JP2001314758A - Drying agent and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drying agent containing, calcium oxide, as an effective component which has sufficient performance and is hardly pulverized and scattered, and to provide a method of producing the same. SOLUTION: The drying agent contains >70 and <=90 wt.% powdery calcium oxide and >=10 and <30 soft resin. The drying agent is produced by dispersing calcium oxide in a solution in which the soft resin is dissolved and drying/ solidifying the resulting solution by removing the solvent, or by mixing calcium oxide with the soft resin melted by heat in a blending device free from a dead spot to disperse the calcium oxide into the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a desiccant, and more specifically, to enhance safety by substantially preventing powder from being dispersed from a calcium oxide desiccant, and to be applicable as a desiccant in various fields. And a method for producing the same.

[0002]

2. Description of the Related Art Generally, silica gel, calcium chloride, calcium oxide and the like are widely used as desiccants and dehumidifiers. Silica gel is generally in the form of granules, and the granules are used in appropriate containers or used by being wrapped in a breathable packaging material. Calcium chloride as a dehumidifying agent is contained in a container, and the upper part of the container is covered with a breathable sheet so as to absorb water and prevent calcium chloride in an aqueous solution from leaking. Calcium oxide is usually used by wrapping granules in air-permeable wrapping paper with enhanced tear strength so that powdered ones after moisture absorption are not scattered. Also, Japanese Patent Application Laid-Open No. 5-227
No. 930 proposes a sheet-shaped desiccant comprising 20 to 70% by weight of calcium oxide and 80 to 30% by weight of a polymer.

[0003]

Calcium oxide is generally produced by calcining limestone, and is widely used as a desiccant because it is produced in large quantities.
Compared to other desiccants, it has a high ability to absorb moisture at low humidity and is widely used in the food field. Calcium oxide is usually made by laminating with tape or film to give a breathable wrapping paper with high tear strength.
g, 10 g and larger are treated as desiccants packaged in units of 100 g or more. Such a calcium oxide desiccant is used together with food in a bag for packaging food, and is used in particular for rice confectionery, dried seaweed,
Widely used for nuts, cookies, delicacies, tea and dry matter.

[0004] These foods have a low edible moisture limit, and are susceptible to product deterioration caused by water, that is, microbial deterioration, physical deterioration, and chemical deterioration. In order to prevent such an adverse change, a calcium oxide desiccant having a high hygroscopic ability at low humidity is used. The packaged calcium oxide desiccant is enclosed with the food packaging bag until the food is lined up at the store after packaging, absorbs the moisture permeating through the food packaging bag, and acts to keep the food moisture low. After opening the food packaging bag, the moisture in the air is sucked in, and many parts are changed to calcium hydroxide.

[0005] After use, the calcium oxide desiccant is discarded in a packaged state. However, in rare cases where the package is broken or cut by force majeure, calcium oxide is granules or powder, and those converted to calcium hydroxide are more fine powder, so they are easily scattered, and Dangerous. In fact, it cannot be denied that food manufacturers have inquiries from consumers who have purchased food for responding to accidental ingestion of desiccants.

[0006] In particular, when calcium oxide is changed to calcium hydroxide, powdering occurs with volume expansion and the shape of calcium oxide does not remain. Calcium oxide must be firmly packaged to avoid splashing. However, when wrapped in sturdy wrapping paper, the dimensions are large and the weight is heavy, so that it has been difficult to apply it to applications such as medicines where the object to be dried is small. In addition, the actual use has been limited in that it cannot be used as a desiccant for precision equipment or the like that dislikes dust at all.

As a solution to the problem of safety, Japanese Patent Application Laid-Open No. Hei 5-227930 proposes a calcium oxide polymer sheet. The polymer sheet is manufactured by melt-kneading calcium oxide and thermoplastic polymer,
It contains 20% by weight or more and 70% by weight or less of calcium oxide. This polymer sheet is a desiccant that generates excessive heat upon water injection and does not cause the user to suffer burns or fire, and if the amount of calcium oxide is more than 70% by weight, continuous It is described that it cannot be made into a sheet. This desiccant has a small amount of calcium oxide and therefore has a small amount of moisture absorption.Although the ratio of calcium oxide is small due to the use of a hard resin, it loses refuge when calcium oxide changes to slaked lime and powders. Is easy to occur.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a desiccant containing calcium oxide as an active ingredient, which does not cause powdering or scattering while maintaining a sufficient moisture absorbing performance as a desiccant, and a method for producing the same. Is to provide.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for preparing calcium oxide 70 in granular or powder form.
The drying agent was configured such that ９０90 parts by weight (excluding 70) was dispersed in 30 to 10 parts by weight (excluding 30) of the soft resin.

The present invention also provides a method of dispersing a granular or powdery calcium oxide in a solution in which a soft resin is dissolved,
Alternatively, calcium oxide is mixed and dispersed in a soft resin having a melt flow rate of preferably 10 or more in a hot melt state in a blending apparatus in which substantially no dead space is generated, and then solidified to form a film, a sheet, a chip, The composition was formed into various shapes such as a tablet to form a desiccant manufacturing method.

In the present invention, calcium oxide granules or powders are dispersed in a soft resin, bound by the soft resin, and when the calcium hydroxide is changed to calcium hydroxide, it is prevented from expanding and powdering by covering with the soft resin. Thus, the scattering of the calcium oxide desiccant is prevented. This desiccant can prevent the calcium oxide desiccant from scattering even though the proportion of calcium oxide is extremely large, and also maintains the moisture absorbing performance as the desiccant. The manufacture of this desiccant is
One is to dissolve a soft resin in a solvent, disperse calcium oxide in the solution, and remove the solvent from the solution by drying and solidification. It is also possible by dispersing calcium oxide in the form and then solidifying it.

As the calcium oxide contained in the desiccant according to the present invention, generally, crushed stone obtained by calcining limestone is pulverized, and mainly calcium oxide having a large particle diameter of 1000 μm or less, preferably large. Part is 100 μm
The following powder is used.

The desiccant according to the present invention comprises 70 to 90 parts by weight (excluding 70) of powdery or granular calcium oxide.
And 30 to 10 parts by weight (excluding 30) of the soft resin. In the desiccant, the calcium oxide powder is dispersed and bound in the soft resin, and is prevented from expanding and powdering when the calcium oxide is changed to calcium hydroxide by covering with the soft resin. 7 calcium oxide in desiccant
If the amount is less than 0 parts by weight, the moisture absorption capacity is reduced, and if the amount of the soft resin is less than 10 parts by weight, the prevention of powdering is not sufficient. In consideration of the moisture absorbing ability, preferably, calcium oxide is 75 to 90 parts by weight, and the soft resin is 25 to 10 parts by weight.

The soft resin contained in the desiccant according to the present invention refers to a resin having a breaking strength at room temperature of 50 MPa or less, preferably 25 MPa or less.
The resin has a MPa or less and a breaking elongation of 200% or more, preferably 500% or more, but is not limited thereto. In this case, another resin may be present in the soft resin at, for example, 20% or less. Examples of the soft resin herein include rubber-like resins such as unvulcanized rubber and thermoplastic elastomer, and thermoplastic resins. These are, for example, natural rubber, polybutadiene, polychloroprene, styrene-butadiene copolymer, styrene-isoprene copolymer, butyl rubber, nitrile rubber, isoprene rubber, ethylene propylene rubber, urethane rubber, acrylic rubber, ethylene-butene copolymer, It is a polyurethane elastomer, an ionomer, an ethylene ethyl acrylate copolymer, an ethylene vinyl acetate copolymer, polyethylene, polypropylene, a copolyester, or the like, or a mixture thereof. The composition ratio, molecular weight, viscosity, etc. of the soft resin used here are not limited,
It can be appropriately selected according to the use and the like.

Other resins that may be contained in these soft resins, ie, hard resins, include aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, aromatic hydrocarbon resins, polyterpene resins, and cumarone. -Indene resin, petroleum resin, rosin, styrene resin, low molecular weight olefin resin and the like.

The ratio of the soft resin to the other resin in the desiccant according to the present invention is preferably such that the soft resin is 80% by weight or more, and if the soft resin is less than 80% by weight, calcium oxide is changed to calcium hydroxide. In this case, the effect of preventing powdering is reduced.

In the method for producing a desiccant according to the present invention, when calcium oxide and a soft resin are mixed and dispersed with each other, 1
One is to dissolve a soft resin in a solvent and mix them. That is, granular or powdered calcium oxide 7
0 to 90 parts by weight (excluding 70) of soft resin 30 to 10
Dispersed in parts by weight (excluding 10) of the dissolved solution,
It consists of each process of drying and solidifying. The solvent used is not particularly limited as long as the solvent dissolves the soft resin,
For example, acetone, isopropyl alcohol, ethyl acetate, butyl acetate, methyl ethyl ketone,
An aliphatic solvent such as MIBK, normal hexane, cyclohexane, toluene, and xylene, an alicyclic solvent, an aromatic solvent, or a mixed solvent thereof can be selected. Some soft resins are commercially available in the form of a solution, and these can also be used. Another method for producing a desiccant is preferably a blending apparatus in which a soft resin having a melt flow rate of 10 or more does not substantially generate a dead space, for example, in a blending apparatus having good mixing properties such as a co-kneader, a pressure kneader, and a roll. Then, 70 to 90 parts by weight (excluding 70) of granular or powdery calcium oxide and 30 to 10 parts by weight (excluding 10) of the soft resin are heated and melted, and, for example, apparently no aggregation of calcium oxide is found. By sufficiently mixing and dispersing. If the melt flow rate of the soft resin is less than 10, the mixing property at the time of melting is poor and uniform dispersion is difficult, and powdering tends to occur after moisture absorption. Further, in a blending apparatus in which a dead spot such as stagnation generated behind the stirring blade occurs, the two are not sufficiently confused and dispersed. The soft resin and the calcium oxide may be housed together in a blending apparatus in a dry state at room temperature and heating and mixing may be started, or the calcium oxide may be gradually added to the blending apparatus containing the soft resin in a molten state. To mix the two.

Although the shape of the desiccant according to the present invention is not limited, it is preferable that the desiccant be formed into a plate-like molded product, a sheet-like material, a tablet-like shape, a disk-like shape, or the like for handling. The desiccant according to the present invention, in the case of a production method of dissolving a soft resin in a solvent, disperse the calcium oxide in the solution by mixing the soft resin and calcium oxide dissolved in the solvent in a dissolution tank equipped with a stirrer. . At this time, a stirrer having various stirring blades such as a paddle, a ribbon, a helical, a propeller, and a screw is appropriately used. A kneader or a twin screw mixer is also effective as an efficient solid-liquid mixer. After mixing, the mixed solution is applied onto a support such as a film, a sheet, or a nonwoven fabric by a roll coater, a doctor knife coater, an applicator, or the like, for example, by 0.5 mm.
It is made into a sheet with a thickness of about 5 mm and dried and solidified. The film may be made of polypropylene or polyester, the sheet may be paper, coated paper, or release paper, and the non-woven fabric may be made of polypropylene, polyester, or other fibers. These supports can be used as carrier sheets only in the production process, or can be used as a laminate integrally with a desiccant. In this case, it is preferable to use a support having air permeability or a processed support having improved air permeability. Drying and solidification are performed by guiding the sheet to a hot air drying zone to dry and remove the solvent. On the other hand, in the case of a method in which a desiccant is mixed and dispersed in a hot-melt state, the mixture is sufficiently mixed and dispersed by a co-kneader or a pressure kneader without dead spots, and then formed into a sheet by a roll or pelletized by an extruder. And coarsening with a crusher, and then forming as appropriate. The sheet desiccant is fed into a chip cutter provided with a cutter that slits the desiccant at a constant width and a cutter that moves up and down at a constant interval at an arbitrary speed, and cuts it into chips, or cuts it into an appropriate shape by a punching machine.

In the desiccant according to the present invention, most of the calcium oxide is covered with a soft resin,
Contact moisture absorption with moisture through soft resin. Calcium oxide changes to calcium hydroxide and expands in volume, but the soft resin has an elongation enough to cope with the expansion, so that calcium hydroxide dust does not scatter.

Although the desiccant according to the present invention has little risk of powdering, it is preferable to wrap it in a simple air-permeable wrapping paper and use it in consideration of contact with foods and the like. . Examples of the air-permeable simple wrapping paper include Japanese paper, nonwoven fabric, and a film having fine pores. In the moisture absorption test of the following examples, test data was collected in an unpackaged state.

[0021]

As described above, according to the desiccant and the method for producing the same according to the present invention, calcium oxide or calcium hydroxide powder is prevented from scattering while sufficiently maintaining the performance as a desiccant, thereby improving safety. Therefore, it is possible to obtain a desiccant which is easier to handle than before and can be applied to various fields.

[0022]

(Example 1) 30 parts by weight of chloroprene rubber, 70 parts by weight of a mixed solvent of normal hexane, cyclohexane, isopropyl acetate and acetone (Konishi Co., Bond G17), and 100 parts by weight of powdered calcium oxide of 200 μm or less The mixture was stirred and mixed, and applied on release paper, and then dried and solidified to a thickness of 3 mm. Calcium oxide is coarsely crushed with a crusher and then 0.5m into a cross beater mill.
A screen having a size of m was set and pulverized, and classified and used at 200 mesh. The ratio of calcium oxide to rubbery resin was 77 parts by weight: 23 parts by weight.

Measurement of hygroscopicity: A laminate of 5 g of the desiccant of Example 1 was cut and kept at 25 ° C. in a desiccator adjusted to 50% relative humidity with sulfuric acid. After 7 days, the amount of hygroscopicity was measured. Rate was 25 wt%. The value of the moisture absorption is
The ratio of the amount of water absorbed and increased with respect to the desiccant (calcium oxide + resin) was expressed in weight percent.

Powdering property: The sample after measuring the hygroscopicity was rubbed against a black backing sheet to observe the presence or absence of dust. The powdery substance was not recognized.

(Example 2) Solid content 6.7 wt%, solvent 9
200 parts by weight of 3.3 wt% of natural rubber paste (Maruni Kogyo, n-hexane and other solvents) and 100 parts by weight of powdered calcium oxide of 200 μm or less are mixed, and the resin solution is 3 mm thick on a polypropylene nonwoven fabric. Was coated with an applicator and dried with hot air. The produced desiccant is in a state of being laminated on a nonwoven fabric, and calcium oxide and a rubber-like resin
8 parts by weight: 12 parts by weight. This product had a moisture absorption of 25%, and powdering was not observed.

Example 3 18 parts by weight of a styrene-isoprene copolymer resin (SIS5505 manufactured by JSR) and 2 parts by weight of a petroleum resin (High Resin # 90 manufactured by Toto Chemical Co.) were dissolved in 80 parts by weight of toluene. Was mixed with 80 parts by weight of powdered calcium oxide having a particle size of 500 μm or less, and a 5 mm-thick sheet was formed on a polypropylene film with an applicator using the solution, followed by hot-air drying. This product had a moisture absorption of 19%, and powdering was not observed.

Example 4 Ethylene ethyl acrylate copolymer resin (NUC Copolymer 657 manufactured by Nippon Unicar Co., Ltd.)
0, melt flow rate 20) 25 parts by weight and 100 mesh or less of calcium oxide at a temperature of 150 ° C. to 220 ° C.
Was mixed and dispersed with a coneder (PCM, manufactured by Ikegai Iron Works Co., Ltd.), solidified by a cooling roll, and subsequently cut into an irregular shape. A rectangular desiccant chip was obtained from the irregular-shaped cut product using a 140 ° C. hot press. The moisture absorption of this chip is 23%
And no pulverization was observed. Here, the melt flow rate is a value expressed by an amount flowing out from an orifice having an inner diameter of 2 mm and a length of 8 mm at a predetermined load and a predetermined temperature in 10 minutes according to JIS K6760. The values listed in the Plastic Molding Material Commerce Handbook (Chemical Industry Daily) are used.

Example 5 10 parts by weight of an ethylene-vinyl acetate copolymer resin (manufactured by Sumitomo Chemical Co., Ltd., Evatate D5020, melt flow rate 75) was pressed into a pressure kneader (manufactured by Moriyama Seisakusho Co., Ltd.).
Into a test machine) and melted at 180 ° C., and 90 parts by weight of calcium oxide having a mesh size of 200 mesh or less were gradually added and sufficiently kneaded. This was passed through two rolls, formed into a sheet, and then cut into chips. This product had a moisture absorption of 28%, and powdering was not observed.

Comparative Example 1 20 parts by weight of natural rubber having a Mooney viscosity of about 80 and calcium oxide of 500 μm or less
In producing the parts by weight, first, natural rubber was charged into a Banbury mixer, and after stirring was started, calcium oxide was gradually added and mixed. At room temperature, it is not easy to obtain a completely kneaded product, but one having an apparently uniform shape was formed into a 2 mm thick sheet with two rolls. Although the moisture absorption of this product was as good as 25%, powdering was severe and fine powder was scattered.

(Comparative Example 2) Biaxial blending of a dry blend of 35 parts by weight of 6 nylon 6 (Tanadine TN200, melt flow rate 12 manufactured by Takayasu Co., Ltd.) and 65 parts of calcium oxide of 50 μm or less was performed at a melting zone of 250 ° C. The mixture was charged into a kneading extruder hopper, extruded into a 3 mm sheet with a press roll set at the exit of the extruder, cut, and then subjected to moisture absorption measurement. The moisture absorption of this product was as good as 20%, probably because of the water absorption of 66 nylon, but powdering was recognized.

Comparative Example 3 Polypropylene (manufactured by Idemitsu Co., Ltd.)
E-203GK, melt flow rate 2.5) A dry blend of 75 parts by weight to 25 parts by weight of calcium oxide of 200 μm or less was melted at a melting temperature of 230 ° C. in the same manner as in Example 2, and extruded into a 2 mm sheet. Then, the hygroscopicity of the cut product was measured. No powdering was observed, but the moisture absorption was as poor as 2%.

(Comparative Example 4) In Example 5, 94 parts by weight of ethylene oxide copolymer resin calcium oxide was kneaded in the same manner to obtain a sheet-like chip. Although the moisture absorption was 29%, powdering after moisture absorption was observed.

(Comparative Example 5) In Example 4, ethylene ethyl acrylate was used with a melt flow rate of 1 (Mitsui
It was manufactured in the same manner as above except that A719 was manufactured by DuPont Chemical. Although the moisture absorption was 23%, it was not uniformly dispersed, and powdering was observed after moisture absorption.

(Comparative Example 6) The kneading time was shortened under the same conditions as in Example 4, and irregular shaped chips were formed in a state where particles of calcium oxide powder were observed. It was formed into a sheet. This product had a moisture absorption of 23%, but powdering was observed from a part of the surface of the desiccant.

(Comparative Example 7) The same procedure was carried out using polystyrene (G100, melt flow rate 24, manufactured by Toyo Styrene Co.) as a hard resin in place of the ethylene-ethyl acrylate copolymer resin of Example 4. When the moisture absorption of the obtained chip was measured, it was 18%. Powdering was also observed.

Comparative Example 8 25 parts by weight of the ethylene-ethyl acrylate copolymer resin of Example 4 was melted at 180 ° C. by using a kneader having a U-shaped mixing shaft for mixing a general solution. Calcium oxide of 100 mesh or less was gradually added to and mixed. This was formed into a sheet with two rolls, and the hygroscopicity and the powdering property were observed. In this kneader, dead spots were easily formed on the back side of the U-shape axis, and there were places where calcium oxide was aggregated, and powdering was observed after moisture absorption. The moisture absorption was 23%.

[0037]

[Table 1]

Table 2 shows the values of the breaking strength and the breaking elongation of the resins used in the examples and comparative examples. These measuring methods followed JIS K-7113 "Plastic tensile test method". Autograph conditions Tensile speed 100 mm / min, ambient temperature 25 ° C Test piece: Dumbbell 2

[0039]

[Table 2]

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D052 AA09 CA02 GA04 GB00 GB12 GB17 HA05 HA34 HA39 HA49 HB02 4G066 AA17B AC10D AC12D AC13C AC13D AC14D AC16D AC17D BA03 BA05 BA16 BA35 BA36 BA38 CA43 DA03 FA03 FA28 FA37 FA37

Claims (6)

[Claims] 1. Granular or powdery calcium oxide 7
A desiccant, wherein 0 to 90 parts by weight (except 70) is dispersed in 30 to 10 parts by weight (except 30) of the soft resin. 2. The soft resin has a breaking strength of 50 MPa.
The desiccant according to claim 1, which has the following elongation and a breaking elongation of 200% or more. 3. The soft resin has a breaking strength of 25 MPa.
The desiccant according to claim 2, wherein the desiccant is at most 500%. 4. Calcium oxide 7 in granular or powder form
0 to 90 parts by weight (excluding 70) of soft resin 30 to 10
Dispersed in parts by weight (excluding 30) of the dissolved solution,
A method for producing a desiccant, comprising drying and solidifying. 5. Granular or powdery calcium oxide 7.
0 to 90 parts by weight (except 70) are mixed and dispersed in 30 to 10 parts by weight (except 30) of the soft resin in a hot-melt state in a blending apparatus in which a dead spot does not substantially occur,
A method for producing a desiccant, comprising solidifying. 6. The soft resin has a melt flow rate of 1
The method for producing a desiccant according to claim 5, which is 0 or more.