JPS6364312B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a laminated inflation film for heavy packaging bags and a method for manufacturing the same.
More specifically, the present invention relates to a laminated inflation film for use in heavy-duty packaging bags that has a well-balanced combination of highly excellent bag breakage resistance, suitability for automatic packaging, transportability, workability, etc., and a method for producing the same. Heavy packaging bags, i.e. fertilizer, feed, sugar, salt,
Traditionally, kraft paper bags,
Low-density polyethylene bags are often used. However, heavy-duty packaging bags require high performance such as tear resistance, suitability for automatic packaging, transportability, and workability, so relatively high-density polyethylene is less effective as a material than low-density polyethylene. Although it has good strength properties, it lacks surface slippage and sealing properties when made into a film, and material performance does not necessarily reflect product performance, so it is used as a material for heavy-duty packaging bags. There are few examples, and the tube-shaped packaging material using the inflation method with a hard inner layer described in Japanese Patent Publication No. 40-9638 lacks sealing performance and is difficult to apply to heavy-duty packaging bags. Films with special structures made by special manufacturing methods, such as obliquely oriented laminated films, have relatively good performance in some cases, but they have the disadvantage of complicated film manufacturing processes and high manufacturing costs. The present inventors focused their attention on a film for heavy packaging bags produced by the inflation method, which is inexpensive to manufacture. The present inventors focused on the fact that relatively high-density polyethylene has better strength properties as a material than low-density polyethylene, and that it is possible to obtain a film with high strength even with a thin wall. Various studies have been conducted in order to obtain a film that has a good balance of high bag tear resistance, suitability for automatic packaging, transportability, workability, etc. The inventors have discovered that this object can be achieved by using a specific amount of styrene-butadiene-based thermoplastic elastomer as the main base material, and by laminating it with low-density polyethylene, and have completed the present invention. That is, the present invention has a density of 0.930 to 0.970,
97-65 parts by weight of polyethylene (1) with MI 0.002-0.5 and 3-35 parts by weight of styrene-butadiene thermoplastic elastomer
Composition (3) consisting of parts by weight is the inner layer, with a density of 0.910~
0.930, MI0.1 to 10.0 polyethylene (2) as the outer layer, the film is inflation-molded, and the thickness ratio of composition (3) and polyethylene (2) is 95:
This is a laminated inflation film for heavy packaging bags characterized by a ratio of 5 to 50:50. The characteristics of the laminated inflation film for heavy duty packaging bags obtained by the present invention are listed below. (1) The film according to the present invention has little anisotropy;
It has high strength properties (tensile, impact, puncture), high energy absorption performance, and high sealing performance, so it has good bag tear resistance and handling during work when made into a product. be. (2) The film according to the present invention has a large surface frictional resistance on its outer surface, so it is easy to handle, and when used as a product, it is less prone to deformation during transport or storage. (3) Since the film according to the present invention has appropriate rigidity and high sealing performance, it has excellent suitability for packaging machines. (4) Since the film according to the present invention maintains high performance such as bag breakage resistance in a well-balanced manner, it is a thinner yet high-performance product than conventional low-density polyethylene films. Next, the film of the present invention and its manufacturing method will be explained in detail. Polyethylene (1) in the present invention is an ethylene homopolymer or an ethylene-α-olefin copolymer with an ethylene content of 90 mol% or more, a density at 23°C of 0.930 to 0.970, and an MI of 0.002
~0.5, preferably 0.01-0.10. MI
If it is less than 0.002, it is substantially difficult to form a film, and if it is more than 0.5, it is unfavorable from the viewpoint of film formability and strength. In addition,
MI is the melt index value measured in g/10 minutes at a temperature of 190°C and a load of 2.16 kg according to ASTM D1238. The styrene-butadiene thermoplastic elastomer in the present invention has the general formula S-B-S, (S-B)
_o , B-(S-B) _o , (S-B) _o -S, (S-B) _n X
S is substantially composed of styrene or a polymer block mainly composed of styrene, B is composed of butadiene or a polymer block mainly composed of butadiene, and the styrene content is preferably 15 to 50% by weight. 25 to 45% by weight, and an MI(G) of 0.01 to 40, preferably 0.1 to 20. In addition, n is an integer of 2 to 10, m is an integer of 3 to 7, X represents a polyfunctional compound to which m polymer chains are bonded, and MI(G) is
The melt index value is measured in g/10 minutes at a temperature of 200° C. and a load of 5 kg according to ASTM D1238. Polyethylene (2) in the present invention is an ethylene homopolymer or a copolymer with a small amount of α-olefin or vinyl acetate, and has a density at 23°C of 0.910 to 0.930 and an MI of 0.1 to 10.0, preferably 0.1
~1.0. Composition (3) in the present invention refers to polyethylene (1)
and a styrene-butadiene thermoplastic elastomer to form one layer. The amount of polyethylene (1) in composition (3) is 97 to 65 parts by weight, preferably 95 to 75 parts by weight, and the amount of styrene-butadiene thermoplastic elastomer is 3 to 35 parts by weight, preferably 5 parts by weight. ~25 parts by weight. If the amount of polyethylene (1) in the composition (3) is 97 parts by weight or more and the amount of the styrene-butadiene thermoplastic elastomer is 3 parts by weight or less, the fracture resistance of the product as intended by the present invention will be reduced. The bag properties are poor and high performance cannot be obtained in a well-balanced manner, and the amount of polyethylene (1) is
If the amount of the styrene-butadiene thermoplastic elastomer is less than 65 parts by weight, and if it is more than 35 parts by weight, it is not preferable because the characteristics of polyethylene are lost and the strength properties (tensile, puncture, etc.) are reduced. Composition (3) comprising polyethylene (1) and styrene-butadiene thermoplastic elastomer according to the present invention
The thickness ratio of and polyethylene (2) is 95:5 to 50:50,
Preferably it is 90:10 to 60:40. polyethylene
If the thickness ratio (2) is more than 50, the mechanical strength and rigidity of the film will decrease, and if it is less than 5, the film will have too high rigidity and will not have a high degree of bag breakage resistance, which is not preferable. In the film of the present invention, polyethylene (1), a composition (3) made of a styrene-butadiene thermoplastic elastomer, and polyethylene (2) are tightly adhered to each other to form layers. The film according to the present invention is manufactured by the following method. A composition (3) consisting of polyethylene (1) and a styrene-butadiene thermoplastic elastomer, which have been previously dry blended or blended into pellets, and polyethylene (2) are transferred from separate extruders to an annular die attached to the extruder. It is obtained by supplying the resin separately to a die near the die lip, extruding the mixture so as to form a layer in a die near the die lip, and then performing inflation molding. In order to obtain sufficient strength characteristics and reduce strength unevenness, the film of the present invention is extruded from a recirculating die at a temperature of
It is extruded at 150°C to 270°C, preferably 170°C to 240°C, and inflation molded under arbitrary conditions such as a blow ratio of 1:2.5 to 1:8 and a frost line height of 200 to 2000 mm. The film of the present invention can be made from thin to thick, but in order to exhibit its performance as a heavy-duty packaging bag, it is preferably 25 to 250 μ thick. The film of the present invention can be used for fertilizer, feed, food, salt,
It is particularly useful as a material for heavy-duty packaging bags with relatively large contents for packaging sugar, chemicals, etc. Next, the present invention will be specifically explained using examples. Example 1 A composition (3) was prepared by dry blending 85 parts of polyethylene (1) with a density of 0.955 and an MI of 0.05 and 15 parts of a styrene-butadiene thermoplastic elastomer with a styrene content of 40% and an MI (G) of 9.0 using a blender. The inner layer is made of polyethylene (2) with a density of 0.918 and MI0.3,
Using separate extruders with a cylinder diameter of 50 mmφ and L/D 26, the composition (3) side was heated at 200°C, and the polyethylene (2) side was heated at 200°C.
At a set temperature of 170℃, die lip gap 1.5mm, diameter
Melt extrusion at a die temperature of 200℃ from a spiral structure annular two-layer die with a diameter of 75 mm and a diameter of 40 mm below the die lip at the confluence point, blowing ratio 4, frost line height 745 mm, take-up speed 8.6 m/min, and folding width 470 mm using the air-cooled inflation method. A laminated film having a thickness of 55 μm and a thickness ratio of composition (3) and polyethylene (2) of 85:15 was molded. When the strength characteristics of this film were measured, it had the values shown in Table 1 and Example 1. In addition, after making bags from this film and filling and sealing them with 10 kg of advanced chemical fertilizer, the bag was observed for accumulation, handling, and tearability due to dropping under the conditions shown in Table 1 (Note). The results are shown in Table 1 and Example 1. Comparative Example 1 The same polyethylene as in Example 1 was used except that it did not contain the styrene-butadiene thermoplastic elastomer, and the same inner layer/outer layer ratio as in Example 1 was 85:15.
A laminated film was prepared under the same conditions as in Example 1, and the strength characteristics and product performance of this film were measured in the same manner as in Example 1. The results are shown in Table 1 and Comparative Example 1-1.

【table】

[Table] Example 2-1 95 parts of the same polyethylene (1) as in Example 1 and Example 1
and 5 parts of the same styrene-butadiene thermoplastic elastomer as the inner layer by dry blending with a blender (3), and the thickness ratio with the outer layer of polyethylene (2) with a density of 0.918 and an MI of 0.3 is 80:20. A laminated film with a thickness of 138 μm was molded under the same conditions as in Example 1. The strength characteristics of this film and the product performance of the bag-made product (filled with 20 kg of advanced chemical fertilizer) were measured in the same manner as in Example 1. The results are shown in Table 2 and Example 2-1. Example 2-2 85 parts of the same polyethylene (1) as Example 1 and Example 1
A laminated film with a thickness of 139 μm was molded under the same conditions as in Example 2-1 except that the inner layer was composed of Composition (3) obtained by dry blending the same styrene-butadiene thermoplastic elastomer (15 parts) with 15 parts of the same styrene-butadiene thermoplastic elastomer in a blender. The strength characteristics of this film and the product performance of the bag-made product were measured under the same conditions as in Example 2-1. The results are shown in Table 2 and Example 2-2. Example 2-3 70 parts of the same polyethylene (1) as Example 1 and Example 1
A laminated film with a thickness of 138 μm was molded under the same conditions as in Example 2-1, except that the inner layer was composed of Composition (3) obtained by dry blending the same styrene-butadiene thermoplastic elastomer and 30 parts of the same styrene-butadiene thermoplastic elastomer in a blender. The strength characteristics of this film and the product performance of the bag-made product were measured under the same conditions as in Example 2-1. The results are shown in Table 2 and Examples 2-3. Comparative Example 2-1 60 parts of the same polyethylene (1) as Example 1 and Example 1
A laminated film with a thickness of 140 μm was molded under the same conditions as in Example 2-1, except that the inner layer was composed of composition (3) obtained by dry blending the same styrene-butadiene thermoplastic elastomer with 40 parts of the same styrene-butadiene thermoplastic elastomer in a blender. The strength characteristics of this film and the product performance of the bag-made product were measured under the same conditions as in Example 2-1. The results are shown in Table 2 and Comparative Example 2-1. Comparative Example 2-2 In Example 2-1, the thickness ratio of the inner layer and the outer layer was 80:20 under the same conditions as Example 2-1 except that the styrene-butadiene thermoplastic elastomer was not included.
A laminated film with a thickness of 137 μm was molded. The strength characteristics of this film and the product performance of the bag-made product were measured under the same conditions as in Example 2-1. The results are shown in Table 2 and Comparative Example 2-1.

[Table] Example 3 90 parts of the same polyethylene (1) as Example 1 and Example 1
and 10 parts of the same styrene-butadiene thermoplastic elastomer as the inner layer by dry blending with a blender (3), and the thickness ratio with the outer layer of polyethylene (2) with a density of 0.918 and an MI of 0.3 is 60:40. A laminated film with a thickness of 81 μm was molded under the same conditions as in Example 1 except for the line height of 520 mm. The strength characteristics of this film and the product performance of the bag-made product (filled with 15 kg of advanced chemical fertilizer) were measured in the same manner as in Example 1. The results are shown in Table 3 and Example 3. Comparative Example 3 90 parts of the same polyethylene (1) as Example 1 and Example 1
and 10 parts of the same styrene-butadiene-based thermoplastic elastomer as the inner layer, and the thickness ratio with the outer layer of polyethylene (2) with a density of 0.918 and MI of 0.3 is 45:55. A laminated film with a thickness of 80 μm was molded under the same conditions as in Example 3. The strength characteristics of this film and the product performance of the bag-made product were measured under the same conditions as in Example 3. The results are shown in Table 3.
This is shown in Example 3.

【table】

[Table] Example 4 A composition (3) obtained by dry blending 80 parts of polyethylene (1) with a density of 0.941 and an MI of 0.10 and 20 parts of the same styrene-butadiene thermoplastic elastomer used in Example 1 in a blender was used as the inner layer. , density 0.918,
The outer layer and thickness ratio of polyethylene (2) with MI0.3 is 80:
A laminated film with a thickness of 65 μm was molded under the same conditions as in Example 1 except that the blow ratio was 20 mm, the blow ratio was 3, and the frost line height was 740 mm. The strength characteristics of this film and the product performance of the bag-made product were measured in the same manner as in Example 1. The results are shown in Table 4 and Example 4. Example 5 Polyethylene (1) with density 0.955 and MI 0.04 and density
A laminated film with a thickness of 63 μm was molded under the same conditions as in Example 4, except that polyethylene (2) having an MI of 0.919 and an MI of 2.0 was used. The strength characteristics of this film and the product performance of the bag-made product were measured in the same manner as in Example 4. The results are shown in Table 4 and Example 5. Comparative example 4 Polyethylene (1) with density 0.950 and MI 1.0 and density
A laminated film with a thickness of 64 μm was molded under the same conditions as in Example 4 except that polyethylene (2) with an MI of 0.918 and an MI of 0.3 was used. The formability of the film was poor.
The strength characteristics of this film and the product performance of the bag-made product were measured in the same manner as in Example 4. The results are shown in Table 4.
This is shown in Comparative Example 4.

[Table] Example 6 A composition (3) obtained by dry blending 90 parts of polyethylene (1) with a density of 0.955 and an MI of 0.05 with 10 parts of the same styrene-butadiene thermoplastic elastomer used in Example 2 in a blender was used as the inner layer. , density 0.920,
The thickness ratio of MI0.4 polyethylene (2) to the outer layer is 70:
30, frost line height 500mm, blow ratio 3, extrusion temperature: composition (3) 210℃, polyethylene (2) 170℃,
A laminated film with a thickness of 50 μm was molded under the same conditions as in Example 1 except that the die temperature was 210° C. Characteristics and performance of this film (Advanced chemical fertilizer 10kg
Filling) was measured in the same manner as in Example 1. The results are shown in Table 5 and Example 6. Comparative Example 5 In Example 6, frost line height 150mm
A laminated film with a thickness of 52 μm was molded under the same conditions as in Example 6 except for the following. The properties and performance of this film were measured in the same manner as in Example 6. The results are shown in Table 5 and Comparative Example 5. Comparative Example 6 In Example 6, frost line height 2100mm
The thickness was 51μ under the same conditions as Example 6 except that
A laminated film was molded, but the molding stability was poor, and the finished film had poor surface properties. Comparative Example 7 In Example 6, a 52μ thick laminated film was molded under the same conditions as Example 6 except that the blow ratio was 1.5. The properties and performance of this film were measured in the same manner as in Example 6. The results are shown in Table 5 and Comparative Example 7.

【table】

Claims (1)

[Scope of Claims] 1. The inner layer is a layer of a composition consisting of 97 to 65 parts by weight of polyethylene having a density of 0.930 to 0.970 and an MI of 0.002 to 0.5 and 3 to 35 parts by weight of a styrene-butadiene thermoplastic elastomer; 0.930, an MI 0.1 to 10.0 polyethylene layer as an outer layer, the film is inflation-molded, characterized in that the thickness ratio between the inner layer and the outer layer is 95:5 to 50:50. Laminated inflation film for heavy duty packaging bags. 2. A composition comprising polyethylene and a styrene-butadiene thermoplastic elastomer with a density of 0.930 to 0.970 and an MI of 0.002 to 0.5, and a density of 0.910 to 0.930,
Polyethylene with an MI of 0.1 to 10.0 is separately supplied to an annular die attached to an extruder, and the polyethylene is combined to form a layer in the die near the die lip.
Extrusion at extrusion temperature 150-270℃, blow ratio 1:2.5
A method for producing a laminated inflation film for heavy packaging bags, characterized by carrying out inflation molding at a ratio of ~1:8 and a frost line height of 200 to 2000 mm.