JP4108577B2 - Resin composition for sealant, sealant film and use thereof - Google Patents

Description

  The present invention relates to a resin composition for sealant, a sealant film having both heat sealability and easy peel property, and further relates to a laminate film and a container using the sealant film.

  With the recent diversification of food, various packaging materials have been proposed. Among these, containers having easy peel properties are widely used as instant noodles, yogurt containers, confectionery containers, and other food containers. The sealant film having an easy peel property is required to satisfy the conflicting performances of the sealing property and the easy peel property at the same time. Furthermore, development of sealant films having various heat seal strengths is desired due to diversification of food containers. For example, when packaging foods that are sensitive to heat, it is necessary to heat seal at a relatively low temperature to protect the contents. For such applications, there is a demand for a sealant film that can exhibit strong seal strength even when heat-sealed at a low temperature and that exhibits easy peel properties. For example, in the case of a lid for a paper cup container coated with a polyethylene film, a relatively low sealing strength is required to prevent the paper cup from peeling off.

  On the other hand, from the standpoints of preventing contamination of the contents and the appearance of the product, there is a demand not to leave a peeling trace (thread drawing) when the seal surface is peeled off, but to prevent the yarn drawing phenomenon itself from occurring.

Japanese Patent Application Laid-Open No. 10-337829 discloses an easy-open film formed from low-density polyethylene and polybutene-1. However, the sealant film obtained by this publication has a problem that the sealing strength when sealed at a low temperature is insufficient. (Patent Document 1)
Japanese Patent Application Laid-Open No. 2002-146343 discloses an easy-open film having improved stringiness and made of low-density polyethylene and polybutene-1. However, the sealant film obtained by this publication has a high sealing strength and an insufficient easy peel property. (Patent Document 2)
Japanese Patent Application Laid-Open No. 11-58642 discloses an easy-open film having improved stringiness and made of low-density polyethylene, polybutene-1 and ethylene-α-olefin copolymer rubber. However, in the method according to the publication, the sealing strength is high, the easy peel property is insufficient, and the usable applications are limited. (Patent Document 3)
Japanese Patent Laid-Open No. 10-337829 JP 2002-146343 A Japanese Patent Laid-Open No. 11-58642

  The present invention has an excellent balance between heat seal strength and easy peel properties, and in particular, a sealant resin composition capable of obtaining a sealant film having a wide optimum seal temperature and no occurrence of stringing, and is obtained from the composition. An object is to provide a sealant film, and a laminate film and a container using the same.

That is, the present invention provides a melt flow rate (MFR, ASTM D1238, 190 ° C.,
2.16 kg load) is 1-50 (g / 10 min), and density (ASTM D1505) is 0.9.
00~0.940 (g / cm ³⁾ in and, and melt tension (MT) and the melt flow rate (MFR) of the following equation ^{40 × (MFR) -0.67 ≦ MT} ≦ 250 × (MFR) -0.67
High-pressure polyethylene (A) satisfying 15 to 55 % by weight,
Graft-modified ethylene / α- olefin (carbon number 3 to 10) copolymer (B) 3 to 50 % by weight, and melt flow rate (MFR, ASTM D1238, 190 ° C., 2.16 kg load) is 0.01 to 10 (G / 10 min), density (ASTM D1505) is 0.880 to 0.92.
5 (g / cm ³ ) butene polymer (1-butene content: 60 to 100 (mol%)) (C)
20 to 60 weight%
The resin composition for sealants formed from this.

  Furthermore, the present invention relates to a sealant film comprising the resin composition of the present invention, and to a laminate and a container formed from the sealant film.

  The resin composition for sealant of the present invention has a good balance between heat-sealability and easy-peel property and the film obtained therefrom can achieve a lower sealing strength without causing stringing. It can be suitably used for a container.

The present invention relates to a resin composition composed of an ethylene polymer, a graft-modified ethylene polymer, and a butene polymer, and a sealant film, a laminate film, and a container using the composition. Next, each of those configurations will be specifically described.

Ethylene polymer (A)
The ethylene polymer (A) in the resin composition of the present invention has a melt flow rate (hereinafter abbreviated as MFR) measured at 190 ° C. and a load of 2.16 kg according to ASTM D1238, preferably 1 to 50, preferably 3 40 (g / 10 min), the density (ASTMD 1505) is 0.900 to 0.940, preferably 0.900 to 0.930 (g / cm ³ ), and the melt tension (MT) and the melt flow Rate (MFR) is the following relational expression 40 × (MFR) ^−0.67 ≦ MT ≦ 250 × (MFR) ^−0.67
The ethylene polymer (A) that satisfies the above is satisfied. Here, both MT and MFR are values measured at 190 ° C. Melt tension (MT) is a value calculated | required by measuring the stress when extending the melted ethylene-type polymer at a fixed speed. Specifically, it is a value measured using a Toyo Seiki MT measuring machine under conditions of a resin temperature of 190 ° C., an extrusion speed of 15 mm / min, a winding speed of 15 m / min, a nozzle diameter of 2.09 mmφ, and a nozzle length of 8 mm. .

  When MFR is in the above range and MT is in the range of the above relational expression, the melt tension of the ethylene polymer is increased and the moldability is improved.

  The ethylene-based polymer (A) used in the composition of the present invention may be a so-called high-pressure polyethylene produced under high pressure using a radical catalyst, or a Ziegler catalyst as long as the physical properties are satisfied. Alternatively, it may be a so-called medium-low pressure polyethylene produced using a metallocene catalyst in the presence of a comonomer such as ethylene and an α-olefin at a medium pressure. In the high pressure polyethylene, long chain branching is present in the molecular chain, which exhibits high melt tension, and therefore can be preferably used in the present invention.

The ethylene polymer (A) used in the composition of the present invention is a copolymer of ethylene and a small amount of an unsaturated carboxylic acid such as vinyl acetate as long as the properties as a sealant film in the present invention are not impaired. It may be.

Graft-modified olefin polymer (B)
The graft-modified olefin copolymer used as the component (B) in the resin composition of the present invention is a modified product obtained by graft-modifying the olefin polymer (B-1) with a vinyl compound having a polar group. Examples of the olefin polymer (B-1) include a propylene (co) polymer, a butene (co) polymer, and an ethylene (co) polymer. Among these, a random copolymer obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms, is preferable. The molecular structure may be linear or branched having long or short side chains. Specific examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene and 1-dodecene, preferably 1- Butene, 1-hexene and 1-octene. The α-olefin content in the copolymer is 5 to 50 mol%, usually 7 to 30 mol%.

The MFR (ASTM D1238, 190 ° C., 2.16 kg load) of the olefin polymer (B-1) is 0.5 to 50, preferably 1 to 45, more preferably 2 to 40 (g / 10 min). The density (ASTMD 1505) is less than 0.960 (g / cm ³ ), preferably 0.850 to 0.930 (g / cm ³ ). More preferable examples of the olefin polymer (B-1) include a density of 0.850 to 0.900 (g / cm ³ ) and a melting point of less than 90 ° C. determined by differential scanning calorimetry (DSC). Alternatively, it is a random copolymer obtained by copolymerizing amorphous ethylene having no melting point and α-olefin having 3 to 10 carbon atoms.
The method for producing the ethylene / α-olefin random copolymer is not particularly limited, but can be produced by copolymerizing ethylene and α-olefin in the presence of a Ziegler-Natta catalyst or a metallocene catalyst. .

 Furthermore, in this invention, it can also be used by the composition which blended several types of ethylene * alpha-olefin random polymers from which density and / or MFR differ.

  The graft-modified olefin polymer (B) used in the present invention is obtained by graft-modifying the olefin polymer (B-1) with a vinyl compound having a polar group. Examples of the vinyl compound having a polar group include vinyl compounds having a polar group containing oxygen such as acid, acid anhydride, ester, alcohol, epoxy and ether, and vinyl compounds having a polar group containing nitrogen such as isocyanate and amide. And vinyl compounds having a polar group containing silicon, such as vinyl silane.

  Among these, a vinyl compound having a polar group containing oxygen is preferable, and an unsaturated epoxy monomer, an unsaturated carboxylic acid, and a derivative thereof are preferable.

  Examples of the unsaturated epoxy monomer include unsaturated glycidyl ether and unsaturated glycidyl ester (for example, glycidyl methacrylate).

Examples of unsaturated carboxylic acids include acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid and nadic acid ^TM (endocis-bicyclo [2,2,1] hept- 5-ene 2,3-dicarboxylic acid) and the like.

  Examples of the unsaturated carboxylic acid derivatives include acid halides, amide compounds, imide compounds, acid anhydrides, and ester compounds of the above unsaturated carboxylic acids. Specific examples include maleyl chloride, maleimide, maleic anhydride, citraconic anhydride, monomethyl maleate, dimethyl maleate, and glycidyl maleate.

Among these, unsaturated carboxylic acids or acid anhydrides thereof are preferable, and maleic acid, nadic acid ^TM or acid anhydrides thereof are particularly preferable.

The graft-modified olefin polymer (B) can be produced by a conventionally known method, for example, the following method.
A method in which the olefin polymer (B-1) is melted with an extruder or the like, and an unsaturated carboxylic acid or the like is added to perform graft modification.
A method of graft-modifying by dissolving the olefin polymer (B-1) in a solvent and adding an unsaturated carboxylic acid or the like.

  In any method, it is preferable to perform the grafting reaction in the presence of a radical initiator in order to graft the unsaturated carboxylic acid and the like efficiently.

  As the radical initiator, organic peroxides, azo compounds and the like are used. Specifically, benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3, 2,5-dimethyl Examples include organic peroxides such as -2,5-di (tert-butylperoxy) hexane and 1,4-bis (tert-butylperoxyisopropyl) benzene, and azo compounds such as azobisisobutylnitrile and dimethylazoisobutyrate. .

  These radical initiators are usually 0.001 to 1 part by weight, preferably 0.003 to 0.5 part by weight, and more preferably 0.05 to 100 parts by weight of the olefin polymer (B-1). Add 0.3 parts by weight.

  The reaction temperature at the time of carrying out the graft reaction in the presence or absence of the radical initiator as described above is usually set in the range of 60 to 350 ° C, preferably 150 to 300 ° C.

  The graft position of the unsaturated carboxylic acid or derivative thereof grafted to the olefin polymer (B-1) is not limited, and the graft position is not limited to any carbon atom of the olefin polymer constituting the graft-modified olefin polymer. Saturated carboxylic acid or its derivative should just be couple | bonded.

  The graft modification amount is 0.01 to 20% by weight, preferably 0.05 to 10% by weight, and more preferably 0.1 to 7% by weight.

Butene polymer (C)
The butene polymer (B) used in the resin composition of the present invention is a 1-butene homopolymer, or an α having 2 to 20, preferably 2 to 10, carbon atoms excluding 1-butene and 1-butene. -Copolymers with olefins. Specific examples of the α-olefin include ethylene, propylene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene and 1-dodecene, preferably ethylene and propylene. The 1-butene content in the butene polymer is 60 to 100, preferably 70 to 100 (mol%).

  The density of the butene polymer is 0.880 to 0.925, preferably 0.885 to 0.920 (g / cm3). When in this density range, the adhesiveness is small, and therefore, when a container is produced from the film, the film is less likely to adhere to an apparatus such as a roll, and the contents can be filled at a high filling speed.

  Moreover, MFR (190 degreeC) exists in the range of 0.01-10, Preferably it is 0.05-8, More preferably, it is the range of 0.1-7 (g / 10min). Within this range, the film can be molded at a high molding speed without applying an excessive load to the motor of the molding machine.

Such a butene polymer is disclosed in JP-B-64-7088, JP-A-59-206415, JP-A-59-206416, JP-A-4-218508, and JP-A-4-218607. And a polymerization method using a stereoregular catalyst described in JP-A-8-225605 and the like. The butene polymer used in the present invention may be one type or a combination of two or more types.

Resin Composition The resin composition of the present invention comprises an ethylene polymer (A), a graft-modified olefin polymer (B), and a butene polymer (C). 60, preferably 15-55% by weight, (B) 1-60, preferably 3-50% by weight, and (C) 10-70, preferably 20-60% by weight. Here, the total amount of (A), (B) and (C) is 100% by weight. When the ratio of each component is within this range, the film obtained from the composition is excellent in the balance between the sealing strength and the easy peel property, and a practically suitable easy-open container is obtained.

  A characteristic of the resin composition of the present invention is that a graft-modified olefin polymer having a specific property is used as a constituent component of the resin composition. By using such a graft-modified olefin polymer, a film having an excellent balance between seal strength and easy peel property can be obtained even at a low sealing temperature. Furthermore, even if the sealing strength is lower than that of the conventional case, there is no occurrence of stringing and a good easy peel property is exhibited. In addition, since the optimum sealing temperature can be controlled by the amount of the graft-modified olefin polymer, it can be applied to an easy-open container having various characteristics.

  In the present invention, additives such as an antioxidant, a heat stabilizer, a weather stabilizer, a slip agent, an antiblocking agent, a crystal nucleating agent, etc., as necessary, as long as the performance as the resin composition of the present invention is not impaired. May be included.

In addition, after blending each of the above components and, if necessary, various additives with a mixer such as a Henschel mixer, a Banbury mixer, a tumbler mixer, etc., the film formation described later as a pellet using a uniaxial or biaxial extruder However, it can also be used in a film forming machine in a state where the above components are blended.

Sealant Film By forming a film from the resin composition of the present invention, a sealant film for a packaging material that requires easy peelability can be produced. The film may be formed by a cast forming method or an inflation forming method, and a film having a good uniform film thickness can be produced usually under a resin temperature of 180 to 240 ° C. The thickness of the film is usually 3 to 100 μm, preferably 5 to 80 μm.

Laminate Film The sealant film can be used alone, but is generally used as a packaging film or a packaging sheet in the configuration of a laminate film laminated on a base film.

  Although it does not specifically limit as a base film, Polyolefin films, such as polyethylene and a polypropylene, Styrenic resin films, Polyester films, such as a polyethylene terephthalate and a polybutylene terephthalate, Nylon 6 or nylon 6,6 Polyamide films, or stretched films of these, laminated films of polyolefin films and resin films with gas barrier properties such as polyamide films and ethylene-vinyl alcohol copolymer films, metal foils such as aluminum, aluminum or silica A vapor-deposited film, paper, or the like on which vapor is deposited is appropriately selected and used depending on the purpose of use of the packaging material. This base film can be used not only in one type but also in combination of two or more types.

  Since the sealant film layer is located in at least one outermost layer of the laminate film, in the production thereof, the resin composition of the present invention is directly extruded and laminated on the base film, or the base film and the sealant film are combined. A dry lamination method or a method of co-extruding resins constituting both layers can be employed.

   As one embodiment of a laminated body film, the structure of a sealant film layer / polyolefin film layer / other film layers can be mentioned. Here, as another film layer, a layer selected from the group consisting of the aforementioned polystyrene film, polyester film, polyamide film, laminated film of polyolefin film and gas barrier resin film, aluminum foil, vapor deposition film, and paper is used. Can be mentioned.

  When the polyolefin layer and the other film layer cannot be bonded with sufficient adhesive strength, a structure of sealant film layer / polyolefin film layer / adhesive layer / other film layer can be employed. As an adhesive layer, an anchor coat agent such as urethane or isocyanate adhesive, or a modified polyolefin such as unsaturated carboxylic acid grafted polyolefin can be used as an adhesive resin to firmly bond adjacent layers. it can.

Container The sealant film layers of the laminate film described above face each other, or the sealant film layer of the laminate film and another film face each other, and then, at least one of the surroundings so as to have a desired container shape from the outer surface side. A container can be manufactured by heat-sealing the part. Moreover, the sealed bag-shaped container can be manufactured by heat-sealing the entire periphery. When this bag-shaped container molding process is combined with the contents filling process, that is, the bottom and sides of the bag-shaped container are heat sealed, then the contents are filled, and then the top is heat sealed to produce a package. can do. Therefore, this laminate film can be used in an automatic packaging apparatus for solids such as snacks, powders, or liquid materials.

  Also, a laminate film or sheet, or a container in which another film or sheet is previously formed into a cup shape by vacuum forming or pressure forming, a container obtained by injection molding or the like, or a container formed from a paper substrate, etc. Then, the container with the contents packaged is obtained by covering the container with the laminate film of the present invention as a lid and then heat-sealing the upper part or the side part of the container. This container is suitably used for packaging instant noodles, miso, jelly, pudding, snacks and the like.

EXAMPLES Next, although an Example demonstrates this invention, this invention is not limited to this.
[Example 1]

Using an extrusion lamination apparatus with a die width of 500 mm that also has an extruder with a screw system of 65 mmφ, the sealant resin composition described below is applied to the LDPE layer side of the laminate having a layer structure of PET / LDPE (12 μm / 30 μm). A film having a layer structure of PET / LDPE / sealant (12 μm / 30 μm / 20 μm) was prepared by extrusion lamination so that the sealant thickness was 20 μm under the conditions of a resin temperature of 260 ° C. and a take-off speed of 80 m / min. The resulting film was evaluated for heat seal strength, easy peel property and stringiness by the following methods. The results are shown in Table 1.
Sealant resin composition: High-pressure polyethylene (0.917 g / cm ³ , MFR (190 ° C.) 7.2 g / 10 min, MT 28 mN) 30% by weight, maleic anhydride graft-modified ethylene / 1-butene copolymer (MEBR) -1, density 0.896 g / cm ³ , MFR (190 ° C.) 11 g / 10 min, 1-butene content 11 mol%, melting point 82 ° C., maleic anhydride graft modification amount 0.75 wt%) 30 wt%, and A composition comprising 40% by weight of 1-butene polymer (PB-1, density 0.907 g / cm ³ , MFR (190 ° C.) 0.2 g / 10 min, 1-butene 100 mol%) as a butene polymer component. .

(1) Heat seal strength: Two 15 mm strip-shaped test pieces were prepared, the seal layers were faced to each other, and heat seal was performed at a predetermined temperature, a pressure of 0.2 MPa, and a seal time of 1.0 seconds. . Thereafter, the layers were peeled in the direction of 180 ° at a speed of 300 mm / min, the peel strength at that time was measured, and the value was defined as the heat seal strength (N / 15 mm).
(2) Easy peel property: After the heat seal strength measurement, the film sample was observed, and the case where the film was not stretched or cut was marked with ◯. On the other hand, the case where the film was stretched or cut was marked with x.
(3) Thread pullability: The seal surface of the film sample after the heat seal strength measurement was observed, and the case where the resin adhered to the seal surface and its periphery was evaluated as x, and the case where the thread resin was not observed was evaluated as ◯. .

[Example 2, Comparative Example 1]

The film was prepared in the same manner as in Example 1 except that the high-pressure polyethylene, the maleic anhydride graft-modified ethylene / 1-butene copolymer and the 1-butene polymer used as the sealant layer were changed to the resin composition shown in Table 1. Evaluation was performed. The results are shown in Table 1.

As is clear from the results shown in Table 1, the film of the present invention was excellent in the balance between heat sealability and easy peel properties, and had good stringiness even in a lower seal strength region than before.

The resin composition for sealant of the present invention has a good balance between heat-sealability and easy-peel property and the film obtained therefrom can achieve a lower sealing strength without causing stringing. It can be suitably used for a container.

Claims (6)

Melt flow rate (MFR, ASTM D1238, 190 ° C., 2.16 kg load)
Is 1 to 50 (g / 10 min), and the density (ASTM D1505) is 0.900 to 0.940 (
g / cm ³ ) and the melt tension (MT) and the melt flow rate (MFR) are expressed by the following relational expression 40 × (MFR) ^−0.67 ≦ MT ≦ 250 × (MFR) ^−0.67
High-pressure polyethylene (A) satisfying 15 to 55 % by weight,
Graft-modified ethylene / α- olefin (carbon number 3 to 10) copolymer (B) 3 to 50 % by weight, and melt flow rate (MFR, ASTM D1238, 190 ° C., 2.16 kg load) is 0.01 to 10 (G / 10 min), density (ASTM D1505) is 0.880 to 0.92.
5 (g / cm ³ ) butene polymer (1-butene content: 60 to 100 (mol%)) (C)
20 to 60 weight%
The resin composition for sealants formed from. A sealant film comprising the resin composition according to claim 1 and having a thickness of 3 to 100 µm. It is selected from the group consisting of a layer of the sealant film according to claim 2 , a polyolefin film, a polystyrene film, a polyester film, a polyamide film, a laminated film of a polyolefin and a gas barrier resin film, an aluminum foil, paper, and a vapor deposition film. A laminate comprising the at least one film layer. A layer of the sealant film according to claim 2 , a polyolefin film layer, a polyolefin film, a polystyrene film, a polyester film, a polyamide film, a laminated film of a polyolefin and a gas barrier resin film, an aluminum foil, paper, and a vapor deposition film A laminate film, wherein at least one film layer selected from the group consisting of is laminated in this order. The container characterized by aligning the sealant film layer surfaces of the laminate film according to claim 3 or 4 and heat-sealing at least a part thereof. The sealant film layer of the laminate film according to claim 3 or 4 and a molded product of a resin selected from the group consisting of polyethylene, ethylene / vinyl acetate copolymer, and polypropylene, at least a part of which is a heat A container characterized by being sealed.