JP4692140B2 - Polypropylene resin laminated film - Google Patents

Description

  The present invention relates to a polyolefin-based resin laminate film, and more specifically, a polyolefin-based resin laminate having a matte appearance and a strong fusing seal strength, and having good dust adhesion prevention properties and suitable for food packaging, particularly bread wrap packaging applications. It relates to film.

  In recent years, with the diversification of designs required for packaging materials, there is an increasing need for matte films for packaging foods such as bread and confectionery bread and other articles. In addition to the design properties, matte films are more widely used because they are superior to transparent films in terms of physical properties such as rigidity and cold resistance.

The matte surface layer of the matte film is known to have a method of blending a propylene-based block copolymer with a polyethylene resin in order to generate irregularities on the surface to make a matte tone. A method of blending a specific polyethylene resin with a polypropylene resin composed of a propylene copolymer elastomer is disclosed (for example, see Patent Document 1).
In addition, a method of blending 20% high-density polyethylene with a propylene / ethylene block copolymer having an ethylene component of 13% is disclosed (for example, see Patent Document 2).
For example, JP-A-7-233291 JP-A-11-129414

  However, this method has a problem that the interface strength between polyethylene and polypropylene resin is weak, and the fusing seal strength is weak when fusing and sealing the mat surfaces together.

On the other hand, a method is disclosed in which the mat surface layer is composed of only a propylene-ethylene block copolymer to increase the fusing seal strength when fusing and sealing the mat surfaces together (for example, Patent Document 3). reference.).
JP 2002-210897 A

  However, in the patent, “a block copolymer may be selected to obtain an opaque multilayer film”, but in order to obtain a film having a good matte feeling, the composition of the block copolymer is specifically described. In the examples, the amount of amorphous ethylene / propylene random copolymer in the block copolymer is about 8%, and a sufficient matte feeling cannot be expected.

On the other hand, the twist packaging often used in bread wrapping has a structure that may cause dust or insects to fall inside when opened when it is transported or displayed on a shelf of a convenience store, supermarket, etc. Therefore, a package body in which the upper part or the lower part of the twist is heat-sealed is disclosed (for example, see Patent Documents 4 and 5).
JP 2002-172744 A JP 2004-59088 A

  However, even if heat is fused near the twist, there is an undeniable risk that dust will fall on the contents when the heat-sealed part is opened if dust adheres to the twist. .

In order to prevent the adhesion of dust, antistatic properties may be imparted to the heat seal surface.
On the other hand, in order to improve the slidability of the matte surface of the matte film, a method of adding a large amount of a slip agent of 3000 to 9000 ppm to the matte surface layer is disclosed (for example, see Patent Document 6). .
JP 2004-58503 A

Therefore, to prevent the adhesion of dust, in order to improve the sliding of whether One print layer, an antistatic agent in the sealing layer 8000Pp m added pressure, the printing layer is obtained by adding a slip agent in a large amount (For example, refer to Patent Document 7).
JP-A-11-129414

  However, when a large amount of an organic additive is used in this manner, the vaporized antistatic agent and slip agent are scattered in a large amount at the site where the film is produced, thereby deteriorating the environment. Further, when a large amount of antistatic agent or slip agent is deposited on the film surface over time, whitening occurs and the appearance of the film deteriorates.

  An object of the present invention is to obtain a polyolefin-based resin laminated film having an excellent mat feeling and an excellent fusing seal strength, and further to provide a film having no slippage and good slipperiness and antistatic properties.

The present inventors have made intensive studies to achieve the above object, a laminate film consisting of two or more layers of polyolefin resin of at least the seal layer and the print layer, wherein each layer possess the following properties, is the film is not less 60% or more, heat-sealing strength of the film is 15N / 15 mm or more and a polyolefin resin haze variation after 30 days of treatment at 40 ° C. is characterized der Rukoto 1% It was found that the laminated film has both a matte feeling and a strong fusing seal strength.
(1) sealing layer propylene random copolymer (A) consisting of 5 0 mass% or more comprising a resin.
(2) Printed layer A resin containing 95% by mass or more of the propylene-based block copolymer (B) satisfying the following characteristics a) to c), an antistatic agent containing at least an alkyl sulfonate, 3000 to 8000 ppm, Consists of.
a) Ethylene content [a] is 8 to 16% by mass
b) Xylene-soluble fraction [b] at 20 ° C. is 14 to 25%
c) [a] / [ b ] is in the range of 0.5 to 0.7

  In this case, it is preferable to add 3000 to 8000 ppm of an antistatic agent containing at least an alkyl sulfonate to the printed layer.

  In this case, it is preferable that an intermediate layer mainly composed of a propylene-based block copolymer (C) having a xylene-soluble content ratio at 20 ° C. of 6 to 25% is provided between the sealing layer and the printing layer. It is.

  Furthermore, in this case, it is preferable that the thickness ratio of the seal layer is 10 to 30% of the whole.

Furthermore, in this case, the heat sheet Lumpur strength when heat sealed at 80 ° C. the seal layer to each other 0.3 N / 70 mm or more, a heat sheet Lumpur strength when heat sealed at 90 ° C. 0.3 It is preferable that it is -3.0N / 70mm.

The polyolefin-based resin laminated film of the present invention has a high fusing seal strength and eliminates the risk of breaking the gusset portion when filling the contents. Moreover, since it is very excellent in a mat feeling, it can be preferably used for various food packaging, particularly for the square bottom packaging of bread.
Furthermore, it is possible to prevent dust from adhering to the surface of the printing layer without whitening.

Propylene Random Copolymer (A): The propylene random copolymer (A) according to the present invention preferably has a melting point of 120 ° C to 150 ° C. The propylene random copolymer (A) in such a range is a copolymer of propylene and an α-olefin having 2 to 10 carbon atoms, and examples of the α-olefin include ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene and the like can be mentioned. In these, the random copolymer with ethylene and / or 1-butene is preferable. The amount of α-olefin is preferably in the range of 4 to 10% by weight.

  Further, the melt flow rate of the propylene random copolymer (A) is not particularly limited as long as it can be used as a film, but is usually in the range of 1 to 20 g / 10 minutes, preferably in the range of 2 to 10 g / 10 minutes. It is in.

Further, the seal layer in the present invention contains 50% by weight or more of the propylene random copolymer. In order to impart low temperature sealability, ethylene such as ethylene 1-butene, ethylene hexene-1 and ethylene octene is used. -It is preferable to mix | blend alpha-olefin copolymer etc. in the range which does not exceed 50 weight %. When it exceeds 50% by weight , the blocking resistance is deteriorated and the rise of the seal strength is abrupt, and there is a risk that the film is broken when the seal portion is peeled off.

Propylene Block Copolymer (B) The propylene block copolymer (B) according to the present invention has an ethylene content [a] of 8 to 16% by mass and a ratio of xylene soluble part at 20 ° C. [b ] Is in the range of 14 to 25%, and [a] / [b] is in the range of 0.5 to 0.7. If the ethylene content [a] is less than 8% by mass or the xylene-soluble part ratio [b] is less than 14% or [a] / [b] is less than 0.5, the mat feeling is insufficient. When the ethylene content [a] exceeds 16% by mass, the xylene soluble part ratio [b] exceeds 25%, or [a] / [b] exceeds 0.7, the fusing seal strength is The harmful effect of lowering occurs.
At this time, in order to obtain a matte, it is preferable that the haze to the film is 60% or more.
Moreover, heat-sealing strength Oh Rukoto preferably at 15N / 15 mm or more, more preferably 17N / 15 mm or more.

  The melt flow rate of the propylene-based block copolymer (B) is not particularly limited as long as it can be used as a film, but is usually 0.5 to 10 g / 10 minutes, preferably 2 to 8 g / 10 minutes. It is in the range. When the melt flow rate is less than 0.5 g / 10 minutes, the productivity is poor, and when it exceeds 10 g / 10 minutes, the impact resistance is poor.

  In the present invention, a resin containing 95% by mass or more of the propylene-based block copolymer (B) is used for the printing layer.

  As resin components other than the propylene-based block copolymer (B), a propylene homopolymer and a random copolymer composed of propylene and less than 10% α-olefin are desirable. Other than these, high density polyethylene, low density polyethylene, propylene-ethylene elastomer, ethylene / α-olefin copolymer, and the like can be mentioned. Resins having low compatibility with these propylene block copolymers (B) In order to reduce the fusing seal strength, the blending ratio is desirably 2% or less.

  Propylene-based block copolymer (C): The propylene-based block copolymer (C), which is the main constituent of the intermediate layer, preferably has a xylene-soluble content ratio at 20 ° C. of 6 to 25%. If the xylene-soluble fraction at 20 ° C. is less than 6%, the film tends to tear, and if it exceeds 25%, the rigidity of the film may be insufficient.

  Further, the melt flow rate of the propylene-based block copolymer (C) is not particularly limited as long as it is in a range that can be used as a film, but is usually 0.5 to 10 g / 10 minutes, preferably 2 to 8 g / 10 minutes. It is in the range. When the melt flow rate is less than 0.5 g / 10 minutes, the productivity is poor, and when it exceeds 10 g / 10 minutes, the impact resistance is poor.

In the present invention, it is preferable to blend 3000 to 8000 ppm of an antistatic agent containing at least an alkyl sulfonate in the printing layer. When the concentration of the antistatic agent is less than 3000 ppm, the slipperiness of the outer layer surface is insufficient, and the antistatic property of the outer layer surface is insufficient, so that dust easily adheres to the upper portion of the twist portion. On the other hand, the concentration of the antistatic agent is more than 8000 ppm, or too low slipperiness in summer, or turned into adversely workability tend to whitening by bleeding of the antistatic agent. Moreover, if an alkyl sulfonate is not blended in the antistatic agent, the slipperiness in winter may be deteriorated.
In the present invention, the degree of whitening of the film due to bleeding of the antistatic agent is preferably 1 to 2%, more preferably 1% or less, before and after standing at 40 ° C. for 30 days.
Also, sliding property [tan .theta] of the printing surface layer is preferably in under 0.5 nonzero.

  There are no particular restrictions on the components of antistatic agents other than alkyl sulfonates, but nonionic antistatic agents such as glycerin fatty acid esters, sorbitan fatty acid esters, poly (oxyethylene) alkylamines, alkylbenzene sulfonates, and alkyl sulfates. There are anionic antistatic agents and cationic antistatic agents such as quaternary ammonium chloride, but nonionic, particularly glycerin fatty acid esters are preferred in terms of heat resistance and durability.

  In the present invention, the thickness ratio of the inner layer is preferably 10 to 30% of the entire film. If it is 10% or less, the film tends to tear, and if it exceeds 30%, the film becomes weak.

  Moreover, although the thickness of the whole film changes with the uses and usage methods, it is generally 10-150 micrometers, Preferably it is about 20-100 micrometers.

Furthermore, in the polyolefin-based resin laminated film of the present invention, it is common to add various additives such as a heat stabilizer, an anti-blocking agent and a slip agent to the sealing layer and the printing layer within a range that does not impair the effect. In order to obtain blocking resistance especially for the sealing layer, it is selected from inorganic fine particles such as silicon dioxide, zeolite, aluminum borate, calcium carbonate, and organic cross-linked fine particles such as methyl acrylate and styrene-butadiene. It is preferable to add one or more inert fine particles in a range of 2000 to 15000 ppm. Although there is no restriction | limiting in particular as an average particle diameter of these fine particles, 2-15 micrometers is preferable when the improvement effect of blocking resistance, transparency, etc. are considered.
In the present invention, it is preferable that the surface resistivity of the sealing layer surface [log .OMEGA] is below 1 4 or less.

  As a method for producing the polyolefin resin laminated film of the present invention, it is preferable to apply a coextrusion molding method such as a T-die method or an inflation method. Further, the film forming conditions are not different from those of a general polyolefin film production method, and are heated and melted so that the resin temperature becomes 150 to 300 ° C., and cooled on a cooling roll of 10 to 80 ° C. or air-cooled. And can be obtained by solidifying.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, but may be implemented with appropriate modifications within a scope that can meet the gist of the present invention. These are all included in the technical scope of the present invention.

  The measurement and evaluation methods employed in this specification are as follows.

[MFR (melt flow rate)]
According to the 2004 edition of JIS K7210, measurement was performed by the method of Condition-14 (load 2.16 kg, temperature 230 ° C.).

[Melting point]
About 6 mg of the propylene-based copolymer (C) is weighed, and heated to 200 ° C. at a rate of temperature increase of 10 ° C./min using a differential scanning calorimeter (type 5200) manufactured by Seiko Denshi Kogyo Co., Ltd. After holding at 200 ° C. for 5 minutes, the temperature is lowered at a cooling rate of 100 ° C./min to 0 ° C., and the temperature rising rate is again measured at 10 ° C./min. From this melting curve, the method of JIS-K-7121 9.1 was followed, and the temperature at the top of the melting peak on the highest temperature side from the melting curve was taken as the melting point.

[Ratio of xylene soluble part at 20 ° C. (%)]
After 5 g of the sample was completely melted in 500 ml of boiling xylene, the temperature was lowered to 20 ° C. and left for 4 hours or more. Thereafter, the precipitate and the solution were separated by filtration, and the filtrate was dried and dried at 70 ° C. under reduced pressure. From the weight of the obtained dried product, the 20 ° C. xylene-soluble part amount was measured and the ratio was determined.

[Ethylene content]
It was measured by ¹³ C-NMR method according to the method described on page 616 of Polymer Handbook (1995, published by Kinokuniya Shoten).

[Haze]
In accordance with 2004 edition JIS-K-6714, measurement was performed using “Haze Tester J” manufactured by Toyo Seiki Seisakusho.

[Blocking resistance]
In accordance with ATM-D1893-67, a load of 90 N was applied to the area of A4 size, left for 2 hours in an atmosphere of 60 ° C., then the load was removed, and the peeling resistance with a φ5 aluminum rod was measured under the condition of a moving speed of 100 mm / min. It was measured.

[Heat seal strength]
Using a heat sealer (PP-701-B) manufactured by Tester Sangyo Co., Ltd., the width direction of the heating bar is fixed at a lower bar temperature of 80 ° C. in a direction orthogonal to the flow direction of the film, and sealed at 0.1 MPa × 3 seconds, The peel strength was measured at a width of 70 mm to obtain the heat seal strength.

[Fusing seal strength]
Prepare two film rolls, pull out each film and set it so that the sealing faces of the film face each other, and then fold it in two to an automatic bag making machine (PP5500 model made by Kyoei Printing Machinery Materials Co., Ltd.) Supplied. Then, sealing and bag making were performed at a temperature setting of 300 ° C. with a fusing seal blade (blade edge angle of 60 degrees) and a bag making speed of 100 bags / min. Then, the seal portion was cut out to a width of 15 mm, two films were attached to the upper and lower chucks of Tensilon, and the fusing seal strength between the printing surfaces was measured at a width of 15 mm under the condition of a crosshead speed of 200 mm / min.

[Bleed whitening]
The haze before and after the film was subjected to an aging treatment at 40 ° C. for 30 days was measured. The case where the change rate of haze was 1% or less was evaluated as ◯, the case where 1-2% was exceeded, and the case where it exceeded 2% were evaluated as ×.

[Average particle size]
The volume average particle size was determined using a laser diffraction particle size distribution analyzer (Nikkiso Microtrac HRA model 9320-X100 (Leeds & Northrup)).

[Surface resistivity (logΩ)]
The polyolefin-based resin laminated film was prepared for 16 hours under the environment of 23 ° C. and 50% relative humidity in accordance with 2004 edition JIS K-6911 5.13 resistivity, and then the surface resistivity of the outer layer surface was measured.

[Measurement of thickness of film, seal layer, and laminate layer]
A film cross section was cut out and measured with an optical microscope using reflected light.

(Polymer used)
The polymers used in Examples and Comparative Examples are shown below.
1) Propylene random copolymer (A): propylene random copolymer containing ethylene content 4% by mass, 1-butene content 4% by mass, melt flow rate 7.0 g / 1 min, melting point 130 ° C. .
2) Ethylene / α-olefin copolymer: 28% by mass of hexene-1 as a comonomer, a melt flow rate of 3 g / 10 min, and a density of 0.890 g / cm ³ .
3) Propylene-based block copolymer (B): ethylene content is 13% by mass, the ratio of xylene-soluble parts at 20 ° C. is 25%, the melt flow rate is 4 g / 10 min, and the melting point is 163 ° C.
4) Propylene-based block copolymer (C): ethylene content is 7% by mass, the ratio of the xylene soluble part at 20 ° C. is 11%, the melt flow rate is 4 g / 10 min, and the melting point is 163 ° C.
5) High density polyethylene: density is 0.940, melting point is 126 ° C., melt flow rate is 2 g / 10 min.
6) Antistatic agent masterbatch: Propylene-ethylene random copolymer having an ethylene content of 6% by mass and a melt flow rate of 8 g / 10 min, an antistatic agent having a glycerin fatty acid ester / sodium alkyl sulfonate = 70/30 wt% Contains 15% of the agent.

(Multilayer film forming method)
A polymer and additives were blended as shown in Table 1, and a three-layer film was formed by a three-layer T-die coextrusion cast molding machine so that the total film thickness was 30 μm. The layer thickness ratio of the film was set to inner layer / intermediate layer / outer layer = 15/65/20. The die outlet resin temperature was 250 ° C. for the seal layer and the printing layer, 260 ° C. for the intermediate layer, and the temperature of the cooling roll was 25 ° C. Further, the corona treatment was performed on the outer layer surface so that the surface tension was 40 mN / m.

(Examples 1-2, Comparative Examples 1-4)
A multilayer film was produced and evaluated as described above using the resin composition shown in Table 1. The evaluation results are shown in Table 1.

Since the polyolefin-based resin laminated film of the present invention has a matte feeling and excellent fusing seal strength, it can be used in a wide range of packaging fields for foods such as bread and confectionery bread and other articles, and contributes greatly to the industry. It is.
Furthermore, there is little whitening and it is excellent in slipperiness and antistatic property.

Claims (3)

A laminated film consisting of two or more layers of polyolefin resin of at least the seal layer and the print layer, wherein each layer possess the following properties, and a haze to the film is 60% or more, heat-sealing strength of the film is 15N / polyolefin resin laminate film and a 15mm or more, and the haze variation after 30 days of treatment at 40 ° C. is characterized der Rukoto than 1%.
(1) sealing layer propylene random copolymer (A) consisting of 5 0 mass% or more comprising a resin.
(2) Printed layer A resin containing 95% by mass or more of the propylene-based block copolymer (B) satisfying the following characteristics a) to c), an antistatic agent containing at least an alkyl sulfonate, 3000 to 8000 ppm, Consists of.
a) Ethylene content [a] is 8 to 16% by mass
b) Xylene-soluble fraction [b] at 20 ° C. is 14 to 25%
c) [a] / [ b ] is in the range of 0.5 to 0.7 It is a polyolefin resin laminated film of Claim 1 , Comprising: The propylene block copolymer (C) whose xylene soluble content ratio in 20 degreeC is 6-25% between the said seal layer and a printing layer. A polyolefin-based resin laminated film comprising an intermediate layer as a main component. 3. The polyolefin resin laminated film according to claim 1, wherein a thickness ratio of the seal layer is 10 to 30% of the whole.