JP2018165025A - Moisture absorption film and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a moisture absorption film which has heat resistance, can be made into a film favorably and is good in dispersibility of a moisture absorbent.SOLUTION: The moisture absorption films 10a and 10b are moisture absorption films each of which comprises a polypropylene resin and a moisture absorption layer 2 containing a moisture absorbent, in each of which the polypropylene resin has strain hardening property.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hygroscopic film and a method for producing the same.

  Conventionally, in the fields of foods, pharmaceuticals, electronic parts, precision machines, recording materials, and the like, a method of packing a desiccant in a package for packaging these has been used for the purpose of preventing quality deterioration due to moisture. In addition, the packaging material itself is allowed to contain a desiccant so that the packaging material itself, such as a film and a laminate for packaging having the film, does not contain a separate desiccant in the packaging body. ing.

  For example, Patent Document 1 discloses a hygroscopic film using a desiccant-containing resin composed of a molecular sieve and a resin of MFR 10 or higher. As the resin, a low-density polyethylene having a relatively low melting point or a random copolymer of ethylene and methacrylate is used.

  Moreover, in order to improve heat resistance, the laminated body for packaging using a polypropylene is also proposed. More specifically, Patent Document 2 discloses a laminate for PTP or blister pack having a base material layer and an absorption layer. In Patent Document 2, the absorption layer has a configuration in which an outer skin layer, an intermediate layer, and an inner skin layer are laminated in this order. The outer skin layer and the inner skin layer are made of polypropylene resin, and the intermediate layer is made of polypropylene. It is said to be composed of a blend of blend resin and absorbent having 66 to 95% by weight of resin and 34 to 5% by weight of polyethylene resin.

JP-A-2005-280188 JP 2013-199283 A

  Depending on the contents to be packaged with the packaging material, it is necessary to perform a heat treatment such as a drying step before distribution. For example, in the case of an electronic / battery member, it is necessary to perform a drying process at around 120 ° C. in order to remove moisture in the assembly process. However, as described in Patent Documents 1 and 2, when a film containing polyethylene is used, the moisture-absorbing film is softened in this drying process, which may cause a problem in contact with the electronic / battery member. is there.

  On the other hand, when only polypropylene is used as the thermoplastic resin in order to improve heat resistance, as taught in Patent Document 2, when the absorbent layer is formed, wrinkles occur in the absorbent layer, and the electronic / battery member There was a problem in the encapsulation of. The expression of wrinkles tends to be frequently observed when the content of the absorbent such as a hygroscopic agent is large, particularly when the content is 20% by mass or more.

  In addition, when trying to disperse the hygroscopic agent in polypropylene, the hygroscopic agent may not be sufficiently dispersed but may aggregate and impair the appearance.

  Therefore, there is a need to provide a hygroscopic film that has heat resistance, can be formed into a good film, and has good dispersibility of the hygroscopic agent.

As a result of intensive studies, the present inventors have found that the above problems can be solved by the following means, and have completed the present invention. That is, the present invention is as follows:
<1> a polypropylene resin, and a hygroscopic layer containing a hygroscopic agent, and the polypropylene resin has strain hardening properties.
Hygroscopic film.
<2> The moisture-absorbing film according to <1>, wherein the polypropylene-based resin has a melt mass flow rate in accordance with JIS K7210 of 6.0 to 50 g / 10 min.
<3> The moisture absorbing film according to <1> or <2>, wherein the polypropylene resin is at least one selected from the group consisting of homopolypropylene, random polypropylene, and block polypropylene.
<4> The moisture-absorbing film according to any one of <1> to <3>, wherein the hygroscopic agent is zeolite.
<5> The moisture absorbent film according to any one of <1> to <4>, wherein the content of the moisture absorbent is 20 to 80% by mass based on the entire moisture absorbent layer.
<6> The moisture absorbing film according to any one of <1> to <5>, further including a skin layer containing a polypropylene resin on one or both surfaces of the moisture absorbing layer. .
<7> The moisture-absorbing film according to <6>, wherein the polypropylene resin of the skin layer has strain hardening properties.
<8> The moisture absorbing film according to any one of <1> to <7>, wherein the substrate layer is laminated on the substrate layer,
A laminate for packaging, comprising:
<9> The packaging laminate according to <8> above and a content, and a moisture-absorbing film of the packaging laminate is disposed on the content side.
Packaging body.
<10> A process for producing a masterbatch by melt-kneading a strain-curable polypropylene resin and a hygroscopic agent, and forming a masterbatch to produce a hygroscopic film. Production method.

  ADVANTAGE OF THE INVENTION According to this invention, it has heat resistance, can form a film | membrane favorably, and can provide the moisture absorption film which has the dispersibility of a hygroscopic agent favorable.

FIG. 1 is a diagram showing the layer structure of the moisture-absorbing film of the present invention. FIG. 2 is a diagram showing a measurement mechanism of elongational viscosity behavior. FIG. 3 is a diagram showing a layer configuration of the packaging laminate of the present invention. FIG. 4 is a diagram showing the measurement results of elongational viscosity. FIG. 5 is a diagram showing the measurement results of elongational viscosity.

《Hygroscopic film》
As shown to Fig.1 (a), the moisture absorption film (10a) of this invention comprises the moisture absorption layer (2) containing a polypropylene-type resin and a moisture absorbent. This polypropylene resin has strain hardening properties.

  Moreover, as shown in FIG.1 (b), the moisture absorption film (10b) of this invention further has the skin layer (4) containing a polypropylene resin in one or both surfaces of a moisture absorption layer (2). You may have.

  The present inventors have found that the above-described configuration can provide a moisture-absorbing film having heat resistance, good film formation, and good dispersibility of the moisture-absorbing agent. Although not wishing to be bound by theory, the above-mentioned polypropylene resin has strain-hardening properties, so that the elongation viscosity of the polypropylene resin increases due to the shearing force applied when the hygroscopic agent and the polypropylene resin are kneaded. As a result, the agglomerates of the hygroscopic agent are well crushed and dispersed well, so that the film is considered to be formed well. Moreover, the heat resistance of a moisture absorption film can be improved by using a polypropylene whose melting | fusing point is high compared with the resin composition containing polyethylene.

  The moisture-absorbing film of the present invention that brings about the above-described action is not only useful as a packaging laminate and packaging as mentioned below, but also as various applications that are expected to be exposed to high heat. Useful. More specifically, the hygroscopic film of the present invention is also useful as a sheet-like getter material that can be incorporated into a fuel cell, a solar cell, an organic EL device, or the like.

  Below, each component of this invention is demonstrated.

<Hygroscopic layer>
The moisture absorption layer contains a polypropylene resin and a moisture absorbent.

  The content of the hygroscopic agent in the hygroscopic layer is more than 0% by mass, 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, or 50% by mass. In addition, it can be 80% by mass or less, 70% by mass or less, or 60% by mass or less. In particular, when the content is 20% by mass or more, the fluidity of the resin composition constituting the moisture-absorbing layer is deteriorated, the dispersibility of the moisture-absorbing agent is also deteriorated, and the film formation tends to be difficult. It becomes.

  The thickness of the hygroscopic layer can be 5 μm or more, 10 μm or more, 20 μm or more, or 30 μm or more, and can be 200 μm or less, 180 μm or less, 160 μm or less, 140 μm or less, 120 μm or less, or 100 μm or less.

{Polypropylene resin}
The polypropylene resin is a resin containing propylene group repeating units in the polymer main chain of 30 mol% or more, 40 mol% or more, 50 mol% or more, 60 mol% or more, 70 mol% or more, or 80 mol% or more. PP) homopolymers, random polypropylene (random PP), block polypropylene (block PP), chlorinated polypropylene, carboxylic acid modified polypropylene, and derivatives thereof, and mixtures thereof.

  The polypropylene-based resin in the moisture absorption layer is a polypropylene-based resin having strain hardening property among the above-mentioned polypropylene-based resins. Whether or not the polypropylene resin has strain-hardening properties can be determined by measuring the elongational viscosity behavior of the polypropylene resin over time.

The measurement of the extensional viscosity behavior can be performed, for example, as follows:
1. A resin to be measured is formed into a resin film.
2. As shown in FIG. 2, both ends of the resin film (2a) are fixed to the two winding drums (32) of the measuring device (30) using a fixing tool (34).
3. The two rolling drums (32) are rotated at a constant speed in the directions indicated by the arrows, and the elongational viscosity of the resin is measured over time.
4). The measurement time is plotted on the horizontal axis and the extensional viscosity is plotted on the vertical axis, and the relationship between the two is plotted on a log-log graph.

  The measurement as described above can be performed using, for example, a measurement device commercially available under the name AR-G2 by T.A. In this case, the resin film can have a length of 18 mm, a width of 10 mm, and a thickness of 0.7 mm. Moreover, the space | interval between fixing tools can be 12.7 mm.

  In the case of a polypropylene resin having strain hardening, there is a region where the slope of the tangent of the curve drawn as described above increases, whereas in the case of a polypropylene resin having no strain hardening, as described above. There is no region where the slope of the tangent of the curve drawn in this way increases. The presence or absence of an increase in the slope of the tangent of the curve will be described in detail in the following examples.

  Such strain hardening property is brought about, for example, when a polypropylene resin molecule has a long-chain side chain. The long chain side chain includes, for example, a linear or branched alkyl group having 5 or more, 10 or more, 50 or more, or 100 or more, and 1000 or less, 500 or less, or 300 or less.

  The flowability of the polypropylene resin can be, for example, 2.0 g / 10 min or more, or 4.0 g / 10 min or more when the melt mass flow rate (MFR) is measured in accordance with JIS K7210. , 50 g / 10 min or less, 30 g / 10 min or less, or 25 g / 10 min or less. In particular, it is preferably 6.0 g / 10 min or more, 8.0 g / 10 min or more, or 9.0 g / 10 min or more from the viewpoint of further improving the dispersibility of the hygroscopic agent.

  The melting point of the polypropylene resin may be 120 ° C. or higher, 125 ° C. or higher, or 130 ° C. or higher, and may be 170 ° C. or lower, 165 ° C. or lower, or 160 ° C. or lower.

{Hygroscopic agent}
Examples of the moisture absorbent include a physical moisture absorbent and a chemical moisture absorbent. The physical and chemical hygroscopic agents exemplified below may be used alone or in combination.

  As the physical hygroscopic agent, for example, zeolite, silica gel, activated carbon and the like can be used. As the zeolite, for example, A type, X type, or LSX type hydrophilic zeolite can be used.

  Examples of chemical moisture absorbents include calcium oxide, magnesium sulfate, magnesium chloride, dibasic sodium phosphate, monobasic sodium phosphate, tribasic sodium phosphate, tribasic lithium phosphate, sodium pyrophosphate, calcium chloride, sodium chloride, Ammonium chloride, potassium carbonate, sodium nitrate, sodium borate, sodium sulfate and the like can be used.

<Skin layer>
The skin layer is an optional layer that can be laminated to one or both sides of the moisture absorbing layer.

  The skin layer can be composed of a polypropylene-based resin, improves the film-forming stability and / or prevents the moisture absorbent from falling off or coming into direct contact with the outside, and / or the surface laminated with the base material layer Smoothness can be imparted.

  As the polypropylene resin constituting the skin layer, the above-mentioned polypropylene resin can be used, but in order to further improve the film-forming stability, it is preferable to use a strain-hardening polypropylene resin. As the polypropylene resin, when skin layers are laminated on both sides of the moisture absorption layer, the polypropylene resins constituting each skin layer may be the same or different.

  The thickness of the skin layer can be 1 μm or more, 3 μm or more, 5 μm or more, or 7 μm or more, and can be 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, or 15 μm or less. When skin layers are laminated on both sides of the moisture absorption layer, the thicknesses of these skin layers may be the same or different.

《Packaging for packaging》
As shown to Fig.3 (a) and (b), the laminated body (20a, 20b) of this invention is laminated | stacked on the base material layer (8) and the base material layer (8) of this invention. Hygroscopic films (10a, 10b) are provided. When a packaging body is constituted using the packaging laminate, a moisture-absorbing film can be disposed on the content side.

  Lamination | stacking with a base material layer and the moisture absorption film of this invention may be performed by a heat seal, or may be performed via an contact bonding layer. As the adhesive layer, for example, a dry laminate adhesive, a hot melt adhesive, a water-soluble adhesive, an emulsion adhesive, and a thermoplastic resin for extrusion lamination can be used.

<Base material layer>
A base material layer is a base material layer which laminates the moisture absorption film of the present invention in a package. It is preferable that this base material layer can provide appropriate moisture and barrier properties to prevent moisture and oxygen from entering from the outside to the hygroscopic film. The base material layer may be, for example, a resin layer, a barrier layer, or a laminate thereof.

{Resin layer}
As the resin layer, a thermoplastic resin excellent in impact resistance, wear resistance, etc., for example, polyolefin, vinyl polymer, polyester, polyamide, etc. can be used alone or in combination of two or more kinds in multiple layers. . This resin layer may be a stretched film or an unstretched film.

  As the polyolefin, a polyethylene resin, a polypropylene resin, a copolymer of ethylene and an oxygen-containing ethylenically unsaturated monomer, or the like can be used. Examples of the copolymer of ethylene and an oxygen-containing ethylenically unsaturated monomer include EVOH (ethylene-vinyl alcohol copolymer).

  In the present specification, the polyethylene-based resin includes a repeating unit of an ethylene group in a polymer main chain of 30 mol% or more, 40 mol% or more, 50 mol% or more, 60 mol% or more, 70 mol% or more, or 80 mol% or more. For example, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), ethylene-acrylic acid copolymer (EAA), ethylene- Methacrylic acid copolymer (EMAA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EMA), ethylene vinyl acetate copolymer (EVA), carboxylic acid-modified polyethylene, carboxylic acid-modified ethylene Vinyl acetate copolymer and Derivatives of al, and is selected from the group consisting of mixtures.

  As the polypropylene resin, the above polypropylene resin can be used.

  As the vinyl polymer, for example, polyvinyl chloride (PVC), polystyrene, PVDC (polyvinylidene chloride), polychlorotrifluoroethylene, PAN (polyacrylonitrile) and the like can be used.

  Examples of the polyester include polyethylene terephthalate (PET) and polybutylene terephthalate.

  Examples of the polyamide include nylon such as nylon (registered trademark) 6 and nylon MXD6.

  The thickness of the resin layer can be 3 μm or more, 5 μm or more, 7 μm or more, 10 μm or more, or 12 μm or more, and is 120 μm or less, 100 μm or less, 80 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, Or it can be 20 micrometers or less.

{Barrier layer}
As the barrier layer, a material capable of suppressing transmission of water vapor from the outside to the moisture absorption layer can be used. When the resin layer has sufficient water vapor barrier properties and gas barrier properties, a barrier layer is not necessary, but when the resin layer does not have sufficient barrier properties, it is preferable to provide a barrier layer. For example, but not limited to, metal foil such as aluminum foil or aluminum alloy, aluminum vapor deposition film, silica vapor deposition film, alumina vapor deposition film, inorganic vapor deposition film such as silica / alumina binary vapor deposition film, or polyvinylidene chloride An organic coating film such as a coating film or a polyvinylidene fluoride coating film can be used.

  The thickness of the barrier layer can be 1 μm or more, 3 μm or more, 5 μm or more, or 7 μm or more, and is 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. Can do.

<Packaging body>
The packaging body of the present invention includes the packaging laminate of the present invention and the contents, and the moisture absorption film of the packaging laminate is disposed on the contents side.

  In the packaging body of the present invention, the packaging laminate of the present invention may contain the contents so that, for example, moisture-absorbing films may be heat-sealed facing each other, or other packaging layers or laminations It may be heat sealed facing the body.

  Examples of the form of the package include bags, tubes, blister containers, and the like, as well as molded containers such as cup containers.

<Contents>
The contents are not limited as long as they can be deteriorated by contact with the outside air, and include drugs, foods, cosmetics, medical instruments, medical equipment, electronic parts, precision machines, recording materials, etc. Can do. Moreover, as a chemical | medical agent, a cleaning agent, an agricultural chemical, etc. are included besides a pharmaceutical formulation.

  In particular, when the contents are contents that are supposed to be subjected to a drying process after sealing, such as medical instruments, medical devices, electronic parts, precision machines, recording materials, etc., softening when the drying process is performed The package of the present invention which is suppressed becomes more useful.

<< Method for producing moisture-absorbing film >>
The method for producing a hygroscopic film of the present invention includes the following steps:
A step of melt-kneading a strain-curable polypropylene resin and a hygroscopic agent to produce a master batch, and a step of producing a master batch to produce a hygroscopic film.

<Process for producing master batch>
The master batch can be produced by melt-kneading a strain-hardening polypropylene resin and a hygroscopic agent. As the polypropylene resin having strain hardening property, the resins mentioned for the moisture absorption layer can be used. The melt-kneading can be performed using, for example, a batch kneader such as a kneader, a Henschel mixer, a mixing roll, or a continuous kneader such as a twin-screw kneader.

  By using a strain-hardening polypropylene resin, the elongational viscosity of the polypropylene resin rises due to the shearing force applied to the polypropylene resin during the above melt-kneading, so that the mass of the hygroscopic agent is crushed well. In order to disperse well, it is considered that the film is formed well in the subsequent film forming process.

<Process for producing a hygroscopic film>
The hygroscopic film can be produced by forming the above master batch. Examples of the film forming method include, but are not limited to, an inflation method, a T-die method, a calendar method, a casting method, press molding, extrusion molding, and injection molding.

  When the adsorbing layer has a skin layer, a master batch for skin layer can be prepared separately, and can be formed by a coextrusion inflation method, a coextrusion T-die method, or the like. As the master batch for the skin layer, as mentioned regarding the skin layer, the above-mentioned polypropylene resin, in particular, a strain-hardening polypropylene resin can be used.

  The present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these.

<< Production of moisture-absorbing film >>
<Example 1>
50 wt% of random polypropylene (MFR 5.0 g / 10 min) as a polypropylene resin and 50 wt% of zeolite (Molecular Sieve 3A) as a hygroscopic agent were kneaded by a twin screw extruder to obtain a master batch for a hygroscopic layer. . Example 1 in which the masterbatch is used for the moisture-absorbing layer, homopolypropylene is used for the skin layer, and skin layers are provided on both sides of the moisture-absorbing layer by coextrusion molding by air-cooling type two-layer inflation A film was formed.

<Examples 2 to 4 and Comparative Examples 1 to 3>
Films of Examples 2 to 4 and Comparative Examples 1 to 3 were produced in the same manner as Example 1 except that the thermoplastic resin shown in Table 1 was used instead of the random polypropylene used in Example 1. .

<Comparative example 4>
A film of Comparative Example 4 was produced in the same manner as Comparative Example 1 except that no hygroscopic agent was contained.

<Evaluation of elongational viscosity behavior>
As already mentioned, the measuring apparatus (AR-G2, T.A. Instruments Co., Ltd.) was used to measure the elongational viscosity behavior of the thermoplastic resins used in the hygroscopic layers of Examples 1 to 4 and Comparative Examples 1 to 4. And evaluated.

  FIG. 4 is a graph showing the elongational viscosity behavior of Examples 2 and 4 and Comparative Example 2. The difference in elongational viscosity behavior observed from these curves is further explained with reference to FIG.

  Since the inclination increases between the tangents 2A and 2B of the curve in Example 2, it can be confirmed that the thermoplastic resin of Example 2 has strain hardening. Moreover, since the inclination increases between the tangents 4A and 4B of the curve in Example 4, it can be confirmed that the thermoplastic resin of Example 4 has strain hardening. On the other hand, in Comparative Example 2, there is no region where the slope of the tangential line increases, so it can be confirmed that the thermosetting resin of Comparative Example 2 does not have strain hardening. .

  Moreover, although not shown in figure, since the thermoplastic resins of Examples 1 and 3 and Comparative Example 3 all have the same curve as that of Example 2, these thermoplastic resins have strain hardening properties. It is what you have. Moreover, since the thermoplastic resins of Comparative Examples 1 and 4 both had the same curve as that of Comparative Example 2, these thermoplastic resins do not have strain hardening properties.

  With respect to the strain curability determined as described above, in Table 1 below, those having strain curability are “◯”, and those having no strain curability are “x”.

<Evaluation>
<Heat-resistant>
Each film formed was stored in a 120 ° C. environment for 2 hours, and then the presence or absence of softening was visually confirmed. The case where there was no softening was “◯”, and the case where there was softening was “×”.

<Film forming properties>
The presence or absence of wrinkles in each film formed was visually observed. The case where there was no wrinkle was indicated as “◯”, and the case where there was a wrinkle was indicated as “x”.

<Zeolite dispersibility>
The dispersibility of the zeolite in the hygroscopic layers of the formed Examples 1 to 4 and Comparative Examples 1 to 3 films was observed using an optical microscope. The case where there was no zeolite agglomeration and high smoothness was designated as “◎”, the case where no zeolite was agglomerated was designated as “◯”, and the case where zeolite was agglomerated was designated as “X”.

  The results are shown in Table 1.

  It can be understood from Table 1 that the moisture-absorbing film using the strain-curable polypropylene resin has heat resistance, can be formed into a good film, and the dispersibility of the moisture-absorbing agent is good. Moreover, when the films of Comparative Examples 1 and 4 using the same kind of random polypropylene are compared, it can be confirmed that the film-forming property is deteriorated due to the presence of the hygroscopic agent in the polypropylene having no strain hardening.

  Further, among the examples, it can be understood that Examples 2 and 3 in which the melt mass flow rate of polypropylene is 6.0 to 20 g / 10 min have better dispersibility of zeolite.

DESCRIPTION OF SYMBOLS 2 Hygroscopic layer 2a Resin film 4 Skin layer 8 Base material layer 10a, 10b Hygroscopic film 20a, 20b Laminate for packaging 30 Measuring apparatus 32 Winding drum 34 Fixing tool

Claims (10)

A polypropylene resin, and a hygroscopic layer containing a hygroscopic agent, and the polypropylene resin has strain hardening properties,
Hygroscopic film.   The moisture absorption film according to claim 1 whose melt mass flow rate based on JIS K7210 of said polypropylene system resin is 6.0-50 g / 10min.   The moisture absorption film according to claim 1 or 2, wherein the polypropylene resin is at least one selected from the group consisting of homopolypropylene, random polypropylene, and block polypropylene.   The hygroscopic film according to claim 1, wherein the hygroscopic agent is zeolite.   The moisture-absorbing film according to any one of claims 1 to 4, wherein a content of the moisture-absorbing agent is 20 to 80% by mass based on the entire moisture-absorbing layer.   The moisture absorption film according to any one of claims 1 to 5, further comprising a skin layer containing a polypropylene resin on one or both surfaces of the moisture absorption layer.   The hygroscopic film according to claim 6, wherein the polypropylene-based resin of the skin layer has strain hardening properties. A hygroscopic film according to any one of claims 1 to 7, which is laminated on the base material layer, and the base material layer,
A laminate for packaging, comprising: The packaging laminate according to claim 8 and a content are provided, and the moisture-absorbing film of the packaging laminate is disposed on the content side.
Packaging body. A method for producing a moisture-absorbing film, comprising: a step of melt-kneading a strain-curing polypropylene resin and a hygroscopic agent to produce a master batch; and a step of producing the master batch to produce a moisture-absorbing film.

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