JPS6259037A - Heat-shrinkable laminated packaging material - 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 (Industrial Application Field) The present invention relates to improvements in heat-shrinkable laminated packaging materials having heat sealability.

(Prior Art) Heat-shrinkable plastic films such as polyolefin films and polyamide films are widely used as heat-shrinkable packaging materials for foods and other products. Depending on the type of product being packaged, the packaging material must have properties such as pinhole resistance, cold resistance, and gas barrier properties, so in such cases, two-wheel stretched nylon film is used as the heat-shrinkable base film. However, because nylon films tend to stretch easily and have poor gas barrier properties due to moisture absorption, a film with moisture-proof sealant films laminated on both sides of this base film is used. . When heat-shrink packaging foods, etc., the items to be packaged are generally filled into bags made of heat-shrinkable packaging materials that have been made in advance using the gassho pasting method, tape sealing method, envelope pasting method, etc., are degassed, and then heated. After sealing, the package is heat-shrinked in hot air or hot water to form a tight-fitting package.

Examples of heat-shrinkable laminated packaging materials having such P1-seal properties are those disclosed in Japanese Patent Publication No. 58-47986 and Japanese Patent Application Laid-Open No. 54-15981.

(Problem to be Solved by the Invention) However, such multilayer films are either a heat-shrinkable base film laminated with a sealant film that has almost no heat shrinkage on one or both sides, or a base film with a sealant film laminated on one or both sides of the base film. After the films were laminated, they were stretched. In such multilayer films, the sealant layer has poor heat shrinkability, so it is difficult to obtain a sufficient heat shrinkage rate during heat shrink packaging, which tends to create voids inside the tightly packed package, resulting in tight packaging. Not only does the lack of adhesive properties impair the appearance, but also condensation forms in the voids, causing bacterial growth. Even if heat absorption 3i1 treatment is performed at a higher temperature condition to compensate for the above-mentioned drawbacks, not only is it still not possible to obtain a satisfactory finished appearance, but depending on the type of the packaged items, the heat during shrink wrapping may damage the packaged items. This may result in quality deterioration.

In addition, when shrink wrapping is attempted using a multilayer film in which a heat-shrinkable sealant film is laminated on only one side of a heat-shrinkable base film, the heat-sealed portion must be pasted with the palms of hands together, and a certain amount of heat is applied. In order to obtain seal strength, it is necessary to increase the thickness of the sealant film or widen the seal width, which poses the problem that the seal portion becomes unsightly.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides heat-shrinkable laminated packaging having heat-sealability, which is formed by laminating heat-shrinkable sealant films on both sides of a heat-shrinkable base film. The material provides a satisfactory finished appearance during heat shrink packaging.

The heat-shrinkable base film used in the present invention is stretched in the longitudinal and transverse directions at a stretching ratio of 1.5 to 7.0 times, and has a hot water shrinkage rate of 15 to 5 at 95°C.
0%, preferably 20-50% heat shrinkable films are used, such as nylon 6, nylon 6-6, nylon 6-10, nylon 6-6/6 copolymer, nylon 6
-12, polyamide resins such as nylon 11 and nylon 12, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyvinyl chloride resins, polyac IJ Cl nitrile resins, polystyrene resins, polyolefin resins such as polypropylene,
A polyvinyl alcohol resin, an ethylene/vinyl acetate copolymer (hereinafter referred to as EVOH), a mixture thereof, or a resin containing these as main components is formed into a film, and this is formed into a film by at least one film in each of the vertical and horizontal directions. Biaxially stretched to .5 times, preferably 1.5 to 7.0 times, 9
The hot water shrinkage rate at 5°C is 15-50%, preferably 2
Examples include films that have been given heat shrinkability of 0 to 50%, but are not limited to these films. Further, these films may be provided with a coating layer or a printed layer of polyvinylidene chloride resin, EV OH resin, or the like.

The heat-shrinkable sealant film used in the present invention may be any heat-shrinkable sealant film having a melting point lower than that of the heat-shrinkable base film, such as linear low-density polyethylene film (hereinafter referred to as L-LDP).
E-film), low-density polyethylene film (referred to as
(hereinafter referred to as LDPE film), polypropylene film, ionomer resin, a mixture of these resins, or a resin that is a blend of these resins with a small amount of other polymers such as polyester elastomer or ethylene vinyl acetate copolymer resin. The film is stretched by at least 1°5 times, preferably 1°, in each of the machine and transverse directions.
．． Examples include films with heat sealability that are biaxially stretched 5 to 7.0 times and have a hot water shrinkage rate of 10 to 50% at 95°C, more preferably 15 to 50%; A material having heat shrinkability comparable to that of the base film is more preferably used. Also, L-LDPE
A heat-shrinkable sealant film made of the following is particularly preferable because it has excellent pinhole resistance and heat-sealing strength.

The heat-shrinkable base film used in the present invention usually has a
It has a thickness of 0 μm, and in practical terms it is 10 to 35 μm.
It is preferable to have a thickness of . In addition, sealant films with a thickness of 10 to 50 μm are normally used, but since the sealant film according to the present invention is laminated on both sides of the base film, the heat-sealed part must be attached to an envelope. Therefore, the thickness of the sealant film may be relatively thin, even if it is 10 to 30 μm, it can be suitably used.

The type and thickness of the sealant film will depend on the type and capacity of the packaged items, such as pinhole resistance, gas barrier properties,
It is appropriately selected in consideration of the performance required as a packaging material such as heat seal strength and the characteristics of the base film used, and is not limited to the above range.

The heat-shrinkable laminated packaging material according to the present invention can be obtained by laminating the heat-shrinkable base film and the heat-shrinkable sealant film by a conventional laminating method, such as extrusion lamination or tri-lamination.

The extrusion lamination is a method in which a thermoplastic resin that can be formed into a film by melt extrusion is extruded through a thin slit of a T-die of an extruder and laminated on a base film.
This method involves cooling and solidifying. The dry lamination is a method in which an organic solvent-based adhesive such as a urethane adhesive is applied to a base film, the solvent is evaporated and removed by drying, and then a sealant film is laminated by heating and pressure bonding.

The processing conditions during the lamination are appropriately selected depending on the combination of the base film and sealant film to be laminated.

(Functions and Effects) The heat-shrinkable laminated packaging material according to the present invention obtained as described above can be heat-sealed in the sealant layer, and a sealant film with excellent heat-shrinkability is laminated thereon. It has excellent heat shrinkability without impairing the heat shrinkability of the material film. Furthermore, since the laminated packaging material of the present invention has a heat-shrinkable sealant film with excellent heat-sealability laminated on both sides of the base film, it can be made into bags by an envelope pasting method, etc. A beautiful close-fitting package can be obtained.

In particular, when the heat-shrinkable base film is a heat-shrinkable nylon-based film and L-LDPE-based sealant films are laminated on both sides of this film, pinhole resistance,
It is an extremely superior heat-shrinkable packaging material that has excellent cold resistance and gas barrier properties, and is almost unaffected by outside air humidity.
Furthermore, since the L-LDPE sealant film has excellent heat sealing strength, it is possible to reduce the thickness of the sealant layer and narrow the overlap width during lap sealing, resulting in a beautiful appearance of the sealed part. be. Therefore, the packaging material according to the present invention is suitable for shrink-wrapping meat packages, cheese, and various other articles.

In addition, the laminated packaging material according to the present invention is a lamination of a base film and a sealant film, each of which has been made heat-shrinkable by stretching, and can be laminated with the printed side inside, so both materials can be co-extruded. Compared to the case where the printing is laminated and then stretched, the appearance of the printing is better, and it is advantageous in that the printed surface can be prevented from peeling off or falling off due to friction, oil, water, etc.

Furthermore, a single film has simpler manufacturing equipment and easier quality control than a multilayer film produced by coextrusion, making it suitable for mass production. Another advantage of this method is that it is possible to easily obtain laminated packaging materials with predetermined properties such as heat shrinkability, barrier properties, heat sealability, and puncture resistance as needed. Practically superior to those with shrinkage properties.

(Examples) Next, the present invention will be specifically explained using Examples, but the present invention is not limited thereto.

In addition, the measuring method of the main characteristics measured in the present invention is as follows.

Hot water shrinkage rate: Cut the packaging material to be measured into approximately 2Qcm x 20 marks, condition the humidity at 20°C, 165% RH for 24 hours, and then accurately measure the longitudinal and lateral dimensions of the film (measurement Let the value be A). This sample was completely immersed in hot water at 95°C for 10 seconds (however, for nylon films with sealant laminated on both sides, 100°C for 5 minutes), taken out, and the moisture adhering to the surface of the sample was removed with filter paper. ,
The film was left at 20° C. and 65% RH for 24 hours, and the longitudinal and transverse dimensions of the film were accurately measured (the measured values were designated as B). Calculation of the hot water shrinkage rate is performed in the following 2.

Hot water shrinkage rate (%) - (A-B/A) x 100 Heat seal strength: A sample of the packaging material to be measured was conditioned at 20°C and 65% RH for 24 hours and cut into 25mm x 300mm pieces. Place the sealant films on top of each other so that they face each other, and seal this sample using a bar sealer with a cylinder diameter of 5011φ, size 101 width x 300 dragon length, set at a predetermined temperature, at a gauge pressure of 1 kg/cI11 and a sealing time of 1 second. Humidity conditioned for 24 hours at 20゛C165%RH and width 1
5. Sampling to self. Each sample was pulled from the inside of the seal, and then attached to the Tensilon chuck and pulled at a speed of 300 mm/min.
The strength is read by Tensilon's chart.

Pinhole resistance: Pinhole resistance is expressed as puncture resistance. The film was fixed in a frame with an inner diameter of 60 mm, and a hemispherical needle tip with a radius of curvature of 0.5 m was applied perpendicularly to the film surface at the center of this circle at a speed of 50 ± 5 mm/min. The maximum resistance force that can be applied until it breaks is expressed in kg.

Oxygen gas barrier property: Oxygen gas barrier property is ASTM
It is expressed as the oxygen gas permeability measured by MOCON (OX-TRAN100 type oxygen gas permeability measuring device) manufactured by Modern Controls, Inc. in the United States in accordance with D-1434.

Measurement conditions DRY: Measured in a dry state after leaving the sample in a desiccator for 24 hours or more WET: Measured in a wet state after immersed in water for 24 hours Example 1 Nylon 6 with a thickness of 15 μm that was simultaneously biaxially stretched (Second The heat-shrinkable film shown in Table-(A)) was simultaneously biaxially stretched as a heat-shrinkable sealant on both sides with a specific gravity of 0.92 and a thickness of 15μ.
One side corona treatment of m (wetting tension 40 dynes/cm)
heat-shrinkable linear low-density polyethylene (hereinafter referred to as L-L
The corona-treated surfaces of the films (abbreviated as DPE) (Table 2-(F)) were placed facing each other, and the laminating adhesive AI)-503/CA'1 manufactured by Toyo Morton Co., Ltd. was applied.
Using lO=90/10, 3 and 70゛C, respectively.
After dry laminating and aging at 35 to 40°C for 2 days, the physical properties were evaluated and the results are shown in Table 1.

Using the obtained laminated film, a round-bottom bag with a length of 300 mm and a folded diameter of 165 mm was made by sealing the bottom with a round seal with a lamp width of 2 ms. After filling and deaerating the irregularly shaped roast ham of size 25 CI11, the opening was sealed with a flat seal with a seal width of 2 ms, followed by a hot water shower treatment at 95°C for 5 minutes, followed by a further 10 minutes at 90°C. A heat bath treatment was performed. As a result, although the contents were amorphous, the laminated film part of the bag adhered extremely tightly and did not form any voids, so there was no condensation and the appearance was extremely beautiful. Comparative Example 1 Heat Specific gravity 0.0 as a sealant instead of shrinkable sealant.
92, unstretched L-LDPE film (trade name: Kojin L-Ace, manufactured by Kyokojin, Table 2-(■)) with a thickness of 15 μm and corona treatment on one side (wetting tension 40 dynes/cm). A double-sided heat-sealable heat-shrinkable packaging material was produced in exactly the same manner as in Example 1, except that the material was used.The physical properties thereof were evaluated, and the results are shown in Table 1.

As is clear from the results of Example 1 and Comparative Example 1 above, the product in which biaxially stretched heat-shrinkable sealant films are laminated on both sides has better hot water shrinkage than the product in which non-shrinkable sealant films are laminated. It was significantly higher.

Example 2 A polyamide copolymer with a weight ratio of nylon 6/nylon 6-6 of 85/15 (trade name Nippa Mid, Mitsubishi Kasei (+
extruded into a tube at 250-260℃ using
A tubular unstretched film having a diameter of 66 mm and a thickness of 14.5 μm was obtained. This unstretched film was simultaneously biaxially stretched at 75 to 80°C using a tubular stretching method, and after unfolding, it was heat-set at 150°C for 10 seconds using a tenter, and the film was heated to a thickness of 15.5 μm. A shrinkable film was obtained. The heat shrinkage rate of this film is shown in Table 2 (B).

A heat-shrinkable L-LDPE sealant film (trade name: Kojin BO-LS, manufactured by Koshiiri, Table 2-(F)) was laminated on both sides of this heat-shrinkable film in the same manner as in Example 1. The physical properties of the laminated packaging material obtained were evaluated, and the results are shown in Table 1.

Comparative Example 2 An unstretched L-LDPE film (trade name: Kojin L-Ace, manufactured by Koshiiri, Table 2) was used as a sealant film.
A double-sided laminated packaging material was produced in exactly the same manner as in Example 2, except that (ii))) was used. The physical properties were evaluated and the results are shown in Table 1.

As can be seen from the results of Example 2 and Comparative Example 2 above, even if the same heat-shrinkable film is used as the base material, if the sealant film laminated on both sides is not heat-shrinkable, the heat-shrinkability of the laminated film will be However, in the case of a laminated heat-shrinkable sealant film, the heat-shrinkability decreased only slightly.

Example 3 Simultaneous biaxial stretching as a heat-shrinkable sealant with a thickness of 15μ
heat-shrinkable polypropylene film (product name: KOHJIN) with single-sided corona treatment (wetting tension 40 dynes/cm)
A laminated packaging material was prepared in exactly the same manner as in Example 1, except that KORAP, manufactured by 11 Kojin, Table 2-(G)) was used, and its physical properties were evaluated, and the results are shown in Table 1. . As described above, it was found that a heat-shrinkable film in which a heat-shrinkable sealant was laminated on both sides exhibited excellent heat-shrinkability even if the heat-shrinkable sealant was a polypropylene film.

Example 4 Biaxially oriented heat-shrinkable polypropylene film with a thickness of 20 μm (product name: KOHJIN KORAP, manufactured by ■Koshiiri)
Corona treatment is applied to both sides and the wet tension is 39 dynes/cm.
), a small polka dot pattern was gravure printed on one side using blue ink for polypropylene, and a biaxially stretched heat-shrinkable L-LDPE film (product name: Kojin B O-LS, The corona-treated surfaces (wet tension: 40 dynes/cm) of f411 Kojin Co., Ltd. (Table 2-(F)) were laminated using the same dry laminating adhesive as in Example 1, and heated to a room temperature of 40°C. It was left for 2 days. There were no particular problems during printing. The properties of the obtained laminated packaging material are shown in Table 1. This laminated packaging material was made into a cylinder using an automatic bag-making machine with a lamp seal with a wrap width of 2 mm, and the bottom was sealed with a round seal with a seal width of 2 mm to form a cylinder with a length of 300 mm and a folded diameter of 165 mm. Although the bag was made, no particular trouble occurred.

As mentioned above, the laminated packaging material of this example not only had excellent heat shrinkability and pinhole resistance (but also had sufficient printability and bag-making processing suitability. The reason for this is that the polypropylene base material This seems to be due to the synergistic effect of the heat shrinkability and good workability of the layer and the heat shrinkability and pinhole resistance of the sealant layer.

Comparative Example 3 Simultaneously biaxially stretched as a sealant, specific gravity 0.92, thickness 30 mm, one side corona treated surface (wetting tension 40 dynes/
A laminated film was produced in exactly the same manner as in Example 1, except that a heat-processable L-LDPR film (trade name: Kojin BO-LS, Table 2-(E)) of ca+) was laminated only on one side.

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

As can be seen from this result, the heat shrinkability of the obtained laminated shrinkable film is not much different from that of the heat-shrinkable L-LDPE film laminated on both sides (Example 1), but since it is laminated on one side, This is a gassho pasting method, and the seal strength is significantly lower than that of a double-sided laminated product (envelope pasting). In addition, the gas barrier properties had a drawback that under wet conditions, the nylon layer absorbed moisture, resulting in a significantly high gas permeability.

Reference Example 1 A heat-shrinkable polyester film (trade name: Diaboil, thickness 12 μm, made on the Diafoil side, Table 2-(D)) was used as a heat-shrinkable film, and a sealant layer with a thickness of 3
0 μm biaxially stretched LDPE film (Table 2-(H))
A laminated film was produced by laminating only on one side in the same manner as in Example 1. The physical properties of the obtained film were measured and the results are shown in Table 1.

Reference example 2 Melting point: 111.5°C Density at 125°C: 0.920
low-density polyethylene (product name: UBE IIFO)
19. Ube Industries (+ unmanufactured) at 200 to 250°C, and separately polyethylene terephthalate with an intrinsic viscosity of 0.7.
Each was heated and melted in an extruder at 87°C, and the slit diameter was 7.
5 The inner side of the two-layer annular die of Tsuru is a polyethylene terephthalate layer, and the ratio of the thickness of the inner and outer layers is 1;
The inside of the film is indirectly cooled with water by extruding it so that the inside of the film is directly below the die and sliding it over an internal mandrel with a diameter of 66111 which is cooled with 30°C water.At the same time, the outside of the mandrel part is The film was cooled from the outer surface by blowing cold air at a higher speed to obtain a laminated unstretched film having a diameter of 66 mm, a thickness of 234 μm, and a polyethylene terephthalate portion having a crystallinity of 18%. This unstretched film was simultaneously stretched in two wheels by the tubular method. The stretching conditions were based on the biaxial stretching conditions of polyethylene terephthalate, first preheated to 70°C with hot air, then the temperature at the starting point of stretching was 107°C, and the first 1/3 section of the stretching zone was 105 to 108°C. After finishing the stretching by making the subsequent section a continuous descending slope from 104 to 75 °C, it was cooled at room temperature, and the diameter was 200 mm and the thickness was 41 mm.
A biaxially stretched laminated film of μm was obtained and further heated to 80°C for 10
Heat fixation was performed for seconds. The properties of this laminated film were evaluated and shown in Table 1. As can be seen from the results of Reference Example 1 and Reference Example 2, the heat shrinkability of the film of Reference Example 2 that was stretched after coextrusion was different from that of the film that was laminated after stretching the heat-shrinkable film layer and the sealant film layer separately. The ratio was considerably lower than that of the film of Reference Example 1, and a phenomenon in which the film curled significantly in the direction of the polyethylene terephthalate layer was observed when it was heat-shrinked. From these phenomena, the polyethylene layer serving as the sealant layer was stretched together with the polyethylene terephthalate layer, but it had almost no residual shrinkage, so it seems that the original shrinkage force of the polyethylene terephthalate layer was reduced.

(Effects of the Invention) As explained above, according to the present invention, heat-shrinkable sealant films are laminated on both sides of a heat-shrinkable base film, which provides excellent heat-shrinkability and heat-sealability. A laminated packaging material can be obtained.

(Hereafter, margin)

Claims (4)

[Claims] (1) A heat-shrinkable laminated packaging material having heat-sealability, which is formed by laminating heat-shrinkable sealant films on both sides of a heat-shrinkable base film. (2) The heat-shrinkable sealant film is a polyolefin film that has a melting point lower than that of the heat-shrinkable base film and has a heat shrinkage rate of 10 to 50% in the longitudinal direction and the transverse direction, respectively. A heat-shrinkable laminated packaging material according to claim 1. (3) The heat-shrinkable base film is a polyamide-based film or a polypropylene-based film having a heat shrinkage rate of 15 to 50% in the longitudinal direction and in the lateral direction, respectively, according to claim 1. heat-shrinkable laminated packaging material. (4) Claim 1, wherein the heat-shrinkable base film is made of a biaxially stretched polyamide film, and the heat-shrinkable sealant film is made of a biaxially stretched linear low-density polyethylene film. Heat-shrinkable laminated packaging material described in Section 1.