JPH0985917A - Metal sheet coating film, coated metal sheet, and thier manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a metal sheet by thermally laminating a polyester resin film on the metal sheet by high adhesion. SOLUTION: An amorphous saturated polyester resin layer under 20% crystallinity) is laminated on at least one side surface of a crystalline saturated polyester resin layer (at least 20% crystallinity). When a melting point of the crystalline resin is Tmc, the amorphous resin layer is thermally laminated on the metal sheet heated at (Tmc-120) deg.C-(Tmc+100) deg.C to obtain a coated metal sheet. the crystalline resin layer can be composed of polybutylene terephthalate resin, and the amorphous resin layer can be formed of a polyester resin wherein at least 70mol% of glycol constituent is 1,4-butanediol. The crystalline resin layer and the amorphous resin layer may be a nonorientable resin layer, and may contain polycarbonate. Thermal laminating can be carried out at a comparatively low temperature by this method, and even after laminating, the crystalline resin layer maintains high crystallinity.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyester resin film useful for coating the surface of a metal plate, a coated metal plate coated with this polyester resin film, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a metal plate laminated with a thermoplastic film has been used as a material for electric appliances, furniture, storage cases, interior / exterior building materials, household products, containers, cans and the like. The coated metal plate, for example, an adhesive is applied to the surface of the metal plate using a roll coater or the like, after evaporating volatile components such as a solvent of the adhesive, a thermoplastic resin film is laminated and cooled, It is manufactured by a method of heating and then aging if necessary, followed by cooling, and a method of laminating a thermobondable thermoplastic resin film in which a polar group is introduced into a thermoplastic resin in advance on a metal plate.

Regarding the coated metal sheet, for example, a coated steel sheet obtained by laminating a polyvinyl chloride film on a steel sheet using an adhesive, a coated steel sheet obtained by laminating a polyolefin resin film on a metal sheet (JP-A-53-141786),
A coated metal plate (Japanese Patent Publication No. 57-23584) in which a copolymerized polyester resin film is laminated on a metal plate has been proposed. However, a steel sheet laminated with polyvinyl chloride has low heat resistance and surface scratch resistance, and a polyolefin-coated steel sheet has poor heat resistance, corrosion resistance, and surface hardness. Further, the steel sheet coated with the copolyester resin is high in cost and poor in practicality.

JP-A-58-39448, JP-B-6
3-13829 discloses a method of laminating a polyester film on a metal plate using an adhesive. In this method, the adhesive is applied to the surface of the metal plate,
A method of heating in a long oven (150 to 200 ° C.) to evaporate volatile components such as a solvent, followed by laminating a polyester resin film and immediately cooling, or a method of further heating and aging for cooling after that is adopted. There is. However, such a method requires a long oven, is disadvantageous in terms of equipment and economy, and the capacity of the oven greatly affects the production rate. for that reason,
There is a limit to increasing productivity.

JP-B-49-34180 proposes a method of laminating a polyester film (crystalline stretched polyethylene terephthalate film) as an adhesive on a metal plate, and JP-B-60-47103 discloses a polyester film. A method of thermally laminating (crystalline stretched polyethylene terephthalate film) on a metal plate has been proposed. However, in the method of heat-bonding the crystalline stretched polyethylene terephthalate film to the metal plate, the heat-bonding conditions are limited to a narrow range, and 280 to 300
Sufficient adhesion with a metal plate cannot be obtained unless it is heated to a high temperature of about ℃. Furthermore, the crystallinity is almost destroyed by the heat at the time of heat bonding, and the crystalline stretched polyethylene terephthalate film is converted into an amorphous polyester resin film. Therefore, the permeability of moisture, gas, and various ions increases, and the characteristics of the coating film do not manifest effectively, and the protective effect on the metal plate tends to decrease. For example, bending workability and drawing workability deteriorate, and when an Erichsen test is performed, film peeling and film cracking phenomena occur. Therefore, the characteristics of the crystalline stretched polyethylene terephthalate film cannot be effectively utilized, and the significance of using the film is lost. This also applies when a biaxially stretched polyethylene terephthalate film is used.

[0006]

Therefore, an object of the present invention is to maintain a high crystallinity even after laminating and to have a high surface protection property, which is useful for protecting a metal plate. To provide. Another object of the present invention is to provide a polyester resin film for covering a metal plate, which can be heat-laminated with high adhesion to a metal plate without using an adhesive and has little thermal deterioration. Still another object of the present invention is to provide a coated metal plate coated with a film having the above-mentioned excellent properties, and a method capable of producing such a coated metal plate by thermal lamination at a relatively low temperature. is there.

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have laminated an amorphous resin layer on a crystalline resin layer, and heat the amorphous resin layer on a metal plate. When bonded, not only the adhesion with the metal plate but also the surface protection is great,
The inventors have found that the crystalline resin layer can effectively protect the metal plate and completed the present invention.

That is, in the film for coating a metal plate of the present invention, an amorphous saturated polyester resin layer for thermal lamination to a metal plate is laminated on at least one surface of the crystalline saturated polyester resin layer. The crystallinity of the crystalline saturated polyester resin layer may be 20% or more, and the crystallinity of the amorphous polyester resin layer is 20%.
It is often less than%. The crystalline saturated polyester resin layer may be composed of a polybutylene terephthalate resin containing a butylene terephthalate skeleton composed of terephthalic acid and 1,4-butanediol in an amount of 70 mol% or more, and the amorphous saturated polyester resin layer may include a glycol component. It can be composed of an amorphous saturated polyester in which 70 mol% or more is 1,4-butanediol. Each of the resin layers may be a non-stretched resin layer. Furthermore, the melting point of the crystalline saturated polyester resin is Tmc, and the melting point of the amorphous saturated polyester resin is Tmc.
Assuming ma, the melting points Tmc and Tma are 80 ° C <Tma <
In many cases, the relational expression of (Tmc-5) ° C is satisfied. The crystalline saturated polyester resin layer and / or the amorphous saturated polyester resin layer may contain polycarbonate.

In the coated metal plate of the present invention, a crystalline saturated polyester resin layer is laminated on at least one surface of the metal plate via an amorphous saturated polyester resin layer.
Such a coated metal plate is a method of thermally laminating a crystalline saturated polyester resin layer on at least one surface of the metal plate, and when the melting point of the crystalline saturated polyester resin is Tmc, (Tmc-120 ) ° C ~ (Tmc + 10
It can be manufactured by laminating a crystalline saturated polyester resin layer on the surface of the metal plate heated to 0) ° C. via an amorphous saturated polyester resin layer.

In the present specification, the melting point (Tm) of the polyester resin is the peak temperature corresponding to the melting endothermic peak when measured with a differential scanning calorimeter (DSC) at a heating rate of 10 ° C./min. means. Further, as described above, the melting point of the saturated crystalline polyester resin is Tmc, and the melting point of the saturated amorphous polyester resin is Tma.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The saturated polyester resin used in the present invention is obtained from a saturated polyvalent carboxylic acid or its acid anhydride or a corresponding lower alkyl ester (for example, methyl ester), and a saturated polyhydric alcohol. Examples of the saturated polycarboxylic acid include phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, diphenyldicarboxylic acid, trimetic anhydride, 2,6-naphthalenedicarboxylic acid, di (p-carboxyphenyl) ethane and di ( p-
Carboxyphenyl) ether, bis (4-carboxyphenyl) ketone, aromatic polycarboxylic acid such as 5-sodium sulfoisophthalic acid, succinic acid, glutaric acid,
Examples thereof include aliphatic polycarboxylic acids such as adipic acid, pimelic acid, suberic acid, sebacic acid, azelaic acid and dodecadioic acid, and alicyclic polycarboxylic acids such as 1,4-cyclohexanedicarboxylic acid. These saturated polycarboxylic acid components may be used either individually or in combination of two or more. Among these polyvalent carboxylic acid components, aromatic dicarboxylic acid,
In particular, an aromatic dicarboxylic acid component containing at least terephthalic acid is often used.

Examples of the saturated polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,3-butanediol and 1,4-butane. Aliphatic diols such as diols, polytetramethylene glycol, 1,5-pentanediol, 1,6-hexanediol and neopentyl glycol, aliphatic polyols such as trimethylolpropane and pentaerythritol, cyclohexanediol, 1,4-cyclohexane Alicyclic diols such as dimethal, aromatic diols such as bisphenol A, alkylene oxides of bisphenol A (eg, ethylene oxide adducts) And the like. These saturated polyhydric alcohols can be used alone or in combination of two or more. Of these polyhydric alcohol components, a diol component is often used. The preferred saturated polyhydric alcohol component is linear C
_2-6 Aliphatic diols (eg ethylene glycol, diethylene glycol, triethylene glycol, 1,4
-Butanediol, etc.), alicyclic diols (eg,
1,4-dimethylolcyclohexane etc.) and the like. A particularly preferred polyhydric alcohol component contains at least ethylene glycol and / or 1,4-butanediol. Incidentally, instead of the polyvalent carboxylic acid component and the polyhydric alcohol component, p-oxybenzoic acid, p-
An oxycarboxylic acid component such as β-ethoxybenzoic acid may be used.

The saturated polyester resin is preferably an aromatic polyester resin containing at least an aromatic polycarboxylic acid component rather than an aliphatic polyester resin in which the polycarboxylic acid is an aliphatic polycarboxylic acid. In many cases, the aromatic polycarboxylic acid component contains at least terephthalic acid as a main component. The weight average molecular weight of the saturated polyester resin is, for example, 1 × 10 ^{4 to} 100 × 10.
⁴ , preferably in the range of about 2 × 10 ⁴ to 50 × 10 ⁴ .

In the present invention, among these saturated polyester resins, a crystalline saturated polyester resin (hereinafter sometimes referred to simply as a crystalline polyester resin or a crystalline resin) and an amorphous (amorphous) saturated polyester resin (hereinafter ,
(Sometimes referred to as amorphous polyester resin or amorphous resin). That is, the metal plate coating film of the present invention, on at least one surface of the crystalline saturated polyester resin layer, an amorphous saturated polyester resin layer is laminated, the amorphous saturated polyester resin layer, a metal plate and Used for thermal lamination. In addition,
Japanese Unexamined Patent Publication (Kokai) No. 3-124443 discloses a film in which a polyethylene terephthalate layer and a heat seal layer formed of a polybutylene terephthalate copolymer having a melting point of 140 to 215 ° C. are laminated. However, this film is used as a packaging material for heat treatment and retort treatment.

Crystalline Saturated Polyester Resin Layer The crystallinity of the polyester resin constituting the crystalline saturated polyester resin layer can be measured by a wide-angle X-ray diffraction method, for example, 20% or more (for example, 23 to 60%). Degree), preferably 25% or more (for example, about 25 to 55%), more preferably 30% or more (for example, 30 to 5).
0%). The crystallinity is determined by the type of saturated polyester resin, film molding method (for example, T-die method, inflation method, stretch molding method, heat setting method, etc.).
In addition, it can be adjusted by adding a crystal nucleus growth agent, aging and the like.

The crystalline saturated polyester resin contains a saturated polyester of a dicarboxylic acid containing terephthalic acid as a main component and a diol component containing alkylene glycol as a main component, and contains 70 mol% of alkylene terephthalate units.
Or more (preferably 75 to 100 mol% or more, more preferably about 80 to 100 mol). That is,
The amount of terephthalic acid used is 7
It is 0 mol% or more (preferably 75 to 100 mol, more preferably about 80 to 100 mol), and terephthalic acid is often used alone. When terephthalic acid is combined with another dicarboxylic acid, terephthalic acid is often used in combination with an aromatic dicarboxylic acid (eg, isophthalic acid, naphthalene dicarboxylic acid, etc.). Further, the polyhydric alcohol component contains at least ethylene glycol and / or 1,4-butanediol, and the amount thereof is 70 mol% or more (preferably 75 to 100 mol%, more preferably, 100% by mol) of the whole polyhydric alcohol component. 80 to 100 mol%). As the polyhydric alcohol component, ethylene glycol or 1,4-butanediol is often used alone. These crystalline saturated polyester resins may be used alone or in combination of two or more.

Preferred saturated polyester resins include polyesters containing terephthalic acid units, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), poly (1,4-dimethylolcyclohexane terephthalate) (PET-G), polyethylene. Examples include naphthalate (PEN), polybutylene naphthalate (PBN), and copolyesters containing ethylene terephthalate units and butylene terephthalate units as main constituent units. A more preferable crystalline saturated polyester resin is polybutylene terephthalate containing 70 mol% or more (preferably 80 mol% or more, more preferably 85 mol% or more) of a butylene terephthalate skeleton composed of terephthalic acid and 1,4-butanediol. -Based resins (for example, polybutylene terephthalate, polybutylene terephthalate copolymer in which a part of terephthalic acid is replaced with other aromatic dicarboxylic acid such as isophthalic acid, polybutylene terephthalate in which a part of butanethiol is replaced with another diol) Copolymers, etc.) are included. The polybutylene terephthalate-based resin has a characteristic that it has a high crystal-forming ability, and even if it is formed into a non-stretched film, a film having a crystallinity of 20% or more can be easily obtained, which is economically advantageous. Is. That is, when a biaxially stretched film in which a resin that is difficult to crystallize (for example, polyethylene terephthalate) is stretched to increase the degree of crystallinity is used, the crystal is transformed into an amorphous shape depending on the condition of thermal lamination, and the crystallinity of the original crystallinity is increased. Will not recover. On the contrary,
In the polybutylene terephthalate resin, even if the crystal structure becomes amorphous by heating, the crystallinity of 20% or more is easily recovered due to the excellent crystal forming ability. Therefore, it is possible to suppress the variation in the thickness of the crystalline saturated polyester resin layer set in the initial stage. Further, even if it is coated with a metal plate, it has excellent drawability and bending workability. The crystalline polyester resin layer may be formed of a stretched resin layer such as a stretched film or a non-stretched resin layer depending on the type of crystallized saturated polyester resin and the ability to form crystals. When the crystalline polyester resin layer is formed of a non-stretched resin layer, stretching treatment is not required, so that productivity can be increased and it is economically advantageous.

When the crystalline saturated polyester resin layer is formed of a film, specific examples of the film include:
Biaxially stretched polyethylene terephthalate film (for example, Toyobo Co., Ltd., ester film E5100), biaxially stretched polyethylene terephthalate film with a small stretching ratio, unstretched polybutylene terephthalate film (for example, Daicel Chemical Industries, Ltd., Senesi) E
SHG16 film, etc.) and the like.

Amorphous Saturated Polyester Resin Layer The amorphous saturated polyester resin layer is used for thermal lamination with a metal plate. The crystallinity of this amorphous saturated polyester resin layer is, for example, less than 20%, preferably 15% or less (for example, about 0 to 13%), and more preferably 10%.
% Or less (for example, about 0 to 8%), particularly 5% or less (for example, about 0 to 5%).

The amorphous saturated polyester resin may be a polyester resin having a low crystallinity, and includes, for example, a saturated polyester of a dicarboxylic acid containing terephthalic acid as a main component and a diol component containing alkylene glycol as a main component. . In the amorphous saturated polyester resin, at least one of terephthalic acid and / or alkylene glycol (in particular, ethylene glycol, 1,4-butanediol, etc.) is replaced with another polyvalent carboxylic acid and / or polyhydric alcohol. In many cases Other polyvalent carboxylic acids that can replace terephthalic acid include, for example, phthalic acid, isophthalic acid, and the like. Examples of the polyhydric alcohol that can be substituted with the alkylene glycol include propylene glycol, triethylene glycol, neopentyl glycol, cyclohexane-1,4-dimethanol and the like. The amount of terephthalic acid used is 90 mol% or less (for example, 50 to 9) of the total polycarboxylic acid component.
0 mol%), preferably 85 mol% or less (preferably 5 mol%)
0 to 80 mol%, more preferably about 50 to 75 mol%). Terephthalic acid is often used in combination with an aromatic dicarboxylic acid such as isophthalic acid. Moreover, the polyhydric alcohol component contains at least ethylene glycol and / or 1,4-butanediol, and the amount thereof is 70 mol% or more (preferably 75 to
100 mol%, more preferably about 80 to 100 mol%). The polyhydric alcohol component is at least 7
It is preferable to contain 0 mol% or more (preferably 80 mol% or more, more preferably 90 mol% or more) of 1,4-butanediol as a glycol component. That is, the amorphous saturated polyester resin is more economical than the polyethylene terephthalate-based resin in which the glycol component is ethylene glycol, from the viewpoints of economy and thermal adhesiveness at low temperatures.
It is preferably a polybutylene terephthalate resin which is 1,4-butanediol. When a polybutylene terephthalate resin is used, the melting point is often about 130 to 200 ° C., the adhesion conditions and the heat resistance level are appropriate, and it is economical because it is not a special polymer. These amorphous saturated polyester resins may be used alone or in combination of two or more.

Specific examples of the amorphous saturated polyester resin include, for example, a resin having a polyethylene terephthalate resin as a basic skeleton and a sheet or film called A-PET sheet (for example, "Tetoron sheet" manufactured by Teijin Ltd.). , Eastman Kodak Company, "Kodabond PET
G5116 "and its film), JP-A-5-328.
No. 00, JP-A-3-14925, JP-A-6-
A film molded from a polybutylene terephthalate copolymer resin described in Japanese Patent No. 55717, a polybutylene terephthalate hot melt film (“2810 film”, Daicel Chemical Co., Ltd.), a “Byron GM900 resin” manufactured by Toyobo Co., Ltd. And the like. The amorphous saturated polyester resin adhesive layer may be stretched, but is preferably a non-stretched layer in order to impart high adhesiveness. In particular, when both the crystalline saturated polyester resin layer / the amorphous saturated polyester resin adhesive layer are non-stretched layers, the metal plate can be coated with high adhesive strength and the protective effect on the metal plate can be enhanced.

The crystalline saturated polyester resin layer and /
Or, the amorphous saturated polyester resin layer, the crystallinity, processability, without impairing the adhesiveness, properties of the polyester resin,
Polycarbonate may be included, if necessary, in order to adjust the bending workability and impact resistance. Polycarbonates include polymers obtained by reacting a dihydroxy compound with phosgene or a carbonic acid ester (such as diphenyl carbonate). The polycarbonate may be an aliphatic polycarbonate or an alicyclic polycarbonate, but an aromatic polycarbonate. In particular, a bisphenol type polycarbonate derived from a bisphenol compound is often used.

Examples of the bisphenol compound include:
Bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4
-Hydroxyphenyl) propane, 2,2-bis (4-
Hydroxyphenyl) propane (bisphenol A),
2,2-bis (4-hydroxyphenyl) butane, 2,
2-bis (4-hydroxyphenyl) pentane, 3,3
-Bis (4-hydroxyphenyl) pentane, 2,2-
Bis (4-hydroxyphenyl) -3-methylbutane,
2,2-bis (4-hydroxyphenyl) hexane,
2,2-bis (4-hydroxyphenyl) 4-methylpentane, 1,1-bis (4-hydroxyphenyl) cyclopentane, 1,1-bis (4-hydroxyphenyl)
Cyclohexane, bis (4-hydroxy-3methylphenyl) methane, 1,1-bis (4-hydroxy-3-methylphenyl) ethane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2, 2-bis (4-
Hydroxy-3-ethylphenyl) propane, 2,2-
Bis (4-hydroxy-3-isopropylphenyl) propane, 2,2-bis (4-hydroxy-3-secbutylphenyl) propane, bis (4-hydroxyphenyl) phenylmethane, 1,1-bis (4-hydroxy) Phenyl) -1-phenylethane, 1,1-bis (4-hydroxyphenyl) -1-phenylpropane, bis (4
-Hydroxyphenyl) diphenylmethane, bis (4-
Hydroxyphenyl) dibenzylmethane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide and the like. These bisphenol compounds may be used alone or in combination of two or more. The preferred polycarbonate has heat resistance,
Bisphenol A-type polycarbonate and the like are included in terms of processability and economy. Specific examples of the polycarbonate include "Upilon" manufactured by Mitsubishi Gas Chemical Co., Inc., "Panlite" manufactured by Teijin Chemicals Ltd., "Lexan" manufactured by Nippon GE Plastics Co., Ltd., and the like.

The molecular weight of the polycarbonate can be selected within a range that does not adversely affect the properties of the coated metal plate.
The weight average molecular weight is 1 × 10 ^{4 to} 20 × 10 ⁴ , preferably about 1 × 10 ⁴ to 10 × 10 ⁴ .

The content of the polycarbonate in the crystalline saturated polyester resin layer can be selected within a range that does not impair the properties of the polyester resin without excessively suppressing crystallization, and for example, crystalline polyester resin / polycarbonate = 80 / 20-100 / 0 (wt%), preferably 80 / 20-95 / 5 (wt%), more preferably 9
It is about 0/10 to 95/5 (% by weight). The content of polycarbonate in the amorphous saturated polyester resin layer can be selected within a range that does not impair the crystallinity and does not impair the characteristics and processability of the polyester resin. For example, amorphous polyester resin / polycarbonate = 95
/ 5 to 60/40 (wt%) (for example, 90/10 to 6)
5/35 (wt%)), preferably 85/15 to 70 /
30 (wt%), more preferably 80/20 to 70 /
It is about 30 (% by weight).

The crystalline saturated polyester resin and / or the amorphous saturated polyester resin may contain various additives such as stabilizers such as antioxidants and ultraviolet absorbers, plasticizers, flame retardants, and crystals, if necessary. Nuclear growth agent, lubricant, filler,
It may contain a coloring agent or the like.

The layer structure of the film may be such that an amorphous polyester resin layer as an adhesive layer is laminated on at least one surface of the crystalline polyester resin layer, and the amorphous saturated polyester resin layer is a crystalline saturated polyester resin. You may laminate on both surfaces of a layer. In such a film, the amorphous polyester resin layer can be used to firmly and thermally adhere to a metal plate in a wide temperature range. Further, an intermediate layer such as an adhesive layer may be interposed between the crystalline polyester resin layer and the amorphous polyester resin layer. From the economical point of view, a simple layer structure, for example, a two-layer structure film of crystalline polyester resin layer / amorphous polyester resin layer, or three layers of crystalline polyester resin layer / adhesive layer / amorphous polyester resin layer Includes structural films and the like. The adhesion method between layers of each layer is not particularly limited,
The crystalline polyester resin layer and the amorphous polyester resin layer may be laminated using an adhesive, but when each layer is thermally adhered by a film forming method such as a multi-layer coextrusion molding method or an extrusion laminating method or a heat laminating method. A film having high integrity and stable characteristics can be efficiently and economically produced.

The thickness of the coating film can be selected according to the coating property and protection property of the metal plate, for example, 5 to 3
00 μm, preferably 10 to 200 μm, further 15
˜150 μm, especially about 20 to 100 μm. Further, the ratio of the thickness of the crystalline polyester resin layer and the amorphous polyester resin adhesive layer can be selected within a range that does not impair the adhesiveness to the metal plate and the protective property, for example, with respect to the thickness of the entire film, Crystalline polyester resin layer / amorphous polyester resin adhesive layer = 50/50 to 95/5
%, Preferably 60/85 to 90/10%, more preferably 70/30 to 85/15%. The minimum thickness of each layer is 2 to 3 μm or more.

In order to smoothly heat-laminate the film on a metal plate, the melting point of the crystalline saturated polyester resin should be Tm.
c. When the melting point of the amorphous saturated polyester resin is Tma, each melting point preferably satisfies the following relational expression. 80 ° C. <Tma <(Tmc-5) ° C., preferably 90 ° C. <Tma <(Tmc-10) ° C. When the melting point Tma of the amorphous saturated polyester resin is less than 80 ° C., the heat resistance of the coated steel sheet by lamination is lowered. If the melting point Tma is too high, the crystalline polyester resin layer or the amorphous polyester resin layer may be thermally deteriorated due to thermal lamination. The crystalline saturated polyester resin often has a melting point Tmc of, for example, about 180 to 300 ° C., preferably about 200 to 280 ° C., and the amorphous saturated polyester resin has a melting point Tma of, for example, 100.
-250 degreeC, Preferably it is about 100-230 degreeC in many cases.

The film of the present invention is useful for coating a metal plate. The metal plate may be in any form such as a foil shape, a sheet shape, and a coil shape, and as the metal plate, for example, a steel plate, an iron plate, an aluminum plate, a surface-treated metal plate or the like can be used. The surface-treated metal plate includes, for example, a metal chrome layer as an underlayer, an electrolytic chromic acid treated steel plate having a layer of hydrated chromium oxide as an upper layer, an ultra-thin tin-plated steel sheet, an ultra-thin iron-tin alloy-coated steel sheet, an ultra-thin chrome Plated steel sheet, nickel-plated steel sheet, copper-plated steel sheet, zinc-plated steel sheet, chromium hydrate oxide-coated steel sheet, treated steel sheet such as organic matter treated steel sheet, phosphoric acid treated steel sheet, chromate treated steel sheet, aluminum sheet treated with these treatments, etc. Is included. Organic matter treatment, for example,
A metal plate treated with a polar group such as a carboxyl group or a compound capable of forming a chelate is included. The processing of the metal plate is
It can be carried out by combining one kind or two or more kinds.

The film is laminated on the metal plate by a thermal laminating method. That is, a coated metal plate can be obtained by bringing the amorphous polyester resin layer into contact with a metal plate heated to a predetermined temperature to laminate a film, press-bonding the film with a laminating roll, and then cooling. The laminating roll may be heated or heated to a predetermined temperature (for example, a temperature equal to or lower than the melting point of the crystalline polyester resin layer).

In the method of the present invention, it is important to set the heating temperature of the metal plate, that is, the thermal laminating temperature. That is,
When the melting point of the crystalline saturated polyester resin is Tmc, the heating temperature can be selected within the following temperature range, for example. (Tmc-120) ° C. to (Tmc + 100) ° C., preferably (Tmc-100) ° C. to (Tmc + 80) ° C. If the heating temperature is too low, the adhesiveness will decrease, and if it is too high, the film will be prone to thermal deterioration.

Another feature of the method of the present invention cannot be realized by using a film having the above-mentioned laminated structure, at a temperature not higher than the melting point Tmc of the crystalline polyester resin, that is, a conventional saturated crystalline polyester resin single layer film. It can be heat-bonded at a high temperature. The thermal laminating temperature is, for example, as follows. (Tmc-120) ° C to (Tmc) ° C, preferably (Tmc-100) ° C to (Tmc-10) ° C Further, the thermal laminating temperature is 150 ° C or lower, for example,
When (Tmc-120) ° C. to 150 ° C., even if a film is printed or a pattern is formed, the surface of the film is not deteriorated and a coated metal plate having a good appearance can be obtained.

The temperature of the laminating roll, the nip pressure and the cooling conditions can be appropriately selected within a range that does not impair the adhesion according to the thickness of the coated metal plate or the film, and are not particularly limited. When the polybutylene terephthalate-based resin is used for the crystalline polyester resin layer, the crystallinity is recovered as described above even if the polyester resin is melted. It can be set according to economic efficiency, productivity, device characteristics, etc. within a range that does not impair. When a polyethylene terephthalate resin is used for the crystalline polyester resin layer, the thermal laminating temperature or the like may be set so that the crystallinity does not decrease.

The coated metal plate thus obtained has high surface protection and adhesion between the film and the metal plate. Furthermore, it has high workability and is excellent in drawability and bending workability. For example, when two parallel notches are formed in the film on the surface of a laminated steel sheet at intervals of 5 mm in width and length, and subjected to an Erichsen test according to JIS K5400, the film peels off unlike the biaxially stretched polyethylene terephthalate film. Does not happen.
Further, the metal plate and the film are in close contact with each other with high adhesion, and the metal plate is provided with high corrosion resistance.

[0036]

The film for coating a metal plate of the present invention can be thermally laminated to a metal plate by utilizing the amorphous saturated polyester resin layer laminated on at least one surface of the crystalline saturated polyester resin layer. The high crystallinity can be maintained, the metal plate can be effectively protected, and the surface protection is high. Further, it is possible to perform thermal lamination with high adhesion to a metal plate without using an adhesive, and suppress thermal degradation. According to the method of the present invention, it is possible to obtain a coated metal sheet which can be heat-laminated at a relatively low temperature, has high production efficiency, and has high adhesion, durability and workability between the metal sheet and the film.

[0037]

The present invention will be described below in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The materials used in the examples and comparative examples are as follows. Metal plate: Cold-rolled steel plate (thickness 0.4 mm) electrogalvanized and coated with polyester type paint color steel plate (Nippon Steel Corp., Elio steel plate) Crystalline polyester resin layer: Polyester resin: Poly Butylene terephthalate (PBT) homopolymer (manufactured by Polyplastics Co., Ltd., Duranex 600F)
P, Tmc = 225 ° C) Polyester film: PET-1 (manufactured by DIAFOIL Co., Ltd., DIAFOIL T1)
00E, 25 μm, Tmc = 260 ° C.) Amorphous polyester resin layer: Polyester resin: Modified PBT-1 (manufactured by Polyplastics Co., Ltd., Duranex 600LP, Tmc = 170 ° C.) Modified PET-1 (Mitsui DuPont Co., Ltd.) Made, Sealer PT
8307, Tmc = 221 ° C.) Modified PBT-2 (manufactured by Toyobo Co., Ltd., Byron GM900,
Modified PET-2 (manufactured by Eastman Kodak Co., Ltd., Kodabond PET-G5113, Tmc = 180 ° C) Polyester film: PET-2 (manufactured by Toyobo Co., Ltd., ester film E510)
Denatured PBT-3 (manufactured by Daicel Chemical Industries, Ltd., Thermolite 2810, 30 μm, Tmc = 137 ° C) Polycarbonate (manufactured by Mitsubishi Gas Chemical Co., Inc., Iupilon S3000) The film for coating a metal plate in, as a polyester forming a crystalline polyester resin layer or an amorphous polyester resin layer,
As shown in the table, the resin or film of No. 1 was used and any one of a coextrusion molding method, an extrusion laminating method, and a thermal laminating method was used. In addition, PET-1 and PE
Regarding the T-2 film, an amorphous molybdenum ester resin layer was laminated on the surface-treated surface. In Examples 2 and 6, modified PBT-1 and polycarbonate were used as the composition for forming the amorphous polyester resin layer in the ratio of former / latter = 80/20 (parts by weight).

Then, the steel sheet was heated to the temperature shown in the table by a heat roll heating method, a silicone roll having a temperature of 125 ° C. was used as a laminating roll, and the amorphous polyester resin layer was brought into contact with the steel sheet at a laminating speed of 150 m / min. It was heat-laminated and cooled with water to a temperature of 60 ° C. or lower to prepare a coated steel sheet.

The characteristics of the obtained coated steel sheet were measured as follows, and the results shown in the table were obtained. Adhesive strength: 180 ° at a pulling speed of 100 mm / min
The peel strength was measured and the adhesiveness was evaluated according to the following criteria. Excellent: Adhesive strength is 1.5 kg / 15 mm or more, and the film breaks without interfacial peeling. Poor: Adhesive strength is less than 1.5 kg / 15 mm, interfacial peeling. Crystallinity: For the laminated film, each layer A sample obtained by thermally laminating the corresponding film in the same manner as above was measured by the wide-angle X-ray diffraction method. Machining adhesion: Two cross-shaped notches that are parallel to each other at a width of 5 mm are formed, and the Erichsen test (JIS
K5400) was evaluated according to the following criteria. Excellent: No change is observed in the coating film Good: Some small cracks are generated in the coating film Poor: Cracks are generated in the coating film Surface protection: Scratch the polyester coating layer of the steel sheet with a cutter, and perform as described above. Heat-laminate the film,
After standing in a 3 wt% NaCl aqueous solution at 55 ° C. for 3 days, the appearance was observed and evaluated according to the following criteria.

Excellent: No corrosion of steel plate No: Corrosion of steel plate

[0041]

[Table 1] As is clear from the table, in the examples, it is possible to carry out heat lamination at a relatively low temperature, and the crystalline polyester resin layer has a high degree of crystallinity, and a coated steel sheet having high surface protection and high adhesive strength can be obtained. Further, the workability of the coated steel sheet is also high.

Claims (12)

[Claims] 1. A film for coating a metal plate, wherein an amorphous saturated polyester resin layer for thermal lamination to a metal plate is laminated on at least one surface of the crystalline saturated polyester resin layer. 2. The film for coating a metal plate according to claim 1, wherein a crystalline saturated polyester resin layer having a crystallinity of 20% or more and an amorphous polyester resin layer having a crystallinity of less than 20% are laminated. 3. The metal according to claim 1, wherein the crystalline saturated polyester resin layer is composed of a polybutylene terephthalate resin containing 70 mol% or more of a butylene terephthalate skeleton composed of terephthalic acid and 1,4-butanediol. Film for board coating. 4. The film for coating a metal plate according to claim 1, wherein 70 mol% or more of the glycol component of the amorphous saturated polyester resin is 1,4-butanediol. 5. The film for coating a metal plate according to claim 1, wherein the crystalline saturated polyester resin layer and the amorphous saturated polyester resin layer are non-stretched resin layers. 6. The melting point of the crystalline saturated polyester resin is T
The film for coating a metal plate according to claim 1, wherein mc is 80 ° C <Tma <(Tmc-5) ° C, where Tma is the melting point of the amorphous saturated polyester resin. 7. The film for coating a metal plate according to claim 1, wherein the crystalline saturated polyester resin layer is formed of a resin composition containing 80 to 95% by weight of a crystalline saturated polyester resin and 20 to 5% by weight of a polycarbonate. . 8. The film for coating a metal plate according to claim 1, wherein the amorphous saturated polyester resin layer is formed of a resin composition containing 60 to 95 wt% of the amorphous saturated polyester resin and 40 to 5 wt% of the polycarbonate. . 9. A coated metal plate in which a crystalline saturated polyester resin layer is laminated on at least one surface of the metal plate via an amorphous saturated polyester resin layer. 10. A method of thermally laminating a crystalline saturated polyester resin layer on at least one surface of a metal plate, wherein the melting point of the crystalline saturated polyester resin is Tmc, (Tmc-120) ° C. A method for producing a coated metal plate, comprising laminating a crystalline saturated polyester resin layer on the surface of the metal plate heated to (Tmc + 100) ° C. with an amorphous saturated polyester resin layer interposed therebetween. 11. The method for producing a coated metal sheet according to claim 10, wherein heat lamination is performed at a temperature of (Tmc-120) ° C. to (Tmc) ° C. 12. The method for producing a coated metal plate according to claim 10, wherein heat lamination is performed at a temperature of (Tmc-120 ° C.) to 150 ° C.