JP2001315284A - Polyester laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester laminate which shows high heat adhesion and excellent recycle properties and is economical and best suited for the use as a packaging container which undergoes various kinds of heat adhesion processes. SOLUTION: This polyester laminate is structured of an layer (A) laminated at least on one of the faces of a layer (B); the layer (A) is formed of a copolymerized polyester with an intrinsic viscosity of 0.55-0.80, obtained by copolymerizing 1-10 mol% isophthalic acid and the layer (B) is formed of a polyester with an intrinsic viscosity of 0.55-0.80, obtained by copolymerizing 0-10 mol% isophthalic acid. In addition, at least one thickness of the layer (A) is equivalent to 1% or higher of the total thickness of the laminate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester sheet having good thermal adhesiveness and excellent economy.

[0002]

2. Description of the Related Art The use of polyester sheets (A-PET), which are extremely excellent in transparency, as packaging materials is rapidly spreading because the packaged contents are visible. In particular, because it is excellent in food safety and there is no harmful gas generation during combustion,
As an alternative to the conventionally used vinyl chloride, it is widely used for food packaging containers such as umeboshi, toroten, mozuku and blister packs.

Since A-PET is used as a substitute material for vinyl chloride, it is necessary to have various processing aptitudes conventionally performed. For example, various heat bonding processes such as a heat sealing process in which containers are thermally bonded to each other without an adhesive, a bonding method using an easy-peel adhesive, or a blister bonding in which a backing sheet coated with an adhesive and a blister pack are thermocompressed. It needs to be performed stably.

[0004] However, A-PET using unmodified polyester is not sufficiently processable due to its crystallinity. For this reason, for applications such as thermal bonding, it is common to use PET resin with low crystallinity for all layers of the sheet, or for laminated upper and lower layers. As a typical example, KODAR PETG6763 manufactured by Eastman Kodak Co., Ltd. obtained by copolymerizing 33 mol% of 1,4 cyclohexanedimethanol is generally widely used.

However, since the above-mentioned copolymerized polyester is amorphous, it is difficult to handle due to fusion during a drying step and an extrusion step. Usually, there is a problem in the recycle property which is the largest property of A-PET. This is because the above-mentioned copolymerized polyester is slightly inferior in thermal stability to a commonly used homopolyester, and therefore has a problem that it is colored or its IV is slightly lowered when used as a recycled material. Also, due to the high copolymerization component ratio, even if these sheets are only thinly laminated on the upper and lower layers, when recycled, they cannot be used for fibers because of insufficient heat resistance and orientation, This is because the use is limited to limited ones such as sheets. Further, the above-mentioned copolymerized polyester is expensive and is not economical for use in general-purpose packaging materials.

[0006]

SUMMARY OF THE INVENTION The present inventors have made intensive studies in order to solve such a conventional problem, and as a result, have arrived at the present invention. An object of the present invention is to obtain a polyester laminate which is economical as well as excellent in properties and recyclability, and is most suitable for a packaging container to be subjected to various types of heat bonding.

[0007]

An object of the present invention is to provide a polyester laminate comprising a layer (B) and a layer (A) laminated on at least one surface of the layer, wherein the layer (A) contains 1 to 1 of isophthalic acid.
A layer comprising a copolymerized polyester comprising 0 mol% and a copolymerized polyester having an intrinsic viscosity of 0.55 to 0.80, wherein the layer (B) comprises 0 to 10 mol% of isophthalic acid and A polyester laminate having an intrinsic viscosity of 0.55 to 0.80, wherein at least one layer (A) has a thickness of 1% or more of the total thickness of the laminate. Achieved by

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester used for the layers A and B in the present invention is mainly polyethylene terephthalate, but other polyesters can also be used.

The copolymerized polyester used in the layer (A) of the polyester laminate of the present invention must have an isophthalic acid copolymerization ratio of at least 1 mol%, preferably at least 3 mol%. If the copolymerization ratio is less than 1 mol%, crystallization of the surface disadvantageous to thermal bonding occurs, and the heat sealability between the sheets and the thermal adhesiveness using various adhesives decrease, which is not preferable. is there. The copolymerized polyester has an isophthalic acid copolymerization ratio of 10 mol%.
Or less, preferably 7 mol% or less. If the copolymerization ratio exceeds 10 mol%, the whole sheet becomes brittle and easily cracked due to the notch effect, which is not preferable. It is preferable to copolymerize isophthalic acid from the viewpoint of stability of thermal bonding, but in some cases, it is also possible to blend a polyester having a high copolymerization of isophthalic acid with a homopolyester.

The intrinsic viscosity of the polyester used for the layers (A) and (B) of the polyester laminate of the present invention is 2
When measured in a phenol / tetrachloroethane mixed solvent having a weight ratio of 60/40 at 0 ° C., a value of 0.55 or more is required, and particularly preferably 0.60 or more. This is because the mechanical strength of the entire sheet is reduced due to the notch effect when it is smaller than 0.55. On the other hand, it is necessary to be 0.80 or less, and preferably 0.73 or less. Even if the intrinsic viscosity exceeds 0.80, a significant increase in mechanical strength cannot be expected, and expensive raw materials with high IV must be used, which is not economically advantageous.

Specifically, the polyester laminate of the present invention is obtained by laminating a layer (B) on a layer (A) or (A)
Layer, a layer (B), and a layer (A) having a three-layer structure. For example, in a case where the layer is thermoformed and used as a blister case, the surface on the side where the layer (A) is bonded to the backing paper Can be used.

In any of the above-mentioned lamination forms, when the polyester laminate of the present invention is used by heat bonding, the thickness of (A) on the side used on the bonding surface side is a proportion of the total thickness of the laminate. It is necessary to be at least 1%, and from the viewpoint of quality stability, it is preferably at least 3%, particularly preferably at least 5%. If it is less than 1%, the thermal adhesive strength becomes unstable, which is not preferable. On the other hand, the maximum thickness to be laminated is preferably 30% or less, particularly preferably 20% or less. Although an effect is obtained even if it exceeds 30%, the case where the thickness ratio of the (A) layer is 30% or less tends to have excellent impact strength of a container obtained by thermoforming a sheet made of a polyester laminate. If the amount exceeds 30%, the effect of further improving the thermal adhesiveness is small, and therefore, it is economically preferable to suppress the amount of expensive copolyester to 30% or less.

The thermal adhesion of the laminate is largely affected by the composition of the sheet surface and is less affected by the main layer. Therefore, the polyester used for the layer (B) of the laminate of the present invention is homo P
It is economically preferable to use ET, but when performing deep drawing, it is preferable to use a PET resin obtained by copolymerizing isophthalic acid in an amount of 3 mol% or more for the (B) layer. This is because copolymerization of isophthalic acid improves the deep drawing thermoformability. From the viewpoint of mechanical strength, the copolymerization ratio of isophthalic acid is required to be 10 mol% or less, preferably 7 mol% or less. It is not only economically disadvantageous to raise the copolymerization ratio of isophthalic acid than necessary, but if it exceeds 10 mol%, the sheet becomes brittle and mechanical properties deteriorate, which is not preferable.

The layer (A) of the polyester laminate of the present invention,
In the polyester used for the (B) layer, in addition to isophthalic acid, dicarboxylic acid components such as adipic acid, diphenylcarboxylic acid, diphenylether dicarboxylic acid, diphenylsulfone dicarboxylic acid, sebacic acid, and naphthalenedicarboxylic acid; and diethylene glycol,
Hexamethylene glycol, trimethylene glycol,
Propylene glycol, cyclohexane dimethanol,
Glycol components such as neopentyl glycol and butylene glycol can also be used.

However, the total proportion of copolymer components other than isophthalic acid contained in the PET is preferably at most 10 mol%, more preferably at most 3 mol%. Further, it may contain a trifunctional or more functional compound or a monofunctional compound within a range considered to be substantially linear. Further, a heat stabilizer, a fluidity improver, an ultraviolet absorber, an antistatic agent, an anti-fogging agent and the like can be added to the polyester within a range that does not lower the transparency. When matting is required, a coloring agent such as titanium dioxide, calcium carbonate, iron oxide, or carbon black can be contained.

The reasons why the isophthalic acid copolymerized PET resin having the above composition is suitable for A-PET are as follows. First, isophthalic acid has the effect of reducing the crystallinity required to improve the thermal adhesiveness with a low molar copolymerization as compared with other copolymer components, and is advantageous in cost and economical. However, there is a tendency that the thermal bonding temperature is lowered without a significant decrease in heat resistance due to copolymerization. Furthermore, since the copolymerized PET resin having the above composition has appropriate crystallinity, it is easy to handle without being fused in a drying step or an extrusion step, and has a thermal stability equivalent to that of homo PET and a copolymerization ratio. Because it is not higher than necessary, KODAR PETG 676
The recyclability, which is a particular problem in No. 3, does not have any problem.

The total thickness of the polyester laminate of the present invention is:
Although not particularly limited, it is usually preferably 50 to 2000 μm, and particularly preferably 200 to 1000 μm. The laminate can be obtained by melt-extrusion using a usual polyester extruder such as a single-screw extruder or a twin-screw vent-type extruder, and cooling the molten resin by a cooling drum. The laminate is preferably rapidly cooled as much as possible in order to prevent a decrease in transparency and thermal adhesiveness due to crystallization, and a haze is desirably 3% or less.

For the laminate of the present invention, a known co-extrusion apparatus having a feed block die, a multi-manifold die and the like can be used. Also, it can be manufactured by a known technique such as melt lamination and dry lamination,
Coextrusion is preferred from the quality of the laminate.

It is not preferable to apply a large amount of silicone coating since it acts in the direction of reducing the thermal adhesiveness, but in the case of the present invention, there is no particular problem with the amount of silicone required to prevent blocking. .

Examples of the film forming method include a method of sandwiching and cooling between metal rolls (touch roll method), a method of applying electrostatic force, an air knife method, etc., from the viewpoints of gloss and thickness uniformity of a sheet or a laminate. The touch roll method is preferred.

A-PET is generally used for in-line recycling of A-PET, in which an ear portion that is formed when a sheet or a laminate is cut into a predetermined width during film formation or a skeleton portion obtained by punching a container after thermoforming is crushed and returned as a raw material. Although it is used, in the present invention, it is preferable to blend it into the layer (B) within a range that does not extremely lower the intrinsic viscosity of the sheet or the laminate.

[0022]

Industrial Applicability The polyester laminate of the present invention is not only excellent in heat bonding recyclability but also economical and is most suitable for packaging containers for performing various heat bonding processes.

[0023]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.
In addition, each characteristic value was measured according to the following method.

(1) Intrinsic viscosity (I of sheet or laminate)
V) Measurement was carried out in a phenol / tetrachloroethane mixed solvent having a weight ratio of 60/40 at a concentration of 1.0 g / dl and at 20 ° C.

(2) Heat seal strength between laminates Peel test (n = 2)
0) was performed, and the following evaluations were made based on the peel strength per 15 mm seal width. If all were in the range of 14.7 N (1500 g) or more; ○ If any one was less than 14.7 N (1500 g), it was evaluated as ×.

(3) Easy peel adhesive strength Peeling test (n = 2) at a rate of 50 mm / min.
0) was performed, and the following evaluations were made based on the peel strength per 15 mm seal width. All 4.9N (500g) or more 9.8N (1000g)
If it is in the following range: ○ Any one is 2.0N (200g) or more and 4.9N (500g)
g); if at least one was less than 2.0 N (200 g);

(4) Evaluation of Blister Adhesive Strength After placing 60 g of the product in the molded product and thermally bonding it to the backing paper,
It was cooled down to the concrete ground and dropped from a height of 1 m from the azimuthal direction. No peeling out of 10 tests;
も の Even one peeled off; ×.

(5) Cracking of Containers, etc. Sealed laminates, containers adhered with an easy peel adhesive, and blister containers are peeled off by hand, and cracks do not occur in the laminates, lids, container bodies, blister containers, and the like. The sample was evaluated as ○, and the sample in which cracks occurred even at one location was evaluated as ×.

Melt extrusion was performed from a T-die using a multilayer extruder with a twin screw vent at 285 ° C. and a degree of vacuum of 667 Pa at a vent portion, and a film was formed by a touch roll method to form two types and three layers. A polyester laminate was obtained. Further, 10 mg / m ^{2 of} silicone was applied to prevent blocking.

The following containers were prepared by vacuum molding for evaluation of various thermal adhesiveness (thermoforming conditions: surface temperature of the laminate 100 ° C., mold temperature 35 ° C., degree of vacuum 8000 Pa).
A 100 mm x 100 mm 70 mm deep body container (using a 600 μm thick laminate) to evaluate the heat sealability of the laminates without using an adhesive and to evaluate the adhesiveness when using an easy peel adhesive. And a lid having a size of 100 mm × 100 mm and a depth of 10 mm (using a laminate having a thickness of 250 μm). Further, a dome-shaped blister container of 50 mm × 100 mm (using a laminate having a thickness of 300 μm) was prepared for evaluating the adhesiveness with the blister mount to which the adhesive was applied.

Various adhesives were used in the following manner. Easy peel agent (polyester) has a dry thickness of 5μm
Gravure printing was carried out, and a lid was produced by vacuum molding. The blister adhesive (polyester type) was used by applying a dry weight of 4 g / m ² to a coated paper having a thickness of 350 μm.

The heat bonding was performed under the following conditions. Evaluation of heat sealability between sheets or laminates Hot plate temperature 180 ° C, pressure 0.405MPa, sealing time 2.0 seconds / cycle Easy peel adhesion evaluation Hot plate temperature 160 ° C, pressure 0.405MPa, sealing time 1.5 seconds / Cycle blister adhesion evaluation Hot plate temperature 180 ° C, pressure 0.284MPa, sealing time 1.2sec / cycle

Comparative Examples 1 to 6 A copolymer having a low copolymerization ratio of isophthalic acid or a thinner surface layer is not preferred because the adhesive strength is lowered (Comparative Examples 1 to 6).
4,5). If the copolymerization ratio of isophthalic acid is too high or the sheet IV value is too low, the container is easily broken (Comparative Examples 2, 3, and 6).

Examples 1 to 3 When the copolymerization ratio of isophthalic acid and the sheet IV are within the proper ranges, excellent adhesive strength can be obtained by any of the heat bonding methods, and a container having sufficient mechanical strength can be obtained. Can be obtained (Examples 1, 2, 3, 3).

[0035]

[Table 1]

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3E035 BD10 CA07 DA03 4F100 AK42A AK42B AK42C AK42J AK42K AL01A AL01B AL01C BA03 BA06 BA10A BA10C BA23 BA25 GB15 GB16 JA06 JA06A JA06B JA06C JK07 JL12 YY00YYB00

Claims (1)

[Claims] 1. A polyester laminate comprising a layer (B) and a layer (A) laminated on at least one side of the layer, wherein the layer (A) copolymerizes 1 to 10 mol% of isophthalic acid and has an intrinsic viscosity of 0. A layer comprising a copolyester having a molecular weight of 0.55 to 0.80, wherein the layer (B) contains 0 to 10 mol% of isophthalic acid.
A layer made of polyester copolymerized and having an intrinsic viscosity of 0.55 to 0.80, wherein at least one layer (A) has a thickness of 1% or more of the total thickness of the laminate. Polyester laminate.