JPH0929914A - Biaxially stretched film for metal laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially stretched film excellent in impact resistance at low temp. and good in taste retaining properties and the adhesiveness with a metal panel by laminating a first layer composed of polyester and a second layer consisting of polyester and polycarbonate represented by a specific formula. SOLUTION: A first layer is composed of polyester containing ethylene terephthalate as a main repeating unit and a second layer is formed from a compsn. consisting of 20-60wt.% of polycarbonate substantially composed of a repeating unit represented by formula (wherein R<1> and R<2> are respectively a hydrogen atom, a 1-5C alkyl group or a cycloalkyl group having a 5-6C ring member, R<3> and R<4> are respectively a 1-5C alkyl group, a phenyl group or a halogen atom and m and n are respectively 0, 1 or 2) and 40-80wt.% of polyester. This polyester consists of 10-90wt.% of polyester containing ethylene terephthalate as a main repeating unit and characterized by that the concn. of a terminal carboxyl group is 10 equivalent/10<6> g or more and 10-90wt.% of polyester containing butylene terephthalate as a main repeating unit and characterized by that the concn. of a terminal carboxyl group is 20 equivalent/10<6> g or less.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a metal laminate 2
Regarding the axially stretched film, more specifically, it exhibits excellent formability when it is laminated with a metal plate and subjected to a can-making process such as drawing, and also has adhesiveness with the metal plate, aroma retention (flavorability), and low temperature. And a biaxially stretched film for metal laminate suitable for use in metal cans such as beverage cans and food cans, which are excellent in impact resistance and have good film-forming properties (extrusion moldability and stretchability).

[0002]

2. Description of the Related Art Metal cans have been generally coated to prevent corrosion of the inner and outer surfaces. Recently, organic solvents have been used for the purpose of simplifying the process, improving hygiene, and preventing pollution. The method of laminating a thermoplastic resin film on a metal plate such as tin, tin-free steel, aluminum, etc., and then drawing cans has been widely used. Is coming.
As such a thermoplastic resin film, a polyester film is usually used, and many proposals have been made so far.

For example, JP-A-56-10451 and JP-A-1-192546 disclose that a biaxially oriented polyethylene terephthalate film is laminated on a metal plate via an adhesive layer of a low-melting polyester to form a can-forming material. It is disclosed for use. However, although the biaxially oriented polyethylene terephthalate film is excellent in heat resistance and aroma retaining property (flavor property), its processability is insufficient and the film is whitened (small Occurrence of cracks) and fracture may occur.

[0004] Also, JP-A-1-192545 and JP-A-2-57339 disclose that a non-crystalline or extremely low-crystalline aromatic polyester film is laminated on a metal plate and used as a can-making material. It has been disclosed. However, an amorphous or extremely low-copolymerized aromatic polyester film has good moldability, but is inferior in fragrance retention (flavor), and can be used for printing after can-making, retort sterilization, and the like. It may be easily embrittled by post-treatment and further long-term storage, and the film may be easily broken by impact from the outside of the can.

The present inventors have conceived of using a copolymerized polyester film to solve such a problem, and have made various proposals so far.

As a result, the use of a specific copolymerized polyester film has solved the problems of molding processability, heat resistance, retort resistance, and fragrance retention (flavor), but the impact resistance at low temperatures has been reduced. However, the impact resistance, especially at a low temperature of 5 ° C. or less, has not been sufficient, and there is room for improvement. Poor impact resistance at low temperatures means that if the product is handled in a cooled state, such as a metal can for juice or soft drinks, the film may crack when dropped and impacted. Is a big problem.

On the other hand, in order to solve such a problem of the polyester film, that is, the problem of poor impact resistance at low temperatures, it has been proposed to use a film in which polyester and polycarbonate are blended ( JP-A-6-255022. When such a blend film is used, the impact resistance at low temperatures is certainly improved, but a new problem arises in that the fragrance retention (flavor) and the adhesion to a metal plate are poor. Further, at the time of extrusion molding, pulsation of the discharged molten polymer, which is called "melt run-out", occurs, and a film having a uniform thickness cannot be obtained. This tendency becomes remarkable as the extrusion molding speed increases, and Extrusion molding becomes difficult.
In addition, when the extruded film is stretched in order to enhance the impact resistance, there is a problem that the film is broken and satisfactory stretching cannot be performed, so that it is difficult to use the film as a biaxially stretched film.

[0008]

DISCLOSURE OF THE INVENTION The present invention solves the problems of the prior art, especially the problems of the film composed of a blend composition of polyester and polycarbonate, and has excellent impact resistance at low temperature. In addition, the biaxially stretched film for metal laminate has good taste retention (flavor), good adhesion to a metal plate, and good film formability (extrusion moldability, stretchability). This is an issue.

[0009]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the inventors of the present invention blended a first layer made of a specific polyester and a polyester and a polycarbonate in a specific ratio. The present invention has been found that a two-layer film is formed by laminating two layers, and the polyester of the second layer may be a mixed polyester of a polyethylene terephthalate-based polyester having a specific terminal carboxyl group concentration and a polybutylene terephthalate-based polyester. Has been completed.

That is, according to the present invention, the first layer (A) comprising a polyester having ethylene terephthalate as a main repeating unit, and 20 to 60% by weight of a polycarbonate substantially consisting of a repeating unit represented by the following general formula (1): And 40 to 80% by weight of polyester, the polyester having ethylene terephthalate as a main repeating unit and 10 to 90% by weight of a polyester having a terminal carboxyl group concentration of 10 equivalents / 10 ⁶ g or more, and butylene terephthalate. And a second layer (B) comprising 10 to 90% by weight of a polyester having a terminal carboxyl group concentration of 20 equivalents / 10 ⁶ g or less as a main repeating unit. It is a stretched film.

[0011]

Embedded image

(Here, R ¹ and R ² are each a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a ring member having 5 to 5 carbon atoms.
And R ¹ and R ² may form a cycloalkyl group having 5 to 6 ring members together with the carbon atom to which they are attached, and R ³ and R ⁴ each have 1 to 5 carbon atoms. Represents an alkyl group, a phenyl group or a halogen atom, and m and n are each 0, 1 or 2. )

In the present invention, the first layer (A) and the second layer (A)
The polyester having ethylene terephthalate as the main repeating unit used in the layer (B) is a polyester having at least 85 mol% ethylene terephthalate,
Preferably 90 mol% or more, more preferably 95 mol%
The above is the polyester composed of ethylene terephthalate.

In these polyesters, the components which can be copolymerized as the third component include, for example, acid components such as aromatic dicarboxylic acids such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid, adipic acid, azelaic acid and sebacine. Acids, aliphatic dicarboxylic acids such as decane dicarboxylic acid, and alicyclic dicarboxylic acids such as cyclohexane dicarboxylic acid.Alcohol components include diethylene glycol, butanediol, aliphatic diols such as hexanediol, and fatty acids such as cyclohexanedimethanol. A cyclic diol can be mentioned. These can be used alone or in combination of two or more.

These polyesters have a melting point of 200 ° C.
And more preferably a melting point of 210
℃ or above. It is not preferable to use a polyester having a low melting point, since a film having poor heat resistance and impact resistance is obtained.

The above polyester has an intrinsic viscosity of preferably 0.5 to 0.9, particularly preferably 0.6 to 0.8, measured at 35 ° C. in orthochlorophenol.

These polyesters can be produced by a conventionally known melt polymerization method. As a catalyst, a germanium (Ge) compound catalyst or titanium (T
i) A compound catalyst is preferably used, and the polymerization method is also preferably solid phase polymerization from the viewpoint of oligomer reduction. In particular, when mixed with polycarbonate and melted, antimony (S
b) When a polyester polymerized with a compound catalyst is used,
Since the decarboxylation reaction is promoted, carbon dioxide gas is generated, and bubbles are generated, it is preferable to avoid using an Sb compound catalyst.

In the present invention, the polycarbonate used for the second layer (B) substantially consists of the repeating unit represented by the above formula (1). In the above formula (1), R ¹
And R ² are each a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a cycloalkyl group having 5 to 6 ring members, or R ¹ and R ² are taken together with the carbon atom to which they are bonded. A cycloalkyl group having 5 to 6 ring carbon atoms may be formed.

The alkyl group having 1 to 5 carbon atoms may be linear or branched, for example, ethyl, n-propyl, iso-propyl, n-butyl, i-butyl.
Examples thereof include so-butyl and pentyl.

Examples of the cycloalkyl group having 5 to 6 ring carbon atoms include cyclopentyl and cyclohexyl.

R ³ and R ⁴ are an alkyl group having 1 to 5 carbon atoms, a phenyl group or a halogen atom, respectively. Examples of the alkyl group having 1 to 5 carbon atoms are the same as those described above. As a halogen atom,
For example, fluorine, chlorine, bromine and the like can be mentioned.

M and n are each 0, 1 or 2.

As the repeating unit represented by the above formula (1), for example, a bisphenol A type carbonate unit in which R ¹ and R ² are methyl and m and n are 0 can be exemplified as preferable ones.

The polycarbonate used in the present invention is:
It can be composed of the same repeating unit represented by the above formula (1), or can be composed of two or more different repeating units represented by the above formula (1).

Polycarbonates are usually prepared by reacting a corresponding dihydric phenol with a carbonate precursor such as phosgene in the presence of a known acid acceptor or molecular weight regulator in a solvent such as methylene chloride (interfacial polymerization method). Alternatively, it is produced by a transesterification reaction (melt polymerization method) of a corresponding dihydric phenol and a carbonate precursor such as diphenyl carbonate.

The method for producing the carbonate used in the present invention is not particularly limited. For example, it can be produced by the following method. That is, (a) a method in which a dihydric phenol is excessively reacted with a carbonate precursor when producing by an interfacial polymerization method, (b) a method in which terminal blocking is carried out in producing by an interfacial polymerization method, (c) A method of adjusting the ratio of a dihydric phenol and a carbonate precursor when producing by a melt polymerization method; (d) a method of adding a polyhydroxy compound at a later stage of the polymerization reaction when producing by a melt polymerization method;
(E) A terminal OH content of less than 20 mol / 10 ⁶ g of polycarbonate and an appropriate amount of a dihydric phenol are melt-mixed, and if necessary, a catalyst is added to react the polycarbonate with the dihydric phenol to obtain a terminal OH content. And the like.

The above polycarbonate has a viscosity average molecular weight of 10,000 to 40,000, more preferably 10,000 to 40,000.
It is preferably 35,000.

Further, in the second layer (B) of the biaxially stretched film of the present invention, the polyester having ethylene terephthalate as a main repeating unit is a polyester having at least 85 mol% of butylene terephthalate, and preferably. 90 mol% or more, more preferably 95
A polyester having a mol% or more of butylene terephthalate.

In the polyester, the component which can be copolymerized as the third component is, for example, an acid component such as aromatic dicarboxylic acid such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid, adipic acid, azelaic acid and sebacic acid. , Aliphatic dicarboxylic acids such as decane dicarboxylic acid, and alicyclic dicarboxylic acids such as cyclohexane dicarboxylic acid. In the alcohol component, aliphatic diols such as diethylene glycol, butane diol, and hexane diol, and alicyclic rings such as cyclohexane dimethanol. Group diols. These alone,
Alternatively, two or more kinds can be used in combination.

These polyesters have a melting point of 200 ° C.
And more preferably a melting point of 210
℃ or above. It is not preferable to use a polyester having a low melting point because the resulting film has poor heat resistance and impact resistance.

The polyester has an intrinsic viscosity of 0.6 to 0.3 as measured at 35 ° C. in orthochlorophenol.
It is preferably 1.6, and particularly preferably 0.7 to 1.5.

Also in the case of this polyester, it is preferable to produce it by a solid phase polymerization method using a Ge compound catalyst or a Ti compound catalyst as in the case of the above-mentioned polyester containing ethylene terephthalate as a main repeating unit. Ge compounds include (a) amorphous germanium oxide, (b)
Fine crystalline germanium oxide, (c) a solution of germanium oxide dissolved in glycol in the presence of an alkali metal or alkaline earth metal or a compound thereof, (d)
A solution obtained by dissolving germanium oxide in water is preferably used. Preferred examples of the Ti compound include titanium tetrabutoxide and titanium acetate.

Second layer (B) of the biaxially stretched film of the present invention
The polyester having ethylene terephthalate as the main repeating unit used in 1) needs to have a terminal carboxyl group concentration of 10 equivalents / 10 ⁶ g or more, preferably 12 equivalents / 10 ⁶ g or more, more preferably 15 equivalents / It is preferable that the concentration is 10 ⁶ g or more, and the terminal carboxyl group concentration is 30 equivalents / 10 ⁶ g or less.
If the terminal carboxyl group concentration is less than 10 equivalents / 10 ⁶ g, the dispersion with the polycarbonate is poor, and the film stretching treatment is difficult. In an extreme case, the film cannot be stretched.

Furthermore, in the second layer (B) of the biaxially stretched film of the present invention, the polyester having butylene terephthalate as the main repeating unit, which is used as a mixture with the polyester having ethylene terephthalate as the main repeating unit, is used.
It is necessary that the terminal carboxyl group concentration is 20 equivalents / 10 ⁶ g or less, preferably 17 equivalents / 10 ⁶ g or less, and more preferably 15 to 5 equivalents / 10 ⁶ g.

The polyester containing butylene terephthalate as the main repeating unit improves the dispersibility of the polycarbonate in the polyester phase, reduces the "melt runout" during extrusion molding and the breakage during stretching, and improves the film forming property. Although it functions, when the terminal carboxyl group concentration of the polyester is higher than 20 equivalents / 10 ⁶ g, the effect of improving the dispersibility with the polycarbonate and improving the film-forming property is not exhibited.

Although the polycarbonate contained in the second layer (B) has a terminal hydroxyl group, when the second layer (B) is adhered to a metal plate, this terminal hydroxyl group contributes to this adhesiveness. Therefore, the total concentration of the terminal hydroxyl groups of the polycarbonate and the polyester is preferably at least 25 equivalent / 10 ⁶ g. More preferably, the total concentration of the terminal carboxyl group and the terminal hydroxyl group is at least 30 equivalent / 10 ⁶ g, and even more preferably 40 to 200 equivalent / 10 ⁶ g.

The second layer (B) of the biaxially stretched film of the present invention must be formed of a composition containing 20 to 60% by weight of the above-mentioned polycarbonate and 40 to 80% by weight of polyester. . If the proportion of polycarbonate exceeds 60% by weight, "melt runout" during extrusion molding,
Breakage frequently occurs during stretching, and film formability deteriorates. On the other hand, if the content of polycarbonate is less than 20% by weight, the impact resistance at low temperatures is not improved.

Further, the above-mentioned polyester used in the second layer (B) is 10 to 90% by weight of the above-mentioned ethylene terephthalate as the main repeating unit and 10 to 90% by weight of the above-mentioned butylene terephthalate as the main repeating unit. Must consist of%. When the proportion of the polyester having butylene terephthalate as a main repeating unit exceeds 90% by weight of the polyester component of the second layer (B), the film becomes colored, and further reacts with the polycarbonate, thereby decarbonating. Carbon dioxide gas is generated and bubbles enter, making film formation difficult. Conversely, if the content is less than 10% by weight, the dispersibility of the polycarbonate in the polyester phase cannot be improved, and the effect of reducing "melt run-out" during extrusion molding and breaking during stretching cannot be achieved. . The compounding ratio (P) of a polyester (PET) having ethylene terephthalate as a main repeating unit and a polyester (PBT) having butylene terephthalate as a main repeating unit.
(ET / PBT) is (20-85% by weight) / (15-80% by weight).
% By weight), and more preferably (40 to 80% by weight) / (20 to 60% by weight).

In the biaxially stretched film of the present invention, the composition forming the second layer (B) is 20 to 100 ppm, preferably 40 to 100 ppm, more preferably 40 to 50 p.
It is desirable to contain a phosphorus compound of pm. This phosphorus compound suppresses the reaction between the polycarbonate and the polyester, and prevents the generation of carbon dioxide gas due to the coloring or decarboxylation of the film.However, when the content is too large, butylene terephthalate is a main repeating unit. The effect of improving the dispersibility of the polycarbonate by the resulting polyester is impaired, and the film forming property is reduced.

The phosphorus compound used here may be an inorganic phosphorus compound or an organic phosphorus compound, such as phosphorous acid, phosphoric acid, pyrophosphoric acid, metaphosphoric acid and salts thereof.
Examples thereof include di- or tri-alkyl phosphines, di- or tri-aryl phosphines, mono- or di-alkyl phosphinic acids, mono- or di-aryl phosphinic acids, phosphites, phosphates, and polyphosphoric acid. Of these, (phosphite) and (phosphite) ester are preferable.
Examples of the ester include lower alkyl (for example, methyl and ethyl) esters, phenyl ester, and glycol (for example, ethylene glycol) esters.

These phosphorus compounds may be contained during the production of polyester and / or polycarbonate, or may be added to and mixed with the composition during melt extrusion.

The first layer (A) of the biaxially stretched film of the present invention
In the composition consisting of the polyester forming polyester and / or the polycarbonate forming the second layer (B) and the polyester, if necessary, an antioxidant, a heat stabilizer, an ultraviolet absorber, a plasticizer, inorganic particles, an organic compound, Additives such as particles and antistatic agents can be dispersed and compounded.

Further, in the biaxially stretched film of the present invention, in order to improve the handleability (winding property) in the film manufacturing process, fine particles having an average particle size of 2.5 μm or less are added to the first layer (A) in each layer. It is particularly recommended to add 0.01 to 1% by weight to 100% by weight of the composition comprising the polyester to be formed and / or the polycarbonate to form the second layer (B) and the polyester.

The lubricant may be inorganic or organic, but is preferably inorganic. Examples of the inorganic lubricant include silica, alumina, titanium dioxide, calcium carbonate, barium sulfate and the like, and examples of the organic lubricant include cross-linked polystyrene particles,
Examples include crosslinked silicone resin particles. In any case, the average particle diameter is desirably 2.5 μm or less. When the average particle diameter of the lubricant exceeds 2.5 μm, coarse lubricant particles (for example, particles having a diameter of 10 μm or more) of a portion deformed by molding work have a starting point. And a pinhole may be formed or, in some cases, broken.

In particular, a preferable lubricant in terms of pinhole resistance is a monodisperse lubricant having an average particle size of 2.5 μm or less and a particle size ratio (major axis / minor axis) of 1.0 to 1.2. It is a lubricant. Examples of such a lubricant include spherical silica, spherical tin dioxide, spherical zirconium, and spherical crosslinked silicone resin particles.

The biaxially stretched film of the present invention has a structure in which a first layer (A) made of polyester and a second layer (B) made of polycarbonate and polyester are laminated. By taking such a structure, the second layer (B)
Is laminated to a metal plate so that the first layer (A) is in contact with the metal plate, and the first layer (A) is made into a container so that the first layer (A) is in contact with the contents of the metal can. By protecting the fragrance with the first layer (A) having a good aroma retaining property (flavor property), the aroma retaining property (flavor property) of the entire film is improved, and the scent component of the contents of the metal can is adsorbed on the film. , The flavor of the contents is not affected by the odor of the film.

The biaxially stretched film having such a two-layer structure is obtained by, for example, separately melting the polyester and the composition of the polycarbonate and the polyester constituting the respective layers, coextruding them, and laminating and fusing them before solidification. After that, it can be produced by a method of biaxially stretching and heat setting, a method of separately melting and extruding a composition of polyester and polycarbonate and polyester into a film, and stretching and then fusion-bonding the both.

Examples of the biaxial stretching method include a sequential biaxial stretching method, a simultaneous biaxial stretching method and an inflation method.

The film of the present invention thus obtained has a total film thickness of 5 to 100 μm, particularly 10 to 75 μm.
m, and the thickness ratio of the first layer (A) and the second layer (B) (A /
B) is preferably 1/99 to 50/50.
The thickness ratio (A / B) is further preferably 5/95 to 40/60, and particularly preferably 10/90 to 30/70.

The biaxially stretched film of the present invention is the first
It is preferable that the plane orientation coefficients of the layer (A) and the second layer (B) are each 0.05 to 0.10, and the heat shrinkage rate of the entire film at 150 ° C. is 10% or less.

Here, the plane orientation coefficient is defined by the following equation.

[0052]

F = [(n _x × n _y ) / 2] −n _{z In the} above formula, f: plane orientation coefficient, n _x , n _y , n _z :
These are the refractive indices in the horizontal, vertical and thickness directions of the film, respectively.

The refractive index is measured as follows. A polarizing plate analyzer is attached to the eyepiece side of the Abbe refractometer, and each refractive index is measured with a monochromatic NaD line. The mounting solution uses methylene iodide, and the measurement temperature is 25 ° C.

If the orientation coefficient is too small, problems such as cracking tend to occur when the deep drawing ratio in deep drawing becomes high, and conversely, if it is too large, fracture during deep drawing tends to occur.

The heat shrinkage was 150 at the room temperature with two mark points (intervals of about 10 cm) on the sample film.
C. in a hot air circulating oven at 30 ° C. for 30 minutes, then return to room temperature, measure the distance between the above marked points, determine the difference before and after the temperature was kept at 150 ° C., and compare this difference with the temperature before the temperature was kept at 150 ° C. It is calculated from the reference point interval.

If the heat shrinkage (150 ° C.) of the film is too large, the dimensional shrinkage when bonded to a metal plate is large, and defects such as wrinkling of the film are likely to occur.

The above-mentioned plane orientation coefficient and thermal shrinkage (150
C.) to obtain a biaxially stretched film, for example, in sequential biaxial stretching, the longitudinal stretching ratio is from 2.5 to 3.6 times, and the transverse stretching ratio is from 2.7 to 3.6 times. From the range
Heat setting temperature is 150 to 220 ° C, preferably 160 to 2
Select from the range of 00 ℃, combine these and stretch,
It should be heat fixed.

As the metal plate to which the biaxially stretched film of the present invention is attached, particularly as a metal plate for can making, tin, tin-free steel, aluminum and the like plates are suitable. For bonding the film to the metal plate, for example, the following (a),
The method (a) can be used.

(A) The metal plate is heated to a temperature higher than the softening temperature of the film, the film is bonded, and then cooled and adhered.

(A) An adhesive layer is primer-coated on a film in advance, and this surface is bonded to a metal plate. As the adhesive layer, a known resin adhesive, for example, an epoxy adhesive, an epoxy-ester adhesive, an alkyd adhesive, or the like can be used.

When the biaxially stretched film of the present invention is attached to a metal plate, impact resistance is improved, adhesion to the metal plate is improved, and aroma retention (flavor property) is improved. The second layer (B) made of the composition of polycarbonate and polyester is located on the side that is exposed to the impact and contacts the metal plate, and the first layer (A) that is made of polyester on the side that contacts the contents of the metal can. It is preferable to bond them so that () is located. For example, when bonding the film of the present invention to the inside of a metal can, the second layer (B) may be bonded to the can.

Further, in the biaxially stretched film of the present invention, if necessary, between the first layer (A) and the second layer (B),
Further, another additional layer may be laminated on one surface.

[0063]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. In the examples, “part” means “part by weight”. The measurement of the characteristic values of polyester and polycarbonate and the evaluation of the film were performed as follows.

(1) Intrinsic viscosity [η] of polyester Measured in orthochlorophenol at 35 ° C.

(2) Melting point (Tm) and glass transition temperature (Tg) of polyester Measured by DSC.

(3) Concentration of terminal carboxyl group of polyester In a mixed solvent of phenol: tetrachloroethane = 2: 3, tetrabromophenol blue is used as an indicator and N
Titration was performed with a solution of aOH in benzyl alcohol.

(4) Viscosity average molecular weight (Mv) of polycarbonate Calculated from the intrinsic viscosity ([η]) measured in a methylene chloride solution using the following Schnell equation.

[0068]

[Equation 2]

(5) Terminal hydroxyl group concentration of polycarbonate Color measurement by interaction between TiCl ₄ and terminal hydroxyl group (Die Makromol. Chem. 88 (1965) 215)
).

(6) Extrusion Moldability of Film The discharge state of the molten polymer was observed and evaluated according to the following criteria. ⊚: Melt runout does not occur and extremely stable extrusion molding is possible. ：: Slight extrusion does not occur and stable extrusion molding is possible. Δ: Melt run-out sometimes occurred, and extrusion molding was unstable. ：: Melt runout frequently occurs, and substantially stable extrusion cannot be performed.

(7) Stretchability of Film The stretched state of the film was observed and evaluated according to the following criteria. ◎: No break occurs and extremely stable stretching is possible. ：: Little breakage occurs and stable stretching is possible. Δ: Occasional breakage occurred and stretching was unstable. ×: Many breaks occurred, and substantially stable stretching was not possible.

(8) Peel strength Between two sheets of 210 μm-thick steel plates obtained by electrolytically treating the same two films with electrolytic chromic acid so that the layer whose peel strength should be evaluated is on the outside (the side in contact with the metal plate). Overlaid on 285
At a pressure of 20 kg / cm ² with a hot press
By holding for 0 second, it was laminated with a steel plate. The laminate was cut into a size of 10 mm in width and 50 mm in length to prepare a test piece. This test piece has one end 2
A release agent was previously adhered to 0 mm so that the laminate plate was easily peeled off, and two steel plates were peeled in opposite directions at a portion of 20 mm on the side of the test piece where the release agent was adhered. It was T-shaped, and both ends of the peeled portion were fixed with a tensile tester, and the peel strength was measured at a pulling speed of 20 mm / min. (According to JIS K 6854).

(9) Low temperature impact resistance One film and one film were prepared by the same method as described in (8).
A laminated plate is manufactured from steel sheets. After the production, the laminate was kept in water at 50 ° C. for 5 days, and then the laminated plate was kept at 5 ° C.
An impact deformation test was performed according to the method described in JIS K5400.

That is, a shooting die having a radius of curvature of 5 mm was set on the upper surface of the laminated plate on which the film was not laminated, and a weight having a mass of 200 g was gravity dropped from the position of 20 cm in height onto the shooting die. At this time, a rubber plate having a thickness of 5 mm is provided below the laminate plate.

After this impact deformation test, one electrode was applied to the metal surface of the laminated plate on which the film was not laminated, and 1 was placed on the film surface of the other laminated plate at the position (convex portion) where the weight was dropped. % Cotton solution was applied, the other electrode was applied to the cotton, a voltage of 6 V was applied, and the current value at that time was measured. The smaller the current value (mA), the better the low-temperature impact resistance.

(10) Fragrance retaining property (flavor property) The laminated plate is cut into a disk shape having a diameter of 150 m / m, deep drawing is performed in four steps using a drawing die and a punch, and a side seamless container having a diameter of 55 mm. (Hereinafter, abbreviated as can) was created.

A metal can having a film laminated on the inner surface thereof was filled with a 20 ppm aqueous solution of d-limonene, left for 5 days, and then the film was peeled, cut into a size of 15 cm × 15 cm, and heat-treated at 80 ° C. for 30 minutes. The amount of adsorbed d-limonene per 1 g of the film was determined using gas chromatography. The smaller this value is, the better the fragrance retention (flavor) is. The adsorption amount was equal to or superior to that of polyethylene terephthalate. ○, slightly inferior to the left, Δ: inferior to the left.

Examples 1 to 9 and Comparative Examples 1 to 4 (Production of Polyester Film Layer (First Layer (A)) Polymer) Polyethylene terephthalate copolymerized with 12 mol% of isophthalic acid (intrinsic viscosity 0.64, Using a germanium dioxide catalyst and containing titanium dioxide having a particle size ratio of 1.1 and an average particle size of 0.3 μm in an amount of 0.3% by weight, a solid phase polymerization method was obtained. This polyester had a melting point of 229 ° C. and a glass transition temperature of 73 ° C.

(Production of Polycarbonate) A reaction vessel equipped with a vacuum distillation system having a stirrer and a nitrogen gas inlet was charged with 216 parts of diphenyl carbonate, 228 parts of bisphenol A and 0.05 part of diNa salt of bisphenol A. , And the operation of introducing nitrogen gas after vacuum degassing at room temperature was repeated three times to replace the reaction system with nitrogen. Next, after heating and reacting at 190 ° C. under normal pressure for 30 minutes, the pressure was gradually reduced at the same temperature to 50 mmHg after 60 minutes. Further, the reaction temperature was raised from 190 ° C. to 290 ° C. over about 60 minutes, and at the same time, the degree of vacuum was changed from 50 mmHg to 1 mmHg or less. As the reaction proceeded, phenol generated by the reaction was distilled off. The reaction was carried out under the same conditions for 40 minutes to obtain a polycarbonate having a viscosity average molecular weight (Mv) of 26,000 and a terminal hydroxyl group temperature of 73 equivalents / 10 ⁶ g.

(Production of Polycarbonate / Polyester Composition Film Layer (Second Layer (B)) Polymer and Production of Laminated Film) Polyester obtained by mixing the above polycarbonate with polyethylene terephthalate and polybutylene terephthalate in the proportions shown in Table 1. Table 1
Mix at the ratio shown in, and add phosphoric acid as a phosphorus compound at 60 p
pm (phosphorus concentration conversion) was added, and the first using a two-layer die
Two layers of unstretched film were extruded simultaneously with the layer (A).
Here, the polyester polymer of the first layer (A) was melt-extruded at a polymer temperature of about 280 ° C. after drying. The second layer (B) was also melt extruded using an extruder at a polymer temperature of about 290 ° C. The film-shaped laminated polymer melt-extruded from the two-layer die was cooled and drawn by a casting roller to obtain an unstretched film. Then, this unstretched film was longitudinally stretched 3.0 times at 130 ° C., and then 135
The film was transversely stretched 3.0 times at 0 ° C. and heat set at 180 ° C. to obtain a laminated biaxially stretched film.

[0081]

[Table 1]

The plane orientation coefficient of the obtained biaxially stretched film was 0.06 for the first layer (A), 0.05 for the second layer (B), the thickness was 6 μm for the first layer (A), and the second layer (B) ) 24 μm.
The heat shrinkage rate of this film at 150 ° C. was 5 to 7%.

The above polyethylene terephthalate and polybutylene terephthalate were both obtained by solid-state polymerization. The former used an intrinsic viscosity of 0.64, used a germanium dioxide catalyst, had a melting point of 255 ° C. and a glass transition temperature of 7
8 ° C., terminal carboxyl group concentration 15 equivalents / 10 ⁶ g, the latter having an intrinsic viscosity of 1.1, using tetrabutyl titanate catalyst, melting point 223 ° C., glass transition temperature 32 ° C., terminal carboxyl group concentration 10 equivalents / 10 ⁶ g. Met.

The evaluation results are shown in Table 2. The biaxially stretched film of the present invention is excellent in extrusion moldability, stretchability, adhesion to a metal plate, low-temperature impact resistance, and fragrance retention (flavor properties). It was.

[0085]

[Table 2]

[Comparative Example 5] In Example 2, the first layer (A) was not laminated and only the second layer (B) was formed (thickness: 3).
However, the fragrance retaining property (flavor property) deteriorated to x.

[Examples 10 to 17 and Comparative Examples 6 to 7] (Production of Polycarbonate) 216 parts of diphenyl carbonate, 228 parts of bisphenol A and 0.05 part of bisphenol A diNa salt were stirred with a stirrer and nitrogen gas. The reaction system was replaced with nitrogen by repeating the procedure of charging in a reaction vessel equipped with a vacuum distillation system having an introduction port and introducing nitrogen gas after vacuum deaeration at room temperature three times. Then, under normal pressure
After heating and reacting at 90 ° C. for 30 minutes, the pressure was gradually reduced at the same temperature to 50 mmHg after 60 minutes. Further, the reaction temperature was raised from 190 ° C. to 290 ° C. over about 60 minutes, and at the same time, the degree of vacuum was changed from 50 mmHg to 1 mmHg or less. As the reaction proceeded, phenol generated by the reaction was distilled off. The reaction was carried out under the same conditions for 40 minutes, and the viscosity average molecular weight (Mv) was 28,000 and the terminal hydroxyl group temperature was
Equivalent / 10 ⁶ g of polycarbonate was obtained. Asahi Denka Kogyo Co., Ltd. as a phosphorus compound in the obtained polycarbonate
ADEKA STAB 2112 was mixed at 45 ppm (phosphorus concentration conversion) and melt-extruded to mix.

(Production of Laminated Film) Polyethylene terephthalate (intrinsic viscosity 0.75, germanium dioxide catalyst used, particle size ratio 1.1, containing 0.2% by weight of titanium dioxide having an average particle size of 0.3 μm) as a solid phase Obtained by the polymerization method. This polyethylene terephthalate had a melting point of 255 ° C. and a glass transition temperature of 78 ° C. (Polymer used for the first layer (A))

On the other hand, the polycarbonate 4 produced above
0% by weight and 60% by weight of polyester composed of polyethylene terephthalate type polyester (70% by weight) and polybutylene terephthalate type polyester (30% by weight) shown in Table 3 were dry blended.

The polyethylene terephthalate type polyester and the polybutylene terephthalate type polyester were both obtained by a solid phase polymerization method, the former using a germanium dioxide catalyst and the latter using a tetrabutyl titanate catalyst, a solid phase polymerization. The IV of the prepolymer and the solid phase polymerization time were changed, and the terminal carboxyl group concentration was changed as shown in Table 3.

[0091]

[Table 3]

The above-mentioned polyethylene terephthalate and polycarbonate / polyester blend polymer were each dried by a conventional method, and these were respectively supplied to two extruders for forming a two-layer coextrusion laminated film. The polyethylene terephthalate had a polymer temperature of 280.
℃, the polymer temperature of the blended polymer is 280-290 ° C
And extruded through a co-extrusion slit. The co-extrusion film was cooled and taken off from the casting drum to produce a laminated unstretched film.

Next, this unstretched film was longitudinally stretched at 135 ° C. to 3.0 times, laterally stretched at 135 ° C. to 3.0 times, and heat-set at 180 ° C. to obtain a biaxially stretched film. .

The polyethylene terephthalate layer of the obtained biaxially stretched film had a thickness of 5 μm and a plane orientation coefficient of 0.0.
7. The thickness of the blend polymer layer was 20 μm, and the plane orientation coefficient was 0.06. The heat shrinkage of this film at 150 ° C. was 5 to 7%.

The evaluation results are shown in Table 4. The terminal carboxyl group concentration of the polyethylene terephthalate polyester is 10 equivalents / 10 ⁶ g or more, and the terminal carboxyl group concentration of the polybutylene terephthalate polyester is 20 equivalents / 10 ⁶ g or less. In the case of, a film excellent in adhesiveness to a metal plate can be obtained, and film forming properties (extrusion moldability,
Stretchability) was also good.

[0096]

[Table 4]

[Examples 18 to 21] 40% by weight of the polycarbonate used in Examples 1 to 9 and 60% by weight of polyester composed of polyethylene terephthalate and 5 mol% of isophthalic acid copolymerized polybutylene terephthalate used in Example 12. In the dry blending, Asahi Denka Kogyo Co., Ltd. ADEKA STAB 2112 was added as the phosphorus compound in the amount shown in Table 5 (phosphorus concentration conversion), and thereafter, a laminated film was produced under the same conditions as in Example 12.

The results are shown in Table 5, and particularly good results were obtained when the addition amount of the phosphorus compound was 20 to 100 ppm.

[0099]

[Table 5]

[0100]

EFFECTS OF THE INVENTION According to the present invention, the impact resistance at a low temperature is excellent, the taste retention (flavor) and the adhesion to a metal plate are good, and the film-forming property (extrusion molding) is excellent. It is possible to provide a biaxially stretched film for metal laminating, which is also excellent in elastic stretchability.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C08L 69/00 LPR C08L 69/00 LPR // B29K 67:00 B29L 9:00 (72) Inventor Yukihiko Minamihira, 3-37-19 Oyama, Sagamihara-shi, Kanagawa Teijin Limited Sagamihara Research Center (72) Inventor Kinji Hasegawa 3-37-19, Oyama Sagamihara-shi, Kanagawa Teijin Limited Sagamihara Research Center

Claims (4)

[Claims] 1. A first layer (A) composed of a polyester having ethylene terephthalate as a main repeating unit, 20 to 60% by weight of a polycarbonate substantially composed of a repeating unit represented by the following general formula (1), and a polyester of 40 to The polyester is composed of 80% by weight, and the polyester has ethylene terephthalate as a main repeating unit and has a terminal carboxyl group concentration of 10 equivalents / 10 ⁶ g.
Polyester 1 containing 10 to 90% by weight of the above polyester and butylene terephthalate as a main repeating unit and having a terminal carboxyl group concentration of 20 equivalents / 10 ⁶ g or less
A biaxially stretched film for metal laminating, characterized by being laminated with a second layer (B) comprising 0 to 90% by weight. Embedded image (Wherein R ¹ and R ² each represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a cycloalkyl group having 5 to 6 carbon atoms in a ring, and R ¹ and R ² represent a carbon atom to which they are bonded. May form a cycloalkyl group having 5 to 6 ring members together with R ³ and R ⁴ each represent an alkyl group having 1 to 5 carbon atoms, a phenyl group or a halogen atom, and m and n each represent 0, 1 or 2) 2. The composition forming the second layer (B) comprises 20 to 20 parts by weight of the composition.
The biaxially stretched film for metal laminate according to claim 1, which contains 100 ppm of a phosphorus compound. 3. The thickness of the entire film is 5 to 100 μm, and the thickness ratio (A / B) between the first layer (A) and the second layer (B).
Is 1/99 to 50/50. The biaxially stretched film for metal laminate according to claim 1. 4. The plane orientation coefficients of the first layer (A) and the second layer (B) are each 0.05 to 0.10.
The biaxially stretched film for metal laminate according to claim 1, 2 or 3, wherein the heat shrinkage rate of the entire film in 10 is 10% or less.