JP4314146B2 - Resin composition for sealant and easy heat sealable sealant film obtained therefrom - Google Patents

Description

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

  With the recent diversification of food, various packaging materials have been proposed, and the development of sealant films having various heat seal strengths is desired. 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, a sealant film is required that exhibits strong sealing strength even when heat-sealed at low temperatures. Furthermore, a sealant film having a wide range of heat seal temperature possible temperature and capable of having both functions of easy peel and complete sealing by changing the heat seal temperature is also desired.

JP-A-61-106648 discloses a composition comprising a propylene random copolymer and a 1-butene system. (Patent Document 1)
Japanese Patent Application Laid-Open No. 2002-154188 discloses a laminate in which a composition comprising a propylene resin and a 1-butene copolymer is used as a sealant layer. These films have good low temperature heat sealability. Furthermore, the heat seal temperature range is wide, and it is possible to impart easy peel properties by controlling the seal temperature, which is particularly suitable for packaging such as confectionery bread and bread. However, the sealant film obtained by this publication requires the addition of a large amount of 1-butene copolymer in order to exhibit sufficient low-temperature heat sealability, and the seal strength becomes unstable due to poor dispersion or the like. In addition, there is a problem that heat sealing performance deteriorates with time. (Patent Document 2)
JP-A 61-106648 JP 2002-154188 A

 The present invention is obtained from a sealant resin composition that is less deteriorated in heat sealability with time, has excellent heat sealability at low temperatures, and can exhibit high seal strength even at a low seal temperature, and the composition. An object is to provide a sealant film, and a laminate and a container using the same.

  The present inventors have found that the above problems can be solved by a film using a specific resin composition, and have completed the present invention.

That is, in the present invention, the melt flow rate (MFR, ASTM D1238, 230 ° C., 2.16 kg load) is 1 to 50 (g / 10 min), and the melting point measured with a differential scanning calorimeter (DSC) is 110 to 150 ° C. A propylene polymer (A) of 30 to 96% by weight, a melt flow rate (MFR, ASTM D1238, 190 ° C., 2.16 kg load) of 0.5 to 50 (g / 10 min), and a density (ASTM D1505) An ethylene / α-olefin random copolymer (B) 2 to 60 having a melting point of less than 90 ° C. and less than 0.850 to 0.900 (g / cm ³ ) and determined by differential scanning calorimetry (DSC). wt%, and the propylene content is 50 to 90 mol%, and a melt flow rate (MFR, ASTM D1238,190 ℃, 2.16kg load 0.1 to 25 (g / 10 min), a resin for sealant formed from 2 to 30% by weight of a propylene copolymer (C) having a melting point measured by a differential scanning calorimeter (DSC) of 100 ° C. or less Relates to the composition.

  Furthermore, this invention relates to the sealant film which consists of a resin composition of the said invention.

  The film obtained from the resin composition of the present invention is excellent in heat sealability at low temperatures, and its industrial utility value is extremely high.

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

Propylene polymer (A)
Examples of the propylene polymer (A) in the resin composition of the present invention include a known propylene homopolymer, or a random or block copolymer with ethylene or an α-olefin having 4 to 20 carbon atoms. The melt flow rate (MFR, ASTM D1238, 230 ° C., 2.16 kg load) of the propylene polymer is 1 to 50 (g / 10 minutes), preferably 1 to 40 (g / 10 minutes), a differential scanning calorimeter A propylene random copolymer having a melting point measured by (DSC) in the range of 110 to 150 ° C, preferably 115 to 140 ° C is preferably used. By using such a random copolymer, a sealant film excellent in low-temperature heat sealability and film appearance can be obtained.

  Such a propylene-based polymer (A) typically contains propylene in the presence of a solid titanium catalyst and a catalyst mainly composed of an organometallic compound or a metallocene catalyst using a metallocene compound as one component of the catalyst. It can be produced by polymerization or copolymerization of propylene and other α-olefins.

Ethylene / α-olefin random copolymer (B)
The ethylene / α-olefin random copolymer used as the component (B) in the resin composition of the present invention is a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms. Is a random copolymer obtained. 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 ethylene / α-olefin random copolymer is 0.5 to 50, preferably 1.0 to 30 (g / 10 min), and the density (ASTM D1505). ) Is 0.850 to less than 0.900 (g / cm ³ ), preferably 0.855 to 0.890 (g / cm ³ ), and the melting point determined by differential scanning calorimetry (DSC) is 90 ° C. Less than or amorphous where no melting point is observed.

  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.

Propylene copolymer (C)
The propylene-based copolymer (C) used in the resin composition of the present invention is a copolymer of propylene and an α-olefin having 2 to 20 carbon atoms, preferably 2 to 10 excluding propylene. Specific examples of the α-olefin include ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene and 1-dodecene, preferably 1-butene. The propylene content in the propylene-based copolymer (C) is 50 to 90 (mol%) , preferably 60 to 80 (mol%).

  Melting | fusing point measured with the differential scanning calorimeter (DSC) of the propylene-type copolymer (C) is 100 degrees C or less. Preferably it is 20-100 degreeC, More preferably, it is the range of 40-90 degreeC.

  Moreover, MFR (190 degreeC) exists in the range of 0.1-25, Preferably it is 0.5-25, More preferably, it is the range of 1-25 (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 propylene-based copolymer (C) is typically propylene in the presence of a catalyst mainly composed of a solid titanium catalyst and an organometallic compound, or a metallocene catalyst using a metallocene compound as one component of the catalyst. And other α-olefins can be copolymerized. Preferably, it is a propylene-based copolymer obtained by copolymerizing propylene and another α-olefin in the presence of a metallocene catalyst, and its molecular weight dispersity (Mw / Mn) is 1.5 to 3.0, preferably Indicates a value of 1.7 to 2.5.

Resin Composition The resin composition of the present invention comprises a propylene polymer (A), an ethylene / α-olefin random copolymer (B) and a propylene copolymer (C), and the mixing ratio thereof is (A ) Is 30 to 96, preferably 30 to 90% by weight, (B) is 2 to 60, preferably 5 to 50% by weight, and (C) is 2 to 30, preferably 5 to 25% by weight. Here, the total amount of (A), (B) and (C) is 100% by weight. When the proportion of each component is within this range, the film obtained from the composition is excellent in low temperature heat sealability and stability over time of the seal strength, and a practically suitable container can be obtained.

  The resin composition of the present invention is characterized in that an ethylene / α-olefin random copolymer having certain properties is used as a component of the resin composition. By using the ethylene / α-olefin random copolymer as described above, a film excellent in low-temperature heat sealability and stability over time of seal strength is obtained. In addition, the sealant film obtained by the resin composition of the present invention has a wide temperature range in which heat sealing is possible, and it is possible to impart easy peel properties by controlling the sealing temperature. Can also be supported.

  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 the above components and various additives as necessary, for example, 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 requiring low temperature heat sealability 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 in the range of 1 to 100 μm, preferably 3 to 80 μm.

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

  Although it does not specifically limit as a base material, Polyolefin films, such as polyethylene and a polypropylene, A film of styrene resin, Polyester films, such as a polyethylene terephthalate and a polybutylene terephthalate, Nylon 6, nylon 6,6, etc. 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, silica, etc. A vapor-deposited film, paper or the like on which is vapor-deposited is appropriately selected and used depending on the intended 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, the resin composition of the present invention is directly extruded and laminated on the base material, or the base material and the sealant film are dry laminated. Alternatively, a method of co-extrusion of resins constituting both layers can be employed.

   As one embodiment of a laminated body, 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 coating agent such as a urethane-based or isocyanate-based adhesive, or a modified polyolefin such as an unsaturated carboxylic acid grafted polyolefin may be used as an adhesive resin to firmly bond adjacent layers. it can.

  Furthermore, the sealant film layers of the laminate film described above face each other, or the sealant film layer of the laminate film and other films face each other, and then at least around the periphery so as to form a desired container shape from the outer surface side. A container can be manufactured by heat-sealing a 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 device for solids such as snacks and bread, powders, or liquid materials.

  Also, a laminate or sheet, or another film or sheet previously formed into a cup shape by vacuum forming or pressure forming, etc., a container obtained by injection molding or the like, or a container formed from a paper substrate, etc. The container in which the contents are packaged is obtained by filling the contents, and then coating the laminate film of the present invention as a lid and 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]
In the three-layer three-layer T-die cast molding machine having a die width of 300 mm, which has an extruder with a screw diameter of 40 mmφ in the core layer and an extruder with a sealant layer and a skin layer of 30 mmφ, using the following resin raw materials, A film having a layer structure of skin layer / core layer / sealant layer (10 μm / 50 μm / 10 μm) was formed at a molding temperature of 220 ° C. and a chill roll temperature of 30 ° C. The heat sealability of the obtained film was evaluated by the following method. The results are shown in Table 1.

Skin layer: Random polypropylene (melting point 138 ° C., MFR (190 ° C.) 7.0 g / 10 min, propylene-ethylene-butene random copolymer)
Core layer: Homopolypropylene (melting point 160 ° C., MFR (190 ° C.) 7.0 g / 10 min)
Sealant layer: As propylene copolymer (A), random polypropylene (melting point 138 ° C., MFR (190 ° C.) 7.0 g / 10 min, propylene-ethylene-butene random copolymer) 70% by weight, ethylene / α-olefin As a random copolymer (B), ethylene / 1-butene copolymer (density 0.885 g / cm ³ , MFR (190 ° C.) 3.6 g / 10 min, 1-butene content 11 mol%, melting point 66 ° C.) 15 % By weight, and propylene-1-butene copolymer (MFR (190 ° C.) 7.0 g / 10 min, propylene content 75 mol%, Mw / Mn = 2.1, melting point 75) as propylene-based copolymer (C) C. produced with a metallocene catalyst) 15% by weight.
(1) Heat sealing property: Two 15 mm strip-shaped test pieces were prepared, the sealing layers were faced to each other, and heat sealing was performed at a predetermined temperature, a pressure of 0.2 MPa, and a sealing time of 1 second. 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). The heat-sealed sample was stored in an oven at 45 ° C. for 7 days, and then the heat-seal strength was measured in the same manner to evaluate the heat-sealability after time.

[Example 2, Comparative Example 1]
The film was evaluated in the same manner as in Example 1 except that the propylene-based polymer, ethylene / 1-butene copolymer, and propylene-based copolymer used as the sealant layer had the contents shown in Table-1. . The results are shown in Table 1.

  As is apparent from the results shown in Table 1, the film of the present invention exhibits high sealing strength at a low sealing temperature. Further, the heat sealability after aging was also good.

The resin composition for sealants of the present invention can be suitably used for food packaging containers because the film obtained therefrom is excellent in heat sealability at low temperatures and has good heat sealability after aging.

Claims (4)

Propylene polymer having a melt flow rate (MFR, ASTM D1238, 230 ° C., 2.16 kg load) of 1 to 50 (g / 10 min) and a melting point of 110 to 150 ° C. measured by a differential scanning calorimeter (DSC) (A) 30 to 96% by weight,
Melt flow rate (MFR, ASTM D1238, 190 ° C., 2.16 kg load) is 0.5 to 50 (g / 10 min), and density (ASTM D1505) is less than 0.850 to 0.900 (g / cm ³ ) 2 to 60% by weight of an ethylene / α-olefin random copolymer (B) having a melting point of less than 90 ° C. determined by differential scanning calorimetry (DSC), and
The propylene content is 50 to 90 mol%, the melt flow rate (MFR, ASTM D1238, 190 ° C., 2.16 kg load) is 0.1 to 25 (g / 10 min), and a differential scanning calorimeter (DSC ) The propylene copolymer (C) having a melting point of 100 ° C. or less measured in 2 to 30% by weight
The resin composition for sealants formed from.   2. The sealant according to claim 1, wherein the propylene copolymer (C) has a molecular weight dispersity (Mw / Mn) of 1.5 to 3 as measured by gel permeation chromatography (GPC). Resin composition.   A sealant film comprising the resin composition according to claim 1 or 2 and having a thickness of 1 to 100 µm.   It is selected from the group consisting of a layer of the sealant film according to claim 3, 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 at least one film layer.