JP2003170557A - Polyester laminate and molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polyester laminate having not only excellent heat resistance and impact resistance but also excellent recyclability and economy, and to provide a molding. <P>SOLUTION: The polyester laminate comprises a polyethylene naphthalate (B) copolymer polyester having an intrinsic viscosity of 0.40 to 0.70 and laminated on at least one side surface of a base layer made of a polyester (A) having an intrinsic viscosity of 0.50 to 1.0. In the laminate, the thickness of at least one of the layers (A) is 5 to 35 μm. The molding is also provided. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyester laminate and a molded article which are excellent not only in heat resistance and impact resistance but also in recyclability and economy.

[0002]

2. Description of the Related Art Polyester sheets (A-PET), which are extremely excellent in transparency, are rapidly becoming widely used as a packaging material because the packaged contents can be seen. Especially, since it is excellent in food safety and no harmful gas is generated during combustion,
As an alternative material to the conventionally used vinyl chloride, it is widely used for food packaging containers such as umeboshi, tokoroten, mozuku, and blister packs.

However, since A-PET made of polyethylene terephthalate has a low heat resistance temperature of about 65 ° C., it cannot be used in a field requiring heat resistance. For example, when it was used as a lid of a lunch box, it could not be used because the container would be deformed when heated in a microwave oven.

Therefore, many attempts have been made to increase the heat resistance of A-PET. For example, the method of laminating a polyarylate resin having a high glass transition temperature (JP-A-1-200959) has good heat resistance and mechanical properties of the sheet, but bisphenol A is used as a raw material. There is concern about elution of environmental hormones.
As a countermeasure, polyester with low crystallinity has been further laminated on the outermost layer, but a special extruder of 3 types and 5 layers is required, and it becomes very expensive in terms of cost. Is not commonly used as.
Similarly, a method of laminating a PEN resin (polyethylene naphthalate) having a high glass transition temperature (JP-A-9-118).
No. 323) is also studied, but the PEN resin is very brittle in the unstretched state, and the impact strength is extremely lowered by simply laminating it, and the practical level strength is not obtained. .

Therefore, it has been attempted to use a PEN resin which has been copolymerized in order to improve the crackability, which is a drawback of the PEN resin (JP-A-10-16160 and JP-A-10-315417). ). However, although the impact resistance is improved by increasing the amount of the copolymerization component, on the other hand, the high glass transition temperature (about 1
15 ° C.), and the heat resistance of the sheet and the container obtained therefrom also deteriorates. Further, the PEN resin subjected to the special copolymerization is very expensive, and thus is economically inferior. Therefore, the polyester heat-resistant container having a practical impact strength without impairing the food safety, transparency, economy, and recyclability of A-PET has not been widely used at present.

[0006]

The inventors of the present invention have made extensive studies in order to solve the above-mentioned conventional problems, and as a result, the present invention has been achieved. , And to obtain a polyester laminate and a molded product which are excellent not only in impact resistance but also in recyclability and economy.

[0007]

The above-mentioned object is to provide an intrinsic viscosity of at least one side of a base material layer comprising a polyester (A) having an intrinsic viscosity of 0.50 to 1.0 with an intrinsic viscosity of 0.40 to 0.
A polyester laminate in which polyethylene naphthalate (B) 70 is laminated, and the thickness of the (B) layer is 5 to 35 μm, and a polyester laminate, and a molded article. .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The intrinsic viscosity of polyethylene naphthalate used in the layer (B) of the polyester laminate of the present invention is measured in a phenol / tetrachloroethane mixed solvent having a measurement temperature of 20 ° C. and a weight ratio of 60/40. , 0.40
The above is required, and particularly preferably 0.45 or more. This is because if it is less than 0.40, the mechanical strength of the entire sheet decreases due to the notch effect. On the other hand, it should be 0.70 or less, preferably 0.60 or less. This is because if the intrinsic viscosity exceeds 0.70, the melt viscosity becomes extremely high and the film-forming property of the sheet deteriorates.

The polyethylene naphthalate used in the layer (B) is preferably homopolyethylene naphthalate in terms of economy and heat resistance. When the thickness of the layer (B) is within the specified range, the impact resistance of the sheet and the molded product is high, and thus the conventional copolymerization for the purpose of impact improvement is not necessary. However, dicarboxylic acid components such as isophthalic acid, adipic acid, diphenylcarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, sebacic acid, naphthalenedicarboxylic acid, and diethylene glycol, hexamethylene glycol, trimethylene glycol, as long as heat resistance is not deteriorated. A small amount of glycol components such as propylene glycol, cyclohexanedimethanol, neopentyl glycol and butylene glycol can be copolymerized.

The PEN resin laminated on the sheet surface (B) layer has a great influence on the heat resistance and impact resistance of the laminate and the molded product. Therefore, the polyester used for the layer (A) of the laminate of the present invention may be that used for ordinary A-PET, and it is not necessary to use a special one. From the economical point of view, it is preferable to use homo PET. On the other hand, even if a resin having a high impact property is used for the layer (A) for improving the impact strength, the impact strength of the sheet is extremely reduced when the thickness of the layer (B) is out of the range of the present invention, which is not effective.

The intrinsic viscosity of the polyester used in the layer (A) of the polyester laminate of the present invention is 0.50 or more when measured in a phenol / tetrachloroethane mixed solvent having a weight ratio of 60/40 at 20 ° C. Is necessary, and particularly preferably 0.60 or more. This is because if it is less than 0.50, the mechanical strength is reduced. On the other hand, it needs to be 1.0 or less, and preferably 0.80 or less. This is because even if the intrinsic viscosity exceeds 1.0, a significant improvement in mechanical strength cannot be expected, and it is necessary to use an expensive raw material having a high IV, which is not economically advantageous.

Since the laminated body of the present invention has a high glass transition temperature of the layer (B), it is necessary to raise the thermoforming temperature by about 30 to 50 ° C. higher than that of ordinary A-PET. For this reason, when the crystallization speed of the core layer is high, the core layer may be crystallized during thermoforming, which may reduce the transparency. Therefore, the crystallinity of the polyester used for the layer (A) is preferably low. As a guide, the peak temperature (Tc) of the crystallization temperature by DSC is preferably 130 ° C or higher, and particularly preferably 140 ° C or higher. Peak temperature of crystallization temperature (Tc)
If it is less than 130 ° C., the molded product tends to crystallize when the laminate is thermoformed, and the transparency tends to decrease.

When the laminate is produced only from the virgin raw material, homo-PET can provide a thermoformed article having high transparency as in the case of a normal A-PET sheet. However, when a large amount of recycled PET resin is blended, the crystallinity is slightly increased and Tc tends to be lowered.
In such a case, a dicarboxylic acid component such as isophthalic acid, adipic acid, diphenylcarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, sebacic acid, naphthalenedicarboxylic acid, diethylene glycol, hexamethylene glycol, trimethylene glycol or propylene glycol. It is improved by lowering the crystallinity of the polyester used for the layer (A) by copolymerizing a small amount of glycol components such as cyclohexanedimethanol, neopentyl glycol and butylene glycol.

Further, in the polyester, a heat stabilizer, a fluidity improver, an ultraviolet absorber, within a range not deteriorating the transparency,
An antistatic agent, an antifogging agent and the like can be added. When matting is required, a coloring agent such as titanium dioxide, calcium carbonate, iron oxide or carbon black may be added.

The impact strength of the sheet and the molded product in which the PEN resin is laminated on the surface layer has a remarkable PEN layer thickness dependency,
As the PEN resin layer thickness increases, the impact strength tends to decrease. This tendency is hardly improved even if the IV of the resin used for the core layer is increased. PE laminated on sheets and molded products
When the thickness of at least one of the N resin layers exceeds 35 μm, the impact strength is deteriorated, and it becomes difficult to maintain the impact strength at a practical level when used as a container. Furthermore, 5
If it exceeds 0 μm, the impact strength is remarkably reduced, and the sheet is broken during film formation, or cracked when punching the thermoformed container, making it difficult to produce the container itself.

On the other hand, PEN laminated on sheets and molded products
When the thickness of the resin layer is 35 μm or less, it becomes possible to maintain a practical level of impact strength. In particular, when the thickness is 25 μm or less, the impact strength of the sheet and the molded product is extremely small, and the insufficient impact strength, which is a problem in the sheet and the molded product in which the PEN resin is laminated, does not cause any problem.
It is possible to perform various kinds of processing similar to T.

From the viewpoint of impact strength, it is preferable that the PEN resin layer to be laminated is thin, but from the viewpoint of imparting heat resistance, at least one of the PEN resin layers to be laminated on the sheet and the molded product is a continuous PEN resin having a thickness of 5 μm or more. It is necessary to form layers. Laminated PEN in terms of quality stability
The total thickness of the resin layer is preferably 10 μm or more, particularly preferably 13 μm or more.

Specifically, the polyester laminate of the present invention is obtained by laminating the layer (B) on the layer (A), or (B).
Examples include a layer, a layer (A), and a layer (B) having a three-layer structure.

In any of the above-mentioned laminated forms, the thickness of the (B) layer of the polyester laminate and the molded product of the present invention needs to be 5 to 35 μm, preferably 10 to 30 μm, and particularly preferably. It is 13 to 25 μm. Even when the layer (B) is laminated on both sides of the layer (A), excellent impact resistance can be maintained as long as the thickness of each layer is within the above range.

Even if the PEN resin thickness of the PEN resin laminated sheet exceeds the above range and is inferior in impact resistance, the PEN resin layer thickness in the container is adjusted by thermoforming and stretching. If it falls within the range, impact resistance is improved.

When a load is applied to the container such as a jelly container for hot filling or a lunch container body for heating in a microwave oven, the total thickness of the PEN resin layer of the heat resistant container is at least 20 μm or more in total. Although it is necessary, the container itself becomes hot like the upper lid of the lunch container, but if there is little load and it is only necessary to maintain the shape of the container, 5μ
Heat resistance can be maintained by forming a continuous PEN resin layer of m or more. In the case of a container shape in which the area of the portion without ribs is large, it is necessary to make the total thickness of the PEN resin layer relatively thick, but sufficient heat resistance can be imparted by laminating 10 μm or more.

As mentioned above, only in a specific stacking thickness range,
Both practical heat resistance and impact resistance can be realized, but this range is constant without being affected by the thickness of the entire sheet. As a result, the ratio of the PEN resin laminated on the surface layer to the entire sheet varies greatly depending on the thickness of the sheet. For example, when PEN resin is laminated on both surfaces of a 100 μm sheet (PEN resin layer 35 μm / PET resin layer 30 μm / PEN resin layer 35 μm
m) PEN accounts for 70%, but 1000μ
When PEN resin is laminated on both sides of the m sheet (PEN resin layer 15 μm / PET resin layer 970 μm / P
The EN resin layer 15 μm) PEN accounts for only 3%.

From the past, in consideration of heat resistance, moldability, and economical efficiency, there are many examples in which the heat resistant layer is preferably about 10 to 30%. There is no correlation in impact. For example, a laminated sheet of 1000 μm in which a PEN resin is laminated on one side in an amount of 50 μm has a remarkably low impact strength and is not suitable for practical use even though the heat resistant layer is only 5%.

From the viewpoint of thermoformability and heat resistance of the polyester laminate of the present invention and a molded product, it is preferable to laminate the PEN resin on both sides of the sheet and the molded product. Particularly preferably,
A laminate and a molded product in which a layer (B) having a thickness of 13 to 25 μm is laminated on both surfaces of the layer (A).

The total thickness of the polyester laminate and the container of the present invention is not particularly limited, but is usually 50 to 2000 μm.
Is preferable, and particularly preferably 150 to 1000 μm. The laminate can be obtained, for example, by melt-extruding with a usual extruder for polyester such as a single-screw extruder or a twin-screw vent extruder, and cooling the molten resin with a cooling drum. The laminated body is preferably cooled as rapidly as possible in order to prevent deterioration of transparency and thermal adhesiveness due to crystallization, and a haze of 3% or less is desirable.

The laminate of the present invention can be used with a known coextrusion device having a feed block die, a multi-manifold die and the like. Also, it can be manufactured by known techniques such as melt lamination and dry lamination,
Coextrusion is preferred because of the quality of the laminate.

As a film forming method, there are a method of sandwiching and cooling between metal rolls (touch roll method), an electrostatic application method, an air knife method, etc., but from the viewpoint of glossiness and thickness uniformity of the sheet or laminate. The touch roll method is preferred.

Further, there is no particular problem in applying a necessary amount of silicone or an antifogging agent in order to prevent blocking and impart antifogging property.

A-PE is an in-line recycling method in which the ears and the skeleton part punched out of the thermoforming container that appear when the laminate is cut into a predetermined width are crushed and returned as raw materials during film formation.
Although it is generally used for T, in the present invention, there is no problem even if it is blended with the layer (A) within a range that does not extremely reduce the haze of the sheet. It is also possible to increase the compatibility of the resins and improve the transparency by copolymerizing a small amount of each of the PEN resin and the PET resin used. However, even if the homo-PEN resin is used for the (B) layer and the homo-PET resin is used for the (A) layer,
Since the sheet haze is not significantly reduced by selecting the film forming temperature condition, there is no problem in blending the skeleton obtained by punching the ears and the container after thermoforming into the (A) layer.

The molded products of the present invention include vacuum molding, pressure molding,
Hot plate molding, plug assist molding, reverse draw molding,
Any method such as air slip molding or a combination of these methods may be used.

[0031]

EFFECTS OF THE INVENTION The polyester laminate and the molded product of the present invention are A-PET having transparency, food safety and recyclability.
It is not only excellent in heat resistance but also economical because it retains its original properties, and is optimal for heat-resistant containers for food packaging, especially for lunch boxes and side dishes.

[0032]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.
Each characteristic value was measured according to the following method.

(1) Intrinsic viscosity (I of laminate or molded product)
V) It was measured 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) Layer thickness The layer thickness was determined by observing the cross section of the sheet and the molded product with a polarizing microscope.

(3) Haze of sheet and molded product Haze (haze value) of the sheet was measured by a method according to JIS-K-7105 using a haze meter NDH-20D manufactured by Nippon Denshoku Co., Ltd.

(4) Heat resistance of container Leave the thermoformed container in an oven at 100 ° C for 10 minutes, No deformation The deformed one was evaluated as x.

(5) Crystallization peak temperature (Tc) Differential scanning calorimeter (manufactured by Perkin Elmer, model DS
C-7) was measured by a method according to JIS-K-7105. The quenched sheet in a substantially amorphous state was measured in a nitrogen stream at a temperature rising rate of 10 K / min to determine a peak temperature (Tc) for crystallization.

(6) Impact Strength of Laminated Body and Molded Product A test piece having a length of 90 mm and a width of 90 mm was prepared from the laminated body and the molded product (the molded product was prepared by cutting out the top plate of the container),
Using a surface impact tester (Hydroshot) with a constant temperature bath manufactured by Shimadzu Corporation, the breaking energy at 20 ° C was measured under the conditions of a punching speed of 5 m / sec, a punching punch diameter of 13 mm and a die diameter of 3 inches. Breaking energy is 4.0 kJ /
Those having m or more were evaluated as ◯, those having 2.5 kJ / m or more and less than 4 kJ / m were evaluated as Δ, and those less than 2.5 kJ / m were evaluated as x.

From the main extruder, the PET resin was set at a set temperature of 295 ° C. and the vent degree of the twin-screw extruder was set to 667 Pa. From the sub-extruder under the conditions,
Melt extrusion was performed from a T die using a multi-layer extruder. The ears of the sheet cut to obtain a sheet having a predetermined width were returned to the core layer. The melt-extruded resin was cooled by a touch roll method to obtain a polyester laminate of 2 types and 3 layers of various configurations. To prevent blocking, add 10
mg / m ^{2 was} applied.

For the evaluation of physical properties, a vacuum pressure air molding machine with plug assist was used to measure length 135 mm × width 190 mm.
A molded product for a lid of a lunch box having a depth of 32 mm was produced (thermoforming condition: the sheet surface temperature measured by an infrared radiation thermometer was 1
50 ° C., mold temperature 35 ° C., vacuum degree 8000 Pa).

Comparative Examples 1 to 7 A sheet obtained by laminating a PEN resin on the surface layer of the sheet tends to have a reduced impact strength, and when the PEN resin layer thickness exceeds a specified value, the impact strength of the sheet and the molded product is It can be seen that it is remarkably low and does not have practical strength. Surface PE
A high-IV N resin is used, and the core layer is a copolyester having excellent impact resistance (PETG6763 1,4
Even if cyclohexanedimethanol 33 mol% copolyester manufactured by Eastman Co., Ltd. is used, almost no improvement effect is observed. Further, as can be seen from Comparative Example 4, even if the PEN resin layer occupies a low proportion in the whole sheet, the impact strength of the laminate is remarkably low when the thickness of the PEN resin layer exceeds the specified value. It can be seen that the property largely depends on the thickness of the PEN resin laminated on the surface layer.

Examples 1 to 4 Those having a PEN resin layer thickness of the surface layer of the sheet within the specified range have excellent impact resistance and maintain practical strength without using a special copolymerized PEN resin. I know what I can do. Also, it can be seen that the heat resistance of the container is sufficient for the use of the upper lid where no load is applied.

[0043]

[Table 1]

Continued front page    F term (reference) 3E033 AA09 BA17 BA30 BB08 CA03                       CA07 CA18 FA04                 4F100 AK41A AK41B AK41C BA03                       BA06 BA25A BA25C BA26                       GB16 JA06A JA06B JA06C                       JJ03 JK10 JL16 YY00A                       YY00B YY00C

Claims (2)

[Claims] 1. A polyethylene naphthalate (B) having an intrinsic viscosity of 0.40 to 0.70 is provided on at least one surface of a base material layer made of a polyester (A) having an intrinsic viscosity of 0.50 to 1.0. A laminated polyester laminate, wherein the layer (B) has a thickness of 5 to 35 μm. 2. A polyethylene naphthalate (B) having an intrinsic viscosity of 0.40 to 0.70 is provided on at least one side of a base material layer made of polyester (A) having an intrinsic viscosity of 0.50 to 1.0. A molded article, which is a laminated polyester laminate and has a layer (B) thickness of 5 to 35 μm.