JP3317475B2 - Polymethylpentene sheet for perishables, container for keeping freshness, and method of transporting perishables - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a container for keeping freshness which is excellent in the balance of physical properties such as sealability, transparency and gas permeability, and a polymethylpentene sheet which is excellent in heat sealing and which is used as a lid sheet in this container. And a method of transporting fresh products using the same.

[0002]

2. Description of the Related Art Polymethylpentene has heat resistance, transparency,
It can be formed into a sheet having excellent gas permeability. However, it is known that polymethylpentene has a high melting point and excellent heat resistance, but has poor heat sealing.
For example, JP-A-5-96690 and JP-A-7-6092
No. 1 describes that the problem is solved by further laminating a resin layer having good heat sealability on polymethylpentene.

[0003]

However, in such a method in which a resin layer having good heat sealability is further laminated and used, depending on the fresh product used, the excellent transparency and gas inherent in polymethylpentene are inherently obtained. In some cases, the transparency cannot be sufficiently exhibited. Further, the lamination as described above requires a lot of man-hours, and it is difficult to collect and reuse the laminated materials of different types.

[0004]

Means for Solving the Problems The present invention has been made as a result of intensive studies to solve the above problems, and as a result, has been made to improve the heat sealability of polymethylpentene which is excellent in heat resistance, transparency and gas permeability. In particular, focusing on improving the surface wetting, the contact angle, which is one of the indices indicating this wetting, is 60 ° to 7 ° C when measured using water at a temperature of 25 ° C.
It has been found that only a polymethylpentene sheet having a specific value of 5 ° exhibits excellent heat sealing properties with a polyester resin.

According to a first aspect of the present invention, a contact angle measured using water at a temperature of 25 ° C. is 60 °.
To 75 °, and exhibit excellent heat sealing properties with the polyester resin. In particular, the means for setting the contact angle to 60 ° to 75 ° is corona. It is preferable that the contact angle is measured by using water at a temperature of 25 ° C. on only one side of the polymethylpentene sheet, and the contact angle is 60 ° to 75 °. It is preferred that

According to a second aspect of the present invention, a polymethylpentene sheet according to any one of the first to third aspects is used as a lid sheet in a container body having a flange made of a polyester resin. A freshness holding container characterized in that the flange portion of the container body and the sheet are heat-sealed, wherein the lid sheet made of a polymethylpentene sheet is securely attached to the container body made of a polyester resin. Heat sealable.

According to a third aspect of the present invention, as described in claim 5, after a fresh product is put in a container body with a flange made of a polyester resin, a polymethylpentene sheet is used as a lid sheet, It is characterized in that it is transported after heat sealing the flange portion of the main body and the sheet, and is suitable for maintaining freshness, and particularly suitable for transporting vegetables, fruits and flowers according to the sixth aspect.

[0008]

Next, a preferred embodiment of the present invention will be described. First, the polymethylpentene used in the present invention is a homopolymer of poly-4-methyl-1-pentene or a copolymer with another α (alpha) -olefin. Here, α-olefin means ethylene, propylene, 1-butene, 1-hexene, 1-octene,
1-decene, 1-tetradecene, 1-octadecene, 1
Olefins having 2 to 30 carbon atoms, such as -hexadecene, 1-dodecene and 1-tetradecene, each of which can be used alone or in combination of two or more. However, when a copolymer of poly 4-methyl-1-pentene and α-olefin is used, poly 4-methyl-1-pentene is used.
A copolymer mainly composed of poly 4-methyl-1-pentene containing pentene of 80 mol% or more is preferable. The most preferred is a homopolymer of poly-4-methyl-1-pentene from the viewpoint of transparency, gas permeability, heat sealability and the like.

[0009] Polymethylpentene is formed into a sheet by a method such as extrusion. The thickness of the sheet is not particularly limited, but a thickness of about 0.03 to 1 mm can be preferably used. The sheet thus obtained was subjected to a corona discharge treatment, and the contact angle measured using water at a temperature of 25 ° C. was 60 °.
Treat the polymethylpentene sheet to ７５75 °. Here, the corona discharge treatment, using a known corona discharge treatment device such as a vacuum tube method, thyristor method,
For example, the treatment is performed by applying a gap of preferably about 0.2 to 5 mm between the discharge electrode and the sheet and applying an applied voltage of 0.1 to 50 kV.

The contact angle of the treated polymethylpentene sheet measured using water at a temperature of 25 ° C. is 60 ° to 7 °.
Must be 5 °. With a polymethylpentene sheet having a contact angle of more than 75 °, sufficient sealing strength cannot be obtained when heat sealing with a polyester resin. On the other hand, if the contact angle is less than 60 °, when the polymethylpentene sheet is wound into a roll, the sheets are likely to be blocked and stuck together, and the sealing strength at the time of heat sealing is undesirably reduced. Furthermore, in order to reliably prevent such sheets from blocking each other, it is most preferable to treat only one surface of the polymethylpentene sheet so as to have a contact angle in the above range.

The polyester resin used for molding the container body with a flange used in the present invention is a linear polyester of a polycondensate of an aromatic dicarboxylic acid component and a diol component, and specifically, polyethylene terephthalate, polybutylene terephthalate, Polybutylene terephthalate elastomer, amorphous polyester, polycyclohexane terephthalate and the like, alone or these resins,
A plurality of these resins may be used as a mixture, and a modified resin containing 50% by weight or more of these resins may be used.

Further, these containers may be formed by foaming the above resin or in an unfoamed state. The polymethylpentene sheet treated so that the contact angle measured using water at a temperature of 25 ° C. becomes 60 ° to 75 ° can improve the sealing strength surprisingly, especially when heat-sealed with a polyester resin. it can.

Therefore, as shown in FIG. 1, after the fresh product is put into the container body 1 with the flange 10 made of a polyester resin, the polymethylpentene sheet according to any one of claims 1 to 3 is used as a lid sheet. When the fresh product is transported using the flange portion 10 and the lid sheet 2 after being heat-sealed 3 and transported, the seal may be detached due to vibration during transport. And can be suitably transported. As the above-mentioned fresh products, leafy vegetables, fruits, flowers, etc., especially large leaves, cut cabbage, lettuce, etc., with a large amount of breathing, easily wilted vegetables, fruits requiring freshness, as well as flowers such as carnations, roses, etc. are transported. It is effective in that case, and the number of days for keeping freshness can be greatly extended.

In the embodiment, the lid sheet can be heat-sealed not only to the illustrated container body but also to various container bodies.

[0015]

【Example】

(Experimental Example 1) Homopolymer of poly-4-methyl-1-pentene (density 0.833 g / cm ³ : MFR 26 g / 10 min, measured according to ASTM D1505, ASTM D1)
(Measured at 260 ° C. according to 238) at a cylinder temperature of 300 ° C. and a mold temperature of 305 ° C. to form a sheet having a thickness of about 0.05 mm.

The sheet has a contact angle of 71 measured using water at a temperature of 25 ° C. (surface tension 74.14 dyn / cm).
°, 67 °, 65 °, 63 °, and 56 ° were subjected to corona discharge treatment. The contact angle of the poly (4-methyl-1-pentene) homopolymer sheet not subjected to the corona discharge treatment was 90 ° or more. The measuring method of the contact angle is
Contact angle measuring device (manufactured by Elma Corporation: Contact angle measuring device G-1)
-1000 type) using the above-mentioned sheet by the liquid point method. In addition, distilled water at 25 ° C. was used for the measurement, and the appropriate amount of the solution was 0.0035 cc. Next, the heat seal strength was measured. As a measurement sample, the above-mentioned sheet was used as a lid sheet, polyethylene terephthalate and a heat-sealing machine were used, which were heated at a heating temperature of about 270 ° C. for about 6 seconds and heat-sealed to a seal width of 4.0 mm to measure heat seal strength. Sample. This is J
According to IS-Z-1711, the test speed is 500 mm /
The maximum load point was measured under the test conditions for minutes. The above results are shown below. [Table 1] Contact angle Maximum load point Evaluation of seal strength (゜) (kgf) Polymethylpentene 90 °> No adhesion × (No corona discharge treatment) Polymethylpentene 71 ° 0.83 ○ (Line speed 5 m / min.) , Applied voltage 0.3 kV) polymethylpentene 67 ° 0.92 ○ (line speed 5 m / min, applied voltage 0.6 kV) polymethylpentene 65 ° 0.90 ○ (line speed 5 m / min, applied voltage 0.9 kV) polymethyl Penten 63 ° 0.50 ○ (Line speed 5m / min, applied voltage 1.2kV) Polymethylpentene 56 ° 0.21 × (Line speed 5m / min, applied voltage 2.1kV) (Experimental example 2) Next, from polyethylene terephthalate A non-foamed tray-type container with a flange is formed, and large leaves, which are representative of vegetables that have a good breathability and are easily wilted, are freshly prepared. After inserting 0 sheets, using a polymethylpentene sheet (having a contact angle of 67 ° described above) as a lid sheet, 10 samples were obtained by heat-sealing the flange portion and the sheet at a heating temperature of about 275 ° C. Prototype made.
In the prototype, the polymethylpentene sheet covering the upper part of the container showed good transparency, so that a good one in which the state of the large leaf inside could be clearly seen was obtained.

The prototype was transported from Nagoya to Nara by truck under refrigerated conditions at 8 ° C. After transport, when stored under the same refrigerated conditions of 8 ° C., the lid sheet made of polymethylpentene sheet and the flange portion of the tray-type container were well sealed, and the large leaves were withered for about 20 days thereafter.
It was confirmed that it could be stored well without discoloration. (Experimental Example 3) A tray-type container with a flange was formed using a foamed sheet (trade name: Cellpet, manufactured by Sekisui Chemical Co., Ltd.) made of polyethylene terephthalate.

After the large leaves were put into this, ten samples were heat-sealed in the same manner as above using a polymethylpentene sheet (having a contact angle of 65 ° described above) as a lid sheet. In the prototype, the polymethylpentene sheet covering the upper part of the container showed good transparency, so that a good one in which the state of the large leaf inside could be clearly seen was obtained. The prototype was transported from Nagoya to Nagoya by truck under refrigerated conditions of 8 ° C and stored under refrigerated conditions under the same conditions. As a result, the lid sheet made of polymethylpentene sheet and the flange of the tray-type container were sealed well. It was confirmed that the large leaves could be stored well without wilting or discoloration for about 20 days thereafter. Comparative Example 1 Ten samples were heat-sealed in the same manner as in Experimental Example 2 except that a sheet not subjected to corona discharge treatment was used as a polymethylpentene sheet. However, none of these samples could be heat-sealed satisfactorily and they were stored and stored at 8 ° C. under refrigeration conditions, but withered in about 5 days.

[0019]

According to the present invention, the heat sealability of polymethylpentene having excellent heat resistance, transparency and gas permeability can be improved. In particular, when the contact angle, which is one of the indices indicating this wetting, is measured using water at a temperature of 25 ° C., 60 ° to 7 °.
The sheet having a specific value of 5 ° can exhibit excellent heat sealing properties with the polyester resin, and the lid sheet made of the polymethylpentene sheet is heated in a container with a flange made of the polyester resin. By using it in a sealed state, it is possible to transport easily withering vegetables such as large leaves, cut cabbage and lettuce, wilted vegetables, fruits and flowers that require freshness, and significantly extend the number of days for keeping freshness. Can be.

Further, since different kinds of materials are not laminated, it is easy to collect and reuse them after use.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a flanged container using a sheet according to the present invention as a lid sheet after heat sealing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container 10 Flange part 2 Lid sheet 3 Heat seal part

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Fumitoshi Nakamura 3-11-5 Nihonbashi Honcho, Chuo-ku, Tokyo Inside RIKEN Vinyl Industry Co., Ltd. (72) Inventor Hirojiro Suga 6-chome, Waki, Waki-cho, Kuga-gun, Yamaguchi Prefecture 1-2 No.2 within Mitsui Petrochemical Industry Co., Ltd. (72) Takashi Nakahara 1-2-2 Waki, Waki-machi, Kuga-gun, Yamaguchi Prefecture Inside Mitsui Petrochemical Industry Co., Ltd. (72) Inventor Kazuo Tajima Koga-shi, Ibaraki Kitamachi 4-27-604 (72) Inventor Tatsuo Murai 400-1 Oshinsaka, Sakurai-shi, Nara Prefecture (72) Inventor Toshiro Maekawa 3-5-6 Sakyo, Nara-shi (72) Inventor Minoru Fujishima Heigunmachi, Ikoma-gun, Nara Prefecture 2-8-11-201 Nishinomiya (56) References JP-A-7-62308 (JP, A) JP-A-3-65338 (JP, A) JP-A 9-270361 (JP, A) JP-A-2 -282080 (JP, A) Special JP-A-5-162782 (JP, A) JP-A-7-87884 (JP, A) JP-A-1-24066 (JP, B2) JP-A-8-15909 (JP, B2) JP-A-62-58706 (JP) , B2) Patent 3019394 (JP, B2) Patent 3230853 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B65D 81/24 B65D 65/02 B65D 85/50

Claims (6)

(57) [Claims] 1. A polymethylpentene sheet for perishable goods, wherein the contact angle measured using water at a temperature of 25 ° C. is 60 ° to 75 °. 2. The polymethylpentene sheet for perishable goods according to claim 1, wherein the means for setting the contact angle to 60 ° to 75 ° is performed by corona discharge treatment. 3. The method according to claim 1, wherein only one side of the polymethylpentene sheet is
The contact angle measured using water at a temperature of 25 ° C. is 60 ° to 7 °.
The polymethylpentene sheet according to claim 1, wherein the angle is 5 °. 4. A container body with a flange made of a polyester resin , wherein the polymethylpentene sheet for perishable goods according to any one of claims 1 to 3 is used as a sheet for a lid, and a flange portion of the container body is provided. A freshness preserving container characterized by being heat-sealed with a sheet. 5. A fresh product is placed in a flanged container body made of a polyester-based resin, and the polymethylpentene sheet is used as a lid sheet, and the flange portion of the container body and the sheet are heat-sealed. A method for transporting perishable goods, characterized by being transported later. 6. The method according to claim 5, wherein the fresh products are vegetables, fruits and flowers.