JP2000177080A - Easy opening container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide sufficient sealing force as a packaging container or bag having a propylene resin on a heat-sealing surface, easy to open at a time of opening and also excellent in the appearance of a peel surface. SOLUTION: The ethylenic resin layer of a laminated film consisting of a layer of a resin compsn, which comprises a polymer of a modified olefinic resin obtained by subjecting 40-70 wt.% of an olefinic resin and 60-30 wt.% of a vinyl monomer to a graft reaction condition and an unmodified olefinic resin and/or a vihyl monomer compounded if necessary and contains 30-60 wt.% of the vinyl monomer in total, and a layer of an ethylenic resin is heat- sealed to the surface of an ethylenic resin to obtain an easy opening container having heat-sealed structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging container or a packaging bag having an ethylene-based resin on a heat-sealing surface, which has sufficient sealing force, is easy to open at the time of opening, and has an appearance of a peeling surface. Also relates to an easily openable container.

[0002]

2. Description of the Related Art Conventionally, seal pack packaging, in which a resin container body is heat-sealed with a resin film-like lid material and packaged, has been widely used mainly for packaging foods and beverages such as dairy products, confectionery, fruit juice drinks and the like. And occupy an important position together with plastic packaging bags. Conventionally, solution-type adhesives and hot-melt-type adhesives have been used as these sealants, but these are not always easy to open because the sealant causes a ductile fracture at the time of opening to form a thread. However, there was a problem of lack of easy-opening properties such as poor appearance of the peeled surface, and a lack of sealing properties such as peeling at high temperatures due to insufficient heat resistance. .

[0003] In order to improve such problems, various sealants having both sealing properties and easy-opening properties have been proposed in recent years.
Used. For example, there is a composition in which a tackifier is blended with an ethylene-vinyl acetate copolymer, and a modified olefin resin obtained by modifying the olefin resin with an aromatic vinyl monomer proposed by the present applicant. (See Japanese Patent Publication No. 1-42967). However, these sealants are also used as a packaging container or a packaging bag in a condition where internal pressure is applied, such as filling the contents and performing a heat treatment on a boil or the like. There is a problem that the contents spout out during processing.

On the other hand, in order to have easy-opening property and to solve insufficient sealing force, a sealing layer made of an ethylene-based resin is used.
A method using a laminated film comprising a cohesive failure layer of a mixture of an ethylene-based resin and a propylene-based resin as a sealant (for example, see JP-A-10-264330), or a polypropylene resin sealing layer and a polypropylene resin. A method using a laminated film composed of a mixture of a propylene-ethylene copolymer resin and a polyethylene resin, and a cohesive failure layer of a mixture of a polypropylene resin and a propylene-ethylene copolymer resin as a sealant (for example, JP-A-3-288642) Etc.) are proposed. However, according to the study of the present inventors, in a packaging container or a packaging bag having an ethylene-based resin on the heat sealing surface, the sealant composed of the laminated film has a problem that the appearance of the peeled surface is not good. Turned out to be.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art in an easily-openable container. Therefore, the present invention provides a packaging container having an ethylene-based resin on a heat-sealing surface. Alternatively, it is an object of the present invention to provide an easily-openable container which has a sufficient sealing force, is easily opened at the time of opening, and is excellent in appearance of a peeled surface as a packaging bag or the like.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present invention and the like have found that a laminated film having a layer of a resin composition containing a modified olefin resin having a specific composition is used. It has been found that the above object can be achieved, and the present invention has been completed. That is, the present invention provides an olefin resin of 40 to 70% by weight and a vinyl monomer of 60 to 3%.
A modified olefin-based resin obtained by subjecting 0% by weight to a graft reaction condition and a polymer of an unmodified olefin-based resin and / or a vinyl monomer blended as required; The ethylene-based resin layer of the laminated film of the layer of the resin composition having a total content of the polymer of 30 to 60% by weight and the layer of the ethylene-based resin, and the surface of the ethylene-based resin,
The gist of the present invention is an easily-openable container having a heat-sealed structure which is heat-sealed.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the olefin resin used for the modified olefin resin constituting the resin composition of the resin composition layer in the laminated film includes, for example, ethylene, propylene, 1-butene and the like. Carbon number 2
About 8 to about 8 α-olefin homopolymers,
Olefin, ethylene, propylene, 1-butene, 3
-Methyl-1-butene, 1-pentene, 4-methyl-1
-Pentene, 4,4-dimethyl-1-pentene, 1-hexene, 4-methyl-1-hexene, 1-heptene, 1
-Other α-olefins having about 2 to 18 carbon atoms such as octene, 1-decene, and 1-octadecene; vinyl acetate;
Copolymers with (meth) acrylic acid, (meth) acrylic acid esters, and the like, and the like. Specifically, for example, ethylene single polymer such as low-, medium-, or high-density polyethylene (branched or linear) Coalesce, ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-4-methyl-1-
Pentene copolymer, ethylene-1-hexene copolymer,
Ethylene-1-octene copolymer, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer,
Ethylene-based resins such as ethylene-ethyl (meth) acrylate copolymer, propylene-based resins such as propylene homopolymer, propylene-ethylene copolymer, propylene-ethylene-1-butene copolymer, and 1-butene Examples thereof include homopolymers, 1-butene-ethylene copolymers, and 1-butene-based resins such as 1-butene-propylene copolymers.
In the present invention, two or more of these olefin resins may be used in combination.

[0008] Among the above olefin resins, in the present invention, ethylene resins are preferable, and ethylene homopolymer or ethylene-1-butene copolymer is particularly preferable.

The vinyl monomer used in the modified olefin resin includes, for example, styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene,
-Aromatic vinyl compounds such as methylstyrene, dimethylstyrene, chlorostyrene, etc .; vinyl esters such as vinyl acetate and vinyl propionate; methyl acrylate, ethyl acrylate, i-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, hexyl acrylate Acrylate esters such as 2-ethylhexyl acrylate, octyl acrylate and dodecyl acrylate, methacrylate esters such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate and glycidyl methacrylate; Acrylic acid, methacrylic acid, maleic anhydride, dimethyl maleate, di (2-ethylhexyl) maleate Unsaturated carboxylic acids or derivatives thereof, acrylonitrile, unsaturated nitriles such as methacrylonitrile, vinyl chloride, unsaturated mono- or dihalides such as vinylidene chloride, etc., among which aromatic vinyl compounds are preferred. Among them, styrene is preferred.
In the present invention, two or more of these vinyl monomers may be used in combination.

In the present invention, the modified olefin resin constituting the resin composition of the resin composition layer in the laminated film comprises 40 to 70% by weight, preferably 45 to 65% by weight of the olefin resin and the vinyl olefin resin. Dimer 60-30
%, Preferably 55 to 35% by weight, obtained by subjecting to graft reaction conditions. If the vinyl monomer content is less than this range, the sealing force of the resin composition layer of the laminated film is too strong to open. On the other hand, if it exceeds this range, the homogeneity of the resin composition layer will be impaired and the resin composition layer cannot be put to practical use.

In the present invention, the conditions for the graft reaction are basically as follows:
A method such as electron beam irradiation or addition of a radical generator under aqueous suspension or the like can be employed, but in the present invention, an aqueous suspension method with addition of a radical generator is preferable.

Specifically, the aqueous suspension method with the addition of a radical generator is preferably an oil-soluble radical generator having a decomposition temperature of 50 ° C. or higher. If the decomposition temperature is lower than 50 ° C., the polymerization of the vinyl monomer proceeds abnormally, and it tends to be difficult to obtain a homogeneous modified resin. Here, the decomposition temperature is a temperature at which 50% of the radical generator is decomposed when 0.1 mol of the radical generator is added to 1 liter of benzene and left for 10 hours.

In the present invention, examples of the radical generator include di-t-butyl peroxide, dicumyl peroxide, t-butylbenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide and octanoyl. Peroxide, benzoyl peroxide, o-methylbenzoyl peroxide, 2,4
-Dichlorobenzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxypivalate, t-butylperoxybenzoate,
Di-tert-butyl-diperoxyphthalate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane,
Organic peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; and azo compounds such as azobisisobutyronitrile and azobis (2,4-dimethylvaleronitrile). In the present invention, two or more of these radical generators may be used in combination.

The amount of the radical generator is 0.01 to 10 parts by weight per 100 parts by weight of the vinyl monomer.
When the amount is less than this range, the reaction does not proceed smoothly. When the amount is more than this range, a gel tends to be easily generated in the modified resin.

The preferred aqueous suspension grafting conditions in the present invention include an aqueous suspension containing the olefin resin, the vinyl monomer, and a predetermined amount of the radical generator, and the decomposition of the radical generator. This is a method in which the temperature is raised to a temperature that does not substantially occur to impregnate the vinyl monomer into the olefin resin, and then the temperature is further raised to complete the graft reaction.

Here, the aqueous suspension is prepared by adding a vinyl monomer in which a radical generator is dissolved to an aqueous suspension of an olefin resin and stirring the mixture, or stirring the vinyl monomer in which the radical generator is dissolved. It is preferably prepared by any method of adding an olefin resin to an aqueous suspension of a body and stirring the mixture.

The content of the olefin resin and the vinyl monomer in the aqueous suspension is about 5 to 100 parts by weight with respect to 100 parts by weight of water. For example, polyvinyl alcohol, methylcellulose, water-soluble polymers such as hydroxycellulose, anionic surfactants such as alkylbenzene sulfonate, nonionic surfactants such as polyoxyethylene alkyl ether, or magnesium oxide, calcium phosphate and the like It is preferable to use a suspension stabilizer such as a water-insoluble inorganic salt, alone or in combination, in an amount of about 0.001 to 10% by weight based on water.

The olefin resin is impregnated with the vinyl monomer under stirring, generally at room temperature to 100 ° C., preferably at room temperature.
The reaction is carried out at 0 to 90 ° C. until the free vinyl monomer becomes 80% by weight or less of the total amount of the vinyl monomer, usually in about 2 to 8 hours. Since the olefin resin is relatively compatible with the vinyl monomer, even if such a vinyl monomer is released before the start of the reaction, the vinyl monomer is impregnated into the olefin resin during the reaction. Thus, a homogeneous modified resin can be obtained.

The grafting reaction is generally carried out under stirring with 5
This is performed at a temperature of about 0 to 150 ° C. and a normal pressure of about 10 kg / cm ^{2 for} about ² to 10 hours, but the temperature and pressure during that time need not be constant. The olefin-based resin used for the reaction is used in the form of powder and granules, and is preferably in the form of particles having an average particle size of 1 to 8 mm, particularly 3 to 7 mm.

The modified olefin resin obtained by the above method is usually a mixture of an olefin resin grafted with a vinyl monomer and a polymer of a vinyl monomer. As the resin composition constituting the resin composition layer of the above, a vinyl monomer is added to the total amount of an unmodified olefin resin and / or a polymer of a vinyl monomer to be blended if necessary. It is essential that the total content of the polymer is 30 to 60% by weight, and the total content is preferably 35 to 55% by weight. If the total content of the polymer of the vinyl monomer is less than this range, the sealing force of the resin composition layer of the laminated film is too strong to make the opening difficult. The property is impaired and cannot be put to practical use.

Therefore, as the resin composition constituting the resin composition layer of the laminated film in the present invention, when the content of the vinyl monomer polymer in the modified olefin resin satisfies this range, The modified olefin-based resin can be used as it is, but even if the range is satisfied, if the sealing property or the opening property is adjusted according to the application, or if the range is not satisfied, A resin composition is obtained by blending a polymer of an unmodified olefin resin and / or a vinyl monomer with the modified olefin resin.

As the unmodified olefin resin at that time, the olefin resins mentioned in the above-mentioned modified olefin resin, for example, preferably, ethylene homopolymer,
Ethylene-1-butene copolymer and the like, and as the vinyl monomer polymer, the vinyl monomer polymer mentioned in the modified olefin resin, for example, preferably, a polystyrene resin, High impact polystyrene resin and the like can be mentioned. It is preferable to blend the same olefin resin as used for the modification and the same vinyl monomer polymer as used for the modification.

In the present invention, the resin composition constituting the resin composition layer of the laminated film includes the modified olefin resin, the unmodified olefin resin and / or the polymer of the vinyl monomer. In addition, as long as the effects of the present invention are not impaired, other thermoplastic resins and rubbers, and antioxidants, light stabilizers, antistatic agents, antiblocking agents,
Additives such as lubricants, plasticizers and pigments, fillers and the like may be blended. These compounds may be added in advance to the olefin resin to be modified, added to an unmodified olefin resin or a vinyl monomer polymer, or added during the production of the resin composition, or modified. During the production of the olefin-based resin, for example, a method of adding it to a styrene monomer together with a radical generator may be used.

In the present invention, the ethylene resin constituting the ethylene resin layer in the laminated film may be the same as the ethylene resin mentioned in the modified olefin resin constituting the resin composition layer. Can be

The laminated film of the present invention comprises a layer of the resin composition and a layer of the ethylene-based resin,
The lamination method is not particularly limited, but it is preferable to perform co-extrusion of both layers using a known T die or annular die.

Practically, various thermoplastic resins such as polyamide resin, polyester resin, saponified ethylene-vinyl acetate copolymer, polyolefin resin, polycarbonate resin, polystyrene resin, acrylic resin, etc. As a laminated film obtained by extrusion lamination on a substrate such as a film, aluminum foil, paper or the like, or as a co-extruded film with the above-mentioned various thermoplastic resins. The “film” in the present invention includes not only ordinary films but also sheets.

The thickness of the resin composition layer of the laminated film of the present invention is preferably about 5 to 100 μm, and the thickness of the ethylene resin layer is preferably about 1 to 50 μm.
Further, the thickness ratio of the resin composition layer to the ethylene-based resin layer is 2 or more from the viewpoint of easy opening at the time of opening as an easily-openable container, particularly from the viewpoint of not causing a film residue of the ethylene-based resin layer at the time of opening. Is preferable, and it is especially preferable that it is 2.5 or more.

The easy-open container of the present invention has a heat-sealing structure in which the ethylene-based resin layer of the laminated film and the ethylene-based resin surface are heat-sealed. The ethylene-based resin surface as the heat-sealed body of the film is a single-layer or laminated state as long as the same ethylene-based resin as that mentioned in the laminated film forms the heat-sealed body surface. Either is fine.

In the present invention, the specific form of the easily-openable container is, for example, (1) a packaging container comprising a container body and a lid material, and (a) a case where a laminated film is used on the lid material side. (B) an easy-open container comprising: a container body having an ethylene-based resin on a heat-sealing surface; and a lid having a laminated film having the ethylene-based resin layer as a heat-sealing surface.
When the laminated film is used on the container body side, the laminated film is easily formed of a container body having the ethylene resin layer as a heat sealing surface and a lid member having the ethylene resin on the heat sealing surface. Openable container, (2) as packaging bag,
(A) when the laminated film is used on both sides of the bag,
An easy-open container that is a heat-sealed bag body with the ethylene-based resin layers facing each other and having the laminated film as a heat-sealing surface, and (b) using the laminated film on one surface of the bag,
In the case where a bag member having an ethylene-based resin on the heat-sealing surface on the other surface is used, the bag is a bag in which the ethylene-based resin layer of the laminated film and the ethylene-based resin surface are heat-sealed. Containers and the like.

[0030]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. The modified olefin resins used in Examples and Comparative Examples are shown below.

Production Example A of Modified Olefin-Based Resin A 50-liter autoclave was charged with 20 kg of water.
As a suspending agent, 0.4 kg of tricalcium phosphate and 0.6 g of sodium dodecylbenzenesulfonate were added as an aqueous medium, and a branched ethylene homopolymer resin having an average particle size of 3 to 4 mm (density 0.917 g / cm ³ , 190
° C, melt flow rate 45 g / at 2.16 kg load
10 minutes) 7 kg of particles were added and stirred to form an aqueous suspension. 3,5,5 as a radical generator
18.2 g of 5-trimethylhexanoyl peroxide
Then, 7 kg of styrene monomer in which 10.5 g of benzoyl peroxide was dissolved was added, and nitrogen was introduced into the autoclave to pressurize the system to 0.5 kg / cm ^{2. Then} , the temperature in the autoclave was raised to 55 ° C. The mixture was stirred at a temperature for 5 hours to impregnate the entire amount of the styrene monomer containing the radical generator into the ethylene homopolymer resin particles. Subsequently, the inside of the autoclave was heated to 65 ° C.
The mixture was stirred for an hour to perform a graft reaction, and the temperature was further raised to 110 ° C., and the mixture was stirred for 3.5 hours at this temperature to complete the reaction.
After cooling, the reaction solid was taken out and washed with water to obtain 14 kg of a particulate modified ethylene homopolymer resin. The resulting modified resin (modified olefin resin A) contained 50% by weight of polystyrene and had a melt flow rate of 2.5 g / 10 minutes under the same conditions.

Production Example B The amount of the branched ethylene homopolymer resin particles was 8.4 kg,
A modified ethylene homopolymer resin was obtained in the same manner as in Production Example A, except that the amount of the styrene monomer was changed to 5.6 kg. Obtained modified resin (referred to as modified olefin resin B)
Contained 40% by weight of polystyrene and had a melt flow rate of 6.0 g / 10 minutes under the same conditions as above.

Production Example C The amount of the branched ethylene homopolymer resin particles was 4.9 kg,
A modified ethylene homopolymer resin was obtained in the same manner as in Production Example A except that the amount of the styrene monomer was changed to 9.1 kg. Obtained modified resin (modified olefin resin C)
Contained 65% by weight of polystyrene.

Examples 1 to 5 and Comparative Examples 1 to 4 A modified olefin resin and the same branched ethylene homopolymer resin and / or polystyrene resin as those used for the modification (200 ° C., 5 kg load) Melt flow rate 1
6 g / 10 min) was dry-blended at the ratio shown in Table 1 and then melt-kneaded at 200 ° C. using a single-screw extruder having a diameter of 40 mm to prepare a resin composition. The same branched ethylene homopolymer resin as used for the quality
Each was fed to a co-extrusion film forming machine having a diameter of 35 mm equipped with a T die, and co-extruded at 230 ° C. to form a laminated film having a thickness shown in Table 1 consisting of a resin composition layer and an ethylene homopolymer resin layer. After being molded and subjected to a corona discharge treatment on the surface of the laminated film on the side of the resin composition layer, a 15 μm-thick polyamide resin film as a substrate was adhered via a dry laminating adhesive to produce a composite film.

On the other hand, the above-mentioned composite film is used as a cover material on the flange portion of a rectangular container body produced by thermoforming from a sheet of branched ethylene homopolymer resin, and the ethylene homopolymer resin layer is bonded to the adhesive surface. To prepare an easily-openable container. The obtained easily-openable container was evaluated for heat sealing performance by the following method, and the results are shown in Table 1.

Peel strength Using a hot plate type heat sealer, at a temperature of 160 ° C. and 180 ° C.
At 200 ° C., pressure 2 kg / cm ² , time 1 second,
The lid material is thermocompression-bonded to the container body flange at a width of 5 mm, the bonded portion is sampled at a length of 15 mm, and peeled at 23 ° C. at a pulling speed of 300 mm / min in the bonding width direction using an Instron type tensile tester. Then, the 180 degree peel strength was measured.

Opening Property The presence or absence of a film residue on the peeled surface of the test piece after measuring the peel strength was visually observed.

Examples 6 to 8, Comparative Examples 5 to 6 In the same manner as in Examples 1 to 3 and Comparative Examples 1 and 2, a composite film prepared by laminating a molded laminated film and a polyamide resin film was used. The ethylene homopolymer resin layer was opposed to each other to prepare an easily-openable container as a heat-sealed bag, and the easily-openable container of the obtained bag was heat-sealed in the same manner as described above. The performance was evaluated, and the results are shown in Table 1.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

According to the present invention, as a packaging container or a packaging bag having an ethylene-based resin on the heat sealing surface, it has a sufficient sealing force, can be easily opened at the time of opening, and has an appearance of a peeling surface. It is also possible to provide an easily-openable container that is also excellent.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 51/06 C08L 51/06 (72) Inventor Yoshinobu Yada 1 Tohocho, Yokkaichi-shi, Mie Mitsubishi Chemical Corporation F-term (reference) at Yokkaichi office of the company BA02 BA25 DA01 EH20 EH202 EJ55 EJ552 GB17 JL14 YY00A 4J002 BB032 BB052 BC033 BN051 BN061 BN071 BN081 GG01

Claims (8)

[Claims] 1. A modified olefin resin obtained by subjecting 40 to 70% by weight of an olefin resin and 60 to 30% by weight of a vinyl monomer to a graft reaction condition and an unmodified olefin resin blended as required. A polymer of a resin and / or a vinyl monomer, wherein the total content of the polymer of the vinyl monomer is 3
The ethylene-based resin layer of the laminated film of the resin composition layer and the ethylene-based resin layer having 0 to 60% by weight and the ethylene-based resin surface have a heat-sealed structure in which the surface is heat-sealed. An easily openable container characterized by the following. 2. A graft reaction condition of a modified olefin resin constituting the resin composition of the resin composition layer in the laminated film is such that an aqueous suspension containing an olefin resin, a vinyl monomer, and a radical generator is used. A step of raising the temperature to a temperature at which decomposition of the radical generator does not substantially occur to impregnate the vinyl monomer into the olefin resin, and then further raising the temperature to complete the graft reaction. 3. The easily-openable container according to 1.). 3. The easy-open container according to claim 1, wherein the olefin resin of the modified olefin resin constituting the resin composition of the resin composition layer in the laminated film is an ethylene resin. 4. The easy-open package according to claim 1, wherein the vinyl monomer of the modified olefin resin constituting the resin composition of the resin composition layer in the laminated film is an aromatic vinyl compound. Sex container. 5. The laminated film according to claim 1, wherein the thickness ratio of the resin composition layer to the ethylene resin layer is 2 or more.
5. The easy-open container according to any one of items 1 to 4. 6. The easy-open container comprises a container body having an ethylene-based resin on a heat-sealing surface, and a lid having a laminated film having the ethylene-based resin layer as a heat-sealing surface. 5. The easily-openable container according to any one of 5. 7. An easily-openable container having a laminated film, a container body having an ethylene-based resin layer as a heat-sealing surface,
The easy-open container according to any one of claims 1 to 5, comprising a lid material having an ethylene-based resin on a heat sealing surface. 8. The easy-to-open container according to claim 1, wherein the easily-openable container is a bag which is heat-sealed with its ethylene-based resin layers having a laminated film as a heat-sealing surface facing each other. Openable container.