, and the like.

In other words, if the moisture absorbent absorbs moisture in the air and liquefies, or once the water retained in the water retention agent etc. is removed and liquefied, the packaging container is damaged. In order to cause liquid leakage in the container and cause contamination, contamination, rusting, etc. of the cargo in the container and the food around the desiccant, the entire amount of water generated by moisture absorption by the moisture absorbent is absorbed by the water retention agent, It is necessary to make the gel and prevent water separation.
Japanese Examined Patent Publication No. 62-30815 Japanese Patent No. 3327983 Japanese Patent Laid-Open No. 10-99632

  However, in the above Patent Documents 1 to 3, as starch contained in the desiccant, modified starch (processed starch) such as pregelatinized starch, cross-linked starch, esterified starch and etherified starch, and starch degradation products are disclosed. Although dextrin and the like are disclosed, these starches are more expensive than non-gelatinized starches, and there is a problem that the production of the desiccant is costly.

  On the other hand, ungelatinized starch is inexpensive in price, but has a low water absorption capacity compared to other modified starches (processed starches), so in order to prevent liquid leakage from the desiccant, There is a problem that it is necessary to reduce the content of the deliquescent material such as calcium chloride contained in the desiccant together with starch in the desiccant and increase the content of starch, which is not suitable as a raw material for the desiccant. Needless to say, in recent years, it has been preferable to use ungelatinized starch having a low energy cost as a raw material for the desiccant in a situation where the problem of global warming becomes serious.

  Accordingly, an object of the present invention is to provide a desiccant that is excellent in water absorption capability and hardly leaks and is inexpensive.

  In order to solve the above problems, the present inventors have intensively studied to use inexpensive starch as a desiccant, and as a result, found that the water absorption ability of waxy starch is superior to other starches, The present invention has been completed.

That is, the present invention provides a drying agent characterized in that it contains calcium chloride, a waxy starch and α starch (invention 1). According to this invention ( Invention 1), calcium chloride absorbs water present in the environment around the desiccant, and the calcium chloride aqueous solution produced thereby absorbs water with a high water absorption capacity and low cost waxy starch. Therefore, it is possible to obtain a desiccant that is excellent in water absorption capability and hardly leaks and that is low in cost. Waxy starch is less than room temperature (about 10 to 30 ° C.) and hardly absorbs calcium chloride aqueous solution having a predetermined concentration (about 42%) or more, but pregelatinized starch is less than room temperature and has a predetermined level. Even a calcium chloride aqueous solution of a concentration or higher absorbs water. In the initial stage of water absorption by calcium chloride, it is considered that a high concentration calcium chloride aqueous solution is generated and the concentration decreases with time. Therefore, according to this invention, in the initial stage of water absorption by calcium chloride, the pregelatinized starch absorbs a calcium chloride aqueous solution having a predetermined concentration or higher, and then the waxy starch absorbs the calcium chloride aqueous solution having a predetermined concentration or lower. Therefore, even in the initial stage of water absorption (moisture absorption) by calcium chloride, water can be absorbed and gelled, and a desiccant that hardly causes liquid leakage can be obtained.

In the said invention ( invention 1), it is preferable that the said waxy starch is ungelatinized waxy starch ( invention 2). Since non-gelatinized waxy starch is available at low cost, according to this invention ( Invention 2), the waxy starch is non-gelatinized so that it can be made a lower cost desiccant.

In the above invention (inventions 21 to), at least the waxy starch is preferably a starch glutinous corn origin (invention 3). According to this invention ( Invention 3 ), waxy starch derived from glutinous seeds and corn has an excellent water absorption capability among waxy starches, so that it can be a desiccant with higher water absorption capability and less liquid leakage.

In the said invention ( invention 1-3 ), it is preferable that the mixture ratio of the said waxy starch and the said pregelatinized starch is 8: 2-2: 8 ( invention 4 ). According to this invention ( invention 4 ), if the blending ratio of waxy starch and pregelatinized starch is within the above range, it has excellent water absorption ability and excellent gelling ability, so that it is more difficult to cause liquid leakage. It can be used as an agent.

In the said invention ( invention 1-4 ), it is preferable to contain a highly water-absorbing resin further ( invention 5 ). According to this invention ( invention 5 ), it can be set as the desiccant which is more excellent in water absorption capability and is hard to produce a liquid leak by further containing superabsorbent resin.

  According to the present invention, it is possible to provide a desiccant that is excellent in water absorption capability and hardly leaks and is inexpensive.

Hereinafter, the desiccant which concerns on one Embodiment of this invention is demonstrated.
The desiccant according to the present embodiment contains calcium chloride and waxy starch.

  The shape of calcium chloride is not particularly limited, and for example, it may be fine powder, fine powder, coarse powder, granular or granular, and its particle size is not particularly limited. However, it is preferable that the particle size is smaller because the surface area of calcium chloride can be increased and the water absorption rate by calcium chloride can be improved.

  Waxy starch refers to glutinous starch whose amount of amylopectin contained in the starch is almost 100%, such as glutinous rice starch, waxy potato starch, and glutinous corn (waxy corn) starch. The waxy starch in the present embodiment is preferably starch derived from glutinous seeds and corn (glutinous seeds and corn starch) from the viewpoints of supply capacity and price.

  The waxy starch may be non-gelatinized (that is, the starch granules are not substantially damaged and maintain a healthy non-gelatinized state). Processed starch such as waxy adipic acid cross-linked acetylated starch, waxy phosphoric acid cross-linked starch, waxy cationized starch or the like obtained by processing waxy starch may be used, but ungelatinized waxy starch is preferred. Ungelatinized waxy starch is superior in water absorption capacity to other starches and is available at a lower cost than modified starch (modified starch), etc., thus reducing the manufacturing cost of desiccant Can do.

  The desiccant according to this embodiment preferably further contains pregelatinized starch. Calcium chloride absorbs moisture in the air to produce a high-concentration calcium chloride aqueous solution. It is considered that the concentration of the aqueous solution gradually decreases as the water absorption proceeds. Here, ungelatinized waxy starch has a higher water absorption capacity than other starches, and absorbs water at room temperature if it is in a predetermined concentration of calcium chloride aqueous solution. It is difficult to absorb water at a concentration. On the other hand, pregelatinized starch is inferior in water absorption capacity to ungelatinized waxy starch, but can absorb water even in a calcium chloride aqueous solution having a concentration equal to or higher than a predetermined concentration. Therefore, such a desiccant contains pregelatinized starch, and in the initial stage when calcium chloride starts to absorb water in the air, pregelatinized starch absorbs the high-concentration calcium chloride aqueous solution generated thereby. In addition, since the non-gelatinized waxy starch can absorb the calcium chloride aqueous solution reduced to a predetermined concentration, it can be used in a wide temperature range (for example, 10 to 70 ° C.) and has a high water absorption capability. It can be set as the desiccant which does not produce a liquid leak easily.

  In the present embodiment, pregelatinized starch refers to processed starch obtained by rapidly drying non-gelatinized starch that has been gelatinized by adding water and heating. Examples of the raw material for such pregelatinized starch include ungelatinized starch separated from potato, wheat, rice, corn, sweet potato, cassava, kudzu, katakuri, broad bean, mung bean, red bean and the like. Of these raw materials, the pregelatinized starch in the present embodiment is preferably pregelatinized starch obtained from starch derived from glutinous corn. In addition, the pregelatinized starch in this embodiment may be obtained by further performing processing such as esterification, etherification, and crosslinking on the pregelatinized starch.

  In the desiccant according to the present embodiment, when waxy starch and pregelatinized starch are included, the blending ratio thereof is not particularly limited, but is preferably 8: 2 to 2: 8. : 4 to 2: 8 is more preferable, and from the viewpoint of production cost, it is preferable to increase the blending amount of waxy starch rather than pregelatinized starch. If the blending ratio of waxy starch exceeds 8 and the blending ratio of pregelatinized starch is less than 2, the aqueous calcium chloride solution produced in the initial stage of water absorption by calcium chloride may not be effectively absorbed or gelled. When the blending ratio of waxy starch is less than 2 and the blending ratio of pregelatinized starch exceeds 8, the blending amount of waxy starch decreases, and the calcium chloride aqueous solution generated by the absorption of calcium chloride is sufficiently absorbed and gelled. It may not be possible.

  The desiccant according to this embodiment may further contain a superabsorbent resin. Thereby, it is possible to further increase the water absorption capacity and prevent liquid leakage. Examples of the highly water-absorbing resin include polyacrylamide polymers, cellulose carboxymethylcellulose sodium salts, polyvinyl alcohol polymers, and the like, but it is preferable to use polyacrylamide polymers.

  Examples of polyacrylamide polymers include cationic monomers (methacrylic acid ester derivatives such as dialkylaminoethyl (meth) acrylate and dialkylaminopropyl (meth) acrylate); dialkylaminopropyl (meth) acrylamide, dialkylaminopropyl (meta ) Acrylamide, (meth) acrylamide derivatives such as (meth) acrylamide-3-methylbutyldimethylamine), anionic monomers (acrylic acid, methacrylic acid, crotonic acid, allyl carboxylic acid, methallyl carboxylic acid, itaconic acid, malein Acid, fumaric acid, phthalic acid, citraconic acid, etc.), sulfonic acid monomer (allyl sulfonic acid, methallyl sulfonic acid, vinyl sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane) Sulfonic acid etc.), phosphonic acid monomer (vinyl phosphonic acid, α-phenylphosphonic acid, 1-butene-2-phosphonic acid, isopropenylphosphonic acid etc.) and nonionic monomer ((meth) acrylamide, N, N-dimethylacrylamide) Etc.), and a polymer obtained by one or more copolymerization reactions selected from the above.

  The blending ratio of calcium chloride, waxy starch, pregelatinized starch, and superabsorbent resin in the desiccant according to the present embodiment is not particularly limited, and is based on conditions such as humidity and moisture content in the use environment of the desiccant. What is necessary is just to change suitably according to it.

  The method for producing waxy starch in the present embodiment is not particularly limited, and may be produced using conventional wet milling technology using glutinous seeds and corn as raw materials. Moreover, the manufacturing method of the pregelatinized starch in this embodiment is not specifically limited, What is necessary is just to manufacture using the conventional technique.

  The desiccant according to this embodiment is a mixture of calcium chloride and waxy starch (preferably ungelatinized waxy starch), preferably pregelatinized starch, and more preferably a superabsorbent resin. Can be housed in a packaging material made of a film having water vapor permeability (breathability) and water impermeability, sealed by heat fusion, etc., and used as a desiccant package.

  As a film having water vapor permeability and water impermeability, for example, a unitary film formed from a polyolefin-based material such as polyethylene, polypropylene, polyfluorinated ethylene, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, etc. Although a microporous film, a urethane film, etc. are mentioned, it is not limited to these.

  Since the desiccant according to this embodiment described above contains waxy starch, it can effectively absorb and gel the aqueous calcium chloride solution generated by water absorption in the air by calcium chloride. In addition to obtaining a desiccant having a high water absorption capacity, liquid leakage from the desiccant can be effectively prevented. Further, by further containing pregelatinized starch, it is possible to immediately absorb the calcium chloride aqueous solution generated in the initial stage of water absorption by the calcium chloride aqueous solution, so that it is possible to further increase the water absorption capacity, and from the desiccant. Liquid leakage can be further prevented.

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  The present invention will be described in more detail with reference to the following test examples, but the present invention is not limited to the following test examples.

[Water absorption capacity evaluation test]
50 g of 37.5 mass% calcium chloride aqueous solution was added to 1 g of each sample shown in Table 1 below (various starches, various superabsorbent resins and sepiolite, samples 1 to 15), and left for 40 hours with occasional stirring at 23 ° C. Centrifugation was performed to collect precipitates (starch, superabsorbent resin, sepiolite). The mass of the collected precipitate was measured, and the amount of water absorption per 1 g of sample was calculated.
The results are shown in Table 2.

  As shown in Table 2, ungelatinized waxy corn starch (sample 1) has a water absorption of 50.0 g or more, and a water absorption of about 3 to 33 times that of other non-waxy starch (samples 3 to 11). In addition, waxy crosslinked corn starch (sample 1) showed a water absorption of about 2.5 to 28 times that of other non-waxy starches (samples 3 to 11). As a result, it was confirmed that the waxy starch had an excellent water absorption capability compared to other starches, and the non-gelatinized waxy starch was confirmed to have a particularly excellent water absorption capability. Moreover, it was confirmed that the non-gelatinized waxy corn starch (sample 1) has a water absorption capability equivalent to that of polyacrylamide (PAM, sample 12) having the most excellent water absorption capability among the superabsorbent resins.

[Evaluation test of water absorption capacity of ungelatinized waxy starch]
It is known that ungelatinized starch is gelatinized at room temperature in a calcium chloride aqueous solution in a predetermined concentration range. On the other hand, calcium chloride absorbs moisture in the air to produce a high-concentration calcium chloride aqueous solution, but it is considered that the concentration decreases with time as water absorption proceeds. Therefore, if calcium chloride powder and ungelatinized starch are mixed and exposed to the air, the starch will gelatinize when the high-concentration aqueous solution formed by moisture absorption of calcium chloride reaches the prescribed concentration. Will do. That is, the starch begins to absorb water at this point. Therefore, the concentration of the aqueous solution of calcium chloride at which the ungelatinized waxy corn starch (sample 1 shown in Table 1) starts to absorb water at room temperature was examined by the following method.

  Distilled water was added to anhydrous calcium chloride to prepare calcium chloride aqueous solutions with various solid concentrations, and the solution was cooled to 5 ° C. in an ice water bath. To this, ungelatinized waxy corn starch was suspended so that the solid content concentration was 6% by mass, and Rapid Visco-Analyzer (manufactured by Newport Scientific Pty. Ltd., product name: Model RVA-4) was used. The pasting behavior was measured. The measurement conditions were a heating rate of 12 ° C./min, heating with stirring (160 rpm), measuring the temperature at which the viscosity began to rise, and this temperature was defined as the gelatinization temperature. A graph showing the relationship between the calcium chloride concentration and the gelatinization temperature is shown in FIG.

  As shown in FIG. 1, at normal temperature (30 ° C. or lower), it was confirmed that ungelatinized waxy corn starch does not gelatinize and does not absorb water unless the concentration of calcium chloride is reduced to about 42% or less. .

  From this, at the initial stage of water absorption by calcium chloride, which is considered to have a calcium chloride concentration exceeding 42%, it is difficult to absorb and gel the aqueous calcium chloride solution only with ungelatinized waxy corn starch. It is considered that it is preferable to use a pregelatinized starch or PAM that exhibits excellent water absorption ability even in a low temperature range (about 10 to 30 ° C.) and a high calcium chloride concentration.

  Therefore, a desiccant consisting of calcium chloride, ungelatinized waxy corn starch, pregelatinized starch and / or PAM absorbs calcium chloride aqueous solution immediately after water absorption by calcium chloride in the temperature range of 10 to 70 ° C. It is thought that it can be gelled.

[Drying agent fluidity evaluation test]
A desiccant prepared by mixing calcium chloride, ungelatinized waxy corn starch (Sample 1 shown in Table 1), and pregelatinized corn starch (Sample 3 shown in Table 1) at the mixing ratio shown in Table 3 Examples 1 to 11 and Comparative Examples 1 and 2) were placed in a thermo-hygrostat controlled at 40 ° C. and a relative humidity of about 70%, and water (calcium chloride aqueous solution) generated by moisture absorption of calcium chloride was used. The flow state of the absorbed starch (samples 1 and 3) was visually observed, and the flowability of the desiccant (Examples 1 to 11 and Comparative Examples 1 and 2) was evaluated in five stages according to the criteria shown in Table 4 below. .
The results are shown in Table 5.

  As shown in Table 5, it was confirmed that the desiccant of Examples 1 to 11 blended with waxy starch was able to absorb calcium chloride aqueous solution as compared with the desiccant of Comparative Example 1 not blended with waxy starch. It was done.

  In addition, the desiccant of Examples 2 to 5 has a low fluidity from the initial stage of the start of use after 5 hours to 1 day from the start of use and also has a low flowability after 4 to 13 days from the start of use. If the blending ratio with the pregelatinized starch is within the range of 8: 2 to 2: 8, the pregelatinized starch absorbs the calcium chloride aqueous solution at the initial stage of use, and then the waxy starch absorbs water. It was confirmed that liquid leakage from the desiccant could be prevented.

  In addition, although the desiccant of Comparative Example 2 containing no waxy starch has a relatively good flow state, as shown in Table 2 above, the pregelatinized starch has a water absorption capacity of less than 1/3 of the waxy starch. Therefore, it is considered that there is a possibility that the whole amount of the calcium chloride aqueous solution cannot be absorbed when it is used under conditions of higher humidity than the test.

  In this way, by combining waxy starch and pregelatinized starch and / or PAM, the mixture absorbs the entire amount of water (calcium chloride aqueous solution) generated by water absorption by calcium chloride and gels. it can. Water (calcium chloride aqueous solution) produced in the initial stage of moisture absorption of calcium chloride is absorbed by gelatinized starch and / or PAM and gelled, and the water produced thereafter (calcium chloride aqueous solution) has a high water absorption capacity. Waxy starch having a water content can be absorbed and gelled. Therefore, it can be set as the desiccant which has a high water absorption capability and hardly causes liquid leakage.

  The desiccant of the present invention is useful for drying and dehumidifying the surrounding environment of a cargo such as a container in which cargo such as electronic parts, precision machines, machine tools, and industrial machines is loaded.

It is a graph which shows the relationship between the density | concentration of calcium chloride aqueous solution, and the gelatinization temperature of waxy corn starch.

Claims (5)

Drying agent characterized by containing calcium chloride, the waxy starch and α starch.   The desiccant according to claim 1, wherein the waxy starch is a non-gelatinized waxy starch. The desiccant according to claim 1 or 2, wherein at least the waxy starch is a starch derived from glutinous seeds and corn. The desiccant according to any one of claims 1 to 3, wherein a mixing ratio of the waxy starch and the pregelatinized starch is 8: 2 to 2: 8. Drying agent according to any one of claims 1 to 4, characterized in that further contains a super absorbent polymer.

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