JP2005289471A - Packaging film excellent in heat resistance and heat sealing capability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a packaging film excellent in heat resistance and heat sealing capability, which secures almost the same level of heat resistance and high elasticity as is with a conventional packaging film that is layer-constituted by dry-lamination, and is further excellent in heat resistance and heat sealing capability, which allows automatic filling and packaging at a high speed. <P>SOLUTION: The packaging film has a three-layer structure comprised of a sealant layer 3 made of L-LDPE, an intermediate layer 2 made of L-LDPE that has a higher density than the sealant layer, and a base film layer 1 made of biaxially oriented film, and is excellent in heat resistance and heat sealing capability. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a packaging film having excellent heat resistance and heat sealability.

  In recent years, from the viewpoint of food and beverage hygiene, when filling a packaging bag with food or beverage, filling and packaging of a high-temperature food or beverage that has been subjected to heat sterilization while maintaining the high-temperature state has been widely performed. It is coming. In addition, in order to meet the demands of consumers who want to eat warm foods and drinks at any time, food and drinks are actively developed assuming high temperature boiling when eating. And the demand for high heat resistance and high-strength packaging bags used in such applications is also growing rapidly, and it is compatible with high-speed filling packaging for mass production in response to the increased demand for food and drink products. There is also a need for the development of such packaging bags.

  Conventionally, as packaging bags used for filling high temperature liquids that have been heat sterilized, filled liquids and other high temperature boiling, etc., two layers using high-density plastic for the base film layer and sealant layer Structural packaging films are known. From the viewpoint of high heat resistance and high elasticity, it is generally known that a high-density film is superior to a low-density film as long as it is a film made of the same component plastic. For example, taking polyethylene as an example, high-density polyethylene (HDPE) is superior in the above properties to low-density polyethylene (LDPE).

  However, packaging films made of high-density plastics have low MI (melt index) values indicating heat flow suitability during heating due to their high density, and heat sealability (seal strength, low-temperature heat sealability, etc.) As a result, the heat supply to the sealant layer is insufficient for the demand for higher-speed automatic filling and packaging for liquids, liquids, etc., and in many cases, 20 m / min of the packaging film is used. It is difficult to ensure that proper heat sealing is applied to the packaging bag for automatic filling and packaging under exceeding traveling speed. Packaging is virtually impossible.

  On the other hand, a packaging film using a low-density plastic for the sealant layer can obtain high heat resistance and high stiffness by increasing the thickness of the sealant layer. However, when the thickness of the sealant layer is increased, it becomes difficult to perform an appropriate heat seal with a small amount of heat supplied, and there is a problem that it is impossible to cope with high-speed automatic filling packaging.

Based on the above, conventional double-layer packaging films using high-density plastic for the base film layer and sealant layer are compatible with high-speed automatic filling packaging, and have high heat resistance, high stiffness, and high heat sealability. There was a problem that it was impossible to provide a compatible packaging bag.
Japanese Patent Laid-Open No. 2003-205949 Japanese Patent Application No. 8-243814 JP-A-8-108507

  The present invention has been made with the object of solving the above-mentioned problems of the prior art, and the object of the present invention is to provide a conventional two-layer packaging using a high-density plastic for the sealant layer. Providing packaging film with excellent heat resistance and heat-sealability that is capable of automatic filling and packaging at high speeds exceeding 20 m / min while ensuring heat resistance and high stiffness equivalent to film for packaging It is in.

  The present invention is based on the premise that the L-LDPE layer exhibits sufficient heat resistance, and the L-LDPE layer contributes mainly to the portion that contributes to the achievement of high stiffness and the excellent heat sealability. It was made by separating the functions into parts. The packaging film excellent in heat resistance and heat sealability according to the present invention includes a sealant layer made of L-LDPE, an intermediate layer made of L-LDPE having a higher density than the sealant layer, and a biaxially stretched film. It has an extruded three-layer laminated structure with a base film layer.

Here, the density of L-LDPE constituting the intermediate layer is 0.920 g / cm ³ or more and 0.940 g / cm ³ or less, and the density of L-LDPE constituting the sealant layer is 0.900 g / cm ³ or more and 0.920. It is characterized by being less than g / cm ³ . Further, the density of the L-LDPE constituting the sealant layer is 0.900 g / cm ³ or more and 0.910 g / cm ³ or less.

  Further, the biaxially stretched film constituting the base film layer is formed of nylon film, polyethylene terephthalate film, ethylene-vinyl alcohol copolymer film or polyvinyl alcohol on which silica, alumina or the like is deposited or not deposited, The thickness is in the range of 10 μm to 30 μm.

  On the other hand, the thickness of the intermediate layer and the sealant layer are both in the range of 10 μm to 50 μm.

According to the present invention, a packaging bag having a three-layer structure having an intermediate layer made of L-LDPE having a higher density than the sealant layer between the base film layer and the sealant layer is manufactured from the film. It is possible to impart high stiffness to the bag and to effectively suppress the occurrence of wrinkles on the heat seal portion of the bag. Moreover, high heat resistance can be exhibited with respect to high temperature filling and high temperature boiling. Also, here, based on the high degree of elasticity provided by the intermediate layer, the total thickness of the packaging film can be reduced, yet high quality can be ensured, meeting the demand for thinner laminate films. Can do.
In addition, since this packaging film uses L-LDPE, which has a lower density than the intermediate layer, as the sealant layer, it is possible to perform an appropriate heat seal with a small amount of heat supply. It is possible to carry out the packaging as expected by sufficiently dealing with the above.

Here, the density of the L-LDPE used in the intermediate layer, be 0.920 g / cm ³ or more 0.940 g / cm ³ or less, it is preferable in ensuring a high waist degree and excellent durability.
That is, it tends to be insufficient Koshido is less than 0.920 g / cm ^3, exceeds 0.940 g / cm ^3, as a result of the waist is too strong, pinhole resistance of the packaging bag, the impact resistance decreases There is a risk.
In addition, as for L-LDPE which comprises an intermediate | middle layer, it is desirable to use what was manufactured using the metallocene catalyst.

The density of the L-LDPE used in the sealant layer, 0.900 g / cm ³ or more 0.920 g / cm less than ^3, be inter alia 0.910 g / cm ³ or less, on to achieve both heat resistance and heat sealability Is preferable. In other words, if it is less than 0.900 g / cm ³ , it is difficult to achieve sufficient heat resistance, and if it is 0.920 g / cm ³ or more, it becomes difficult to achieve an appropriate heat seal with a short heat seal time.

  By the way, when the base film layer made of the biaxially stretched film is formed of nylon film, polyethylene terephthalate film, ethylene-vinyl alcohol copolymer film or polyvinyl alcohol, the base film layer is made of nylon film, polyethylene terephthalate. When molded with a film, ethylene-vinyl alcohol copolymer film or polyvinyl alcohol, it improves the printing suitability of the printing bag, and heat resistance, waist strength, and gas barrier properties of the packaging bag. And pinhole resistance can be improved and each can be effectively applied.

  Further, by making the thickness of the base film layer within a range of 10 μm to 30 μm, it is possible to effectively impart barrier properties such as dimensional stability, transparency, cutability, heat resistance and gas of the packaging bag. .

That is, when the thickness is 10 μm, the packaging bag is easily broken, and the heat seal strength, pinhole resistance, and barrier properties such as gas cannot be improved.
On the other hand, if it exceeds 30 μm, it is difficult to perform an appropriate heat seal with a small amount of heat supplied, and it becomes impossible to sufficiently cope with high-speed automatic filling packaging.

  The thickness of the intermediate layer and the sealant layer is in the range of 10 μm to 50 μm. By doing so, it is possible to withstand high heat and high temperature filling (hot pack) and high temperature boil heat and still provide high heat seal strength. In addition, it is possible to perform an appropriate heat seal with a small amount of supplied heat, and sufficiently enable high-speed automatic filling packaging.

  On the other hand, if the thickness is 10 μm, sufficient stiffness cannot be obtained, and it becomes difficult to ensure a high texture. In addition, wrinkles and the like are likely to occur in the entire seal portion during automatic filling and packaging. If it exceeds 50 μm, it takes a long time for heat sealing, and high-speed automatic filling and packaging becomes difficult. Moreover, since the elasticity of a film becomes too high, it will become inferior to pinhole resistance. In addition, it is more preferable that it is 10 micrometers-less than 30 micrometers.

  FIG. 1 is an enlarged cross-sectional view showing an embodiment of the present invention. In the figure, reference numeral 1 denotes a base film layer, and reference numerals 2 and 3 denote an intermediate layer and a sealant layer, respectively. Here, each of the intermediate layer 2 and the sealant layer 3 can be sequentially laminated on the base film layer 1 with a required thickness using, for example, a tandem type extrusion laminating apparatus.

Base film layer 1, a silica, alumina or the like was deposited or not deposited, for example, a thickness in the range of 10 m to 30 m, density in the range of ^{1.10g / cm 3 ~1.50 g / cm} 3, a nylon film, It can be formed of a polyethylene terephthalate film, an ethylene-vinyl alcohol copolymer film, or polyvinyl alcohol.

The intermediate layer 2 is preferably a thickness in the range of 10 m to 50 m, density can be formed by ^{0.920g / cm 3 ~0.940 g / cm} 3 in the range of L-LDPE, the sealant layer 3, Preferably, it is formed by L-LDPE having a thickness in the range of 10 μm to 50 μm and a density in the range of 0.900 g / cm ^{3 to} 0.920 g / cm ³ , more preferably 0.900 g / cm ^{3 to} 0.910 g / cm ^3. be able to.

  The packaging film formed in this way has a well-known seal form such as a three-side seal or a four-side seal, which is applied to, for example, an automatic filling and packaging machine and filled with a liquid or other form of an object to be packaged. When it is made into a packaging bag, it exhibits excellent heat resistance under the action of the intermediate layer 2 and the sealant layer 3 as well as the base film layer 1, and in particular, it has a high elasticity under the action of the intermediate layer 2. Based on the expansion of the temperature range for proper heat sealing by the sealant layer 3, it provides excellent heat sealing performance, in other words, high heat sealing strength even when the film runs at high speed. be able to.

  Using an automatic filling and packaging machine (NT-DANGAN TYPE-III, manufactured by Nippon Seiki Co., Ltd.), packing and packaging with 45 g of water at temperatures of 30 ° C and 90 ° C in 110 mm x 75 mm packaging bags. When the change in the set temperature range of the transverse heat seal blade is obtained for each of the example film and the conventional film, an appropriate sheet seal can be obtained with the change in the filling speed, and the result shown in FIG. 2 is obtained. It was.

Here, in the example film, a base film layer is formed of a nylon film having a thickness of 15 μm and a density of 1.20 g / cm ³ , and an intermediate layer is formed of a thickness of 30 μm and a density of 0.920 g / cm ^{3 to} 0.940. formed in g / cm ³ of L-LDPE, a sealant layer, the thickness was 30 [mu] m, are those density formed by ^{0.900g / cm 3 ~0.920 g / cm} 3 of L-LDPE, conventional films, like the base film layer composed of biaxially stretched film, as the sealant layer, the thickness was 60 [mu] m, the L-LDPE having a density of ^{0.920g / cm 3 ~0.940 g / cm} 3, which was laminated by dry lamination is there.

According to FIG. 2 (a) showing hot water at 30 ° C., as shown by the broken line in the figure, the conventional film provides sufficient heat sealing for high speed running of the packaging film exceeding 20 m / min. In addition, the width of the upper limit value and the lower limit value of the transverse seal temperature at which the intended heat seal can be performed is shown for the film speeds lower than that of the example film indicated by the solid line in the figure. Since it becomes very narrow compared with it, it turns out that exact temperature control of the horizontal heat seal blade according to the running speed of a film becomes essential.
However, in the example film, sufficient heat-sealing is possible even at a speed exceeding 25 m / min, and a wide heelable temperature range of about 15 ° C. can be secured at that speed.
On the other hand, according to FIG. 2 (b) for hot water at 90 ° C., the conventional film also has a wide heelable temperature range, but still has a sufficient heat seal for a film speed exceeding 20 m / min. It is understood that it cannot be realized.
Thus, according to the example film, excellent heat-sealability can be exhibited even with respect to the traveling speed exceeding 25 m / min of the packaging film, and heat can be applied regardless of the temperature of the packaged object. A wide sealable temperature range can be secured to facilitate the temperature management of the transverse heat seal blade, and the risk of occurrence of seal failure can be greatly reduced.

  For each film described in Example 1, a heat sealer is used, and the film is folded between two upper and lower heat seal blades according to JIS Z 1707 for food packaging plastic film test method. When the set temperature of the heat seal blade was changed at 0.196 MPa and the heat seal time was 1 second to obtain the low temperature heat seal strength, the result shown in FIG. 3 was obtained.

  According to the result of FIG. 3 based on JIS Z 1707 and using a tensile testing machine (Tensilon RTM-1 manufactured by Orientec Co., Ltd.), the example film is a low temperature that does not have the same color as the conventional film. It can be seen that heat seal strength can be provided.

When the waist was measured for each of the same example film as in Example 1 and the conventional film, the result shown in FIG. 4A was obtained.
Note that the stiffness was determined by measuring the force when a pressing force was applied to the tip of a 15 mm × 17 mm strip film with one end fixed with a chuck and the film was bent.
According to the figure, it can be seen that the example film can exhibit the same stiffness as the conventional film.
In addition, the change of the elasticity when the thickness of each sealant layer of the example film and the conventional film was changed was as shown by a solid line and a broken line in FIG. 4B, respectively.
According to this, in any film, the stiffness increases substantially equally as the thickness of the sealant layer increases.

  Each of the example film described in Example 1 and the conventional film is charged into a rotating drum tester having a diameter of 250 mm with 45 g of water kept constant at 30 ° C. in a packaging bag of 110 mm × 75 mm in length and width. When the time for generating pinholes in each film when the drum was rotated at 60 rpm was measured, the results shown in FIG. 5A were obtained.

According to this, it can be seen that the pinhole resistance of the example film is equivalent to that of the conventional film.
Here, the pinhole generation time when only the thickness of the sealant layer of each film was changed was as shown in FIG. In the figure, a solid line has a configuration according to the present invention, and a broken line has a dryer laminated structure.

  In the film having the configuration according to the present invention, the presence of the intermediate layer made of L-LDPE having a higher density than the sealant layer, and thus the total thickness of the film is thinner than that of the dry laminated structure film. When the thickness is about 55 μm, the pinhole resistance is inferior to that of the dry laminated structure, but when the thickness is exceeded, it can be seen that the equivalent pinhole resistance can be exhibited.

  For each of the example film and the conventional film identical to Example 1, the film was folded in half with the sealant layer facing and sandwiched between clips and boiled at 90 ° C. for 30 minutes and at 30 ° C. for 30 minutes. Table 1 shows the result of examining whether the sealant layer was fused or not for each of the cases where boiling was performed for a minute.

  According to Table 1, it turns out that an Example film can exhibit the boil resistance more than a conventional film.

  INDUSTRIAL APPLICABILITY The present invention provides a packaging bag that enables a film speed that allows high-speed automatic filling and packaging while exhibiting heat resistance and stiffness, and can be used in fields such as food and beverage packaging and pharmaceutical packaging.

It is an expanded sectional view showing an embodiment of this invention. It is a graph which shows the change of the temperature range which can be sealed according to the filling speed. It is a graph which shows the relationship between heat seal temperature and low-temperature heat seal intensity | strength. It is a graph which shows a waist and a waist change. It is a graph which shows pinhole generation | occurrence | production time and its change.

Explanation of symbols

1 Base film layer 2 Intermediate layer 3 Sealant layer

Claims (5)

  Heat resistance and heat characterized by having a three-layer structure of a sealant layer made of L-LDPE, an intermediate layer made of L-LDPE having a higher density than the sealant layer, and a base film layer made of a biaxially stretched film Packaging film with excellent sealing properties. The density of L-LDPE constituting the intermediate layer is 0.920 g / cm ³ or more and 0.940 g / cm ³ or less, and the density of L-LDPE constituting the sealant layer is 0.900 g / cm ³ or more and 0.920 g / cm ^{3. The} packaging film having excellent heat resistance and heat sealability according to claim 1, wherein the packaging film is less than ³ . ^{3. The} packaging having excellent heat resistance and heat sealability according to claim 1, wherein the density of L-LDPE constituting the sealant layer is 0.900 g / cm ³ or more and 0.910 g / cm ³ or less. the film.   The biaxially stretched film constituting the base film layer is formed of nylon film, polyethylene terephthalate film, ethylene-vinyl alcohol copolymer film or polyvinyl alcohol, and the thickness of the base film layer is 10 μm to 30 μm. The packaging film excellent in heat resistance and heat sealability according to any one of claims 1 to 3. The packaging film excellent in heat resistance and heat sealability according to any one of claims 1 to 4, wherein both the intermediate layer and the sealant layer have a thickness of 10 µm to 50 µm.

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