KR910009516B1 - Vassel for food package - Google Patents

Abstract

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Description

Food Sealant Container

Figure 1a is a vertical cross-sectional view of the container according to the present invention.

FIG. 1B is a vertical sectional view of the lid covering the container of FIG. 1A.

FIG. 2 is a partially enlarged cross-sectional view of a synthetic resin coating layer formed on a metal foil through an intermediate layer in the container of FIG. 1A.

The present invention relates to a container for food sealing, and more particularly, to a container for sealing a cooked food that can be eaten by reheating.

2. Description of the Related Art Conventionally, retort foods that have been completely bacterium are well known by placing sealed foods such as curry and stew in a plastic bag such as polyethylene and sealing them by heat sterilization in a retort. This retort food is reheated in boiling water with a bag just before serving to a table.

Some cooked foods need to be heated to the point where the surface is slightly delayed when reheating such as gratin or hamburger. Since such foods need to be heated to a high temperature of about 250 ° C. with an electric oven or an oven toaster, such plastic bags as used in retort foods do not have heat resistance to such high temperatures even if they are sufficiently resistant to hot water temperature. Therefore, the gratin, hamburger, etc. were conventionally put in metal containers, such as aluminum. However, since it is not sealed like a plastic bag, retort sterilization cannot be performed and inevitably has been frozen for long term storage. Foods frozen in this way must be kept frozen at all times after purchase in the product distribution process, must be thawed before being eaten, and there are also grooves that have a lower taste than retort foods.

Therefore, the present applicant first proposed a food sealing container that is sealed and sterilized, even if it is cooked food necessary for high temperature reheating, regardless of coldness (Japanese Patent Application No. 63-94173). The proposed container is a flanged metal foil container in which a synthetic resin coating layer made of an epoxy resin and a polypropylene resin modified with an unsaturated carboxylic acid or an acid anhydride is formed on the inner surface of the container body and the upper surface of the flange. .

The flanged metal foil container is molded by deep drawing, but when it has a synthetic resin coating layer as described above, it should not be peeled off during molding. The same can be said for the heat sterilization by retort.

Even in the above-mentioned container, although there is no problem with respect to the above point, there are some disturbances in the adhesion between the metal film and the synthetic resin coating layer and the water vapor resistance.

An object of the present invention is to provide a food-sealed container in which cooked foods requiring high-temperature reheating are retorted and sterilized by sealing without refrigerating, and improved on the above points.

In order to achieve the above object, the container for food sealing according to the present invention is modified as 30-90 parts of an epoxy resin, an unsaturated carboxylic acid or an acid anhydride over the entire inner surface of the container body and the upper flange surface in a flanged metal foil container. The synthetic resin coating layer which consists of 5-50 parts of polypropylene resin, 1-5 parts of polyisocyanate resin, and 0.1-5 part of silane coupling agents is formed.

In this specification, parts are based on weight.

As for the thickness of a metal foil, 40-150 micrometers is preferable. If it is less than 40 µm, the strength is insufficient, and if it exceeds 150 µm, not only is it difficult to form, but also the cost is high. As metal foil, aluminum foil is preferable.

As a specific example of an epoxy resin, the reaction product of polyhydric phenols, such as epichlorohydrin and bisphenol A, is mentioned. Epoxy resins are polyisocyanates which do not generate toxic formalin, 2,4- or 2,6-triene diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, Or these adducts, blocked isocyanates, or polymers thereof.

In addition, in order to increase the curing speed of the epoxy handmade, 1-10 parts of thermosetting resins, such as a phenol resin, an acrylic modified epoxy resin, an acrylic modified styrene resin, an alkyd resin, and a polyvinyl butyral resin, may be added. In particular, it is most effective to add 1-10 parts of phenol resin. The polypropylene resin modified as unsaturated carboxylic acid or its acid anhydride is a polypropylene resin graft copolymerized with maleic anhydride, and preferably contains 0.05-5 parts of maleic anhydride in terms of adhesion to aluminum described later. .

Among the coupling agents, silane coupling is particularly preferred.

Compositions of polypropylene resins, polyisocyanate resins and silane coupling agents modified with epoxy resins, unsaturated carboxylic acids or acid anhydrides thereof are coated with cellosolve acetate, cellosolve, methyl ethyl ketone, toluene and the like, By applying to the metal foil, a synthetic resin coating layer is formed.

According to the present invention, since the synthetic resin covering layer including 30-90 parts of epoxy resin and 5-50 parts of polypropylene resin modified with unsaturated carboxylic acid or its acid anhydride is formed on the entire inner surface of the container body and the upper surface of the flange, the container flange By heat-sealing the lid, the container filled with the cooked food can be sealed, and even if the cooked food is opened and reheated at a high temperature by an electric oven, the synthetic resin coating layer does not discolor or dissolve and impair the aesthetics. . This is because the epoxy resin has high heat resistance, and the polypropylene resin modified with unsaturated carboxylic acid or its acid anhydride has excellent heat adhesiveness, respectively, so that the synthetic resin coating layer has both of these properties. If the epoxy resin is less than 30 parts, dissolution occurs in the synthetic resin coating layer at the time of reheating due to high temperature, and if it is more than 90 parts, thermal adhesiveness becomes insufficient. On the other hand, if the modified polypropylene resin is less than 5 parts, the thermal adhesiveness is insufficient, and the sealing property of the container is impaired, and if it exceeds 50 parts, the heat resistance is problematic. In the present invention, the synthetic resin coating layer has the former of 30-90 parts, the latter. Since is in the range of 5-50 parts, there is no problem. It is especially preferable that the former is 60-90 parts and the latter 10-30 parts within these ranges.

In addition, since the polypropylene resin does not have sufficient affinity with a metal and is not modified as described above, the synthetic resin coating layer is easily peeled from the metal, but is modified to improve adhesiveness by unsaturated carboxylic acid or its acid anhydride. Therefore, there is no problem at this point.

In addition, 1-5 parts of polyisocyanate resin as a hardening | curing agent of an epoxy resin does not generate formalin at the time of high temperature heating, and is joined for the use of this invention. Examples of the curing agent for epoxy resins include formaldehyde-modified resins such as melamine resins, urea resins, and benzoguanamine resins, but they are not preferable because they generate formalin at high temperatures.

As a composition of 30-90 parts of epoxy resin, 5-50 parts of modified polypropylene resin, and 1-5 parts of polyisocyanate resin, the pin synthetic resin coating layer not only has high heat resistance and excellent heat adhesiveness, but also has good moldability. Addition to 0.1-5 parts of silane coupling agents above helps to improve moldability. The silane coupling agent has good adhesion between the metal foil and the synthetic resin coating layer. However, the silane coupling agent has no effect at less than 0.1 part, and the effect is almost equal even when added in excess of 5 parts. As the coupling agent, a titanate coupling agent and a zircoaluminum coupling agent are also used as the coupling agents. However, these additions are not preferable because they are ineffective and may be partially gelled.

In short, according to the food-sealing container of the present invention, not only frozen foods requiring high temperature reheating are sealed by freezing, but also retort sterilization, and both water vapor resistance and adhesion are improved as compared with the proposed container of the base material. Therefore, there is no fear that the aluminum foil and the synthetic resin coating layer peel off during retort sterilization or tip drawing.

Since foods generally contain salts, acidic seasonings, or spices that are susceptible to corrosion of metal foils such as aluminum foils, an intermediate layer of zirconium-containing synthetic resins or chromium-containing synthetic resins containing trivalent chromium compounds is interposed between the metal foil and the synthetic resin coating layer. It is preferable to make it.

The zirconium-containing synthetic resin intermediate layer is formed by using a treatment solution in which a zirconium compound, an olefin polymer, and a polymer having a hydroxyl group or a carboxyl group are mixed in an aqueous solution or an emulsion state. As a zirconium compound, the alkali metal salt, ammonium salt, etc. of ammonium zirconium carbonate and a fluoro zirconate are mentioned, for example. As the olefin polymer, ethylene, propylene, 1-butene, 2-butene, isobutylene, 1-benten, 2-benten, 2-methyl-2butene, 1-hexane, 2,3-dimethyl-2-butene And polymers of 1-heptene, 1-octene, 1-nonene and 1-decene. Especially, it is preferable to use the polymer of ethylene and propylene. Examples of the polymer having a hydroxyl group include polyvinyl alcohol and hydroxyethyl ether of cellulose. Polyacrylic acid may be cited as the polymer of the carboxyl group, but polyacrylic acid is particularly preferable.

Next, the mixing ratio of acid 3 will be described. For the olefin polymer, 10-95 parts, in particular 60-90 parts are preferred. The addition of the olefin polymer helps to improve the moldability of the skin itself. As for the polymer which has a hydroxyl group or a carboxyl group, 5-90 parts, especially 10-40 parts are preferable. The addition of a polymer having a hydroxyl group or a carboxyl group is intended to make the mixture of both polymers water soluble as a whole, but especially when the olefin polymer is more than 95 parts, the polymer mixture becomes not water soluble in its entirety. As for the ratio of a zirconium compound, the ratio of a zirconium compound and the said weak polymer total is preferable with respect to a zirconium compound 1 in 0.5-10 part, especially 1-5 part in total of the said copolymer.

As a method for forming the zirconium-containing synthetic resin intermediate layer, any method such as spraying method, immersion method, roll coating method, or brush coating method can be adopted. Moreover, it is preferable to perform drying after formation of an intermediate | middle layer at 15-300 degreeC. The drying time depends on the drying temperature, for example, about 1 minute at 200 ° C. It is preferable that the zirconium adhesion amount in this intermediate | middle layer is 0.1 mg / m <^2> or more. Zirconium contributes to the improvement of corrosion resistance, but is less effective at less than 0.1 mg / m ² . On the contrary, not only is there a great serious corrosion resistance effect, but also the adhesiveness with the synthetic resin coating layer deteriorates, the coating layer at the time of container linearity is easy to peel off, and it is easy to discolor at the time of high temperature heating by an electric oven or the like. In particular, the preferable attachment range is 0.5-100 mg / m ² . The zirconium adhesion amount may be set by adjusting the blending ratio of the zirconium compound and the polymer having an olefin polymer and a hydroxyl group or a carboxyl group in the preparation step of the treatment liquid, and to adjust the coating amount of the treatment liquid to the metal foil. You may carry out. 0.5-5000 mg / m <^2> is preferable at the point of application | coating thickness, etc. at this time. In particular, 3-300 mg / m ² is preferable.

Specific examples of the epoxy resins include reaction products of epichlorohydrin and polyhydric phenols such as bisphenol A. As a hardening | curing agent of an epoxy resin, polyisocyanate is preferable, As a specific example, paraphenylene diisocyanate, 2,4- or 2,6-toluene diisocyanate, 4,4'- diphenylmethane diisocyanate, hexamethylene diisocyanate, Or these adducts, blocked isocyanates, or polymers thereof.

Instead of using a zirconium-containing synthetic resin for the intermediate layer, when a chromium-containing synthetic resin containing a chromium compound of trivalent chromium is used, the thickness thereof is preferably 5 µm or less. That is, the middle layer is the 0.005-5g / m ² preferably on one side of the metal foil is formed at a rate of 0.1-1g / m ^2. Moreover, it is preferable that a trivalent chromium compound of the ratio of 0.1-100 mg / m <^2> is contained in the intermediate layer calculated as chromium. If the content of the trivalent chromium compound is less than 0.1 mg / m ² , sufficient corrosion resistance cannot be obtained. If the content of the trivalent chromium compound is more than 100 m / m ² , the intermediate layer is likely to be peeled off with a metal foil when forming a container, There is a possibility of discoloration by high temperature heating, which is not preferable.

Such a chromium-containing synthetic resin intermediate layer is formed by applying a treatment liquid containing a trivalent chromium compound, water and synthetic resin to one side of a metal foil by a gravure cord method or a roll coat method and drying it.

As the chromium compound, inorganic compounds such as various salts and oxides containing trivalent chromium are used. As the synthetic resin, polyacrylic acid, polyvinyl alcohol, ethylenemaric anhydride, polyvinylmethyl ether and the like are used. Among them, polyacrylic acid is preferable. These synthetic resins are used in the form of a solution or in the form of an emulsion in a solvent. In order to dissolve the chromium compound, the treatment liquid contains water.

Embodiments of the present invention will be described below with reference to the drawings.

Example 1

The container 1 is comprised as the flange 3 provided in the correlation of the container main body 2 and the circumferential wall, as shown in FIG. 1A. This container 1 is, on one side of an aluminum foil 4 having a thickness of 120 µm, 30 parts of an epoxy resin, 30 parts of a polypropylene resin modified as an unsaturated carboxylic acid or an acid anhydride thereof, 3 parts of a polyisocyanate resin, and 5 parts of a phenol resin. And 4 g / m ² (in terms of solids content) of the composition comprising the second part of the cinnamic coupling, to form a laminate having the coating layer 5 formed in a predetermined shape, and then the synthetic resin coating layer 5 is formed of the container body 2. Deep drawing is formed to be inside.

The lid 6 shown in FIG. 1B is a laminate in which an unstretched polypropylene film 8 having a thickness of 5 µm is laminated as a heat sealant on an aluminum foil 7 having a thickness of 70 µm.

The following experiment was performed about the said container 1. That is, after putting 180 g of cooked gratin into the container body 2, the lid 6 was covered and the peripheral edge thereof was heat sealed to the flange 3 of the container 1. Next, these gratins were subjected to a retort sterilization treatment at 120 ° C. for 30 minutes. The lid 6 was then removed and the gratin jar 1 was placed in an oven toaster and heated to about 250 ° C. for 15 minutes. As a result, the surface of the gratin had a dark brown pressed color, but no change was recognized in the synthetic resin coating layer 5 of the container 1.

Example 2

In Example 1, the zirconium-containing synthetic resin intermediate layer 3 is interposed between the aluminum foil 4 of the container 1 and the synthetic resin layer 5. As a zirconium-containing synthetic resin for forming the intermediate layer 9, a mixture of 13% ZrO ₂ and 87% water and 13% aqueous solution of a composition consisting of 80 parts of ethylene and 20 parts of polyacrylic acid was used as a stock solution, which was diluted and used. . Although the adhesive bond layer 10 is interposed between the intermediate | middle layer 9 and the coating layer 5 as shown in FIG. 2, this can be abbreviate | omitted.

Example 3

This example uses chromium-containing synthetic resins containing trivalent chromium chromium compounds instead of zirconium-containing synthetic resins in the intermediate layer 3 in Example 2.

As this chromium-containing synthetic resin, the liquid containing 3500 ppm of polyacrylic acid 3500 ppm trivalent chromium was diluted and used.

In each of the above embodiments, a protective coating layer made of an epoxy resin, a thermosetting acrylic resin, or the like may be formed on the outer surface of the container to prevent corrosion of the outside of the container. The thickness of a protective coating layer is 10 micrometers or less.

Claims (3)

Flanged metal foil container, comprising: 30-90 parts of epoxy resin, 5-50 parts of polypropylene resin modified with unsaturated carboxylic acid or its acid anhydride, and 1-5 parts of polyisocyanate, all over the inner surface of the container body and the upper surface. And a synthetic resin coating layer composed of 0.1-5 parts of a silane coupling agent. The food-sealed container according to claim 1, wherein a zirconium-containing synthetic resin intermediate layer is interposed between the metal foil and the synthetic resin coating layer. The food sealing container according to claim 1, wherein a chromium-containing synthetic resin intermediate layer containing a trivalent chromium compound is interposed between the metal foil and the synthetic resin coating layer.

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