JP4447719B2 - Metal can weld repair film - Google Patents

Description

【００５５】
【表２】

【００５６】
【発明の効果】
本発明のポリエステルフィルムは、接着性、耐衝撃性、耐腐食性等に優れ、加熱やレトルト処理によっても剥離し難く、また、ポリエステルにより形成されるため環境特性に極めて優れており、特に金属飲料缶などの溶接部の耐食被膜として有用であり、その工業的価値は高い。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat-fusible polyester film used for repairing a metal can weld. More specifically, the present invention relates to a repair film that is coated for the purpose of preventing corrosion or metal elution of a metal plate exposed from a surface protective layer after welding in the process of making a metal can.
[0002]
[Prior art]
In recent years, metal welded cans have been used in a wide range of applications as storage containers regardless of food or non-food. The surface of the can of metal welded cans is rarely used as it is, and surface treatment for protecting the inner and outer surfaces of the can from rusting, scratches, dirt, etc. is performed by, for example, coating or film bonding.
[0003]
For example, in a can manufacturing process of a three-piece steel can for beverages, which is a typical metal welded can, a surface protection treatment is first performed on a steel plate. Examples of these treatment methods include a method of applying a paint and laminating a resin film by an adhesive or heat fusion. The steel plate subjected to surface treatment is cut into a desired size, and then a cylindrical can body is manufactured from the cut steel plate by welding, and then the can body is wound up and down by tightening the can lid Is manufactured.
[0004]
However, in the can manufacturing process of the three-piece steel can, there is an inevitable problem that the underlying steel plate is exposed after the can body is welded. Specifically, after welding, a protective treatment layer is not placed on a portion having a width of about several millimeters in the vicinity of the weld bonded portion, and the underlying steel is exposed.
[0005]
As it is, the exposed steel will corrode due to contact with the contents of the can or the outside air, so at present, organic paints such as epoxy / phenolic paints and vinyl chloride organosol paints are used as corrosion prevention treatments. The repair painting that had been carried out was carried out after the can body was manufactured.
[0006]
However, there are some problems with the current repair painting with organic paints. For example, pinhole-like coating defects may occur even when the repair coating process is performed. Currently, we are dealing with increasing the amount of paint applied and the number of paintings, but it is still difficult to eliminate the occurrence of cans with coating defects in the repair area. Still have problems in terms of performance and yield. In addition, the coating application process requires a facility for recovering the solvent generated in the baking process by high-temperature heating, and there are problems such as a heavy burden from the viewpoint of manufacturing equipment cost and the extremely large energy consumption required for the baking process. is there.
[0007]
Furthermore, in recent years, organic paints such as epoxy / phenolic resins and vinyl chloride organosol paints are being shunned by users, and can makers are beginning to refrain from using them.
[0008]
Recently, studies are being made on organic solvent-based paints or dehalogenated paints such as water-based paints, ultraviolet curable paints, and powder paints, which are next-generation paints that replace the current paints. However, the present condition is that the coating material which has protection performance like the conventional organic coating material is not yet developed.
[0009]
In addition, organic coating agents generally have a large amount of adsorbed material from the can contents, and have the major disadvantages of reduced can taste and poor flavor characteristics.
[0010]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and the problem to be solved is to solve environmental characteristics and rust prevention problems that could not be achieved by conventional coating-type repair agents, and further, impact resistance and adhesion. Another object of the present invention is to provide a polyester film for repairing a welded portion of a metal can that is excellent in the above.
[0011]
[Means for Solving the Problems]
As a result of intensive studies in view of the above problems, the present inventors have found that the above-described problems can be solved when a polyester film having specific physical properties is used, and the present invention has been achieved.
[0012]
That is, the gist of the present invention is an amorphous polyester having a melting point of 180 to 240 ° C., one surface layer (A) composed of heat-fusible polyester a, and a glass transition temperature of 60 to 150 ° C. b or et intermediate layer (B) is formed, the total polyhydric alcohol component constituting the amorphous polyester b, 1,4-cyclohexanedimethanol content of 20 to 40 mol%, a melting point of polyester a film der of the laminated structure other surface layer of polyester c (C) is configured at least the melting point of Ri, a, thickness of each layer of the B and C (dA, dB, dC) and total thickness (dT) is It exists in the metal can welded part repair film characterized by satisfying following formula (1)-(3) simultaneously .
dB / dT ≧ 0.2 (1)
dC / (dA + dB) ≦ 3 (2)
dT ≦ 100 μm (3)
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
[0014]
The metal can welded part repair film of the present invention (hereinafter referred to as repair film) is, for example, a polyester obtained by polycondensation of dicarboxylic acid and diol, or a mixture of polyester obtained by condensation polymerization from dicarboxylic acid and diol. It is a laminated film composed of a plurality of layers.
[0015]
As the dicarboxylic acid component of the polyester constituting each layer of the laminated film, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, decanedicarboxylic acid, azelaic acid, dodecadicarboxylic acid, cyclohexane Examples of the diol component include ethylene glycol, butanediol, hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, decanediol, 2-ethyl-2-butyl-1-propanediol, and the like. Can be mentioned. Among these, it may be a copolymer of three or more kinds of dicarboxylic acid or diol, or a copolymer with a monomer or polymer such as diethylene glycol, triethylene glycol, or polyethylene glycol.
[0016]
The melting point (Tm _A ) of polyester a constituting one surface layer A of the film of the present invention is 180 to 240 ° C., preferably 190 to 235 ° C. When the melting point of the polyester is less than 180 ° C., when a retort treatment is applied after can processing, the repair film may be peeled off or wrinkles may be generated. Also, if the melting point exceeds 240 ° C, it can have sufficient thermal adhesiveness to the paint surface coated on the can surface, printed surface, laminated protective resin film, exposed can material such as steel and aluminum. Since it is not, it is not preferable.
[0017]
Furthermore, the polyester a needs to have the above-mentioned melting point and heat fusion properties. In the present invention, the heat melting property means that the polyester is heated to a glass transition temperature of + 60 ° C. or higher, and press-contacted to the target adherend, for example, the inner surface of the can body or the welded portion of the can body, and then to around room temperature. Even when the temperature is lowered, it means that the temperature is kept in close contact with the adherend.
[0018]
Moreover, it is preferable that the intrinsic viscosity (IV) of the polyester a is in the range of 0.40 to 1.50. When IV exceeds 1.50, the productivity of the raw material resin and the film may decrease. If IV is less than 0.40, impact resistance and heat resistance may be lowered.
[0019]
The polyester constituting the intermediate layer B of the film of the present invention is an amorphous polyester b having a glass transition temperature (Tg) of 50 to 150 ° C., or a crystalline polyester b having a melting point (Tm _B ) of Tm _A −10 ° C. or less. 'Is.
[0020]
When Tg of the amorphous polyester exceeds 150 ° C., the adhesion to the welded portion may be insufficient, and when it is less than 50 ° C., the heat resistance is insufficient, which is not preferable. The Tg of the amorphous polyester b is preferably 60 to 120 ° C.
[0021]
On the other hand, the melting point (Tm _B ) of the crystalline polyester b ′ is preferably Tm _A −20 ° C. or lower. When Tm _B exceeds Tm _A -10 ° C, the adherence to the step of the welded part of the film becomes insufficient, and after the retort treatment, corrosion occurs in the can material under the repair film or the repair film is peeled off. Therefore, it is not preferable.
[0022]
The intrinsic viscosity (IV) of polyester b is in the range of 0.40 to 1.50. When IV exceeds 1.50, productivity may be reduced. If IV is less than 0.40, impact resistance and heat resistance may be lowered.
[0023]
The melting point (Tm _C ) of the polyester c constituting the other surface layer C of the repair film of the present invention is Tm _A That is necessary. Tm _A If it is less than, when heat lamination at a temperature above the Tm _A ° C. from near Tm _A ° C. in order to ensure sufficient adhesion, the surface constituted by polyester c laminating - or stick to the roll coater, repair This is not preferable because wrinkles and scratches may occur on the film surface or may peel off.
[0024]
The film of the present invention is coated on the exposed portion in order to repair the exposed portion of the can material generated in the process of making the metal can.
[0025]
Although there is no restriction | limiting in particular in the total thickness of the film of this invention, in the case of a metal drink can, it is 5-100 micrometers normally, Preferably it is 10-75 micrometers, More preferably, it is 15-50 micrometers. If the total thickness is less than 10 μm, impact resistance and rust resistance tend to be insufficient, and if it exceeds 100 μm, there may be cases where the step does not adhere to a step present in the can weld.
[0026]
It is preferable that each layer thickness dA, dB, dC and total thickness (dT) of the repair film of the present invention satisfy the following formulas simultaneously.
[0027]
[Expression 2]
dB / dT ≧ 0.2 (1)
dC / (dA + dB) ≦ 3 (2)
dT ≦ 100 μm (3)
If the repair film thickness ratio dB / (dA + dB + dC) is less than 0.2, dC / (dA + dB) exceeds 3, or the total thickness exceeds 100 microns, the step shape of the metal can weld trace will be caused by thermal lamination. May not sufficiently adhere to the surface, resulting in inferior impact resistance, rust resistance, and heat resistance.
[0028]
The film of the present invention preferably contains lubricant particles and the film has slipperiness. In particular, the polyester A and / or polyester C in the surface layer preferably contains lubricant particles. Although there is no restriction | limiting in particular in the particle diameter which a polyester film contains, Generally it is preferable that an average particle diameter is 0.01-5.0 micrometers, Furthermore, it is preferable that it is 0.02-3.0 micrometers. Moreover, the compounding quantity of a lubricant particle is 0.01 to 1.0 weight% normally, and 0.05 to 0.5 weight% is still more preferable. The particles may be either inorganic or organic, but are preferably inorganic from the viewpoint of cost.
[0029]
In the film of the present invention, the protective coating is applied to both surfaces or one surface of the metal plate, the resin film is laminated by an adhesive or heat fusion, or the molten thermoplastic resin is cast on both surfaces or one surface of the metal plate. After that, the metal plate is cut into a desired size and canned by welding, for example, canned foods represented by beverage cans, pail cans, tin plate 18L cans, steel drums and other repair films Is preferred.
[0030]
Moreover, there is no restriction | limiting in particular in the raw material kind of can material, What is necessary is just a metal material generally used for can-making, for example, tin, TFS (chin free steel), aluminum etc. are mentioned. Moreover, there is no restriction | limiting in particular in the welding method of a metal can, The method used conventionally may be used, and the welding can said here may be the thing which has exposure of can material after welding and needs repair. . Moreover, even if it is a metal can which performs can body bonding with an adhesive agent, when there exists exposure of a can material, the repair film of this invention is used suitably.
[0031]
The production method of the film of the present invention is not particularly limited as long as it does not exceed the gist of the present invention. Generally, the raw material polyester is first melted in an extruder (in the case of a laminated structure, it is preferable to co-extrusion at this stage), extruded from a T die, and then rapidly cooled with a cooling roll to be amorphous. From the viewpoint of productivity, a forming method in which the sheet is heated to the glass transition temperature or higher of the raw material polyester and then longitudinally stretched, laterally stretched and sequentially stretched or simultaneously stretched is suitable.
[0032]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these examples at all unless it exceeds the summary. In addition, the evaluation method of the film of this invention and the manufacturing method of a raw material are as follows.
(1) Production of resin film-bonded steel plate welding sample Polyester resin (melting point 254 ° C) polycondensed from terephthalic acid and ethylene glycol was extruded at 290 ° C and rapidly cooled with a cooling drum at 70 ° C to form an unstretched film. Obtained. Next, this unstretched film was stretched 3.7 times in the longitudinal direction at 85 ° C., stretched 4.0 times in the transverse direction at 120 ° C., and then heat-set at 220 ° C. to thereby form a biaxial film having a thickness of 12 μm. A stretched polyethylene terephthalate film was obtained.
[0033]
Next, the film obtained on a steel plate having a thickness of 0.2 mm cut into 300 mm square was bonded to both surfaces using a urethane resin adhesive, and then heat-treated at 150 ° C. for 6 hours in a hot air oven. A double-sided polyester film laminate sample plate having a height of 70 to 100 microns and a steel material exposed at a width of 4.0 to 5.0 mm centered on the level difference. About 300 mm × 600 mm × 0.2 mm).
(2) After a film sample is cut into a tape shape having a repair film laminate width of 10 mm and a length of 300 mm, both sides of the double-sided polyester film laminate sample plate obtained in (1) above are obtained on the laminator device. On the other hand, the tape was aligned and laminated so as to cover the welded portion. In a laminating apparatus having two upper and lower metal rolls subjected to surface processing with Teflon, the pressure was adhered to both surfaces of a double-sided polyester film laminate sample plate at a laminating speed of 25 m / min and a roll pressure of 0.3 MPa.
[0034]
Subsequently, the following items (3) to (10) were evaluated.
(3) Whether or not the step adhesion repair film is in close contact with the double-sided polyester film laminate sample plate (especially according to the shape of the weld step), the cross section of the obtained sample piece is observed with an optical microscope, and the following criteria Evaluated.
[0035]
○: Adhering in accordance with the step Δ: Floating is observed in the step portion when the roll speed is 25 m / min, but it adheres in accordance with the step when the roll speed is lowered to 10 m / min. X: Up to 5.0 m / min of the roll speed Even if dropped, it does not adhere to the level difference and has a float. (4) Impact resistant repair film Dent processing is performed on one side of the coated surface with a DuPont impact tester to repair impact from outside the can. Resistance index. The striker tip R was 3/16 inch, the falling distance was 30 cm, and the falling weight mass was 500 g. After the test, the state of the coated film surface (peeling, cracks, etc.) was observed with an electron microscope and evaluated according to the following criteria.
[0036]
○: Peeling and cracks are not observed at any falling distance ×: Peeling and cracking are observed at any falling distance (5) After denting on the heat-resistant repair film coated surface under the same conditions as the impact resistance evaluation Then, after heat treatment at 200 ° C. for 5 minutes in a hot air oven, the adhesion state of the film in the dents recess was observed and confirmed.
[0037]
○: No peeling is observed on the film at any heat treatment temperature. X: The film at the dents part peels off at any heat treatment temperature. (6) Polyester Melting Point TI Instruments Differential Scanning Calorimeter MDSC2920 The melting point (hereinafter “Tm”) and glass transition temperature (hereinafter “Tg”) of the raw material polyester were measured. The measurement conditions were a heating rate of 10 ° C./min, and the melting point of the polyester was the endothermic peak temperature due to crystal melting obtained.
(7) Intrinsic viscosity [η] (dl / g)
1 g of the polymer was dissolved in 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) and measured at 30 ° C.
(8) After the sample plate coated with the corrosion-resistant repair film was stored at 30 ° C. for 1 month in a beaker containing a 5% NaCl aqueous solution, the corrosion state of the steel material under the repair film coating was observed.
[0038]
○: The steel plate under the film covering part was unchanged after 1 month.
X: Corrosion was observed on the steel plate under the film coating after one month.
(9) Film thickness The cross section of the film was observed with a scanning electron microscope (SEM), and the thickness was measured.
(10) The retort-treated film-coated surface was dented under the same conditions as the impact resistance evaluation and then subjected to a retort treatment at 125 ° C. for 30 minutes, and then the adhesion state of the film in the dents recess was observed and confirmed.
[0039]
○: No peeling or whitening is observed on the film of the dents part ×: The film of the dents part is peeling or the film is whitening [0044]
Examples 1 and 2
Polyester a1 polycondensed from terephthalic acid, isophthalic acid and ethylene glycol (isophthalic acid content in the polyester is 12 mol%, Tm = 226 ° C., [η] = 0.67), terephthalic acid, ethylene glycol, 1,4-cyclohexane Polyester resin e1 polycondensed from dimethanol (cis / trans ratio = 32/68 mol% ratio) (1,4-cyclohexanedimethanol content in the polyester is 24 mol%, Tm = none, Tg = 79.9 ° C. , [Η] = 0.78), polyester resin c1 polycondensed from terephthalic acid and ethylene glycol (Tm = 253 ° C., [η] = 0.70) were melted separately, and the flow paths were aligned immediately before The film was coextruded from a T die at 290 ° C. and quenched with a cooling drum at 70 ° C. to obtain an unstretched film. This unstretched film is stretched 3.5 times in the longitudinal direction at 83 ° C., stretched 3.8 times in the transverse direction at 120 ° C., and then heat-set at 230 ° C. to thereby obtain a polyester A layer (derived from polyester a1) ) A film having a thickness of 2.5 μm, a polyester B layer (derived from polyester e1) of 20 μm, a polyester C layer (derived from polyester c1) of 2.5 μm, and a total thickness of 25 μm was obtained (Example 1). Instead of polyester resin e1, polyester resin f1 polycondensed from terephthalic acid, ethylene glycol, 1,4-cyclohexanedimethanol (content of 1,4-cyclohexanedimethanol in the polyester is 36 mol%, Tm = none, Tg = 82) A film was obtained in the same manner as in Example 1 except that 0.5 ° C. and [η] = 0.80) were used (Example 2). This repair film has excellent step adhesion even when the roll speed is increased from 25 m / min to 75 m / min, and also has excellent impact resistance, heat resistance and retort resistance. No corrosion was observed on the part.
[0047]
Comparative Example 1
In Example 1, instead of polyester a1, polyester h1 polycondensed from terephthalic acid, isophthalic acid and ethylene glycol (isophthalic acid content in the polyester 2.4 mol%, Tm = 248 ° C., [η] = 0.64) The film was obtained in the same manner as in Example 1 except that the roll temperature was 250 ° C. The obtained film was inferior in step adhesion, heat resistance, and retort resistance, and a black spot (= corrosion) was observed under the coating after one month.
[0048]
Comparative Example 2
In Example 1, a film was obtained in the same manner as in Example 1 except that polyester b1 was used instead of polyester c1. The film obtained could not be laminated at a roll temperature of 230 ° C. because the repair film would stick to the roll. By reducing the roll temperature to 200 ° C., no adhesion occurred on the roll, but the film could not be laminated.
[0049]
Comparative Example 3
In Example 1, a film was obtained in the same manner as in Example 1 except that polyester a1 was used instead of polyester b1. The obtained film was inferior in the step adhesion and retort resistance, and a black spot was observed under the covering part after one month.
[0050]
Comparative Examples 4 and 5
In Example 1, a film was obtained in the same manner as in Example 1 except that each layer thickness of the film was as described in the following table. The obtained film was inferior in level difference adhesion and retort resistance, and a black spot was observed under the coating after one month.
[0051]
Comparative Example 6
Example 1 Example 1 except that amorphous polyester resin i1 (Tm = none, Tg = 182 ° C.) composed of bisphenol A and isophthalic acid / terephthalic acid = 90/10 mol% was used instead of polyester b1. A film was obtained in the same manner as in 1. The obtained film was inferior in level difference adhesion and retort resistance, and a black spot was observed under the coating after one month.
[0052]
Comparative Example 7
In Example 1, instead of polyester a1, polyester j1 polycondensed from terephthalic acid, isophthalic acid and ethylene glycol (isophthalic acid content 32 mol% in polyester, Tm = 176 ° C., [η] = 0.66) A film was obtained in the same manner as in Example 1 except that it was used. The obtained film was inferior in heat resistance, impact resistance and retort resistance, and a black spot (= corrosion) was observed under the coating after one month.
[0053]
The results thus obtained are summarized and shown in Tables 1 and 2 below.
[0054]
[Table 1]

[0055]
[Table 2]

[0056]
【The invention's effect】
The polyester film of the present invention is excellent in adhesion, impact resistance, corrosion resistance, etc., hardly peeled off by heating or retort treatment, and is extremely excellent in environmental characteristics because it is formed of polyester, particularly metal beverage It is useful as a corrosion-resistant coating for welds such as cans, and its industrial value is high.

Claims (1)

A melting point of 180 to 240 ° C., one surface layer of a polyester A having a heat fusion property (A) is formed, amorphous polyester b or et intermediate layer having a glass transition temperature of 60 to 150 ° C. (B) In the total polyhydric alcohol component constituting the amorphous polyester b, 1,4-cyclohexanedimethanol content is 20 to 40 mol%, and the melting point is higher than the melting point of the polyester a. Ri film der of the laminated structure other (C) of the surface layer is constituted, a, thickness of each layer of the B and C (dA, dB, dC) and total thickness (dT) is the following formula (1) to (3 ) Is a metal can weld repair film.
dB / dT ≧ 0.2 (1)
dC / (dA + dB) ≦ 3 (2)
dT ≦ 100 μm (3)