JPH0465782B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Field of Application) The present invention relates to a coated polyolefin film with excellent suitability for heat-seal packaging. More specifically, the present invention relates to a coated film that has good packaging stability during high-speed automatic packaging and can be packaged without impairing the packaging aesthetics of interior items. (Prior Art) Conventionally, polyvinylidene chloride resin-coated polyolefin films have been widely used as packaging materials because of their excellent gas barrier properties, heat sealability, transparency, etc. For example, a heat-sealable polyvinylidene chloride resin-coated polyolefin film is used as the outer packaging film for cassette tapes, boxed medical products, confectionery, etc. In this case, this outer packaging film is generally used to facilitate opening. The product is packaged with tamper tape heat-sealed to the inside of the package.
Furthermore, polyolefin films, which are the base material for such packaging films, are usually heat-shrinkable so that they can be heat-shrinked during the packaging process to create a neat packaging finish. The heat sealing temperature and time were selected accordingly. (Problems to be Solved by the Present Invention) However, in recent years, there has been a strong demand for high-speed packaging for the purpose of improving efficiency, and therefore, consideration has been given to applying short-time, high-temperature conditions as heat-sealing conditions during packaging. However, since the base film has heat-shrinkability as described above, heat-shrinkage wrinkles are likely to occur in the heat-sealed portion due to high-temperature conditions, reducing commercial value. Further, there are disadvantages such as curling and getting caught in high-speed automatic packaging machines. (Means for Solving the Problems) In order to solve these drawbacks, the inventors of the present invention have made extensive studies and found that by using a coated polyolefin film that has heat shrinkage characteristics within a limited range, it is possible to The inventors discovered that even when partially heat-sealed, there were no wrinkles or curls, leading to the completion of the present invention. That is, the present invention has a heat shrinkage stress of 5 to 50 g/15 mm width in the vertical direction and 10 g in the horizontal direction for 1 second at a temperature of 120°C.
A heat-sealable polychloride for high-speed automatic packaging that is ~100g/15mm wide and has a heat shrinkage rate of 0.5-2.5% in both the vertical and horizontal directions when heat-sealed at a temperature of 135°C for 0.25 seconds. It is a polyolefin film coated with vinylidene resin, and more preferably has a heat shrinkage stress of 10 to 40 g/15 mm width in the longitudinal direction and 30 g/15 mm in the transverse direction at a temperature of 120°C.
~70g/15mm width, temperature 135℃, heat sealing rate for 0.25 seconds in both vertical and horizontal directions
The polyvinylidene chloride resin-coated polyolefin film is characterized in that the content of the polyvinylidene chloride resin is 0.8 to 2.0%. Heat shrinkage stress at 120℃ is 50g/15mm in the vertical direction
Width or more, 100g/15mm width or more in the horizontal direction,
When the tear tape is heat-sealed in a high-speed automatic packaging machine, the heat-sealed area is narrow (1 to 3 mm) and is locally heat-treated, causing curling due to an imbalance in the thermal shrinkage behavior of the tear tape and the covering polyolefin film. While the packaging film is being fed into a process for packaging cassette tapes, etc., it gets caught in a part of the machine, and the packaging film cannot be fed smoothly. As a result, the packaging machine frequently stops, making it difficult to manage the packaging process and reducing productivity. Also, the heat shrinkage rate during heat sealing at 135℃ is
If it is 2.5% or more, when an audio cassette tape case or the like is packaged, heat shrinkage wrinkles will become severe at the heat-sealed areas of the mouth, bottom, and chest, which will reduce the commercial value of the packaged product, which is not desirable. On the other hand, the heat shrinkage stress at 120℃ is 5g/
15mm width or less, lateral direction 10g/15mm width or less or 135℃
If the heat shrinkage rate during heat sealing is 0.5% or less, when packaging cassette tapes, etc., the heat shrinkage properties of the covering polyolefin film will be insufficient, the packaging will not be finished neatly, and the product value will decrease. do. It is known that a coated polyolefin with a heat shrinkage rate of 10% or less at 120°C has good wrinkle resistance during packaging, but even if it meets this condition, it is not suitable for the film of the present invention. Seal part,
Curls and wrinkles in the heat-sealed area result in poor processability and poor packaging appearance. Examples of the polyolefin film used as the base material include biaxially oriented polypropylene film, unstretched polypropylene film, and unstretched polyethylene film. As shown in the examples, by the next step of coating and drying,
Since the shrinkage rate and shrinkage stress are reduced, an original fabric with a desired shrinkage rate and shrinkage stress can be selected from commercially available products, or it can be prepared by a conventional method through film forming, stretching heat treatment, etc. The polyvinylidene chloride resin coated to provide heat sealing properties has a low vinylidene chloride content.
It is preferably 90% or less, and if it is more than 90%, the heat sealability will deteriorate. The coating amount of the polyvinylidene chloride resin is not particularly limited, although the coating thickness is usually 1 to 2 .mu.m. The coating is usually formed by applying a solution or emulsion to one side using a Meyer bar, air knife, dipping, or reverse roll method and drying it. It should be noted that other compounding agents such as anti-blocking agents, slip agents, antistatic agents, etc. may be used in combination with the above-mentioned coating layer, if necessary. Furthermore, before applying the polyvinylidene chloride resin, the surface of the polyolefin film to be applied can be subjected to a corona treatment, and an anchor coat layer can also be provided. (Actions and Effects) The coated polyolefin film of the present invention has the following properties:
Because the heat shrinkage stress at 120℃ and the heat shrinkage rate at 135℃ are limited, the heat shrinkage is moderate in the temperature range (110-170℃) where it is heat-sealed in high-speed automatic packaging machines, and therefore, Even when the packaging method is subjected to localized high-temperature and short-term heat action, there are no heat shrinkage wrinkles and the finished product is good. The effects of the present invention are summarized below. A: When a tear tape is layered on a part of the film of the present application and the entire surface of the tape is heat-sealed (tape-sealed) at high temperature for a short period of time, no heat shrinkage wrinkles occur in the tape-sealed portion, and no curling occurs. It can be prevented. B When packaging uniformly shaped objects such as cassette tape cases at high temperatures and for short periods of time,
Heat-shrinkage wrinkles do not occur in the heat-sealed parts of the bottom and body, and bagginess can also be prevented. C Due to the effects of A and B above, the process of adhering the tear tape to the film of the present application and the process of packaging using the film of the present application with the tear tape are integrated.
High-speed automation is possible. The present invention will be explained below using examples. The method for measuring the physical properties of the film shown in the Examples is as follows. 1 Heat shrinkage stress A sample of 15 mm x 100 mm was fixed under tension with clips at the top and bottom, and a measuring device (manufactured by Koa Shokai) with a strain gauge (Toyo Baldwin, for 1000 g) connected to the upper end and a recorder were used. Connect the sample in this state to a glycerin bath at 120℃ for 1 hour.
Immersed for seconds. The behavior at this time was recorded on a recorder, and the heat shrinkage stress (g/15 mm width) was measured. 2 Heat shrinkage rate during heat sealing Draw two marked lines on a 50 mm x 150 mm sample with a distance of 100 mm, length 300 mm, width 10 mm.
With bar type heat sealer, temperature 135
℃, crimping pressure 10g/ ^cm3 , crimping time 0.25 seconds, after crimping the bar so that it spans the two marked lines, measure the distance (mm) between the marked lines after crimping, and then The thermal shrinkage rate was calculated using the formula. Heat shrinkage rate (%) = 100mm-mm/100mm×100 Example 1 Both sides of the biaxially stretched polypropylene film shown in Table 1 were corona treated (wet tension 38 dynes/
cm) and then 10 parts of Coronate L (Japan Polyurethane, 75%) and Byron 30S (Toyobo, 30%).
After coating with a gravure roll using a mixed solution of 10% ethyl acetate and toluene as an anchor layer at a coating amount of 0.3 g/ ^m2 ,
Dry at 90°C for 10 seconds. Next, the following polyvinylidene chloride resin emulsion (concentration: 40%) was used as a top layer and coated with an air knife at a density of 3 g/m ² , followed by drying at 90° C. for 10 seconds. Further, the same operation as above was performed to obtain a biaxially stretched polypropylene film coated with polyvinylidene chloride resin on both sides. Next, it was aged at 40°C for 48 hours and its suitability for packaging was evaluated. Characteristics and evaluations of the above-obtained coated film were carried out, and continuous packaging tests were carried out using this film to make audio cassette tape cases using a high-speed automatic packaging machine.
The results are shown in Table 1. As can be seen from the results, the suitability for high-speed automatic packaging and the finish of the heat-sealed portion were also good, and the effects of the present invention were clear. Top coating agent formulation Polyvinylidene chloride resin emulsion (solid content 50%) 100 parts Silica fine powder 0.25 parts Parafine wax (solid content 30%, mp60℃) 4.0 parts Quaternary ammonium salt (solid content 60%) 1.0 parts comparison Examples 1 to 2 In the same manner as in Example 1, biaxially oriented polypropylene films having both sides of the original biaxially oriented polypropylene film coated with polyvinylidene chloride resin shown in Table 1 were produced. The properties of the obtained coated film were evaluated and a continuous packaging test was conducted in the same manner as in Example 1. The results are shown in Table 1. As can be seen from these results, it can be seen that when a film that does not belong to the present invention is used, the suitability for high-speed automatic packaging and the packaging condition are inferior.

【table】

[Table] Comparative Example 3 As a base film, the heat shrinkage rate at 50℃ is
0.78% horizontally 0.51%, heat shrinkage rate at 120°C vertically 4.9% horizontally
A polyvinylidene chloride resin-coated OPP film was produced in the same manner as in Example 1 except that an 8.1% OPP film was used. Its performance is shown in Table 2. When the obtained coated OPP film was used for high-speed automatic packaging of curry roux in paper cases, it stopped due to curling at the tape sealing part, and
Excessive heat shrinkage during heat sealing of the opening, bottom, and body caused wrinkles, poor running properties of the package, and frequent stoppages of the packaging machine.

【table】

[Table] The heat shrinkage rates at 120°C and 50°C were measured as follows. Heat shrinkage rate at 120°C Draw a marked line approximately at the center of the 100 mm x 100 mm sample in the vertical and horizontal directions, and measure the distance between the marked lines in the vertical and horizontal directions using a caliper (omm). This sample was left in an oven at 120°C for 15 minutes, taken out, measured again (mm), and the thermal shrinkage rates in the vertical and horizontal directions were calculated using the calculation method below. Thermal shrinkage rate (%)=o-/o×100 Heat shrinkage rate at 50°C Thermal shrinkage rate was determined in the same manner as in the case of 120°C, except that the measurement was performed after being left in an oven at 50°C.

Claims (1)

[Claims] 1 The heat shrinkage stress at 120°C for 1 second is 5 to 50g/15mm width in the vertical direction and 10 to 100g/15mm width in the horizontal direction, and the heat shrinkage rate during heat sealing at 135°C for 0.25 seconds is vertical and Both horizontally 0.5~
A heat-sealable polyvinylidene chloride resin-coated polyolefin film for high-speed automatic packaging characterized by a 2.5% content.