JP3720904B2 - Multilayer film - Google Patents

Description

【００３５】
実施例１及び２は、剥離部の糸引きもなく、光沢があるものであり、また剥離強度も適当であり熱間シール性に優れるものであった。
これに対して、比較例１は、剥離強度は適当ではあるが、熱間シール性が劣りヒートシーラント層としてはやや劣るものである。
比較例２は、剥離強度、熱間シール性は適当ではあるが剥離部の切れが悪く外観の劣るものであった。
また、比較例３は、ヒートシール強度が弱く密封性に劣るものであった。
そして、比較例４は、適度の剥離強度はもつものの、剥離が凝集破壊を示し、また熱間シール性も劣るものであった。
【００３６】
【発明の効果】
少なくとも、メタロセン触媒を用いて製造されたエチレンとαーオレフィンとの共重合体を含む薄膜の剥離性ＨＳ層をＰＰ層に形成して多層フィルムは、ポリエチレンとヒートシールしたとき、安定したヒートシール性をもち、界面で滑らかに剥離して開封でき、そして光沢がある剥離部をもつ易開封性包装体を提供する効果を奏する。
そして、ＰＰ層と剥離層及びＰＥ層とからなる多層フィルムは、製膜加工性が優れたものである。
【図面の簡単な説明】
【図１】本発明の多層フィルムの断面を示す概念図である。
【図２】本発明の他の構成の多層フィルムの断面を示す概念図である。
【図３】本発明の多層フィルムを用いた積層シートの例を示す概念図である。
【符号の説明】
１ ＰＰ層
２ 剥離性ＨＳ層
21 剥離層
22 ＰＥ層
３ 接着剤層
４ 二軸延伸ポリエステルフィルム
５ 積層シート[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lid material or a heat sealant layer used relative to a molded container or multilayer film of a laminated material having a polyethylene-based resin as a heat sealant layer, when stable heat sealability, easy peelability and peeling It belongs to a multilayer film that has the characteristics of not stringing.
[0002]
[Problems to be solved by the invention]
As a material to obtain the stability of foreign matter adhesion seal and the hot sealability required for high-speed filling heat seal in order to stably heat seal with polyethylene film as a heat sealant layer and multilayer film, linear It was carried out using polyethylene (hereinafter referred to as LLDPE). However, when LLDPE is used, there is a problem that it is difficult to open because of its high heat seal strength and breaking strength. The present invention is a heat-sealable multilayer film that maintains the stability of heat seal of LLDPE, has a peel strength that is easy to open, has no stringing, has an excellent appearance of the peeled portion, and can be easily peeled at the interface. The issue is to provide
[0003]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a multi-layer film comprising a polypropylene layer (hereinafter referred to as PP layer) as a support layer and a peelable heat sealant layer, and the peelable heat sealant layer (hereinafter referred to as peel). Is a multilayer film comprising a layer containing a copolymer of ethylene and α-olefin polymerized at least using a single site catalyst.
Further, the peelable HS layer includes a peel layer containing a copolymer of ethylene and α-olefin polymerized at least using a single site catalyst on the PP layer, and a polyethylene resin layer (hereinafter referred to as PE layer). .).
[0004]
[Prior art]
The sealing part of the easy-open packaging body by conventional heat sealing is to blend one kind of heat sealant layer with a dissimilar substance that controls the heat sealing strength to reduce the heat sealing strength or to make the interlayer strength of the layer brittle. It was easy to coagulate and break within the layer to provide easy opening.
Some heat seal portions formed in multiple layers have an ultrathin layer, and some have easy-openability by adjusting adhesion strength (peeling strength) with a layer in contact therewith or by cohesive failure.
[0005]
However, the easy-open packaging body in which the heat seal strength is lowered by blending different substances is poor in transparency because the heat sealant layer is blended with an incompatible material, and the composition is uniform. It was difficult to disperse in the film, and it was difficult to avoid non-uniform peelability (unevenness in peel strength).
And the dissociation part which blended dissimilar substances and was coherently destroyed became a rough surface and was not preferable in appearance.
[0006]
A technique is also disclosed in which when a heat sealant layer formed in multiple layers is used as an ultrathin layer and the sealing portion is peeled off, the ultrathin layer is cut and then peeled off from the layer in contact with the layer by interfacial peeling or cohesive failure. . However, if the peeled portion is a cohesive failure, roughening of the peeled portion cannot be avoided due to the unevenness of the peel strength described above, and even if it is interface peeling, it is a trace of cutting an ultrathin layer. There is a problem that it is difficult to prevent a certain stringing phenomenon.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The multilayer film of the present invention comprises a PP layer 1 as a support layer and a peelable heat sealant layer 2 as shown in FIG. 1, and the peelable heat sealant layer 2 is polymerized using at least a single site catalyst. And a multilayer film comprising a layer containing a copolymer of α-olefin.
The peelable heat sealant layer 2 may be a multilayer film 3 in which a peelable HS layer 2 composed of a peel layer 21 and a PE layer 22 is laminated on the PP layer 1 as shown in FIG.
[0008]
The PP layer of the present invention serves as a substrate for forming a multilayer film, and is a polypropylene that does not exhibit cohesive failure even under conditions of a tensile strength of 300 kg / cm ³ and an elongation of 200% or more. . And the grade which can perform a cast sheet or melt extrusion coating is used. The polypropylene may be either a homopolymer or a copolymer. Preferably, in order to adjust the adhesive strength (peel strength) with the peelable HS layer, a copolymer with an α-olefin, an ethylene / vinyl acetate copolymer, an ethylene / acrylic acid copolymer, or an ethylene / acrylic acid It can be formed from a composition in which an ester copolymer, an ionomer and the like are appropriately selected and mixed.
Moreover, you may add suitably the edge part at the time of film forming, and the pulverized product of a scrap to this PP layer.
[0009]
The PP layer is preferably formed by a coextrusion cast film or a melt coextrusion coat together with a single layer peelable HS layer or a peelable HS layer composed of a multilayer peelable layer and a PE layer, 10-60 μm.
The multilayer film of the present invention is preferably formed by coextrusion with a PP layer after thinning a single layer or a multilayer peelable HS layer as described below. As the coextrusion film forming method, a T-die method using a normal flat die or an inflation method using an annular die can be applied.
In the T-die method, either black box type co-extrusion or multi-manifold type may be used. A known annular die can also be used as the die used for the inflation method.
Moreover, it is preferable to perform a corona discharge treatment, an ozone treatment, or the like on the surface of the PP layer on which the peelable HS layer is not provided in order to stabilize adhesion with a printing film or the like. When the other base film is provided by melt coextrusion coating, for example, an isocyanate anchor coat is preferably applied to the base film.
[0010]
The composition containing a copolymer of ethylene and α-olefin polymerized using a single site catalyst used for the peelable HS layer is a single site catalyst (metallocene catalyst, so-called so-called ethylene / α-olefin copolymer). (Including Kaminsky catalyst) is produced from those having a uniform active site (single site). This single-site catalyst is a metallocene-based transition metal compound and an organoaluminum compound or boron compound, and is sometimes used supported on an inorganic substance.
[0011]
The metallocene transition metal compound is a transition metal selected from group IVA of the periodic table of elements, that is, titanium, zirconium, hafnium, cyclopentadienyl group, substituted cyclopentadienyl group, indenyl group, substituted indenyl group, tetrahydroindene. 1 to 2 of nyl group, substituted tetrahydroindenyl group, fluoronyl group, or substituted fluoronyl group are bonded, or two of these groups are covalently bridged, and hydrogen Atoms, oxygen atoms, nitrogen atoms, silicon atoms, halogen atoms, alkyl groups, alkoxy groups, aryl groups, acetylacetonal groups, carbonyl groups, substituents including Lewis bases, and ligands such as unsaturated hydrocarbons It is.
[0012]
Examples of the organoaluminum compound include alkylaluminum, chain-like or cyclic amoxane and the like.
Examples of the alkylaluminum include triethylaluminum, triisobutylaluminum, dimethylaluminum chloride, diethylaluminum chloride, methylaluminum dichloride, ethylaluminum dichloride, dimethylaluminum fluoride, diisobutylaluminum hydride, diethylaluminum hydride, and ethylaluminum sesquichloride.
[0013]
The chain or cyclic aluminoxane is produced by bringing an alkylaluminum into contact with water. For example, it can be obtained by adding alkylaluminum at the time of polymerization, adding water, or reacting crystal water of a complex salt or adsorbed water of an organic / inorganic compound with alkylaluminum.
[0014]
Examples of the inorganic material that supports the single site catalyst include silica gel, zeolite, and diatomaceous earth.
Examples of the polymerization method include bulk polymerization, solution polymerization, suspension polymerization, and gas phase polymerization. These polymerizations may be either batch type or continuous type.
Polymerization temperature, pressure, and time conditions are -100 to 25 ° C, 1 to 50 kg / cm ² , and 0.08 to 10 hours.
[0015]
Examples of the α-olefin copolymerized with ethylene include propylene, 1-methyl-1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and decene. These α-olefins may be used alone or in combination of two or more.
[0016]
The mixing ratio of the α-olefin is usually 0.5 to 70 mol%, preferably 10 to 50 mol%. When the mixing ratio is less than 10 mol%, the adhesive strength with polypropylene may not be obtained, and when the mixing ratio exceeds 50 mol%, the viscosity is high, and when film formation is performed by melt extrusion, Machining becomes difficult because of the heavy load on the processing machine.
[0017]
The ethylene / α-olefin copolymer produced using the metallocene catalyst of the present invention has a melt flow rate of 1.0 to 9.0 g / 10 min (hereinafter referred to as MFR ·· g) and a density of 0.8. Those that do not exceed 930 g / cm ³ are preferable. When the MFR is larger than the above range, it is difficult to form a film by itself, and co-extrusion film formation used for mass production is required. Further, when the MFR is smaller than 1.0 g, there is a problem that it is difficult to flow and film formation cannot be performed. A material having a density of 0.930 g / cm ³ or less is preferred from the viewpoint of excellent low-temperature heat sealing.
[0018]
The peelable HS layer can be provided in a single layer or two-layer configuration, and the PP layer may be a single unit of the ethylene / α-olefin copolymer produced using the above metallocene catalyst, LLDPE, low-density polyethylene (hereinafter referred to as LDPE), ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / acrylic acid ester copolymer, ionomer, etc. are appropriately blended with the above copolymer. You can also use what you did.
Further, the peelable HS layer has an appropriate adhesion, that is, peelability, with the PP layer, and can be firmly heat-sealed with the polyethylene resin.
And it is preferable that the thickness of the peelable HS layer provided in the P layer is 1.5 to 5 μm.
When the thickness of the peelable HS layer is 1.5 μm or less, stable heat sealing cannot be performed, and when it is 5 μm or more, the hot sealability is good and stable as a heat seal, but the peelability when opened. Stringing may occur due to the high breaking strength of the HS layer.
[0019]
As shown in FIG. 2, the peelable HS layer 2 can be composed of a multilayer of a peel layer 21 and a PE layer 22. In this case, the release layer 21 is formed so as to have appropriate adhesiveness (peelability) with the PP layer 1 and to adhere more strongly to the PE layer 22 than to the PP layer 1.
The multi-layer peelable HS layer 2 is composed of the ethylene / α-olefin copolymer produced by using the above metallocene catalyst alone or the LLDPE, LDPE, ethylene / vinyl acetate copolymer. A release layer 21 is formed by appropriately blending a polymer, an ethylene / acrylic acid copolymer, an ethylene / acrylic acid ester copolymer, an ionomer, and the like, and a PE layer 22 is further laminated.
[0020]
The PE layer 22 can be selected from materials that can be heat-sealed with polyethylene in consideration of hot sealability, workability, and the like. For example, LDPE, LLDPE, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / acrylic acid ester copolymer, ionomer, and the like. The thickness is preferably 2 to 4 μm, and by performing coextrusion with the PE layer, the multilayer film has the effect of making the lamina flow uniform and forming a stable film.
[0021]
The total thickness of the multilayer film including the peelable HS layer is preferably 15 to 60 μm, and if it is 10 μm or less, the PP layer has insufficient strength, tends to cause wrinkles, and is difficult to handle as a film. It lacks the cushioning effect required for the sealant layer. On the other hand, if the thickness exceeds 90 μm, the material is wasted and the cost is large.
[0022]
Non-ionic surfactant (eg glycerin fatty acid ester, pentaerythritol fatty acid ester, polyoxypropylene / polyoxyethylene block polymer), anionic to prevent dew condensation on the peelable HS layer or PE layer as necessary A surfactant (for example, alkyl sulfonate <Na, K, ammonium>, alkyl benzene sulfonate, etc.) or an amphoteric surfactant can be added alone or in combination.
[0023]
In order to impart lubricity, a lubricant such as an aliphatic hydrocarbon such as liquid paraffin, synthetic paraffin, and microcrystalline wax, a stearic acid ester of a linear alcohol, and a higher fatty acid amide can be appropriately selected and added.
[0024]
Films to be laminated with the multilayer film of the present invention include stretched or unstretched films such as polyester, polypropylene, polyethylene, polyamide, polycarbonate, polyvinyl chloride, and cellulose triacetate, or single films or composite films such as paper, aluminum foil, and cellophane. .
These films and the multilayer film of the present invention can be prepared by dry lamination, which is a normal processing method, or sandwich lamination using an adhesive resin such as LDPE.
Also, these films can be provided with a picture layer by gravure printing, flexographic printing, silk screen printing or sheet-fed printing as desired.
[0025]
For dry lamination, a two-component reactive adhesive such as normal polyester / isocyanate or polyether / isocyanate, or a polyurethane-based adhesive can be used as the adhesive layer.
Sandwich lamination is also possible by providing a base film with an isocyanate, alkyl titanate or polyethyleneimine anchor coat layer, LDPE, LLDPE, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / acrylic. An acid ester copolymer, an ionomer, or the like can be processed as an adhesive resin with a thickness of 10 to 25 μm.
[0026]
Next, about an Example and a comparative example, the heat sealing property and the easy-openability comparison result are described.
[0027]
【Example】
(Example 1)
As the peelable HS layer 2 shown in FIG. 1, a copolymer (MFR 3.5 g, density 0.910 g / cm ³ ) of ethylene and α-olefin produced using a metallocene catalyst, and homopolypropylene (specified in JIS K7210). MFR 7.0 g) is supplied to a T-die black box type co-extrusion apparatus, and the film is formed by extrusion at a temperature of 240 ° C., and the ethylene / α-olefin co-polymer is formed on one side of the PP layer 1 having a thickness of 50 μm. A polymer was formed to a thickness of 3 μm, and the other surface of the PP layer was subjected to corona discharge treatment to form a multilayer film 3 of Example 1.
[0028]
(Example 2)
As shown in FIG. 2, the PP layer 1 and the ethylene / α-olefin copolymer used in Example 1 were used as the release layer 21, and LLDPE (MFR 2.0 g, density 0.915 g / cm ³ ) was used as the PE layer 22. , Supplied to a T-die black box type co-extrusion apparatus to a thickness of 45 μm, 2 μm and 5 μm, respectively, extruded at a temperature of 240 ° C., and a peelable HS layer 2 of 7 μm on one side of the PP layer 1 The other surface of the PP layer 1 was subjected to corona discharge treatment to form a multilayer film 3 having a total thickness of 52 μm of Example 2.
[0029]
(Comparative Examples 1 and 2)
In the same manner as in Example 1, films were formed so that the peelable HS layer 2 had a thickness of 1 μm and 6 μm, and multilayer films 3 of Comparative Examples 1 and 2 were produced.
[0030]
(Comparative Examples 3 and 4)
In the same manner as in Example 1, the peelable HS layer 2 was replaced with MFR 2.0 g, LLDPE with a density of 0.925 g / cm ³ , and MFR 3.5 g of ethylene butene rubber (EBM), and its thickness was 3 μm. As a result, the multilayer film 3 of Comparative Examples 3 and 4 was prepared.
[0031]
The corona discharge-treated surface of the multilayer film 3 of the above Examples and Comparative Examples and the 12 μm thick biaxially stretched polyester film 4 provided with the polyester / isocyanate-based adhesive layer 3 were combined by dry lamination in FIG. Laminated sheets 5 of Examples and Comparative Examples as shown were prepared.
[0032]
The LDPE surface of a laminate sheet (hereinafter referred to as a laminate PE sheet) of a peelable HS layer 2 of the laminate sheet 5 of the above examples and comparative examples, a polyester sheet having a thickness of 300 μm, and an LDPE film having a thickness of 50 μm. The heat sealability and peelability were evaluated using the following conditions.
[0033]
(Evaluation criteria)
* 1 Peel strength:
At each temperature shown in Table 1, the peelable HS layer of the laminated sheet and the LLDPE surface of the laminated PE sheet were heat sealed under the conditions of a pressure of 1 kg / cm ² and a time of 1 second, a peeling angle of 90 °, and a pulling speed of 300 mm. The peel strength was measured at a width of 15 mm.
* 2 Hot sealability:
At each temperature shown in Table 1, immediately after heat-sealing the peelable HS layer of the laminated sheet and the LLDPE surface of the laminated PE sheet under the conditions of a pressure of 1 kg / cm ² and a time of 1 second, it has not yet cooled and solidified. The peel distance mm is measured and evaluated by applying an external force with a load of 50 g to the heat seal surface.
A material having a small peeling distance is a material excellent in hot sealability.
* 3 Peeling part:
The appearance of the peeled portion of the sample whose peel strength was measured is visually evaluated.
A: Good without stringing.
○: Almost no stringing is observed, which is good.
Δ: Some stringing remains and the commercial value is lowered.
X: The stringing is large and there is a problem as a product.
* 4 Overall evaluation.
A: Appearance of peeled portion, peel strength and hot sealability are good.
○: Appearance of peeled part, peel strength or hot sealability is slightly inferior, but there is no practical problem.
(Triangle | delta): Any of the external appearance of a peeling part, peeling strength, or hot sealing property is a little inferior, and there are some problems as goods.
X: The appearance of the peeled portion, the peel strength or the hot sealability is inferior, and there is a problem as a product.
The evaluation results are shown in Table 1.
[0034]
[Table 1]

[0035]
Examples 1 and 2 were glossy without stringing at the peeled portion, had a suitable peel strength, and were excellent in hot sealability.
On the other hand, Comparative Example 1 has a suitable peel strength but is poor in hot sealability and somewhat inferior as a heat sealant layer.
In Comparative Example 2, the peel strength and the hot sealability were appropriate, but the peeled portion was poor and the appearance was inferior.
In Comparative Example 3, the heat seal strength was weak and the sealing performance was poor.
And although the comparative example 4 had moderate peeling strength, peeling showed cohesive failure and it was also inferior in hot sealing property.
[0036]
【The invention's effect】
At least, when a multi-layer film is heat sealed with polyethylene by forming a peelable HS layer of a thin film containing a copolymer of ethylene and α-olefin produced using a metallocene catalyst into a PP layer, stable heat sealability And has an effect of providing an easy-open packaging body having a glossy peeling portion that can be smoothly peeled and opened at the interface.
And the multilayer film which consists of PP layer, a peeling layer, and PE layer is excellent in film forming processability.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing a cross section of a multilayer film of the present invention.
FIG. 2 is a conceptual diagram showing a cross section of a multilayer film having another configuration according to the present invention.
FIG. 3 is a conceptual diagram showing an example of a laminated sheet using the multilayer film of the present invention.
[Explanation of symbols]
1 PP layer 2 peelable HS layer
21 Release layer
22 PE layer 3 Adhesive layer 4 Biaxially stretched polyester film 5 Laminated sheet

Claims (2)

In a multilayer film composed of a polypropylene layer as a support layer and a peelable heat sealant layer, the peelable heat sealant layer is a layer containing a copolymer of ethylene and α-olefin polymerized using at least a single site catalyst. ,
And the thickness of the said polypropylene layer is 10 micrometers-60 micrometers,
And the thickness of the peelable heat sealant layer is 1.5 μm to 5 μm,
The copolymer of ethylene and α-olefin polymerized using the single site catalyst has a melt flow rate of 1.0 g / 10 min to 9.0 g / 10 min, a density of 0.91 g / cm ^3. multilayer film which is a ~0.93g / cm ^3. The peelable heat sealant layer, and a release layer comprising a copolymer of ethylene and α-olefins which are polymerized using the at least single-site catalyst, a multilayer of polyethylene-based resin layer, and wherein the multi-layer The layer of the film is formed by coextrusion, and the layer structure of the multilayer film is, from the outside, the polypropylene layer as the support layer and the ethylene and α-olefin polymerized using the at least single site catalyst. And the polyethylene resin layer is sequentially laminated , and the polyethylene resin layer has a thickness of 2 μm to 4 μm. Item 11. The multilayer film according to Item 1.

Images