JPH045317Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Technical Field of the Invention] The present invention relates to a wrap-seal packaging material that is easy to operate and has excellent heat-sealability. [Prior art] Packaging materials that can be used to make bags or package goods by heat sealing have an ethylene content of 0.5
~1.5% by weight of biaxially oriented polypropylene film A, A/B/C laminated film consisting of uniaxially oriented polypropylene film B having a lower ethylene content than A and non-oriented layer C (Japanese Utility Model Publication No. 52-21345); A three-layer laminated polypropylene film (Japanese Unexamined Patent Application Publication No. 128685-1985) consisting of a biaxially oriented polypropylene film, with a low birefringence ethylene/propylene copolymer layer laminated on one side and a high birefringence ethylene/propylene copolymer layer laminated on the other side. No. 2) is known. However, these packaging materials have problems such as having a heat-sealing layer on only one side, making it impossible to lap-seal, or adding low-temperature heat-sealing properties to the packaging materials, resulting in poor slipperiness, blocking, and poor processability. There were flaws. [Object of the invention] The object of the present invention is to eliminate the above-mentioned conventional drawbacks and to provide a wrap packaging material having improved slip properties and heat-sealing strength. [Structure of the invention] The wrap seal packaging material of the present invention that achieves the above object is A/B/D/B/C or A/B/C.
A is a thick olefin-based polymer with a melting point of 137°C or less or low crystallinity.
B is a layer of biaxially oriented polypropylene film which is thicker than both A and C, and C has a melting point of 140° C. or higher and a thickness of 3 μm.
It is a layer of an olefinic polymer having a thickness of ~9μ, and the D is an adhesive layer or a printing layer. Hereinafter, the present invention will be explained based on embodiments shown in the drawings. FIG. 1 shows the first embodiment of the present invention, with A/B/
It has a three-layer laminated structure of layer C, that is, layer B is sandwiched between layers A and C. The A layer is an olefinic polymer having a melting point of 137° C. or less or low crystallinity, and is thinner than the C layer described later, and has a thickness of 0.3 to 1.5 μm. Here, olefin polymers with a melting point of 137°C or less are ethylene/propylene random copolymers with an ethylene content of 4% by weight or more, propylene/
Olefin copolymers or terpolymers such as butene copolymers, ethylene/butene copolymers, ethylene/vinyl acetate copolymers, ethylene/ethyl acrylate copolymers, ionomers, blends of these copolymers, In addition, these and polyethylene,
A polymer selected from a blend of polypropylene, polybutene, etc., preferably an ethylene/propylene random copolymer, a propylene/propylene random copolymer, etc.
It is a butene copolymer. When the melting point of such a polymer is higher than 137°C,
The starting temperature for heat sealing is high, resulting in poor heat sealing properties. In addition, low-crystalline olefin-based polymers include olefin-based elastomers, synthetic rubbers, etc. Refers to copolymers consisting of more than one species and blends thereof, which have a crystallinity of 40% or less as measured by X-ray diffraction. If the thickness of the A layer is less than 0.3μ, the heat sealing force will be weak and the heat sealability will be poor, and if it exceeds 1.5μ, the slipperiness will be poor, resulting in defects such as wrinkles during processing. Furthermore, the A layer is non-oriented or substantially non-oriented and maintains excellent heat sealability. "Substantially non-oriented" refers to the case of manufacturing by the co-extrusion method described below, and the fine orientation that occurs during melt extrusion when manufacturing and bonding the A layer alone is also "substantially non-oriented". included. Next, layer B is a biaxially oriented polypropylene film. This polypropylene film has a propylene content of 50% by weight, preferably 80% by weight or more, and is biaxially stretched. Stretching may be simultaneous stretching or sequential stretching; for example, in the case of sequential biaxial stretching, the temperature is 120 to 140°C.
While heating it, it is stretched 3.7 to 7 times in the longitudinal direction,
Then, it is stretched 6 to 12 times in the transverse direction in an atmosphere at 150 to 165°C. Further, if necessary, relaxation heat treatment may be performed in an atmosphere of 140 to 160°C. Although the thickness of layer B is not particularly limited, it is selected to be thicker than both layer A and layer C. The C layer is an olefinic polymer layer having a melting point of 140° C. or higher and a thickness of 3 to 9 μm. More specifically, olefin binary or ternary copolymers with an ethylene content of 3.5% by weight or less, such as ethylene/propylene random copolymers, propylene/butene copolymers, ethylene/butene copolymers, and copolymers thereof. and blends of these copolymers with polyethylene, polybutene-1, polypropylene, etc. However, when containing butene, the butene content is preferably 4% by weight or less. If the melting point of the polymer in the C layer is less than 140°C, the film will have poor slip properties. Further, if the thickness of the C layer is thinner than 3μ, the heat sealing force will be low, and if it exceeds 9μ, the heat sealing force will be higher than required, but the slipperiness will be poor. Like the A layer, this C layer is also non-oriented or substantially non-oriented. In the packaging material manufacturing method of the present invention, layers A and C are extruded and laminated in the order of A/B/C. These laminated sheets are stretched at the optimum stretching temperature for layer B, so layer A has a lower melting point than layer B.
The stretching of the layer and C layer is almost non-oriented. In addition, known additives such as stabilizers, etc. may be added to any or all layers of the packaging material of the present invention.
It goes without saying that ultraviolet absorbers, antistatic agents, colorants, fillers, plasticizers, lubricants, etc. may be mixed. Additionally, any or all of the layers may be subjected to surface treatment such as corona discharge treatment. FIG. 2 shows a second embodiment of the present invention, in which a vapor deposited layer and/or a printed layer D is formed within layer B. This B layer is formed after forming the D layer on the surface of the B1 layer or B2 layer by vapor deposition and/or printing.
It is formed by laminating Layer/A layer and B2 layer/C layer with adhesive or extrusion laminate. Note that the position where the D layer is deposited and/or printed may be either the B1 layer or the B2 layer, and is not particularly limited. [Effect of the invention] As described above, according to the invention, in either the A/B/D/B/C laminated structure including the D layer or the A/B/C laminated structure not including the D layer, Also, layer A, which has a lower melting point and is thinner than layer B, is laminated on one side of layer B, while layer A is laminated on the other side of layer B.
Layer C, which has a higher melting point than Layer A and is thicker than Layer A, is laminated. Therefore, when the packaging materials of the present invention are overlapped,
As shown in Figure 3, layer A and layer C are always bonded. Furthermore, the thin A layer, which has a low melting point, provides good slipperiness during heat sealing and improves operability. On the other hand, the C layer, which is thicker than the A layer, gives thickness to the entire heat seal layer together with the B layer, which serves as the substrate.
Can maintain strength. Therefore, it is possible to improve the slipperiness with the high-temperature sealing plate during automatic packaging. The measurement method adopted in this invention will be explained below. (1) Melting point: Perkin-Elmer differential scanning calorimeter model
Using the DSC-2 model, a 5 mg sample was heated to 280°C at a heating rate of 20°C/min, held for 5 minutes, cooled at the same rate, and then heated again. Take the melting curve. The highest peak point of this curve is taken as the melting point. (2) Slip coefficient: Lay the opposite sides of two samples that have been conditioned for 24 hours in a room at 20°C and 65% RH, and then
A single sample was moved at a speed of 150 mm/min with a load of 100 g placed on it, and its resistance value was read and expressed as a calculated value of resistance value (g)/200 g. A value similarly measured on a hot plate heated to 100°C indicates the high-temperature slip coefficient. (3) Heat sealing: Heat a vertically-grained metal plate and a grid-shaped metal plate to a set temperature, place the film between the metal plates with opposite sides on top of each other, and press with a pressure of 1 kg/cm ² for 0.5 seconds. I sealed it. The peel strength of this seal film is measured, and this strength per centimeter is called heat seal strength. Examples of the present invention will be described below. [Example] Examples 1 to 4, Comparative Examples 1 and 2 A layer raw materials (MI7 to 10) shown in the table below and polypropylene (MI2.0) (B layer) were coextruded at 280°C and cooled and molded. Then, it was stretched 4 times in the width direction while heating to 120 to 140°C, and 10 times in the longitudinal direction in an atmosphere at 155 to 165°C. The polypropylene surface of this biaxially stretched film was surface-treated to give a wettability index of 38 dyne/cm. Layer C was similarly coextruded, biaxially stretched, and surface treated. Aluminum vapor deposition was performed on the polypropylene surface of the former, printing was performed on the polypropylene surface of the latter, and the two were bonded together using an adhesive (urethane type) to process a lap seal (sealing the inner and outer surfaces). Example 5, Comparative Examples 3 and 4 Raw materials for layers A and C shown in the table below and polypropylene (MI2.0) were coextruded at 280°C and stretched in the same manner as in Example 1.

[Table] As is clear from the table, in Examples 1 to 5 where the thickness of the A layer is thin, the slip coefficients at room temperature and high temperature are low;
Comparative Examples 1 and 2, which are thick, have high slip coefficients at room temperature and high temperature, poor processing characteristics, and tend to wrinkle near the sealing surface. Furthermore, polymers with a high melting point of 140°C or higher have poor heat sealability.

[Brief explanation of the drawing]

Fig. 1 is a partially enlarged sectional view showing the first embodiment of the present invention, Fig. 2 is a partially enlarged sectional view showing the second embodiment of the present invention, and Fig. 3 shows the usage situation of the packaging material of the present invention. It is an enlarged sectional view.

Claims (1)

[Scope of utility model registration request] It has a laminated structure of A/B/D/B/C or A/B/C, where A is an olefinic polymer with a melting point of 137°C or less or low crystallinity and a thickness of 0.3 to 1.5μ.
B is a layer of biaxially oriented polypropylene film which is thicker than both A and C, C is a layer of olefinic polymer having a melting point of 140° C. or higher and a thickness of 3 to 9 μm, and D is a wrap seal packaging material characterized by having an adhesive layer or a printing layer.