JPH0796283B2 - Easy-cleavable laminated film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a laminated film which is easily cleaved.

[Conventional technology]

In a bag or container made of a thermoplastic such as polypropylene or polyethylene terephthalate as a constituent material, between thermoplastics that are heat-sealed,
Alternatively, a package in which a container body and a lid are hermetically sealed by heat sealing has heretofore been widely used in the field of food and the like.

These film layers are not only heat-sealed to form a structure with excellent sealing reliability, but also the film is easy to open,
That is, it must have a strength such that it can be easily peeled off by hand when it is opened, and at the same time, it must have a smooth peeling interface without surface roughness or feathering. In order to satisfy this requirement, the resin layer is made of polypropylene or polyethylene (for example, JP-A-57-77465) or a polyester copolymer such as polyethylene terephthalate / isophthalate copolymer. Attempts have been made to use it. However, all of these conventional hot air resin layers are insufficient in terms of the smoothness of the peeled surface, and have the drawback that the opening force changes with time.

[Problems to be solved by the invention]

The object of the present invention is to eliminate the above-mentioned drawbacks, the opening surface when opened is constant and smooth, and the change of the opening force with time is slight to the extent that it does not pose a practical problem. It is intended to be provided.

[Means for solving problems]

The present invention provides a styrene-based resin, a methacrylic acid ester-based resin, based on 100 parts by weight of the polyolefin-based resin (a), on at least one surface of a layer A made of the polyolefin-based resin.
A film in which a layer B formed by mixing 15 to 45 parts by weight of at least one resin (b) selected from methylpentene resin, saturated polyester resin and polyamide resin is laminated,
The average dispersion diameter (b value) of the resin (b) in the TD cross section of
0.2 to 10 μm, and the thickness of the layer B is 3 to 2 μm,
The present invention relates to an easily cleavable laminated film having a total thickness of 15 to 350 μm.

The polyolefin resin in the present invention has a melt index (hereinafter abbreviated as MI) measured at 190 ° C. of 0.1 to 50 g.
/ 10 minutes polyethylene or ethylene and other α-
Copolymer with olefin, MI 0.1-50g / measured at 230 ° C
10 minutes polypropylene or propylene and other alpha
Examples thereof include copolymers with olefins, modified polyolefins or ionomers, and mixtures of these polyolefin resins.

The modified olefin described here is a graft polymerization of at least one monomer selected from α, β-ethylenically unsaturated basic acids and their acid anhydrides, esters, amides, and imides with a graft ratio of 20 mol% or less. It was done. Examples include polyethylene grafted with maleic anhydride. Further, the ionomer referred to in the present invention is an α-olefin and 1 to
It is a copolymer with an ionic group of an α, β-unsaturated carboxylic acid containing a trivalent ion. Examples include partial metal salts of ethylene and methacrylic acid copolymers.

The styrene-based resin referred to in the present invention is 70 mol% of styrene.
It is a polymer or copolymer containing the above. Specifically, it refers to, for example, polystyrene, styrene and acrylonitrile, or copolymer of styrene and a rubber-based substance.

The methacrylic acid ester-based resin referred to in the present invention is a polymer or copolymer containing 70 mol% or more of methacrylic acid ester. Specifically, for example, polymethylmethacrylate,
It means polyethyl methacrylate, a copolymer of methyl methacrylate and ethylene or α-methylstyrene, and a copolymer of methyl methacrylate and acrylic acid, methyl acrylate, ethyl acrylate and the like.

The methylpentene resin referred to in the present invention means, for example, poly-4-
Methylpentene-1 resin.

The saturated polyester resin referred to in the present invention is a polyester or copolyester composed of a dicarboxylic acid and a diol, for example, polyethylene terephthalate (PET), polyethylene terephthalate / isophthalate (PET / I).
PET resin such as. Polybutylene terephthalate (PB
T), polybutylene terephthalate / isophthalate (P
PBT resins such as BT / I) and mixtures of these saturated polyester resins can be mentioned.

Note that these resins preferably have an intrinsic viscosity (IV) of at least 0.5 or more.

The polyamide resin referred to in the present invention is a polyamide or copolyamide obtained by polycondensation of a diamine and a dibasic acid, and examples thereof include polycapramide, polyhexamethylene adipamide, polyhexamethylene sebacamide, polyundecane amide, and polydodecaamide. Resins and copolymers and mixtures thereof.

These, styrene resin, methacrylic acid ester resin,
15 to 45 parts by weight, preferably 100 to 100 parts by weight of the polyolefin resin, preferably 1 or more kinds selected from methyl pentene resin, saturated polyester resin and polyamide resin (this may be referred to as resin (b)). Add 20-40 parts by weight. If the amount of the resin (b) added is less than 15% by weight, the easiness of cleavage is poor and the peeled surface is extremely rough, which is not preferable.

If the added amount is more than 45 parts by weight, the cleavage force is low,
It is not preferable because the contents may leak and a feathering defect is likely to occur.

The present invention relates to an easily cleavable film characterized by the resin composition as described above, and in the resin composition, an antioxidant, a heat stabilizer, an ultraviolet absorber, a viscosity modifier, a plasticizer, if necessary. Additives such as agents, organic lubricants and pigments can be dispersed / blended. Inorganic fine particles such as titanium oxide are used in an amount of 0 to 20 parts, preferably 3 to 1 parts, per 100 parts of the resin composition.
0 parts can be added.

The dispersion diameter of the resin (b) as the island component in the present invention means the diameter in the film thickness direction of the resin (b) existing as an island component in the polyolefin of the sea component in the B layer / TD cross section of the film formed. This is a value that can be used as a measure of peeling strength and surface unevenness after peeling. Here, the TD cross section means a cross section when cut in a direction (generally referred to as a width direction) orthogonal to the machine direction in consideration of the film forming process.

The average dispersion diameter (b value) of the resin (b) in the B layer is 0.2 to 1
It is 0 μm, and preferably 0.5 μm to 8 μm. If the average dispersion diameter exceeds 10 μm, the cleavage force at the time of peeling is too strong and the surface irregularities after peeling become large, so that a smooth peeled surface cannot be obtained. On the other hand, if it is less than 0.2 μm, the peeling force is too small, and there is a risk of leakage of the content.

The thickness of layer B is 3 to 25 μm (6 to 50 μm for both sides),
It is preferably 5 to 15 μm. When the thickness of the layer B is less than 3 μm, the unevenness of the cleavage surface is increased and the film is broken, which is not preferable. If it is thicker than 25 μm, a feathering defect is likely to occur, which is not preferable.

The total thickness of the film is 20 to 350 μm, preferably 30 to 250
μm is preferable because it is easy to control the particle size of the polyolefin resin.

Next, a method for producing the film of the present invention will be described, but the method is not limited thereto.

A polyolefin resin is supplied from an extruder X, and a composition obtained by mixing a polyolefin resin and a resin (b) by a dry blend method is supplied from an extruder Y. Both polymers are laminated in the die to form a laminated film.

The average dispersion diameter (b value) of the resin (B) in the layer B is also related to the melt viscosity ratio of the mutual resin of the polyolefin resin (A) and the resin (B) in the form of mixed particles. Although appropriate selection is also necessary, it is particularly important to select the linear velocity of the polymer of the B layer when passing through the lip portion to the die. Preferred film forming conditions for obtaining the dispersed particle diameter (b value) of the resin (b) of the present invention are as follows: the extrusion temperature is in the range of 180 to 290 ° C., the polymer temperature in the head part of the extruder Y is T ₁ , the die is It is preferable that the linear velocity of the polymer passing through the lip portion is 60 cm / min or more at T ₁ -T ₂ = 5 to 45 ° C. when the polymer temperature immediately after discharge is T ₂ . The film forming condition is related to the melt viscosity of the polyolefin resin, but it is preferably carried out within the following range.

When the polymer temperature in the head portion of the extruder Y is T ₁ and the polymer temperature immediately after the die discharge is T ₂ , T ₁ −T ₂ = 5 to 45
At ℃, the linear velocity of the polymer passing through the lip is 6 (cm / mi
It is preferably n) or more. Needless to say, these blended resins may be chips kneaded in advance with a pelletizer.

The constitution of the present invention comprises a layer made of a polyolefin resin (A layer) and a layer made of a polyolefin resin and a resin (B) (B layer) and laminated in the order of A / B or B / A / B. It is a film.

A typical example of this film will be described with reference to the drawings.

Figure 1 shows the TD cross section of the A / B two-layer film, and Figure 2 shows B / A / B.
3 shows a TD cross section of the three-layer film of FIG.

In the figure, 1 is a polyolefin resin layer (A layer), 2 is a layer obtained by blending a polyolefin resin with a resin (B) (B)
Layers) and 3 are resin (b) of island component having an average dispersion of 0.2 to 10 μm.

The composite film thus obtained can be used as a bag, a plastic container, a lid for a container, or the like, as a single body or in a mold in which a metal foil or the like is laminated on the surface of a polyolefin resin layer or the like as necessary. Various layers of polypropylene, polyethylene, or a metal optionally treated with a primer are sealed with a layer containing the resin (b) by a heat sealing method, a high frequency induction heating method, or the like.

The easily cleavable laminated film of the present invention can, of course, be used as a sealant or a container body for containers of various contents including foods, but since the cleavage surface is very good after opening, the peeling surface is directly exposed. It is also suitable for use in contact with, for example, soft drinks such as juice and containers for alcoholic beverages.

[Effects of the Invention] The effects of the present invention are listed below.

(1) Since the cohesive failure force of the film is used, the hermeticity is stable. The cleaving force is stable because the dispersion diameter is controlled.

(2) Since the cleavage plane is determined on the surface layer portion, the cleavage is extremely stable even when the tension angle and the tension speed are changed, and the feathering defect does not occur.

(3) Roughness of the cleaved surface is fine and stable, so that a good peeling appearance and mouth feel are exhibited.

(4) Substantially no change in opening force over time.

(5) The laminated film itself can be used as a lid material.

[Characteristics Measuring Method / Evaluation Criteria] The characteristic measuring methods and evaluation criteria in the present invention are as follows.

(1) Average dispersion diameter of resin (b) Using a microtome manufactured by Nippon Microtome Co., Ltd., the TD cross section of the film is cut to make a section of several μm. This section is photographed at 100 to 200 parts under bright field illumination of an optical microscope and then printed on photographic paper at a total magnification of 1000 to 5000 times. The length of the island component particles in the finished photograph in the thickness direction is measured and used as the particle diameter of the resin (b). The value obtained by calculating the arithmetic mean of the particles present in the B layer using this method is the b value.

(2) Cleavage force: A polypropylene or polyethylene unstretched film having a thickness of about 200 μm and a layer containing the island component resin (b) of the easily cleavable laminated film having a thickness of 15 to 350 μm are overlaid and heated with a heat sealer at a predetermined temperature. Bonding was performed under the conditions of constant sealing pressure and constant sealing time. The sample thus obtained is cut into a strip of 0.5 cm width, and using Tensilon manufactured by Toyo Baldwin at a peeling angle of 180 °, it is pulled at a pulling speed of 500 m / min, and the cleavage strength (kg / cm) at that time is obtained. The cleavage force (opening force) was used. In the case where the cleavage force evaluated in this way was 1.6 to 2.8 kg / cm, the state in which both the sealing property and the easy cleavage property (easy opening property) were compatible was defined as "○", and the other cases were defined as "x".

(3) Cleavage force after lapse of time The cleavage force after leaving for 3 months in an atmosphere of 50 ° C. is shown.

(4) Cleavage surface The surface condition of the film after being cleaved by a natural angle and a natural speed (and 300 to 500 mm / min) by using a surface roughness meter without using a measuring machine. Evaluated by determining the roughness (JIS B0601 method, 0.8m
m cutoff). Those with Ra = 3 μm or less were evaluated as smooth “◯”, those with Ra = 3 μm or more and less than 5 μm were evaluated as somewhat rough “Δ”, and those with Ra = 5 μm or more were evaluated as rough “x”.

(5) Resin temperature The resin temperature T ₁ was measured between the screw of the extruder and the perforated plate using a thermocouple / type IC type. For T _2, the polymer temperature immediately after being discharged from the die (a location about cm away from the die) was measured using a radiation thermometer manufactured by Minolta Co., Ltd.

(6) Polymer Flow Rate Calculated from the discharge amount of polymer and the slit gap area of the T-die.

"Example" Examples 1-8, Comparative Examples 1-8 As a polyolefin resin, polypropylene resin (MI
= 2, 4, 20, 40 g / 10 minutes), a resin obtained by graft-polymerizing propylene with 0.5 mol% of maleic anhydride ((MI = 2),
Select polyethylene resin (MI = 4) and ionization rate 60% zinc metal type ionomer (MI = 0.7).

Polystyrene, polymethylmethacrylate, 4-methylpentene resin, polybutylene terephthalate, and nylon 6 were selected as the resin (b) to be the island component, and these resins were dry blended in the ratios shown in Table 1 and Table 2, respectively. After that, 40mmφ with T-die (slit gap: 0.5mm)
Supply to a 30mmφ compound extruder. A from 40mmφ extruder side
The resin composition of layer B was supplied from the 30 mmφ extruder side. The extrusion temperature of both units was heated to a temperature of 270 ° C. and extruded.

In Examples 1 to 8, Comparative Examples 1 to 4 and Comparative Example 8,
T ₁ −T ₂ = 30 ° C, polymer linear velocity at lip currency is 140 (cm /
min). In Example 2 and Comparative Example 5, the film take-up speed was set to 20 to 30 m / min. In Comparative Example 6, T ₁ -T ₂ is 0.
℃, the polymer linear velocity when passing through the lip is 40 (cm / min)
Was formed as a film. In Comparative Example 7, T ₁ −T ₂ = 50 ° C., and the film was formed at a polymer linear velocity of 230 (cm / min) when passing through the lip.

The thus-obtained two-layer film was heat-bonded to the B side and the PP film (200 μ) under the condition of 200 ° C. for 3 seconds using a heat sealer.

The unsealing force (cleavage force) and the peeling surface state (cleavage surface) of the sample thus obtained before and after aging were determined, and A
The thickness of each layer and the layer B, and the average dispersion diameter b value of the resin (b) in the layer B are shown in Tables 1 and 2.

As can be seen from Table 1, Examples 1 to 8 were also good in opening after passage of time and showed excellent cleavability. Also, the cleaved surface after opening by hand without constant pulling speed and pulling angle
It was 3.0 or less, and was excellent in smoothness. Compared to this,
Comparative Examples 1 and 2 in which the island component resin was not mixed in the B layer or the island component resin was not present did not show any cleavage. Comparative Examples 3, 6 and 6 exhibited the defects that the cleavage force was too large and the unevenness of the cleavage surface after cleavage was too large. In Comparative Examples 4 and 7, the cleavage force was too low, so there was a risk of leakage of the contents, and also a feathering defect occurred. Layer B
In Comparative Example 5 having a thickness of 2.5 μm, the cleavage plane was unstable and the cleavage force was not constant.

[Brief description of drawings]

FIG. 1 is a TD sectional view of a cleavable laminated film according to the present invention having a two-layer structure. FIG. 2 is a TD cross-sectional view of an easily cleavable laminated film according to the present invention having a three-layer structure. In the figure, 1 indicates a layer A made of a polyolefin resin, 2
Shows a layer B composed of a polyolefin resin and a resin (b). 3 is a resin (b).

Continuation of front page (56) Reference JP-A-57-77464 (JP, A) JP-A-56-41161 (JP, A) JP-A-53-99250 (JP, A)

Claims (1)

[Claims] 1. A styrene resin, a methacrylic ester resin, a methylpentene resin, a saturated polyester resin, a polyamide resin based on 100 parts by weight of the polyolefin resin (a) on at least one surface of a layer A made of a polyolefin resin. A film in which a layer B formed by mixing 15 to 45 parts by weight of one or more selected resins (b) is laminated, and the average dispersion diameter (b) of the resin (b) in the TD cross section of the layer B.
Value) is 0.2 to 10 μm, and the thickness of the layer B is 3 to 2
A cleavable laminated film having a thickness of 15 μm and a total thickness of 15 to 350 μm.