JP3205783B2 - Laminated film and laminated bag for packaging - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminate film and a laminate bag for packaging.

[0002]

2. Description of the Related Art In general, printing is performed on a biaxially stretched polypropylene film, and another film is laminated for the purpose of protecting the printed surface, increasing the strength and improving the heat sealing property, and using the laminated film for packaging. It is well known to use such as. Conventionally, as such a laminated film, a film obtained by printing on a corona discharge treated surface of a biaxially oriented polypropylene-based film, then applying an adhesive to the printed surface, and then laminating a film used as a heat seal layer is usually used. It is used. However, when manufacturing such a laminated film, the use of an organic solvent at the time of applying the adhesive harms the health of workers, and the residue of the solvent becomes a hygienic problem, and it is necessary to dry and evaporate the solvent. However, there is a problem that the cost is high and the pollution of the atmosphere by the vaporized gas cannot be ignored.

In order to solve such problems, the present inventors have previously developed a novel method for producing a laminated film (Japanese Patent Publication No. 63-7933). This method
Printing on the heat-sensitive adhesive material layer surface of the composite biaxially stretched polypropylene-based film having a heat-sensitive adhesive material layer, then ethylene-propylene random copolymer on this printed surface,
This is a method of thermocompression bonding an easily heat-sealable polyolefin film made of a propylene-1-butene random copolymer or a mixture thereof without using an adhesive or a solvent. According to this method, the above problems can be solved, and since the easily heat-sealable polyolefin-based film is mainly composed of propylene, a laminated film excellent in transparency, stiffness, moisture-proof property, etc. can be obtained. Has advantages. However, on the other hand, the laminated film has a drawback that the heat sealing strength is slightly weak and is unsuitable for packaging heavy objects.

[0004]

Means for Solving the Problems In view of this situation, the present inventors have made intensive studies to develop a laminated film capable of solving all of the above-mentioned disadvantages, and as a result, have finally completed the present invention. Was.

[0005] The present invention relates to a biaxially stretched polypropylene film having one side of an ethylene-propylene random copolymer, a propylene-1-butene random copolymer and an ethylene-propylene random copolymer.
Printing on the surface of the heat-sensitive adhesive layer of a composite biaxially stretched polypropylene-based film having a heat-sensitive adhesive layer containing at least one copolymer selected from the group consisting of propylene-1-butene random terpolymer as a main component A laminated film formed by laminating the printed surface and a corona-discharge treated surface of a linear low-density polyethylene film subjected to corona discharge treatment by thermocompression bonding, and a joint seal using the laminated film. The present invention relates to a packaging laminate bag provided with a bottom seal or a three-way seal.

In the present invention, as the ethylene-propylene random copolymer constituting the heat-sensitive adhesive layer, a copolymer having an ethylene content of 0.5 to 15 mol%, preferably 1 to 10 mol%, is selected from propylene. As the -1-butene random copolymer, the 1-butene content is 1 to 3.
Those having a random property of 5 mol%, preferably 5 to 25 mol%, have an ethylene content of 0.5 to 15 as an ethylene-propylene-1-butene random terpolymer.
Those having randomness of 1 mol%, preferably 1 mol% to 10 mol%, and 1-butene content of 0.5 mol% to 35 mol%, preferably 1 mol% to 25 mol% are exemplified. If the value is outside the above range, problems tend to occur in moldability, transparency, adhesion to polypropylene, thermocompression bonding, scratch resistance, blocking resistance, etc., and it becomes difficult to obtain a good laminated film. Therefore, it is hard to say that it is preferable, but it is not impossible to use. In the heat-sensitive adhesive layer of the present invention, various third components may be added to the above copolymer as long as the properties of the layer are not significantly impaired. As such a third component, for example, a polyolefin-based resin such as a linear low-density polyethylene can be exemplified.

In the present invention, the biaxially oriented polypropylene film includes a propylene homopolymer having a boiling n-heptane extraction residue of 90% or more, and an ethylene content of 5 mol%.
Ethylene-propylene copolymer having a melting point lower than that of the copolymer used for the heat-sensitive adhesive layer, and a propylene homopolymer and a propylene-α-olefin copolymer having a total propylene content of 95 mol% or more. Examples of the film include a mixture with a polymer.

[0008] The surface of the heat-sensitive adhesive layer of the composite biaxially oriented polypropylene film of the present invention may or may not be subjected to corona discharge treatment. The corona discharge treatment improves the adhesion to the printing layer, but requires a slightly higher temperature during thermocompression bonding because the surface is oxidized and hardened. Conversely, if the corona discharge treatment is not performed, lamination can be performed at a low temperature during thermocompression bonding, but the adhesion to the print layer is slightly reduced. Regarding the seal strength of the printed portion after lamination, there is no difference between the two even if the corona discharge treatment is performed or not, so it is more preferable not to perform the corona discharge treatment after all.

In the present invention, the printing ink used to form the printing layer is not particularly limited, and any ordinary polyolefin-based ink can be used. The printing layer is not particularly limited, and may be printed on the entire surface or partially printed.

The linear low-density polyethylene film (hereinafter referred to as "L-LDPE") used in the present invention is obtained by copolymerizing ethylene and a C _4-8 α-olefin by a low pressure method. And a film made of a resin whose density is reduced by introducing a short-chain branch into the resin. A film having a density in the range of 0.91 to 0.93 g / cm ³ is preferable. If the density is below 0.91 g / cm ^3, tends to be inferior in terms of blocking and seal strength, whereas if it exceeds the 0.93 g / cm ^3, and requires high temperatures at the time of thermocompression bonding, the dimensions due to heat so that in the laminate before and after Since the change tends to occur, it is difficult to say that each case is preferable, but it is not impossible to use.

[0011] The laminated surface of the L-LDPE of the present invention is:
It is important to perform corona discharge treatment in advance. If the corona discharge treatment is not performed, the laminate strength and the seal strength of the printed portion after the thermocompression bonding are weakened, which causes a drawback that the printed portion cannot be put to practical use. As the strength of the corona discharge treatment, the wetting index is 35 dynes / cm or more, preferably 35 dynes / cm.
It is preferable to adopt a condition so as to be ~ 45 dynes / cm. The L-LDPE used in the present invention may be stretched, but is preferably unstretched from the viewpoint of heat sealability.

In the present invention, the thermocompression bonding is performed to protect a printed portion on the surface of the heat-sensitive adhesive layer and to form a strong heat seal layer. As thermocompression bonding method can be adopted any conventionally known method, it is effective to use a nip roll which is usually heated. For example, d
Tsu one of the up roll is 100~160 ℃, preferably 11
Lamination is performed by passing a metal roll heated to 0 to 150 ° C. and an elastic roll such as a silicon rubber roll at a linear pressure of 5 kg / cm or more, preferably about 20 to 100 kg / cm. When performing thermocompression bonding, L-LD
The surface of the PE that has not been subjected to the corona discharge treatment may be passed through so as to be in contact with the heated metal roll, but is usually elastic so that the heated metal roll is in contact with the polypropylene film layer surface of the composite biaxially oriented polypropylene-based film. When the roll and the non-treated surface of L-LDPE are passed in contact with each other, the lamination can be performed more smoothly.

Thus, the laminate film of the present invention is manufactured. The thickness of each layer constituting the laminate film of the present invention is not particularly limited, but the biaxially stretched polypropylene film layer is usually about 10 to 80 μm, preferably about 15 to 60 μm, and the heat-sensitive adhesive layer is 0.5 to 10 μm. About, preferably about 1 to 5 μm, and the thickness of the L-LDPE film layer is about 10 to 100 μm, preferably about 20 to 60 μm.

Using the bag making machine, the gasket seal (9) and the bottom seal (1)
0), a laminated bag for packaging (refer to FIG. 2) commonly called a joint seal bag, and a three-sided seal (12)
, A packaging laminate bag (refer to FIG. 3) commonly called a three-side seal bag is manufactured. On this occasion,
After packing the article to be packed in such a laminate bag, the opening (1
The method of 1) is arbitrary, but generally, it is preferable to seal by heat sealing or various known methods.
It should be noted that the present invention also encompasses an embodiment in which a so-called automatic packaging machine is used to form a laminated bag containing an object to be packaged by simultaneously packing the object to be packaged while performing bag making using the laminate film of the present invention. At this time, the opening (1 1 ) may be heat-sealed at the same time as the packing object is packed, or the processing of the opening (1 1 ) is free. In forming these bags, heat sealing can be exemplified as a preferable example of forming a seal.

[0015] In the present invention, the laminated film
Another reason for using LDPE films is that L-LD
This is because when a PE film is used as a seal layer, good results are obtained in hot tack property and foreign substance seal property. Hot tack is the strength of the seal when heated.
This hot tack property is particularly important when packaging is performed by an automatic packaging machine that packs articles to be packaged as described above. In addition, the foreign substance sealability refers to the sealing strength when foreign substances enter the seal surface. Since there are cases where the impurities enter, the sealing property of the contaminants is also important.

[0016]

The present invention will be further clarified with reference to the following examples and comparative examples, but the present invention is not limited to these examples. In the following, the density is JIS
It is a value measured from K6760, and the seal strength is a value measured at a tensile speed of 200 mm / min using an Instron universal tester.

Example 1 A polypropylene resin having an MFR of 1.7 and an ethylene-propylene random copolymer resin having an MFR of 9.0 and an ethylene content of 4.5 mol% were co-extruded with a T-die, stretched longitudinally 5 times, and further stretched 10 times. The film was transversely stretched by a factor of 2 to produce a composite biaxially stretched polypropylene film. The polypropylene layer of such a composite biaxially oriented polypropylene-based film has a thickness of 20 μ,
The heat-sensitive adhesive layer had a thickness of 2μ. This composite film was cut into a working width of 600 mm with a slitter and wound up on a paper tube. Next, gravure printing was performed on the heat-sensitive adhesive surface of the film using a thermoviewer (manufactured by Dainippon Ink and Chemicals, Ltd.) as a printing ink.

Example 2 L-LDP having a density of 0.920 g / cm ³ and an MFR of 2.0
After extruding the E resin by a T-die, the resin was subjected to corona discharge treatment and wound up on a paper tube. Next, this L-LDPE film was cut into a working width of 580 mm width using a slitter and wound up on a paper tube. The L-LDPE film thus obtained is
The thickness is 40 μm, and the corona discharge treated surface has a wetting index of 40.
It was Dine.

Example 3 Using the apparatus shown in FIG. 1, the printed surface of the film obtained in Example 1 and the corona-discharge treated surface of the film obtained in Example 2 were brought into contact with each other at 120 m / min. The lamination was performed at the following speed. Laminating conditions were as follows: the surface temperature of the heated metal roll was 135 ° C., and the pressure of the rubber roll was 40 kPa.
g / cm, and the distance in which the film of Example 1 is in contact with the heated metal roll before reaching the pressure-bonded portion is 100 m.
m, the positions of the film supply angle adjustment roll (7) and the film discharge angle adjustment roll (8) were set so that the distance from the position where the film was separated from the heated metal roll after the pressure bonding to the pressure bonding part was 200 mm. Next, using the commercially available gas seal bag making machine and three-side seal bag making machine, the laminated film was formed at a speed of 80 sheets / min.

In addition, sugar as a to-be-packaged product was packaged while forming a seal bag using a continuous automatic packaging machine. The laminate packaging bag formed by heat-sealing the opening was excellent in hot tack properties and also excellent in sealing impurities.

Example 4 The resin constituting the heat-sensitive adhesive layer had a 1-butene content of 20.
A printed biaxially stretched polypropylene-based film was prepared in the same manner as in Example 1 except that a propylene-1-butene random copolymer having an MFR of 8.5 and an MFR of 8.5 was used. Along with the film, a gasket seal bag and a three-side seal bag were prepared in the same manner as in Example 3.

Example 5 The resin constituting the heat-sensitive adhesive layer had an ethylene content of 3 mol%, a 1-butene content of 2 mol%, and an ethylene
A gasket seal bag and a three-sided seal bag were prepared in the same manner as in Example 4 except that a propylene-1-butene random terpolymer was used.

Example 6 A film was prepared in the same manner as in Example 2 except that an L-LDPE resin having a density of 0.905 g / cm ³ and MFR7 was used, and then a film was prepared in Example 3 together with the film obtained in Example 1. A laminate film was prepared in the same manner as described above. Since the L-LDPE surface of the laminate film tends to have a slightly lacking lubricity, it was determined that if it was made into a bag, poor opening properties would be caused, and Nikkalico AS100S [Nikka Rico AS100S] (Trade name) was sprayed in advance, and then a gasket seal bag and a three-sided seal bag were prepared using a bag making machine.

Comparative Example 1 An ethylene-propylene random copolymer resin having an ethylene content of 4.5 mol% and an MFR of 9.0 was extruded by a T-die,
It was subjected to corona discharge treatment and wound up on a paper tube. Next, this film was cut into a working width of 580 mm with a slitter and wound up on a paper tube. The film thus obtained has a thickness of 40 μm and the corona discharge treated surface has a wetting index of 40 μm.
It was Dine. Next, a laminate film was formed from this film together with the film obtained in Example 1 in the same manner as in Example 3, and further, a gasket seal bag and a three-side seal bag were formed.

Comparative Example 2 A propylene-1-butene random copolymer resin having a 1-butene content of 20 mol% and an MFR of 8.5 was used in place of the ethylene-propylene random copolymer resin of Comparative Example 1.
A film was prepared in the same manner as in Comparative Example 1. This film was laminated together with the printed biaxially stretched polypropylene-based film used in Example 4 in the same manner as in Example 3, and further a two-sided seal bag and a three-sided seal bag were prepared.

Comparative Example 3 A biaxially stretched polypropylene film having a thickness of 20 μm having a printed surface on the corona discharge treated surface and the film obtained in Example 2 were coated at a speed of 100 m / min with a commercially available urethane adhesive. For dry lamination. The thickness of the adhesive after drying was 2.5 μm. This laminated film is
After aging overnight at room temperature in a room temperature, a gasket seal bag and a three-sided seal bag were prepared in the same manner as in Example 3.

Table 1 shows the seal strength of the gasket seal bag and the three-side seal bag obtained in Examples 3 to 6 and Comparative Examples 1 to 3.
Are shown together.

[0028]

[Table 1]

The following can be seen from Table 1. That is, the third embodiment
When the seal strengths of the non-printed portion and the printed portion of the laminated bags of Nos. 6 to 6 and the laminated bags of Comparative Examples 1 and 2 are compared, the seal strengths of the laminated bags of Examples 3 to 6 are strong. Also,
When the laminated bags of Examples 3 to 6 are compared with the laminated bag of Comparative Example 3 prepared by dry lamination, the latter has extremely low sealing strength. This is because although the adhesive was cured by aging overnight after dry lamination, the adhesive layer was still sticky even after curing, so it is assumed that the seal strength was low. Furthermore, comparing the seal strength of the non-printed part and the printed part of the laminated bags of Examples 3 to 6, the non-printed part has a higher seal strength, and therefore, the printed pattern that the printed part does not cover the seal part is adopted. Then, it turns out that a bag with very strong sealing strength is obtained.

[0030]

According to the present invention, since no adhesive or solvent is used at the time of lamination, there is no concern about the adverse effects caused by the use of these. Moreover, the laminated film of the present invention has transparency, since the composite biaxially oriented polyolefin-based film is mainly composed of propylene.
It is excellent in stiffness, moisture resistance, etc., and has high heat sealing strength, and can be suitably used for packaging heavy objects.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus for producing a laminated film of the present invention.

FIG. 2 is a perspective view showing one embodiment of a gasket seal bag obtained by the present invention.

FIG. 3 is a perspective view showing one embodiment of a three-side seal bag obtained by the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Feeding out part of printed composite biaxially stretched polypropylene film 2 ... Feeding out part of L-LDPE film 3 ... Winding part of laminate film 4 ... Heated metal roll 5 ... Silicon rubber roll 6 ... Cooling roll 7 ... Film supply angle Adjustment roll 8 ... Film discharge angle adjustment roll 9 ... Gap seal 10 ... Bottom seal 11 ... Opening 12 ... Three-way seal

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (2)

(57) [Claims] 1. A biaxially oriented polypropylene film having one surface selected from the group consisting of an ethylene-propylene random copolymer, a propylene-1-butene random copolymer and an ethylene-propylene-1-butene random terpolymer. A printed layer is provided on the surface of the heat-sensitive adhesive layer of the composite biaxially stretched polypropylene-based film having a heat-sensitive adhesive layer containing at least one copolymer as a main component, and the printed surface is subjected to a corona discharge treatment. A laminated film obtained by laminating a chain low-density polyethylene film with a corona discharge treated surface by thermocompression bonding. 2. A laminate bag for packaging, which is provided with a gasket seal and a bottom seal or a three-way seal using the laminate film according to claim 1.