JP7240435B2 - Laminates and containers - Google Patents

Description

The present invention relates to laminates and containers.

In recent years, as a preparation for intravenous drip infusion, a premix type soft bag preparation in which a pre-diluted injection preparation is filled in a container molded of plastic resin or the like has been developed. This type of preparation is more convenient and quicker to use, as well as more convenient to dispose of the container than when a concentrated drug is filled in a glass container such as a bottle or an ampoule.

However, when general resins such as polyolefin (polyethylene, polypropylene) and polyvinyl chloride are used as container materials for soft bag formulations, some drugs such as nitroglycerin, albumin, vitamins, trace elements, radical scavengers, etc. is known to adsorb or permeate. Therefore, a container having a cyclic olefin resin layer as a material that does not adsorb or permeate a drug is useful as a container for soft bag formulations (for example, Patent Documents 1 and 2).

Cyclic olefin-based resins form a three-dimensional molecular structure with a high density compared to polyethylene and the like. Therefore, when a cyclic olefin-based resin is formed into a sheet by itself, the sheet tends to be hard and brittle. Therefore, in order to process it into a soft bag, it is common to laminate a polyethylene resin, a polypropylene resin, or the like.

On the other hand, the cyclic olefin resin has a problem that it is difficult to obtain adhesive strength with other materials. As a means to solve this problem, a method has been proposed in which an adhesive layer composed mainly of a linear low-density polyethylene resin polymerized using a single-site catalyst is provided adjacent to the cyclic olefin resin layer ( For example, Patent Document 3).

For example, Patent Document 3 proposes a laminated sheet in which the innermost layer is a cyclic olefin resin, the intermediate layer is a linear low-density polyethylene resin polymerized using a single-site catalyst, and the outermost layer is a high-density polyethylene. there is Although this structure has excellent adhesion stability between layers, high-density polyethylene, which generally lacks flexibility and transparency, is used. For this reason, if the thickness of the outermost layer is increased to ensure heat resistance, there is a drawback that the visibility and dischargeability of the contents are impaired, and the performance required for a pharmaceutical container is not satisfied. Further, since the melting point of high-density polyethylene is as low as about 120° C., if heat treatment or sterilization treatment is performed at a higher temperature than that, the container may be deformed.

As a means of imparting heat resistance to a container, it is common to use a polypropylene-based resin having a higher melting point than polyethylene, but it has been difficult in the past to firmly bond a polypropylene-based resin layer and a cyclic olefin-based resin layer. rice field. In order to solve this problem, for example, in Patent Document 4, a linear low-density polyethylene resin polymerized using a single-site catalyst is used as an adhesive layer between a cyclic polyolefin resin layer and a polypropylene resin layer. , a composition in which a polypropylene-based resin is blended has been proposed.
Patent Document 5 proposes a multi-layer container having a two-layer structure, but the polypropylene-based resin layer adjacent to the cyclic olefin-based resin layer contains a styrene-based elastomer.

JP-A-2008-29829 WO2009/66752 JP 2008-18063 A JP-A-2005-335108 Japanese Unexamined Patent Application Publication No. 2011-93209

However, in the laminate described in Patent Document 4, since a polyethylene resin is used in the adhesive layer, there is a possibility that the adhesive strength may be lowered at a temperature higher than the melting point of the polyethylene resin. In addition, the initial adhesive strength of the adhesive layer is not sufficient, and when the container filled with the contents is dropped, peeling of the seal interface and liquid leakage may occur.

Further, the above-mentioned Patent Document 2 proposes a container in which a resin composition layer made of a blend of a propylene-based polymer and a styrene-based elastomer is laminated between a cyclic olefin-based resin layer and a polypropylene-based resin layer. ing. However, in this configuration, if an organic solvent such as alcohol or ethyl acetate adheres to the adhesion interface, the interlayer adhesion strength may be greatly reduced, and delamination may occur.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a laminate and a container that are excellent in adhesive strength between layers and whose adhesive strength does not easily decrease even during high-temperature sterilization or the like.

In order to solve the above-mentioned problems, the present invention provides a laminate of at least three layers including a structure in which a cyclic olefin resin layer, an adhesive layer, and a polypropylene resin layer are laminated in this order, The adhesive layer contains a resin component consisting of linear low-density polyethylene, a styrene-based elastomer, and a polypropylene-based resin, and the ratio of (linear low-density polyethylene):(total of styrene-based elastomer and polypropylene-based resin) is , and a weight ratio of 40:60 to 95:5.

The weight ratio of (styrene-based elastomer):(polypropylene-based resin) in the adhesive layer is preferably in the range of 5:95 to 50:50.
The styrene-based elastomer is preferably one or more selected from SEBS, SEPS, SEBC, and HSBR.
It is preferable that the styrene-based elastomer is SEBS.
It is preferable that the styrene content in the styrene-based elastomer is 10 to 50% by weight.
The polypropylene-based resin contained in the adhesive layer is preferably a propylene-based copolymer obtained by copolymerizing at least one of ethylene and an α-olefin having 4 to 8 carbon atoms.

The present invention also provides a container formed using the laminate.

ADVANTAGE OF THE INVENTION According to this invention, the laminated body and container which are excellent in the adhesive strength between layers and whose adhesive strength is hard to fall even by high-temperature sterilization processing etc. can be provided.

The present invention will be described below based on preferred embodiments.

The laminate of this embodiment is a laminate of at least three layers including a structure in which a cyclic olefin-based resin layer, an adhesive layer, and a polypropylene-based resin layer are laminated in this order. The adhesive layer is an intermediate layer for bonding between the cyclic olefin resin layer and the polypropylene resin layer.

The adhesive layer contains linear low-density polyethylene, a styrene-based elastomer, and a polypropylene-based resin. The resin component contained in the adhesive layer may substantially consist of three components: linear low-density polyethylene, styrene-based elastomer, and polypropylene-based resin. The adhesive layer may contain an additive component in addition to the resin component.

Linear low-density polyethylene (LLDPE) is usually made by copolymerizing α-olefins with 4 or more carbon atoms and introducing short-chain branching to reduce long-chain branching and create a linear molecular structure. have. α-Olefins to be copolymerized with LLDPE include 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like.

Types of LLDPE contained in the adhesive layer include a resin polymerized using a Ziegler-Natta catalyst, a resin polymerized using a single-site catalyst, and the like. LLDPE polymerized using a single-site catalyst is preferable because it has a narrow molecular weight distribution and excellent mechanical properties. Single site catalysts include metallocene catalysts. Examples of metallocene-based catalysts include catalysts containing metallocene compounds containing ligands having a cyclopentadienyl skeleton and metals such as zirconium and hafnium.

The polypropylene-based resin contained in the adhesive layer is preferably a propylene-based copolymer obtained by copolymerizing at least one type of ethylene or α-olefin having 4 to 8 carbon atoms. Among them, polymerization is performed using a single-site catalyst. propylene-based copolymers are preferred. Comonomers to be copolymerized with the polypropylene resin include ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like. The polypropylene-based resin contained in the adhesive layer may be a random copolymer or a block copolymer.

Styrene-based elastomers contained in the adhesive layer include copolymers of styrene and aliphatic olefins. Blocks containing styrene constitute hard blocks and blocks containing aliphatic olefins constitute soft blocks. The higher the styrene content in the molecule, the stronger the adhesive strength. However, if the styrene content is too high, flexibility is impaired, so the styrene content in the styrene-based elastomer is preferably 10 to 50% by weight, more preferably 10 to 30% by weight, and further preferably 10 to 20% by weight. preferable.

Specific examples of styrene-based elastomers include styrene-ethylene copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-ethylene-propylene-styrene block copolymers (SEPS), and styrene-ethylene-butylene. - styrene block copolymer (SEBS), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-isoprene-butadiene-styrene block copolymer (SIBS) , styrene-ethylene-butylene-olefin crystal block copolymer (SEBC), hydrogenated styrene-butadiene rubber (HSBR), and the like. Among these, one or more selected from SEBS, SEPS, SEBC, and HSBR are preferable, and SEBS is particularly preferable.
In addition, SEBS is generally obtained by hydrogenating (hydrogenating) a styrene-butadiene-styrene block copolymer, and converting a butadiene unit into two ethylene units or a butylene unit. or those subjected to selective hydrogenation or the like.

The weight ratio of (linear low-density polyethylene):(total of styrene-based elastomer and polypropylene-based resin) in the adhesive layer is preferably in the range of 40:60 to 95:5. Also, the ratio of (styrene-based elastomer):(polypropylene-based resin) in the adhesive layer is preferably in the range of 5:95 to 50:50 as a weight ratio.

Among the resin components constituting the adhesive layer, the ratio of linear low-density polyethylene, styrene-based elastomer, and polypropylene-based resin is, for example, 40 to 95 parts by weight of linear low-density polyethylene with the total resin component being 100 parts by weight. 1 to 50 parts by weight of the styrene elastomer and 1 to 59 parts by weight of the polypropylene resin.
Here, the linear low-density polyethylene is more preferably in a proportion of 40 to 80 parts by weight.
Also, the proportion of the styrene-based elastomer is more preferably 1 to 30 parts by weight.
Further, it is more preferable that the proportion of the polypropylene resin is 30 to 50 parts by weight.

In the adhesive layer, the total of the three components of linear low-density polyethylene, styrene-based elastomer, and polypropylene-based resin is preferably 90% by weight or more, more preferably 95% by weight or more, and may be 100% by weight. The adhesive layer may contain resin components or additive components other than the above three components, but the proportion thereof is preferably 10% by weight or less, more preferably 5% by weight or less, of the entire adhesive layer.

The polypropylene-based resin layer is a layer mainly containing a polypropylene (PP)-based resin. The polypropylene-based resin used in the polypropylene-based resin layer may be a propylene homopolymer or a copolymer with at least one or more of ethylene or an α-olefin having 4 to 8 carbon atoms. good too. When the polypropylene-based resin contained in the polypropylene-based resin layer is a copolymer, the copolymer may be a random copolymer or a block copolymer. The polypropylene-based resin layer may contain one type of polypropylene-based resin, or may contain two or more types of polypropylene-based resin layers.

The cyclic olefin-based resin layer is a layer that mainly contains a cyclic olefin-based resin. The cyclic olefin resin contained in the cyclic olefin resin is a polymer composed of one or more olefin monomers or a polymer in which the double bond is hydrogenated, and at least one of the olefin monomers is cyclic carbonized. It is a cyclic olefin monomer having a hydrogen skeleton. Cyclic olefin monomers include, for example, norbornene compounds.
In the following description, the term "cyclic olefin-based resin" simply refers to a cyclic olefin-based resin included in the cyclic olefin-based resin.

Cyclic olefin resins are polymers obtained by hydrogenating the remaining double bonds after ring-opening metathesis polymerization of norbornene compounds, addition polymers composed of two or more cyclic olefin monomers, and cyclic olefin monomers and non-cyclic olefin monomers. and addition polymers obtained by copolymerizing the above. However, a single addition polymer of only one cyclic olefin monomer is not preferred.
Methods for producing cyclic olefin resins include a method of hydrogenating a ring-opening metathesis polymer of a norbornene compound, a method of copolymerizing two or more cyclic olefin monomers, and a method of copolymerizing a cyclic olefin monomer and an α-olefin. method.

Among cyclic olefin resins, the basic structure of a polymer obtained by hydrogenating a ring-opening metathesis polymer of a norbornene compound includes, for example, the following formula (I). That is, the formula (I) is described as a polymer in which cyclic skeletons and ethylene skeletons are alternately arranged. The cyclic skeleton of formula (1) is a 1,3-cyclopentylene skeleton. However, the ring-opening metathesis polymer itself of the norbornene compound need not be a copolymer.

In Formula (I), n is an integer of 1 or more, and R ¹ and R ² represent a hydrogen atom or an alkyl group. R ¹ and R ² may be the same or different. R ¹ and R ² may combine with each other to form a ring.

In the structure shown in formula (I), the substituents R ¹ and R ² possessed by n 1,3-cyclopentylene skeletons are the same, and the ring-opening metathesis polymer of the norbornene compound is a homopolymer (homopolymer). It is not limited to the case where The structure represented by formula (I) may be a polymer obtained by hydrogenating ring-opening metathesis polymers of two or more norbornene compounds. Examples thereof include the following formula (II).

In formula (II), m and n are integers of 1 or more, and R ¹ and R ² represent a hydrogen atom or an alkyl group. m and n may be the same or different. R ¹ and R ² may be the same or different. R ¹ and R ² may combine with each other to form a ring.

Specific examples of polymers obtained by hydrogenating ring-opening metathesis polymers of norbornene compounds include "ZEONEX (registered trademark)" and "ZEONOR (registered trademark)" manufactured by Zeon Corporation.

Moreover, the following formula (III) is mentioned as an addition polymer which copolymerized the cyclic olefin monomer and the non-cyclic olefin monomer. Copolymers of formula (III) are described as polymers in which the cyclic and ethylene backbones are randomly arranged. The cyclic skeleton of formula (I1I) is a 2,3-norbornanylene skeleton.

In formula (III), m and n are integers of 1 or more, and R ¹ , R ² and R ³ each represent a hydrogen atom or an alkyl group. m and n may be the same or different. R ¹ , R ² and R ³ may be the same or different. R ¹ and R ² may combine with each other to form a ring.

Here, as a polymer in which R ¹ , R ² and R ³ are all hydrogen atoms, “TOPAS (registered trademark)” manufactured by Polyplastics Co., Ltd. can be mentioned. Further, examples of polymers in which R ¹ and R 2 are alkyl groups and R ³ is a hydrogen atom include “APEL (registered trademark)” manufactured by Mitsui Chemicals, Inc.

These cyclic olefin resins have excellent water vapor barrier properties and are readily available. As described above, in the laminate of the present embodiment, these cyclic olefin resins can be used as the main component of the cyclic olefin resin layer. The cyclic olefin resin layer may contain one cyclic olefin resin or two or more cyclic olefin resins. Here, the two or more cyclic olefin-based resins may be two or more cyclic olefin-based resins corresponding to any one of the formulas (I) to (III). ) may be one or more cyclic olefin-based resins for each of two or more formulas, and may further include cyclic olefin-based resins that do not correspond to formulas (I) to (III). Moreover, the cyclic olefin resin layer may be the innermost layer (sealant layer) in the laminate.

Next, commercially available cyclic olefin resins are exemplified. Although partly overlaps with the above, for example, ZEONEX (registered trademark) (manufactured by Nippon Zeon Co., Ltd., hydrogenated polymer of ring-opening metathesis polymer of norbornene-based monomer), TOPAS (registered trademark) (manufactured by Polyplastics Co., Ltd.) , a copolymer of norbornene and ethylene), ZEONOR (registered trademark) (manufactured by Nippon Zeon Co., Ltd., a copolymer based on ring-opening polymerization of dicyclopentadiene and tetracyclopentadodecene), APEL (registered trademark) (Mitsui Chemicals, Inc. Copolymer of ethylene and tetracyclododecene, manufactured by JSR Corporation), Arton (registered trademark) (a cyclic olefin resin containing a polar group made from dicyclopentadiene and methacrylic acid ester, manufactured by JSR Corporation), and the like.

The cyclic olefin-based resin layer may contain other resin components in addition to the cyclic olefin-based resin. Other resin components that may be contained in the cyclic olefin resin include polyethylene, polypropylene, polybutene, ethylene/α-olefin copolymer, ethylene/(meth)acrylic acid copolymer, and ethylene/vinyl acetate copolymer. , Polyolefin resins such as ethylene/(meth)acrylic acid ester copolymers, urethane resins, rubber resins, polyester resins, polyester urethane resins, acrylic resins, amide resins, styrene resins, silane resins etc. 1 type, or 2 or more types are mentioned. Among these, examples of styrene-based resins include polystyrene, styrene-acrylonitrile copolymer (SAN), and styrene-based elastomers. Among them, in particular, styrene-butadiene block copolymers, styrene-butadiene-styrene block copolymers, styrene-isoprene block copolymers, styrene-isoprene-styrene block copolymers, hydrogenated products thereof (e.g., SEBS, SEPS, etc.), styrene-butadiene random It is preferable that the cyclic olefin-based resin layer contains one or more of copolymers in the range of 0.05 to 20% by mass.
When other resin components are contained, it is possible to improve the desired performance of the container, such as impact resistance at low temperatures, maintenance of transparency immediately after autoclave sterilization, and improvement of flexibility.

The cyclic olefin-based resin layer preferably contains only a cyclic olefin-based resin as a resin component (may contain additives other than resins), and may contain 100% by mass of the cyclic olefin-based resin (additives may also be added). Not included). When the other resin components mentioned above are included, the cyclic olefin-based resin layer is mainly composed of a cyclic olefin-based resin, that is, one type of cyclic olefin-based resin or two or more types of cyclic olefin-based resins totaling 50% by mass. It is preferably contained in an amount of 70% by mass or more, and particularly preferably in an amount of 70% by mass or more. If the composition ratio of the cyclic olefin-based resin is low, trace components and drug components that have a high affinity for plastics may be adsorbed, resulting in insufficient storage stability of the contained drug components.

In order to improve the appearance of the container, stabilize the quality, and provide other required performance, , various additives such as antioxidants, ultraviolet absorbers, antistatic agents, lubricants, antiblocking agents, etc. may be contained within a range that does not impair safety and hygiene.

The method for forming each layer (film) used in the laminate (sheet) of the present embodiment is not particularly limited, but examples thereof include T-die forming and inflation forming. After the T-die molding, the film, sheet, etc. may be quenched with a cooling roll. In the case of continuously forming a long film, sheet, or the like, it is preferable to roll up the long formed body such as the film or sheet after forming, since it is excellent in productivity.

The laminate is exemplified by a configuration in which a substrate, a sealant layer, and optionally other layers are laminated. That is, an adhesive layer or an anchor layer may be interposed between the layers, or the layers may be laminated so as to be in direct contact with each other. As other layers, one layer or multiple layers such as a reinforcing layer, a gas barrier layer, a light shielding layer, and a printing layer can be appropriately selected. The sealant layer is a layer used for heat sealing, and is arranged as the innermost layer in contact with the contents as a packaging material. Heat sealing is a method of bonding by melting a sealant layer, but there are no particular restrictions on the sealing method, and hot plate sealing, ultrasonic sealing, high frequency sealing, impulse sealing and the like can be used. The substrate may be the other outermost surface of the laminate opposite to the sealant layer, or may be laminated inside the other outermost surface.

The method for producing the laminate of the present embodiment is not particularly limited, and each layer constituting the laminate is formed by an extrusion lamination method, a dry lamination method, a co-extrusion method, or a combination of two or more of these methods. Layers may be appropriately laminated. The thickness of the sealant layer depends on the use of the packaging material and is not particularly limited, but is usually about 5-150 μm, preferably 15-80 μm. Although the thickness of the adhesive layer is not particularly limited, it is, for example, 10 to 100 μm.

When the three layers of the cyclic olefin resin layer, the adhesive layer, and the polypropylene resin layer of the laminate are laminated by a co-extrusion method, these three layers are laminated without interposing an adhesive layer or an anchor layer. be done. The laminate may include five layers of cyclic olefin-based resin layer/adhesive layer/polypropylene-based resin layer/adhesive layer/cyclic olefin-based resin layer, and polypropylene-based resin layer/adhesive layer/cyclic olefin-based resin layer/adhesive layer. / Five layers of polypropylene-based resin layers may be included.

According to the laminate of the present embodiment, the interlaminar strength between the cyclic olefin resin layer and the adhesive layer and the interlaminar strength between the polypropylene resin layer and the adhesive layer can be greatly improved.
Moreover, the laminate of the present embodiment has higher heat resistance than a laminate composed of a polyethylene-based resin layer and a cyclic olefin-based resin layer. Therefore, it has heat resistance even at high temperatures exceeding 120° C., and high-pressure steam sterilization is also possible.
In addition, the laminate of the present embodiment has higher heat resistance than a laminate composed of a polypropylene-based resin layer and a cyclic olefin-based resin layer, and has a high peel strength even after high-pressure steam sterilization. A decrease can be suppressed, and the impact resistance of the container can be improved.

The container of this embodiment can be formed using the laminate of this embodiment. Examples of containers include packaging bags (pouches) and tube packaging. When the packaging bag is provided with a spout, the spout can be suitably used as long as it can be bonded to the sealant layer of the laminate constituting the packaging bag to ensure sealing performance. Preferably, the sealant layer of the laminate and the spout made of a heat-sealable resin are used, and the spout and the laminate are joined by heat sealing. When heat-sealing the laminate and the spout, the spout may be heat-sealed by inserting the spout between the stacked laminates with the sealant layer on the inside. A base portion may be provided, and this flange portion or fusion base portion may be heat-sealed with the periphery of the hole provided in the laminate or the inner surface of the opening of the packaging bag.

The container of this embodiment can be suitably used as a container for storing medicines, food and drink, cosmetics, and the like. The drug may be a substance that is highly adsorbable or permeable to common resins, such as nitroglycerin, albumin, vitamins, trace elements, radical scavengers, and the like.
The forms of packaging bags include small packaging bags (pouches) such as three-sided bags, four-sided bags, gusseted bags, gusset bags, and self-supporting bags, as well as large bags such as inner bags for bag-in-boxes and inner bags for drums. , is applicable without particular limitation.

Although the present invention has been described above based on preferred embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

EXAMPLES The present invention will be specifically described below with reference to examples.

(Laminate manufacturing method)
Using a T-die multilayer film forming machine, a laminate was produced by a co-extrusion method so that the thicknesses of the surface layer/intermediate layer/innermost layer were 180 μm/50 μm/30 μm, respectively.
For the surface layer, a polypropylene-based thermoplastic elastomer "Xerus (registered trademark)" (manufactured by Mitsubishi Chemical Corporation, density 0.89 g/cm ³ , melting peak temperature 162°C) was used. A cyclic olefin polymer "ZEONEX (registered trademark)" (manufactured by Nippon Zeon Co., Ltd., density 1.02 g/cm ³ , glass transition temperature 136°C) was used for the innermost layer.

Pellets obtained by dry-blending three components consisting of LLDPE, polypropylene (PP), and an elastomer (compatibilizer) at a predetermined ratio were used for the intermediate layer.
As the LLDPE, vapor-phase metallocene polyethylene "Harmolex (registered trademark)" (manufactured by Nippon Polyethylene Co., Ltd., density 0.908 g/cm ³ , melting peak temperature 120°C) was used.
As the PP, metallocene polypropylene "Wintech (registered trademark)" (manufactured by Japan Polypropylene Corporation, density 0.90 g/cm ³ , melting peak temperature 125°C) was used.
As the elastomer, thermoplastic elastomers shown in Table 1 below were used.

As the four types of SEBS (styrene-ethylene-butylene-styrene block copolymer), "Tuftec (registered trademark)" (manufactured by Asahi Kasei Corporation, styrene content: 12 to 43% by weight) was used.
As SEPS (styrene-ethylene-propylene-styrene block copolymer), "Septon (registered trademark)" (manufactured by Kuraray Co., Ltd., styrene content: 18% by weight) was used.
SEBC (styrene-ethylene-butylene-olefin crystal block copolymer), HSBR (hydrogenated styrene-butadiene rubber), and CEBC (olefin crystal-ethylene-butylene-olefin crystal block copolymer) are DYNARON (Registered Trademark)” (manufactured by JSR Corporation) was used.

(First Experimental Example)
A laminate having an intermediate layer having the composition shown in Table 2 was produced using the method for producing a laminate described above. Using the film-formed laminate, the innermost layers were superimposed, and the outer periphery of the laminate except for the filling port was heat-sealed to prepare an infusion bag-shaped pouch container with outer dimensions of 172 mm×115 mm. After trimming so that the peripheral seal width was 5 mm, the inside of the pouch was filled with 105 mL of water, and then the filling port was heat-sealed to seal the pouch.

The sealed pouch was subjected to autoclave sterilization using an autoclave at 121° C. for 20 minutes. After the high-pressure sterilization, the temperature of the pouch was quickly lowered with cooling water, and then the heat seal strength and interlayer adhesive strength of the pouch were measured.

The heat seal strength was measured by the following procedure. First, a test piece having a width of 15.0 mm and a developed length of 100 mm or more is taken in a direction perpendicular to the heat-sealed portion of the pouch, and the heat-sealed portion of the test piece is placed in the center, and the sheet portions on both sides of the heat-sealed portion are turned 180°. Each sheet portion on both sides was attached to the grip portion of a tensile tester with a grip interval of 50 mm. Next, the tensile load was measured at a constant tensile speed of 300 mm/min until the heat-sealed portion broke, and the maximum load (N/15 mm) until breakage was defined as the heat-seal strength.
Regarding the evaluation of heat seal strength, considering JIS Z0238 (test method for heat seal flexible packaging bags and semi-rigid containers), 23 N / 15 mm of "when strong heat seal strength is required for retort sterilization bags" More than that was evaluated as "good", and less than that was evaluated as "bad".

The interlayer adhesive strength was measured by the following procedure. First, the non-heat-sealed sheet portion of the pouch was cut into pieces of 15 mm wide by 150 mm long, and ethyl acetate was used to separate part of the interlayer from one end of the sheet. It was developed until the length of the separation between the layers became 20 mm or more, and both ends where the layers were separated were attached to grips of a tensile tester. Next, a tensile load was applied at a tensile speed of 5 mm/min to delaminate a length of 30 mm, and the average load (N/15 mm) was taken as the interlayer adhesion strength.
Regarding the evaluation of the interlayer adhesive strength, with reference to the results of packaging products, 10 N/15 mm or more was evaluated as "good", and less than that as "poor".

When measuring the interlaminar bond strength of the pouch, the separated peel surface was observed. Table 3 shows the results of heat seal strength, interlayer adhesive strength, and peel surface of the pouch.

When the styrene elastomer is added (number 1- 7 to 1-12) showed a tendency to significantly increase the values of heat seal strength and interlayer adhesive strength before and after sterilization. In addition, the degree of decrease in strength after sterilization compared to before sterilization was smaller when the styrene elastomer was added than when the styrene elastomer was not added, and the performance as a container was improved.

When PP accounts for most of the composition of the intermediate layer, the peeled surface tends to be "intermediate layer/innermost layer". When the intermediate layer contained LLDPE at a rate of 40% by mass or more (Nos. 1-9 to 1-12), the heat seal strength was at a good level exceeding the standard value.
On the other hand, when LLDPE accounts for most of the composition of the intermediate layer, the peeled surface tends to be "surface layer/intermediate layer". When the intermediate layer consisted of two components of LLDPE and SEBS (Nos. 1-12), the interlayer adhesive strength after sterilization was less than 10 N/15 mm.

From the viewpoint of suppressing interlayer separation (delamination) even if the interlayer adhesion strength gradually decreases during long-term storage as a soft bag formulation and maintaining the commercial value of the formulation including its appearance, the interlayer adhesion strength after sterilization is improved. High is preferred. Therefore, the ratio of LLDPE and (PP+SEBS) constituting the intermediate layer is preferably 40:60 to 95:5, more preferably 40:60 to 80:20. In Table 3, when a styrene-based elastomer was added, when the ratio of LLDPE to PP was 40:50 to 60:30, it became "non-peelable", indicating extremely excellent performance.

(Second experimental example)
A laminate having an intermediate layer having the composition shown in Table 4 was produced in order to verify the case where the amount of elastomer added to the intermediate layer was changed from 10% by weight. Other procedures (pouch production, sterilization, measurement of heat seal strength and interlayer adhesive strength) were the same as in the first experimental example.

Table 5 shows the results of heat seal strength, interlayer adhesive strength, and peeled surface of the pouch in the second experimental example.

When the amount of elastomer added to the intermediate layer was 5% by weight (Nos. 2-1 to 2-6), the values of heat seal strength and interlayer adhesive strength tended to increase overall. Considering together with the case of adding 10% by weight of elastomer to the intermediate layer in the first experimental example (Nos. 1-7 to 1-14), when the amount of LLDPE added to the intermediate layer is too small, the heat after sterilization It is believed that the seal strength and interlayer bond strength values do not increase significantly. On the other hand, if the amount of PP added to the intermediate layer is too small, the heat-sealing strength is maintained at a sufficient level even after sterilization, but the interlaminar adhesive strength is significantly lowered. For this reason, it is desirable that the intermediate layer contains three components, LLDPE, PP, and an elastomer, in an appropriate ratio.

(Third experimental example)
Laminates having intermediate layers having the compositions shown in Table 6 were produced in order to verify the case where the type of elastomer or styrene content in the intermediate layer was changed. Other procedures (pouch production, sterilization, measurement of heat seal strength and interlayer adhesive strength) were the same as in the first experimental example. For comparison, Tables 6 and 7 also show numbers 1-9 and 1-3 according to the first experimental example.

Table 7 shows the results of heat seal strength, interlayer adhesive strength, and peel surface of the pouch in the third experimental example.

Elastomers that could improve interlayer adhesion strength to the extent that they could not be peeled off after sterilization were SEBS (Nos. 1-9 and 3-1) with a styrene content of 18% by weight or less. When SEBS with a styrene content of 30% by weight or more is added to the intermediate layer as an elastomer (Nos. 3-2 and 3-3), the heat seal strength after sterilization is 23 N/15 mm or more according to the above JIS standard, but The numerical value was lower than that of Nos. 1-9 and 3-1.
Even when a styrenic elastomer other than SEBS was used (Nos. 3-4 to 3-6), a certain performance improvement effect was observed. However, when CEBC was used as an elastomer containing no styrene block (Nos. 3-7), the results were not significantly different from when no elastomer was added to the intermediate layer (Nos. 1-3).
This suggests that it is necessary to add a styrenic elastomer to the intermediate layer in order to improve the heat seal strength and interlayer adhesive strength.

Claims (6)

A laminate of at least three layers including a structure in which a cyclic olefin-based resin layer, an adhesive layer, and a polypropylene-based resin layer are laminated in this order,
The resin component contained in the adhesive layer is substantially composed of three components, a linear low-density polyethylene, a styrene-based elastomer, and a polypropylene-based resin. The proportion of linear low-density polyethylene is 20 to 95 parts by weight, and the ratio of (styrene-based elastomer):(polypropylene-based resin) in the adhesive layer is 25/3:275/3 to 50/3 as a weight ratio. A laminate characterized in that it is within the range of 250/3. 2. The laminate according to claim 1 , wherein the styrene-based elastomer is one or more selected from SEBS, SEPS, SEBC, and HSBR. 3. The laminate according to claim 1, wherein the styrene-based elastomer is SEBS. The laminate according to any one of claims 1 to 3, wherein the styrene content in the styrene elastomer is 10 to 50% by weight. Claims 1 to 4, wherein the polypropylene resin contained in the adhesive layer is a propylene copolymer obtained by copolymerizing at least one of ethylene and α-olefin having 4 to 8 carbon atoms. The laminate according to any one of the above. A container formed using the laminate according to any one of claims 1 to 5 .