KR100303625B1 - Desiccant Composition - Google Patents

Abstract

A novel desiccant composition consisting of calcium chloride and starch is disclosed. Preferably the starch is modified starch, preferably modified corn starch. The composition contains about 5 to about 95% calcium chloride and about 5 to about 95% starch.

Description

Desiccant Composition

This application is a partial continuing application (CIP) of September 19, 1996, application number 08 / 715,067.

The present invention relates to a desiccant container. More specifically, the present invention relates to a material composition for use in a desiccant container consisting of a combination of calcium chloride and starch.

Desiccant containers that absorb water vapor, water, liquids, and the like are well known in the art. In general, these containers consist of water or water vapor permeable packaging materials, formed from fibers or membrane products, which are tightly sealed at the edges of the packaging. The packaging material encapsulates a desiccant such as silica gel. The volume of water or water vapor absorbed by the desiccant container is determined by the absorption performance of the desiccant contained in the container.

One type of desiccant container absorbs them by permeating both water vapor and liquid through the packaging material and allowing it to be absorbed by the desiccant. In some situations, the packaging material for this type of product is dissolved in order for the desiccant contained in the desiccant container to be in direct contact with the liquid.

Another type of desiccant container absorbs only water vapor, not liquid water. Packaging materials for this type of desiccant container are designed to prevent the water absorbed in the desiccant container in the form of water vapor from falling out of the desiccant container in the form of liquid water.

There are many common products utilized as desiccants. Among the most commonly used include silica gel, calcium sulfate, calcium fluoride, activated carbon, molecular sieves, lithium chloride, calcium chloride and other products. A list of such conventional dry medicaments is described, for example, in Kirk-Othmer, Encyclopedia of Chemical Technology, Volume 7, Pages 378-398. Conventional desiccants used in conventional desiccant containers are described in US Pat. 5,114,003, which also discloses the use of montmorillonite clay, silica gel, molecular sieves, calcium oxide, calcium sulfate and calcium chloride. In addition, silica gel, aluminosilicate, alumina, activated carbon and molecular sieve as drying agents are described in US Pat. 4,464,261.

Due to its low cost and high absorption, commercial grade calcium chloride is widely used as a desiccant. Calcium chloride, which condenses in the form of particles or beads, is described, for example, in US Pat. Used as a desiccant at 3,923,944.

Mixtures and combinations of different materials have been combined with calcium chloride to make dry products. For example, polyethylene glycol is described in US Pat. At 3,779,936 it was mixed with calcium chloride to form a dry product. Furthermore, U.S. Patent No. 3,334,468 discloses the use of calcium chloride and sodium chloride or sodium carbonate. Moreover, combinations of magnesium, lithium or ammonium salts with calcium chloride are described, for example, in US Pat. 3,885,926. The use of calcium chloride with metals, such as iron peeling, is described in US Pat. 1,798,862. Moreover, the use of calcium chloride and activated carbon as dry products is described in US Pat. 2,027,093.

U.S. Patent No. 3,390,511 discloses the use of calcium chloride placed on a carrier material for use as a gas dryer desiccant. A preferred material used as a carrier for calcium chloride is sodium chloride (see US Pat. No. 3,334,468). U.S. Patent No. The dry product at 3,390,511 preferably comprises about 90 to 97% sodium chloride and about 10 to about 3% calcium chloride as carrier. Sodium dichromate and trisodium phosphate may also be included in this product in small amounts. Preferred carriers of calcium chloride are sodium chloride, while other disclosed carriers include sugars, potassium chloride, potassium nitrate, sodium nitrate and starch. See column 3 line 33. The amount of calcium chloride used in this product is 10% or less, since the main component of the product is the carrier.

One problem with the use of calcium chloride as a desiccant is the formation of a liquid mixture on the surface of calcium chloride when water is absorbed. This is a US patent no. 3,334,468. In the case of conventional dry product coexistence, such liquids may leak, causing problems if the dry product is used in storage containers.

While these references, alone or in combination with various compositions, disclose the use of calcium chloride as a desiccant, there is still a need for improved dry products using calcium chloride.

Therefore, it is an object of the present invention to disclose a desiccant composition containing calcium chloride as a main component.

It is a further object of the present invention to disclose a desiccant composition containing calcium chloride mixed with a significant amount of starch to form a desiccant composition.

It is a further object of the present invention to disclose a desiccant composition which is a combination of calcium chloride and starch, preferably modified starch, contained in the packaging material.

It is a further object of the present invention to disclose a desiccant composition containing calcium chloride in which water absorbed by calcium chloride does not leak out of the desiccant container.

It is a further object of the present invention to disclose a desiccant composition contained in a packaging material which prevents leakage of water from within the package by the use of starch, preferably modified starch.

These and other objects and features of the present invention will be apparent to those skilled in the art upon consideration of the following detailed description, drawings and claims. In addition to the drawings, the following provides selected embodiments of the structure and process of the product to illustrate the invention.

1 is a perspective view of a desiccant container.

[Description of Symbols for Main Parts of Drawing]

DESCRIPTION OF SYMBOLS 10 Desiccant container 12 Packaging material 14 Desiccant 16 laminated film layer

22: laminated film 18, 24: inner surface 20, 26: outer surface

According to the present invention there is provided a desiccant composition comprising from about 5 to about 95 weight percent calcium chloride and from about 5 to about 95 weight percent starch. In a preferred embodiment, calcium chloride is included in about 20 to about 95 weight percent of the composition, while starch is included in about 5 to about 80 weight percent of the composition. The starch used may be unmodified, but preferred embodiments are modified starch, preferably modified corn starch.

Although the present invention is adapted to a wide range of uses, a desiccant container 10 for absorbing and fixing liquid is shown for the purpose of illustration in FIG. 1, which consists of a desiccant packaging material 12 encapsulating the liquid absorbent and fixed desiccant 14. do.

Desiccant packaging material 12 may include any conventional packaging material. Preferably, the inner surface 18 and the outer surface, preferably formed of an uncoated microporous or nonwoven layer sealed with an inner surface 24 and an outer surface 26 and sealed with a water vapor permeable laminated film 22. A laminate layer 16 having a surface 20. The inner surface of the layers is sealed at the edges as shown in FIG.

Conventional microporous or nonwoven membranes used for the production of laminated packaging materials have been formed of composite membranes bonded to another layer of material. Typically, the bonding between the two layers is performed by using an adhesive that coats one or both sides of the inner surface of the layer. It has surprisingly been found that strong, laminated desiccant packaging materials can be produced from uncoated microporous or nonwoven membranes.

The uncoated microporous membrane or nonwoven membrane 16 includes a membrane having a plurality of micro apertures, which are gas permeable and water impermeable when the air pressure between the inside and the outside of the membrane is not different. The size of the opening is preferably in the range of approximately 0.01 to 50 microns. The uncoated microporous membrane or nonwoven membrane may be composed of a single membrane layer, or may be composed of a laminated layer of separated microporous membranes. Preferably, the membrane is a single layer microporous membrane formed from a polyolefin material such as polyethylene, polypropylene, poly (fluorinated ethylene), ethylene vinyl acetate, ethylene acrylic esters and the like. Uncoated microporous membranes or nonwoven membranes are characterized by the cold orientation of membranes, the orientation of membranes containing different substances, the extraction of different substances from membranes containing different substances, the orientation of membranes treated with different substance extractions, the heat of the resulting membrane after cross-dispersion of fiber bundles. -Can be prepared by any conventional film forming process including pressurized and other conventional processes utilized to form microporous membranes. Many such microporous membranes are commercially available and are sold, for example, under the trademarks Celgard ^R (Hoechst Celanese Corporation), GORE-TEX ^R (Gore & Co. Gmbh) and Tyvek ^R (EI DuPont). Preferred microporous membranes have a Gurley-type air permeability of about 0.01 to 10,000 seconds / 100 millimeters, preferably 1 to 1,000 seconds / 100 millimeters, most preferably about 400 seconds / 100 millimeters or less. Preferably, the microporous membrane is a polyethylene or polypropylene-based microporous membrane, most preferably a polyethylene spun-bonded paper such as Tyvek ^R 1059B or 1037B manufactured by EI DuPont, or San Ai, Ltd., Osaka, Japan. Polypropylene based membranes such as GDT II produced by

The second layer of desiccant packaging material is preferably formed from the uncoated laminate 22. The laminated film can be made from a conventional polymeric material. An important aspect of the composition of the laminated film is that the inner surface 24 of the laminated film, which is bonded to the inner surface 18 of the uncoated microporous or nonwoven film at the edge of the packaging material, is a material compatible with the composition of the inner surface of the microporous or nonwoven film layer. It must be done. Materials that can be used to form such laminated films include conventional polyolefin materials such as polyolefin polypropylene, polyolefin polyethylene, polyester, and the like. Preferably, the uncoated laminate has a lower moisture vapor transmission rate than the microporous or nonwoven membrane. In addition, the softening temperature of the uncoated laminated film is preferably equal to or less than the softening temperature of the inner surface of the uncoated microporous film. Preferably, the laminate film consists of a laminate film comprising a high melting point or high softening point material such as polyester, which is located on the side opposite to the side on which the low melting point material such as polypropylene is laminated. Examples of acceptable laminates include RPP91-1964 or RPP-31-1007a manufactured by RollPrint.

The outer surface 26 of the laminated film is preferably formed from a material which is incompatible with the microporous film, for example, a material having a high melting point or high softening point than the inner surface of the microporous film, or a polyester-like material. On the contrary, the inner surface of the laminated film 24 should be formed from a material compatible with the inner surface 18 of the microporous film. By having two inner surfaces formed from compatible materials, strong bonds are formed between the two layers when they are heat sealed together.

The term "compatible" means that the materials are mixed at the molecular level and can be homogeneously crystallized. Thus, even though the layers may not have exactly the same softening point, they must have compatible softening points in order for the material to be mixed at the molecular level. Compatible bonds should be at least about 5 lb./in. It generally has the above bond strength. For example, compatible materials may contain high density, low density or linear low density polyethylene, as well as non-oriented, biaxially oriented or laminated polypropylene. On the other hand, at least the outer surface of the laminated film should be made from incompatible materials such as polyester or nylon or polyethylene or polypropylene material having a higher softening point than the inner surface of the laminated film material.

In addition, it is also important that the inner surfaces of both the laminated and microporous or nonwoven films should not be coated with an adhesive. When sealed to another coating or uncoated film, the coating film frequently forms a degraded quality, weak seal. In addition, the sealing machine used to seal the coating film is expensive and difficult to operate, resulting in expensive costs for producing the sealing coating film. In addition, uncoated films are generally cheaper than coating films, sometimes up to 50% cheaper.

Suitable materials for use as desiccants to be incorporated into the desiccant package include conventional desiccants, which are absorbed in contact with alkali metal carboxylate salts of silica gel, clay, calcium chloride, starch-polyacrylonitrile and water or water vapor, Gels, other products that thicken, such as sodium polyacrylate. However, preferred dry materials are produced from mixtures of calcium chloride and starch, preferably modified starch, most preferably modified corn starch such as MIRA-SPERSE ^R 623, 626 and 629 produced by AE Staley Manufacturing Company. It was surprisingly found to be possible. The composition of such a desiccant is preferably about 5 to about 95% calcium chloride mixed with about 95 to about 5% starch. Preferably, calcium chloride is included in about 20 to about 95%, while starch is included in about 80 to about 5% of the composition. More preferably, calcium chloride is included in about 50 to about 80%, while starch is included in about 50 to about 20% of the composition.

The starch used in the present invention may include unmodified starch, oxidized starch, enzyme-converted starch and modified starch including functional groups such as hydroxyl, carbonyl, amido and amino groups. Thus, the term "starch" as used throughout the specification and claims includes any starch or mixture of two or more starches. Preferred starches are modified starches such as oxidized, enzyme-converted starch. The modification of the starch may be chemical, such as crosslinking or substitution, or physical, such as granulation.

Conventional starch, such as granular starch, is not used mainly in its original state due to its high viscosity and retrogradeity which is a special problem of unmodified starch. This problem is significantly reduced in modified starches such as hydroxyethylated starch. For example, in most industries unmodified starch is converted to modified starches such as oxidized, enzymatically converted or hydroxyethylated starch. Alternatively, further modified starches in the form of cationic starches may be used. However, the price of such cationic starch is significant compared to unmodified or hydroxyethylated starch. Of importance for the selection of starch is the ability to absorb water, preferably cool water, ie water up to about 40-50 ° C.

In a preferred embodiment, the starch when combined with water should have a higher viscosity than when water alone. When measured as Brookfield viscosity, the viscosity should be at least about 1.0 cps. An important action provided by modified starch is the ability to mix with water and to thicken or gel the water or calcium chloride / water composition formed during water absorption by calcium chloride.

The calcium chloride / corn starch desiccant composition may not only be used in the desiccant container outlined above, but may also be used in any conventional desiccant container used to absorb water or water vapor.

The process of forming the desiccant container consists of many steps. Desiccant packaging material is formed first. In order to form the desiccant packaging material of the present invention, an uncoated microporous film and a nonwoven film 16 are first formed or obtained from conventional raw materials. In a preferred embodiment, the microporous membrane is Celgard ^R manufactured by Hoechst Celanese Corporation, Tyvek ^R No. manufactured by EI DuPont. Uncoated microporous or nonwoven membranes such as 1059B and 1073B or any other polypropylene based nonwoven membranes such as GDT I, II manufactured by San Ai of Osaka, Japan. As described above, the permeability of the microporous membrane should be about 1 to about 1000 Gurley seconds per 100 millimeters, preferably about 400 seconds or less per 100 millimeters.

After the formation of the uncoated microporous film or the nonwoven film, the uncoated laminated film 22 is formed. As described above, these uncoated laminates can be made of different layers of the same or different materials stacked together. However, an important element of the composition of this material is that the membrane must be uncoated, and the inner surface 24 of the laminated membrane sealed to the inner surface 18 of the microporous material is " compatible with the inner surface of the uncoated microporous or nonwoven membrane. "It must be formed of one material. In one preferred embodiment, the laminated film is a laminated film having a polypropylene material on the inner surface and a polyester material on the outer surface, such as RPP 91-1964 manufactured by RollPrint. Another preferred embodiment is RPP 31-1007A, which is also a polyethylene-based material made by RollPrint.

After forming the two layers, the edges of the layers are sealed by conventional heat sealing procedures. One advantage of the product formed from the present invention is that the bond formed between two compatible uncoated materials is stronger than conventional bonds utilizing an adhesive coating. By utilizing the ability of compatible materials to form a strong seal without the use of adhesives, the strength of the desiccant packaging material has been significantly increased over conventional packaging materials. In addition, these uncoated materials are produced cheaper and work better through the sealing device.

The preferred desiccant is then placed in a desiccant packaging. By using a preferred desiccant formed from calcium chloride and starch, preferably modified starch, the same water absorption as before is achieved using less dry matter than is required for use in conventional desiccant containers.

The mixture of calcium chloride and starch may be prepared by placing the two components in a conventional mixing device such as a tumbler mixer or the two components may be fed directly from the two separate feeds into the desiccant packaging. Besides the physical mixing of these materials, there is no further process for the calcium chloride / starch composition. The simple mixing of the two materials produces a desiccant composition with great utility.

Following the desiccant addition into the desiccant packaging material, the remaining unsealed edge of the desiccant container is sealed to form a complete desiccant container.

Example

Example 1

The water absorption performance of the desiccant composition comprising calcium chloride and cornstarch is tested. 133 g of a mixture of Mirasperse 629 modified waxy corn starch and calcium chloride, sold by Staley Foods Inc., Illinois, USA, is placed in a conventional desiccant bag for desiccant products. It is sold by Desiccants and is known as "CONTAINER DRI ^R ". For about two months, the desiccant bag is placed in an environment with a relative humidity of 80% at 25 ° C. The test results are shown in Table 1.

Example 2

The same test is performed on a composition of corn starch and calcium chloride in a 1: 4 ratio using the same type of Mirasperse 624 modified corn starch as discussed in Example 1. Water absorption over time is shown in Table 1.

Example 3

The water absorbency of a typical 500 g of CONTAINER DRI ^R desiccant product made by United Desiccants is compared to the products of Examples 1 and 2 using the same procedure used in Example 1. The water absorption performance of this product over time is also shown in Table 1.

In addition, the performance of the modified starch / calcium chloride product in the 1/4 ratio of Example 2 is compared with the conventional 500 g CONTAINER DRI ^R product. The performance at 40% relative humidity, water absorption at 40% relative humidity, performance at 80% relative humidity and water absorption at 80% relative humidity after two months are presented in Table 2.

As will be apparent from this example, the composition of cornstarch and calcium chloride is superior in water absorption compared to conventional dry matter. Such water absorption is at least as good as conventional desiccant packages sold on the market. In addition, the desiccant composition of Example 2 is compared to the CONTAINER DRI ^R product after 265 hours. Because of the ability of the starch to absorb water and liquid calcium chloride on the surface of the calcium chloride product, the water does not leak out of the container even after three months.

Claims (18)

A desiccant composition comprising at least about 5 to about 95 weight percent calcium chloride and about 5 to about 95 weight percent starch of the composition. The desiccant composition of claim 1 comprising about 20 to about 95 weight percent calcium chloride and about 5 to about 80 weight percent starch of the composition. The desiccant composition of claim 1 comprising about 50 to about 80 weight percent calcium chloride and about 20 to about 50 weight percent starch of the composition. The desiccant composition according to claim 1, wherein the starch is modified starch. The desiccant composition according to claim 1, wherein the starch is modified corn starch. The desiccant composition of claim 1 wherein the starch exhibits a Brookfield viscosity of at least about 1 cps. A desiccant container comprising a desiccant composition consisting of at least about 5 to 95 weight percent calcium chloride and about 5 to 95 weight percent starch of the composition, immobilized in the water vapor permeable membrane product. The desiccant container of claim 7 comprising about 20 to about 95 weight percent calcium chloride and about 5 to about 80 weight percent starch of the composition. 8. A desiccant container according to claim 7, comprising about 50 to about 80 weight percent calcium chloride and about 20 to about 50 weight percent starch of the composition. 8. The desiccant container according to claim 7, wherein the starch is modified starch. 8. The desiccant container according to claim 7, wherein the starch is modified corn starch. 8. The desiccant container of claim 7, wherein the starch exhibits a Brookfield viscosity of at least about 1 cps. (a) preparing a water vapor permeable membrane product, (b) preparing a desiccant composition comprising at least about 5 to 95 weight percent calcium chloride and about 5 to about 95 weight percent starch of the composition, (c) placing the desiccant composition between the layers of the vapor permeable membrane product, and (d) sealing the edges of the water vapor permeable membrane product around the desiccant composition to produce a desiccant container. The method of claim 13, comprising about 20 to about 95 weight percent calcium chloride and about 5 to about 80 weight percent starch of the composition. The method of claim 13, comprising about 50 to about 80 weight percent calcium chloride and about 20 to about 50 weight percent starch of the composition. The method of claim 13, wherein the starch is modified starch. The method of claim 13, wherein the starch is modified corn starch. The method of claim 13, wherein the starch exhibits a Brookfield viscosity of at least about 1 cps.

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