JPH01191668A - Method for treating container - Google Patents

Abstract

PURPOSE:To prevent putrefaction, deterioration and denaturation by preservation for a long period, by filling contents in a container having propylene based polymer layers as an inner and outer layers and a specific saponified substance placed therebetween, hermetically sealing the container and treating the contents under specific conditions. CONSTITUTION:A container body is formed from an inner layer 1 and an outer layer 2 of a propylene based polymer and an intermediate layer 3 of saponified ethylene-vinyl acetate copolymer (having >=80% saponification degree and 15-60mol% copolymerization ratio of ethylene). Bonding resin layers 6 and 7 may be provided. The thickness of the outer layer 2 is 30-200mum and contents are filled in the container. After hermetically sealing the container, the contents are heat-treated with steam or hot water and dried by an infrared heater. A heater simultaneously having near infrared rays (with >=40% emissivity) at 2-4mum wavelength and far infrared rays (with >=40% emissivity) at 6-15mum wavelength or two kinds of heaters are used as the infrared heater. The moisture content of the saponified substance layer is reduced to <=10% in a short time.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for treating containers.

The present invention relates to a method for processing a thermoplastic resin container, which is characterized in that the food containing water contained therein is processed to have excellent long-term storage stability. [Prior art] In recent years, olefin polymers (for example,
Plastink molded containers using a saponified ethylene-vinyl acetate copolymer as a gas barrier layer are considered suitable for food storage due to their excellent gas barrier properties. Its uses are currently expanding.

However, after filling the contents (e.g., soup) into this type of molded container body and sealing it, a retort heat sterilization treatment (e.g., 30 minutes at a temperature of 125°C) is performed.
minutes), the ethylene layer in the middle layer during heat sterilization
Saponified vinyl acetate copolymer absorbs moisture and acts as a gas barrier
There were problems such as a significant decrease in the quality of the product and the contents becoming rotten, deteriorated, and discolored.

(Problems to be Solved by the Invention) From the above, the present invention does not have these drawbacks (problems), that is, it not only has excellent gas harrier properties when not retorted, but also has long-term durability after retort heat sterilization. To obtain a thermoplastic resin container whose contents do not rot, deteriorate, or denature even when stored.

[Means and effects for solving the problems] According to the present invention, these problems can be solved by changing the copolymerization ratio of ethylene to 1
A saponified layer obtained by saponifying at least 80% of an ethylene-vinyl acetate copolymer of 5 to 60 mol % is interposed, the inner and outer layers are propylene polymer layers, and the outer layer has a thickness of 30 to 200 mol %. After filling the container with the contents and sealing it, the container is treated with steam or hot water, and the infrared rays are at least 40% in the infrared region of wavelengths 2 to 4 JLI+, and the distance is 6 to 25 pm. The problem can be solved by a method for treating a container, characterized in that the water content of the saponified layer is reduced to 10% or less using an infrared heater having an emissivity of 40% or more in the infrared region. The present invention will be explained in detail below.

(8) Propylene polymer In the present invention, the propylene polymer constituting the inner layer and the outer layer is a propylene homopolymer or a lantum or α-olefin containing ethylene or other α-olefin containing at least 70% by weight of propylene. Random or flock copolymers with 1.
A good product is obtained when 0 to 50% by weight of ethylene polymer is mixed with propylene polymer. The melt flow index (JIS
Measured according to K-7210 under conditions 14, hereinafter r M
FR (1) J) is 0.005 to 80 g/lo min, preferably 1 to 60 g/lo min.
Particularly suitable is a propylene polymer having a content of 0.01 to 40 g/ro. MFR (1) or 0.005g/
If a propylene polymer is used for less than 10 minutes, the molding processability to obtain a container will be poor, and a good container will not be obtained.
When using a propylene polymer that exceeds g/10 minutes,
The impact resistance of the container is weak and the container is not suitable for practical use.

As the propylene polymer in the present invention, one to which an inorganic filler described later may be added may be used.

In this case, when forming a container and filling the container with food, from the viewpoint of food hygiene, a propylene polymer that does not contain an inorganic filler is added inside the inner layer of the propylene polymer that contains an inorganic filler. It is preferable to provide a layer of

The inorganic filler is generally one widely used in the fields of synthetic resins and rubber.

These inorganic fillers are preferably inorganic compounds that do not react with oxygen and water and do not decompose during kneading and molding.

The inorganic fillers include aluminum laminate, metals such as copper, iron, lead and nickel, oxides of these metals and metals such as magnesium, calcium, barium, zinc, zirconium, molybdenum, silicon, antimony and titanium, and hydrates thereof. It is broadly classified into compounds such as hydroxides, sulfates, carbonates, silicates, their double salts, and mixtures thereof. A representative example of the inorganic filler is disclosed in Japanese Patent Application No. 1983-
It is described in No. 124481.

Among these inorganic fillers, those in powder form have a diameter of 3
Preferably, the diameter is 0 micron or less (preferably 10 micron or less). In addition, the fibrous material has a diameter of 1 to 500 microns (preferably 1 to 300 microns) and a length of 0.
．． A thickness of 1 to 6.0 mm (preferably 0.1 to 5 mm) is desirable. Further, it is preferable that the plate-like material has a diameter of 30 microns or less (preferably 10 microns or less). Among these inorganic fillers, those in the form of flat plates (flake) and those in the form of powder are particularly suitable.

The composition ratio (content ratio) of the inorganic filler in the inorganic filler-containing propylene polymer is at most 70% by weight, preferably 5 to 65% by weight, particularly preferably 5 to 60% by weight.

If the composition ratio of the inorganic filler in the inorganic filler-containing propylene polymer exceeds 70% by weight, the impact resistance of the resulting container will be significantly reduced, resulting in a container that is not suitable for practical use.

(B) Saponified product of ethylene-vinyl acetate copolymer Furthermore, in the present invention, ethylene is the starting material for the saponified product of ethylene-vinyl acetate copolymer constituting the intermediate layer interposed between the inner layer and the outer layer. - The copolymerization ratio of ethylene in the vinyl acetate copolymer is 15 to 60 mol%, and is 15 to 60% by mole.
55 mol% is preferred. In particular, the degree of saponification is 80% or more, preferably 85% or more, particularly preferably 90% or more.

Furthermore, melt flow index (JIS K-7
Is it 210? Temperature 210°C and load 2.
Measured at 16kg, below r! IIFR (2)] is usually 0.1 to 50 g/10 minutes, and 0.1 to 20 g
/10 minutes or preferably, especially 0.5-20g/
10 minutes or suitable MFR (2) or 0.1g/1
If a saponified ethylene-vinyl acetate copolymer is used for less than 0 minutes, the moldability will be poor when producing the multilayer laminate described below. On the other hand, if a saponified ethylene-vinyl acetate copolymer exceeding 20 g/10 minutes is used, extrudability is poor when producing a multilayer laminate, and a good laminate cannot be obtained.

In producing the container of the present invention, an adhesive resin may be interposed as shown in F in order to improve the adhesion between the inner layer and the intermediate layer and between the outer layer and the intermediate layer.

(C) Adhesive resin and adhesive In addition, in the present invention, the adhesive resin used for adhering the inner layer and outer layer to the intermediate layer is a graft polymerization of an unsaturated carboxylic acid or a derivative thereof to an olefin polymer. It can be obtained by making This kraft polymerization is generally carried out in the presence of a radical initiator as described below.

The olefin polymer may be an ethylene homopolymer, ethylene and at least 12 carbon atoms (preferably 3 carbon atoms).
~8 pieces) with α-olefin (copolymerization ratio of α-olefin is usually 20% by weight or less, preferably 15% by weight or less, preferably 10% by weight or less) and ethene as the main component ( Generally 65% by weight or more, preferably 70% by weight
(weight% or more) monomers having polar groups [e.g.
Examples include copolymers with vinyl acetate, (meth)acrylic acid or alkyl esters thereof, and the propylene-based polymers described above.

Melt flow index (
Measured according to JIS K-7210, condition 4,
The MFR (hereinafter referred to as r MFR (:l) J) and the VFR (1) of propylene polymers are both generally from 0.1 to
100 g/10 minutes, preferably 0.02 to 50 g/10 minutes, particularly preferably 0.05 to 50 g/10 minutes. When a propylene polymer or an ethylene polymer having an MFR (1) or MFR (3) below the lower limit is used, it is difficult to uniformly carry out the craft reaction. On the other hand, if the amount exceeding the upper limit is used, the strength of the resulting adhesive resin will be poor, and the adhesive strength will also be poor.

Among these olefin polymers, low-density and high-density ethylene homopolymers, propylene homopolymers, copolymers of ethylene and propylene, and copolymers of ethylene or propylene with other α-olefins. or desirable.

The unsaturated carboxylic acids used in producing this kraft copolymer are broadly classified into monobasic unsaturated carboxylic acids and dibasic unsaturated carboxylic acids. - The basic unsaturated carboxylic acid usually has at most 20 carbon atoms (preferably 15 or less), and representative examples include acrylic acid and methacrylic acid. Furthermore, the number of carbon atoms in dibasic unsaturated carboxylic acids is generally at most 40.
(preferably 30 or less), typical examples of which include maleic acid, itaconic acid, nadecic acid, and fumaric acid. Furthermore, examples of derivatives include esters, acid anhydrides, amides, imides, and metal salts of these monobasic unsaturated carboxylic acids and dibasic unsaturated carboxylic acids. Among these derivatives, for amides and imides, the number of carbon atoms in the amide group and imide group is usually at most 20 (preferably 15 or less). Further, the total number of carbon atoms in the ester is generally at most 40, preferably 30 or less. Further, the metal of the metal salt generally includes alkali metals and metals of Group 2 of the periodic table, and representative examples thereof include sodium, potassium, zinc, magnesium, and calcium. Representative examples of these derivatives include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, methyl methacrylate, glycidyl acrylate, glycidyl methacrylate, and maleic acid. Monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester, fumaric acid dimethyl ester, itaconic acid monomethyl ester, itaconic acid diethyl ester, acrylamide, methacrylamide, maleic acid monoamide, maleic acid diamide, maleic acid-N-monoethylamide , maleic acid-N, N-diethylamide, maleic acid-N-monobutyramide, maleic acid-N
, N-dibutylamide, fumaric acid monoamide.

fumaric acid diamide, fumaric acid-N-monoethylamide,
Fumar M-N, N-diethylamide, fumaric acid-N-monophthylamide, fumaric acid N-N, N-cyphthylamide, maleimide, N-butylmaleimide, N-phenylmaleimide, sodium acrylate, sodium methacrylate, potassium acrylate, Potassium methacrylate can be given.

In addition, the decomposition temperature of the radical initiator used in this graft polymerization with a half-life of 1 minute is usually 100°C or higher,
A temperature of 105°C or higher is preferred, and a temperature of 120°C or higher is particularly preferred. Representative examples of suitable radical initiators include cyflumi peroxide, benzoyl peroxide, cy tertiary-butyl peroxide, 2,5-
Dimethyl-2,5-di(tertiary-phthyl peroxy)
Examples include organic peroxides such as hexane, 2,5-dimethyl-2,5-di(tertiary-butylperoxy)hexane-3, lauroyl peroxide, and tertiary-phthyl peroxybenzoate.

The ratio of the unsaturated carboxylic acid, its derivative, and the radical initiator to 100 parts by weight of the olefin polymer is generally as follows.

The total amount of unsaturated carboxylic acids and derivatives thereof is 0.1 to 5.0 parts by weight, and 0.05>3.
0 parts by weight is preferred, and 0.1 to 2.0 parts by weight is particularly preferred. If the proportion or total amount of unsaturated carboxylic acids and derivatives thereof used is less than 0.01 parts by weight, the adhesion of the kraft copolymer will be insufficient. On the other hand, 5.
If the amount exceeds 0 parts by weight, not only may decomposition or crosslinking reactions occur simultaneously during the production of the graft copolymer, but also the adhesiveness may deteriorate.

Further, the amount of the radical initiator is 0.001 to 1.0 parts by weight, preferably 0.01 to 1.0 parts by weight, particularly 0.01 to 0.5 parts by weight. If the proportion of the radical initiator used is less than 0 or 0 parts by weight, the modification effect will be insufficient and a long period of time will be required to complete the modification. on the other hand,
If it exceeds 1.0 part by weight, it is not preferable because excessive decomposition or crosslinking reaction occurs.

The graft copolymer of the present invention can be produced by any known means for producing this type of craft copolymer.

A typical production method involves preparing the olefinic polymer, unsaturated carboxylic acid or its derivative, and radicals in a solvent such as an aromatic hydrocarbon compound such as xylene or toluene, or an aliphatic hydrocarbon compound such as hexane or heptane. A method of manufacturing by heating and mixing an initiator, and a method of mixing these olefinic polymers, unsaturated carboxylic acids or derivatives thereof, and radical initiators in advance under conditions that essentially do not crosslink, and then passing the resulting mixture through a screw extruder, Can you name a production method that involves melt-mixing using a kneader commonly used in the field of synthetic resins, such as a Banbury mixer or kneader?
The latter method is preferred from the point of view of economy.

In the latter case, the temperature conditions for modification are appropriately selected in consideration of the deterioration of the olefin polymer, the decomposition of the unsaturated carboxylic acid or its derivative, the decomposition temperature of the organic peroxide, etc. ~350°C, 1
50-350'C, preferably 150-30'C
0°C is preferred.

Furthermore, in the present invention, adhesives that are generally reprinted can also be preferably used. Typical examples of such adhesives include aliphatic and aromatic urethane adhesives, which can be retorted without delamination,
Even if retorted at 125°C for 30 minutes, it is desirable that the adhesive strength be 800 g/15 aua or more.

(D) Container and method for manufacturing the same The container of the present invention will be explained in more detail with reference to one drawing below.

FIG. 1 is a sectional view of a typical container body of the present invention filled with contents 10 and sealed by a lid 11. FIG. 2 is a partially enlarged sectional view of the bottom wall portion 9 of the sectional view shown in FIG. 1. The container body has a flange portion 5 as shown in FIG. The container body has an inner layer 1 and an outer layer 2 made of a propylene polymer, and an intermediate layer 3 made of a saponified ethylene-vinyl acetate copolymer interposed between these layers. Furthermore, adhesive resin layers 6 and 7 as described below may be provided between the inner layer 1 and the intermediate layer 3 and the outer layer 2 and the intermediate layer 3, respectively, in order to improve their adhesion.

The saponified layer 3 of ethylene-vinyl acetate copolymer, which is the intermediate layer, generally has a certain thickness in order to maintain practical gas barrier properties in a normal dry state (a state balanced with normal humidity). is 5 to 200 lm, especially l
O to 180 p-rs is preferred.

The water vapor permeation amount of the propylene polymer layer 2 having a thickness of 30 to 200 pm as the outer layer is 3 to 50 times that of the propylene polymer layer 1 as the inner layer,
A ratio of 3 to 40 times is desirable, and a range of 3 to 35 times is particularly preferred. This facilitates the loss of moisture by drying the moisture absorbed by the intermediate layer during treatments such as retort heat sterilization described later, thereby promoting recovery of the oxygen barrier properties of the intermediate layer. This is to do so. However, the outer layer 2 must have a water vapor permeation rate that is 50 times or less than the water vapor permeation rate of the inner layer 1, or a thickness of 30 pLm or more. If it is thinner than that, the strength of the outer layer 2 will be weak during the delamination and distribution stages during retort heat sterilization, and the middle layer 3 will be damaged due to scratches, etc., which will not only reduce the barrier properties of the container, but also reduce the strength of the outer layer 2 during delamination and distribution stages during retort heat sterilization. If the container is placed underneath, there may be problems such as a decrease in barrier properties. On the other hand, if the thickness is less than 5 times the magnification, the length must be constantly increased and at the same time the temperature of the contents becomes high, causing changes in the contents, which is not preferable. From these facts, the thickness of the inner layer and outer layer depends on the type of propylene polymer m used, the presence or absence of an inorganic filler mixed into the propylene polymer, the type and proportion of the inorganic filler mixed, and the container. The thickness of the outer layer is usually 30 to 2.
007zm, particularly preferably 30 to 180ga+. On the other hand, the thickness of the inner layer is generally between 100 p.m and 2.0 mm, especially between 2001 Lm and 1.0 mm.
51 is desirable. Further, when the adhesive resin layer is interposed between the outer layer and the intermediate layer and between the inner layer and the intermediate layer, the thickness thereof is usually 5 to 50 gm (preferably 5 to 20 gm).
).

Further, in the container shown in FIG. 1, the flange portion 5,
The thickness of the trunk wall part 8 and the bottom wall part 9 is generally 0.3 to 0.3 to ensure self-shape retention and to prevent deformation during retort processing.
It is LD II■.

To manufacture the container of the present invention, any molding method practiced in the field of general olefin polymers (such as a sheet method, an injection molding method, a blow molding method, etc.) may be applied. As a typical example of this molding method, each thin layer (film, sheet) of the inner layer, intermediate layer, outer layer, or these layers and adhesive resin layer is formed in advance by sheet molding or film molding method in these fields. Then, a laminated sheet is manufactured by adhering each of these thin materials. In step ν), a container may be manufactured from this sheet by vacuum forming, pressure forming, or press forming. In addition, polymers (
The sheet may be manufactured by co-extrusion sheet molding (resin).

As shown in FIG. 1, after the container body thus manufactured is filled with contents 1O, the lid portion 11 is heat-sealed to the flange portion 5 for sealing. The lid 11 is a laminate that forms the body of the molded container, for example, a laminate that has a metal foil (for example, aluminum foil) on the outside of a resin that can be heat-sealed to the inner layer of the lid 11 or the inner layer l of the container body. Good too.

The sealed container thus produced can be subjected to retort heat sterilization (sterilization by steaming or ripening) under the conditions of time and temperature necessary to ensure complete commercial sterilization of the contents. (for example, for 30 minutes at a temperature of 125°C). During this treatment with 'f2 bacteria, the water content of the saponified ethylene-vinyl acetate copolymer in the intermediate layer increases and usually exceeds 20%.

After the sterilization process is completed, the sealed container that leaves the sterilization tank (not shown) is then cleaned so that the water content of the saponified layer of the ethylene-vinyl acetate copolymer is 10% or less (preferably 6% or less).
drying with an infrared heater having an emissivity of at least 40% in the near-mid infrared region of 2-4 pm and an emissivity of 40% or more in the far-infrared region of 6-15 g1. Furthermore, hot air (generally at a temperature of 20 to 130
℃, relative humidity less than 10%) may be carried out.

When using a normal far-infrared heater (far-infrared radiation type heater) with an emissivity of less than 40% in the near- and mid-infrared region (wavelength 2 to 4 JLI11), the processing time will be very long, and the content will be lost during processing. The temperature of the object or high temperature (for example, 90
(100°C or higher), which is undesirable because the contents change, the internal pressure of the container increases, and the container deforms.

On the other hand, when using an infrared heater with an emissivity of less than 40% in the far infrared region (wavelength: 6 to 15 lm), the temperature rise speed of the outer propylene polymer layer becomes slower.
As a result, the processing time may be very long, the temperature of the contents may be high during processing (e.g. above 90°C, and in extreme cases above 100°C), the contents may change or the internal pressure of the container may increase. This is undesirable because it causes the container to rise and deform.

That is, the processing time can be significantly shortened by simultaneously having near/mid infrared rays with a wavelength of 2 to 4 JL11 and far infrared rays having a wavelength of 6 to 15 gm, or by using two types of heaters.

In other words, infrared rays with wavelengths of 2 to 41 Lta and 6 to 15 Lta are used to raise the temperature of the propylene polymer layer (outer layer 2) to a high temperature state (significantly increase the amount of water vapor permeation), and at the same time, with wavelengths of 2 to 4 p- By evaporating the moisture in the saponified layer 3 of the ethylene-vinyl acetate copolymer with infrared rays of m, the processing time for removing the moisture in the saponified layer 3 from the container can be greatly shortened.

The water content of the saponified ethylene-vinyl acetate copolymer balanced under normal atmospheric conditions (e.g., temperature 20°C, relative humidity 60%) is 1-3% (depending on the mol% ratio of ethylene in the saponified material). 1~
Even if dried to a moisture content lower than 3%, the moisture content will rise to 1-3% during storage, so there is no point in drying it below this moisture content. On the other hand, if the moisture content exceeds 10% due to insufficient drying, ethylene
The oxygen permeability of the saponified vinyl acetate copolymer film is 6 to 1 occ.20 color Il/rrf.day at a temperature of 23°C and 1 atmosphere of oxygen. (It varies slightly depending on the copolymerization ratio of ethylene) 1) It is insufficient to prevent normal changes and deterioration of the contents. Furthermore, if the moisture content is lowered to 10% or less, the moisture content will drop to 1 to 3% during normal storage so as to be in balance with the humidity in the atmosphere.

The processed material of the container of the present invention is not limited to the above examples, and for example, in cases where the container is not a microwave oven container, a container made of a metal sheet (for example, an aluminum sheet, a tin-plated steel sheet) may be used for sealing. The part may be wrapped around the body of the molded container, or double-sealed.

(Examples and Comparative Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples.

The permeability of each sample was measured using a vapor permeation tester (Model L80, manufactured by Ridge Co., Ltd. (Switzerland)) at a measurement temperature of 38° C. and a relative humidity of 90% using the sheet before molding. In addition, the oxygen permeability of each sample was measured using an oxygen permeation measuring device (Motancon L-Rho) Lt.
0X-TRAN 10150, manufactured by U.S.A.) at a measurement temperature of 23° C., the relative humidity inside the container was 90%, and the relative humidity outside the container was 60%.

Moreover, FIG. 1 is a sectional view of containers manufactured in Examples and Comparative Examples. Furthermore, FIG. 2 is a partially enlarged sectional view of FIG. 1.

In FIG. 1, 4 is a heat seal portion, and 5 is a flange. In addition, 9 is the bottom wall part, and 10 is the contents (
For example, salad oil). Furthermore, 11 is a lid. Further, in FIG. 2, 1 is an inner layer, and 2 is an outer layer. Further, 3 is an intermediate layer, and 6 and 7 are adhesive resin layers.

Example 1 As an inner layer material, 85 parts by weight of an ethylene-propylene flock copolymer (ethylene copolymerization ratio 18% by weight) with a VFR (1) of 0.5 g/10 min and an MFR (3) or 0
．． Ethylene homopolymer (density 0
．． A mixture consisting of 15 parts by weight (955g/cm') was prepared using an extruder with a diameter of 511I11 to a thickness of 0.95g/cm'.
A sheet with a width of 8 mm and a width of 680 cm was produced. Furthermore, a film of the same mixture as the inner layer material was used as the outer layer material and had a thickness of 100 p-rs, and as an intermediate layer, a saponified product of ethylene-vinyl acetate copolymer with an ethylene copolymerization ratio of 38 mol% [saponification degree 99%, VFR (2)
4.0 g/10 minutes, hereinafter referred to as rEVOHJ) to produce a film with a thickness of about 40 gm.

A polyester adhesive (manufactured by Toyo Morton Co., Ltd., Model AD-950A/B) was applied between the outer layer film and the saponified ethylene-vinyl acetate copolymer (as an intermediate layer) at a nip temperature of 80°C. Using a tri-laminator (manufactured by Okazaki Materials Industry Co., Ltd.), the coating was applied uniformly at a coating weight of 3.5 g/rn'.

The laminated sheet was then laminated at a nip temperature of 80°C, and then knee-sinked at 40°C for 7 days. Manufactured. A polyester adhesive is applied to the saponified ethylene-vinyl acetate copolymer side of the obtained laminated sheet in the same manner as described above, and the inner layer material is laminated on the coated side and dried to form a laminated sheet (thick A diameter of 0.93 μl and a width of 680 mm) was manufactured. The amount of water vapor permeated through the outer layer was 10 times that of the inner layer. The sheet thus obtained was then vacuum-formed (manufactured by Asano Research Institute, model FLV 441) with a diameter of 81 mm.
．． 2. A container with a depth of 70 cm and a capacity of 230 cc was molded.

The container obtained in this way is filled with water to 5% of the total content or the empty space, and with an aluminum foil of 20 Bm thick interposed on both sides, a propylene polymer with a thickness of 60 mm is prepared. 2. Place the lid on the lid at a temperature of 200°C and a pressure of 2.
Link sealing was performed for 3 seconds at 5 kg/crn' to obtain a container filled with water. Put this container into a retort pot (manufactured by Daiwa Seikasha, model: IIR-W-101M).
Retort treatment was carried out for 30 minutes at a temperature of 125°C. No deformation of the container could be observed.

After that, an infrared ray heater with an emissivity of about 80% in the near-mid infrared region of wavelengths 2 to 4 I and an emissivity of 80% in the far infrared region of 6 to 25 gm (the heater's radiation The outer layer was dried for 30 minutes (total drying time was 33 minutes) using a dryer (shown as ■ in Figure 3) while controlling the surface temperature of the outer layer at 120°C. After drying, the oxygen permeability of this container is 0.0 at 1 atmosphere of oxygen.
It was 4cc/24 hours. Furthermore, the thickness distribution of the inner layer is 0.3 to 0.6 lll1, and the thickness distribution of the outer layer is 0.
．． It was 05-0.08■.

Examples 2 to 5 Drying was carried out in the same manner as in Example 1 except that the drying time was changed as shown in Table 1, and Table 1 shows the oxygen permeability under 1 atmosphere of oxygen.

Table 1 Example 6 Instead of infrared drying in Example 1, 95°
Drying was performed while blowing hot air of C (wind speed: 1 m/sec, relative humidity: 10%). The oxygen permeability of the obtained container was 0.020 cc for 724 hours under 1 atmosphere of oxygen. The moisture content of EVOH was 3%.

Example 7 Three types of upper layer sheet forming machine (manufactured by Toshiba Machine Co., Ltd., diameter 40m1I)
1. L/D 26. Diameter 90mII, L/D 2
8. Diameter 65am.

L/D28, T-tie, 100mm width, die temperature 2
30'C) and propylene homopolymer (MFR (1) 0.5g / 10 minutes) 1 as the adhesive resin.
0.00 parts by weight. : 1Oi4FiS part of maleic anhydride is crafted using benzoyl peroxide (as a radical initiator) Seta VFR (1) 2.5g/10
An outer layer sheet with the same thickness as in Example 1 was molded using the same amount of resin (each adhesive resin layer had a thickness of 20 g).
m). As a result, 0.045c at 1 atmosphere of oxygen
c/24 hours.

Comparative Example l The oxygen permeability of a container that was not dried with hot air as in Example 1 was 4.5c under 1 atmosphere of oxygen.
It was 724 hours.

Comparative Example 2 The same procedure as Example 1 was used, except that a laminated sheet using a film made of a mixture of the ethylene-propylene floc copolymer and ethylene homopolymer used as the outer layer agent in Example 1 and having a thickness of 25 gm was used. A container filled with water was manufactured in the same manner. The container thus obtained was dried in the same manner as in Example 1, and the oxygen permeability under 1 atmospheric pressure of oxygen was measured. The ratio of the water vapor permeability of the outer layer to the water vapor permeability of the inner layer was 40. As a result, the oxygen permeability was 0.02 cc/24 hours under 1 atm. However, the oxygen permeability at a temperature of 50° C. and relative humidity of 95% was very poor at 1.5 cc/24 hours under 1 atmosphere of oxygen, and the outer layer was frequently damaged during the distribution stage, making it difficult to use. Furthermore, the thickness distribution of the inner layer is 0.3 to 0.6
The thickness distribution of the outer layer was 15 mm.

Comparative Example 3 Emissivity in the near and mid-infrared region of wavelength 2 to 4 gl is approximately 2
The experiment was carried out in the same manner as in Example 1, using a heater having an absorption spectrum indicated by ■ in FIG. 3, which is 5%. When drying was carried out for a total drying time of 33 minutes, the oxygen permeability was -1.2 cc for 724 hours under 1 atmosphere of oxygen.

Further, when drying the outer layer at a surface temperature of +20° C. for 130 minutes, the drying time was extremely long at 55 minutes. At this time, the oxygen permeability is 0.1cc/under 1 atmosphere of oxygen.
It was 24 hours.

Comparative Example 4 A test was carried out in the same manner as in Example 1 using a heater. When drying was carried out for a total drying time of 33 minutes, the oxygen permeability was 1.0 cc/24 hours under 1 atmosphere of oxygen. Furthermore, when the surface temperature of the outer layer was 120'C for 30 minutes, the drying time was as long as 45 minutes. The oxygen permeability at this time is 0.2cc/2 under 1 atmosphere of oxygen.
It had been four hours.

Comparative Example 5 The same procedure as in Example 1 was carried out, except that the thickness of the outer layer was 0.8 cm. Oxygen permeability is 1.6 under 1 atmosphere of oxygen.
It was cc/24 hours. The thickness distribution of the inner layer is 0.3 to 0.
．． 6■, and the thickness distribution of the outer layer is 0.30~.

It was 0.55mm+. The oxygen permeability at this time was 3.0 cc/24 hours under 1 atmosphere of oxygen. Also, if the drying time is 2.5 hours, the drying time is 1.0 cc/24
It only improved over time.

〔Effect of the invention〕

The container obtained by the treatment method of the present invention exhibits the following effects.

In other words, it only has excellent gas barrier properties.
This is a thermoplastic resin container that does not rot, deteriorate, or denature its contents even if stored for a long time after retort heat sterilization.

The container obtained by the method of the present invention can be used in a wide variety of ways to achieve the above-mentioned effects. Typical uses are shown below.

(1) Various processed seasoning food containers (2) Various liquid food containers (3) Various food containers (4) Various industrial chemical containers

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of containers manufactured in Examples and Comparative Examples. Moreover, FIG. 2 is a partially enlarged sectional view of FIG. 1. Furthermore, FIG. 3 is a diagram showing the relationship between the wavelength of radiation and the emissivity of each infrared heater used in the examples and comparative examples. In Figure 3, the vertical axis is emissivity (%),
The horizontal axis is the wavelength (final m). ■・・・Inner layer, 2...Outer layer, 3...
...Middle layer, 4...Heat seal part, 5...
...Flange. 6 and 7...Adhesive resin layer, 9...
Bottom wall portion, 1O... Contents, 11... Lid.

Claims (1)

[Claims] A saponified layer obtained by saponifying at least 80% of an ethylene-vinyl acetate copolymer having an ethylene copolymerization ratio of 15 to 60 mol% is interposed, the inner and outer layers are propylene polymer layers, and the outer layer thickness of 30
After filling the container with the contents of ~200 μm and sealing it, the container is treated with steam or hot water, and the content is at least 40% in the infrared region with a wavelength of 2 to 5 μm, and furthermore, it is in the far-field region with a wavelength of 6 to 25 μm. A method for treating a container, comprising reducing the water content of the saponified layer to 10% or less using an infrared heater having an emissivity of 40% or more in the infrared region.