JP3225245B2 - Heat sealing material for hermetically sealed containers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyether for sealed packaging.
Tylene container, polypropylene container, polystyrene container,
Also , the present invention relates to a heat-sealing lid material used for a container for hermetic packaging made of a paper container coated with polyethylene .

[0002]

In recent years, with the development of packaging technology, various chemicals, foods and beverages, and increasingly be packaged by filling in a container of the above Symbol, in such a case, not only the sealing of the container only, The demand for easy opening during use has become very high.

[0003]

However, in the case where the opening property is improved, when the lid material and the container body are thermally bonded at a high temperature after filling the contents, there is a rise in the temperature of the head space of the sealing body, There is a problem that the internal pressure is increased and the heat-bonded portion is peeled off. Furthermore, as the content, when the hot-fill method of filling and sealing a heat sterilized foods in a heated state orゝ(80 ° C. or more) containers <br/> device described above, this problem is likely more generated Was.

Therefore, conventionally, in order to satisfy the function of the sealing property of the container, peeling of the heat-bonded portion has been prevented at the expense of opening, so to speak, but there has been a problem of incompleteness.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a polyethylene container and a polypropylene container for hermetically sealed packaging.
Wrench container, polystyrene container, or polyethylene container
When the contents are filled and sealed in a container consisting of a paper container , the heat sealing surface can sufficiently withstand the peeling force exerted by the increase in the internal pressure of the sealed body, and has excellent sealing properties. An object of the present invention is to provide a heat-sealing lid material for a container for hermetically sealed packaging, which can be easily peeled off with an appropriate force when opened, and has both functions of sealing and easy peeling.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a polyethylene container for hermetically sealed packaging,
Polypropylene container, polystyrene container, or polyethylene
Thermal sealing of containers for hermetic packaging consisting of paper containers made of ren-coated
A lid material, on one side of a metal foil, partially saponified ethylene-vinyl acetate copolymer, and, of the acid-modified thereof,
Heat-sensitive adhesive resin 50 to 9 containing at least one as a main component
The gist of the present invention is a heat-sealing lid material for a container for hermetically sealed packaging provided with a heat-sensitive adhesive layer containing 8 parts by weight, 1 to 40 parts by weight of rosins, and 0.1 to 10 parts by weight of a higher fatty acid amide. I have.

As the above metal foil, aluminum foil is usually used, but other metal foils may be used. In the case of aluminum foil, its thickness is 5 to 100 μm, preferably 5 to 100 μm.
５０50 μm. When a so-called skirt portion (hem portion) is formed after or before sealing the lid material, the thickness of the aluminum foil is preferably 15 to 50 μm. In some cases, a polyester film or the like may be attached to one side to give the cover material its own strength.

[0008] When a metal foil is used as the base material of the heat sealing material, it has excellent barrier properties and can effectively preserve contents such as desserts and cooked foods for a long period of time.

[0009] Among the constituent components of the heat-sensitive adhesive layer, first, a partially saponified ethylene-vinyl acetate copolymer (hereinafter, referred to as a "substance")
HEVA) or (and) an acid-modified product thereof (hereinafter abbreviated as HEVA-C) will be described.

As the ethylene-vinyl acetate copolymer (EVA) used as a raw material for producing these components, one having a vinyl acetate content of 19 to 45% by weight is used.
More preferably, 25 to 40% by weight is used.
EVA having such a vinyl acetate content is produced by a known production method and usually has a melt index (g / g).
10 minutes, according to ASTM1238-65T, the same applies hereinafter)
Is from 10 to 800, preferably from 100 to 500.

The EVA raw material is then subjected to a saponification reaction to obtain a partially saponified EVA (HEV).
A) is obtained.

The saponification rate of EVA is usually 3 to 3
0 mol%, preferably 5 to 20 mol%. The saponification reaction may be performed by a conventionally known method, for example, in a system comprising a low-boiling alcohol such as methanol and ethanol and an alkali such as sodium hydroxide, potassium hydroxide and sodium methylate.

Next, an acid-modified product having a carboxyl group (HEVA-C) is obtained by using such a partially saponified ethylene-vinyl acetate copolymer (HEVA). As a method for acid-modifying HEVA, there are a method using a graft reaction and a method using an esterification reaction.

First, when utilizing a graft reaction, HE
The VA is reacted with an unsaturated carboxylic acid. Examples of such unsaturated carboxylic acids include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, and itaconic acid, and unsaturated dicarboxylic acids such as maleic acid (or anhydrides thereof). Usually, acrylic acid is used.

The grafting reaction may be performed under ordinary reaction conditions using a radical initiator such as benzoyl peroxide, lauroyl peroxide, α, α'-azobisisobutyronitrile, and the like.

The unsaturated carboxylic acid is used in an amount of 0.1 to 15% by weight, preferably 0.5 to 5% by weight, based on the weight of HEVA. The modified resin having a carboxyl group obtained by such a reaction generally has an acid value of 0.1 to
40, preferably 0.5 to 15.

When an esterification reaction is used, HEVA is reacted with a dicarboxylic anhydride under ordinary reaction conditions. Examples of such a dicarboxylic anhydride include maleic anhydride, succinic anhydride, phthalic anhydride, hexahydrophthalic anhydride and the like. The amount of the dicarboxylic anhydride used is 5 to 80 of the hydroxyl groups in HEVA and its acid-modified product (HEVA-C).
Mol%, preferably 10 to 50 mol%. The modified resin having a carboxyl group obtained by such an esterification reaction generally has an acid value of 0.1 to 20, preferably 0.5 to 15.

The partially saponified ethylene-vinyl acetate copolymer (HEVA) and its acid-modified product (HEVA-
C) is used alone or in combination of two or more. These HEVA) and HEVA-C
Among them, HEVA-C is particularly preferably used.

In general, rosins are thermoplastic resins containing abietic acid as a main component, such as gum rosin, wood rosin and tall oil rosin.

The rosins used in the present invention include hydrogenated rosin (dihydroabietic acid, tetrahydroabietic acid), disproportionated rosin, disproportionated hydrogenated rosin, and polymerized rosin (including partially polymerized rosin) in addition to the above. ), Modified rosins, rosins or alkyl esters of modified rosins,
Glycol esters, glycerin esters, pentaerythritol esters and the like can be mentioned.

The above-mentioned rosins are used alone or in combination of two or more.

The higher fatty acid amide includes, for example, those having 10 to 50 carbon atoms such as stearamide, palmitic amide, oleic amide, erucamide, lauric amide, methylenebisstearamide, and ethylenebisstearamide. There are things.

The higher fatty acid amides may be used as a mixture of two or more kinds.

A wax can be used in combination with the above higher fatty acid amide.

As the wax, for example, microcrystalline wax, paraffin wax (140
{F, 145 ° F, 150 ° F, 155 ° F), montan wax, carnauba wax, oxidized polyethylene wax, montan wax derivatives, sorbitol stearate, oxidized microwax, synthetic oxidized wax, caster wax, beeswax, wood wax, etc. Use

It is desirable to use a wax having a melting point of 60 ° C. or higher. This is because low-melting wax causes stickiness after film formation. If the melting point of the wax is 60 ° C. or higher, the surface of the fin material does not become sticky even in summer.

In addition, in order to prevent so-called blocking, a thermoplastic resin other than the above resins may be blended with the heat-sensitive adhesive resin in some cases.

Examples of such a thermoplastic resin include polyethylene, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / acrylic acid ester copolymer, and ionomer, and ionomer is particularly preferably used. .

The amount of these thermoplastic resins added is determined by the
It is necessary to have less than 50% by weight of the amount of A or (and) HEVA-C.

In the heat-sensitive adhesive, an appropriate amount of a tackifier such as a terpene resin or a petroleum resin (aliphatic, aromatic or alicyclic) may be used.

In the above, a heat-sensitive adhesive layer containing a higher fatty acid amide is provided on one side of the metal foil.
The heat-sensitive adhesive layer is made of HEVA or (and) HEVA-
50 to 98 parts by weight, preferably 60 to 97 parts by weight, of a heat-sensitive adhesive resin containing C as a main component, 1 to 40 parts by weight, preferably 3 to 38 parts by weight of rosins, and 0.1 to 10 parts by weight of higher fatty acid amide. Parts by weight, and preferably 0.3 to 10 parts by weight.

Here, HEVA and / or HEV
When AC exceeds 98 parts by weight and rosin is less than 1 part by weight, the amount of the rosin is too small and the container is filled with the content and sealed. It is not preferable because it cannot withstand the peeling force exerted by the increase in internal pressure.

Conversely, HEVA or (and) HE
When VA-C is less than 50 parts by weight and rosin exceeds 40 parts by weight, the amount of the rosin is too large, so that the blocking of the heat-sensitive adhesive becomes severe, which is not preferable.

On the other hand, when the content of the higher fatty acid amide is less than 1 part by weight, the amount of the higher fatty acid amide is too small, and there is no blocking prevention effect, which is not preferable.

Conversely, when the content of higher fatty acid amide is 1
When the amount exceeds 0 parts by weight, the higher fatty acid amide does not originally have adhesiveness, so that the original adhesiveness of the heat-sensitive adhesive layer is reduced, or the higher fatty acid amide is not bonded to the heat-sensitive adhesive layer via the higher fatty acid amide coating layer. It is not preferable because the adhesive strength with the container for hermetic packaging is reduced.

If necessary, an intermediate resin layer may be interposed between the heat-sensitive adhesive layer and the metal foil. This is because plastic containers may have poor thermal adhesion due to the molding method, and polyethylene-coated paper cups, etc., when molded from paperboard into cups, have a large step at the joint. In such a case, an intermediate resin layer such as a polyethylene layer is preferably provided as a cushion layer.

The intermediate resin layer needs to have good adhesion to the heat-sensitive adhesive layer. For example, an ethylene copolymer resin such as polyethylene or ethylene-vinyl acetate copolymer resin is used. The thickness of the intermediate resin layer is 10 to 50 μm for the purpose of overcoming unevenness and steps of the heat-sensitive adhesive layer.
It is preferable to set the degree. With such an intermediate resin layer, the cushioning property at the time of heat sealing is improved,
Corrosion of the metal foil due to contents such as dressing and mustard can be prevented.

Further, the other surface of the metal foil is usually subjected to necessary printing, and an anticorrosion coat layer is further provided on the surface.

The cover member made of the metal foil and the heat-sensitive adhesive layer is continuously punched and formed into a shape and a size covering the mouth of the container.

[0040]

In the above, when the container is filled with the contents and the container is hermetically sealed with the heat sealing material of the present invention, the heat sealing surface can sufficiently withstand the peeling force exerted by the increase in the internal pressure of the sealed body, and is excellent. It has good sealing properties, and can be easily peeled off with an appropriate force when opened, and has both functions of sealing properties and easy peeling.

FIGS. 1 and 2 show a specific example of a lid material according to the present invention.

First, the lid material shown in FIG.
On one side of (1), a heat-sensitive adhesive layer containing higher fatty acid amide
(2) is provided through an adhesive layer (3), containers made of polyethylene-coated paper or polyethylene containers, polyps
The higher fatty acid amide is present on the surface to be thermally bonded to the mouth part (10) of a hermetically sealed container made of a propylene container or a polystyrene container . Aluminum foil (1)
On the other side, an anticorrosion coat layer (4) is provided.

The lid shown in FIG. 2 has substantially the same structure as the lid shown in FIG.
In order to prevent corrosion of the aluminum foil (1), an intermediate resin layer (5) made of, for example, a polyethylene film is provided on one side of the aluminum foil (1), and the intermediate resin layer (5) has a heat-sensitive adhesive layer (2) containing a higher fatty acid amide. Is applied without using an adhesive layer by a gravure coat or the like.
On the other side of (1), an anticorrosion coat layer (4) is provided.

[0044]

Next, examples of the present invention will be described together with comparative examples.

Examples 1-3 Referring to FIG. 2, an anchor coat layer of a titanium coupling agent was provided on the other surface of a 35 μm thick aluminum foil (1) having an anticorrosion coat layer (4) on one surface. Thereafter, an intermediate resin layer (5) made of polyethylene is extruded to form an intermediate resin layer (5).
It was laminated to a thickness of μm. Further, a heat-sensitive adhesive layer (2) obtained by mixing various amounts of rosins and higher fatty acid amides with a heat-sensitive adhesive resin is further coated with a gravure coat to obtain a solid content of 4 g.
/ M ² to produce three types of heat-sealing lids.

Here, as the heat-sensitive adhesive resin, in Examples 1 and 2, an ethylene-vinyl acetate copolymer having a vinyl acetate content of 28% [Evaflex EV-250 (manufactured by Mitsui Dupont Polychemical Co., Ltd.)] was used. A mixture prepared by uniformly dispersing and mixing 5% by weight of calcium carbonate having an average particle size of about 1 μm in a 10% toluene solution of a 10% partially saponified product was used.

In Example 3, the vinyl acetate content was 28%.
% Ethylene-vinyl acetate copolymer [Evaflex E
V-250 (manufactured by Mitsui Dupont Polychemical Co., Ltd.)]
5% by weight of calcium carbonate having an average particle size of about 1 μm was uniformly dispersed and mixed in a 10% toluene solution of a modified product obtained by graft-polymerizing 1% of acrylic acid to 10% of a partially saponified product. .

In each case, rosins are K
R-610 (manufactured by Arakawa Chemical Industry Co., Ltd.) was used as the higher fatty acid amide in Examples 1 and 2 using stearic acid amide, and in Example 3, stearic acid amide and paraffin wax were used in combination.

The various lid materials thus obtained were punched into a predetermined shape and size corresponding to the mouth (10) of the container made of polyethylene coated paper by a punch press.

Then, these lids were fitted to the mouth (1) of a polyethylene-coated paper filled with jam at 80 ° C.
On 0), sealing was performed under the conditions of 210 ° C. and 0.8 seconds.

Then, in order to evaluate the sealing property and the peeling property of the sealed packaging container after the heat sealing as described above, the number of leaks (for 100 containers of the same type) ) And the peel strength (seal strength) of the lid material (average value when 10 containers of the same type were opened, kg / 15 mm width) were measured, and are shown in Table 1 below.

Comparative Examples 1 to 3 For comparison, a heat-sensitive adhesive made of a partially saponified ethylene-vinyl acetate copolymer (HEVA) on one side of an aluminum foil (1) as in Examples 1 and 2 above. A lid material provided with a heat-sensitive adhesive layer (2) containing resin as a main component and containing rosin but not stearamide (Comparative Example 1)
And a partially saponified ethylene-vinyl acetate copolymer (H
A lid material (Comparative Example 2) provided with a heat-sensitive adhesive layer (2) containing a heat-sensitive adhesive resin (EVA) as a main component and containing stearamide but not containing rosin, and an aluminum foil (1) Having a heat-sensitive adhesive resin made of an ethylene-vinyl acetate copolymer (EVA) that is not partially saponified as a main component and a heat-sensitive adhesive layer (2) containing rosins and stearamide on one side of the cover. A material (Comparative Example 3) was prepared, and the number of leaks in the sealed packaging container after heat sealing and the peel strength (kg
/ 15 mm width), and are shown in Table 1 below. In Comparative Example 1, the blocking of the heat-sensitive adhesive layer (2) was severe, and the winding and rewinding operations after coating were difficult, and the sealing and peeling properties of the lid material were not evaluated.

[0053]

[Table 1] As is clear from the above table, according to the lid material of the present invention,
Since the higher fatty acid amide is contained in the heat-sensitive adhesive layer (2) to be heat-bonded to the mouth (10) of the container, when filling and sealing the contents of the container, the internal pressure of the sealed body is applied to the heat-sealing surface. It can sufficiently withstand the peeling force exerted by the rise, and the number of leakage occurrences per 100 containers after the sealed packaging is zero.
And had excellent sealing properties. And when you open it,
The peel strength of the lid material was 1.0 to 1.3 kg / 15 mm width, and it could be easily peeled off with an appropriate force, and had both functions of sealing and easy peeling.

On the other hand, in the lid material of Comparative Example 2 provided with the heat-sensitive adhesive layer (2) containing stearamide but not rosin, the peel strength of the lid material was 1.1 kg / 15.
mm width, good peelability, but container 10 after sealed packaging
There were as many as 10 leaks per 0, and the sealing performance was poor.

In the lid material of Comparative Example 3 in which the heat-sensitive adhesive layer is mainly composed of a heat-sensitive adhesive resin composed of an ethylene-vinyl acetate copolymer (EVA) which is not partially saponified,
Even though the rosins and stearamide were contained in the heat-sensitive adhesive layer at the same ratio as in Example 1, there were 23 leaks per 100 containers after hermetically sealed packaging, and the sealing property was extremely poor. In addition, the peel strength of the lid material was 1.6 kg / 15 mm width, and the peelability was also poor.

[0056]

EFFECTS OF THE INVENTION The inventions, as described above, for a sealed package
Polyethylene container, polypropylene container, polystyrene
Container or polyethylene-coated paper container
A heat-sealing material for a hermetically sealed container, wherein a heat- sensitive adhesive resin containing, as a main component, at least one of a partially saponified ethylene-vinyl acetate copolymer and an acid-modified product thereof on one surface of a metal foil. 50-98 parts by weight and rosins 1-4
A heat-sensitive adhesive layer containing 0 parts by weight and 0.1 to 10 parts by weight of a higher fatty acid amide is provided. According to the lid material of the present invention, the contents are filled and sealed in a container. , Which can withstand the peeling force acting on the heat sealing surface due to the rise of the internal pressure of the sealed body, has excellent sealing properties, and can be easily peeled off with a moderate force when opening, It has the function of both sex and easy-peeling, which is very convenient.

[Brief description of the drawings]

FIG. 1 is a partially enlarged sectional view showing a specific example of a heat sealing material according to the present invention.

FIG. 2 is a partially enlarged sectional view showing another specific example of the heat sealing material according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 aluminum foil (metal foil) 2 heat-sensitive adhesive layer 3 adhesive layer 4 anticorrosion coat layer 5 intermediate resin layer

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Satoshi Yakura 6, 224 Kaiyama-cho, Sakai City Examiner, Showa Aluminum Co., Ltd. Kenichi Kamono (56) Reference JP-A-3-96339 (JP, A) JP Hei 3-34848 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 15/08 B32B 7/12 B32B 27/28 102

Claims (3)

(57) [Claims] 1. A polyethylene container and a polyp for hermetically sealed packaging.
Lopylene container, polystyrene container, or polyethylene
・ Heat-sealing lids for hermetically sealed containers consisting of coated paper containers
Wherein, on one side of the metal foil (1), partially saponified ethylene-vinyl acetate copolymer, and acid-modified thereof,
Heat-sensitive adhesive resin 50 to 9 containing at least one as a main component
A heat-sensitive adhesive layer containing 8 parts by weight, 1 to 40 parts by weight of rosins, and 0.1 to 10 parts by weight of a higher fatty acid amide (2)
A heat-sealing lid material for a container for hermetically sealed packaging provided with: 2. An intermediate resin layer (5) is provided between one side of a metal foil (1) and a heat-sensitive adhesive layer (2), and the intermediate resin layer (5) is mainly composed of polyethylene or a copolymer thereof. The heat-sealing lid material for a container for hermetically sealed packaging according to claim 1, which is made of a film having the following characteristics. 3. The metal foil (1) is an aluminum foil having a thickness of 5 to 100 μm, and a film mainly composed of polyethylene or a copolymer thereof constituting the intermediate resin layer (5) is
A heat-sensitive adhesive layer having a thickness of 10 to 50 μm
The heat-sealing lid material for a container for hermetically sealed packaging according to claim ² , wherein (2) has a thickness of 1 to 10 g / m2.