JP3112603B2 - Polyester sheet for thermoforming - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to prepare a polyester molded lid or container having a low-temperature heat-sealing property while retaining a flavor component having the contents of a food or the like in a package for filling the food or the like. And a thermoforming polyester sheet.

[0002]

2. Description of the Related Art Conventionally, in a package for filling food or the like, a polyester container, which is one of the adherends to which the package is filled, has been widely used as a container for the food or the like.

[0003]

In the case of sealing a lid and a container by a heat sealing method after filling the contents, a polyester molded by a thermoforming method such as vacuum forming or pressure forming. Molded lids, containers, and the like are often used recently because they have excellent taste retention of foods due to the properties of polyester, but have difficulty in heat sealing.

[0004] Therefore, for the purpose of imparting a low-temperature heat-sealing property to a heat-sealing layer, studies have been made on low-temperature heat-sealing using a copolymer type polyester having a low glass transition point or a blend of the polyester.

However, such a polyester sheet has a drawback that the innermost layer of the heat seal layer and the base layer of the polyester layer are liable to cause blocking in the wound state of the sheet, and the polyester sheet is wound during thermoforming such as vacuum forming or pressure forming. Dispensing cannot be performed, or even when the thermoformed molded articles are stacked, the individual molded articles when filling and heat-sealing the contents such as foods are blocked, and there is a problem that the mold cannot be released.

As a means for preventing blocking, a method of applying a solution such as a silicone resin as a release agent to the surface of the base layer has been attempted. However, such a method involves heating the release agent in a wound state. There is a disadvantage that the heat sealing property is greatly impaired by adhesion or transfer to the sealing layer surface.

The present invention provides a polyester sheet for thermoforming which is excellent in heat sealability, does not cause blocking in a wound state, and can be smoothly released from a stacked state of the molded body. With the goal.

[0008]

The present invention for achieving the above-mentioned object is to form a composite of polybutylene terephthalate having a melting point of 180 ° C. or more on the outer surface of an amorphous linear saturated polyester resin layer as a base layer. And the combined thickness is
A thickness of 10 to 50 μm is appropriate.

The compounding method is an embodiment of dry lamination of a polybutylene terephthalate film with a urethane adhesive or co-extrusion sheeting.

[0010]

The present invention configured as described above has the following effects.

A first heat-sealable polyester
A layer, an amorphous linear saturated polyester resin layer serving as a base layer as a second layer adjacent to the first layer, and a polybutylene terephthalate layer as a third layer disposed adjacent to the layer. Thereby, as described above, the anti-blocking property at the time of winding and the anti-blocking property of the stacked molded product can be obtained.

[0012]

Next, an embodiment of the polyester sheet for thermoforming of the present invention will be described with reference to the drawings.

FIG. 1 shows a three-layer coextruded sheet A according to an embodiment of the present invention.
Is shown, a first layer 1 and a second layer 2
And the third layer 3.

In FIG. 1, the first layer is a heat-sealable polyester.

The thickness of the first layer 1 is preferably 15 μm or less.

In order to obtain the polyester which is the first layer 1 having such proper physical properties, the present inventors have conducted intensive studies and as a result, have obtained an amorphous wire having good heat sealability and a breaking elongation close to zero. Amorphous linear saturated polyester with very low glass transition temperature that can be well-suited to this purpose in order to further improve the heat-sealing property in the fused state with the target adherend polyester. It has been found that the purpose can be achieved by blending polyester.

Such a blended polyester is, for example, a non-crystalline linear saturated polyester having a heat seal property, which is a registered trademark of Komatsu manufactured by Eastman Kodak Company.
dabond Copolyester5116 (glass transition temperature 58 ℃) or
DuPont Selar PT X-207 (glass transition temperature 71 ° C)
The desired physical properties can be obtained by appropriately blending an amorphous linear saturated polyester having a very low glass transition temperature and a registered trademark of Byron GM-900 (glass transition temperature: -20 ° C) manufactured by Toyobo Co., Ltd. Can be

The blend ratio of the amorphous linear saturated polyester having a low glass transition temperature is 30% or less, preferably 15 to
A range of 25% is appropriate.

As a blending method, a blend mixer commonly used in the art can be used. Before the mixture is introduced into an extruder for forming a film, it is necessary to prevent hydrolysis required for general polyester extrusion. Dehumidification drying for is essential.

In FIG. 1, the second layer 2 serves as a base layer of the polyester sheet for thermoforming of the present invention, and the amorphous linear saturated polyester resin is, for example, ethylene glycol, propylene glycol or one of the glycol components. Condensed polymers with alcohol components such as those whose parts are substituted with 1,4-cyclohexanedimethanol with dicarboxylic acids such as terephthalic acid and isophthalic acid are used, but amorphous polyethylene terephthalate is generally used. Generally, those having a glass transition temperature of 70 ° C. or higher are used.

The thickness of the layer is determined by the shape of the molding and, in particular, the drawing ratio of the molding, and is generally from 200 μm to 200 μm.
A thickness of 1000 μm is used as a polyester sheet for thermoforming.

For the purpose of improving gas barrier properties, a polyethylene vinyl alcohol resin or a polyvinylidene chloride resin layer, which is widely used in the art, is formed between the first layer 1 and the second layer 2. No problem.

The third layer 3 of the embodiment of the present invention prevents the blocking of the polyester sheet for thermoforming comprising the first, second and first layers 1 and 2 claimed in the present invention, and
The objective was achieved by combining polybutylene terephthalate, which also has recyclability with the third layer, by compromising the heat sealing properties and thermoformability and by being appropriately compatible with each layer in the third layer. It is.

The thickness of the layer is suitably from 10 to 50 μm, and the compounding method can be dry lamination of a polybutylene terephthalate film with a urethane adhesive or co-extrusion sheeting.

As for the polybutylene terephthalate type of the layer, the homo type is more excellent in antiblocking property in the constitution of the present invention than the polybutylene terephthalate copolyester type.

The polybutylene terephthalate suitable for the purpose includes, for example, Duranex (registered trademark) manufactured by Polyplastics Co., Ltd. and NOVADUR (registered trademark) manufactured by Mitsubishi Kasei Corporation having a melting point of 224 ° C.

In the present embodiment, the extrusion temperature at which the sheet composed of the first to third layers was prepared by the co-extrusion sheeting method was set at 230 ° C. for the first layer, 240 ° C. for the second layer, and 260 ° C. for the third layer. I went.

Examples 1 to 6 are shown in Table 1 and Comparative Examples 1 to 4 are shown in Table 2.

According to Table 1, the anti-blocking property is as follows.
Clearly good results are shown in the examples of the present invention.

As shown in FIG. 2, the blocking property of the take-up roll is such that the inner surface and the outer surface of the sheet A are applied when the sheet is wound on the thermoforming machine 4 such as vacuum forming and pressure forming, and when the sheet winding 5 is unwound. When blocking is performed, unwinding of the sheet A becomes impossible.

Therefore, in the same figure, the polyester sheet of the present invention is smoothly unwound, and the sheet A is softened by the infrared heaters 7, 7 arranged on both sides thereof, and the vacuum action from the mold 8 is reduced. And the pressing force of the plug 9 to form a compact b.

Next, the molded body b is filled with contents such as food, and then placed in a cup-filling and sealing machine 11 which is heat-sealed with the lid member 10. As shown in FIG. A large number of compacts b stacked on 12 are released one by one, and into a compact receiving bucket 13 provided below the compacts b,
When the fittings are inserted one after another, this operation cannot be performed if the molded bodies b that are adjacent to each other and overlap each other in the storage body 12 are blocked.

In the same figure, the compacts b thermoformed from the sheet A of the present invention are smoothly separated one by one from the lower one from the state of being stacked in the storage body 12 one by one. Fit into bucket 13,
The molded body b is filled with the contents by the filling machine 14, and in the next step, the lid 10 continuously fed out from the lid winding 15
Is supplied to the molded body b of the bucket 13 and heat-sealed between the lid 10 and the flange portion of the molded body b by heat sealing bars 16 and 16. Shown is a package 18 punched and packaged at 17.

FIG. 4 is a view in which the lid member 10 thermoformed from the sheet A of the present invention is heat-sealed to the polyester container 19.

FIG. 5 shows a case where the sheet A is thermoformed into a molded body b which is a container as described above.

[0036]

[Table 1]

[0037]

[Table 2]

Polyester sheet for thermoforming Outer layer: Polybutylene terephthalate manufactured by Polyplastics Co., Ltd. Duranex, 600FP (melting point: 224 ° C.) Base layer: Polyethylene terephthalate resin J-025 manufactured by Mitsui Pet Resin Co., Ltd. (glass transition point: 70 ° C.) Inner layer: A: Copolymer polyester Kodabond Copolyester 5116 (glass transition: 58 ° C.) manufactured by Eastman Chemical Company B: Polyester manufactured by Toyobo Co., Ltd. Byron GM9
00 (glass transition point -20 ° C, melting point 113 ° C).

Seal strength Biaxially stretched nylon film 15 μm thick / Same as above Kodabond C
opolyester 5116,50μm thickness and inner layer surface at 180 ℃ × 2.0kg
/ Cm ² × 1.0 seconds after heat-sealing and 30 in Tensilon
Measured at 0 mm / min, CH.S.

Anti-blocking property Both the take-up roll and the molded article / molded article were cooled sufficiently at 23 ° C. after a lapse of 40 ° C. × 24 hours, and the degree of blocking was checked.

Judgment ☆: No blocking ○: Very slight blocking and no hindrance to production △: Medium blocking and hindrance to production ×: Large blocking and no release.

[0042]

The polyester sheet for thermoforming of the present invention thus obtained is excellent in productivity such as thermoforming because of its excellent anti-blocking property, and is produced at the time of filling and sealing the molded article. It also has excellent utility in heat-sealing properties, recyclability after finishing the role of the package, and the like.

In addition to the field of foods, the present invention has a special effect such as those which can be widely used for packaging in the fields of medical and electronic parts.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view showing a part of a configuration of one embodiment of a polyester sheet for thermoforming according to the present invention.

FIG. 2 is an explanatory view showing a step of forming a formed body using the sheet of FIG. 1;

FIG. 3 is an explanatory view showing a step of molding a package containing contents by using the molded article molded in FIG. 2;

FIG. 4 is a cross-sectional view showing a heat-sealed state of the package in an example in which the sheet in FIG.

FIG. 5 is a cross-sectional view showing a heat-sealed state of a package in which the sheet in FIG. 1 is used for a container.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polyester 2 Amorphous linear saturated polyester resin 3 Polybutylene terephthalate

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FIB29L 9:00

Claims (1)

(57) [Claims] 1. An inner surface of an amorphous linear saturated polyester resin layer, which is a base layer, is heated with a copolyester having a glass transition temperature of 85 ° C. or lower, or a blend resin with another type of polyester containing the polyester. A polyester sheet for thermoforming, comprising a polybutylene terephthalate compound for the purpose of preventing blocking with the heat sealing layer on the outer surface of a layer opposite to the sealing layer.