JP2865027B2 - Heat shrinkable package of polypropylene resin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable package obtained by covering an object to be packaged with a heat-shrinkable polypropylene resin film and then heat-shrinking the polypropylene resin film. The present invention relates to a heat-shrinkable package provided with a sealing portion formed by a method.

[0002]

2. Description of the Related Art A heat-shrinkable package in which an object to be packaged is roughly wrapped with a film for packaging and passed through a heating tunnel to thermally shrink the film for packaging, and the object to be packaged is tightly packaged with the film. For example, it is mainly used in a package in which a lightweight material such as a cup noodle or a lactic acid beverage is to be packaged.

[0003] As a packaging film in this type of heat-shrinkable package, a polypropylene-based resin film having excellent functions such as transparency, gloss and moisture resistance is used.

[0004] In obtaining a heat-shrinkable package using a heat-shrinkable polypropylene resin film, a vertical seal is formed by a bar seal or a cut seal method, and a horizontal seal is formed by a fusing seal method. Has formed.

[0005] By the way, as the thickness of the polypropylene resin film used as the above-mentioned heat shrink wrapping film becomes thinner, or as the packing speed in the heat shrink wrapping process is increased, the strength of the horizontal seal portion becomes poor. It was way. In other words, a sealing defect such as a hole being generated in the horizontal seal portion during fusing and sealing at the time of heat shrink wrapping, or a hole being generated in the horizontal sealing portion when passing through the heating tunnel even if the sealing is accurately performed during fusing and sealing. Began to occur.

The poor sealing of the fusing seal portion is caused by the fact that the heat-shrinkable polypropylene resin film used as a packaging film has a low fusing seal strength and a narrow fusing seal temperature range.

As a heat-shrinkable polypropylene resin film having a high fusing seal strength, a heat-shrinkable polypropylene resin film using a polypropylene resin having a small melt index as a film forming material is known. A heat-shrinkable film made of a polypropylene-based resin cannot be produced at a high speed because of a small discharge amount of the film-forming raw material at the time of forming the raw film because the polypropylene-based resin as a film-forming material has a high melt viscosity. In addition, there is a drawback that a highly transparent film cannot be obtained because the surface of the molded film is roughened.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a high heat-shrinkable polypropylene resin film having high transparency and high mechanical strength, as well as high heat-shrinkability. A heat-shrinkable package wrapped with a heat-shrinkable polypropylene-based resin film, which is provided with a fusing seal portion having high seal strength even when the speed of the heat-shrinkable packaging step for obtaining the heat-shrinkable package is increased. Another object of the present invention is to provide a heat-shrinkable package of such a polypropylene resin film.

[0009]

The above objects can be attained by a heat-shrinkable package of a polypropylene resin film of the present invention having the following constitution. That is, the present invention provides 98.5 to 90.0% by weight of propylene with 1.5% by weight.
After wrapping an object to be packaged with a heat-shrinkable polypropylene-based resin film obtained by stretching a film of a random propylene-based copolymer resin with ethylene and / or butene in an amount of up to 10.0% by weight, and then fusing. A heat-shrinkable package of a polypropylene resin film obtained by forming a seal portion by a sealing method and further heat-shrinking the heat-shrinkable polypropylene resin film, wherein the heat-shrinkable polypropylene resin film is melted by DSC. Difference (Tm) between peak temperature (Tm) and crystallization peak temperature (Tc)-
(Tc) is a heat-shrinkable package of a polypropylene resin film having a temperature in the range of 30 to 40 ° C.

The present invention is also obtained by subjecting a random propylene copolymer resin film formed from 98.5 to 90.0% by weight of propylene and 1.5 to 10.0% by weight of ethylene to a stretching treatment. After the package is wrapped with the heat-shrinkable polypropylene resin film, a sealing portion is formed by a fusing seal method, and the heat-shrinkable polypropylene resin film is further heat-shrinked. The difference (Tm) between the melting peak temperature (Tm) and the crystallization peak temperature (Tc) of the heat-shrinkable polypropylene resin film by DSC of the heat-shrinkable polypropylene resin film.
(Tc) is a heat-shrinkable package of a polypropylene resin film having a temperature in the range of 30 to 40 ° C.

Further, the present invention relates to 98.5 to 90.0% by weight.
After covering a packaged object with a heat-shrinkable polypropylene-based resin film obtained by stretching a film of a random propylene-based copolymer resin with propylene and 1.5 to 10.0% by weight of butene, A heat-shrinkable package of a polypropylene-based resin film formed by heat-shrinking the heat-shrinkable polypropylene-based resin film, wherein the heat-shrinkable polypropylene-based resin film is heat-shrinkable. (Tm) between melting peak temperature (Tm) and crystallization peak temperature (Tc)
(Tc) is a heat-shrinkable package of a polypropylene resin film having a temperature in the range of 30 to 40 ° C.

In a random propylene copolymer resin film composed of propylene, ethylene and / or butene, a polypropylene resin film having a total amount of ethylene and butene of less than 1.5% by weight produces a heat-shrinkable film. In this case, it is not easy to form a raw film, and the obtained propylene-based resin film also has a low heat shrinkage.

In this random propylene copolymer resin film comprising propylene and ethylene and / or butene, the total amount of ethylene and butene is 10.0.
If the content is more than 10% by weight, a film having a sufficient heat shrinkage ratio is obtained, but stickiness tends to occur and blocking tends to occur, resulting in poor handling.

In the heat-shrinkable polypropylene resin film package of the present invention, the melting peak temperature (Tm) and the crystallization peak temperature (Tc) of the heat-shrinkable polypropylene resin film for covering the object to be packaged by DSC are measured by DSC. )
Is a temperature measured according to JIS K7121, and is a numerical value obtained by the following method.

That is, a 5 mg sample was heated to 180 ° C. at a rate of 10 ° C./min and maintained at 180 ° C. for 10 minutes, and then cooled to 10 ° C. at a rate of 10 ° C./min.
Then, the crystallization peak temperature (Tc) is determined. Then, after being kept at 40 ° C. for 10 minutes, 10 ° C.
The melting peak temperature (Tm) is determined by increasing the temperature to 180 ° C. at a rate of temperature increase per minute.

Here, the difference (Tm)-(Tc) between the melting peak temperature (Tm) and the crystallization peak temperature (Tc) of the heat-shrinkable polypropylene resin film by DSC is 30 ° C.
If it is smaller, the fusing seal temperature range when forming the seal portion by the fusing sealing method becomes wider, but the film formation becomes unstable because the crystallization of the polypropylene resin when obtaining the raw film is too fast. As a result, a stable raw film cannot be obtained due to an increase in thickness unevenness.

If the difference (Tm)-(Tc) between the melting peak temperature (Tm) and the crystallization peak temperature (Tc) of the heat-shrinkable polypropylene resin film by DSC exceeds 40 ° C., the fusing sealing method is used. The temperature range of the fusing seal at the time of forming the seal part becomes narrower, the thread is pulled at the time of fusing sealing, the cutting at the fusing sealing becomes worse, and the fusing seal strength becomes weak because the fusing seal part becomes thinner There are drawbacks such as becoming.

By mixing a propylene homopolymer with a random propylene copolymer resin composed of propylene and ethylene and / or butene, a so-called stiff film can be obtained. Although the melting peak temperature (Tm) increases, the crystallization peak temperature (Tc) does not change. For this reason, when a propylene homopolymer is added, the difference (Tm) − (Tc) between the melting peak temperature (Tm) and the crystallization peak temperature (Tc) by DSC easily exceeds 40 ° C. Propylene and ethylene and / or propylene homopolymer so that (Tm) − (Tc) of the propylene-based copolymer resin film does not exceed 40 ° C.
Alternatively, the amount of the propylene homopolymer added to the random propylene copolymer resin with butene must be kept small.

The difference (Tm)-(Tc) between the melting peak temperature (Tm) by DSC and the crystallization peak temperature (Tc) is 4
In order to obtain a heat-shrinkable polypropylene resin film at a temperature of 0 ° C. or lower, the type of the polypropylene resin as a film forming material is selected, or talc, sodium benzoate, dibenzylidene sorbitol, dimethyl Means such as blending a nucleating agent such as benzylidene sorbitol can be used.

The heat-shrinkable polypropylene resin film used for the heat-shrinkable package of the polypropylene resin film of the present invention may contain additives usually incorporated in the polypropylene resin film, such as an antioxidant and an antistatic agent. , Even if the necessary amount of lubricant, blocking agent, etc. is blended,
As a result, the fusing sealability does not deteriorate.

[0021]

EXAMPLES The specific structure of the heat-shrinkable polypropylene resin film package of the present invention will be described below with reference to examples, and the fusing seal characteristics of the polypropylene resin film used in the heat-shrinkable package will be described below. To mention.

Example 1 A random propylene copolymer resin containing 95.0% by weight of propylene and 5.0% by weight of ethylene (230 ° C.)
Melt index: 2.5 g / 10 min) 100 parts by weight, 0.45 part by weight of silica as an anti-blocking agent,
A film-forming raw material comprising 0.08 parts by weight of calcium carbonate and 0.05 parts by weight of talc was melted at 180 to 230 ° C. and extruded from a tubular die to form a diameter of 50 cm and a thickness of 2 cm.
A tube-shaped raw film of 50 μm was obtained.

This raw film is stretched 4.5 times in length and 4.5 times in width at 100 to 150 ° C. to have a thickness of 12 μm.
The heat-shrinkable polypropylene resin film (A) was obtained. This heat-shrinkable polypropylene resin film (A)
Has a melting peak temperature (Tm) of 137 ° C. and a crystallization peak temperature (Tc) of 102 ° C. by DSC.

Subsequently, a heat-shrinkable package made of a horizontal pillow package of cup noodles was obtained from the heat-shrinkable polypropylene-based resin film (A). Part) is 0.03
%, And the fusing seal strength was 3.0 kg / 25 mm.

Example 2 100 parts by weight of a random propylene copolymer resin (melt index at 230 ° C .: 2.0 g / 10 minutes) with 96.0% by weight of propylene and 4.0% by weight of butene, preventing blocking A film-forming material consisting of 0.3 parts by weight of silica, 0.1 parts by weight of calcium carbonate, and 0.05 parts by weight of talc as an agent was melted at 180 to 230 ° C., extruded from a tubular die, and molded to a diameter of 50 cm. Thickness 250
A μm tubular raw film was obtained.

This raw film is stretched 4.5 times in length and 4.5 times in width at 100 to 150 ° C. to have a thickness of 12 μm.
Was obtained as a heat-shrinkable polypropylene resin film (B). This heat-shrinkable polypropylene resin film (B)
Has a melting peak temperature (Tm) of 138 ° C. and a crystallization peak temperature (Tc) of 100 ° C. by DSC.

Subsequently, a heat-shrinkable package made of a horizontal pillow package of cup noodles was obtained from the heat-shrinkable polypropylene resin film (B). ) Is 0.05%
And the fusing seal strength was 3.5 kg / 25 mm.

Example 3 A random propylene copolymer resin comprising 94.0% by weight of propylene, 3.0% by weight of ethylene and 3.0% by weight of butene (melt index at 230 ° C .: 4.0)
g / 10 minutes) A film-forming material consisting of 100 parts by weight, 0.4 parts by weight of silica as an anti-blocking agent, 0.2 parts by weight of calcium carbonate, and 0.1 parts by weight of talc was mixed with 180 to 2 parts by weight.
It was melted at 30 ° C. and extruded from a tubular die to obtain a tubular raw film having a diameter of 50 cm and a thickness of 250 μm.

This raw film was stretched 4.5 times in length and 4.5 times in width at 100 to 150 ° C. to have a thickness of 12 μm.
Was obtained as a heat-shrinkable polypropylene resin film (C). This heat-shrinkable polypropylene resin film (C)
Has a melting peak temperature (Tm) of 137 ° C. and a crystallization peak temperature (Tc) of 103 ° C. by DSC.

Subsequently, when a heat-shrinkable package consisting of a horizontal pillow package of cup noodles was obtained with the heat-shrinkable polypropylene resin film (C), the fusing seal portion (horizontal seal portion) of the heat-shrinkable package was obtained. The defect occurrence rate was 0.02%, and the fusing seal strength was 4.0 kg / 25 mm.

Example 4 A random propylene copolymer resin containing 94.0% by weight of propylene and 6.0% by weight of ethylene (230 ° C.)
Melt index: 2.5 g / 10 min) from 90 parts by weight, 10 parts by weight of propylene homopolymer, 0.45 parts by weight of silica as a blocking inhibitor, 0.08 parts by weight of calcium carbonate, and 0.04 parts by weight of talc The formed film-forming material was melted at 180 to 230 ° C. and extruded from a tubular die to obtain a tubular raw film having a diameter of 50 cm and a thickness of 250 μm.

This raw film was stretched 4.5 times in length and 4.5 times in width at 100 to 150 ° C. to have a thickness of 12 μm.
Was obtained as a heat-shrinkable polypropylene resin film (D). This heat-shrinkable polypropylene resin film (D)
Has a melting peak temperature (Tm) of 139 ° C. and a crystallization peak temperature (Tc) of 101 ° C.

Subsequently, when a heat-shrinkable package consisting of a horizontal pillow package of cup noodles was obtained with the heat-shrinkable polypropylene resin film (D), the fusing seal portion (horizontal seal portion) of the heat-shrinkable package was obtained. The failure rate was 0.05%, and the fusing seal strength was 3.5 kg / 25 mm.

The melting peak temperature (Tm), the crystallization peak temperature (Tc), the melting peak temperature (Tm) and the crystallization peak of the heat-shrinkable polypropylene resin film used in Examples 1 to 4 were determined by DSC. The difference (Tm)-(Tc) from the temperature (Tc), the defect occurrence rate of the fusing seal portion (horizontal seal portion) in the heat shrinkable package made of the horizontal pillow package of cup noodles, and the seal strength of the fusing seal portion ( (Table 1).

[0035]

[Table 1]

COMPARATIVE EXAMPLE 1 A random propylene copolymer resin containing 94.0% by weight of propylene and 6.0% by weight of ethylene (230 ° C.)
(Melt index: 2.5 g / 10 min) 100 parts by weight and 0.45 parts by weight of silica as a blocking inhibitor were melted at 180 to 230 ° C. and extruded from a tubular die to form a diameter. 50cm, thickness 25
A tube-shaped raw film of 0 μm was obtained.

This raw film was stretched 4.5 times vertically and 4.5 times horizontally at 100 to 150 ° C. to a thickness of 12 μm.
Was obtained as a heat-shrinkable polypropylene resin film (E). The melting peak temperature (Tm) of this film (E) by DSC was 136 ° C., and the crystallization peak temperature (Tc) was 94.
° C.

Subsequently, a comparative heat-shrinkable package consisting of a horizontal pillow package of cup noodles was obtained from the heat-shrinkable polypropylene resin film (E). The defect occurrence rate of the fusing seal portion (horizontal seal portion) of the obtained heat shrinkable package was 1.0%. Further, the fusing seal strength of this heat shrinkable package is 2.5 kg / 2.
5 mm.

Comparative Example 2 A commercially available heat-shrinkable film (F) of a random propylene copolymer resin of ethylene and propylene having a thickness of 12 μm
In the same manner as in Comparative Example 1, a heat-shrinkable package for comparison consisting of a horizontal pillow package of cup noodles was obtained.

Comparative Example 3 Using a commercially available heat-shrinkable film (G) having a thickness of 15 μm of a random propylene-based copolymer resin of ethylene, propylene and butene, in the same manner as in Comparative Example 1, the horizontal pillow packaging of cup noodles A heat-shrinkable package for comparison consisting of a body was obtained.

Comparative Example 4 A commercially available heat-shrinkable film (H) of a random propylene copolymer resin of ethylene and propylene having a thickness of 12 μm
In the same manner as in Comparative Example 1, a heat-shrinkable package for comparison consisting of a horizontal pillow package of cup noodles was obtained.

Comparative Example 5 A commercially available heat-shrinkable film (J) of a random propylene copolymer resin of ethylene and propylene having a thickness of 15 μm
In the same manner as in Comparative Example 1, a heat-shrinkable package for comparison consisting of a horizontal pillow package of cup noodles was obtained.

Melting peak temperature (Tm), crystallization peak temperature (Tc), melting peak temperature (Tm) and melting peak temperature of DSC of the heat-shrinkable film of the propylene copolymer resin used in Comparative Examples 1 to 5 The difference (Tm)-(Tc) from the peak temperature (Tc) is shown in [Table 2].

In addition, the defect occurrence rate of the fusing seal portion (horizontal seal portion) of the heat-shrinkable package made of the horizontal pillow package of cup noodles of Comparative Examples 1 to 5 and the seal strength of the fusing seal portion (fusing seal) Strength) are also shown in [Table 2].

[0045]

[Table 2]

[0046]

The heat-shrinkable package of the polypropylene-based resin film of the present invention has excellent transparency and mechanical strength, like the conventional heat-shrinkable polypropylene-based resin film, and can be produced at high speed. A heat-shrinkable package wrapped with a heat-shrinkable polypropylene-based resin film, which has a high sealing strength even when the speed of the heat-shrinkable wrapping step for obtaining the heat-shrinkable package is increased. Is provided.

That is, the heat-shrinkable polypropylene resin film used in the heat-shrinkable polypropylene resin film of the present invention can be produced at a high speed, like the conventional heat-shrinkable polypropylene resin film. ,
It has excellent properties of transparency and mechanical strength, and is capable of forming a fusing seal portion having a high sealing strength, and further has a fusing seal temperature width when forming the fusing seal portion. Since it is a wide range of about 5 to 10 ° C., even if the speed of the heat shrink wrapping process for obtaining the heat shrink wrap is increased, the heat shrinkage of the polypropylene resin film provided with the fusing seal portion having high sealing strength is achieved. It becomes a package.

Therefore, according to the heat-shrinkable package of the polypropylene-based resin film of the present invention, even if the heat-shrinkable package is formed by high-speed packaging, there is no occurrence of poor sealing at the fusing seal portion and the seal strength. A heat shrinkable package having a high melting seal portion.

Further, according to the heat-shrinkable package of the polypropylene-based resin film of the present invention, since the heat-sealing temperature range for forming the heat-sealed portion in the heat-shrinkable package is wide, the heat-sealed portion is formed. It is easy to adjust the sealing temperature in the process.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI B29L 7:00 C08L 23:00 (56) References JP-A-6-57057 (JP, A) JP-A-5-309732 (JP) JP-A-8-291236 (JP, A) JP-A-6-240065 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08J 5/00-5/02, 5/12-5/22 B29C 61/06 C08F 210/06

Claims (3)

(57) [Claims] 1. A film of a random propylene copolymer resin comprising 98.5 to 90.0% by weight of propylene and 1.5 to 10.0% by weight of ethylene and / or butene is obtained by stretching. After wrapping the object to be packaged with the heat-shrinkable polypropylene-based resin film obtained, a sealing portion is formed by a fusing-sealing method, and the heat-shrinkable polypropylene-based resin film is further heat-shrinked. The difference (T) between the melting peak temperature (Tm) and the crystallization peak temperature (Tc) of the heat-shrinkable polypropylene resin film by DSC of the heat-shrinkable polypropylene resin film.
m)-(Tc) is in the range of 30 to 40 ° C., a heat-shrinkable package of a polypropylene resin film. 2. A heat-shrinkable film obtained by stretching a film of a random propylene copolymer resin comprising 98.5 to 90.0% by weight of propylene and 1.5 to 10.0% by weight of ethylene. After wrapping the object to be packaged with the conductive polypropylene resin film, a sealing portion is formed by a fusing seal method, and further the heat-shrinkable polypropylene resin film is heat-shrinked to form a heat-shrinkable polypropylene resin film. And the difference (Tm)-(Tc) between the melting peak temperature (Tm) by DSC and the crystallization peak temperature (Tc) of the heat-shrinkable polypropylene resin film is in the range of 30 to 40 ° C. A heat-shrinkable package of a polypropylene-based resin film, characterized in that: 3. Thermal shrinkage obtained by stretching a film of a random propylene-based copolymer resin with 98.5 to 90.0% by weight of propylene and 1.5 to 10.0% by weight of butene. After wrapping the object to be packaged with the conductive polypropylene resin film, a sealing portion is formed by a fusing seal method, and further the heat-shrinkable polypropylene resin film is heat-shrinked to form a heat-shrinkable polypropylene resin film. And the difference (Tm)-(Tc) between the melting peak temperature (Tm) by DSC and the crystallization peak temperature (Tc) of the heat-shrinkable polypropylene resin film is in the range of 30 to 40 ° C. A heat-shrinkable package of a polypropylene-based resin film, characterized in that: