JPH03213335A - Laminated film for packaging - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a laminated film for packaging, and more specifically, a laminated film for packaging that does not lose its gas barrier properties even when subjected to hot water treatment, is transparent, and is inexpensive. This invention relates to a laminated film for packaging.

In the present invention, packaging is a concept that includes both primary packaging in which the contents are directly packaged and secondary packaging in which the contents are stored in a plastic bag or container and the bag or container is further packaged. be.

[Conventional technology and issues to be solved]

The gas barrier properties of packaging films after hot water (high pressure steam) treatment are important in the food and medical fields.

For example, when packaging retort food, the food is stored in a packaging bag made of a film with high gas barrier properties and subjected to retort processing, but the gas barrier properties of the packaging film may be impaired during or after retort processing. Food cannot be stored for a long time, and the original purpose of packaging is lost.

Furthermore, in general, when packaging medical liquids such as physiological saline and Ringer's solution, they are stored in a plastic container as a primary packaging product, and this primary packaging product is placed in an autoclave, for example, and then heated with hot water. A method of sterilizing the product by leaving it under high-pressure steam for about 30 minutes has been adopted. In this case, the container is not handled in its naked state, and the subsequent secondary packaging is performed under sterile conditions, but this process is complicated and undesirable, so packaging materials such as plastic sheets are used. In some cases, a primary packaged product is packaged in a secondary package and then directly sterilized in this packaged state.

In the secondary packaging film in such a case, the gas barrier properties, particularly the oxygen gas barrier properties, of the packaging film during and after the sterilization treatment are important, as described above.

Aluminum foil has traditionally been used as a packaging material that can be treated with hot water and has excellent gas barrier properties.Although such packaging materials have excellent hot water resistance and gas barrier properties, It has the disadvantage that it cannot be seen from the outside and is expensive.

In addition, inexpensive packaging materials that can be treated with hot water and have excellent transparency include polyester, polyamide, and polyvinylidene chloride, all of which have better gas barrier properties than aluminum foil. It has the disadvantage of being low. On the other hand, although resins such as saponified ethylene-vinyl acetate copolymers have high gas barrier properties, they are highly dependent on humidity, and their oxygen permeability tends to increase significantly in high humidity regions.

Therefore, the gas barrier properties of the packaging structure are generally maintained by covering and laminating a protective layer such as polyethylene with low water absorption. However, under high-humidity, high-temperature conditions such as during retort processing, the water absorption rate of the polyethylene itself that protects the gas barrier resin layer increases, and the moisture that has permeated through the protective layer transfers to the gas barrier resin layer. However, there is a drawback that the gas barrier properties as a packaging film are significantly impaired.

Furthermore, recently, on the surface of plastic film,
A retort made by laminating a film with one or more dry brating layers of silicon or silicon oxide, and printing thereon as necessary, and a polyolefin film via a polyurethane adhesive. A packaging material for pouches has been proposed (Japanese Patent Application Laid-Open No. 103139/1983). However, this packaging material has the disadvantage that it has insufficient gas barrier performance after hot water treatment and cannot be used for contents that require a high degree of gas barrier property.

[Means to solve the problem]

In view of the above circumstances, the inventors of the present invention have conducted intensive studies and found that if a specific film having a silicon oxide thin film on its surface is to be bonded and protected, hot water (high pressure steam) treatment is necessary. The present invention has been completed based on the finding that the gas barrier properties are maintained at a high level without being impaired even when exposed to heat.

That is, the gist of the present invention is as follows:
Consisting of a layer (A), a second layer (B) and a third layer (C), the second layer is bonded to one surface of the first layer, and the third layer is bonded to the other surface of the second layer. The present invention relates to a laminated packaging film characterized by:

(a) The first layer (A) is a transparent laminated plastic film having a transparent silicon oxide thin film on at least one side of a transparent plastic film with a shrinkage rate of 1% or less after hot water treatment at 120°C for 30 minutes. (It consists of a transparent film containing layers.)

(b) The second layer (B) has a shrinkage rate of 1% or less after hot water treatment at 120°C for 30 minutes, and conforms to JIS Z0208.
It is made of a transparent plastic film with a measured moisture permeability of 60 g/m'·24H or less at 40° C. and 90% RH.

(C) The third layer (C) is made of a heat-sealable transparent plastic film having a tack strength of 10 g/15 mm or less after hot water treatment at 120° C. for 30 minutes.

[Effect]

The silicon oxide thin film of the first layer (A) exhibits high gas barrier properties. Due to its low shrinkage properties, the transparent plastic film of the first layer (A) does not shrink significantly during hot water treatment, and as a result, does not cause cracks or the like to the silicon oxide thin film formed on its surface. .

The transparent plastic film of the second layer (B) exhibits the same effect as above due to its low shrinkage property, and also protects the silicon oxide thin film from water during hot water treatment due to its moisture permeability resistance.

The transparent plastic film of the third layer (C) prevents the films from sticking to each other due to its low tack strength, maintains a beautiful appearance, and facilitates handling.

The present invention will be explained in detail below.

The laminated film for packaging of the present invention consists of a first layer (A), a second layer (B) and a third layer (C) defined as above, and one side of the first layer (A) The second layer (B) is formed by joining the third layer (C) to the other surface.

First, each of the above layers will be explained in order.

(1) First layer (A) In the packaging laminated film according to the present invention, the first layer (A
) is a transparent laminated plastic film having a transparent silicon oxide thin film (hereinafter abbreviated as "SO thin film") on at least one side of a transparent plastic film having a shrinkage rate of 1% or less after hot water treatment at 120°C for 30 minutes. It consists of a transparent film containing at least one layer of.

The above-mentioned low-shrinkage transparent plastic film is not particularly limited, and various transparent plastic films can be used.Of course, unstretched films can be used, but stretched films are used from the viewpoint of mechanical strength, etc., and typically, A balanced type biaxially oriented polyester film is used.

Biaxially oriented polyester film has excellent not only mechanical strength but also heat resistance and transparency, and due to the beat setting after stretching and the subsequent longitudinal and lateral relaxation, it is mainly used in various grades for electrical applications. Shrink films are commercially available. Furthermore, even if the film is of ordinary grade, it can be left in a heating oven at around 200° C. for several hours to sufficiently shrink before use.

Note that the shrinkage rate after hot water treatment at 120° C. for 30 minutes in the present invention means the shrinkage rate in the vertical and horizontal directions (area shrinkage rate).

SO formed on the surface of low shrinkage transparent plastic film
The thin film may be formed on only one side of the film or on both sides.

The SO thin film can be formed using -silicon oxide, silicon dioxide, a mixture thereof, or the like as a deposition raw material, and can be performed by any one of a vacuum evaporation method, a sputtering method, and an ion blating method. In addition, silicon, silicon oxide, silicon dioxide, or
It is also possible to employ a reactive vapor deposition method using a mixture thereof while supplying oxygen gas.

Prior to forming the SO thin film, it is also possible to use an anchor coating agent in order to increase the adhesive strength between the thin films. Suitable anchor coating agents include adhesion promoters such as isocyanate-based, polyethyleneimine-based, and organic titanium-based adhesives, and adhesives such as polyurethane-polyester-based adhesives. Further, as the anchor coating agent, a solvent-free type adhesive such as polyethylene, polyester, or polyamide may be used.

Furthermore, if the SO thin film is 10% by weight or less, even if it contains impurities such as calcium, magnesium, or their oxides, the gas barrier performance of the intended packaging film will not be significantly reduced. do not have.

The thickness of the SO thin film is preferably selected in the range of 100 to 5000. If the thickness of the SO thin film is less than 100, the gas barrier performance will be insufficient, and if it exceeds 5,000, the film may curl, causing problems, or the transparent thin film itself may crack or peel. I don't like it because it's easy.

Note that this first layer (A) is a monolayer body consisting of one transparent laminated film having a transparent SO thin film on one side of the low-shrinkage transparent plastic film, or two or more transparent laminated films are bonded together with a transparent adhesive. The laminate may be either a laminate bonded using a transparent adhesive or a laminate formed by bonding a transparent laminate film and a transparent plastic film using a transparent adhesive. Examples of adhesives that can be used in this case include urethane-based, acrylic-based, and polyester-based adhesives.

(2) Second layer (B) In the present invention, the second layer (B) is bonded to one surface of the first layer (A), preferably to the surface on the SO thin film side.

The second layer (B) functions as a protective layer and is
Shrinkage rate after hot water treatment is 1% or less, JIS Z
It is made of a transparent plastic film with a measured moisture permeability of 60 g/m·24H or less at 40° C. and 90% RH in accordance with 020B.

Such a transparent plastic film consists of the first layer (A)
As in the case of , various transparent plastic films can be used without any particular restriction, but from the viewpoint of hot water shrinkage rate etc.
The biaxially oriented polyester film selected as the transparent plastic film for layer (A) has a sufficiently low moisture permeability, so that even in the second layer (B),
A biaxially oriented polyester film similar to the above is preferably used. Of course, like the first layer (A), unstretched films can also be used, such as polypropylene films, such as "FHX" manufactured by Nisho Kagaku Co., Ltd.
(General grade) is the second layer (B) of the present invention as it is.
It can be used as a transparent plastic film for.

The moisture permeability of the second layer (B) also varies depending on the thickness of the film used, so the thickness is appropriately determined in conjunction with the type of plastic.

Note that the definition of the thermal shrinkage rate in the second layer (B) is the same as in the case of the first layer (A).

(3) Third layer (C) In the present invention, a third layer (
C) is joined.

The third layer (C) acts as a sealant and
Tack strength after 130 minutes hot water treatment is 10g/15m
It is made of a transparent plastic film that is less than m and can be heat-sealed.

The tack strength in the present invention means the tack (adhesion) strength of the third layer (C). Since tack strength is determined by heat resistance, the third layer (C) must be a transparent plastic film that has high heat resistance and can be heat-sealed.

A typical example of a transparent plastic film suitable for such a purpose is a heat-resistant grade unstretched polypropylene film.

Various types of heat-resistant grade polypropylene films are commercially available, and for example, 'RXC-7'' and 'RXC-11'' manufactured by Tokyo Cellophane Co., Ltd. can be suitably used. Further, even if a transparent plastic film originally has high tack strength, a film whose tack strength is reduced by roughening the surface can be similarly used.

Next, a laminated structure in which the respective layers are bonded together will be explained.

When bonding the second layer (B) and the third layer (C) to the first layer (A) surface, urethane adhesive, acrylic adhesive,
A known method such as a dry lamination method using a polyester adhesive or an extrusion lamination method can be employed. Moreover, the order of stacking the third layer (C) may be before or after the formation of the SO thin film of the first layer (A).

In addition to the above, the third layer (C) can also be provided on the first layer (A), preferably on the low-shrinkage transparent plastic film surface, by extrusion coating without using an adhesive.

Depending on the contents to be packaged, in addition to gas barrier performance, the packaging film also requires UV blocking ability.
The packaging film according to the present invention can be provided with ultraviolet blocking performance as required.

For example, a packaging film having ultraviolet blocking ability can be obtained by adding a substance having ultraviolet absorbing ability to the adhesive layer when bonding the above-mentioned layers. The ultraviolet absorber used may be one or a combination of commercially available benzophenone, benzotriazole, etc., and the amount of the ultraviolet absorber to be used is determined depending on the required ultraviolet absorbing ability. In addition, the ultraviolet blocking ability is determined by layer (A)
-(C) It goes without saying that this can also be imparted by using a film containing a substance having ultraviolet absorbing ability.

In the packaging laminated film according to the present invention, the second layer (
The total thickness of B) and the third layer (C) is preferably in the range of 5 to 400 μm, and the overall thickness is preferably in the range of 50 to 500 μm from the viewpoint of strength, flexibility, economical efficiency, etc.
More preferably, the thickness is 100 to 300 μm. Thickness ratio of each layer excluding adhesive layer (A): (B):
(C) preferably has a ratio of l:1 to lO:1 to 10.

In addition, between the first layer (A) and the second layer (B), or between the first layer (A) and the second layer (B),
Between the layer and the third layer (C), for overall thickness adjustment,
A transparent plastic film can also be interposed. The plastic film to be interposed is not particularly limited as long as it is transparent, but the same type of plastic film as the plastic film forming the second layer (B) is preferably used. The thickness of the intervening plastic film is selected in relation to the thickness of the entire laminated film.

The laminated film for packaging of the present invention is used with the second layer (B) positioned so as to be exposed on the surface.
It can be suitably used for any of the following packaging applications. especially,
When used for secondary packaging, it has excellent gas barrier properties and low tack strength properties of the third layer (C) that functions as a sealant, resulting in excellent peelability from the secondary packaging container, and therefore good handling. be.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless the gist thereof is exceeded.

In addition, in the following examples, each physical property value etc. was measured by the following method. Further, the thickness of the transparent thin film layer of silicon oxide was measured using a quartz crystal film thickness meter.

(1) Hot water shrinkage rate (%): Cut a 100Mφ sample from the film, heat it in hot water at 120°C for 30 minutes in an autoclave, take it out, measure the outer diameter at 10 points, and calculate the minimum value as DM+
Let it be n. The hot water shrinkage rate is calculated from the following formula.

(2) Moisture permeability of film (gr/m'・24H)
: Compliant with JIS Z 0208 Create a 10100 x 100 three-sided sealed bag from the specified film, fill the bag with granular anhydrous calcium chloride 30g as a moisture absorbent, and then seal the remaining side to prepare the sample. shall be.

Ten samples were each placed in an atmosphere of 40° C. and 90% RH1, and the moisture permeability of the film was determined from the change in weight.

(3) Tack strength (g/15mm): A sample with an opening size of 140 x 140 mm was cut out from the film, heat-sealed on three sides, and then vacuum-sealed on the remaining side to create a bag with an inner size of 120 to 120 bags. This bag was autoclaved in hot water at 120℃ for 3
After heating for 0 minutes, it was taken out and the sealed portions on four sides were cut off to obtain a 120 x 120 mm sample consisting of two overlapping films. From this sample 15nunX120m
A tanzak-shaped sample of m was cut out, and the adhesive strength of the two films was measured.

(4) Oxygen permeability = (cc/I・24H-atm) Using Modern Control's 0X-TRAN100 type oxygen permeability measuring device, temperature: 30°C, relative humidity: 80%
Measured under the following conditions.

Note that the oxygen permeability was measured before and after measuring the hot water shrinkage rate.

(5) Transparency of film (%): The light transmittance of the film in visible light was measured using a spectrophotometer newly manufactured by Hitachi, and the light transmittance at 550 nm was defined as the transparency of the film.

(6) Peelability: In the measurement of tack strength, the peelability of a sample consisting of two overlapping films was evaluated, and those that could be peeled off smoothly were marked with a circle, and those that were difficult to peel were marked with an x.

In the example, an axially stretched polyethylene terephthalate film (stretching ratio 3 x 3 times, thickness 12μ, hot water shrinkage rate 0.9%) was supplied to a vacuum evaporation apparatus, and heated under a vacuum of 5 x 10-5 Torr using an electron beam heating method. Silicon monoxide with a purity of 99.9% was heated and evaporated to obtain a transparent laminated plastic film in which a transparent thin film layer of 1000 silicon oxide was formed on one side of the film (first layer). The same biaxially stretched polyethylene terephthalate film (moisture permeability 60gr/rri'・24H) as above was placed on the silicon oxide thin film side of the obtained film.
r (second layer)" were laminated via a urethane adhesive (a two-component adhesive with a ratio of 9:1 of Takelac A606 and Takenate A-10 manufactured by Ota Pharmaceutical Co., Ltd.) (thickness 2μ),
Furthermore, on the opposite side of this layer, an unstretched polypropylene film (thickness 50μ, tack strength 8gr/15mm) was applied as a sealant layer using the same urethane adhesive as above.
(Third layer) was laminated to obtain a three-layer transparent plastic film.

The various physical properties of the obtained laminated film were measured, and the results are shown in Table 1.

In addition, as Examples 2 to 6 and Comparative Examples 1 to 6, laminated films were prepared in the same manner as in Example 1, except that the type, thickness, and number of transparent films in each layer were changed as shown in Table 1. Table 1 shows the measurement results of the physical properties of each laminated film (however, the measurement results of light transmittance were 83
% or more and had sufficient transparency, Table 1
The description inside is omitted).

Example 3 using two films as the first layer (A)
Two transparent laminated plastic films of Example 1 in which a transparent thin film layer of silicon oxide was formed on one side of the film were used, and the other transparent laminated plastic film was placed on the silicon oxide thin film side of one transparent laminated plastic film. A laminate in which the film sides of the two are bonded together using a urethane adhesive is used as the first layer (A).

In addition, the meaning of each abbreviation in Table-1 is as follows.

[PET] Biaxially stretched polyethylene terephthalate film (stretching ratio 3x3) [Heat-resistant CPP] Unstretched polypropylene film (heat-resistant grade) [General CPP] Unstretched polypropylene film (general grade) [ON
Y] Biaxially oriented nylon-6 film (stretching ratio 3 x 3 times) COPP] Biaxially oriented polypropylene film (stretching ratio 3 x 3 times) (hereinafter referred to as margin) [Effects of the invention] Packaging laminate of the present invention as described above The film maintains its original excellent gas barrier properties even when subjected to hot water (high pressure steam) treatment, is transparent and inexpensive, and also has good peelability, which is important when used for secondary packaging.

Therefore, the packaging film of the present invention has great value as a packaging film for contents that require hot water treatment (retort treatment, sterilization treatment) in the food, medical, and other fields.

Applicant Mitsubishi Monsanto Chemicals Co., Ltd. Agent
Patent Attorney Oka 1) Kazuhiko

Claims (3)

[Claims] (1) First layer (A) and second layer (B) defined as below.
) and a third layer (C), with a second layer on one side of the first layer.
A laminated film for packaging, characterized in that the layers are bonded, and a third layer is bonded to the other side of the first layer. (a) The first layer (A) is a transparent laminated plastic film having a transparent silicon oxide thin film on at least one side of a transparent plastic film with a shrinkage rate of 1% or less after hot water treatment at 120°C for 30 minutes. It consists of a transparent film containing one layer. (b) The second layer (B) has a shrinkage rate of 1% or less after hot water treatment at 120°C for 30 minutes, and a moisture permeability measurement value of 60g at 40°C and 90% RH in accordance with JIS Z0208. /
Made of transparent plastic film with a thickness of m^2.24H or less. (C) The third layer (C) is made of a heat-sealable transparent plastic film that has a tack strength of 10 g/15 mm or less after hot water treatment at 120° C. for 30 minutes. (2) The laminated film for packaging according to claim 1, wherein the second layer (B) is bonded to the silicon oxide thin film side surface of the first layer (A). (3) The thickness of the silicon oxide thin film of the first layer (A) is 100
The laminated film for packaging according to claim 1 or 2, characterized in that the thickness is in the range of 5,000 Å.