JPS6387229A - Easily cleavable laminated film - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a laminated film that is easily folded.

[Conventional technology]

In bags or containers made of thermoplastic plastics such as polypropylene or polyethylene terephthalate, sealing is performed between the thermoplastic plastics to be heat-sealed or between the container body and the lid. BACKGROUND ART Packaging bodies have conventionally been widely used in fields such as food products.

These film layers are not only heat-sealed to form a structure with excellent sealing reliability, but also have easy-to-open,
In other words, it must have enough strength to be easily peeled off by hand when opening, and at the same time, it must have a smooth peeling interface with no surface roughness or feathering.This requirement is met. In order to achieve this, attempts have been made to use a resin layer based on polypropylene or polyethylene (for example, JP-A-57-77465), or a polyester copolymer such as polyethylene terephthalate/isophthalate copolymer. However, all of these conventional hot air resin layers are
The problem is that the smoothness of the peeling surface is insufficient, and the opening force changes with oral administration.

[Problem that the invention seeks to solve]

The purpose of the present invention is to eliminate the above-mentioned drawbacks, and to provide an easily cleavable laminated film which has a constant and smooth opening surface when opened, and whose opening force changes over time so little that it does not pose a practical problem. This is what we intend to provide.

[Means for solving problems]

The present invention is made of polyolefin resin! On at least one side of A, one or more resins selected from styrene resins, methacrylate resins, methylpentene resins, saturated polyester resins, and polyamide resins (b) are added to 100 parts by weight of the polyolefin resin (a). 15-45
A film laminated with a layer B formed by mixing heavy parts,
The average dispersion diameter (
b value) is 0.2 to 10 μm, the thickness of the layer B is 3 to 25 μm, and the total thickness is 15 to 350 μm.

The polyolefin resin in the present invention refers to polyethylene or a copolymer of ethylene and α-olefin having a melt index (hereinafter abbreviated as MI) of 0.1 to 50 g/10 min measured at 190°C; Examples include polypropylene, copolymers of propylene and other α-olefins, modified polyolefins or ionomers, or mixtures of these polyolefin resins, which have an MIo measured at 230°C of 1 to 50 g/10 min. can.

The modified olefin described here refers to polyolefin with α
, β-ethylenically unsaturated basic acids and their acid anhydrides, esters, amides, imides, etc., are graft-polymerized at a graft ratio of 20 mol % or less. Examples include polyethylene grafted with maleic anhydride. In addition, the ionomer referred to in the present invention refers to α-olefin and 1-
It is a copolymer of an α,β-unsaturated carboxylic acid containing a trivalent metal ion and an ionic group. As an example, mention may be made of partial metal salts of copolymers of ethylene and methacrylic acid.

The styrenic resin referred to in the present invention is a polymer or copolymer containing 70 mol% or more of styrene.

Specifically, it refers to, for example, polystyrene, a copolymer of styrene and acrylonitrile, or a copolymer of styrene and a rubber-based substance.

The methacrylic acid ester resin used in the present invention is a polymer or copolymer containing 70 mol% or more of methacrylic acid ester. Specifically, for example, polymethyl methacrylate, polyethyl methacrylate, copolymers of methyl methacrylate and ethylene or α-methylstyrene, methyl methacrylate and acrylic acid, methyl acrylate, ethyl acrylate, etc. A copolymer.

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

The saturated polyester resin referred to in the present invention is a polyester or copolyester consisting of dicarboxylic acid and diol, such as polyethylene terephthalate (PET).
, polyethylene terephthalate isophthalate (PE
PET resin such as T/I). Examples include PBT resins such as polybutylene terephthalate (PBT) and polybutylene terephthalate isophthalate (PBT/I), and mixtures of these saturated polyester resins.

Note that these resins have an intrinsic viscosity (IV) of at least 0.
It is preferable that it is 5 or more.

The polyamide resin used in the present invention refers to polyamides and copolyamides formed by polycondensation of diamine and dibasic acid, such as polycapramide, polyhexamethylene adipamide, polyhexamethylene sebacamide, polyundecaneamide, polydodecanamide, etc. Examples include resins such as amides, and copolymers and mixtures thereof.

One or more of these selected from styrene resin, methacrylate ester resin, methylpentene resin, saturated polyester resin, and polyamide resin (this may be referred to as resin (b)) is added to 100 parts by weight of polyolefin resin. It is added in an amount of 15 to 45 parts by weight, preferably 20 to 40 parts by weight.

If the amount of resin (b) added is less than 15% by weight, it is not preferable because the ease of folding is poor and the peeling surface becomes extremely rough.

If the amount added is more than 45 parts by weight, the inter-fold force is low, so there is a risk of the contents leaking, and feathering defects are likely to occur, which is not preferable.

The present invention relates to an easily creased film characterized by the resin composition as described above, and the resin composition may optionally contain an antioxidant, a heat stabilizer, an ultraviolet absorber, a viscosity modifier, Additives such as plasticizers, organic lubricants, and pigments can be dispersed and blended.

In addition, inorganic fine particles such as titanium oxide are added to the resin composition 10.
0 parts to 20 parts, preferably 3 to 10 parts can be added.

In the present invention, the dispersed diameter of the resin (b) as an island component is the diameter in the film thickness direction of the resin (b) present as an island component in the sea component polyolefin in the B layer/TD cross section of the formed film. That is, peel strength,
This is a value that can be used as a guide for surface unevenness after peeling. Here, the TD cross section refers to a cross section cut in a direction (generally referred to as the width direction) orthogonal to the machine direction when considering the film forming process.

The average dispersion diameter (b value) of the resin (b) in layer B is 0.2
~10 μm, preferably 0.5 μm to 8 μm. If the average dispersion diameter exceeds 10 μm, the opening force during peeling is too strong and the surface unevenness after peeling becomes large, making it impossible to obtain a smooth peeled surface. Also, 0.2
If it is less than μm, the peeling force is too small and there is a risk that the contents may leak.

The thickness of Bff is 3 to 25 μm (6 to 50 μm for both sides)
m), preferably 5 to 15 μm. The thickness of layer B is 3
If it is less than μm, it is not preferable because the unevenness of the actual opening surface becomes large or the film breaks. Also 25 μm
If it is thicker, feathering defects are likely to occur, which is undesirable.

The total thickness of the film is 20 to 350 μm, preferably 3
0 to 250 μm is preferable from the viewpoint of ease of controlling the particle size of the polyolefin resin.

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

A polyolefin resin is supplied from an extruder Both polymers are laminated within the base to form a laminated film.

Although the film forming conditions are related to the melt viscosity of the polyolefin resin, it is preferable to carry out the film forming conditions within the following range.

When the polymer temperature at the head of extruder Y is T1 and the polymer temperature immediately after discharge from the nozzle is T2, T1-T2
=5 to 45°C, and the linear velocity of the polymer passing through the lip portion is preferably 60 (cm/min) or more.

Of course, these blended resins may be used in the form of chips that have been kneaded in advance with a pelletizer.

The structure of the present invention consists of a layer made of polyolefin resin (layer A) and a layer made of polyolefin resin and resin (b) (layer B), in the order of A/B or B/A/
This is a film laminated in the order of B.

Representative examples of this film will be explained based on the drawings.

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

In the figure, 1 is a polyolefin resin layer (A layer), 2 is a layer (B layer) that is a blend of polyolefin resin and resin (B), and 3 is an island component resin with an average dispersion diameter of 0.2 to 10 μm. (b) is shown.

The composite film thus obtained can be used as a bag, a plastic container, or a lid material for a container, either alone or in the form of a polyolefin resin layer laminated with metal foil, etc., if necessary. The layer containing the resin (B) is sealed with various containers such as polypropylene, polyethylene, or metal treated with a primer if necessary, using 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 container body for containers containing various contents including foods, but since the cleavage surface is extremely good, the peeling surface can be easily removed. It is also suitable for applications where water comes into direct contact with the mouth, such as containers for soft drinks such as juice and alcoholic beverages.

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

(1) Because it utilizes the cohesive breaking force of the film,
Stable sealing performance. Since the dispersion diameter is controlled, the interfold force is also stable.

(2) Since the inter-fold plane is determined in the surface layer, the inter-fold plane is extremely stable even when the pulling angle and speed are changed, and feathering defects do not occur.

(3) The roughness at the interface between folds is fine and stable;
Shows good peel appearance and dryness.

(4) There is virtually no change in opening force over time.

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

[Method for Measuring Properties and Criteria for Evaluation] The methods for measuring properties and the criteria for evaluation in the present invention are as follows.

(1) Average dispersion diameter of resin (b) Using a microtome manufactured by Japan Microtome Co., Ltd., cut the TD cross section of the film to create a section of several μm.

After photographing this section under bright field illumination with an optical microscope at 100x to 200x, it was printed on photographic paper at a total magnification of 1000x to 5x.
Burn it 000 times.

The length of the island component particles in the completed photograph in the thickness direction is measured and determined as the particle diameter of the resin (b).

Using this method, the value obtained by calculating the arithmetic average of the particles present in the B layer is the b value.

(2) An unstretched polypropylene or polyethylene film with a thickness of about 200 μm and a layer containing the island component resin (b) of an easily cleavable laminated film with a thickness of 15 to 350 μm are laminated together and heated to a predetermined temperature using a heat sealer. Bonding was performed under conditions of constant sealing pressure and constant sealing time. The samples obtained in this way were cut into strips with a width of 5 cm and pulled at a peeling angle of 180o using a Tensilon manufactured by Toyo Baldwin Co., Ltd. at a tensile speed of 500 m/min, and the interwing strength at that time (ki/ cm) was defined as the interfold force (opening force).

The interfold force evaluated in this way was 1.6 to 2.8 kJ/
cm, the state where both sealability and easy foldability (easy openability) were achieved was rated "○", and the other cases were rated rXJ.

(3) Keihitsu's inter-fold force The inter-fold force was expressed as the inter-fold force after being left in an atmosphere of 50°C for 3 months.

(4) A surface roughness meter was used to measure the surface condition of the film after the creases were measured by hand at a natural angle and at a natural speed (approximately 300 to 500 mm/m1n) without using a crease surface measuring device. Evaluation was made by determining the surface roughness (JIS
BO601 method, 0.8m1i cutoff). Ra =
Those with Ra of less than 3 μm were designated as smooth rOJ, those with Ra = 3 μm or more and less than 5 μm were designated as rough rOJ, and those with Ra = 5 μm or more were designated as rough rXJ.

(5) Resin temperature The resin temperature T1 was measured using a thermocouple type IC between the screw and the perforated plate of the extruder. Also T2
is the direct polymer temperature discharged from the nozzle (approximately 1
0m! The temperature was measured using a Minolta radiation thermometer.

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

[Example] Examples 1 to 8, Comparative Examples 1 to 7 Polypropylene resin (M
I=2.4.20.40g/10min), 0 in propylene
．． Resin graft-polymerized with 5 mol% maleic anhydride (
MI=2), polyethylene resin (MI=4) and ionization rate 60% zinc metal type phionomer (MI=0.7).
> Select.

Polystyrene, polymethyl methacrylate, 4-methylbentene resin, polybutylene terephthalate, and nylon 6 were selected as the resin (b) to be the island component, and these resins were triblended in the ratios shown in Tables 1 and 2, respectively. After that, 4 with a T-die (slit gap: 0.5 mm)
Supplied to qmmφ and 30mmφ composite extruders. 40m
The resin composition for layer A was supplied from the mφ extruder side, and the resin composition for layer B was supplied from the 3qmmφ extruder side.

In Examples 1 to 8 and Comparative Examples 1 to 4, T1-T2=
20~30℃, polymer wire speed when passing through lip is 117~
It was 140. In Example 2 and Comparative Example 5, the film take-up speed was 20 to 30 m/min. Comparative example 6 is T
1-T2 was set to 0 to 5°C, and the polymer wire speed when passing through the lip was set to 30 to 5Q (cm/min>. was coated with a film of 200 or more.

Using a heat sealer, 8 sides of the two-layer film obtained in this manner and a PP film (200 μm) were thermally bonded at 200° C. for 3 seconds.

The opening force (opening force) and peeling surface condition (interfold surface) before and after aging of the 1q sample thus obtained were determined, and A
The thicknesses of the layers and the B layer are shown in Tables 1 and 2 together with the average dispersion diameter of the resin (B) in the B layer.

As seen in Table 1, Examples 1 to 8 were easy to open after oral administration, and exhibited excellent interfoldability. In addition, the surface between the folds after opening by hand without keeping the pulling speed and pulling angle constant was 3.
．． It was 0 or less and had excellent 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 inter-fold property. In Comparative Examples 3 and 6, the opening power was too large;
The problem was that the unevenness of the interfold surface after opening was too large. In Comparative Examples 4 and 7, the opening power was too low, so there was a risk that the contents would leak, and feathering defects also occurred.

In Comparative Example 5, in which layer B was 2.5 μm thick, the interfold plane was unstable and the opening power was also inconsistent.

[Brief explanation of the drawing]

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

Claims (1)

[Claims] On at least one side of layer A made of polyolefin resin, one type selected from styrene resin, methacrylic acid ester resin, methylpentene resin, saturated polyester resin, and polyamide resin is added to 100 parts by weight of polyolefin resin (a). A film laminated with a layer B formed by mixing 15 to 45 parts by weight of the above resin (B), wherein the T of the layer B is
The average dispersion diameter (b value) of the resin (b) in cross section D is 0
．． 2 to 10 μm, and the thickness of the layer B is 3 to 25 μm
m, an easily cleavable laminated film having an overall thickness of 15 to 350 μm.