JP2002096438A - Multi-layer polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-layer polyester film having good forming property, heat resistance, solvent resistance, dimensional stability, handling property and the like. SOLUTION: The multi-layer polyester film comprises a multi-layer film of at least three layers having laminated structure consisting of a polyester layer A as a top layer having stretched orientated structure to one axis or more and a polyester layer B having non-oriented structure which is obtained by heat treatment of stretched orientated structure to one axis or more, wherein (1) a melting point of a polyester constituting the layer A is at least 15 deg.C higher than that of a polyester constituting the layer B, and (2) a ratio (a/b) of a total thickness (a) of the polyester layer A to a total thickness (b) of the polyester layer B is from 0.01 to 3. Preferably, the multi-layer film is prepared by a co-extrusion film manufacturing process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer polyester film, and more particularly, to a film which is excellent in moldability, workability, stability over time, solvent resistance, dimensional stability, etc., and is used for deformation processing such as molding and embossing. The present invention relates to a multilayer polyester film which is particularly useful for applications in which the film is fixed by holding it between holding metal fittings.

[0002]

2. Description of the Related Art In recent years, in the food packaging field (for example, trays,
Ice cream cup, etc.), medicine packaging field (eg, PTP drug packaging such as capsules and tablets), laminate molding field (eg, furniture, indoor and outdoor decorations, electric appliances, automobile parts, etc., films and paper, wood, metal, Alternatively, films (including sheets) are included in a wide range of fields such as the field of card materials for magnetic recording (eg, cash cards, ID cards, credit cards, etc.) and the field of agriculture (eg, greenhouses). same as below)
Is used.

[0003] In these applications, in general, there are many products having not only a flat form but also a non-flat surface form such as a curved surface or an uneven surface. Therefore, as a film material, a hard polyvinyl chloride resin excellent in processability and moldability is used. Is mainly used. However, since the polyvinyl chloride resin has poor heat resistance, the product may be deformed when exposed to high temperatures, for example, when left in a car in the middle of summer. In addition, polyvinyl chloride resin is liable to generate toxic substances due to chlorine when incinerated after use, causing a problem of environmental pollution.

Also, called A-PET (trade name),
An unoriented polyethylene terephthalate film is used. Although it is excellent in moldability, it causes problems such as embrittlement when used for a long time, opacity and reduction in elongation. For the purpose of eliminating this drawback, Japanese Patent Application Laid-Open
Japanese Patent No. 279150 proposes a method using a non-oriented heat-crystallized polyethylene terephthalate film, but this film has a problem that it is inferior in processing such as embossability and formability.

[0005] Further, 1,4-cyclohexanedimethanol derivative copolymerized polyester has been proposed as a polyvinyl chloride substitute resin.
Although there is an improvement effect on the aging, when printed using ink etc., the polymer on the film surface is poor in durability to organic solvents such as easy dissolution by ink solvent etc. Insufficient dimensional stability such as the product is easily curled and deformed.

[0006]

SUMMARY OF THE INVENTION The present inventors have improved these drawbacks, and for example, in the field of food packaging, medicine packaging,
Films useful in the fields of laminate molding, IC, card materials for magnetic recording, agricultural fields, etc., especially useful for forming, laminating and transferring non-flat surfaces such as curved surfaces, uneven surfaces, etc. As a result of intensive studies to develop a film excellent in processability, moldability, stability over time, solvent resistance, and dimensional stability, as a result, a polyester layer A having a uniaxial stretching orientation structure and Stretched orientation structure has a structure in which a polyester layer B which has been made into a non-oriented structure by heat treatment is laminated, and the surface layer is composed of the polyester layer A,
A multilayer film having at least three layers, wherein (1) the melting point of the polyester constituting the layer A is at least 15 ° C. higher than the melting point of the polyester constituting the layer B, and (2) the total thickness (a) of the polyester layer A is A multilayer polyester film in which the ratio (a / b) of the total thickness (b) of the polyester layer B is 0.01 to 3 is particularly suitable for forming and processing, stability over time,
Solvent resistance, dimensional stability, etc. were found to be able to be dramatically improved, and furthermore, when this multilayer film was produced by a co-extrusion film forming method, it was found that it could be produced at low cost, and the present invention was completed. Reached.

Accordingly, an object of the present invention is to provide a food packaging field,
Provide multilayer polyester film with excellent processability, moldability, stability over time, solvent resistance and dimensional stability, which is particularly useful in the fields of chemical packaging, laminate molding, IC, card materials for magnetic recording, agriculture, etc. Is to do.

Another object of the present invention is to provide the above-mentioned multilayer polyester film at low cost.

[0009]

According to the present invention, it is an object of the present invention to provide a polyester layer A having a uniaxially stretched orientated structure and a polyester having a uniaxially stretched orientated structure which is non-oriented by heat treatment. A multilayer film having a laminated structure with a layer B and having a surface layer made of the polyester layer A and having at least three layers, wherein (1) the melting point of the polyester constituting the layer A is the melting point of the polyester constituting the layer B; (2) the ratio (a) of the total thickness (a) of the polyester layer A to the total thickness (b) of the polyester layer B
/ B) is 0.01 to 3 and is achieved by a multilayer polyester film.

According to a preferred embodiment of the present invention, (a) the multilayer film is a multilayer film produced by a co-extrusion film-forming method, and (b) the multilayer film is formed at a temperature higher than the melting point of the polyester constituting the layer B. Heat-treated,
(C) the multilayer film is composed of three layers of polyester layer A / polyester layer B / polyester layer A, and (d) the polyester layer B is composed of a dicarboxylic acid unit mainly composed of a terephthalic acid unit and a naphthalenedicarboxylic acid unit and an ethylene glycol unit. (E) the polyester layer B is composed of a polyester of a glycol unit mainly composed of a dicarboxylic acid unit mainly composed of terephthalic acid units and isophthalic acid units and a glycol unit mainly composed of ethylene glycol units, f) The polyester layer B is composed of a polyester of a dicarboxylic acid unit mainly composed of terephthalic acid units and a glycol unit mainly composed of ethylene glycol units and 1,4-cyclohexanedimethanol units, and (g) the polyester layer B is composed of terephthalic acid. Mainly unit To consist glycol unit of the polyester to the carboxylic acid units and ethylene glycol units and neopentyl glycol units as a main, and / or glass transition point of the polyester constituting the (h) layer B is 5
At least 00 ° C.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester constituting the layers A and B of the multilayer film in the present invention is a polyester capable of forming an oriented crystal structure by one or more stretching treatments after film formation.

The polyester constituting the layer A is not particularly limited, but polyesters whose main dicarboxylic acid units are composed of terephthalic acid and / or 2,6-naphthalenedicarboxylic acid units and whose main glycol units are ethylene glycol units are exemplified. preferable. The polyester may optionally be, for example, isophthalic acid,
Orthophthalic acid, 2,7-naphthalenedicarboxylic acid,
It may contain other carboxylic acid units such as 1,5-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 2,2-biphenyldicarboxylic acid, succinic acid, adipic acid, azelaic acid and sebacic acid. Also, for example, propylene glycol, 1,4-butanediol, 1,
It may contain other glycol units such as 5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, polyethylene glycol and polytetramethylene glycol.

As specific examples of the polyester constituting the polyester layer A, polyethylene terephthalate, polyethylene terephthalate obtained by copolymerizing a small amount of a third component,
Preferable examples include polyethylene-2,6-naphthalate and polyethylene-2,6-naphthalate obtained by copolymerizing a small amount of a third component.

The polyester constituting the polyester layer A has a melting point of at least 205 ° C., and more preferably at least 205 ° C.
It is preferably 70 ° C. or lower. Here, the melting point is
This is the melting endothermic peak temperature when the sample that has been melted once, quenched, and solidified is then heated at a rate of 10 ° C./min with a differential calorimeter. Further, the glass transition temperature of the polyester is preferably 60 ° C. or more, more preferably 70 ° C. or more from the viewpoints of dimensional stability, deformation resistance and curling resistance. Here, the glass transition temperature refers to a structural change (specific heat change) temperature when a polyester, once melted, rapidly cooled and solidified, is heated at a rate of 10 ° C./min with a differential calorimeter. .

As described above, the polyester constituting the polyester layer B is a polyester which forms an oriented crystal structure by uniaxial stretching treatment after film formation, similarly to the polyester constituting the layer A. It has a melting point at least 15 ° C. lower than the melting point of the polyester constituting the layer A, preferably at least 25 ° C. or lower, more preferably at least 35 ° C. lower. This melting point is preferably 190 ° C. or more, more preferably 190 ° C. or more and 250 ° C. or less. Further, the glass transition temperature of the polyester constituting the layer B is 50 ° C. or more, more preferably 70 ° C., from the viewpoints of dimensional stability, deformation resistance and curling resistance of the film and the processed product.
It is preferable that it is above. In particular, in applications where products and the like are exposed to high temperatures, such as storage in a car in the summer, it is preferable to have a glass transition temperature of 80 ° C. or higher. Here, the melting point and the glass transition temperature are measured by the methods described above.

The composition of the polyester constituting the layer B is not particularly limited as long as it has the above properties.
Copolyesters whose main dicarboxylic acid units consist of terephthalic acid and / or naphthalenedicarboxylic acid units are preferred. Preferred examples of the secondary dicarboxylic acid unit of the copolyester include those exemplified as other dicarboxylic acid units of the polyester constituting the layer A, and examples of the glycol unit preferably include those exemplified as the glycol units of the polyester constituting the layer A. Can be.

Specific examples of the copolyester include:
Copolyester consisting of dicarboxylic acid units mainly consisting of terephthalic acid units and naphthalenedicarboxylic acid units and glycol units mainly consisting of ethylene glycol units, and mainly dicarboxylic acid units mainly consisting of terephthalic acid units and isophthalic acid units and ethylene glycol units A copolyester composed of glycol units composed mainly of terephthalic acid units and a copolyester composed of glycol units composed mainly of dicarboxylic acid units mainly composed of terephthalic acid units and ethylene glycol units and 1,4-cyclohexanedimethanol units, mainly composed of terephthalic acid units A copolyester comprising a dicarboxylic acid unit and a glycol unit mainly comprising an ethylene glycol unit and a neopentyl glycol unit is preferably exemplified. More preferably, a copolyester in which the terephthalic acid unit is 95 to 80 mol% and the 2,6-naphthalenedicarboxylic acid unit is 5 to 20 mol% in the dicarboxylic acid unit can be mentioned.

As described above, the melting point of the polyester layer A in the present invention needs to be at least 15 ° C. higher than the melting point of the polyester layer B, more preferably 25 ° C. or higher, particularly preferably 35 ° C. or higher. If the melting point difference between the polyester layer A and the polyester layer B is smaller than 15 ° C., it is difficult to optimize the temperature at which the heat treatment is performed.
That is, if the heat treatment temperature is too close to the melting point of the polyester layer B, the polymer of the polyester layer B does not melt sufficiently, and the change to the non-oriented structure is substantially insufficient. On the other hand, if the heat treatment temperature is too close to the melting point of the polyester layer A, the melting of the polyester layer A partially starts to occur. Troubles such as getting lost easily occur.

In the present invention, it is preferable that the polyester layer A and / or the polyester layer B contains 0.1 to 30% by weight of particles and / or polyolefin resin. Examples of the particles include talc, kaolin, calcium carbonate, amorphous silica, spherical silica, titanium oxide, barium sulfate, silicone, crosslinked polystyrene, carbon black, and the like. Examples of the polyolefin resin include polyethylene, polypropylene, and poly-4-methylpentene. And, for example, concealing properties, cards required matte surface and the like, in the field of packaging, etc., particles excellent in concealing properties,
For example, it is of course possible to include titanium oxide, barium sulfate, etc. for purposes other than imparting smoothness to the film. The average particle size of these additives is 0.05 to 5 μm, and further 0.1
It is preferably in the range of ３3 μm.

The polyester layer A and / or the polyester layer B in the present invention may further contain various additives as long as the object of the present invention is not impaired. For example, if necessary, components such as an elastomer resin such as polybutylene terephthalate-polytetramethylene glycol block copolymer, a pigment, a dye, a heat stabilizer, a flame retardant, a foaming agent, and an ultraviolet absorber can be contained.

The polyester constituting the polyester layers A and B in the present invention can be produced by a known method. Specific examples thereof include a method of reacting one or more dicarboxylic acid ester-forming derivatives with one or more glycols in a polyester production reaction step. 2
A method of melt-mixing and performing a transesterification reaction (redistribution reaction) by using a screw extruder, and the like. In these methods, if necessary, particles, polyolefin,
Other various additives can be contained in the polyester.

The multilayer film of the present invention has a laminated structure of a polyester layer A having a uniaxially stretched orientated structure and a polyester layer B having a uniaxially stretched orientated structure which is made non-oriented by heat treatment, and Although the surface layer is a multilayer film of at least three layers composed of the polyester layer A, usually, this heat treatment is performed in a state where the polyester layer A is laminated on both sides of the polyester layer B, and the temperature is lower than the melting point of the polyester of the layer A. It is performed at a temperature higher than the melting point of the polyester of B. As a result, the polyester in the layer B is temporarily melted, so that the oriented structure of the polymer in the layer B changes from a uniaxially stretched oriented structure to a substantially non-oriented structure. This heat treatment is preferably performed by setting the temperature during the heat setting treatment after the stretching treatment in the co-extrusion film forming method to a temperature lower than the melting point of the polyester in the layer A and higher than the melting point of the polyester in the layer B. It can be carried out.

The layer structure of the multilayer polyester film in the present invention usually comprises a polyester layer A and a polyester layer B. For example, the polyester layer A is a surface layer,
And a three-layer structure of A / B / A (where / indicates a layer structure), in which the polyester layer B is an inner layer, A / B /
A multi-layer configuration such as an A / B / A type five-layer configuration, and a seven-layer, nine-layer, n + 1 configuration, and the like according to these orders can be given. Further, if necessary, when the polyester layer A has two or more layers, one or more layers can be composed of different polymers. The same applies to the case where there are two or more polyester layers B. For example, the polyester layer A is composed of two polymers (A
1, A2), and the polyester layer B is composed of two kinds of polymers (B
1, B2), A1 / B1 / A2 type 3
Examples thereof include a layer configuration and a five-layer configuration of A1 / B1 / A2 / B2 / A1 type. Of these layer configurations, 3
Layers, 5 layers are preferred, and 3 layers are particularly preferred.

The multilayer polyester film according to the present invention comprises a polyester layer A having a uniaxially stretched orientated structure.
Need to constitute the outermost layer. When the polyester layer B having a substantially non-oriented structure constitutes the outermost layer, when printing characters, images, and the like on the film surface with ink, the organic solvent is such that the film is partially dissolved by a solvent or the like and easily set off. In addition, there is a problem that the film is inferior in durability, and the film tends to stick to various rolls and the like in the process during the production of the film. Incidentally, on one or both surfaces of the outermost surface of the film, as long as the effects of the present invention are not impaired, the adhesion is improved,
For surface modification such as improvement of antistatic property and release property, surface treatment such as coating treatment and corona discharge treatment may be performed.
As a surface treatment method such as a coating treatment, a polyester coating agent, a urethane coating agent, an acrylic coating agent or the like is used alone or as a mixture, and is applied in the process of film production. A method of applying in a separate step later can be used.

The multilayer polyester film of the present invention is preferably produced by a co-extrusion film forming method. A specific example will be described for the case of the above-mentioned three-layer film (A / B / A). First, a polyester chip prepared for the polyester layer A is dried and melted. In parallel with this, the polyester chips prepared for the polyester layer B are dried and melted. Subsequently, these molten polymers are laminated into three layers inside the die, for example, laminated into three layers inside the die where the feed block is installed, and then cast on a cooling drum to form an unstretched multilayer film. The film is stretched in one or more directions along a vertical axis and / or a horizontal axis to obtain a multilayer stretched film having a uniaxially stretched orientation structure. The same can be applied to the case of five or more layers. The stretching treatment is performed under the condition that the polyester layer A forms a desired orientation structure. For example, Tg (glass transition temperature) of polyester constituting the layer A is −10 ° C. to Tg + 50.
At a temperature (Tc) of 2.5 ° C., stretching 2.5 times or more, preferably 3 to 6 times in the machine direction, and then from Tc + 5 ° C. to Tc + 50 ° C.
At a temperature of 2.5 times or more, preferably 3 to 6 times in the transverse direction. This stretching is preferably 8 times or more, more preferably 9 times or more in area magnification. The stretching may be performed by a simultaneous biaxial stretching method.

The multilayer stretched film obtained as described above is further subjected to a heat treatment. It is important that the heat treatment temperature is a temperature higher than the melting point of the polyester layer B. By this heat treatment, the polymer of the polyester layer B is melted, and the stretched orientation structure formed by uniaxial or more stretching treatment is It changes to a substantially non-oriented structure. The heat treatment temperature is
Preferably, the temperature is at least 5 ° C. higher than the melting point of the polyester layer B and at least 10 ° C. lower than the melting point of the polyester layer A. The heat treatment gives the polyester layer A an effect of, for example, heat setting. The heat treatment method is not particularly limited, and examples thereof include a method of performing a heat treatment in a process immediately after stretching during film production, a method of winding the film into a roll after completion of the film production, and a method of performing a heat treatment in another step.

In the multilayer polyester film of the present invention, a polyester layer A having a uniaxial or more stretched orientation structure
And the ratio (a / b) of the total thickness (b) of the polyester layer B having a substantially non-oriented structure to the total thickness (a) of the polyester layer B is 0.01 to
3, preferably 0.03 to 2, more preferably 0.03
5 to 1. This thickness ratio is, for example, 3 of the layer configuration A1 (thickness: a1) / B (thickness: b) / A2 (thickness: a2).
When it is composed of layers, it means that the total thickness ratio (a / b) of layer A and layer B, that is, (a1 + a2) / (b) is 0.01 to 3 and the layer configuration is A1 (thickness). : A1) / B1
(Thickness: b1) / A2 (thickness: a2) / B2 (thickness: b
2) In the case of five layers of / A3 (thickness: a3), the total thickness ratio (a / b) of layer A and layer B, that is, (a1 + a2 + a)
3) means that (b1 + b2) is 0.01 to 3; If the total thickness ratio (a / b) is less than 0.01, the outermost layer thickness of the polyester layer A is small, so that it is difficult to control the thickness during film production, and it is easy to partially expose the polyester layer B to the surface layer. This causes problems and the dimensional stability of the film is insufficient. On the other hand, when the total thickness ratio exceeds 3, the polyester layer B having a substantially non-oriented structure
Because of the low proportion of, the workability and flexibility of the film are insufficient when the film is deformed by molding, embossing, or the like, or when the film is used while being held between holding brackets.

The total thickness of the multilayer polyester film is preferably 10 to 3000 μm, more preferably 50 to 2000 μm, and particularly preferably 100 to 1000 μm. In addition,
When this multilayer film is used as a product, it may be used alone, or two or more films may be laminated and laminated. In the case of this lamination, the thickness is appropriately determined depending on the number of layers to be laminated, the total thickness, reasons for use, etc., but is 100 to 5000 μm in total, and 200 to 2000 μm in total.
A thickness of μm is preferred.

The multilayer polyester film of the present invention is a film excellent in processability, moldability, stability over time, solvent resistance, and dimensional stability. It is suitable for magnetic recording card materials, agricultural fields, and the like. In particular, of these uses, it is suitable for forming, laminating, and transferring not a flat body but a curved surface, an uneven surface such as an uneven surface, and a three-dimensional structure such as a tray and an ice cream cup. In the food packaging field, capsules, tablets, etc.
In the TP medicine packaging field, furniture, electrical appliances, automotive parts, etc., when laminating a film with wood, metal, resin, rubber or after laminating, bending, curved surface processing,
In the field of forming three-dimensionally by unevenness processing, blow molding, etc., furniture, electric appliances, automobile parts, etc., curved surfaces,
In the field of transfer foil, such as transfer to a non-flat three-dimensional surface such as an uneven surface, in cash cards, ID cards, credit cards, etc., characters and patterns are embossed, and / or
Or embedded processing of magnetic tape, IC chip, etc.,
In the field of magnetic recording cards, IC recording card materials, and greenhouses, it can be preferably used in the field of agriculture in which frames and clips are used.

[0030]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In addition, the measuring method and evaluation method of the characteristics used in the examples and comparative examples are as follows.

(1) Evaluating Formability-1 The film is pressed against an embossing roller to prepare an embossed film having an embossment having an Rz of 500 μm on the front surface. Here, Rz is the average of the first to fifth peaks and the first to fifth valleys of the straight line parallel to the average line of the portion extracted by the reference length from the cross-sectional curve. It indicates the distance from the average in μm. ：: Even when embossing was applied, no cracking occurred in the embossed film. ：: When embossing is applied, fine cracks occur in the embossed film. X: A large crack occurs in the embossed film during embossing.

(2) Evaluation of moldability-2 PTP (Push through Package) having a heating plug
The film is press-molded at 130 ° C. by a molding machine to prepare a pack film in which pockets having a length of 20 mm, a width of 10 mm, and a depth of 10 mm are provided at intervals of 10 mm. A: The shape of the pocket is the same as that of the mold, and there is no wrinkle in the film between the pockets. ：: The shape of the pocket was the same as the mold, but the film between the pockets had some wrinkles. ×: There are wrinkles in the pockets, and some of the shapes are not the same as the mold. Further, the film between the pockets is often wrinkled.

(3) Evaluation of printability Using an ink in which a pigment is dispersed with methyl ethyl ketone, continuous printing is performed on one side of a film roll using a gravure roll. A: No ink was transferred from the printing surface to the opposite side of the film roll from the printing side (the non-printing side). ：: The transfer of the ink from the printing surface is fine on the opposite side of the printing of the film roll (non-printing surface). X: The transfer of the ink from the printing surface is on the front surface of the film roll opposite to the printing surface (non-printing surface). This printability evaluation is an alternative to the solvent resistance evaluation.

Example 1 A transesterification reaction and a polycondensation reaction were carried out in a conventional manner using dimethyl terephthalate and ethylene glycol as starting materials and manganese acetate, phosphoric acid and antimony trioxide as catalysts. The resulting polymer is discharged from the reactor and cooled, and pellets of polyethylene terephthalate (hereinafter referred to as PET)
I got

Similarly, except that 75 mol% of dimethyl terephthalate (based on all acid components), 15 mol% of dimethyl 2,6-naphthalenedicarboxylate (based on total acid components) and ethylene glycol are used as starting materials. PET
A transesterification reaction and a polycondensation reaction are carried out in the same manner as described above, and the obtained polymer is discharged from the reactor and cooled, and pellets of copolymerized polyethylene terephthalate (hereinafter CO-P
ET).

PET and CO-PET obtained above
Are separately dried and melted by a single screw extruder, then the molten polymer is laminated on three layers of PET / CO-PET / PET inside the die, and then cast on a cooling drum in this state to obtain an unstretched multilayer film. I got Then,
Stretching the multilayer film 3.2 times at 110 ° C. in the machine direction,
Further, after stretching 3.4 times in the transverse direction at 120 ° C., 235
The resultant was heat-set at ℃ to obtain a three-layer film. The thickness configuration of this three-layer film was a total of 120 μm in which the surface layers (polyester layer A) on both sides made of PET were 10 μm and the inner layer (polyester layer B) made of CO-PET was 100 μm.
Table 1 shows the properties and results of the obtained three-layer film.
Good results were obtained in both molding and printing.

[Examples 2 to 7, Comparative Examples 1 to 3] Using a polyester having the composition shown in Table 1, the same procedure as in Example 1 was carried out to obtain a three-layer film. Table 1 shows the properties of the obtained three-layer film. As is clear from Table 1, all the examples satisfying the conditions of the present invention obtained good results. On the other hand, in Comparative Example 1, when the difference in melting point between the polyester layer A and the polyester layer B was small, and the heat setting temperature exceeded 235 ° C., a part of the film was melted during the production of the film, and adhered to a roll or the like. In Comparative Example 2, since the heat setting temperature was lower than the melting point of the polyester layer B, the polyester layer B was not melted, the change to the non-oriented structure was substantially insufficient, and the moldability was poor. Further, in Comparative Example 3, since the polyester layer A was amorphous, adhesion to a roller or a clip occurred during stretching, and a roll-shaped product was easily fused, and the printability evaluation was poor. was there.

Example 8 CO-PET Constituting the Inner Layer
Example 1 was repeated except that 85 parts by weight of PET of Example 1 and 15 parts by weight of polyethylene-2,6-naphthalate pellets separately prepared were mixed, dried, melted, and transesterified (redistributed). Similarly to the above, the molten polymer was laminated on three layers of PET / CO-PET / PET inside the die, cast on a cooling drum in this state, and then stretched and heat-set to obtain a three-layer film. The properties of the obtained three-layer film were the same as those of Example 1, and good results were obtained in both molding and printing.

Example 9 CO-PET Constituting the Inner Layer
10% by mole of 2,6-naphthalenedicarboxylic acid
A mixture obtained by mixing, drying, melting, and transesterifying (redistributing) 50 parts by weight of copolymerized polyethylene terephthalate pellets and 50 parts by weight of copolymerized polyethylene terephthalate pellets obtained by copolymerizing 20% by mole of isophthalic acid. Except for using, the molten polymer was laminated on three layers of PET / CO-PET / PET inside the die and cast on a cooling drum in this state, then stretched and heat-set to obtain A layer film was obtained.
The properties of the obtained three-layer film were the same as those of Example 3, and good results were obtained in both the forming process and the printing evaluation.

[Example 10] PET of Example 1 was used as the polyester constituting the layer A, and 2,6-naphthalenedicarboxylic acid was used as the polyester constituting the layer B.
Mol-% copolymerized polyethylene terephthalate pellets (hereinafter referred to as CO-PET-1) and 1,4-cyclohexane dimethanol copolymerized polyethylene terephthalate pellets (hereinafter referred to as CO-P).
ET-2), dried separately, melted with a single screw extruder, and then PET
/ CO-PET-1 / PET / CO-PET-2 / PE
The molten polymer was laminated on five layers of T, and cast on a cooling drum in this state to obtain a five-layer unstretched film.
Subsequently, the five-layer unstretched film was stretched 3.2 times in the longitudinal direction at 110 ° C., further stretched 3.4 times in the transverse direction at 120 ° C., and then heat-set at 235 ° C. to obtain a five-layer film. Was.
The thickness configuration of the five-layer film is such that the layer A made of PET is 10
The layer B composed of μm, CO-PET-1 and CO-PET-1 was 100 μm each, for a total of 230 μm. Regarding the characteristics of the obtained film, favorable results were obtained in both the molding process and the printing evaluation.

[0041]

[Table 1]

[0042]

Industrial Applicability The present invention is particularly useful in the fields of food packaging, medicine packaging, laminate molding, IC, card material for magnetic recording, agriculture, etc., and has excellent processability, moldability, stability over time, and solvent resistance. To provide a multilayer polyester film having excellent properties and dimensional stability.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4F100 AK41A AK41B AK41C AK42B BA03 BA06 BA10A BA10C BA16 BA25 EH20 EJ37A EJ37B EJ37C EJ38A EJ38B EJ38C EJ42 EK17 GB01 GB15 GB23 GB41 GB66 J01 JA04AJABJ04 JA05 JA04B05 YY00C 4F210 AA24 AA26 AG03 QA02 QA03 QC06 QG01 QG15 QG18 QW07

Claims (9)

[Claims] 1. A laminated structure of a polyester layer A having a uniaxially stretched oriented structure and a polyester layer B having a uniaxial stretched oriented structure non-oriented by heat treatment, and a surface layer of the polyester layer A A multilayer film comprising at least three layers comprising a layer A, wherein (1) the melting point of the polyester constituting the layer A is at least 15 ° C. higher than the melting point of the polyester constituting the layer B; Thickness (a) and total thickness of polyester layer B (b)
A multilayer polyester film having a ratio (a / b) of 0.01 to 3; 2. The multilayer polyester film according to claim 1, wherein the multilayer film is a multilayer film produced by a coextrusion film forming method. 3. The multi-layer film has been heat-treated at a temperature higher than the melting point of the polyester constituting Layer B.
Or the multilayer polyester film according to 2. 4. The multilayer polyester film according to claim 1, wherein the multilayer film comprises three layers of polyester layer A / polyester layer B / polyester layer A. 5. The polyester layer B according to claim 1, wherein the polyester layer B comprises a polyester having a dicarboxylic acid unit mainly composed of terephthalic acid units and naphthalenedicarboxylic acid units and a glycol unit mainly composed of ethylene glycol units. 2. The multilayer polyester film according to item 1. 6. The polyester layer according to claim 1, wherein the polyester layer B comprises a polyester having a dicarboxylic acid unit mainly composed of terephthalic acid units and isophthalic acid units and a glycol unit mainly composed of ethylene glycol units. The multilayer polyester film of the above. 7. The polyester layer B comprises a polyester of a dicarboxylic acid unit mainly composed of terephthalic acid units and a glycol unit mainly composed of ethylene glycol units and 1,4-cyclohexanedimethanol units.
Or the multilayer polyester film according to any one of 4. 8. The polyester layer B according to claim 1, wherein the polyester layer B comprises a polyester having a dicarboxylic acid unit mainly composed of terephthalic acid units and a glycol unit mainly composed of ethylene glycol units and neopentyl glycol units. 2. The multilayer polyester film according to item 1. 9. The multilayer polyester film according to claim 1, wherein the polyester constituting the layer B has a glass transition point of 50 ° C. or higher.