JPS62128754A - Packaging material having excellent hot water resistance - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a packaging material excellent in hot water resistance and gas permeation resistance, and particularly to a packaging material for retorts.

B. Conventional technology Conventionally, saponified ethylene-vinyl acetate copolymer (hereinafter E
VOH) is widely known as a thermoplastic resin with excellent gas permeability, oil resistance, and solvent resistance, and is used in various packaging fields, and is particularly suitable for food packaging films, containers, containers, etc. It has been used in

However, EVOI (EVOI) is sensitive to water and swells, softens, and deforms when it comes into contact with hot water, so it can be used not only as the outermost layer of packaging materials for foods that require boiling or retort sterilization, but also for packaging of substances containing moisture. It cannot be used in the inner layer of the material.Also, even if EvOH is in the middle layer, boiling or retort processing may cause deformation of the container, protrusion, wrinkles, and poor visibility of the end surface. During! IIQ occurs.

Therefore, EVO)t′! No satisfactory retort packaging material has been obtained as an i-constituent material.

C5 Problems to be Solved by the Invention The present invention aims to provide a packaging material for retorts which is free from the drawbacks listed in item-11 and has excellent hot water resistance and gas permeation resistance.

As a result of intensive research, the present inventors have found that the third component is represented by the following general formula (1), and if necessary, a hot water resistance improving aid is added to the modified fi;VOH. The present invention has now been completed.

CH2=CH-C-N-R'-0-R2 (1)H CR1 is a lower alkylene group R2 is a saturated branched or unbranched alkyl group having 1 to 40 carbon atoms) E1 Effects Using the modified EVOH according to the present invention The laminated films, sheets, containers, etc. that use EVOH have superior hot water resistance compared to conventional EV
Gas permeability and fragrance retention comparable to those using Ol (
It has oil resistance and is suitable for use in various packaging fields, particularly in the food packaging field, and in the food packaging field that requires boiling or retort killing treatment.

More detailed explanation of the F1 invention The kVOfi of the present invention is expressed by the following general formula (1).
.

A saponified modified ethylene-vinyl acetate copolymer containing a third component with an ethylene content of 20 to 60 mol%, preferably 20 to 55 mol%, and a saponification degree of the vinyl acetate component of the copolymer of 95 mol%. Above, the content of the third component is 0
．． 5 to 5 mol is suitable. A more preferred range of the third component is 0.5 to 3 mol.

(R1 is a lower alkylene group; R2 is a saturated branched or unbranched alkyl group having 1 to 40 carbon atoms) If the ethylene content is as low as 20 moles, not only will it be difficult to achieve the effects of the present invention, but also Gas permeability is impaired. Furthermore, if the ethylene content exceeds 60 mole percent or the degree of saponification is less than 95 percent, the gas permeability will decrease. Furthermore, if the content of the third component is less than 0.5 mol, the effect of the present invention is difficult to achieve, and if it exceeds 5 mol, the gas permeation resistance decreases and the original characteristics of EVO) 1 cannot be maintained. It disappears.

The EVOH of the present invention can be industrially produced by a conventionally known method. That is, in the presence or absence of alcohol such as methanol, ethylene, vinyl acetate, and the substance represented by the above general formula (1) are mixed with a known radical polymerization initiator such as α, d-azobisisobutyronitrile. The copolymer is then copolymerized using the above-mentioned general formula (1). The substances shown are used: N-methoxymethylacrylamide, N-methoxymethylacrylamide, N-ethoxymethylacrylamide, N-(n-propoxymethyl)acrylamide, N-isopropoxymethylacrylamide,
Preferred are (n-butoxymethyl)acrylamide, N-(n-butoxyethyl)acrylamide, N-imbutoxymethylacrylamide, and particularly preferred is N-(n-butoxymethyl)acrylamide. The lower alkylene group for R1 preferably has 1 to 5 carbon atoms.

The preferred number of carbon atoms in the alkyl group of f9R2 is 1 to 20.

Although the modified gvou of the present invention can be used alone as a packaging material, it is preferably used in a laminate with other thermal OT WJ resins. In this case, the gVO1-11 layer is an inner layer, an outer layer,
It can be used in any intermediate layer, and in particular can be boiled or retorted even when used in the outermost layer, something that conventional EVOH cannot match at all.

As a method for forming the laminate, known methods such as co-extrusion, co-injection, laonation, and solution coating can be applied. In this case, as an aid for improving the hot water resistance of avou, ammonium salts of strong acids such as ammonium chloride and ammonium sulfate, inorganic acids such as sulfuric acid and sulfuric acid, oxalic acid, lactic acid,
Organic acids such as acetic acid and formic acid are mixed with gvoH and heat treated.

In the case of single melt molding, coextrusion, and coinjection, the [η
] (Intrinsic viscosity measured at 30°C in a mixed solvent of 85 ft% phenol and 15 ft% water) is 0.07 to 0.
．． 1771/? is preferred, but this is determined by bath melt moldability and viscosity compatibility with the partner resin.

In the case of solution coating, EVOI ([η] is 0.
03~0.127! /f is preferred. The lower the viscosity, the better from the viewpoint of workability in solution coating, and from the mechanical properties of -Aco-), if [η] is too low, it will be a practical problem.

The various laminate containers thus obtained are suitably used as packaging containers for boiled or retort foods. The present invention will be explained in more detail with reference to examples below.
This example does not limit the invention in any way. (Example A shows weight % unless otherwise specified) G, Example 1 N-(n-butoxy7methyl)acrylamide content 1 mol%, ethylene content 32 mol%, acetic acid Modified EV O1 with a saponification degree of vinyl component of 99.2 mol (((η))=0.
No. 11 was supplied to an extruder and melted into a film using a T-shaped die at 220° C. to obtain a film with a thickness of 15 μm. This film is 5
After soaking in a 10% ammonium chloride aqueous solution at 0°C for 2 minutes, the surface was washed with water, dried at 80°C, and further heat-treated at 120°C for 15 seconds. 11, Mitsui Polyke Bakal type) 50
Extrusion coated at 300℃ to a thickness of μ, EVOH/
A bilayer film of polyethylene was obtained. A bag was made from this laminated film with the gvoH layer as an outer layer, and the oxygen permeability and hot water resistance were examined. Table 1 shows the results.

Control row 1 Ethylene content 32 mol%, saponification degree of vinyl acetate component 9
A bag of kVOH/polyethylene/two-layer film was obtained in the same manner as in Example 1 using 9.3 molti unmodified EVOH ([η] = 0.1), and an experiment similar to Example 11 was conducted. . The results are shown in Table 1.

Control example 2 N-(n-butoxymethyluacrylamide-containing -fil
Modified EVOI ([η] = 0
．． A bag of EvOH/polyethylene NiJ So film was obtained in the same manner as in Example 1 using 0853, and an experiment similar to that of the FJ I was conducted. The results are shown in Table 1.

Table 1 *) Measurement after humidity conditioning in an atmosphere of 20°C and 65% RH **) State after immersion in water at 120°C for 30 minutes in an autoclave Example 2 Contains N-ethoxymethylacrylamide 2 moles %, contains ethylene! 35 mol%, If- of vinyl acetate component
jA, denaturation with a degree of 99.2 mol% vOH ([η]=
0.07) in a mixed solvent of n-gropanol/water (55/45 ratio) (containing 0.5% ammonium chloride).
At 0℃? A bath liquid having an EVOk-1 degree of 15 degrees was obtained.

Stretch-blow molded polypropylene (Noblen MA-6. Mitsubishi Yuka Kesha), volume 0.5 g, body thickness 0.6 ms
After applying 10μ of urethane adhesive (AL)-300 (manufactured by Toyo Morton) to the bottle, it was immersed in the above EVOH solution, dried at 80 °C, and then heat-treated at 110 °C for 15 seconds.
A container with a zvoH coating layer having a thickness of 8μ was obtained. The results of examining the oxygen permeability, carbon dioxide gas permeability, and hot water resistance of this container are shown in Figure 2.

Control example 3 N-ethoxymethylacrylamide acid containing 5.5 mol%,
Ethylene content 35 mol%, saponification of vinyl acetate component J&
Using 99.2 mol % o modified EVOH ([η) = 0.071, a bottle was obtained through the same operation as in Example 2, and an experiment similar to Example FIIJ 2 was conducted. The results are shown in Table 2.

Control Example 4 N-ethoxymethylacrylamide content t2 mol%, ethylene content 15 mol%, saponification of vinyl acetate component 99.
Using 3 molti of modified EVOH ([η) = 0.09), a bottle was obtained through the same operation as in Example 2 (however, the mixed solvent composition was n-globanol/water = 40/60), and the Example An experiment similar to 2 was conducted.

The results are shown in Table 2.

2 2 *) 20℃, 80℃ R1 (temporary humidity control measurement in the atmosphere **)
Condition after immersion in water at 120°C for 30 minutes in an autoclave Example 3 N-isobutoxymethylacrylamide content 3 mol%,
Ethylene content: 40 mol Saponification degree of vinyl thiacetate component: 99
．． The middle layer is 3molti modified EVOH ([η]=0.095), and the inner and outer layers are polypropylene (Noprene MA-
6. (manufactured by Mitsubishi Yuka), and the adhesive layer is made of modified polypropylene (Atomer QF500. Mitsui Petrochemical #), with three types of 5 f
An f4 iJt/@body sheet was obtained by coextrusion. This sheet is produced at a temperature of 145°C using the solid phase air pressure forming method.
Under the conditions: inner diameter 100 rxx, depth 100 mg, wall thickness 0
．． The thickness ratio of the outer layer, adhesive layer, intermediate layer, adhesive layer, and inner layer is 45:2.5:5:2.5 to obtain a 5 as cylindrical cup.
:45. Table 3 shows the results of examining the oxygen permeability and hot water resistance of this cup.

Control example 5 N-isobutoxymethylacrylamide content 03 mol%
, a modified EVOH with an ethylene content of 40 mol% and a saponification degree of vinyl acetate component of 99.3 mol ([η]=0.095)
was treated in the same manner as in Example 3 to obtain a cup, and the same experiment as in Example 3 was conducted. The results are shown in Table 3.

Table 3 *) Temporary humidity control measurement in an atmosphere of 20°C and 851RH **) Condition after immersion in water at 120°C for 30 minutes in an autoclave Example 4 Using the EVOH/polyethylene two-layer film obtained in Example 1, 12α × A bag with a size of 16cn1 was prepared, filled with cooked curry sauce and heat-sealed, and then retort sterilized in an autoclave at a heated water temperature of 120°C for 30 minutes. When this was stored at room temperature, there was no change in color or taste even after 6 months.

On the other hand, as a result of conducting a similar experiment using the two-layer film obtained in Control 911, the curry changed color and started to rot after 4 days.

Claims (2)

[Claims] (1) The saponification degree of the vinyl acetate component of the modified ethylene-vinyl acetate copolymer is 95 mol% or more, the ethylene content is 20 to 60 mol%, and the third component is represented by the following general formula (I). A packaging material having excellent hot water resistance and comprising a saponified modified ethylene-vinyl acetate copolymer having a content of 0.5 to 5 mol%. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (R^1 is a lower alkylene group, R^2 is a carbon number of 1 to 40
saturated branched or unbranched alkyl group) (2) A packaging material with excellent hot water resistance according to claim 1, wherein the packaging material is a retort packaging material.