JPH09290864A - Polymethylpentene sheet, freshness-retaining container and transportation method of perishables - Google Patents

Abstract

PROBLEM TO BE SOLVED: To bring out the heat-sealing property of polyester resin, by using polymethylpentene sheet having a specified index showing the wettability of the surface. SOLUTION: This applied polymethylpentene is an independent polymer of poly 4-methylpentene-1 or a copolymer with other α-olefin and produced to form sheets by an extruding method. The extruded sheet is applied with a corona discharge treatment to become 60-75 degrees in the contact angle measured with water of 25 deg.C. It is preferable to execute this treatment for only one side face. The polymethylpentene sheet processed in this treatment is used for the cover sheet 2. After perishables have been contained in the container body 1 with a flange 10 made of polyester resin, the flange 10 and the cover sheet 2 are sealed 3 together with heat. Then, it is used for transportation of perishables. In this way, the sealing material does not get out of place owing to vibration or the like during the transportation.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Polymethylpentene has heat resistance, transparency,
It can be formed into a sheet having excellent gas permeability. However, while polymethylpentene has a high melting point and excellent heat resistance, it is known that heat sealing is not good.
For example, JP-A-5-96690 and JP-A-7-6092.
No. 1 describes that a resin layer having a good heat-sealing property is further laminated on polymethylpentene to solve the problem.

[0003]

However, in such a method of further laminating a resin layer having a good heat-sealing property, depending on the fresh product to be used, excellent transparency and gas inherent to polymethylpentene can be obtained. The transparency may not be fully exhibited. Further, it takes a lot of man-hours to stack the layers as described above, and it is difficult to collect and reuse the stacked layers of different materials.

[0004]

DISCLOSURE OF THE INVENTION As a result of intensive studies to solve the above problems, the present invention aims to improve the heat-sealing property of polymethylpentene which is excellent in heat resistance, transparency and gas permeability. In particular, focusing on improving the wetting of the surface, the contact angle, which is one of the indexes showing this wetting, is 60 ° to 7 when measured using water at a temperature of 25 ° C.
It was found that only a polymethylpentene sheet having a specific numerical value of 5 ° exhibits excellent heat sealability with a polyester resin and has been completed.

According to a first aspect of the present invention, as described in claim 1, the contact angle measured using water at a temperature of 25 ° C. is 60 °.
It is characterized in that the contact angle is 60 ° to 75 ° and exhibits excellent heat-sealing properties with the polyester resin. Particularly, as in claim 2, the means for setting the contact angle to 60 ° to 75 ° is corona. In addition to the discharge treatment, it is preferable that only one side of the polymethylpentene sheet has a contact angle of 60 ° to 75 ° measured using water at a temperature of 25 ° C. Is preferred.

According to a second aspect of the present invention, as described in claim 4, a flanged container body made of polyester resin is used, and the polymethylpentene sheet according to any one of claims 1 to 3 is used as a lid sheet. A container for freshness, characterized in that the flange portion of the container body and the sheet are heat-sealed, and a lid sheet made of polymethylpentene sheet is securely attached to the container body made of polyester resin. Can be heat-sealed.

According to a third aspect of the present invention, as described in claim 5, after a fresh product is put into a flanged container body made of a polyester resin, a polymethylpentene sheet is used as a lid sheet to form the container. The present invention is characterized in that the flange portion of the main body and the sheet are heat-sealed and then transported, which is suitable for keeping freshness, and particularly suitable for transportation of vegetables, fruits and flowers according to claim 6.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Next, preferred embodiments 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 other α (alpha) -olefin. Here, the α-olefin is ethylene, propylene, 1-butene, 1-hexene, 1-octene,
1-decene, 1-tetradecene, 1-octadecene, 1
-Hexadecene, 1-dodecene, 1-tetradecene, and other olefins having 2 to 30 carbon atoms, 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-
A copolymer mainly composed of poly-4-methyl-1-pentene containing 80 mol% or more of pentene is preferable. Further, from the viewpoints of transparency, gas permeability, heat sealability, etc., the most preferable is a homopolymer of poly-4-methyl-1-pentene.

Polymethylpentene is formed into a sheet by a method such as extrusion. The sheet thickness is not particularly limited, but a sheet thickness of about 0.03 to 1 mm can be preferably used. The sheet thus obtained was subjected to corona discharge treatment, and the contact angle measured using water at a temperature of 25 ° C. was 60 °.
Treat the polymethylpentene sheet to ~ 75 °. Here, the corona discharge treatment, using a known corona discharge treatment device such as a vacuum tube system, thyristor system,
For example, the gap between the discharge electrode and the sheet is preferably about 0.2 to 5 mm, and the applied voltage is 0.1 to 50 kV.

The contact angle of the treated polymethylpentene sheet measured with water at a temperature of 25 ° C. is 60 ° to 7 °.
It 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. If the contact angle is less than 60 °, the sheets are likely to block and stick to each other when the polymethylpentene sheet is wound into a roll, and the sealing strength at the time of heat sealing is also unfavorable. Further, in order to surely 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 within the above range.

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

Further, these containers may be molded in any state by foaming the above resin or in a non-foamed state. A polymethylpentene sheet treated to have a contact angle of 60 ° to 75 ° measured using water at a temperature of 25 ° C can have a surprisingly improved seal strength, especially when heat-sealed with a polyester resin. it can.

Therefore, as shown in FIG. 1, after a fresh product is placed in the container body 1 with the flange 10 made of polyester resin, the polymethylpentene sheet according to any one of claims 1 to 3 is used as a lid sheet. When used as 2, the flange portion 10 and the lid sheet 2 are heat-sealed 3 and then transported. By transporting perishables, the seal may come off due to vibration during transportation or the like. It can be suitably transported without any trouble. As the above-mentioned fresh products, leaf vegetables, fruits, flowers, etc., especially large leaves, vegetables with high respiration volume such as cut cabbage and lettuce, easily wilting vegetables, fruits requiring freshness, as well as carnations, roses and other flowers are transported. This is effective when used and can significantly extend the number of days that freshness is maintained.

The embodiment is not limited to the container body having the illustrated shape, and the lid sheet can be heat-sealed to various container bodies.

[0015]

【Example】

(Experimental Example 1) poly-4-methyl-1-pentene homopolymer (density 0.833g / cm ^3: ASTMD1505 was measured in accordance with, MFR26g / 10min, ASTMD1
(Measured at 260 ° C. according to 238) was extruded 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.

This sheet has a contact angle of 71 measured using water (surface tension 74.14 dyn / cm) at a temperature of 25 ° C.
Corona discharge treatment was performed so as to be at °, 67 °, 65 °, 63 ° and 56 °. The contact angle of the homopolymer sheet of poly-4-methyl-1-pentene not subjected to corona discharge treatment was 90 ° or more. The contact angle measurement method is
Contact angle measuring instrument (manufactured by Elma Co., Ltd .: contact angle measuring instrument G-1)
-1000 type) and 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 liquid was 0.0035 cc. Next, the heat seal strength was measured. The above-mentioned sheet was used as a lid sheet as a measurement sample, and the sheet was heat-sealed to a sealing width of 4.0 mm at a heating temperature of about 270 ° C. for about 6 seconds with a polyethylene terephthalate and a heat-sealing machine to measure the heat-sealing strength. Was used as a sample. This is J
In accordance with IS-Z-1711, test speed 500 mm /
The maximum load point was measured under the test condition of 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 0.3kV) Polymethylpentene 67 ° 0.92 ○ (Line speed 5m / min, Applied voltage 0.6kV) Polymethylpentene 65 ° 0.90 ○ (Line speed 5m / min, Applied voltage 0.9kV) 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 into which 10 large leaves, which are representative of vegetables that are easy to wither, are often used as fresh products. After inserting 0 sheets, a polymethylpentene sheet (having a contact angle of 67 ° as described above) was used as a lid sheet, and the flange portion and the sheet were heat-sealed at a heating temperature of about 275 ° C. to obtain 10 samples. I made a prototype.
As the prototype, the polymethylpentene sheet covering the upper part of the container showed good transparency, and thus a good product was obtained in which the state of the large leaves inside could be clearly seen.

This prototype was transported by truck from Nagoya to Nara under refrigerating conditions of 8 ° C. After transportation, it was stored under the same refrigerating conditions at 8 ° C., and the lid sheet made of polymethylpentene sheet and the flange portion of the tray-shaped container were well sealed, and the large leaves wilted for about 20 days thereafter.
It was confirmed that the adults could be stored well without discoloration. (Experimental example 3) A tray type container with a flange was molded using a foamed sheet made of polyethylene terephthalate (trade name: SELPET, manufactured by Sekisui Plastics Co., Ltd.).

Ten leaves were heat-sealed in the same manner as described above using a polymethylpentene sheet (having a contact angle of 65 ° as described above) as a lid sheet after placing large leaves therein. As the prototype, the polymethylpentene sheet covering the upper part of the container showed good transparency, and thus a good product in which the state of the large leaves inside was clearly visible was obtained. This prototype was transported from Nagoya to Nara by truck under refrigerating conditions of 8 ° C, and was refrigerated under the same conditions. As a result, the lid sheet made of polymethylpentene sheet and the flange portion of the tray type container were well sealed. It was confirmed that the large leaves could be well preserved without wilting or discoloring for about 20 days thereafter. (Comparative Example 1) Ten heat-sealed samples were produced in the same manner as in Experimental Example 2 except that a polymethylpentene sheet that was not subjected to corona discharge treatment was used. However, none of these samples could be heat-sealed satisfactorily, and although they were stored and stored under refrigerated conditions of 8 ° C., they withered after about 5 days.

[0019]

INDUSTRIAL APPLICABILITY The present invention can improve the heat-sealing property of polymethylpentene which is excellent in heat resistance, transparency and gas permeability. In particular, the contact angle, which is one of the indicators of this wetting, is 60 ° to 7 when measured using water at a temperature of 25 ° C.
A sheet with a specific value of 5 ° can exhibit excellent heat-sealing properties with a polyester resin, and a flanged container made of polyester resin is heated with a lid sheet made of polymethylpentene sheet. By using it as a seal, it is possible to transport large leaves, cut cabbage, lettuce, and other vegetables that easily respire, and fruits and flowers that require freshness, and to significantly extend the number of days that freshness is maintained. You can

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

[Brief description of drawings]

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

[Explanation of symbols]

 1 Container 10 Flange Part 2 Lid Sheet 3 Heat Seal Part

Front page continuation (72) Inventor Hiroshi Sakano 3-11-5 Nihonbashihonmachi, Chuo-ku, Tokyo Riken Vinyl Industry Co., Ltd. (72) Inventor Fumitoshi Nakamura 3-11-5 Nihonbashihonmachi, Chuo-ku, Tokyo Riken Vinyl Within Kogyo Co., Ltd. (72) Kojiro Suga 6-1-2 Waki, Waki-cho, Kuga-gun, Yamaguchi Prefecture Mitsui Petrochemical Industries Co., Ltd. (72) Takashi Nakahara Waki-cho, Waki-cho, Kuma-gun, Yamaguchi Prefecture No. 1-2 Mitsui Petrochemical Industry Co., Ltd. (72) Inventor Kazuo Tajima 4-27-604 Kitamachi, Furukawa City, Ibaraki Prefecture (72) Inventor Tatsuo Murai 400-1 Shinosaka, Sakurai City, Nara Prefecture (72) Inventor Maekawa Toshiro 3-5-6 Sakyo, Nara City (72) Inventor Minoru Fujishima 2-8-11-201 Nishinomiya, Taira-gun, Ikoma-gun, Nara

Claims (6)

[Claims] 1. A polymethylpentene sheet having a contact angle of 60 ° to 75 ° measured using water at a temperature of 25 ° C. 2. The polymethylpentene sheet according to claim 1, wherein the means for adjusting the contact angle to 60 ° to 75 ° is performed by corona discharge treatment. 3. Only one side of the polymethylpentene sheet,
The contact angle measured using water at a temperature of 25 ° C. is 60 ° to 7
The polymethylpentene sheet according to claim 1, which has an angle of 5 °. 4. A flanged container body made of polyester resin, wherein the polymethylpentene sheet according to any one of claims 1 to 3 is used as a lid sheet, and the flange portion of the container body and the sheet are combined. A freshness-keeping container characterized by being heat-sealed. 5. After putting a fresh product in a flanged container body made of a polyester resin, a polymethylpentene sheet is used as a lid sheet, and the flange portion of the container body and the sheet are heat-sealed. A method of transporting perishables, characterized by post-transporting. 6. The method of transporting fresh products according to claim 5, wherein the fresh products are vegetables, fruits and flowers.