JPH047700B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a laminated shrink packaging material that is made heat shrinkable by laminating a heat shrinkable sealant film on a non-heat shrinkable material. BACKGROUND ART Conventionally, heat-shrinkable composite packaging materials are known in which a heat-shrinkable base material is laminated with a sealant film having almost no heat-shrinkability. However, conventional heat-shrinkable base materials are mainly made of plastic films, and there are only a limited number of materials, and materials without heat-shrinkability are rarely used for this purpose, even if they have excellent other properties. However, since there was almost no shrinkage, sufficient cohesive strength could not be obtained, resulting in sagging and fine wrinkles during packaging, and a satisfactory finished appearance could not be obtained. The present invention was developed as a result of intensive research aimed at taking advantage of the characteristics of such non-heat-shrinkable base materials and imparting the necessary heat-shrinkability to improve the appearance after packaging. The present invention was achieved based on the discovery that a packaging material in which a heat-shrinkable sealant film is laminated on a heat-shrinkable sealant film provides a practically useful degree of heat-shrinkability. In other words, the present invention has a density of 0.91 to 25°C.
Provides a heat-shrinkable laminated packaging material made by laminating a heat-shrinkable sealant film made by biaxially stretching a 0.93 g/cm ³ ethylene copolymer film by 2.5 times or more in both the length and width, and a material that does not have heat-shrinkability. By performing heat shrinkage treatment after packaging, a satisfactory finished appearance can be obtained. Examples of the base material used in the present invention include breathable materials such as perforated nonwoven fabrics and cloths, and general-purpose plastic films that do not have self-shrinking properties such as stretched nylon films and stretched polypropylene films. It is not limited to these. In addition, as a heat-shrinkable sealant film, an ethylene copolymer having a density of 0.91 to 0.93 g/cm ³ at 25°C is used, which is easy to stretch and provides sufficient shrinkage stress, and is biaxially stretched by 2.5 to 6.5 times in both length and width. Films are preferred, such as linear low-density polyethylene (hereinafter referred to as L-
A film made by stretching 2.5 to 6.5 times (abbreviated as LDPE) or the like is preferably used. The non-heat-shrinkable material and the heat-shrinkable sealant film can be laminated by a commonly used method, such as extrusion lamination, dry lamination, etc. The heat-shrinkable laminated packaging material obtained as described above has sufficient heat-shrinkability depending on the application, and can be heat-sealed in the sealant layer, so that it can be heat-shrinkable without impairing the properties of the base material. It can be used as a material and provides packaging with a satisfactory finished appearance. The heat-shrinkable laminated packaging material obtained according to the present invention can be sealed by bar sealing, tape sealing, etc., or depending on the base material, by fusing sealing, etc., and can also be sealed by hot air or hot water. Because it can be shrunk by heating, etc., by heat-shrinking it after packaging, it can be packaged without wrinkles or sagging in appearance and in close contact with the packaged item. EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited thereto. In addition, the measuring method of the main characteristics measured in the present invention is shown below. Tensile strength and elongation: JIS Z-1521 Heat seal strength: Packaging material to be measured at 20℃
The humidity was adjusted to 65% RH for 24 hours, and the samples cut into 25 mm x 300 mm were stacked so that the sealant film sides faced each other, and this material was set at the specified temperature for a cylinder diameter of 50 mmφ size width 10 mm x length 300 mm. Seal with a bar sealer at a gauge pressure of 1 Kg/cm ² and a sealing time of 1 second, and condition the humidity at 20°C and 65% RH for 24 hours.
Sample to 15mm. This sample is attached to the Tensilon chuck and pulled at a speed of 300 mm/min, and the strength is read by the Tensilon chart and converted into cross-sectional area. Fusing seal strength: Packaging material to be measured at 20℃65
Humidify the sample under conditions of %RH, cut it into a size of 25 mm wide x 300 mm long, and fuse and seal the sample with a heat knife or nichrome wire set at a specified temperature. This sample was conditioned for 24 hours at 20°C and 65%RH, and then cut into 15mm width pieces. Attach this document to the Tensilon chuck.
The strength is read by the tension tensilon chart at a speed of 300 mm/min. Hot water or heat shrinkage rate: Cut the packaging material to be measured into approximately 20cm x 20cm and place it under the conditions of 20℃ and 65%RH.
After conditioning the humidity for 24 hours, accurately measure the longitudinal and transverse dimensions of the film. (The measured value is A.)
After completely immersing this sample in hot water or a glycerin bath at a predetermined temperature for 30 seconds, take it out and wash it with water. Leave to stand for a while and accurately measure the vertical and horizontal dimensions of the film. (The measured value is B.) The hot water shrinkage rate and the heat shrinkage rate are calculated using the following formula. Hot water or heat shrinkage rate (%) = A-B/A x 100 Hot air shrinkage rate: Packaging material to be measured about 20 cm x 20
After cutting into cm pieces and conditioning the humidity at 20℃65%RH for 24 hours,
Accurately measure the longitudinal and lateral dimensions of the sample (the measured value is A'). The sample is circulated at a predetermined temperature and at a wind speed of 1 m/min. After leaving (hanging) in the oven for 10 seconds, adjust the humidity at 20°C and 65% RH for 24 hours, and accurately measure the dimensions of the same area measured before processing. (This measured value is designated as B′) The hot air shrinkage rate is calculated using the following formula. Hot air shrinkage rate (%) = A'-B'/A' x 100 Example 1 High-density polyethylene fiber, basis weight 36g/
m ² , perforated nonwoven fabric and a sealant film that is simultaneously stretched to 5 times the density in both the vertical and horizontal directions.
A heat-shrinkable L-LDPE film with a thickness of 0.92 mm and a thickness of 35 μm was extruded and polysand-laminated according to a conventional method so as to have the following laminated film structure. After being left for a day, the physical properties were evaluated and shown in Example 1 in Table 1. Laminated film composition High-density polyethylene nonwoven fabric (basis weight 36g/m ² )/
Low density polyethylene (thickness 20μ)/heat shrinkable L-
LDPE (thickness 35μ) Comparative example 1 Density 0.92, thickness 35μ as a sealant film
A laminated packaging material prepared in exactly the same manner as in Example 1 except that an unstretched L-LDPE film consisting of It was shown to. Reference Example 1 Using the heat-shrinkable laminated packaging material obtained in Example 1, a cylindrical body having a width of 10 cm and a diameter of 11 cm was produced by a fusing sealing method with the sealant layer facing inside.
This was stacked to cover a glass bottle with an outer diameter of 10 cm, and passed through a hot air tunnel at a temperature of 120°C to shrink the laminated packaging material. As a result, the laminated packaging material closely adhered to the outer peripheral surface of the bottle, had no wrinkles, and was satisfactory in both practicality and appearance as a protective layer to prevent bottle breakage.

[Table] As shown in the above results, the laminated packaging material made of the nonwoven fabric and heat-shrinkable sealant of the present invention has impact resistance without impairing general physical properties or sealing properties.
It was confirmed that new excellent heat shrinkage properties were provided. Example 2 A nylon-6 film with a thickness of 15μ that was biaxially stretched at the same time and sufficiently heat-set, and one side of a nylon-6 film with a density of 0.92 and a thickness of 35μ that was simultaneously biaxially stretched 5 times in the longitudinal and transverse directions as a sealant film. Corona treatment (wetting tension
38 dyne/cm) heat-shrinkable L-LDPE film was coated with lamination adhesive AD- manufactured by Toyo Morton Co., Ltd.
503/CAT-1090/10 using a conventional method, the laminated packaging material was dry laminated at 35 to 40℃ for 2 hours.
The physical properties were evaluated after aging for several days, and the results are shown in the table below.
This is shown in Example 2 of 2. Comparative example 2 As a sealant film, density 0.92, thickness 35μ,
A dry laminated packaging material was prepared in exactly the same manner as in Example 2 except that an unstretched L-LDPE film with one side corona treatment (wetting tension 38 dynes/cm) was used, and after aging at 35 to 40°C for 2 days, the physical properties were determined. was evaluated. The results are shown in Table 2. Reference Example 2 A polyvinyl chloride tray (size 10 cm x 10 cm, depth 7 cm) for lid sealing was sealed by thermal bonding using the laminated packaging material obtained in Example 2 as a lid material. However, due to deformation during processing, the lid part sagged and had an undesirable wavy appearance. However, when this sealed tray was immersed in hot water at 95°C, the lid part became taut, resulting in a package with a good finished appearance.

[Table] As shown in the above results, the laminated packaging material composed of the plastic film and heat-shrinkable sealant of the present invention has newly been imparted with practically useful heat-shrinkability without impairing its general physical properties or sealing properties. The appearance has also been improved. As described above, the laminated packaging material of the present invention, which is made by laminating a base material with almost no self-heat shrinkage property and a heat-shrinkable film, has shrinkage properties that have practical value depending on the type of base material to which it is applied. However, it was confirmed that it can be used for packaging with a good finished appearance.

Claims (1)

[Scope of Claims] 1. A film made of an ethylene polymer having a density of 0.91 to 0.93 g/cm ² at 25°C, both vertically and horizontally.
When the heat-shrinkable sealant film stretched to 2.5 times or more and the non-heat-shrinkable base material have a fabric weight of 1, the non-heat-shrinkable base material has a fabric weight of 0.3 to 1. 2.0, and has a heat shrinkage rate of 2% or more at 100°C after lamination, and is used for packaging objects whose dimensions do not substantially change depending on packaging conditions. . 2 The heat-shrinkable sealant film covers the linear low-density polyethylene film by 2.5 mm each in length and width.
The heat-shrinkable laminated packaging material according to claim 1, characterized in that it is a film that has been stretched more than double. 3 Base material that does not have heat shrinkability has a basis weight of 70g/m ²
The heat-shrinkable laminated packaging material according to claim 1, which is a nonwoven fabric as follows. 4. The heat-shrinkable laminate according to claim 1, wherein the non-heat-shrinkable base material is a polyolefin or polyamide film with a thickness of 30 μm or less that has been simultaneously biaxially stretched and sufficiently heat-set. packaging materials.