JPS581672A - Thermally sealed package which is easily unsealed - 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 an easy-to-open heat-sealed package, and more specifically, the present invention relates to an easy-to-open heat-sealed package, and more particularly, it has an excellent combination of sealing reliability and easy-to-open properties, and also reduces feathering that occurs when the lid is peeled and opened. The present invention relates to an easy-to-open, heat-sealed package that improves the appearance of the unsealed part due to (stringing) forces.

Conventionally, containers consist of a container body made of thermoplastic glass such as polypropylene, and a lid with a heat-sealing resin layer on a base material such as metal.

BACKGROUND ART Packaging bodies in which heat sealing is performed between the polypropylene surface of the container body and the heat sealable resin layer of the lid body are widely used in fields such as food packaging.

This heat-sealing resin layer is not only capable of forming a heat-sealed structure with excellent sealing reliability by simply heat-sealing the polypropylene surface WK. It must be strong enough to

For this purpose, the heat-sealable resin layer is based on polypropylene and is blended with a resin or rubber that does not exhibit fusion properties to polypropylene, or even if it does, the degree of fusion is low. Ru. However, in such blends, polypropylene is blended with different resin components that are difficult to mix with each other, resulting in a non-uniformly dispersed structure. There is a problem in that fluffing or stringing, which is generally called linting, occurs, resulting in a poor appearance at the peeled-open portion. This 7 easring is also thought to be caused by the aforementioned dispersion structure resin being fibrillated by the tension during peeling.

The inventors of the present invention have investigated the problem of phasing caused by peeling of the heat-sealed part [2]. First, we learned that the higher the adhesive strength of the heat-sealable resin layer to the base material, the less likely it is that feathering will occur, and then based on this knowledge, we developed a system with a relatively high melt index. A certain crystalline propylene resin and polyethylene are tarlened in a certain ratio, and this blend is thinly coated on a base material via an acid or acid anhydride-modified propylene resin layer, and feathering can be effectively eliminated. It has been found that heat-sealed packages can be easily obtained.

That is, according to the present invention, the container body is made of polypropylene, and the lid body is provided with a heat-sealable resin layer on the base material, and the polypropylene surface of the container body and the heat-sealable resin layer of the lid body are made of polypropylene. The heat-sealable resin layer is made of a crystalline propylene resin having a melt index of 5 to 100 and a polyethylene having a melt index of 2 to 50 in a 50:50 ratio.
It consists of a layer with a thickness of 5 to 25 microns of a resin blend containing a weight ratio of 95:5 to 95:5, and the physical properties of this resin blend are controlled through a layer of modified propylene resin modified with an acid or an acid anhydride. An easily openable heat-sealed package is provided, which is bonded to the base material.

The invention will be described in detail below with reference to the accompanying drawings.

In FIG. 1 showing a heat-sealed package of the present invention, this package includes a container body 1 made of polypropylene,
The lid 2 is made up of a base material 6 and a heat-sealable resin layer 5 applied to the base via an adhesive network layer 4. The container main body 1 has a heat-sealable part 6 such as a flange, and is arranged so that the polyglobulin surface of the heat-sealable part 6 and the heat-sealable resin layer 5 of the lid are in contact with each other,
Heat sealing is performed between the two by pressure heating.

An important feature of the present invention is that this heat-sealable resin layer 5
Melt index (ASTM D-1258, 117
10 minutes) is 5 to 100, especially 15 to 50, and the melt index is 2 to 50.
In particular, 3 to 15 polyethylene, 50:50 to 9
5:5,! A resin blend containing 55:45 to 80:20 by weight is used, and this blend is applied through a modified propylene resin layer 4 modified with an acid or an acid anhydride to a thickness of 55:45 to 80:20. A thin layer of 7 to 20 microns was provided on 41 to 25 microns.

In the present invention, the use of a blend of propylene resin and polyethylene each having a melt index within the above-mentioned high range has a dual effect in preventing feathering when opening the package. That is, the melt index of these resins is related to the molecular weight of the resin, and it is possible to suppress the strength of the entire heat-sealable resin layer to a relatively low range. In addition, by selecting a combination of resins with a high melt index, melt moldability is improved and extrusion coating becomes possible. It can be made into a thin layer, thereby making it possible to suppress the strength of the entire heat-sealable resin layer to a lower range.

In the present invention, the heat-sealing resin layer is in the thin range described above.
! The fact that the
If the layer of the blend is cast as a thick layer, e.g. 60 microns or more, not only will ethering occur upon opening, but also the inhomogeneous dispersion structure mentioned above will result in easuring within the layer. This causes the inconvenience of rupturing and leaving a thin film stuck to the mouth of the container after the rupture.

The use of the crystalline propylene resin and polyethylene in the blend ratio described above has an important meaning in terms of achieving seal reliability and ease of opening. In other words, if the blending ratio of polyethylene is less than the above range, the heat sealing strength at the heat sealing part tends to be too high, making it difficult to open, while on the other hand, the blending ratio of polyethylene is higher than the above range. In some cases, the heat sealing strength becomes too low and there is a tendency for the dark blue part to break due to accidental external force.
The reliability of the film is reduced, and the film forming properties of the blend are also deteriorated. According to the present invention, by setting the blending ratio of both resins within the above range, it is possible to adjust the heat seal strength to a range called easy-open sealing, that is, a range of α5 to 3.0 kg/l and 5 m. Become.

Furthermore, in order to prevent 7 athering due to peeling at the heat-sealed part, it is extremely useful to thermally bond the above-mentioned resin blend to the gas barrier substrate via an acid or acid anhydride-modified propylene resin. is important. That is, when a crystalline propylene resin/polyethylene blend is extrusion coated onto a substrate via a conventional isocyanate-based or organic titanate-based anchoring agent, even when the above-mentioned conditions are satisfied, After all, it is unavoidable that fading occurs when opening the package. According to the present invention, when an extruded resin blend is extrusion coated onto a substrate via an acid or acid anhydride-modified propylene resin layer, the resin blend adheres closely to the substrate due to K. The occurrence of phase rings is prevented.

In the easy-to-open heat-sealable package of the present invention, as described above, the heat-sealable resin layer has a weakened structure by selecting the melt index and by blending polyethylene, and has a weakened heat-sealing resin layer. The sealing resin layer is provided with a considerably thinner thickness than conventional ones.

Furthermore, this weakened heat-sealable resin layer is extremely firmly bonded to the base material via the modified propylene resin layer. When peeling is performed by tension between the heat-sealed lid and the container body 7 lunge, the container body 7 will inevitably be peeled off.
Peeling occurs in the vicinity of the lunges, and the heat-sealing resin layer easily breaks at the edge of the 7-tsunge, preventing feathering and film tearing.

In the present invention, the crystalline (
In addition to polypropylene, crystalline propylene-ethylene copolymers may also be used. As the polyethylene, any of low density, medium density, and high density polyethylene can be used. From the viewpoint of extrusion coatability, particularly melt tension, it is desirable to use low density polyethylene having a density of 0.9559/CC or less.

The heat-sealing blend of the present invention may contain a third resin component to improve its compatibility. Examples of such a fifth resin component include ethylene-vinyl acetate copolymer, ethylene-7-acrylate copolymer, crystalline ethylene-propylene copolymer, and crystalline ethylene-propylene-propylene copolymer. Combination, ethylene-propylene-
Rubber, ethylene-propylene-nonconjugated diene-rubber, and ionic framework olefin copolymer (ionomer) may be used alone or in combination of two or more.

The fifth resin component of cholera is preferably used in an amount of 5 to 60 parts by weight per 100 parts by weight of polypropyref.

The base material can be metal foil such as aluminum foil, tin foil, steel foil, or tin foil, thermoplastic resin film such as biaxially stretched polyethylene terephthalate film, two-wheel stretched nylon film, or polycarbonate film, various papers, or even 22 of these. Nate et al. In the case of a transparent lid, the above-mentioned nylon or polyester film base material is used, while in the case of a lid that strictly requires gas parrying properties, Arun foil, or aluminum foil and film or paper are used. A laminate with is used as the base material.

Modified propylene resins include crystalline polypropylene and crystalline propylene-ethylene copolymer core polymers.
K, an ethylenically unsaturated carboxylic acid or a graft-modified acid anhydride thereof is used. Suitable examples of acids and acid anhydrides to be used are as follows.

4 Ethylenically unsaturated carboxylic acids Niacrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, 5-norbornene-2,5-dicarboxylic acid.

B, ethylenically unsaturated carboxylic anhydride: maleic anhydride, citraconic anhydride, itaconic anhydride, 5-norbornene-2,5-dicarboxylic anhydride, tetrahydrophthalic anhydride.

These ethylenically unsaturated carboxylic acids or their anhydrides have a syl group in the carboxyl group of 57'rj! n.

Milliquivalent (IQ)/100.9 Polymer, % [
It may be incorporated into the backbone polymer at a concentration of 10 to 300 (IB-example)/100 JF polymer.

Various methods can be used to apply Km-based propylene resin to the base material.
For example, a method of applying in the form of a solution or dispersion, a method of applying in the form of a powder or film, a method of extrusion coating in the form of a melt, etc. are employed. Generally speaking, the thickness of the modified propylene resin layer is preferably in the range of 1 to 50 μm, particularly 3 to 20 μm.

The above-mentioned blend is extrusion coated onto the substrate coated with this modified probile/based resin. The above-mentioned resins may be mixed by tri-blend and the mixture may be directly supplied to a film-forming extruder, or the resin may be kneaded in advance with a pelletizer, mixer, etc. and then supplied at the time of extrusion. Of course, these resin compositions may contain one or more additives known per se, such as lubricants, antioxidants, anti-blocking agents, fillers, tackifiers, and impact modifiers. It can be blended according to known formulations.

Extrusion can be carried out by means known per se, except that the thickness of the final heat-sealable resin layer is within the range specified in the present invention. In order to make the thickness of the coating layer as thin as possible, the feeding speed of the base material was increased (compared to the extrusion speed of the resin blend from the die lip) so that the extruded resin film could be sufficiently compressed and stretched. A blend of polyethylene, especially low-density polyethylene within the above range, is excellent in such drop-down properties.

Thermal bonding of the blend physics to the base material may be done at the same time as extrusion coating, but in general, the laminate after extrusion coating is heated to melt the modified propylene resin layer and the blend physics to completely thermally bond them. Good.

It should be appreciated that instead of separately coating the modified propylene resin layer and the blend physics, both layers can be coextruded through multiple dies and the coextrudate coated onto the substrate.

As the container body, various molded containers are used in which the constituent material is polypropylene and the heat-sealed portion is made of polypropylene. Of course, the container may be a blow molded container or an injection molded container made of polypropylene alone, or a draw molded container made from a film, sheet, etc. by pressure forming, plug assist molding, or vacuum forming. Similar containers formed from other plastics, paper, lanates (such as Manazuru etc.) may be used.

The heat sealing operation can be performed using a heat sealing means known per se such as a heat sealer, high frequency induction heating, and the like.

The package according to the present invention is not only capable of forming a heat-sealed part that is easy to heat-seal, has excellent sealing reliability, and can be heat-sterilized, but also can be easily opened by peeling, and the peeled part can be easily removed. It has the great advantage of being opened without leaving any feathering.

The invention is illustrated by the following example.

The example was applied to the aluminum side surface of a laminate in which a biaxially stretched polyethylene terephthalate film with a thickness of 12μ and an aluminum foil with a thickness of 50μ were adhered by urethane adhesive cutting.
Isotactic polypropylene grafted with maleic anhydride, the average carboxyl group concentration is 2o town v/1
00.9 polymer.

A first extruder having a screw with a diameter of 50 mφ was used to produce modified polypropylene (melting point: 165°C, Ml: 409/10m1ntr), melting point: 154°C, density: 0.9
011/ct1% Ml is 2511/10wLcn.

Ethylene-propylene with a s mol content of 60% by weight of a random copolymer and a low-density polyethylene with a melting point of 109°C and a density of 0.9151/x-MI of 12#/10 pairs/ A dry blend of 40 wt. was heated to a width of 65 mm using a v.2 extruder with a screw of 65 tmφ in diameter at a resin temperature of 230° C.
The modified polypropylene is co-extruded from a coat hanger type two-layer Tm die at the position where it is in contact with the aluminum foil, and is temporarily bonded by pressing with a chill roll with a diameter of 400fiφ and a silicone roll with a diameter of 20()+mφ. Gluing was done. Next, this temporarily bonded laminate was thermocompressed using a heat treatment roll with a diameter of 400 nφ maintained at a temperature of 200°C and a silicone roll with a diameter of 200 wφ, and then a chill roll with a diameter of 400 nφ and a silicone roll with a diameter of 2
By cooling with a 00111φ silicone roll, the structure is changed to 12μ biaxially oriented polyethylene terephthalate layer, 150μ aluminium foil, 15μ modified polypropylene layer/
A laminate having a 10μ ethylene-propylene copolymer blend layer was obtained.

Next, a circular lid member having a diameter of 75 mm and a tab was punched out from this laminate.

Next, a laminated sheet 'IJ≧' having a layer structure of melipropylene/linoic anhydride-modified polypropylene/ethylene-vinyl alcohol copolymer/maleic anhydride polyglopylene//polypropylene is formed, and 7 to 1 loIs is formed.
Coffee jelly was filled into a cup having a flange and having a diameter of 75 mm, and the sealing lid was heat-sealed to the open bottom flap/jet portion. This filled and sealed cup was subjected to retorting at 105° C. for 60 minutes.

As a result of this retort sterilization, no damage to the seal portion was observed, and the sealing performance was perfect. Further, when the seal lid was opened from the tab part, it was easy to open and no 7 ether ring was observed on the peeled surface of the flange part. When the seal strength of the seal lid was separately calculated, it was 1210. It was an f/15 scratch.

Furthermore, a test piece with a width t5α was cut out from the seal lid material, and was heat-sealed to a polypropylene laminated sheet under various temperature conditions at a constant pressure of 2/x” and a constant time of 2 seconds to determine the seal strength (T-peel). The second result of taking care of
Shown in #A. It is clear from the figure that 5. Wide temperature range 1! I
It was possible to peel off from the seal interface over K, and the sole strength was also maintained at a low value. After sterilization in a retort at 120°C for 30 minutes, there was no significant difference in seal strength before and after the retort.

Example 2゜A laminate of a biaxially stretched polyethylene terephthalate film with a thickness of 12μ and an aluminum foil with a thickness of 30μ is bonded using a urethane adhesive. The average concentration of carboxyl groups grafted with maleic acid is 25
m#q/100g polymer, melting point 162°C, Ml 90
11/10 min of modified polypropylene powder was applied by electrostatic coating method and fixed on the aluminum surface by high frequency induction heating. Next, the melting point is 154°C, the density is 0.90jj 7cm", and the Ml is 259/
10 rnin, 65 molar ethylene-propylene random copolymer with 5 molar ethylene content, melting point 109°C, density 0.915. ! J/ci2. Ml
20m1 of low density polyethylene with 12.9/10mja
% and melting point is 104℃, density is 0.927 #/10
mtn, Mlb-99/10711&F&, a tri-blend of ethylene-vinyl acetate copolymer with a vinyl acetate content of 10 wt. Then, melt extrusion coating was applied to the modified polypropylene powder coated surface of the laminate, and temporary adhesion was performed by pressing with a chill roll having a diameter of 400 mm and a silicone roll having a diameter of 20011 mm. Next, this temporarily bonded laminate was thermocompressed using a heat treatment roll with a diameter of 400 mm and a silicone roll with a diameter of 2001 mm, both of which were kept at a temperature of 200°C.
By cooling with a silicone roll of 11 straight and 200 mφ, a laminate with a structure of 12 μ two-wheel stretched polyethylene tele 7 tarley) It / 30 μ aluminum foil 72 μ modified polypropylene layer / 15 μ ethylene propylene copolymer ternary blend layer was made. Obtained.

The laminated sheet thus obtained has a diameter of 7 mm with tabs.
A circular seal lid of 0 mφ is punched out, a cup with a diameter of 70 wφ having a flange at the opening formed from a laminated sheet of 70 μ polypropylene/100 μ aluminium foil is filled with orange jelly, and the seal is placed on the opening 7 langes. The lid was heat sealed. This filled and sealed cup was heated to 120℃.
, 50 minutes of retort sterilization was performed. After this Frut sterilization, no damage to the seal portion was observed, and the sealing performance was perfect. Also, when I opened the seal from the tab part of the lid,
Opening was easy, and no feathering was observed on the peeled surface of the flange. The seal strength of the seal lid was separately measured and found to be 15509/1.5 C1l.

Comparative Example 1゜Instead of coating the modified polypropylene powder on the aluminum foil surface in Example 2, a urethane-based anchoring agent was applied, and after drying, the same ethylene-propylene copolymer 6 as used in Example 2 was applied thereon. When the original blend is extrusion coated, the composition is 12μ biaxially oriented polyethylene terephthalate @/30μ aluminum foil 715
B A laminate of ethylene-propylene copolymer ternary blend layers was obtained.

Using this laminate, a sealing lid similar to that in Example 2 was produced, and a similar aluminum molded cup was filled and sealed. When this seal lid was peeled off and opened, peeling occurred between the aluminum foil of the seal lid and the 6-component ethylene-propylene copolymer blend layer, and a film of ethylene-propylene copolymer remained on the flange of the aluminum molded cup. .

Comparative Example 2゜A film with a thickness of 70 μm was formed by the T-die method using the same pre-prepared ethylene-propylene copolymer as that used in Example 2, and the base material used in Example 2 and urethane were formed into a film with a thickness of 70μ. By laminating with a system adhesive, a laminate having a 12μ biaxially oriented polyethylene terephthalate layer/30μ aluminum foil/70μ ethylene p-filament 75 pre-prepared/pre-prepared layer was obtained.

Using this laminate, a sealing lid similar to that of Example 2 was made, and a similar aluminum (=ram) molded cup was filled and sealed, and when the sealing lid was peeled and opened, the 7th rank part of the aluminum molded cup was sealed. 21 The ring occurred.

Example 6゜Maleic anhydride is grafted onto isotactic polypropylene on the surface of a base material having a composition of 70μ paper/15μ maleic anhydride-modified polypropylene layer/9μ aluminum foil.The average carboxyl group concentration is 50mgq/10011.
50% by weight of modified polypropylene with a melting point of 164 DEG C. and an iI of 55 g71o=t* and a melting point of 156 DEG C. and a density of 0.9011/am".

Ml is 25.9/1 (llsis, engineering f and y & [amount is 4
% Roux ethylene-propylene random copolymer 50
A blended product with a melting point of 154 DEG C. and a density of 0.0 DEG C. was coated by extrusion from a first T-die with a width of 650 m using an extruder having a screw with a diameter of 65 W1.
901/cs'', Ml is 25I/1Q min, ethylene content is 65% by weight, melting point is 162℃, density is 0.9
5011/cm", Ml is si/1omin, medium density polyethylene 20 wt. and melting point is 109°C, density is 0.9159/cx", Ml is 12.9/10rIL.
A dry pre-coated product of i+s low density polyethylene of 15% by weight was extrusion coated through a second T-die having a width of 65*1 L using an extruder having a screw with a diameter of 65 .phi. Next, this temporarily bonded laminate was heat-treated in an open oven at a temperature of 200°C, and the diameter was reduced to 400 mm.
By cooling with a silicone roll with a diameter of 200℃ mφ, the composition becomes 70μ paper/15μ
A laminate of modified polypropylene layer 79μ aluminum foil/10μ modified polypropylene layer/10μ ethylene-propylene copolymer ternary blend layer was obtained.

A sealing lid was punched out from the thus obtained laminate, and after filling a cup made of a laminate of paper/aluminum foil/polypropylene layer with sake, the sealing lid was heat-sealed to the 72-inch portion of the container by high-frequency induction heating. . When this heat-sealed seal lid was opened from the tab part, the opening was only 7.
No needling was observed on the peeled surface of run 9. In addition, when the seal strength of the seal lid was measured, it was found to be 154.
It was 0g/15m.

[Brief explanation of the drawing]

Fig. f@1 is a sectional view showing the structure of a sealed container sealed with an easy-to-open seal lid, which is an example of the present invention, and Fig. 2 is a graph showing the relationship between seal strength and heat seal temperature for Example 1. This is a diagram showing the relationship, where numeral 1 on the side indicates the container body made of polypropylene, 2 indicates the lid, 6 indicates the base material, 4 indicates the adhesive layer, 5 indicates the heat-sealable resin layer, and 6 indicates the cover. The heat-sealed parts are shown. Patent applicant Akira Kishimoto ('C)

Claims (1)

[Scope of Claims] (1) Consisting of a container body made of polypropylene and a lid having a heat-sealable resin layer on a base material, the polypropylene surface of the container body and the heat-sealable resin of the lid. In a package in which the layers are sealed by heat sealing. The heat sealable resin layer has a melt index of 5 to 10.
Crystalline boopylene resin with a melt index of 0 and a melt index of 2
The resin blend 1118 consists of a layer of a resin blend having a thickness of 5 to 25 mm containing polyethylene and polyethylene in a weight ratio of 50:50 to 95:5, and this resin blend 1118 layer is a modified resin modified with an acid or an acid anhydride. An openable heat-sealed package characterized in that it is bonded to the base material via a propylene resin layer. (2) The package according to claim 1, wherein the polyethylene is low-density polyethylene with a density of 0.935 g/CO or less. (3) Crystalline propylene resin and polyethylene at 50%
The package according to claim 1, which is a resin blend containing the resin at a weight ratio of :50 to 95:5. (4) Claim 1, wherein the resin blend layer is applied by extrusion coating. ! The package described in J. (5) The resin blend layer contains 5 to 60 parts by weight of an ethylene-vinyl acetate copolymer, an ethylene-acrylate copolymer, a crystalline ethylene-propylene copolymer, and 5 to 60 parts by weight of a crystalline propylene resin IQO; crystalline ethylene
propylene-butene-1 copolymer, ethylene-propylene rubber, ethylene-propylene-nonconjugated diene rubber, or ionic framework olefin copolymer (iono, -
) The package according to claim 1, which contains: (6) A patent claim in which the modified propylene resin is a propylene resin modified with an ethylenically unsaturated carboxylic acid or its anhydride, containing carboxyl groups at a concentration of 5 to 600 electric equivalents/100 g polymer. The package according to item 1. (Force) The package according to claim I!!, wherein the modified propylene resin layer has a thickness of 1 to 50 microns. (8) The resin blend physical and modified propylene resin layer are formed by multilayer coextrusion. The package according to claim 1, wherein the package is coated on a base material.