JPS6140553B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polypropylene multilayer film with improved heat sealability. Plastic packaging films are used in many industrial fields to maintain and improve product value and streamline distribution processes. It is a well-known fact that heat sealability is one of the most important properties required of plastic films for packaging. Excellent heat-sealability requires that heat-sealing is possible at low temperatures and that the heat-sealed portion has high strength. Lower heat-sealing temperatures allow for faster packaging, which provides significant economic benefits. Polypropylene film, especially biaxially oriented polypropylene film, has excellent transparency and rigidity and is used in various industrial fields, mainly in the food packaging field, but it has the disadvantage of lacking heat sealability due to its inert surface. There is. In order to improve this drawback, various methods have been adopted to treat the film surface by physical or chemical means. One of these is a multilayer film coated with a resin having a lower heat-sealing temperature than the polypropylene base material to form a so-called heat-sealing layer, which is widely used industrially. Ethylene propylene copolymers having an ethylene content of 1 to 6% by weight are generally used as resins with low heat-sealing temperatures, but the reduction in heat-sealing temperatures is insufficient. Recently, propylene-butene copolymers have been used in some cases, but even this resin is insufficient in lowering the heat-sealing temperature. The present inventors have conducted extensive studies on lowering the heat-sealing temperature of polypropylene films, and have found that a propylene-butene-1 copolymer with a butene-1 content of 10 to 25% by weight is added to the surface of a base layer made of polypropylene. By coating a mixture layer of 85 to 97 parts by weight of the copolymer and 15 to 3 parts by weight of a butene-1 copolymer having a butene-1 content of 80 to 93% by weight, the heat sealing temperature is significantly lowered. The present inventors have discovered that the heat sealing strength is high and that the other properties required of the film are not degraded in any way, leading to the present invention. Conventionally, it has been empirically known that the heat-sealing temperature of a mixture of similar resins is based on the additivity of the heat-sealing temperature of the resin composition, but the mixture layer of the present invention has an unexpected heat-sealing temperature. showed a decrease in The propylene-butene-1 copolymer used in the present invention is usually polymerized by a method widely used in industry, and the butene-1 content is
It is a 10-25% by weight random copolymer. If the butene-1 content is less than 10% by weight, the heat-sealing temperature decreases little, which is contrary to the purpose of the present invention. If the butene-1 content is 25% by weight or more, the slippage between the films will deteriorate, making it impossible to put them into practical use. The butene-1 copolymer used in the present invention is a copolymer of butene-1 and an α-olefin other than butene-1 having 2 to 10 carbon atoms, with a butene-1 content of 80 to 93% by weight. %, and is usually polymerized by a method widely used in industry.
If the butene-1 content is less than 80% by weight, the slippage between the films will deteriorate, making it impossible to put them into practical use.
If it is 93% by weight or more, the effect of lowering the heat sealing temperature will not be observed, and the slippage between the films will worsen. When a butene-1 copolymer alone is evaluated as a film, it is recognized that as the butene-1 content decreases, the slippage between the films deteriorates. It is an interesting fact that the slippage between films improves only when the content is in the range of 80 to 93% by weight. The composition of the heat seal layer in the present invention must be a ratio of 85 to 97 parts by weight of propylene-butene-1 copolymer and 15 to 3 parts by weight of butene-1 copolymer. If the proportion of the butene-1 copolymer is 15 parts by weight or more, the slippage between the films will deteriorate, making it impossible to put them into practical use. The proportion of butene-1 copolymer is 3
If the amount is less than 1 part by weight, the effect of lowering the heat sealing temperature of the propylene-butene-1 copolymer will not be recognized. There is no problem in adding to the mixture layer according to the present invention anti-deterioration agents, lubricants, anti-blocking agents, weathering agents, etc. which are commonly used in film applications. The present invention will be explained below with reference to Examples, but these are not intended to limit the present invention in any way. Heat-sealing temperature and strength measurement method: Using a heat-sealing tester manufactured by Toyo Seiki Co., Ltd., heat-seal the heat-sealed surfaces together at several temperatures. A 180° peel strength test is performed on two heat-sealed film test pieces to determine the peel strength at each temperature. The temperature at which the peel strength was 300 g/25 mm width was determined from the graph and was determined as the heat sealing temperature. Since the peel strength reached a certain value at a certain temperature, the peel strength at that time was taken as the heat seal strength. Butene-1 content measurement method...N, J,
The WEGEMERG Method, (Journal of
JOUNAL OF APPLIED POLYMER
SCIENCE) vol 14 p573) using a Shimadzu spectrophotometer IR-27G. Sliding property measurement method: Using a friction angle measuring device manufactured by Toyo Seiki Co., Ltd., a stainless steel block wrapped in film and weighing 1 kg was placed on a plate covered with film, and the block was tilted at a speed of 2.7°/sec. The angle θ at which the vehicle started sliding is expressed as tanθ. Melt flow index measurement method...According to JIS K-6758,
Measurement was performed using a melt indexer model MX-101 manufactured by Takara Kogyo Co., Ltd. Examples 1-3 Butene-1 content 21.0% by weight, melt flow index
11.0 propylene-butene-1 copolymer 97, 93,
To 88 parts by weight, 3, 7, and 12 parts by weight of a commercially available butene-1 copolymer (Witron 8240, butene-1 content 90%, manufactured by U.S. Witco Co., Ltd.) were mixed in a super mixer. The mixture was melted and kneaded using a 40 mmφ extruder manufactured by Co., Ltd. to obtain pellets. Next, a two-layer film was obtained using an in-die adhesive type two-layer coextrusion die using Sumitomo Noblen FA8011 (manufactured by Sumitomo Chemical) as the base layer and the above pellet as the heat-sealing layer on the surface. The thickness of the base layer of this film was 45μ, and the thickness of the heat seal layer was 14μ. The heat-sealing temperature and heat-sealing strength of the heat-sealing surfaces of this film were measured and are shown in Table 1.
The results shown are obtained. Further, the results of measuring the slipperiness between the heat-sealed surfaces are also shown in Table 1. Comparative Examples 1 to 3 Witron 8240 to 100, 80, 0 parts by weight of the same propylene-butene-1 copolymer as Examples 1 to 3
0, 20, and 100 parts by weight of each were mixed in a super mixer and melt-kneaded in a 40 mmφ extruder manufactured by Tanabe Plastics Co., Ltd. to obtain pellets. Two-layer films were obtained in the same manner as in Examples 1 to 3, and the heat-sealing temperature, heat-sealing strength, and slipperiness of the heat-sealing surfaces were measured. Table 1 shows the results. Comparative Examples 4 and 5 5 and 10 parts by weight of Witron 1200s (butene-1 content 95% by weight, manufactured by Witco, USA) were added to 95 and 90 parts by weight of the same propylene-butene-1 copolymer as in Examples 1 to 3, respectively. Mix in a super mixer,
The mixture was melt-kneaded using a 40 mmφ extruder manufactured by Tanabe Plastics Co., Ltd. to obtain pellets. Two-layer films were obtained in the same manner as in Examples 1 to 3, and the heat-sealing temperature, heat-sealing strength, and slipperiness of the heat-sealing surfaces were measured. Table 1 shows the results. Comparative Example 6 95 parts by weight of the same propylene-butene-1 copolymer as in Examples 1 to 3 was mixed with 5 parts by weight of Witron 0300 (polybutene-1, manufactured by U.S. Witco Co., Ltd.) in a super mixer, and 95 parts by weight of the same propylene-butene-1 copolymer as in Examples 1 to 3 was mixed in a super mixer. 40mm
The mixture was melt-kneaded using a φ extruder to obtain pellets. Two-layer films were obtained in the same manner as in Examples 1 to 3, and the heat-sealing temperature, heat-sealing strength, and slipperiness of the heat-sealing surfaces were measured. Table 1 shows the results. Comparative Example 7 Butene-1 copolymer (butene-1-propylene copolymer, butene-1 content 76% by weight, molten Flow index 8.4) was mixed with 10 parts by weight in a super mixer, manufactured by Tanabe Plastics Co., Ltd.
The mixture was melt-kneaded using a 40 mmφ extruder to obtain pellets. Two-layer films were obtained in the same manner as in Examples 1 to 3, and the heat-sealing temperature, heat-sealing strength, and slipperiness of the heat-sealing surfaces were measured. Table 1 shows the results.

[Table] Examples 4 and 5 Butene content 12.3% by weight, melt flow index 6.5
Butene-1 copolymer (butene-1-propylene copolymer, butene-1 content 84.1% by weight,
5 and 10 parts by weight of melt flow index 7.8) were mixed in a super mixer, and a 40mm
The mixture was melt-kneaded using a φ extruder to obtain pellets. Next, using Sumitomo Noblen FS2011 (manufactured by Sumitomo Chemical) as the base layer and the above pellet as the heat-sealing layer on the surface, a two-layer film was obtained using an in-die adhesive type two-layer coextrusion die. The thickness of the base layer of this film was 230μ, and the thickness of the heat seal layer was 20μ. This film was stretched 3 times in length and width at 130°C using a research polymer film biaxial stretching apparatus manufactured by Iwamoto Seisakusho, and then heat set at 120°C. Table 2 shows the results of measuring the heat-sealing temperature, heat-sealing strength, and slipperiness of the heat-sealed surfaces of the multilayer biaxially stretched film obtained as described above. Comparative Examples 8 and 9 To 100 and 80 parts by weight of the same propylene-butene-1 copolymer as in Examples 4 and 5, 0.20 parts by weight of each of the same butene-1 copolymers as in Examples 4 and 5 were added in a super mixer. Mixed and made by Tanabe Plastic Co., Ltd. 40mm
The mixture was melt-kneaded using a φ extruder to obtain pellets. A multilayer biaxially stretched film was obtained in the same manner as in Examples 4 and 5, and the heat-sealing temperature, heat-sealing strength, and slipperiness of the heat-sealing surfaces were measured. Table 2 shows the results.

[Table] Examples 6, 7 Butene-1 content is 23.9% by weight, melt flow index
5 and 10 parts by weight of Witron 8240 were mixed with 95 and 90 parts by weight of the propylene-butene-1 copolymer of 15.2 in a super mixer, and melt-kneaded in a 40 mmφ extruder manufactured by Tanabe Plastics to obtain pellets. Ta. A two-layer film was obtained in the same manner as in Examples 1 to 3, and the heat-sealing temperature, heat-sealing strength, and slipperiness of the heat-sealing surfaces of this film were measured, and the results are shown in Table 3. Comparative Examples 10 and 11 100 and 80 parts by weight of the same propylene-butene-1 copolymer as in Examples 6 and 7 were mixed with 0 parts by weight and 20 parts by weight of Witron 8240, respectively, in a super mixer, and the mixture was mixed with a supermixer manufactured by Tanabe Plastics Co., Ltd. The mixture was melt-kneaded using a 40 mmφ extruder to obtain pellets. A two-layer film was obtained in the same manner as in Examples 1 to 3, and the heat-sealing temperature, heat-sealing strength, and slipperiness of the heat-sealing surfaces of this film were measured, and the results are shown in Table 3. Comparative Example 12 Butene-1 content is 8.5% by weight, melt flow index
5 parts by weight of Witron 8240 was mixed with 95 parts by weight of a propylene-butene-1 copolymer of 8.8 in a super mixer, and the mixture was melt-kneaded in a 40 mmφ extruder manufactured by Tanabe Plastics Co., Ltd. to obtain pellets. A two-layer film was obtained in the same manner as in Examples 1 to 3, and the heat-sealing temperature, heat-sealing strength, and slipperiness of the heat-sealing surfaces of this film were measured, and the results are shown in Table 3. Comparative Example 13 Butene-1 content is 27.2% by weight, melt flow index
5 parts by weight of Witron 8240 were mixed with 95 parts by weight of the propylene-butene-1 copolymer No. 13 in a super mixer, and the mixture was melt-kneaded in a 40 mmφ extruder manufactured by Tanabe Plastics Co., Ltd. to obtain pellets. A two-layer film was obtained in the same manner as in Examples 1 to 3, and the heat-sealing temperature, heat-sealing strength, and slipperiness of the heat-sealing surfaces of this film were measured, and the results are shown in Table 3.

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Claims (1)

[Claims] 1. 85 to 97 parts by weight of a propylene-butene-1 copolymer having a butene-1 content of 10 to 25% by weight and 80 to 93 parts by weight of a butene-1 content on at least one surface of a base layer made of polypropylene. Butene-
A polypropylene multilayer film formed by forming a mixture layer with 15 to 3 parts by weight of a copolymer.