JPH0977132A - Soft package excellent in bag fracture resistance and impact resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soft package having excellent heat resistance, sealing strength, and impact resistance, by using a laminate body in which a layer comprising as its main constituent a syndiotactic propylene polymer having a specific percentage of racemipentad is disposed inside a layer made of a material having a high elastic modulus. SOLUTION: A package uses a laminate body 1 in which at least one layer 4, comprising as its main constituent a syndiotactic propylene polymer having a racemipentad (rrrr) percentage of 75% or more, is disposed inside layers 2 and 3 made of materials having elastic moduli higher than that of the layer 4. In this case, in the layer 4 comprising the syndiotactic propylene polymer as the main constituent, a propylene polymer having no spherulites with a diameter of 10μ or more is used. The layer 4 is formed so as to have a crystallinity rate (Δ) of 80% or more, the crystallinity rate (Δ) being defined by Δ=αc/αmax ×100 (where αmax is a thin recess crystallinity degree and a quantity of heat required for crystalline melting per unit weight of a sample, and αc is a quantity of heat required for the crystalline melting of the corresponding layer).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible package made of a laminate of a propylene-based polymer, and more specifically to bag-breaking resistance, impact resistance, stress cracking resistance, bending resistance, etc. Relates to flexible packaging that has dramatically improved.

[0002]

2. Description of the Related Art In addition to packaging of rigid containers made of metal, glass, plastic, etc. for packaging foods, etc.
Flexible packaging is also widely used. This flexible packaging has the advantages that it is lightweight and that it is easy to dispose of the packaging container after use.

In the case of flexible packaging, even though it is a thin film or sheet, it is used in the form of a laminate obtained by laminating a plurality of flexible materials having various functions, so that excellent gas barrier properties, sealing reliability, and There is an advantage that various required functions such as strength and heat sealability can be sufficiently brought out.

Conventionally, various kinds of olefin resins such as polyethylene and polypropylene have been widely used as the inner surface material of flexible packaging from the viewpoint of heat sealability and hygienic properties. However, heat sterilization of contents such as retort sterilization is performed. Polypropylene, i.e. isotactic polypropylene, is commonly used for the applications it makes.

In Japanese Patent Publication No. 53-31437, an isotactic polypropylene, particularly a sterilizing agent, is used as an inner layer material for a high temperature short time sterilized food package, and its crystal form is a smectic crystal with an orientation degree of 0.7 or less. It is described that one is used.

[0006]

However, the isotactic polypropylene conventionally used as the inner layer material is prone to spherulite growth due to the heat history during or after packaging production, or with the passage of time thereafter, resulting in brittleness. There are drawbacks such as bag breakage due to impact, easy breakage of the heat-sealed portion, and stress cracking.

This tendency is particularly remarkable in unstretched cast polypropylene film (CPP), while stretched polypropylene film (OPP) is
Even if it is relatively excellent in heat stability, the heat seal temperature range is extremely narrow, and even if it is strongly heat sealed,
The heat-sealed portion has the same problem as the CPP film.

In order to prevent these problems, it is known that polypropylene is blended with various elastomers or propylene copolymers are used, but with these means, the heat resistance inherent in polypropylene is lowered,
Furthermore, the effect of improving impact resistance and heat seal strength is still insufficient.

Therefore, an object of the present invention is to provide a flexible packaging having a propylene polymer as an inner layer material, which has excellent heat resistance and is significantly improved in seal strength and impact resistance (bag breaking strength). It is in providing packaging.

[0010]

According to the present invention, a racemic pentad (rrrr, sometimes simply abbreviated as r ₄ hereinafter) syndiotactic propylene polymer having a fraction of 75% or more is mainly used. At least one layer,
There is provided a flexible package characterized by being constituted by a laminated body disposed on the inner surface side of a layer made of a material having a higher elastic modulus than itself.

The layer mainly composed of syndiotactic propylene polymer is a propylene polymer having a spherulite structure having a diameter of 10 μm or more, that is, having no spherulite structure or having a spherulite structure diameter. Is preferably less than 10 μm.

The layer containing a syndiotactic propylene polymer as a main component is represented by the following formula (1) Δ = αc / α _max × 100 (1) In the formula, α _max is the maximum crystallinity, A differential scanning calorimeter measures the temperature of the sample at 200 ° C. at 10 ° C./10 min, holds at the observed exothermic peak temperature for 10 minutes, and then measures the temperature at room temperature at 10 ° C./min again. The crystallization rate (Δ) defined by is the heat of crystal fusion (kJ) per unit weight (mg) of the sample, and αc is the heat of crystal fusion of the corresponding layer measured in the same manner without the hold. It is preferably 80% or more from the viewpoint of stability over time, and preferably has a birefringence of 1.5 × 10 ⁻³ or less from the viewpoint of heat sealability.

As a material having a high elastic modulus, a metal foil or a resin film having stretch orientation is used alone or in combination.

[0014]

In the present invention, a layer mainly composed of syndiotactic propylene polymer having a racemic pentad fraction (rrrr) of 75% or more, particularly 80% or more is selected as the inner surface material of the flexible packaging, and this layer is used as the inner surface material. The feature is that they are combined on the inner surface side of a layer of a material having higher elasticity than itself.

In the propylene polymer chain, particularly in the repeating unit of α-olefin such as propylene, the carbon atom at the base of the side chain alkyl group such as methyl group is an asymmetric carbon, and the arrangement is meso (m). And a racemic (r), the racemic pentad fraction (rrrr) means the racemic (r) in the polymer chain.
Is a fraction of four of which are lined up, and the measurement is performed by, for example, R.I. C. Ferguson, Macromolecules, 4 , 32
4 (1971), the high resolution proton m
The magnetic resonance (pmr) method can be used, and it is important that the value is 75% or more, particularly 80% or more from the viewpoint of heat resistance and the like.

That is, as shown in the examples described later, when the racemic pentad fraction is less than 75%, the syndiotactic propylene polymer causes a problem in heat resistance such as blocking between inner layers. However, when the ratio is within the range of the present invention, there is no problem in heat resistance.

Generally, in the syndiotactic propylene-based polymer, the heat distortion temperature is improved as the racemic pentad fraction (rrrr) is increased, and at rrrr of 75% or more, isotactic random polypropylene or isotactic block is used.・ A heat distortion temperature (80 ℃ or higher) almost equal to that of polypropylene etc. is obtained, and at rrrr 90% or higher, heat distortion temperature equivalent to isotactic homopolypropylene (about 112 ℃)
The above heat distortion temperature can be obtained.

Further, in terms of enhancing the sealing strength and bag drop strength of the laminate, rrrr is 75% or more, particularly 80%.
The above is critical, and this fact becomes clear by referring to the example described later.

In the conventional packaging using an isotactic propylene polymer, particularly isotactic polypropylene, not only the seal strength is generally low, but also the drop strength of the bag due to heat sealing is significantly lowered. This is because coarse spherulites are generated in the vicinity of the seal portion (this can be confirmed by a polarization microscope) and embrittlement occurs.
When a random or block copolymer is used, the seal strength is significantly improved compared to the case where a homopolymer is used, but spherulites still tend to be generated in the vicinity of the seal portion, and the drop-bag strength is high. Especially, the drop bag strength at a low temperature of about 5 ° C. is not yet sufficiently satisfactory. Further, in the conventional isotactic polypropylene-based film, from the viewpoint of maintaining impact resistance, imparting a certain degree of molecular orientation during film formation such as T-die and inflation, and maintaining it even after lamination. Must be,
Therefore, it is necessary to set the birefringence constant, and therefore, the temperature setting with high heat sealability is required.

On the other hand, when the syndiotactic propylene polymer is used as the inner layer material according to the present invention, not only excellent seal strength is obtained, but also coarse spherulites are suppressed in the vicinity of the seal portion. As a result, the drop bag strength is significantly improved.

The syndiotactic propylene polymer used in the present invention has a very small spherulite size and a low crystallinity, and has no spherulite structure or, if at all, a microcrystalline spherulite having a diameter of less than 10 μm. Is. In addition, as shown in the following examples, even if the film once formed and laminated has no large spherulites even when the molecular orientation is reduced or eliminated by a melting process or the like, the impact resistance is high. The feature is that the decrease is small.

The syndiotactic propylene-based polymer forming the inner layer has a crystallization rate Δ defined by the above formula (1) of 80% or more, and this inner layer is crystallographically stable, and is heat-treated or The density change with time is small, and the internal strain is small, and it is stable as a flexible package with time. Further, the birefringence is preferably 1.5 × 10 ⁻³ or less from the viewpoint of heat sealability.

The syndiotactic propylene-based polymer used in the present invention has a flexural modulus lower than that of the isotactic propylene-based polymer and is about half or less depending on the copolymer composition, and is excellent in flexibility and flexibility. Gives the advantage of being.

That is, when heat-sealing a flexible package, foreign substances such as contents are often attached to the heat-sealing surface, and it is necessary to completely bury such inclusions in the heat-sealing resin. Important in terms of reliability,
For this purpose, it is necessary to provide the heat-sealable resin in a considerably large thickness, but the packaging of the present invention has an advantage that the flexibility and flexibility are not impaired even if the inner layer material is provided in a large thickness.

Since the layer mainly composed of the syndiotactic propylene polymer is provided on the inner surface side of a material having a higher elastic modulus than that, for example, a metal foil or a resin film having stretch orientation, this elastic modulus is used. Even if the inner layer is flexible, the material having a high temperature serves as a stress carrier, and plastic deformation of the packaging itself during normal handling is prevented, and sufficient strength can be obtained. Further, the syndiotactic propylene-based polymer used in the present invention is substantially less in hexane extract and the like as compared with the conventional isotactic propylene-based polymer. Inside the barrier material,
Especially when it is used as the innermost surface, a packaging material having excellent flavor properties with less elution into the contents is provided. Also,
When used on the innermost surface, a flexible packaging material suitable for γ-ray sterilization is provided.

[0026]

FIG. 1 shows an example of the flexible packaging of the present invention.
In the above, the laminate 1 is provided with an outer layer 2 of a stretched and oriented resin film, a gas barrier intermediate layer 3 and a syndiotactic propylene polymer layer 4.
The outer layer 2 and the inner layer 4 are provided on both sides of the intermediate layer 3 with adhesive layers 5a,
It is provided via 5b.

In FIG. 2 showing another example of the multilayer structure of flexible packaging, the laminate 1 is the same as FIG. 1 except that the outer layer 2 of the stretched and oriented resin film and the gas barrier intermediate layer 3 are provided.
And a syndiotactic propylene-based polymer inner layer 4, and an innermost layer 6 of a heat-sealable resin having an easy-peel property for providing an easy-peel interface inside the syndiotactic propylene-based polymer layer 4. Has been.

The syndiotactic propylene polymer used in the present invention has a racemic pentad (rrrr) fraction of 75% or more, particularly 80% or more, which is a method known per se, for example, metallocene. It is obtained by polymerizing an olefin using a system compound and an aluminoxane compound as a catalyst.

The syndiotactic propylene polymer is more preferably a homopolymer of propylene, but propylene as the main monomer and ethylene as the comonomer and / or the formula CH ₂ ═CHR (wherein R is Is an alkyl group having 2 to 8 carbon atoms), particularly a copolymer containing less than 15% by weight can be used. Examples of α-olefins other than propylene include butene-1, pentene-1, hexene-1, octene-1, 4-methylpentene-1, and the like. These copolymers are random copolymers or blocks. It may be a copolymer.

The melt flow rate (MFR) of the syndiotactic propylene polymer is not particularly limited, but it is generally preferable to be in the range of 0.5 to 50 g / 10 min, while the density is 0.87 to 0. 92 g / cm
^It should be in the range of ³ .

This syndiotactic propylene polymer can be used alone as an inner layer of a laminate, or can be used in a blend with another polymer.
When used in a blend, the syndiotactic propylene-based polymer preferably accounts for 50% by weight or more, and particularly 70% by weight or more of the whole. Further, as a modified polymer obtained by graft-polymerizing an ethylenically unsaturated carboxylic acid or acid anhydride using this syndiotactic propylene polymer as a trunk polymer, adhesion between a metal foil or a resin film having stretch orientation and an inner resin layer It can also be used as the main component of the resin layer.

Examples of other polymers include olefin resins other than the syndiotactic propylene polymer of the present invention, such as low-, medium- or high-density polyethylene, isotactic polypropylene, linear low density polyethylene and ethylene. -Propylene copolymer, polybutene-1,
Ethylene-butene-1 copolymer, propylene-butene-
1 copolymer, ethylene-propylene-butene-1 copolymer, ethylene-vinyl acetate copolymer, ion-crosslinked olefin copolymer (ionomer), ethylene-acrylic acid ester copolymer, etc .; elastomeric polymer such as nitrile -Butadiene rubber (NBR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), polybutadiene (BR), polyisoprene (IR), butyl rubber, natural rubber, ethylene-propylene rubber (EPR),
Ethylene-propylene-diene rubber (EPDM), polyurethane, silicone rubber, acrylic rubber, etc .; thermoplastic elastomers such as styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, hydrogenated styrene-butadiene-styrene. Examples thereof include block copolymers and hydrogenated styrene-isoprene-styrene block copolymers. Among these, hydrocarbon-based elastomers, particularly EPR and EPDM, are preferable.

The layer containing the syndiotactic propylene polymer as a main component differs depending on the use,
Generally, it is preferable to use it with a thickness of 1 to 200 μm, and particularly 3 to 120 μm. When arranging this layer on the inner surface side of a material with a high elastic modulus, it can be used as the innermost surface layer,
It can also be arranged in the middle.

As the layer having a high elastic modulus which is used in combination with the syndiotactic propylene polymer layer, an oxygen barrier layer or a resin layer having stretch orientation is used, and generally, both are used in combination. Is preferred, but the use of either alone is not excluded.

As the oxygen barrier intermediate layer, a metal foil or an oxygen barrier resin layer is used. A metal foil is particularly suitable in terms of oxygen barrier property and high rigidity.

As the metal foil, various surface-treated steel foils and
Light metal foil such as aluminum is used. Surface treated steel foil
As an example, after cold-rolled steel sheet is annealed, secondary cold-rolled,
Kick, tin plating, nickel plating, electrolytic chromic acid treatment,
Performed one or more surface treatments such as chromic acid treatment
Any thing can be used. An example of a suitable surface treated steel foil
Is an electrolytic chromic acid treated steel foil, especially 10 to 200
mg / m²1 to 50 mg / m with metallic chromium layer²(Money
With a chromium oxide layer (converted to genus chromium)
This is a combination of adhesiveness with resin and corrosion resistance.
Are better. Other examples of surface treated steel foil include 0.6 to 1
1.2 g / m²It is a hard tin foil with a tin plating amount of
You. This tin foil has a chromium content of 1 in terms of metallic chromium.
To 30 mg / m ²Chromic acid treatment or black
It is desirable that romic acid / phosphoric acid treatment is performed. Light
In addition to so-called pure aluminum foil, aluminum foil can be used as metal foil.
Um alloy foil is used. Excellent in terms of corrosion resistance and workability
The aluminum alloy foil produced has a Mn of 0.2 to 1.5 weight.
%, Mg: 0.8 to 5% by weight, Zn: 0.25 to
0.3% by weight, and Cu: 0.16 to 0.26% by weight
%, With the balance being Al. These light
The metal foil also has a chromium content of 20 to 30 in terms of metal chromium.
0mg / m²Chromic acid treatment or chromic acid
/ It is desirable that phosphoric acid treatment is performed.

Although the thickness of the metal foil varies depending on the kind of metal, the use or size of the flexible packaging, it is preferable that the thickness of the metal foil is generally 3 to 150 μm, particularly 5 to 120 μm.

As the gas barrier resin, ethylene-
A vinyl alcohol copolymer can be mentioned, for example, an ethylene-vinyl acetate copolymer having an ethylene content of 20 to 60 mol%, particularly 25 to 50 mol%,
A saponified copolymer obtained by saponification so that the saponification degree is 96 mol% or more, particularly 99 mol% or more is used. The saponified product of ethylene-vinyl alcohol copolymer should have a molecular weight sufficient to form a film, and generally, it is measured at 30 ° C. in a mixed solvent of 85:15 by weight of phenol: water at 0 ° C. 01 dl / g or more,
It is particularly desirable to have a viscosity of 0.05 dl / g or more. Other examples of the gas barrier resin having the above characteristics include polyamides having 5 to 50, especially 6 to 20, amide groups per 100 carbon atoms; for example, nylon 6 and nylon. 6/6, nylon 6/6/6
Copolymer, metaxylylene adipamide, nylon 6/10,
Nylon 11, nylon 12, nylon 13, and semi-aromatic polyamide such as hexamethylene isophthalamide / terephthalamide are used. These polyamides should also have a molecular weight sufficient to form a film and have a relative viscosity (ηrel) of 1.1 or higher, measured at a concentration of 1.0 g / dl in concentrated sulfuric acid and a temperature of 30 ° C., in particular 1. It is preferably 5 or more.

The above gas barrier resin generally varies depending on the amount of oxygen allowed in the package, but is generally 3 to 50.
It is desirable to have a thickness of μm, especially 5 to 30 μm.

A stretched film having a melting temperature higher than that of the syndiotactic propylene polymer is used as the stretchable resin film, and for example, uniaxially or biaxially stretched polyester, polyamide, polycarbonate, polypropylene. Film is used.

Examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate / isophthalate, polyethylene / butylene terephthalate and polyethylene naphthalate. The biaxially stretched polyester film is particularly excellent in terms of rigidity and protective effect.

Examples of the stretched polyamide film include a film obtained by uniaxially or biaxially stretching the nylons described above for the gas barrier resin. This polyamide film has an advantage that it has excellent gas barrier properties as well as mechanical properties and pinhole resistance.

As the polycarbonate, a polycarbonate derived from bisphenols and phosgene is used, and it gives excellent heat resistance even when it is unstretched.

Since the stretched film of isotactic polypropylene has excellent rigidity and heat resistance, it can be used for the purpose of protecting the outer surface.

These stretched films are generally 5 to 40 μm, and especially 10 although they differ depending on the type and layer structure.
It is preferable to have a thickness of 30 to 30 μm.

The laminate used in the flexible packaging of the present invention preferably has a laminate structure in which the gas barrier layer serves as an intermediate layer and the stretched resin film layer serves as an outer layer. This is because the stretched resin film layer serves as a protective layer for the gas barrier layer. Also, in many cases, so-called back printing is performed on the inner surface side of the stretched resin film layer prior to lamination.

In order to impart an easy peel property to the heat seal interface, as shown in FIG. 2, an easy peel heat seal resin layer can be further provided inside the syndiotactic polypropylene layer.

The easy-peel heat-sealing resin layer reduces the cohesive force at the heat-sealing interface, and for example, polypropylene blended with polyethylene is used. As polypropylene, random or block copolymers are used in addition to syndiotactic or isotactic homopolymers. As polyethylene, for example, low-, medium-, or high-density polyethylene, linear low-density polyethylene, etc. are used. The weight ratio of polypropylene to polyethylene is 95: 5 to 5:95, especially 85:15.
It is desirable to be in the range of 15:85.

The easy-peel heat-sealable resin layer preferably has a thickness of generally 0.5 to 30 μm, and particularly 3 to 20 μm.

In some cases, sufficient adhesiveness may not be obtained between the gas barrier layer used and the inner or outer layer resin, but in this case, an adhesive resin layer is interposed between the two.

Examples of such adhesive resin include carboxylic acid, carboxylic anhydride, carboxylic acid In the main chain or side chain of 1 to 700 milliequivalent (meq) / 100 g resin, especially 10 to 500 meq / 1
The thermoplastic resin contained at a concentration of 00 g of resin is mentioned. Suitable examples of the adhesive resin include ethylene-acrylic acid copolymer, ion-crosslinking olefin copolymer, maleic anhydride grafted polyethylene, maleic anhydride grafted polypropylene, acrylic acid grafted propylene polymer,
Ethylene-vinyl acetate copolymer, copolymer polyester,
One or a combination of two or more such as copolyamides. These resins are useful for lamination by coextrusion or sandwich lamination. In addition, for adhesive lamination of the preformed gas barrier layer and the resin film, various adhesive resins such as isocyanate-based or epoxy-based thermosetting type, moisture curing type, ultraviolet curing type or electron beam curing type Also used.

The flexible packaging of the present invention can be manufactured by a method known per se except that it has the above-mentioned layer structure. The laminate used for this flexible packaging can be easily manufactured by a lamination method such as dry lamination, sandwich lamination, and extrusion coating.

For example, a laminate is manufactured by laminating a stretched resin film and a film of syndiotactic propylene polymer on a preformed metal foil. In this case, the syndiotactic propylene-based polymer film preferably has a birefringence of 1.5 × 10 ⁻³ or less, and this film is a cast-molded film using a T-die or a film produced by an inflation method. May be

A laminate can also be produced by extrusion-coating a syndiotactic propylene-based polymer on the metal foil side of a laminate of a metal foil and a stretched resin film and press-bonding this.

Furthermore, a laminate of adhesive resin layer / gas barrier resin layer / adhesive resin layer is extruded between the stretched resin film and the syndiotactic propylene polymer film to produce a laminate by sandwich lamination. You can also

The laminate can be laminated or folded in a bag shape and the periphery thereof can be heat-sealed to form a bag-shaped container. Heat sealing can be performed by a heat sealing bar, high frequency induction heating, ultrasonic sealing, etc.
It can be performed at a temperature of 20 to 250 ° C.

In the flexible packaging of the present invention, the polypropylene inner layer has a diameter of 10 μm or more even in the heat history due to heat adhesion during the production of laminate, the heat history during heat sealing, or the heat history due to hot filling or heat sterilization. The feature is that spherulites are not formed, and this has a remarkable advantage that excellent impact resistance and bag breaking resistance can be obtained. The flexible packaging of the present invention is used in the form of pouches, lids, bag-in-boxes, cups and the like.

[0058]

【Example】

Example 1 Unstretched PP having a film thickness of 70 μm from each material having MFR of 0.8 to 1.0 g / 10 min shown in Table 1 by T die casting method.
(CPP) type film is made, and then biaxially stretched PET, 12 μm / aluminum foil, 7 μm / CP is used.
As a P three-layer composite film, dry lamination is performed using an epoxy urethane solvent-based adhesive between the layers,
A predetermined cure was applied to the pouch packaging material. Then, using an automatic bag-making machine, set the maximum temperature to 240 ℃, 225 ℃, 2
130 × 1 at 125 shots / min, changing to 10 ℃
A pouch with a dimension of 70 mm was prepared. 17 as content liquid
Each of the items in Table 1 was evaluated for a product obtained by filling and sealing 0 ml of water and a 1: 1 mixture of salad oil and performing retort treatment at 125 ° C. for 30 minutes. The seal strength was represented by an arithmetic mean value of 5 points each in the MD and TD directions of the original film. The heat resistance was evaluated by the appearance evaluation of the pouch after the retort. Dropping strength was evaluated by allowing the pouch after retort to stand at 5 ° C. for 1 week and dropping the single piece vertically from 120 cm three times, checking the broken bag, and checking the remaining rate in 100 bags.
In addition, the presence or absence of spherulites and the size of the thin pieces obtained by cutting the cross section of the seal portion of the pouch with a microtome were observed using a polarization microscope. In the table, those in which spherulites of 10 μm or more were not observed were represented by −, those in which spherulites of about 10 μm were observed were represented by ±, and those in which many spherulites of 10 μm or more were observed were represented by + and ++. Also, using a film piece cut out from the pouch, the crystallization rate by DSC,
The birefringence was measured with an Abbe birefringence meter. In the conventional isotactic PP, the homopolymer has a low heat seal strength (Comparative Example 2), and the drop bag strength is remarkably inferior due to the generation of large spherulites near the seal portion. Especially under heat-sealing conditions, the higher the temperature, the worse the tendency becomes. In the case of isotactic random PP (Comparative Example 3), the seal strength is considerably improved, but the drop resistance does not reach the practical level. With the isotactic block PP, a practical level is ensured under specific sealing conditions, but in order to always obtain stable performance, the range of conditions is extremely narrow and still below the practical level. On the other hand, in the case of syndiotactic PP, when the tacticity is low (Comparative Example 1), high seal strength cannot be obtained, and drop resistance still tends to be poor. In addition, it was observed that the inner surfaces of the pouches were blocked and adhered during the retort. With a syndiotacticity of 75% or more, almost stable heat resistance, seal strength and drop resistance can be obtained. Even when the sealing conditions are considerably changed, large spherulites are not generated in the vicinity of the sealing portion, which contributes to secure stable performance of the pouch.

[0059]

[Table 1]

Example 2 For each PP-based material having MFR of 1.2 to 2.0 g / 10 min shown in Table 2, MFR of 1.1 g / 10 min (230 ° C.) of low crystalline ethylene-α-olefin co-weight 5% of the coalescence was added and a CPP film with a film thickness of 60 μm was prepared by the T die casting method.
T, 12 μm / aluminum foil, 7 μm / maleic anhydride modified PP / random PP co-extrusion laminate layer, 10 μm
After obtaining a composite film having m / CPP of 60 μm, a pouch was prepared and evaluated. The biaxially stretched PET and the aluminum foil were dry-laminated with a urethane adhesive as in Example 1 above. After curing, isotactic PP-based maleic anhydride-modified resin adhesive (grafting rate 0.5%, MFR40) and isotactic random PP (ethylene content 4%, MFR13)
At 280 ° C so that the adhesive resin is on the aluminum side,
In addition, co-extrusion sandwich lamination is performed so that CPP is arranged on the random PP side, and a state in which the adhesive resin and aluminum reach almost the same adhesive strength under the condition that the CPP surface is 130 ° C with a heater roll before winding. The heat treatment was performed so that A pouch having the same shape as that of Example 1 above was prepared from the obtained laminated packaging material and its performance was evaluated. In the case of isotactic PP, while the birefringence is lowered by heat treatment, the crystallization rate is remarkably increased, and large spherulites are observed even in the vicinity of the seal portion. Will decrease. On the other hand, when syndiotactic PP is used as the inner surface material (Invention 4 to 6), even if the birefringence is low and the crystallization rate is high, large spherulites are not generated and stable seal strength and drop resistance are obtained. showed that. When the syndiotacticity was low (Comparative Example 5), the blocking and sealing strength during retort was low as in Comparative Example 1 above, and the drop bag strength tended to be slightly inferior.

[0061]

[Table 2]

Example 3 Syndiotactic block PP (ethylene content 4%, MFR 2.0) was used as the inner surface material, and isotactic block PP (ethylene content 4%, MFR) for comparison.
When 1.5) was used as a base resin and the amount of dibenzylidene sorbitol added as a crystal nucleating agent was variously changed, the influence of the crystallization rate and the size of spherulites on the performance of the pouch was examined. As the composite film, a 60 μm CPP film made of these base resins having the same structure as in Example 2 was prepared by the same method, and a pouch was similarly prepared and evaluated. Table 3 shows the results. In the case of isotactic block PP (Comparative Example 9)
-11), the addition of the nucleating agent considerably suppresses the formation of large spherulites, but the heat-sealing tends to increase the spherulites near the sealed portion. Almost all the large spherulites are eliminated by properly selecting the sealing conditions with an added amount showing substantially stable physical properties (Comparative Example 11), but the heat-sealing strength is high probably because the crystallization rate is extremely high. Therefore, the drop resistance is not improved. On the other hand, in the case of syndiotactic block PP (the present invention 7-1
0) Although the crystallization rate is increased by the addition of the engraving agent, the drop resistance is hardly deteriorated and stable performance is secured.

[0063]

[Table 3]

Example 4 Biaxially stretched PET, 12 μm / biaxially stretched nylon, 15 μ
m / aluminum foil, 7μm / maleic anhydride modified PP, 3μ
A composite film of m and syndiotactic random PP, a coextrusion layer of 17 μm, and a total of 20 μm / isotactic block PP, 30 μm was prepared according to the method of Example 2. For the aluminum outer surface, dry lamination with urethane adhesive, then MFR
After co-extruding 1.0 CPP film and laminating by sandwich lamination, CPP surface temperature 1
Heat treatment was performed with a heater roll so that the temperature became 25 ° C. Syndiotactic random PP having an ethylene content of 4%, a tacticity of 90% and an MFR of 10 was coextruded with an adhesive resin at a resin temperature of 280 ° C. at 120 m / min. A pouch was prepared in the same manner as in Example 2, filled with a model solution, subjected to retort sterilization, and evaluated. M. Under the condition of L, 4.6, 4.8,
Good as 4.8, drop bag strength of 97, 98, 99 respectively
And the crystallization rate is 90% and the birefringence is 0.9 × 10 ^−3.
Met. It has been shown that, by disposing one layer without large spherulites on the inner surface side of aluminum, drop resistance and heat seal strength are remarkably improved.

Example 5 In Example 4, as the innermost CPP film, isotactic random PP (ethylene content 8%, MF
R2) and a two-layer two-layer composite film in which 20 wt% of low-density polyethylene was blended with the same resin, a composite film having the same structure was prepared. From this, a capacity of 160 ml using the easy peeling property of the innermost surface material was prepared. Created an easy-open standing pouch. Water and oil model liquids were filled and left at 5 ° C after retort sterilization at 125 ° C for 30 minutes, and then vertically dropped three times from a height of 1.2m, the conventional isotactic with a residual rate of 95%. A remarkable improvement effect was recognized as compared with the case where Tick Random PP was used.

[0066]

According to the present invention, racemic pentad (r
rrr) The syndiotactic propylene polymer having a fraction of 75% or more is used as the inner layer material in combination with the layer of a highly rigid material, so that it has excellent heat resistance, but also has excellent seal strength and impact resistance (breakage). Bag strength),
It was possible to provide a flexible package having excellent flexibility and bending resistance.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a sectional structure of a flexible package of the present invention.

FIG. 2 is a sectional view showing another example of the sectional structure of the flexible packaging of the present invention.

[Explanation of symbols]

 1 Laminate 2 Outer layer of stretched oriented resin film 3 Gas barrier intermediate layer 4 Syndiotactic propylene polymer inner layer 5a, 5b Adhesive layer 6 Easy peel heat-sealing resin innermost layer

Claims (7)

[Claims] 1. A racemic pentad (rrrr) fraction of 75.
% Or more of syndiotactic propylene-based polymer as a main component, and at least one layer is composed of a laminated body disposed on the inner surface side with respect to a layer made of a material having a higher elastic modulus than itself. Flexible packaging. 2. The flexible package according to claim 1, wherein the layer mainly composed of the syndiotactic propylene polymer is a propylene polymer having no spherulites having a diameter of 10 μm or more. 3. A layer mainly composed of a syndiotactic propylene-based polymer has the following formula (1) Δ = α c / α _max × 100 (1) where α _max is the maximum crystallinity. Measured with a differential scanning calorimeter, the sample was heated from 200 ° C at 10 ° C / 10min, held at the exothermic peak temperature observed for 10 minutes, and then heated again from room temperature at 10 ° C / min. Is the heat of crystal fusion (kJ) per unit weight (mg) of the sample, and αc is the heat of crystal fusion of the corresponding layer measured in the same manner without the hold, the crystallization rate (Δ) Is 80% or more.
Flexible packaging as described. 4. The flexible package according to claim 1, wherein the layer mainly composed of the syndiotactic propylene polymer has a birefringence of 1.5 × 10 ⁻³ or less. 5. The flexible package according to claim 1, wherein the syndiotactic propylene-based polymer is polypropylene. 6. A syndiotactic propylene polymer is propylene as a main monomer and ethylene as a comonomer and / or a formula CH ₂ ═CHR (wherein R is an alkyl group having 2 to 8 carbon atoms). ) The flexible packaging according to claim 1, which is a copolymer containing less than 15% by weight. 7. The flexible package according to claim 1, wherein the material having a high elastic modulus is a metal foil or a resin film having stretch orientation.