JP2012017353A - Resin molded article having moisture absorption capacity and drying container using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition molded article which is obtained by using an inexpensive material, has long-term storage stability in an unopened state, and develops, after opened, appropriate instantaneous moisture absorbing property triggered by external water vapor and maintains sufficient moisture absorption capacity.SOLUTION: The resin molded article having moisture absorption capacity is produced by molding a resin composition comprising a base resin and a desiccant that increases its volume by absorbing water, dispersed in the base resin. The base resin contains as principal components a low-density polyethylene resin and a straight-chain low-density polyethylene resin and shows a flexure modulus of 80 MPa or more and 240 MPa or less. In the desiccant, 80% or more by weight of the desiccant comprises particles of calcium oxide or calcium chloride having a particle diameter of 5 μm or more and 100 μm or less. The resin composition contains 35% or more and 75% or less of the desiccant in the resin composition.

Description

  The present invention relates to a resin molded body having hygroscopicity, and more particularly to a resin molded body capable of maintaining the ability to absorb moisture over a long period of time and a drying container using the same.

  Containers for storing articles that are desirable to eliminate the effects of moisture in the air during storage, such as many pharmaceuticals and some foods and medical materials, and hygroscopic resins used therefor Various materials have been proposed.

  Patent Document 1 describes an insert obtained by thermoforming a resin composition obtained by blending a desiccant and a thermoplastic resin. This molded product is based on a thermoplastic resin selected from polyolefins, polycarbonates and polyamides, and a resin composition containing 40% to 75% of a desiccant selected from molecular sieve, silica gel, clay and zinc chloride is heated. Molded.

  The desiccant-containing synthetic resin molding described in Patent Document 2 is a desiccant-containing synthetic resin molding characterized in that calcium oxide and molecular sieve (molecular sieve) are dispersed and mixed in a synthetic resin base. .

  The instantaneous desiccant-containing resin molded article described in Patent Document 3 is a resin containing an instantaneous desiccant containing a molecular sieve, calcium oxide, and a polymer absorbent in a synthetic resin base. It is a molded body.

  The desiccant-containing resin molded body having a high flash rate described in Patent Document 4 is characterized in that calcium oxide and a polymer absorber are mixed and dispersed as a desiccant in an injection-molded synthetic resin molded body. It is a desiccant-containing resin molding with high flashing property.

  The desiccant-containing resin molded article having instantaneous properties and durability described in Patent Document 5 is a synthetic resin obtained by absorbing and expanding a molecular sieve as a desiccant in a synthetic resin molded article that has been injection molded or extruded. It is a desiccant-containing resin molded article having flashiness and sustainability, characterized in that a polymer absorbent that expresses fine cracks is mixed and dispersed in the molded article.

  The desiccant-containing resin molded article having flashiness and durability described in Patent Document 6 is a molecular sieve having a high water absorption rate and a water absorption expansion as a desiccant in a synthetic resin molded article that has been injection molded or extruded. Thus, a desiccant-containing resin molded article having flashiness and sustainability characterized by mixing and dispersing calcium oxide having a fine crack and a high total water absorption capacity in the synthetic resin molded article.

  The instantaneous desiccant-containing resin molded body described in Patent Document 7 absorbs and expands as a desiccant in a synthetic resin molded body that has been injection-molded or extruded, and develops fine cracks in the synthetic resin molded body. Resin molding containing a flashing desiccant, characterized by mixing and dispersing a polymer absorbent that forms a water-containing jelly-like pathway and calcium oxide that absorbs water and expands to develop fine cracks in the synthetic resin molding Body

Special Table 2002-516917 JP 2006-348126 A JP 2007-99886 JP 2007-138090 JP JP 2007-211039 A JP 2007-291258 JP JP 2007-289881

  Investigating the characteristics of each material conventionally used as a desiccant, calcium oxide is cheap and has a high total moisture absorption capacity. There was a drawback that it remained low. On the other hand, molecular sieves (molecular sieves) have a flashing property, and the rise of moisture absorption is fast but lacks sustainability, and is an expensive material. In addition, the polymer absorber has a high water absorption capacity, but has a low hygroscopic capacity at low humidity. Silica gel and clay have a moisture absorption mechanism similar to that of molecular sieves, mainly due to physical adsorption, and their volume does not change even when moisture is absorbed. The internal desiccant does not work effectively. Also, depending on the temperature, there is a property of releasing moisture once absorbed.

  It has been found that when the above-described conventional resin molded body in which these desiccants are combined is applied to, for example, a pharmaceutical container, inconvenience occurs in actual use conditions. That is, the medicines stored in these containers are stored for a relatively long period (about 2 years) in an unopened state, and once opened, they are used for a relatively short period (about 6 months). The contents of the pharmaceutical product are hardly exposed to water vapor in an unopened state, but once opened, the lid is frequently opened and closed, so that it is exposed to a large amount of water vapor.

  When a desiccant-containing resin molding having a high flashing property is used, moisture is actively absorbed during an unopened storage period, and the ability is used up after the essential opening. On the other hand, when a mere persistent desiccant-containing resin molding is used, there is a problem in that it cannot follow the remarkable water vapor exposure after opening, resulting in insufficient drying capacity.

  The problem to be solved by the present invention is to use an inexpensive material and have a long-term storage stability in an unopened state, and after opening, water vapor from the outside is a trigger, so A resin composition molded body that exhibits the above and maintains a sufficient hygroscopic ability is proposed.

As means for solving the above-mentioned problems, the invention according to claim 1 is characterized in that a moisture absorption capacity is obtained by molding a resin composition in which a desiccant that absorbs moisture and increases in volume is dispersed in a base resin. The base resin is mainly composed of a low-density polyethylene resin and a linear low-density polyethylene resin, has a flexural modulus of 80 MPa to 240 MPa, and the desiccant has a weight of 80 % Or more of calcium oxide or calcium chloride having a particle diameter of 5 μm or more and 100 μm or less, and the resin composition contains 35% or more and 75% or less of the desiccant in the resin composition. It is a resin molded body having a hygroscopic ability.

  The invention according to claim 2 is the resin molded body having a hygroscopic ability according to claim 1, wherein the flexural modulus of the base resin is 95 MPa or more and 190 MPa or less.

Further, in the invention according to claim 3, the desiccant is composed of particles of 90% or more by weight of calcium oxide or calcium chloride and having a particle size of 15 μm or more and 50 μm or less, and the resin composition comprises the drying agent. The resin molded body having a moisture absorption capacity according to claim 1 or 2, wherein the resin composition contains 40% or more and 60% or less of the agent.

  Moreover, invention of Claim 4 was equipped with the resin molded object of any one of Claims 1-3 as an inner container or a drying member inside, It is a drying container characterized by the above-mentioned.

  The resin molded body having a hygroscopic ability according to the present invention is obtained by molding a resin composition in which a desiccant that absorbs moisture and increases in volume is dispersed in a base resin having a flexural modulus of 80 MPa to 240 MPa. By using inexpensive calcium oxide or calcium chloride as a desiccant, and adding the desiccant and the particle size within a specific range, the volume of desiccant particles accompanying moisture absorption By increasing the formation of fine cracks in the base resin, and by continuously advancing the generation of these cracks to the inside of the resin molded body, it has succeeded in maintaining a high drying capacity over a long period of time. .

  As the blending conditions of the desiccant at this time, 80% or more of the weight is composed of particles of calcium oxide or calcium chloride having a particle size of 5 μm or more and 100 μm or less, and the resin composition includes the desiccant as a resin composition. It contains 35% or more and 75% or less.

  The resin molded body according to the present invention has a fine crack in the base resin because the desiccant dispersed in the base resin first absorbs moisture and increases its volume. The water vapor in the outside air is taken into the molded body through the crack. That is, while the external environment is low humidity, the desiccant particles inside the molded body hardly react, and therefore, the long-term storage stability is excellent.

  When the external environment of the resin molding becomes high humidity, the desiccant particles near the surface absorb moisture and the volume increases. The fine cracks generated at this time cause the desiccant inside the molding to work, and the fine cracks are chain-reacted. It extends to the inside of the molded body. For this reason, once it comes into contact with the outside air, this triggers a high drying capacity.

  When the flexural modulus of the base resin is 95 MPa or higher and 190 MPa or lower, the balance between the generation and progression of fine cracks and the strength of the entire resin molded body is good.

  The desiccant is composed of particles having a particle size of 15 μm or more and 50 μm or less in which 90% or more of the weight is calcium oxide or calcium chloride, and the resin composition contains 40% or more of the desiccant in the resin composition. When it contains 60% or less, the most preferable result is given in terms of drying ability and sustainability.

  Moreover, the dry container which comprised the said resin molded body inside as an inner container or a drying member has the good preservability before opening, and the capability to hold | maintain the inside of a container at low humidity after opening is high.

FIG. 1 is a cross-sectional explanatory view showing the internal structure of a resin molded body having a moisture absorption capability according to the present invention, and shows a state of no moisture absorption. FIG. 2 is an explanatory cross-sectional view showing the internal structure of a resin molded body having a hygroscopic ability according to the present invention, and shows a state in which the surface starts to absorb moisture. FIG. 3 is a cross-sectional explanatory view showing the internal structure of a resin molded body having a hygroscopic ability according to the present invention, showing a state in which the moisture absorption reaches the inside. FIG. 4 is a cross-sectional explanatory view showing the internal structure of a resin molded body having a hygroscopic ability according to the present invention, and shows a state in which the moisture absorption reaches the inside. FIG. 5 is a schematic cross-sectional view showing an example of a pharmaceutical container using a resin molded body having a hygroscopic ability according to the present invention, and shows an unopened state. FIG. 6 is a schematic cross-sectional view showing an example of a pharmaceutical container using a resin molded body having a hygroscopic ability according to the present invention, and shows a state after opening. FIG. 7 is a schematic cross-sectional view of a drying container using a molded resin body having a hygroscopic ability according to the present invention shown in Example 1. FIG. 8 (1) is a schematic cross-sectional view of the hygroscopic inner cylinder of the drying container shown in FIG. 7, and FIG. 8 (2) is a plan view. FIG. 9 is a graph showing the relationship between the water absorption amount of the resin molded body and the relative humidity in the container in Example 1.

  Hereinafter, the resin molded body having a moisture absorption capability according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional explanatory view showing the internal structure of a resin molded body having a hygroscopic ability according to the present invention, and shows a non-hygroscopic state. Moreover, FIGS. 2-4 is sectional explanatory drawing which showed a mode that moisture absorption advanced to the inside of a resin molding.

  The resin molding which has the moisture absorption capability based on this invention shape | molds the resin composition which disperse | distributed the desiccant particle 3 which absorbs a water | moisture content and increases a volume in the base resin 2. FIG. The base resin 2 is mainly composed of a low-density polyethylene resin and a linear low-density polyethylene resin, and the flexural modulus needs to be 80 MPa or more and 240 MPa or less.

  The low-density polyethylene resin (hereinafter abbreviated as LDPE), which is one main component of the base resin 2, has a role of maintaining its shape while expanding when the desiccant particles 3 expand, and is a straight chain that is the other main component. The low-density polyethylene resin (hereinafter abbreviated as LLDPE) exerts the effect of extending the generated fine crack 4 on its extension and extending the path of the fine crack 4 long. Therefore, the addition of LLDPE is essential.

  As the desiccant, 80% or more of the weight is composed of particles 3 of calcium oxide or calcium chloride having a particle size of 5 μm or more and 100 μm or less, and the resin composition contains 35% or more of the desiccant in the resin composition. It is necessary to contain 75% or less.

As shown in the following reaction formula, calcium oxide reacts with water to become calcium hydroxide and the volume expands. In addition, calcium chloride reacts with water to form monohydrate, dihydrate, tetrahydrate, and hexahydrate, and the volume of the chloride expands similarly. In the case of calcium chloride, anhydrous or dihydrate can be used as a desiccant.

  When the desiccant particles 3 absorb moisture and expand, fine cracks 4 are generated in the surrounding base resin 2. Since external water vapor reaches the inside of the molded body via the fine cracks 4, moisture absorption proceeds continuously.

  At this time, if the base resin 2 is too tough, the cracking does not occur because it exceeds the expansion force of the desiccant. On the other hand, if it is too soft, the expansion of the desiccant is absorbed and cracks are not generated.

  If the base resin has a flexural modulus of 80 MPa or more and 240 MPa or less, moderately fine cracks can be generated. Most preferably, the flexural modulus of the base resin is 95 MPa or more and 190 MPa or less.

  As the base resin, ethylene propylene rubber (EPR) can be added to LDPE in addition to LDPE and LLDPE. Moreover, LLDPE by a metallocene catalyst can be used instead of ordinary LLDPE. The use of a soft polypropylene resin based on a metallocene catalyst instead of LDPE is not preferred because of compatibility with LLDPE.

  On the other hand, with respect to the desiccant, when the particle size of the desiccant is reduced to a fine powder, stress sufficient to cause cracks in the base resin cannot be generated. On the other hand, if the particle size is too large, the dispersibility with the base resin deteriorates, causing problems in molding suitability, or agglomerating into a lump and reducing the hygroscopicity.

  As for the particle size of the desiccant, it is necessary that the particles of 5 μm or more and 100 μm or less are 80% or more of the total weight of the desiccant. The particle size of the desiccant is more preferably 15 μm or more and 50 μm or less, and the particle size within this range is more preferably 90% or more of the total weight of the desiccant.

  About the addition amount of a desiccant, 35% or more and 75% or less are suitable by the weight ratio when a resin composition is 100%. If it is less than 35%, the generation of cracks is insufficient and the moisture absorption capacity is not exhibited. On the other hand, if it exceeds 75%, the molded body becomes brittle, the entire molded body is cracked, fragments are generated, and fine powders and particles are generated, which may be a practical problem.

  The addition amount of the desiccant is more preferably 40% or more and 60% or less by weight ratio when the resin composition is 100%.

  FIGS. 1 to 4 are cross-sectional explanatory views showing the internal structure of a resin molded body having a moisture absorption capability according to the present invention. FIG. 1 shows a non-absorbed state, and FIG. 2 shows that the surface starts to absorb moisture. FIG. 3 shows a state where moisture absorption reaches the inside, and FIG. 4 shows a state where moisture absorption reaches the inside.

  As shown in FIG. 2, in the molded resin body 1 exposed to the atmosphere containing water vapor, the desiccant particles existing near the outermost surface start to absorb moisture. Since the desiccant particles expand with moisture absorption, fine cracks 4 are generated in the base resin 2 around the desiccant particles.

  As shown in FIG. 3, the fine crack 4 gradually progresses to the inside, the water vapor reaches the internal desiccant particles through the crack, and the desiccant particles that have reached the crack start to absorb moisture. .

  As this moisture absorption process proceeds, cracks reach the entire interior as shown in FIG. 4, and the moisture absorption process ends when all the desiccant particles have completely absorbed moisture.

As a method of molding a resin molded body having a hygroscopic ability according to the present invention, a necessary material is previously kneaded and pelletized, and the pellet is subjected to an injection molding machine or an extrusion molding machine to form a desired molded product. it can. Usually, it is meaningless to use the resin molded body according to the present invention alone, and it is often used as an inner part of a moisture-proof container or as an insertion part.

  FIG. 5 is a schematic cross-sectional view showing an example of a pharmaceutical container using a resin molded body having a hygroscopic ability according to the present invention, and shows an unopened state. FIG. 6 shows the state after opening.

  In the example of FIG. 5, the drying container 10 has a lid 13 screwed into a container body in which a moisture-absorbing inner cylinder 12, which is a resin molded body having a moisture-absorbing ability according to the present invention, is inserted inside a moisture-proof outer cylinder 11. It has a combined structure. The lid 13 is provided with an inner ring 16 for improving the sealing performance. In the unopened state, since there is no water vapor intrusion 15 inside the container, the inside of the container is dry and this state is maintained. As shown in FIG. 6, when the drying container 10 is opened, every time the lid 13 is opened and closed, a water vapor intrusion 15 occurs with the outside air. As described above, the water vapor that has contacted the hygroscopic inner cylinder 12 is first absorbed by the desiccant particles near the outermost surface and then sequentially absorbed by the internal desiccant particles.

  For this reason, even if it is once opened, moisture in the air left in the space inside the container is absorbed and removed by the inner cylinder 12 having hygroscopicity when the lid is closed. In such an application, it is assumed that a considerable period of time elapses after opening the contents until the contents are used up. However, since the inner cylinder 12 having hygroscopicity maintains the hygroscopic ability, the contents may be deteriorated. There is no.

  As the moisture-proof outer cylinder 11, a plastic container having a relatively low water vapor permeability such as a high-density polyethylene resin, a polypropylene resin, a polyethylene terephthalate resin, and an acrylic resin is suitable in addition to a metal or glass container. It is also preferable to use a barrier container in which a material having a low water vapor permeability such as an aluminum foil or a gas barrier film on which a metal oxide is deposited is combined.

  A resin composition prepared by mixing and dispersing in a base resin in which LDPE and LLDPE are mixed at a ratio of 1: 1 so as to contain 45% of calcium oxide having a particle size adjusted as follows is prepared, and an injection molding method is used. Thus, a resin molded body corresponding to the hygroscopic inner cylinder 12 having a shape as shown in FIGS. 8 (1) and (2) was prepared. As for the dimensions of the resin molding, the outer diameter at the upper end is about 27 mm, the height is about 43 mm, and the weight is about 11 g. Therefore, this resin molding contains about 5 g of calcium oxide. The flexural modulus of the base resin was 150 MPa.

(Calcium oxide particle size)
Fine particles having a particle size of 10 μm or less and coarse particles having a particle size of 60 μm or more were removed, and particles having a particle size of 15 μm or more and 50 μm or less accounted for 95% of the weight.

An outer container corresponding to the moisture-proof outer cylinder 11 having a shape as shown in FIG. 7 was prepared by an injection molding method using polypropylene resin. A lid 13 connected by a hinge is integrally formed with the outer container, and the container can be sealed by the lid 13. The outer container has an upper end outer diameter of about 30 mm and a height of about 43 mm.
The resin molding was inserted into the outer container. Since a fine V-shaped ventilation groove was provided on the outer periphery of the side wall of the resin molded body and the through hole 17 was provided on the bottom surface, the insertion could be performed smoothly.

  After holding the lid of the container for 1 minute in an environment of 20 ° C. and 65% RH, the lid is closed and the time required for the relative humidity in the container to be less than 10% RH is about 2 samples. It was measured. The results are shown in Table 1.

  Thus, it was found that the relative humidity in the container reached less than 10% 7 hours after closing the lid. Next, the relationship between the storage period of the container capable of maintaining the relative humidity in the container at 10% or less and the water absorption amount was examined. FIG. 9 is a graph showing the relationship between the water absorption amount of the resin molded body and the relative humidity in the container. From this result, it was found that the relative humidity in the container could be kept below 10% up to a water absorption of 423 mg.

  Next, in order to estimate the storage stability of this container, the amount of permeated water per day was examined in an atmosphere of 40 ° C. and 90% RH and in an atmosphere of 20 ° C. and 65% RH. The number of days that could be kept below% RH was estimated. The results are shown in Table 2.

  Thus, it is estimated that the drying container of Example 1 using the resin molded body having moisture absorption capability according to the present invention has a humidity retention capability of about one year in a harsh environment and about two years in a normal environment. Is done. In addition, since the volume increases when the hygroscopic inner cylinder completely absorbs moisture, depending on the fitting dimension with the moisture-proof outer cylinder, the opening and closing of the lid of the outer cylinder may be hindered. it can. In this way, the degree of moisture absorption of the inner cylinder can be estimated by the degree of opening and closing of the lid of the outer cylinder, so that it is possible to prevent troubles such as accidentally using a moisture-absorbed container.

DESCRIPTION OF SYMBOLS 1 ... Molded body 2 ... Base resin 3 ... Desiccant particle 4 ... Fine crack 5 ... Absorbed desiccant particle 10 ... Drying container 11 ... Moisture-proof outer cylinder 12 ... Hygroscopic inner cylinder 13 ... Lid 14 ... Contents 15 ... Water vapor intrusion 16 ... Inner ring 17 ... Through hole

Claims (4)

  A resin molded body having a moisture absorption capability, which is formed by molding a resin composition in which a desiccant that absorbs moisture and increases in volume is dispersed in a base resin, wherein the base resin includes a low-density polyethylene resin and a direct resin. The main component is a chain low density polyethylene resin, the flexural modulus is 80 MPa or more and 240 MPa or less, and the desiccant is a particle having a particle size of 5 μm or more and 100 μm or less of calcium oxide or calcium chloride of 80% or more of the weight. And the resin composition contains the desiccant in the resin composition in an amount of 35% to 75%.   The resin molded body having a hygroscopic capacity according to claim 1, wherein the base resin has a flexural modulus of 95 MPa or more and 190 MPa or less.   90% or more of the weight of the desiccant is composed of particles of calcium oxide or calcium chloride having a particle size of 15 μm or more and 50 μm or less, and the resin composition contains 40% or more of the desiccant in the resin composition. % Or less, The molded resin body having a hygroscopic capacity according to claim 1 or 2.   A drying container comprising the resin molding according to any one of claims 1 to 3 as an inner container or a drying member.

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