JP2629114B2 - Multilayer containers and packages - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer container having an intermediate layer of an ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) and inner and outer layers of a moisture-resistant thermoplastic resin, and filling the container with the contents. A sealed container which is subsequently sterilized with hot water or steam and which has improved storage, thermoformability and appearance of the container.

[0002]

2. Description of the Related Art Conventionally, metal cans, various plastic containers of glass bottles, and the like have been used as packaging containers for food packages.
Plastic containers are used as various food packaging containers in terms of impact resistance and cost.

[0003] However, metal cans and glass bottles have zero oxygen permeation as a material, whereas plastic containers generate heat and moisture at the same time as in retort sterilization, which has recently attracted attention as a food distribution form. Under the working conditions, more oxygen than is permissible enters into the container through the vessel wall, causing deterioration of the content food due to oxygen, which is a problem in terms of preservability such as flavor and freshness of the food.

In order to prevent this, a plastic container having a multilayer structure in which EVOH having excellent oxygen permeability is laminated with a thermoplastic resin layer and an adhesive resin layer has been put on the market. At present, there is a problem as described above, and satisfactory performance as a food packaging container has not been obtained.

[0005] That is, in such a multilayer structure, EVOH exhibits good gas barrier properties under low humidity, but in particular, heat and moisture simultaneously act as in retort sterilization treatment, that is, under high temperature and high humidity. In use, moisture penetrates into the EVOH layer through the outer layer,
It has been pointed out that the gas barrier property of the VOH layer is rapidly reduced.

In order to reduce the influence of moisture during retort sterilization and to improve the disadvantage that gas barrier properties are reduced, a multilayer laminate having a protective layer containing a desiccant is disclosed in -170748 and JP-B-62-6508. However, since the water that has entered the protective layer by the retort comes into contact with the gas barrier layer, the water once adsorbed migrates to the gas barrier layer, and there is a concern that the function of the gas barrier layer may be reduced. In addition, the end face of the multilayer laminate is generally exposed, and when subjected to retort sterilization, a protective layer containing a desiccant elutes from the end face, which has a disadvantage that the commercial value is reduced.

[0007] EVO containing an inorganic substance such as talc
A multilayer container provided with a thermoplastic resin layer on at least one surface of the H layer is described in JP-A-61-242841.
According to the method described here, it is not always easy to obtain a package having excellent storage stability after retort sterilization.

By the way, EVOH containing talc is
For example, JP-B-51-21822 and JP-A-62-143.
No. 980 discloses and is known as a composition in which talc is blended with EVOH.
The technical idea of a food package obtained by obtaining a hermetically sealed container for food packaging from a multilayer laminate as a layer and subsequently treating the container under conditions where heat and moisture simultaneously act is not disclosed. Further, Japanese Patent Application Laid-Open No. 1-253442 discloses that a filler such as talc is added to a composition of EVOH and polyamide for 5 to 60 watts.
Although it is described that t% is blended, there is no description about a method satisfying the below-mentioned formula (I) which is a requirement of the present invention, for example, containing a small amount of a phosphate group. Also, JP-A-1-308627 and JP-A-2-17
8344 contains EVOH with 5 to 50% by weight of an inorganic powder such as talc and mica and 3% by weight or more, preferably 5 to 30% by weight of a phosphate compound such as sodium dihydrogen phosphate.
Although the compounding is described, there is no description about a method satisfying the formula (I), for example, a method of including a small amount of a phosphate group. Furthermore, in all of the above-mentioned known documents, there is a region where an inorganic filler such as talc is laminated in the EVOH layer of the body wall material of the container, in which a substantially two-dimensional thin layer is laminated parallel to the container wall surface. There are many,
In addition, the weight average flake diameter of the inorganic filler in the region is 50.
μ or less, and that the weight average aspect ratio is 3 or more is not described.

[0009] Also, EVOH is usually used in the form of a multilayer laminate comprising a thermoplastic resin layer and an adhesive resin layer, and a multilayer laminate (film, sheet, parison, etc.) produced by various methods is used. When performing secondary processing on a container or the like as a multilayer structure for heat stretching, particularly when performing stretch forming at a temperature equal to or lower than the melting point of EVOH, a small crack is generated in the EVOH layer and stretching unevenness such as local uneven thickness occurs. Insufficient moldability lowers the oxygen barrier properties of the molded container. In addition, the appearance of the container became poor, which was extremely inconvenient for use as a container. In particular, in the case of retort sterilization treatment, after the treatment, an appearance defect that a part of the container surface becomes an orange peel pattern occurs in a multilayer container obtained by performing stretch molding below the melting point of EVOH, and use as a container. I was in a situation where I could not endure.

Therefore, various plasticizers have been added to the EVOH layer (JP-A-53-88067) for the purpose of preventing the EVOH layer from being cracked or voided when the film is stretched by heating below the melting point of the EVOH. Or a polyamide resin blend (Japanese Patent Laid-Open No. 52-141785,
However, in order to sufficiently improve the heat-stretching property, it is necessary to add 10 to 20 parts by weight of a plasticizer to 100 parts by weight of EVOH. Great decrease in barrier properties, E
There are many problems such as a decrease in the interlayer adhesion strength with the VOH layer, and it cannot withstand use. On the other hand, the latter has a large number of gel-like substances in the molded product, and has a marked coloring Because it does not stand use.

Further, a container obtained by mixing different types of ethylene-vinyl acetate copolymers in a solution state, saponifying an EVOH composition (Japanese Patent Application Laid-Open No. 61-5752), and subjecting the resultant to heat drawing is characterized in appearance. Although it is thought that a good container can be obtained, there is a drawback that the gas barrier property of the EVOH layer is greatly reduced when used under high heat and high humidity as in the retort treatment sterilization described above.

[0012]

SUMMARY OF THE INVENTION The present invention provides a multi-layer container using a multi-layer laminate having an intermediate layer of EVOH and inner and outer layers of a moisture-resistant thermoplastic resin, which does not have the above-mentioned problems. The present invention provides a package having improved thermoformability, storage stability and appearance of a container, particularly a food package, which has been filled, sealed, and then sterilized under conditions in which heat and moisture act simultaneously.

[0013]

Means for Solving the Problems As a result of intensive studies, the present inventors have determined that a composition comprising EVOH and an inorganic filler, and in which the dispersed state of the inorganic filler is specified, and which satisfies the following (I) is an intermediate. The food package obtained by forming a sealed container using a multilayer laminate having inner and outer layers of a moisture-resistant thermoplastic resin as a layer and then sterilizing it under conditions in which heat and moisture act simultaneously is a content. It was found that there was no deterioration of the product, the appearance of the multilayer container was improved, and the product was an excellent food package. Upon further investigation, surprisingly, E
EV satisfying the following formulas (II) and (III) obtained by saponifying a composition containing two or more ethylene-vinyl ester copolymers having different ethylene contents as VOH.
It has been found that the multilayer laminate using the OH composition has improved thermoformability, and that the appearance of a sealed container using the multilayer laminate is also improved, thereby completing the present invention.

That is, the present invention provides an ethylene content of 20 to
EVOH 50 to 60 mol%, saponification degree 95 mol% or more
In a multilayer container having a resin composition (A) composed of 95% by weight and 50 to 5% by weight of an inorganic filler as an intermediate layer and having a moisture-resistant thermoplastic resin (B) layer in the inner and outer layers of the intermediate layer, At least in the body wall material, EVOH contains a large number of regions in which a substantially two-dimensional thin layer of an inorganic filler is stacked in parallel with the container wall surface, and the weight average flake diameter of the inorganic filler in the region. Is a particle diameter of 50 μm or less, a weight average aspect ratio is 3 or more, and a moisture permeability of the resin composition (A) layer satisfies the following formula (I). Here, W is the moisture permeability (g · 30 μ / m ² · day) at a temperature of 40 ° C. and a relative humidity of 90%, E is the content (mol%) of the ethylene component of EVOH in the resin composition (A), A _i (I = 0 to 5) is a constant given below. E ⁱ means E to the i-th power. A ₀ = 1.105 × 10 ³ A ₁ = −8.150 × 10 A ₂ = 2.420 A ₃ = −3.535 × 10 ⁻² A ₄ = 2.530 × 10 ⁻⁴ A ₅ = −7 0.091 × 10 ^-7

In another embodiment of the present invention, the EVOH comprises two or more EVOHs having different ethylene contents, an average ethylene content of 20 to 60 mol%, and an average degree of saponification of 95.
This multilayer container is an EVOH composition (C) that is at least 2 mol%, has two or more endothermic peaks in DSC measurement, and further satisfies the following formulas (II) and (III). 5 ≦ T2−T1 (II) where 130 ≦ T1 <T2 ≦ 205 0.01 ≦ W1 / (W1 + W2) ≦ 0.6 (III) Here, T1 and T2 are DSC measurements of the EVOH composition (heating rate) (10 ° C./min), the maximum temperature of the independent melting endothermic peak (° C.) (T2) and the minimum temperature of the independent melting endothermic peak (T1), and W1, W2
Is the weight (W1) of the EVOH with the highest ethylene content,
And the weight of the EVOH with the lowest ethylene content (W2).

Still another embodiment of the present invention relates to an EVOH composition (D) obtained by saponifying a composition containing two or more ethylene-vinyl ester copolymers having different ethylene contents as the EVOH. This is the multilayer container to be used.

Hereinafter, the present invention will be described specifically. The EVOH used in the present invention is a saponified ethylene-vinyl ester copolymer, and as described above, it is important that the ethylene content is 20 to 60 mol%, and preferably 25 to 55 mol%. . If the ethylene content is less than 20 mol%, water resistance and moisture resistance are reduced, gas barrier properties under high humidity are impaired, stress cracking resistance is reduced, and it is difficult to maintain good melt processing characteristics. Become. On the other hand, if it is more than 60 mol%, the water resistance and the moisture resistance are improved, but the originally excellent gas barrier properties are deteriorated. In any case, it becomes unsuitable as a material for packaging or the like. The degree of saponification of the vinyl ester component is 95 mol%
It is necessary that the content is not less than 98 mol%. If the degree of saponification is less than 95 mol%, the thermal stability becomes poor, gels are easily formed during melt processing, and the gas barrier property and oil resistance are reduced, so that the original characteristics of EVOH cannot be maintained. It becomes difficult to enjoy the effect of.
Here, as the vinyl ester, vinyl acetate is mentioned as a typical example, but other vinyl esters, for example, lower or higher fatty acid vinyl esters (vinyl propionate, vinyl pivalate, etc.) can also be used. The vinyl ester may be used alone or in combination of two or more.

In the present invention, the EVOH has an ethylene content of 20 to 60 mol%, a saponification degree of 95 mol% or more, and a vinylsilane content of 0.0001 to 0.5 mol%.
Can be used more satisfactorily for the purposes of the present invention. As the olefinically unsaturated monomer containing silicon, a conventionally known monomer such as disclosed in JP-A-61-290046 can be used. For example, vinyl trimethoxy silane, vinyl triethoxy silane, vinyl methyl dimethoxy silane, vinyl triacetoxy silane, vinyl tripropionyloxy silane and the like can be mentioned. The silicon content is selected according to each purpose, but is preferably in the range of 0.0001 to 0.5 mol%, particularly preferably 0.001 to 0.1 mol%.

The EVOH melt index (A
According to STM D1238 65T, temperature 190 ° C,
(Value measured under the condition of a load of 2160 g; hereinafter referred to as MI)
Is not particularly limited, but is 0.1 to 50 g / 10 min. Further, the EVOH referred to in the present invention may be modified with a small amount of a copolymer monomer as long as the object of the present invention is not hindered.
-Butene, 1-hexene, 4-methyl-1-pentene,
Acrylic esters, methacrylic esters, maleic acid, phthalic acid, itaconic acid, alkyl vinyl ether,
Examples thereof include N-vinylpyrrolidone, N-n-butoxymethylacrylamide, N- (2-dimethylaminoethyl) methacrylamide or a quaternary product thereof, N-vinylimidazole or a quaternary product thereof.

Next, the inorganic filler used in the present invention will be described. It is important that the inorganic filler has a weight average flake diameter of not more than 50 μm and a weight average aspect ratio of 3 or more, and has a whiteness of 80 as measured by a reflectance measurement using a Kett photovoltaic whiteness meter. The above is desirable. If the weight average flake diameter is larger than 50 μm, the blending property with EVOH and the moldability after blending will be poor, and if the aspect ratio is smaller than 3, the modifying effect will be insufficient. The whiteness is desirably 80 or more in terms of the hue of the molded product. The weight average flake diameter and aspect ratio of the above-mentioned inorganic filler are E
It has been confirmed by a scanning electron microscope that there is almost no difference between the value of the raw inorganic filler before mixing with the VOH and the value of the inorganic filler present in the container.

Therefore, in the present invention, the weight average flake diameter and the weight average aspect ratio of the inorganic filler are as follows.
It means the value of the inorganic filler before kneading in the EVOH or the value of the inorganic filler present in the container. The weight average flake diameter of the inorganic filler is preferably 30 μ or less,
More preferably, it is 20 μ or less. The lower limit is not particularly limited, but is preferably 1 μ, more preferably 3 μm.
μ. The weight average aspect ratio is preferably 5
Above, more preferably 10 or more. The upper limit is not particularly limited.

In the present invention, the weight average flake diameter is defined as the powder (here, an inorganic filler) is classified by using a micro sieve or a sieve having various openings, and the result is expressed by Ro.
plotted in sin-Rammlar diagram, a value corresponding to the mesh L ₅₀ of micro-sieve or sieve 50 wt% of the total weight of the powder was subjected to the measurement is passed. That is, the weight average flake diameter L of the powder is (IV) or (V)
Defined by an expression. L = L ₅₀ (in the case of micro sieve) (IV) L = 2 ^1/2 · L ₅₀ (in the case of sieve) (V) Here, the portion of the powder having a large particle size is classified by the sieve. Yes, the parts having a small particle size are classified by a microsieve.

On the other hand, the weight average aspect ratio α of the powder in the present invention is obtained by using the formula (VI) from the weight average flake diameter L and the weight average flake thickness d of the powder measured by the following method. This is a calculated value. α = L / d (VI)

The weight average flake thickness d of the powder in the formula (VI) is C.I. E. FIG. Capes et al. Reported a single-particle water surface membrane method {C. E. FIG. Capes and R.A. C. Col
eman. Ind. Eng. Chem. Fund
am. , Vol. 12, No. 1, p. 124-126
(1973) This is a value calculated from the equation (VII) using the occupied area S of the flake on the water surface measured by｝. d = W / ρ (1-ε) · S (VII)

Here, W is the weight of the powder used for the measurement, ρ is the specific gravity of the powder, and (1-ε) is the occupancy when the powder is in the closest packed state on the water surface. For the body, 0.9 was generally used in the calculations.

In the present invention, examples of the inorganic filler include talc, clay, sericite, glass flake, and mica. Of these, talc and clay are preferred in view of impact resistance and thermoformability.

The compounding ratio in the composition (A) is in the range of 50 to 95% by weight of the EVOH, 50 to 5% by weight of the inorganic filler, particularly 50 to 15% by weight, particularly 40 to 20% by weight. Selected from. When the amount of the inorganic filler is more than 50% by weight, the fluidity at the time of melting, the moldability and strength of the blend are reduced, and the film forming property is also reduced. And the effect of maintaining the appearance of a multilayer container having the intermediate layer of the composition after sterilization treatment under conditions where heat and moisture act simultaneously is not sufficient.

The composition (A) comprising 50 to 95% by weight of the EVOH and 50 to 5% by weight of the inorganic filler in the present invention is used as an intermediate layer of a multilayer container. In particular, it is important for the present invention that the EVOH has a dispersed structure in which the inorganic filler does not agglomerate in the EVOH and contains a large number of regions in which substantially two-dimensional thin layers are stacked in parallel with the container wall surface. This is one of the requirements, and this feature can be determined from observation with a scanning electron microscope. The region where the inorganic filler is laminated in the EVOH in parallel to the container wall surface must exist at the body, and preferably exists not only at the body but also at the bottom. In addition, that a large number of the regions are included means that the regions exist not only at one position but at least a plurality of positions in the wall material or the thickness direction in the wall material.

Next, a method for obtaining the resin composition (A) will be described. In order for the inorganic filler to be uniformly dispersed in the EVOH without agglomeration, and to become a substantially two-dimensional thin layer, which is laminated in parallel with the container wall surface,
The kneading operation of the resin composition (A) is important. A method of melt-kneading EVOH and an inorganic filler (particularly talc) at a temperature equal to or higher than the melting point of EVOH (melt kneading method) is mentioned first. For example, mixing in a Hensiel mixer, super mixer, or EVOH
There is a method in which an inorganic filler is mixed with a melt to form a master, which is mixed with a powdery substance, pellets, or a melt of EVOH, and then the mixture is kneaded at a temperature equal to or higher than the melting point of EVOH. The EVOH and the inorganic filler can be directly introduced into the kneader and kneaded without previously mixing the EVOH and the inorganic filler. Continuous kneaders such as a continuous intensive mixer and a kneading type twin-screw extruder (same direction or different direction) are used as kneaders for obtaining a composition having a high degree of dispersion without aggregation of inorganic fillers. However, a batch-type kneader such as a Banbury mixer, an intensive mixer, or a pressure kneader can also be used.

Among them, the most preferred one for the purpose of the present invention is a continuous intensive mixer. Commercially available types include FCM manufactured by Farrel, CIM manufactured by Japan Steel Works, Ltd., KCM, NCM, LCM, and ACM manufactured by Kobe Steel Works, Ltd. In fact, there is a single screw extruder under these kneaders,
An apparatus that simultaneously performs extrusion pelletization is desirable.

Further, a twin-screw kneading extruder having a kneading disk or a kneading rotor, for example, TEX, Werner & Pfleidere of Japan Steel Works, Ltd.
ZSK of r company, TEM of Toshiba Machine Co., Ltd., and PCM of Ikegai Steel Co., Ltd. are also used for the purpose of kneading in the present invention.

In using these continuous kneaders, the shapes of the rotor and the disk play an important role.
In particular, the gap (clearance) between the mixing chamber and the rotor chip or the disk chip is important, and 1 to 5 mm is appropriate as the chip clearance. Also,
In order to obtain the composition having good dispersibility of the present invention, the specific energy of the kneader is preferably 0.05 kWh / Kg or more, more preferably 0.1 to 0.8 kWh / Kg.

The specific energy is obtained by dividing the energy used for kneading (power consumption; KW) by the kneading processing amount per hour, and the unit is KWh / Kg.
It is. It is necessary for the composition of the present invention to be kneaded with a specific energy higher than the value used in normal kneading, and to obtain a specific energy of 0.05 KWh / Kg or more, simply use a kneader. It is not sufficient to simply increase the number of revolutions, and it is preferable to cool the kneaded composition by a jacket or the like to lower the temperature and increase the viscosity. The kneading temperature is the melting point of EVOH from the resin temperature discharged at the outlet of the kneading section.
Melting point + 80 ° C., more preferably melting point to melting point + 60 ° C.
Range. The rotation speed of the rotor of the kneading machine is 50.
~ 1200 rpm, preferably 100 ~ 1200 rpm
It is. The inner diameter of the kneader chamber is 20 mm or more, preferably 30 mm or more.

When the inorganic filler (such as talc) is added to the resin forming the layer (B), the melt-kneading method can be carried out.

Another method for obtaining the composition (A) is as follows.
EVOH and inorganic filler are mixed with methyl alcohol / water, n-
This is a method (solvent method) of compounding using an EVOH solvent such as propyl alcohol / water. The method of adding the inorganic filler to the solution in which the EVOH is dissolved, or vice versa, is as follows.
Either a method of adding and dissolving VOH or a method of simultaneously adding VOH may be used. After blending, Japanese patent 72
No. 5,520 (JP-A-47-38634), a method of separating EVOH mixed with an inorganic filler by precipitation into a strand, which is disclosed in JP-A-47-38634, is preferably used. After the precipitation and isolation, if necessary, treatment such as water washing and acid treatment is performed by a known method, and then drying is performed. In addition, according to the solvent method,
An inorganic filler (such as talc) may be added during the saponification process before obtaining OH.

When obtaining the resin composition (A),
A plasticizer, a lubricant, an antioxidant, a coloring agent, an ultraviolet ray inhibitor, or another polymer may be added as long as the effects of the present invention are not impaired.

Next, what is important in the present invention is that the moisture permeability of the composition (A) layer in the present invention is the above formula (I), preferably the following formula (I '), more preferably The multi-layer container obtained by using the EVOH composition obtained by the above method has a desired improvement effect, but may not always be sufficient. As a result of intensive studies, the inventors have found that, as the EOVH, by using the composition (A) layer having such a small moisture permeability,
EO even under high temperature and high humidity such as retort sterilization
It has been found that VH has a small decrease in gas barrier properties. Here, W is the moisture permeability (g · 30 μ / m ² · day) at a temperature of 40 ° C. and a relative humidity of 90%, and E is the content of the ethylene component of the ethylene-vinyl alcohol copolymer in the resin composition (A) ( Mol%), Bi (i = 0 to 5)
And Ci (i = 0 to 5) are constants given below. The moisture permeability was measured according to JIS Z 0208 by peeling the composition (A) layer from the multilayer container. Also E
ⁱ indicates that E is the i-th power. B ₀ = 9.100 × 10 ² B ₁ = −6.712 × 10 B ₂ = 1.993 B ₃ = −2.911 × 10 ⁻² B ₄ = 2.083 × 10 ⁻⁴ B ₅ = −5 _{^{.840 × 10 -7 C 0 = 6.000}} × 10 2 C 1 = -4.193 × 10 C 2 = 1.188 C 3 = -1.667 × 10 -2 C 4 = 1.156 × 10 - ⁴ C ₅ = -3.163 × 10 ^-7

In the present invention, as a method for imparting such moisture permeability, for example, phosphate groups (PO
₄ ^-3) a method of present 5~500ppm the like. Here, as the compound having a phosphate group, phosphoric acid,
Sodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate and the like can be mentioned. The content of the phosphate group is preferably 10 ppm or more, more preferably 20 ppm or more, and preferably 400 ppm or less, more preferably 300 ppm or less.

Another requirement of the present invention is that the composition (A) is used as an intermediate layer, and a layer of a moisture-resistant thermoplastic resin (B) is provided on both sides of the intermediate layer. If the layer (B) is provided only on one side of the layer (A), the package of the present invention, which is excellent in storability, cannot be obtained.

As a resin forming the layer of the moisture-resistant thermoplastic resin (B), a hydrophobic resin, in particular, a polyolefin-based resin is exemplified. Examples of the polyolefin resin include high-, medium-, or low-density polyethylene, vinyl acetate, acrylate, and α- such as butene, hexene, and 4-methyl-1-pentene.
Polyethylene copolymerized with olefins, ionomer resin, polypropylene, polypropylene graft copolymerized with ethylene, or polypropylene copolymerized with α-olefins such as ethylene, hexene, 4-methyl-1-pentene, poly-1-butene , Poly-4-methyl-1-pentene, or a modified polyolefin obtained by reacting the above-mentioned polyolefin with maleic anhydride or the like. Among them, polypropylenes (PP) are most suitable for the purpose of the present invention.

The resin forming the layer (B) is a polyester resin represented by poly (ethylene terephthalate), poly (ethylene naphthalate), poly (butylene terephthalate), poly (ethylene terephthalate / isophthalate), and the like. Resin, polystyrene resin such as polystyrene, styrene-butadiene copolymer, styrene-isoprene copolymer, and polycarbonate resin are exemplified.

The resin forming the layer (B) may be the same as or different from the inner and outer layers. Further, the resin forming the layer (B) may contain the above-mentioned inorganic filler (such as talc) as long as the moldability is not impaired.

Another aspect of the present invention is as follows.
In the case where the multilayer laminate having the (A) layer as the intermediate layer and the (B) layer as the inner and outer layers is subjected to secondary stretching into a container or the like by heating and stretching, particularly, the melting point of the EVOH in the (A) layer is not more than the melting point (T2).
In the case where the stretch molding is carried out in the following), it is to use an EVOH which has a suitable thermoformability without cracks, uneven stretching and the like, has no change in appearance after retort, and is excellent in retort suitability. The most important requirement in this embodiment is that the EVOH has two or more types of E with different ethylene contents.
It consists of VOH, has an average ethylene content of 20 to 60 mol%, an average degree of saponification of 95 mol% or more, and has two or more endothermic peaks in a DSC measurement (heating rate 10 ° C./min, substantially anhydrous state). And further (II),
The use of an EVOH composition (C) satisfying the formula (III).

It is important that the average ethylene content be from 20 to 60 mol%, preferably from 25 to 55 mol%. If the average ethylene content is less than 20 mol%, the water resistance and moisture resistance are reduced, and the gas barrier property under high humidity is impaired, and the stress cracking resistance is reduced.
Also, it is difficult to maintain good melt processing characteristics. On the other hand, 6
If it is more than 0 mol%, the water resistance and moisture resistance are improved, but the originally excellent gas barrier properties are deteriorated. In any case, it becomes unsuitable as a material for packaging or the like. The average degree of saponification needs to be 95 mol% or more, and preferably 98 mol%. If the degree of saponification is less than 95 mol%, the thermal stability becomes poor, a disadvantage occurs in that gel is easily generated at the time of melt processing, and the gas barrier properties and oil resistance also decrease,
The original characteristics of the EVOH cannot be maintained, and it becomes difficult to enjoy the effects of the present invention.

In order to exhibit more excellent effects in the above formula (II), it is necessary to use an EVOH composition (C) satisfying the following formulas (II ') and (III'). 10 ≦ T2−T1 (II ′) 135 ≦ T1 <T2 ≦ 190 0.05 ≦ W1 / (W1 + W2) ≦ 0.55 (III ′)

EVO satisfying the above formulas (II) and (III)
In order to obtain the H composition (C), for example, the following method is employed. That is, there is a method in which EVOH having T1 (EVOH having the maximum ethylene content) and EVOH having T2 (EVOH having the minimum ethylene content) are separately prepared and blended in a molten state or a solution state.
In addition, in order to obtain the resin composition (A) according to the method already described, the inorganic filler is EVOH having T1 and TOH.
The compound may be previously added to each of the EVOHs having 2 or one of them, or may be added after obtaining the EVOH composition (C). However, the multilayer container obtained by using the EVOH composition obtained by this method has a desired improvement effect but may not always be sufficient.

Therefore, the present inventors have conducted intensive studies, and as a result,
The above formulas (II) and (III) obtained by saponifying a composition containing two or more types of ethylene-vinyl ester copolymers having different ethylene contents as EVOH in the resin composition (A). It has been found that a multilayer container obtained by using a satisfactory EVOH composition (D) has further excellent gas barrier properties, thermoformability, and appearance of the container.

As a method for obtaining a composition containing two or more ethylene-vinyl ester copolymers having different ethylene contents, two or more ethylene-vinyl ester copolymers having different ethylene contents are prepared by solution. Alternatively, a method obtained by blending in a molten state, or using two polymerization tanks arranged in series or in parallel, different polymerization conditions in each polymerization tank, such as polymerization temperature, polymerization pressure, polymerization catalyst, polymerization time, etc. By setting different conditions, for example, in order to obtain an ethylene-vinyl ester copolymer having a higher ethylene content, the polymerization pressure is increased, and the ethylene-vinyl ester copolymer having a lower ethylene content is increased. When obtaining a polymer, by setting the polymerization pressure lower, the ethylene-vinyl ester-based And a method of obtaining a polymer composition. There is also a method of blending an ethylene-vinyl ester copolymer and an ethylene-vinyl alcohol copolymer having a different ethylene content in a solution or a molten state. Among them, the former method by changing the polymerization conditions is most preferable. Next, as a method for saponifying the ethylene-vinyl ester-based copolymer composition, the ethylene-vinyl ester-based copolymer composition is dissolved or dispersed in water, alcohol, or another organic solvent, and the acid or alkali is dissolved. There is a method of saponifying with a system catalyst. For example,
The solvent composition is carried out under conditions such as blowing in a mixed solvent of water-containing methanol and methyl acetate, and injecting a mixed vapor of methanol and methyl acetate to remove reaction by-products.

The EVOH composition (D) may be modified with a small amount of the above-mentioned copolymerizable monomer as long as the object of the present invention is not impaired. Coloring agents, ultraviolet absorbers, and other polymers may be added as long as the effects of the present invention are not impaired.

If the interlayer adhesive strength of the multilayer sheet having the resin composition (A) and the moisture-resistant thermoplastic resin (B) in the present invention is not sufficient, it is preferable to provide an adhesive resin layer. The adhesive resin is not particularly limited as long as it does not cause delamination at a practical stage, and is not particularly limited. An unsaturated carboxylic acid or an anhydride thereof may be an olefin polymer (for example, polyethylene, polypropylene, polyolefin such as polybutene, Modified olefin polymers containing a carboxyl group, which are obtained by chemically (eg, addition reaction, graft reaction) bonding to an olefin-based copolymer). Specifically, one selected from maleic anhydride graft-modified polyethylene, maleic anhydride graft-modified polypropylene, maleic anhydride graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene-vinyl acetate copolymer or Preferred are mixtures of the two. In addition, EVOH can be mixed with these adhesive resins within a range that does not impair the effects of the present invention.

In the present invention, the multilayer laminate comprising the layers (A) and (B) and the container using the multilayer laminate can be produced by a conventionally known or ordinary method. For example, in the co-extrusion method, a method of extruding into a predetermined shape through a multilayer dies such as a T-die and a circular die after melt-kneading with an extruder corresponding to each resin layer is employed. A method is employed in which after melt-kneading with an injection machine corresponding to each resin layer, the mixture is injected into a mold to obtain a multilayer container or a preform for the container. In addition, a dry lamination method, a sand lamination method, and an extrusion lamination method can also be adopted.

The laminate produced by these methods takes the form of a sheet, a film, a parison, a preform or the like, and the laminate is reheated at a predetermined temperature by vacuum pressure forming, biaxial stretching blow molding or the like. And a method of subjecting the multilayer laminate (sheet, film) to a biaxial stretching machine and performing a heating and stretching operation, and a method of stretching and blowing a parison or preform obtained by a co-injection method. It is formed in a container having a predetermined shape. Among the methods for producing the multilayer laminate, the coextrusion method can obtain the best results. In the layer of the moisture-resistant thermoplastic resin (B) in the co-extrusion method, scrap generated during production of the multilayer container of the present invention can be used as a raw material. Further, the scrap can be used as a layer independent of the (A) layer and the (B) layer.

Further, with respect to the multilayer container of the present invention, the average thickness of all the layers of the body wall is 50 to 2500 μm, particularly 250 μm.
The thickness ratio of the layer (A) to the total layer thickness is not particularly limited, but is preferably 2 to 30%.
Particularly, 5 to 20% is preferable.

In the present invention, when a container such as a cup or a bottle, a sheet, or a film is obtained by heating and stretching, the heating means that the multilayer laminate is left at a temperature required for heating and stretching for a predetermined time. Means an operation that makes the heat substantially uniform, and in view of the operability, a method of heating and uniformizing with various heaters is preferable.

The heating may be carried out simultaneously with the stretching or before the stretching. In addition, the heating is performed by chucking, plug,
It is performed by vacuum force, pneumatic force, and the like. Stretching refers to either uniaxial stretching or biaxial stretching.

The multilayer container of the present invention obtained as described above includes:
After filling the contents, especially food, the inside is degassed by known means if necessary, or nitrogen gas, after replacing the inside with an inert gas such as carbon dioxide gas, sealing by means such as heat sealing, Subsequently, it is sterilized by hot water or steam (especially high-temperature, high-pressure steam sterilization) such as a so-called boil treatment at 100 ° C. or lower or a retort treatment carried out at a temperature condition exceeding 100 ° C., especially at 105 to 135 ° C. Thus, the package of the present invention, in particular, a food package is obtained.
Here, as the boil sterilization treatment or the retort sterilization treatment, ordinary hot water or steam heat treatment conditions can be adopted. For the retort sterilization treatment, various methods such as a recovery type, a replacement type, a shower type, a spray type and the like are adopted.

When the multilayer container of the present invention is a cup or tray type container, a particularly excellent food package is obtained.

The contents to be filled are mainly foods. Here, as food, you can eat it as it is,
Cooked or semi-cooked foods that are warmed prior to eating are suitable. Next, examples of sterilized foods will be described. Cooked curry, cooked bean sprouts, beef stew, borscht, meat sauce, sour pork, sukiyaki, chinese bean, happo, meat, potato, oden, asparagus boiled, sweet corn, mushroom, tuna cream boiled, consommé,
Various soups such as potage, miso soup, pork juice, kenchin soup, rice, pot rice, fried rice, pilaf, porridge, spaghetti,
Additive foods such as buckwheat, udon, ramen, noodles, kamame-no-miso, chinese buckwheat noodles, boiled azuki, zenzai, anmitsu, meat dumpling, hamburger, beef steak, roast pork, pork steak, corned beef, ham, sausage, grilled fish , Yakiniku, yakitori, roast chicken, pork ketchup, fish meat, bacon, kamaboko, pudding, jelly, yokan, various pet foods, and the like. Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto. Parts mean parts by weight.

[0059]

【Example】

Example 1 Sodium dihydrogen phosphate containing ethylene content 31 mol%, degree of saponification of vinyl acetate component 99.5 mol%, M
80 parts of EVOH powder having an I of 1.6 g / 10 min, a weight average flake diameter of 10 μm, and a weight average aspect ratio of 1
5. After premixing 20 parts of talc powder having a whiteness of 95 in a Hensiel mixer, high-speed mixing was performed to obtain a mixture.
Continuously, a mixing chamber having an inner diameter of 30 mm, kneading using a two-stage twin-screw different-direction continuous extruder with two mixing rotors and a deaeration mechanism between the two rotors and a single-screw extruder connected to this. Extrusion pelletization was performed to obtain pellets of the composition. The mixing rotor employed at this time had a tip clearance of 3 mm from the mixing chamber, a kneading temperature (outlet temperature) of 205 to 230 ° C.
The rotor rotation speed was in the range of 300 to 450 rpm and the specific energy was in the range of 0.1 to 0.3 KWh / Kg.

With the EVOH itself in a substantially anhydrous state, the melting point Tm was measured (heating rate: 10 ° C./min) using a Mettler DSC30. Table 1 shows the results.

Then, a laminated sheet of three types and five layers having the blended pellets as an intermediate layer was subjected to an inner / outer layer extruder having a branched melt channel, an intermediate layer extruder, and a branched melt channel of an adhesive layer extruder. Obtained using a combined extruder and a T-die. The resin used in the molding was an intermediate layer of the above blend pellets, an inner and outer layer of polypropylene (Mitsubishi Yuka, Noblen PY220), and an adhesive layer of maleic anhydride modified polypropylene (Mitsui Petrochemical,
Admer QF500). The molding temperature is 180-230 ° C. for the intermediate layer extruder, and 200-240 for the inner and outer layer extruders.
℃, extruder for adhesive layer 200-240 ℃, T die 240 ℃
It is. The laminated sheet has a thickness of 650/75/135/75 / as an outer layer / adhesive layer / intermediate layer / adhesive layer / inner layer.
650μ. This multilayer sheet was thermoformed at 190 ° C. using a vacuum pressure air molding machine manufactured by Asano Research Laboratories Co., Ltd., and was a cup having a circular shape with a bottom surface having a radius of 33 mm and an upper opening having a radius of 37 mm and a height of 37 mm. A container was obtained. The cup had good appearance without any uneven stretching such as cracks and uneven thickness. The thickness configuration of this container is 270/30/55 from the outer layer.
/ 30 / 270μ (harmonic average thickness).

The obtained cup was filled with corned beef as a content and replaced with nitrogen gas, and then heat-sealed as a lid with an aluminum foil / polypropylene laminate film as a lid to obtain a sealed container to obtain a test sample (1). A 110 cc glass bottle was filled with corned beef, purged with nitrogen gas, and sealed with an aluminum cap to prepare a control sample (0). The above sample was subjected to a retort apparatus (Hisaka Manufacturing Co., Ltd., high temperature and high pressure cooking sterilization tester RCS)
-40 RTGN) and a retort treatment at 120 ° C. for 30 minutes was performed. After retort treatment, Sample (1) did not show any particular defect in appearance and morphology. This sample (1) was placed in a control sample (0) at 20 ° C. and 65% RH.
Was stored in a refrigerator (5 ° C.). Three months later, both were opened,
When age and gender were evaluated by 10 panelists randomly selected, 10 out of 10 panelists showed no change in taste, color and odor, and had good storage stability.

The EVOH layer obtained by eluting the polypropylene layer and the adhesive layer of the cup with xylene was determined according to JIS.
The moisture permeability was measured at 40 ° C. and 90% RH according to Z0208. The EVOH layer was heated at 95 ° C. for 3 hours with stirring in a 0.1 N aqueous nitric acid solution, and the phosphate group (PO ₄ ^-3 ) in the filtrate was measured by ion chromatography, and the EVOH of the phosphate group was measured. Content is 45 pp
m. The results are shown in Table 1.

The shape (weight-average flake diameter, weight-average aspect ratio) of talc obtained by firing the EVOH layer of the cup in an electric furnace was observed with a scanning electron microscope.
Little difference was observed from the one before mixing. In addition, the body of the cup was cut out at several places and the intermediate layer of the cross section was observed with a scanning electron microscope.Talc was not agglomerated, and a thin layer of talc was laminated almost parallel to the container wall. In addition, a large number of laminated areas were observed, and the dispersibility of talc (which is presumed to be affecting the reduction of oxygen gas permeability) was also good. The above results are shown in Tables 1 and 2.

Examples 2-3 A test was conducted in the same manner as in Example 1 except that the blend ratio of EVOH and talc was changed at the ratios shown in Tables 1 and 2. The thermoformability, preservability, and talc dispersibility were good, and no particular change was observed in the container appearance after the retort treatment. The results are shown in Tables 1 and 2.

Example 4 Ethylene content: 31 mol%, saponification degree of vinyl acetate component: 99.5 mol%, vinyltrimethoxysilane: 0.027
The test was carried out in the same manner as in Example 1 except that EVOH having a mole% of 1.6 g / 10 min was used. The thermoformability, preservability, and talc dispersibility were good, and no particular change was observed in the container appearance after the retort treatment.
The results are shown in Tables 1 and 2.

Example 5 A test was carried out in the same manner as in Example 1 except that the weight average flake diameter, the weight average aspect ratio and the sterilization conditions of talc were changed as shown in Tables 1 and 2. The thermoformability, preservability, and talc dispersibility were good, and no particular change was observed in the container appearance after the retort treatment. Table 1 shows the results
~ 2.

Comparative Example 1 In Example 1, EVOH alone was used without blending talc, with an ethylene content of 31 mol%, a saponification degree of a vinyl acetate component of 99.5 mol%, and a MI of 1.6 g / 10 min. A test was performed in the same manner as in Example 1 except for the above. The shelf life was poor. The results are shown in Tables 1 and 2.

Comparative Example 2 A test was conducted in the same manner as in Example 1 except that EVOH was used, the ethylene content was 31 mol%, the degree of saponification of the vinyl acetate component was 90.0 mol%, and the MI was 8.5 g / 10 min. Carried out. The shelf life was poor. The results are shown in Tables 1 and 2.

Comparative Example 3 A test was conducted in the same manner as in Example 1 except that EVOH was used, an ethylene content was 65 mol%, a degree of saponification of a vinyl acetate component was 99.3 mol%, and an MI was 25 g / 10 min. . The shelf life was poor. The results are shown in Tables 1 and 2.

Comparative Example 4 Ethylene content: 17 mol%, degree of saponification of vinyl acetate component: 99.5 mol%, MI measured at 210 ° C .: 7.5 g /
The test was performed in the same manner as in Example 1 except that the thermoforming temperature of the multilayer sheet was set to 210 ° C. instead of 190 ° C. using EVOH for 10 minutes. The storage stability, thermoformability and talc dispersibility were also poor. The results are shown in Tables 1 and 2.

Comparative Example 5 A test was performed in the same manner as in Example 1 except that the blend ratio of EVOH and talc was changed at the ratio shown in Table 1.
The storage stability, thermoformability, and talc dispersibility (some talc aggregation was observed) were also poor. The results are shown in Tables 1 and 2.

Comparative Example 6 A test was conducted in the same manner as in Example 1 except that the blend ratio of EVOH and talc was changed at the ratio shown in Table 1. However, the fluidity at the time of melting was poor, and kneading was difficult. And E
A blend pellet of VOH and talc could not be formed.
The results are shown in Tables 1 and 2.

Comparative Example 7 A test was carried out in the same manner as in Example 1 except that EVOH containing 2 ppm of sodium dihydrogen phosphate in terms of a phosphate group was used as the EVOH. The moisture permeability was large and the storage stability was poor. The results are shown in Tables 1 and 2.

Example 6 27.9 parts by weight of ethylene-vinyl acetate copolymer having an ethylene content of 31 mol% (hereinafter referred to as EVAc) (weight after saponification (W2) = 16 parts by weight) and ethylene content of 48 mol%
6.45 parts by weight of EVAc ｛weight after saponification (W1) =
4 parts by weight were dissolved in a solvent obtained by mixing 76 parts by weight of methanol and 4 parts by weight of methyl acetate.
While the H-methanol solution (the molar ratio to the vinyl acetate component was 0.2) was added dropwise, by-products were expelled with methanol-methyl acetate mixed vapor. The obtained EVOH composition is immersed in an aqueous solution in which sodium dihydrogen phosphate is dissolved, and contains 45 ppm of sodium dihydrogen phosphate in terms of phosphate radical. The average ethylene content is 34 mol%, and the average degree of saponification is 9%.
9.5 mol%, MI was 2.9 g / 10 min. Using the EVOH composition, a test was performed in the same manner as in Example 1 except that the thermoforming temperature of the multilayer sheet was set to 150 ° C. The thermoformability, preservability, and talc dispersibility were good, and no particular change was observed in the container appearance after the retort treatment. The results are shown in Tables 3 and 4.

Examples 7 and 8 and Comparative Examples 8 and 9 Tests were carried out in the same manner as in Example 6 except as shown in Tables 3 and 4. The results are shown in Tables 3 and 4.

[0077]

[Table 1]

[0078]

[Table 2]

[0079]

[Table 3]

[0080]

[Table 4]

[0081]

As is clear from the above examples, the multi-layer container of the present invention is filled with food, sealed, and then sterilized under conditions where heat and moisture act simultaneously, such as retort treatment. The body has a low permeation of oxygen, which deteriorates the food that is the content, and has no deterioration of the content, has good storage performance and appearance of the container, and also has excellent thermoformability in preparing the container. I have.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B65D 81/24 B65D 81/24 M C08F 210/02 MJG C08F 210/02 MJG // C08K 3/20 KEB C08K 3/20 KEB C08L 23/26 LDM C08L 23/26 LDM 29/04 29/04 (72) Inventor Hideaki Oda 1621 Sazu, Kurashiki City, Okayama Pref. Kuraray Co., Ltd. (72) Inventor Hiroto Hiroshi Okayama 1621 Sazu, Kurashiki-shi, Japan Examiner, Kuraray Co., Ltd. Ryoko Masuda (56) References JP-A-1-43554 (JP, A) JP-A-3-281340 (JP, A)

Claims (3)

(57) [Claims] 1. A resin composition (A) comprising 50 to 95% by weight of an ethylene-vinyl alcohol copolymer having an ethylene content of 20 to 60% by mole and a saponification degree of 95% by mole or more, and 50 to 5% by weight of an inorganic filler. A multilayer container having a moisture-resistant thermoplastic resin (B) layer in the inner and outer layers of the intermediate layer, wherein at least in the body wall material of the container, the copolymer substantially contains inorganic filler in the copolymer. Many regions in which two-dimensional thin layers are stacked in parallel to the container wall are included, and the weight average flake diameter of the inorganic filler in the region is 50%.
A multilayer container having a particle size of μ or less, a weight average aspect ratio of 3 or more, and a moisture permeability of the resin composition (A) layer satisfying the following formula (I). Here, W is the moisture permeability (g · 30 μ / m ² · day) at a temperature of 40 ° C. and a relative humidity of 90%, and E is the content (mol%) of the ethylene component of the copolymer in the resin composition (A). , A _i (i = 0 to 5) are constants given below. A ₀ = 1.105 × 10 ³ A ₁ = −8.150 × 10 A ₂ = 2.420 A ₃ = −3.535 × 10 ⁻² A ₄ = 2.530 × 10 ⁻⁴ A ₅ = −7 0.091 × 10 ^-7 2. An ethylene-vinyl alcohol copolymer comprising two or more ethylene-vinyl alcohol copolymers having different ethylene contents, and having an average ethylene content of 2.
0 to 60 mol%, the average degree of saponification is 95 mol% or more,
And having two or more endothermic peaks in the DSC measurement,
Further below (II) and (III) a composition satisfying (C) is a formula according to claim 1 multilayered container according. 5 ≦ T2−T1 (II) where 130 ≦ T1 ≦ T2 ≦ 205 0.01 ≦ W1 / (W1 + W2) ≦ 0.6 (III) Here, T1 and T2 are the DSC measurements of the composition (C). The maximum temperature of the independent melting endothermic peak (T2) and the minimum temperature of the independent melting endothermic peak (T1) when the temperature rise rate is 10 ° C./min), and W1, W2
Are the weight (W1) of the ethylene-vinyl alcohol copolymer having the maximum ethylene content and the weight (W1) of the ethylene-vinyl alcohol copolymer having the minimum ethylene content.
2). 3. A package obtained by filling the multilayer container according to any one of claims 1 to 2 with a content, sealing the content, and treating with hot water or steam.