JP2000143841A - Polyester film for lamination with metallic sheet for can cover - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyester film capable of thermocompressively bondable to a metal even at a relatively low temperature and excellent in seamability by selecting a film which is made from a specified amount of a polyester in which terephthalic acid accounts for a specified amount of the total acid component and a specified amount of a polyamide having a specified melting point and has a specified centerline average roughness. SOLUTION: This film is made from a polyester resin composition comprising 97-80 wt.% polyester in which terephthalic acid accounts for at least 80 mol% of the total acid component, and, desirably, 1,4-butanediol accounts for at least 40 mol% of the total glycol component and 3-20 wt.% polyamide, desirably, nylon 12, having a melting point of 150-230 deg.C and has a centerline average roughness of at least 30 nm. Alternatively, the film comprises 70-95 wt.% above polyester resin and 5-30 wt.% polyarylate having a glass transition temperature of at least 150 deg.C. A metallic sheet laminated with this film is one excellent in formability, retorting registance, and feathering resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for laminating a metal plate of a can lid. In detail, the present invention provides a biaxially stretched laminated metal sheet that can be laminated by heat bonding so that the metal sheet is excellent in formability, excellent in tightening properties, and further excellent in retort resistance. And a polyester film for laminating a can lid metal plate.

[0002]

2. Description of the Related Art Metal cans, which are one form of food and beverage packaging containers, are excellent in mechanical strength and airtightness, so that the contents can be stored for a long time. In addition, since the contents are filled at a high temperature and sealed as they are, or sterilization treatment such as retort treatment can be easily performed, the reliability for safety and health as a packaging container is high. In addition, since it has many advantages that contents can be stored in a heated state and that the cans are easily separated and collected after use, in recent years, various types of contents have been filled and used in large quantities. Have been.

Conventionally, a solvent type paint mainly composed of a thermosetting resin has been applied to the inner and outer surfaces of a metal can for food and drink. This paint is used for the purpose of maintaining the flavor of the contents, preventing corrosion of the metal can, improving the aesthetics of the outer surface of the can, protecting the printed surface, and the like.

[0004] However, such a coating can has the following problems. (A) When the contents are filled and sealed, and then subjected to a heating treatment such as a retort treatment, low molecular weight substances such as a residual solvent in the coating film migrate into the contents, and the flavor of the contents is significantly reduced ( Inferior in flavor).

(B) As the diameter of the can lid becomes smaller and the thickness of the can becomes thinner, workability and impact resistance of the coating film are required more than before. On the other hand, the coating film is whitened or coated after retort treatment. Although retort resistance is required for problems such as peeling of the film, it is difficult to obtain a coating film that satisfies these performances.

(C) Use a large amount of an organic solvent. Also,
A large amount of thermal energy is required for drying and baking of the coating film. In recent years, attention has been paid to a metal can (laminate can) manufactured using a film-laminated metal plate obtained by laminating a single-layer or multi-layer plastic film on a metal plate, with respect to a coating can having such a problem. As a film for lamination, especially a polyester film is excellent in mechanical strength, processability, heat resistance, hardly causes pinholes and cracks, hardly impairs the flavor of the contents (excellent in flavor), and relatively It has the advantage of being inexpensive, and has been actively put into practical use.

As a method of laminating a plastic film on a metal plate, a method of providing an adhesive layer in advance on at least one of the plastic film and the metal plate and thermally bonding the same, or a method of laminating a metal plate using a heat-bondable plastic film And the like.

In the former method of providing an adhesive layer, when an adhesive made of a solution in which an uncured thermosetting resin is dissolved in an organic solvent is used, the above-mentioned methods (a) and (c) are used. The problem is not solved, and an interface is formed between the adhesive layer and the film, which causes a problem in workability of the laminated metal plate and impact resistance of the laminated can.

On the other hand, when the latter heat-adhesive film is used, the above problems (a) to (c) are solved and the productivity of metal cans is improved. Specifically, a laminated metal plate obtained by laminating a polyester resin film as a heat-adhesive plastic film on a metal plate has been put to practical use as a material for the body of a three-piece can or a two-piece can. However, at present, application to a lid material constituting a metal can body has not been advanced.

[0010] The main characteristics required of the film laminated on the outer surface of the lid material include:-having an adhesive property to a metal plate;-formability when forming the lid material from the laminated metal plate (pressing and pressing). (Curling processability); ・ In the winding step of winding and closing the lid material and body member, the film should not be damaged when it comes into contact with the winding roll under high load while rotating at high speed (hereinafter referred to as “rolling”). ,
During retort treatment, white powder which is considered to be derived from a low molecular weight material of polyester resin is generated, and water droplets formed by condensation of steam are white spots (water spots). -When a laminated metal plate is applied as an easy-open lid (EOE) material, the film is cut along with the metal plate when the tab is opened, and the film is cut from the metal plate. No peeling of the film, no residue of the film in the cut portion (hereinafter referred to as “feathering property”), and the like.

Hitherto, as laminated films for can lids, JP-A-5-331302 and JP-A-7-13-1 have been used.
Japanese Patent No. 45252 discloses a polyester film in which a water spot during retort hardly occurs. Japanese Patent Publication No. 7-80253 discloses a film suitable for EOE.

[0012] In any case, however, there is no detailed description of the tightness which seems to be the most difficult to solve among the above-mentioned required performances, and the above-mentioned requirements required for the film laminated on the outer surface of the lid member are not described. Techniques for satisfying all of the performances have not been known so far. Therefore, those skilled in the art are strongly demanding the development of a film that can sufficiently withstand a winding process in which severe processing is performed, and a lid member formed by laminating the films.

[0013]

Accordingly, the present invention is capable of being laminated on a metal plate by thermocompression bonding, and satisfies all of the above-mentioned properties required for a film laminated on the outer surface of a lid material. An object of the present invention is to provide a polyester film that is suitable for use in a lid for a laminated can by being excellent in winding property.

[0014]

Means for Solving the Problems The present inventors have found that by containing a certain amount of polyamide in a specific polyester, excellent tightening properties are exhibited and the above-mentioned problems are solved. The present invention has been reached.

That is, the gist of the present invention is as follows. (1) 97-80 wt% of a polyester in which terephthalic acid is 80 mol% or more with respect to all the acid components, and the melting point is 15
Consisting of 3-20 wt% polyamide at 0-230 ° C,
A polyester film for laminating a can lid metal plate, wherein the center line average roughness Ra is 30 nm or more.

(2) Terephthalic acid is 8 relative to all acid components
97-80 wt% of polyester that is 0 mol% or more
And a polyamide having a melting point of 150 to 230 ° C. 3 to 20 wt.
% Of a polyester resin having a glass transition temperature Tg of 150 ° C. or higher, and 5 to 30% by weight of a polyester film for laminating a can lid metal plate.

(3) 1,4-butanediol is 40 mol% based on all glycol components constituting the polyester.
The polyester film according to any one of (1) and (2), characterized in that:

(4) The polyester film according to any one of (1), (2) and (3), wherein the polyamide is nylon 12.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The polyester for producing the film of the present invention is a polyester composed of one type of dicarboxylic acid component and one type of glycol component, or a (copolymerized) polyester composed of two or more types of dicarboxylic acid and / or glycol components, or A blend of two or more polyesters may be used. However, it is necessary that 80 mol% or more of the total acid component is terephthalic acid. When the proportion of the terephthalic acid component is less than 80 mol%, the resulting film is difficult to be oriented and crystallized, and as a result, there arises a problem that the operability particularly in the stretching step is deteriorated.
In addition, a problem that feathering property is inferior occurs.

The copolymerization component is not particularly limited. However, as the acid component, aromatic dicarboxylic acids such as isophthalic acid, (phthalic anhydride), 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, and azelaic acid , Dodecane dicarboxylic acid, (maleic anhydride), maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, etc., aliphatic dicarboxylic acid, (anhydrous) hexahydrophthalic acid, hexahydroterephthalic acid, etc., alicyclic dicarboxylic acid, carbon Hydroxycarboxylic acids such as dimer acid, p-hydroxybenzoic acid, lactic acid, β-hydroxybutyric acid, and ε-caprolactone; and polycarboxylic acids such as trimellitic acid (anhydride), trimesic acid, and pyromellitic acid (anhydride) having several 20 to 60 Functional carboxylic acids can be mentioned.

The alcohol component is not particularly limited. However, 40 mol% or more of the total glycol component is 1,4-
Butanediol is preferred because of its excellent retort resistance. Other copolymerization components include diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, and a molecular weight of 200 to 200. Aliphatic diols such as 2,000 polyethylene glycol, the same polypropylene glycol, and the same polytetramethylene glycol;
Alicyclic diols such as cyclohexanedimethanol and 1,4-cyclohexanediethanol can be exemplified. Aromatic diols such as bisphenol A and bisphenol S ethylene oxide or propylene oxide adducts can also be mentioned. Further, polyfunctional alcohols such as trimethylolpropane, glycerin, pentaerythritol and the like can also be mentioned.

The limiting viscosity of the polyester resin for producing the film of the present invention is preferably 0.45 to 1.5 dl / g. More preferably 0.50 to 0.9
0 dl / g, even more preferably 0.55 to 0.8
0 dl / g. If the intrinsic viscosity is less than 0.45 dl / g, it is difficult to obtain a film having mechanical strength that can be practically used, and if the intrinsic viscosity exceeds 1.5 dl / g, the thermocompression bonding property of the film to a metal plate tends to be impaired. Become.

Known methods can be applied to the production of the polyester. For example, when producing polyethylene terephthalate (PET), terephthalic acid and ethylene glycol and optionally other copolymers are added to an esterification reactor in which bis (β-hydroxyethyl) terephthalate and its low polymer are present. The slurry of the components is continuously supplied and reacted at a temperature of 250 ° C. for about 3 to 8 hours to continuously obtain an esterified product having an esterification reaction rate of about 95%. Next, this was transferred to a polymerization vessel, and 1.3 hP was added in the presence of a catalyst such as germanium dioxide or antimony trioxide.
Melt polymerization may be performed under reduced pressure of a or lower and at a temperature of 250 to 280 ° C. until a polyester resin having a desired intrinsic viscosity is obtained.

Since the polyester after polymerization contains oligomers and acetaldehyde, it is preferable to reduce the content of these by solid-phase polymerization. The solid-state polymerization reaction ends the melt polymerization reaction at a stage where the intrinsic viscosity is lower than the target, and the obtained resin is mass-formed at 180 to 235 ° C.
This is carried out by flowing an inert gas stream so that the atmosphere becomes as described above, or by performing treatment under reduced pressure for 2 to 20 hours.

The film of the present invention contains a polyamide having a melting point of 150 to 230 ° C. in addition to the above polyester. The content ratio is (polyester) / (polyamide) = 97-80 / 3-20 wt%, preferably 95-80%.
It is necessary that the content be 90/5 to 10 wt% in order to obtain excellent crimpability. 3w polyamide content
If it is less than t%, the effect of improving the tightening property is not sufficiently exhibited,
On the other hand, if it exceeds 20% by weight, a production problem occurs, and a film in which both components are uniformly dispersed cannot be obtained.

The polyamide in the present invention is a homopolyamide or a copolyamide obtained from an aminocarboxylic acid, a lactam or a dicarboxylic acid and a diamine. Further, two or more polyamides may be used in combination.

As the monomers forming the polyamide, aminocarboxylic acids include 6-aminocaproic acid, 11
-Aminoundecanoic acid, 12-aminododecanoic acid, p-
Aminomethylbenzoic acid and the like.

As the lactam, ε-caprolactam,
ω-undecanolactam, ω-laurolactam and the like. Examples of dicarboxylic acids include adipic acid, suberic acid, azelaic acid, sebacic acid, dodecane diacid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, 2-
Examples thereof include methyl terephthalic acid, 5-methyl isophthalic acid, 5-sodium sulfoisophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, and diglycolic acid.

As the diamine, tetramethylene diamine, hexamethylene diamine, undecamethylene diamine, dodecamethylene diamine, 2,2,4- / 2,4,4
4-trimethylhexamethylenediamine, metaxylenediamine and the like.

Preferred examples of the polyamide used in the present invention include polycaproamide (nylon 6), polyhexamethylene sebacamide (nylon 610), polyundecamide (nylon 11), polydodecamide (nylon 12) and copolymers thereof. Polyamides. Among them, nylon 12 is particularly preferred in that it has excellent tightness.

The polyamide of the present invention preferably has a relative viscosity ηr of from 1.3 to 5.0, particularly from 1.5 to 5.0, in order to obtain good film properties by mixing with the polyester.
It is preferably 3.0.

The polyamide used in the present invention has a melting point of 1
Must be 50-230 ° C, 170-230 ° C
Is preferably within the range. When the melting point exceeds 230 ° C., the thermocompression bonding property to a metal plate and the formability are inferior, and the sealing property is not sufficient. On the other hand, when the melting point is less than 150 ° C., the moldability into a film is poor, and not only a uniform film is hardly obtained, but also the dimensional stability is poor, so that the workability at the time of thermocompression bonding to a metal plate is deteriorated. .

A known method is suitable for producing the polyamide.
Can be used. For example, when manufacturing nylon 6
Contains 100 parts by weight of ε-caprolactam and 10 parts by weight of water.
Into a reaction vessel and heat while stirring, 3 to 10 kg
/ Cm^TwoIncrease pressure until. And gradually steam
While releasing pressure, pressure 3 to 10 g / cm ^Two, Temperature 260 ~
After polymerization at 280 ° C for 2 hours, normal pressure for 1 hour
Release pressure to Then, at a temperature of 260-280 ° C and normal pressure
React until a polyamide of the desired relative viscosity is obtained.
Perform polymerization.

In the film of the present invention, in addition to the polyester resin comprising the above-mentioned polyester and polyamide,
It is a preferred embodiment to further contain a polyarylate. The polyarylate refers to an aromatic resin composed of an aromatic dicarboxylic acid and a derivative thereof and a divalent phenol and a derivative thereof. This polyarylate is a high molecular weight substance via an ester bond, but is generally distinguished from a so-called polyester because it generally has a very high glass transition temperature.

In the present invention, the glass transition temperature Tg is 150
C. or higher polyarylate (polyester resin described above) / (polyarylate) = 70-95 / 5-30 wt.
% Is preferable in order to increase the adhesion to metal while maintaining good feathering properties. When the glass transition temperature of the polyarylate is less than 150 ° C., the feathering property is poor. On the other hand, if the content is less than 5%, the effect of adding polyarylate is not recognized.
If the content exceeds wt%, the crystallinity of the mixed resin decreases, and the feathering property decreases.

The aromatic dicarboxylic acid component constituting the polyarylate includes terephthalic acid, isophthalic acid, phthalic acid, biphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid,
Tert-butyl isophthalic acid can be exemplified.

Examples of the divalent phenol component include hydroquinone, resorcinol, bis (4-hydroxyphenyl) methane, bis (4-hydroxyphenyl) ether, bis (4-hydroxyphenyl) sulfide, and bis (4-hydroxyphenyl) sulfoxide. , Screw (4-
Hydroxyphenyl) ketone, bis (4-hydroxyphenyl) diphenylmethane, bis (4-hydroxyphenyl) -p-diisopropylbenzene, bis (3,5-
Dimethyl-4-hydroxyphenyl) methane, bis (3
-Methyl-4-hydroxyphenyl) methane, bis (3,5-dimethyl-4-hydroxyphenyl) ether, bis (3,5-dimethyl-4-hydroxyphenyl) sulfone, bis (3,5-dimethyl-4- Hydroxyphenyl) sulfide, 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (3,5-dimethyl-4-hydroxyphenyl) ethane, 1,1-bis (4
-Hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane,
2,2-bis (4-hydroxyphenyl) propane,
2,2-bis (4-hydroxyphenyl) butane, 2,
2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, 2,2-bis (3-methyl-4-hydroxyphenyl) propane, 2,2-bis (chloro-4-
Hydroxyphenyl) propane, 2,2-bis (3,5
-Dichloro-4-hydroxyphenyl) propane, 2,
2-bis (3-bromo-4-hydroxyphenyl) propane, 2,2-bis (3,5-dibromo-4-hydroxyphenylpropane, 1,1,1,3,3,3-hexafluoro-2- Bis (4-hydroxyphenyl) propane, 4,4′-dihydroxybiphenyl, 3,3 ′,
5,5'-tetramethyl-4,4'dihydroxybiphenyl, 4,4'-dihydroxybenzophenone and the like can be mentioned.

In the present invention, in particular, (terephthalic acid) /
(Isophthalic acid) = 20-80 / 80-20mol%
And 2,2-bis (4-hydroxyphenyl) propane (Bis-A) are preferred because of their excellent compatibility with polyester.

As a method for producing polyarylate, a known method can be applied. For example, in the interfacial polymerization method, a divalent phenol compound in the presence of a polymerization catalyst,
Alternatively, the acid halide of the aromatic dicarboxylic acid dissolved in a solvent that is inert to the reaction and dissolves the resin to be formed is mixed with an aqueous alkali solution in which a divalent phenol compound is dissolved, and the mixture is mixed at 2 to 50 ° C. By reacting for 0.5 to 5 hours, polyarylate can be obtained.

The polyester film of the present invention can be easily and stably produced by melt-extruding a resin in which polyester and polyamide are mixed so as to satisfy the above constitution (blend method). When a polyarylate is contained, it is preferable to melt-mix the polyester and the polyarylate before blending with the polyamide, from the viewpoint of increasing compatibility.

More specifically, the mixture is melted and mixed by the above-described method, discharged from a die, formed into a film, and subjected to biaxial stretching and heat setting. That is, it can be manufactured by a known method such as a flat type or tubular type film forming method, but a flat type is preferable in order to manufacture a film with less thickness unevenness. As the stretching method, a simultaneous stretching method or a two-stage biaxial stretching method can be used successively.

Hereinafter, as a more detailed example, a case where the polyester film of the present invention is produced by a flat biaxial stretching method will be described. For example, polyester and polyamide blended to have a target composition are
It is melt-mixed using an extruder equipped with a die, extruded into a sheet from a T-die, and brought into close contact with a casting roll whose temperature is controlled to a glass transition point of Tg (Tg-10) ° C. or lower, and quenched. Then, an unstretched sheet having a desired thickness is obtained. At this time, in order to sufficiently melt and mix the resin composition of the raw material, a raw material that has been previously melt-kneaded may be used. The degree of kneading of the resin composition is determined by the screw shape of the extruder, the extrusion temperature, the residence time of the resin, and the like.

Next, both ends of the unstretched sheet are gripped with clips, and preheated by blowing hot air at a temperature of 40 to 120 ° C. from the upper and lower surfaces of the sheet. It is biaxially stretched about 2 to 4 times.

Thereafter, the film is heat-set at 100 to 200 ° C. for several seconds to several tens of seconds, with the relaxation rate in the vertical and / or horizontal direction being several percent, to heat set the film. And cool to room temperature,
The film is wound at a speed of 20 to 500 m / min to obtain a film having a desired thickness.

As a heat treatment method after stretching, a conventionally known method can be employed. For example, a method of blowing hot air to the stretched film, a method of irradiating the stretched film with infrared rays, a method of irradiating the stretched film with microwaves, and the like can be mentioned. Is preferred.

As disclosed in JP-B-35-11774 and JP-B-43-5557, etc.
A heat buffer zone may be provided between the stretching step and the heat setting step.

The film of the present invention has an average particle diameter of one or more selected from inorganic lubricants such as silica, alumina, kaolin, calcium carbonate, titanium dioxide, barium sulfate and the like, or organic lubricants such as silicone particles. 2.
A required amount of a lubricant of 5 μm or less may be added. This makes it possible to impart slip properties to the film surface, thereby improving the processability during film production or thermocompression bonding with a metal plate.

Further, the film may contain a coloring agent, an antioxidant, an antistatic agent, an antifoaming agent, a flame retardant and the like.

The center line average roughness Ra of the film thus obtained must be 30 nm or more. If Ra is less than 30 nm, the desired crimping property cannot be obtained because the slip property of the film surface is reduced.

The film of the present invention has a thickness of 5 to 50 μm.
It is preferred that More preferably, 8 to 25 μm,
More preferably, it is 10 to 20 μm. 5μ thickness
If it is less than m, breakage or the like is likely to occur at the time of processing, and if it exceeds 50 μm, the winding property will be deteriorated.

Further, the film of the present invention may be provided with an adhesive layer by coextrusion, lamination or coating in order to improve the adhesion to the metal plate. The thickness of the adhesive layer is preferably 0.5 μm or less in terms of a dry film thickness.

As a method of laminating the polyester film and the metal plate of the present invention, the metal plate is preheated to a predetermined temperature in advance, and this and the film are pressed against each other by a temperature-controllable roll and thermocompressed. A method of cooling is used. By doing so, a laminated metal plate can be manufactured continuously.

Examples of the method for heating the metal plate include a heater roll heat transfer system, an induction heating system, a resistance heating system, and a hot air transfer system. The system is preferred. As a cooling method after lamination, a method of dipping in a coolant such as water or a method of contacting with a cooling roll can be used.

The conditions for lamination are not particularly limited, but excessive amorphization of the film during the lamination step should be avoided. This is because the non-crystallized part is partially crystallized during the retort treatment, thereby generating a water spot or deteriorating the feathering property.

Preferred lamination conditions are [Tm-50 ° C.] to [Tm-10 ° C.] with respect to the melting point Tm of the polyester which is a main component of the film. Tm1, Tm2 on high temperature side
Room temperature to [Tm-100 ° C] or [Tm1 to 50 ° C] to [Tm2 to 10 ° C].
m1-100 ° C.] with a linear pressure of 5
For example, a method in which a film is pressed at 100 kg / cm to perform thermocompression bonding and then rapidly cooled in cold water can be exemplified.

As the metal plate for lamination, a sheet-shaped or band-shaped steel plate or an aluminum plate, or those obtained by subjecting their surfaces to various plating treatments or chemical conversion treatments are preferable. Particularly, those having a chromium hydrated oxide film on the surface layer or those having a two-layer structure of metal chromium on the lower layer and chromium hydrated oxide on the upper layer have an adhesive property with the polyester film of the present invention. Excellent.

Further, the surface of the steel sheet is subjected to one or more multi-layer plating or alloy plating of tin, nickel, zinc, aluminum or the like, and a chromium hydrated oxide film or a film having the above-mentioned two-layer structure is formed thereon. Can be used. Specifically, tinplate, tin-free steel (TFS), nickel-plated steel sheet, ultra-thin tin-plated steel sheet (LTS) and the like can be used.

As the aluminum plate, pure aluminum, an Al—Mn alloy, an Al—Mg alloy, which has been subjected to a chromate treatment, a phosphate treatment, an anodizing treatment, a boehmite treatment, or the like, or a chromium A hydrated oxide film or a film formed with a film having the above-mentioned two-layer structure can be used.

[0059]

Next, the present invention will be described more specifically with reference to examples. The analysis method and measurement method of each characteristic value used in the following Examples and Comparative Examples are as follows.

Resin composition: Methanol was decomposed in a sealed tube at 230 ° C. for 3 hours, then subjected to gas chromatogram analysis, and quantitatively analyzed.

Intrinsic viscosity [η] of polyester resin: Measured at a temperature of 20 ° C. using an equal weight mixed solvent of phenol / 1,1,2,2-tetrachloroethane. The unit is dl
/ G.

Relative viscosity [ηr] of polyamide resin: 9
8% sulfuric acid as solvent, temperature 25 ° C, concentration 1g / d
1 was measured.

Center line average roughness [Ra] of the film: Using a stylus type surface roughness meter (ET-30K) manufactured by Kosaka Laboratories, a stylus radius of 0.5 μm according to JIS B0601.
m and the contact pressure were 0.02 g.

Thermal properties of the film: Using a differential scanning calorimeter (DSC-7) manufactured by Perkin Elmer, 10 to 12 mg of the stretched film was heated at a rate of 20 ° C./min from 25 ° C. to 280 ° C. The temperature was elevated and measured.

The melting point Tm was determined from the temperature at the peak top of the melting peak. For example, Japanese Patent Application Laid-Open No. 4-117427
In the case where a sub-peak derived from a heat-setting treatment performed during the production of a film, as described in Japanese Patent Application Laid-Open No. H10-163, etc., was observed, the measurement was performed by excluding this.

Lamination property: The condition after lamination was visually evaluated according to the following criteria. ：: The film laminated with metal has no defects such as scratches and wrinkles, and the part which is well thermocompressed is 98% of the entire area.
that's all.

Δ: The above portion is 80% or more and less than 98% of the entire area. ×: The above portion is less than 80% of the entire area.

Adhesion: A strip-shaped test piece having a width of 18 mm was cut out from the laminated metal plate having the above-mentioned lamination property judged to be ○ or △. The film was not laminated on the end of the metal plate, and the length of the laminated portion was set to 8 cm or more. Then, using an autograph manufactured by Shimadzu Corporation, 10 m per film
A 180 ° peel test was performed at a speed of m / min, and the peel strength of 11 test pieces was measured and evaluated according to the following criteria.

：: Peel strength of 10 or more test specimens out of 11 specimens was 30
The film was broken at 0 gf or more or 300 gf or more. Δ: Peeling strength of 5 to 9 test pieces is 300 gf or more,
The film was broken at 300 gf or more.

X: Four or less test pieces having a peel strength or breaking strength of 300 gf or more when the film is broken.

Moldability: Press machine (manufactured by Onuma Iron Works, N
FL-25) and a curling machine (manufactured by Tokyodo Kikai Co., Ltd.), 100 pieces of 202-diameter lid material were formed from the laminated metal plate, and at that time, the presence or absence of damage such as peeling, cutting, and cracking of the film was visually checked. And observed with a fluorescence microscope (magnification: 80) and evaluated according to the following criteria.

：: 95 or more of the 100 lids were not damaged. Δ: Out of 100 lid materials, 80 to 94 were not damaged. ×: Some damage is observed in 21 or more of the 100 lid materials.

Crimping property: After a resin lining (PVC sol) is applied to the inner surface of the lid material obtained as described above, a commercially available 190 g 3P can is formed using a wrapping machine (manufactured by Chujo Can Co., Ltd., semi-automatic seamer). (Welded can) was wound around the lid material.

In the winding step, since the film is not scratched even by delicate differences in conditions, 100 pieces of lids made under each condition are prepared, and they are arranged at random. Continuous tightening was performed, and the occurrence of damage was visually observed and evaluated according to the following criteria.

：: 95 or more of the 100 lids were not damaged. Δ: Out of 100 lids, 80 to 94 were not damaged. ×: Some damage is observed in 21 or more of the 100 lid materials.

Feathering property: Aluminum plate (50
52H34 material) from a laminated metal plate using a stainless steel tab (SOT) type easy-open lid (E
OE) were prepared for each 100 pieces.

Then, ten persons were asked to open 10 plugs each, and the cut surfaces were visually observed and evaluated according to the following criteria. ：: Abnormality such as peeling of the film or whiskers was not observed in 95 or more out of 100 EOEs.

Δ: Abnormality such as peeling of the film or whiskers was not observed in 80 to 94 out of 100 EOEs. ×: Abnormalities such as peeling of the film and whiskers were observed in 21 or more out of 100 EOEs.

Retort resistance: The lid material obtained as described above was autoclaved (BS32, manufactured by Tommy Seiko Co., Ltd.).
5) and subjected to retort treatment in steam at 125 ° C. for 30 minutes. Thereafter, the appearance of water spots and white powder on the appearance of the film was visually observed and used as an index of retort resistance according to the following criteria.

○: good. Δ: Water spot or white powder was observed in less than 5% of the film surface area. ×: Water spots or white powder were observed in 5% or more of the film surface area.

Further, polyester (A) and polyarylate (B) used in the following Examples and Comparative Examples, a melt-mixed resin (C) of these polyester (A) and polyarylate (B), polyamide (D) The details are as follows.

Polyester (A) (A-1): PET formed by 100 mol% of terephthalic acid (TPA) and having intrinsic viscosity η of 0.71 and subjected to solid-state polymerization. Melting point Tm is 254 ° C.

(A-2): Isophthalic acid (IPA)
Copolymerized PET which has been subjected to solid-phase polymerization and has a limiting viscosity η of 0.78 by copolymerization with 0 mol%. Tm is 230 ° C. (A-3): a copolymerized PET having an intrinsic viscosity η of 0.82 obtained by copolymerizing 17 mol% of IPA.

(A-4): Copolymerized PET having an intrinsic viscosity η of 0.80 obtained by copolymerizing 22 mol% of IPA. (A-5): PBT having an intrinsic viscosity η of 1.12. Tm is 222 ° C.

Each of the resins A-1 to A-5 contained 0.01 wt% of silica having an average particle size of 1.0 μm.

Polyarylate (B) (B): Terephthalic acid (TPA) / isophthalic acid (IP
A) is obtained by interfacial polymerization of acid chloride having an equimolar ratio with 2,2-bis (4-hydroxyphenyl) propane (Bis-A), and has an intrinsic viscosity [η] of 0.62.
Polyarylate. Glass transition temperature Tg is 194 ° C.

Melt-mixed resin (C) (C-1): A resin obtained by dry-blending polyester A-1 and polyarylate B at 40/60 wt% and melt-mixing at 300 ° C. No Tm was found in the obtained molten mixed resin, and Tg was 125 ° C.

(C-2): Polyester A-2 and polyarylate B are dry-blended at 60/40 wt%.
Resin melt mixed at 290 ° C. Tm of the obtained molten mixed resin was 206 ° C., and Tg was 108 ° C.

Polyamide (D) (D-1): Nylon 6 having a relative viscosity ηr of 1.8. Tm
Is 220 ° C. (D-2): Nylon 6 having a relative viscosity ηr of 2.5. Tm
Is 222 ° C.

(D-3): Nylon 12 having a relative viscosity ηr of 1.9. T
m is 178 ° C. (D-4): Nylon 12 having a relative viscosity ηr of 1.8. T
m is 178 ° C. (D-5): Nylon 66 having a relative viscosity ηr of 1.7. T
m is 259 ° C.

Table 1 shows a list of the polyesters (A), polyarylates (B) and polyamides (D).

[0092]

[Table 1]

(Example 1) 90% by weight of a sufficiently dried polyester resin A-2 and 10% by weight of a polyamide D-1
t%, and an extruder (7
It was extruded into a sheet at a temperature of 260 ° C. and a discharge rate of 500 g / min using a gentle compression type single screw having a diameter of 5 mm and L / D = 45. Subsequently, this was brought into close contact with a casting roll adjusted to a surface temperature of 10 ° C. and rapidly cooled to obtain an unstretched sheet having a thickness of 120 μm.

The end of the unstretched sheet was gripped by clips of a tenter-type stretching machine, and after traveling in a preheating zone of 80 ° C., stretched three times in the machine direction (MD) at a temperature of 85 ° C. After running through the preheating zone of 95 ° C,
It was simultaneously biaxially stretched 3.5 times in the transverse direction (TD) at 0 ° C.

Next, the relaxation rate of TD was set to 5%,
And then cooled to room temperature.
The film was wound at a speed of / min to obtain a film having a thickness of 12 µm.

The obtained film was slit and the width was 20c.
m was obtained.

Next, a laminated metal plate was manufactured using this film. That is, the board thickness is 0.19 mm and the board width is 2
A 2 cm roll of tin-free steel (TFS, temper degree T-4) is heated to 208 ° C. by an induction heating roll, and the film is coated on both sides with a surface temperature of 50 ° C.
Using a pair of silicone rolls adjusted to ° C, lamination was performed under the conditions of a nip length of 20 mm and a line speed of 20 m / min. Lamination time was 0.06 seconds. After 3 seconds, the laminate was immersed in ice water and cooled to obtain a laminated metal plate. A can lid material was manufactured using the laminated metal plate.

Table 2 shows the properties of the obtained film, various evaluation results using the laminated metal plate, and various evaluation results when a can lid material was manufactured using the laminated metal plate.
Shown in

The evaluation of the feathering property of the easy-open lid (EOE) was performed using a sample obtained by laminating a film on an aluminum plate. That is, commercially available rolled aluminum (5052H34, 0.26 mm
This was heated with a heater roll. Otherwise, the film was laminated by the same operation as described above.

[0100]

[Table 2]

(Example 2) In the stretching treatment, after running in a preheating zone at 80 ° C, the MD was tripled at 90 ° C,
It was simultaneously biaxially stretched 3.3 times in TD. Then, a film and a laminated metal plate were obtained under the same conditions as in Example 1 except for the above.

Table 2 shows the properties of the obtained film, various evaluation results using the laminated metal plate, and various evaluation results when a can lid material was manufactured using the laminated metal plate.
Shown in

(Examples 3 to 7 and Comparative Examples 1 to 5) As shown in Tables 2 and 3, the types of the polyester resin and the polyamide resin, the compounding ratio thereof, and the film production conditions were changed, and the simultaneous biaxial A film was produced by a stretching method.

Using the obtained film, a laminated metal plate was experimentally produced under the same conditions as in Example 1, and its performance was evaluated. Tables 2 and 3 show the obtained results.

[0105]

[Table 3]

As shown in Tables 2 and 3, Examples 1 to 7
In, all of the various performances were satisfactory. In particular, those of Examples 6 and 7 contained polyarylate, so that the adhesiveness to the metal plate was good while maintaining good feathering properties. In Example 1,
In the evaluation of retort resistance in 2, 3, and 7, white powder was observed in less than 5% of the film surface area.
Which was based on the low molecular weight material in the resin.

In Comparative Example 1, the melting point of polyamide D-5 was 2
Since it was 59 ° C., which was higher than 230 ° C. which is the upper limit of the range of the present invention, the adhesiveness and moldability of the laminated metal plate were poor. In addition, since the can lid was damaged after molding and a good one was not obtained, the evaluation after the tightening property in Table 1 was not performed.

In Comparative Example 2, the center line average roughness R of the film was
Since a was 25 nm, which was below the lower limit of 30 nm of the range of the present invention, the crimpability was poor. Feathering and retort resistance were also poor.

In Comparative Example 3, the content of terephthalic acid in polyester A-4 was 77.3 wt% (77.3 m
ol%), which is lower than the lower limit of 80 mol% of the range of the present invention, so that the feathering property was poor. It was also inferior in winding and retort resistance.

In Comparative Example 4, the blending ratio of polyester / polyamide was 99/1, out of the range of the present invention in the direction of decreasing the amount of polyamide, and the center line average roughness Ra of the film was 16 nm. 30 which is the lower limit of the range
nm, it was inferior in the tightening property.

Comparative Example 5 shows that 1,4-butanediol contains 4
Although it was contained in an amount of 0 mol% or more and had excellent retort resistance, the center line average roughness Ra of the film was 22 nm,
Since it was less than the lower limit of 30 nm of the range of the present invention, it was inferior in the tightening property.

Comparative Example 6 75% by weight of a dried polyester resin (A-1 / A-5 = 40/60% by weight)
And 25% by weight of polyamide D-3 were blended, and extrusion was performed at 260 ° C. in the same manner as in Example 1.
However, since the blending ratio of the polyamide was higher than the range of the present invention, bals occurred immediately after the extrusion port, and a uniform unstretched film could not be obtained.

Therefore, the extrusion temperature was increased to 270 ° C., but the situation was not improved.

[0114]

According to the present invention, polyesters 97 to 8 in which terephthalic acid is at least 80 mol% based on the total acid components.
0% by weight and polyamide 3 ~ with melting point of 150 ~ 230 ° C
Since it is made to be 20 wt%, it has excellent mechanical properties and heat resistance, and can be thermocompression bonded to metal at a relatively low temperature.
The laminated metal plate obtained by the heat pressure welding has excellent moldability and retort resistance, and has a synergistic effect with that the center line average roughness Ra is 30 nm or more. A polyester film can exhibit many advantages such as excellent winding and feathering properties, which have not been able to satisfy the required properties.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C08L 77/00 C08L 77/00 // B32B 27/36 B32B 27/36 (72) Inventor Masanobu Hioki Uji, Kyoto 23, Kozakura Unitika Central Research Laboratories F-term (reference) CF181 CL012 CL032 FD170 GH02

Claims (4)

[Claims] 1. The terephthalic acid content is 80 m with respect to all acid components.
ol% or more of 97 to 80% by weight of a polyester having a melting point of 150 to 230 ° C and 3 to 20% by weight of a polyamide having a center line average roughness Ra of 30 nm or more. Polyester film. 2. Terephthalic acid is 80 m based on all acid components.
ol% or more of a polyester resin consisting of 97 to 80 wt% of a polyester having a melting point of 150 to 230 ° C and a polyamide resin of 3 to 20 wt%, and a polyarylate having a glass transition temperature Tg of 150 ° C or more. A polyester film for can lid metal plate lamination, comprising 5 to 30 wt%. 3. The polyester film for a can lid metal plate according to claim 1, wherein 1,4-butanediol is at least 40 mol% based on all glycol components constituting the polyester. 4. The polyester film according to claim 1, wherein the polyamide is nylon 12.