JP5072791B2 - How to paint strip metal plate - Google Patents

Description

  In the present invention, all or most of the solid content of the paint is composed of a dicarboxylic acid component and a glycol component, the dicarboxylic acid component is composed of naphthalene dicarboxylic acid and terephthalic acid, and the glycol component is ethylene glycol and cyclohexanedimethanol (1,1). 4-cyclohexanedimethanol), which is a uniform and thin film on a strip metal plate, using a paint in which resin fine particles mainly composed of quaternary amorphous polyethylene naphthalate resin are dispersed in a solvent. It relates to the method of painting.

  In recent years, instead of coating paint on a strip metal plate for manufacturing packaging containers, electrical parts, automobile parts, etc., by laminating a thermoplastic resin film such as polyester resin on the strip metal plate in advance, One side or both sides are coated with a thermoplastic resin coating, and coating after molding (that is, post-coating) is omitted by molding parts such as packaging containers and electrical parts from this coated metal strip. Things have come to be done widely.

  As an example of the forming process using a resin-coated metal plate, for example, in the case of a packaging container, first, a shallow cup is formed by punching drawing process, and the redrawing process is further performed once or again on the shallow cup. By performing the process twice or more, the process of molding a seamless can with a bottom with a smaller diameter and a larger cup height (about 1.5 to 3.0 times the diameter) or punching 2. Description of the Related Art Conventionally known is a process for forming a can lid by drawing a concave part and a convex part and performing a score engraving process after drawing. When such processing is applied to a resin-coated metal plate, stress is applied not only to the metal plate but also to the resin coating that covers the surface of the metal plate. In order to reduce the stress, it is desirable to remove the stress by performing a heat treatment for heating for a predetermined time at a temperature equal to or higher than the glass transition point of the resin forming the resin film.

  When the resin film covering the surface of the metal plate is a thermoplastic resin such as a polyester resin mainly composed of polyethylene terephthalate, even if the surface is shallowly scratched (such as shaved or streaky) Even if a scratch or the like occurs, the resin film is softened by this heat treatment, and the damaged portion is repaired incidentally, especially by setting the heat treatment temperature to a temperature near or above the melting point of the film resin. Has the advantage of being able to repair the wound almost completely.

  By the way, as a method of laminating such a thermoplastic resin film on a belt-shaped metal plate, a thermoplastic resin film formed by extruding a previously melted thermoplastic resin from a T-die of an extruder and cooling it to a predetermined temperature is used. After stretching in a uniaxial or biaxial direction to form a thin film, this thermoplastic resin film is laminated directly to a heated metal strip or via an adhesive layer, and from the T die of an extruder There is a method of laminating an extruded molten thermoplastic resin film directly on a metal strip. However, regardless of which method is used, it is necessary to install a considerably large laminate facility. In addition, when the latter extrusion film laminating method is adopted, a thin film-like film cannot be formed only by the melt extrusion method, so that a considerably thick thermoplastic resin film is necessarily laminated on the belt-like metal plate. As a result, the amount of thermoplastic resin used increases, resulting in the use of extra resin.

  Now, the method of laminating a thermoplastic resin on a belt-shaped metal plate is an environmentally friendly resin coating method because it does not use an organic solvent that causes air pollution or environmental pollution as compared with a coating method. However, the thermoplastic resin laminated to the metal plate is usually limited to a film having a thickness of 10 μm or more commercially, and a thinner film, for example, a film having a thickness of 5 μm or less, maintains a uniform film thickness. However, even if it is difficult to continuously produce the film itself, even if it can be formed into a film, the thin film is easily broken when laminated on the belt-like metal plate, and the yield is lowered. There is a problem that handling of the film becomes difficult. Accordingly, a thermoplastic resin film having a thickness of 5 μm or 4 μm is actually difficult to manufacture, and even if it can be manufactured, it becomes very expensive, and this film is laminated on a strip metal plate. Is more expensive than a strip-shaped metal plate laminated with a film having a thickness of 10 μm, and cannot be used for an inexpensive ordinary packaging container or the like.

  On the other hand, Patent Documents 1 to 6 describe an example of a method of coating a metal plate with a thermoplastic resin film by a method other than the laminating method. In Patent Document 1 and Patent Document 2, a paint (slurry paint) in which a fine powder of a thermoplastic resin is dispersed in an organic solvent is used as a repair paint for a metal can (the coating film is damaged by processing or coating before processing is omitted) It has been proposed that a part of the metal can (weld seam part) or a member thereof (part where the score of the can lid is engraved) or a metal can material is thickly applied as a paint to be subsequently applied to the applied part.

  In the method described in Patent Document 1 and Patent Document 2 described above, a paint in which a thermoplastic resin powder having a particle size of several μm to several tens of μm is dispersed in a solvent in advance is 50 ° C. or higher or 100 ° C. or higher. Used as a repair paint for welded seams of metal cans that have been heated to a high temperature and the score line of easy open can lids, or as an internal paint for two-piece cans that have been heated to 100 ° C or higher . However, the thickness of the coating film is very large, from several tens of μm to one hundred μm, and it is too thick as a coating material for coating uniformly on almost the entire surface of the belt-shaped metal plate, resulting in a very high cost.

  Patent Document 3 discloses a paint in which a thermosetting resin (curable material) is mixed with a thermoplastic resin (crystallizable polymer) having a particle diameter of 0.1 μm to 500 μm dispersed in a diluent. It is described that a coating film having a film thickness of 6 to 17 μm was obtained by coating a metal plate.

Furthermore, Patent Document 4 discloses that the weight of the coating film after drying is 0. 0 by coating a metal plate or the like with a paint in which a thermoplastic resin having an average primary particle size of 10 to 1000 nm is dispersed in an organic solvent. It is described that it is adjusted to 1 to 50 g / m ² , preferably 1 to 50 g / m ² , more preferably 3 to 20 g / m ² . Further, the same contents as in Patent Document 4 are also described in Patent Document 5 and Patent Document 6.

JP 54-144442 A Japanese Patent Laid-Open No. 55-11038 Japanese Patent Laid-Open No. 6-16953 International Publication No. 2005/019363 Pamphlet JP 2006-45542 A JP 2006-45543 A

  As described above, when the thickness of the thermoplastic resin film covering the surface of the belt-shaped metal plate used for the forming process needs to be 10 μm or more, it can be easily obtained by the film laminating method. However, the laminating method has a problem that even if the thermoplastic resin film has a film thickness of 5 μm or less (for example, 1 to 5 μm), a film having a film thickness of 10 μm or more has to be used. . Moreover, since the method described in Patent Document 1 and Patent Document 2 results in a coating film having a film thickness of several tens of μm to several tens of μm, it is used when uniformly coating a wide band-shaped metal plate. Can not.

  As a result of research by the inventors of the present application, the thermoplastic polyester resin mainly composed of polyethylene terephthalate is relatively corrosive such as carbonated beverages and highly acidic beverages when the film thickness is 1.0 to 5.0 μm. It has been found that the inner surface side coating of metal containers containing high contents and beer has insufficient corrosion resistance. That is, a test piece (6 cm × 6 cm) of an aluminum alloy plate provided with a 1.0 to 5.0 μm coating film made of polyethylene terephthalate resin, such as carbonated beverages, highly acidic beverages, and beer contained in a glass container. When immersed in a beverage and stored in a thermostatic chamber at 55 ° C. for 30 days in that state, the blister-like paint film was lifted on the entire surface of the aluminum alloy plate coated with polyethylene terephthalate resin. Many such blister-like coatings were lifted even when they were immersed in beer with relatively low corrosivity. However, a quaternary amorphous polyethylene naphthalate resin, that is, a polyethylene naphthalate resin in which the dicarboxylic acid component is composed of naphthalene dicarboxylic acid and terephthalic acid and the glycol component is composed of ethylene glycol and cyclohexanedimethanol is used. In the case of the coated aluminum alloy plate, no blister-like paint film lift occurred on the paint film surface even when the same test was conducted. Therefore, when a quaternary amorphous polyethylene naphthalate resin is used as the coating resin for the metal container, the film thickness of the inner coating of the metal container is about 1.0 to 5.0 μm. It has been found that even the thickness can sufficiently withstand corrosion caused by carbonated beverages, highly acidic beverages, beer and the like.

  Further, Patent Document 3 has a description that a film having a resin film mainly composed of a thermoplastic resin having a film thickness of 6 to 17 μm is obtained. This is a painting method in which a relatively small metal plate is hand-painted using a coating tool called a bar coater, which is used in the painting test method for investigating and confirming this, and is applied directly to long strips of metal strip that extend continuously It is impossible to do. In addition, in Patent Document 3, although a method for preparing a coating composition is described in considerable detail, the conditions for actually applying the obtained coating material, such as a brush coating method, a spraying method, a dipping method, Only the fact that the roll coding method can be used is described, and the specific coating conditions are not described at all.

  Patent Document 4, Patent Document 5 and Patent Document 6 disclose a method of obtaining a thermoplastic resin having an average primary particle diameter of 10 to 1000 nm, and dispersing the thermoplastic resin fine particles in an organic solvent to form a paint. The method is described in considerable detail. However, the specific examples of the means for painting the paint are only the hand painting method using a bar coater, which is a painting method for investigating and confirming the basic physical properties or performance of the paint. As an example of the coating method, it is exemplified that film thicknesses of 3 μm, 4 μm, 5 μm, and 10 μm were obtained. Examples of the coating method include a roll coating method, a spray coating method, a brush coating method, a spatula coating method, a dip coating method, an electrodeposition coating method, and an electrostatic coating method, but the actual coating conditions such as roll coding are exemplified. There is no mention of coating conditions by law.

  By the way, generally, a roll coating apparatus as shown in FIG. 3 and FIG. 4 is used for coating on the band-shaped metal plate. First, what is shown in FIG. 3 is a schematic view of a roll coating apparatus (roll coater) that applies a natural coat to the band-shaped metal plate 26. Reference numeral 21 in FIG. 3 denotes a paint pan, which stores the paint 22. Reference numeral 23 denotes a supply roll (pickup roll). The lower part is immersed in the paint 22 in the paint pan 21, and the paint 22 is pumped up from the paint pan 21. Reference numeral 24 denotes a coating roll (applicator roll), which faces the upper portion of the supply roll 23 through a very small gap, and rotates so that the outer peripheral surface moves in the same direction as the supply roll 23 on the facing side. To do. The coating roll 24 faces the backup roll 25 through a slight gap through which the strip-shaped metal plate 26 can pass on the side opposite to the supply roll 23 side, and on the side facing the backup roll 25. The outer peripheral surface rotates so as to move in the same direction as the coating roll 24. Therefore, the coating 22a pumped up by the supply roll 23 is applied to the band-shaped metal plate 26 that travels in the same direction as the movement direction of the painting roll 24 through the narrow gap between the painting roll 24 and the backup roll 25.

  Next, FIG. 4 is a schematic view of a roll coating apparatus (roll coater) that performs reverse coating on the belt-shaped metal plate 36. In FIG. 4, reference numeral 31 denotes a paint pan, and the paint 32 is stored in the paint pan 31. Reference numeral 33 denotes a supply roll (pickup roll). A lower portion of the supply roll 33 is immersed in the paint 32, and the supply roll 33 rotates to pump up the paint 32 in the paint pan 31. It has become. Reference numeral 34 denotes a coating roll. The coating roll 34 faces the upper portion of the supply roll 33 through a very small gap, and the outer peripheral surface thereof faces the same direction as the supply roll 33 on the facing side. Rotate to move. The coating roll 34 rotates so that the outer peripheral surface moves in the opposite direction to the backup roll 35 that faces the supply roll 33 on the side opposite to the supply roll 33. That is, the coating roll 34 and the backup roll 35 rotate so that their outer peripheral surfaces move in opposite directions on the facing side. Then, the coating material 32 a pumped up by the supply roll 33 is applied to the band-shaped metal plate 36 that travels in the gap between the coating roll 34 and the backup roll 35 in the direction opposite to the moving direction of the outer peripheral surface of the coating roll 34.

  In addition, although not shown in the figure, this type of coating apparatus is provided with a doctor roll, which is a scraping roll that is in contact with the supply roll 33 and scrapes excess paint at a position away from the coating roll 34. There is also.

  Now, when a normal solution type thermosetting paint is used for the coating apparatus as described above, the belt-shaped metal plate is run between the coating roll and the backup roll at a speed of 110 m / min to 180 m / min, The peripheral speed ratio of the coating roll is set to about 1.05 to 1.3 times the traveling speed of the belt-shaped metal plate, and the peripheral speed ratio of the supply roll to the traveling speed of the belt-shaped metal plate is set to about 0.1. When adjusted to about 4 to 0.8 times, the paint in the paint pan adheres to the periphery of the supply roll as the supply roll rotates, and the rotation speed of the supply roll is increased at the upper position. Since the coating material is transferred to the coating roll rotating at a speed of about 1.4 times, it is possible to perform coating with a uniform and thin film thickness from the coating roll onto the belt-shaped metal plate.

  However, according to experiments by the present inventors, a paint in which resin fine particles mainly composed of a quaternary amorphous polyethylene naphthalate resin as a subject of the present invention are dispersed in an organic solvent is thixotropic or thixotropic. Because it is extremely high in performance, the coating roll is almost entirely applied at the peripheral speed ratio of the supply roll 0.4 to 0.8 times the running speed of the belt-like metal plate, which incorporates the common general knowledge of conventional solution-type paints. Therefore, satisfactory coating could not be made on the strip-shaped metal plate. Furthermore, even if the peripheral speed ratio of the supply roll with respect to the traveling speed of the belt-shaped metal plate is increased by about 20%, an amount of paint necessary for satisfactory coating could not be supplied to the coating roll.

  Accordingly, an object of the present invention is to eliminate the above-mentioned problems of the prior art. Specifically, the average primary particle size of a resin mainly composed of a quaternary amorphous polyethylene naphthalate resin is 10 It is to provide a method in which a paint in which fine particles of ˜1000 nm are dispersed in an organic solvent is roll-coated on a strip metal plate continuously and in a uniform thin film. Furthermore, an object of the present invention is to provide a continuous and uniform thin film on a strip-shaped metal plate with a paint in which fine particles of resin mainly composed of such a quaternary amorphous polyethylene naphthalate resin are dispersed in an organic solvent. It is another object of the present invention to provide a method of forming a coating film having good adhesion and workability with a metal plate surface by a predetermined heat treatment.

  The primary particles of the resin described in this specification are particles that cannot be further dispersed, and are distinguished from secondary particles in which the primary particles are aggregated. As the average primary particle size decreases, the viscosity of the resulting suspension tends to increase, and the thickness of the resulting coating film decreases. On the other hand, when the average primary particle size is increased, the film thickness of the obtained coating film is increased. When the average primary particle diameter is less than 10 nm, the viscosity of the resulting suspension becomes too high, and the coating operation becomes difficult. On the other hand, when the average primary particle diameter exceeds 1000 nm, the film thickness of the coating film increases, and problems such as not becoming a continuous film are likely to occur when attempting to make a thin film. Therefore, the average primary particle diameter of the resin mainly composed of the quaternary amorphous polyethylene naphthalate resin to be used needs to be 10 to 1000 nm.

  As a result of repeated experiments and additional tests in order to achieve the above object, the present inventors have completed the present invention shown below. That is, the invention of claim 1 is mainly composed of a quaternary amorphous polyethylene naphthalate resin in which the dicarboxylic acid component is composed of naphthalenedicarboxylic acid and terephthalic acid, and the glycol component is composed of ethylene glycol and cyclohexanedimethanol. A resin component containing a resin component and having an average primary particle diameter of 10 to 1000 nm of the resin component dispersed in a solvent, and supplied to the resin paint stored in the paint pan By immersing and rotating the lower part of the roll, the resin coating is supplied to the coating roll facing the supply roll with a narrow gap above the supply roll, and the coating roll and the backup roll The resin coating is uniformly and thinly coated with the coating roll on a band-shaped metal plate that runs in a narrow gap between In the method, the coating roll is rotated in a direction opposite to the direction in which the belt-shaped metal plate travels, and the peripheral speed ratio of the coating roll to the traveling speed of the belt-shaped metal plate is 1.8 times to 2.3 times. The peripheral speed ratio of the supply roll with respect to the traveling speed of the belt-shaped metal plate is 1.2 to 1.4 times.

  A second aspect of the present invention is the method for coating a strip-shaped metal plate according to the first aspect of the present invention, wherein the travel speed of the strip-shaped metal plate is 120 m / min to 170 m / min.

  According to a third aspect of the present invention, in the first or second aspect of the invention, the belt-shaped metal plate coated with the resin paint in a thin film is passed through a heating furnace heated to a high temperature so that the surface of the belt-shaped metal plate is The solvent in the coating film of the formed resin coating is dried and vaporized, and at least most of the quaternary amorphous polyethylene naphthalate resin in the coating film is melted, and then the strip metal plate is It is a coating method of the strip-shaped metal plate characterized by making the said coating-film surface into a smooth state by cooling.

  According to the first aspect of the present invention, since the peripheral speed ratio of the supply roll to the traveling speed of the belt-shaped metal plate is increased by 1.2 to 1.4 times, a sufficient amount of paint for coating is supplied from the paint pan to the supply roll. Can be lifted up or pumped up and supplied to the coating roll. Therefore, a highly thixotropic paint in which very fine fine particles of a resin mainly composed of a quaternary amorphous polyethylene naphthalate resin are dispersed in a solvent has a thickness after drying of 1 μm to 5 μm. It is possible to continuously coat the belt-shaped metal plate so as to form a coating film having a thin film thickness and a uniform thickness. And the coating film obtained after giving a predetermined heat drying process with respect to the coating-film surface of the strip | belt-shaped metal plate after coating has a nonuniformity in a surface state in the width direction and longitudinal direction of a strip-shaped metal plate. Also, there is no flow, smoothness, no generation of bubbles, and the coating film on the metal plate does not have a large variation in film thickness.

  In addition, when the peripheral speed ratio of the supply roll with respect to the running speed of the belt-shaped metal plate is less than 1.2 times, the amount of the paint roll lifted by the supply roll is insufficient, and it becomes difficult to uniformly apply the paint roll. As a result, there is a portion where there is almost no coating film, and vertical streaky coating unevenness and flow eyes become conspicuous. Moreover, the target application amount cannot be ensured, and the test result of QTV (Quick Test Value) measurement, which is a measurement method for electrically testing the coating film performance, is deteriorated. On the other hand, when the peripheral speed ratio exceeds 1.4 times, the amount of paint lifted by the supply roll becomes too large, and the coating amount becomes difficult to be uniform, and the uniformity of the coating film is difficult to obtain. For this reason, vertical stripe unevenness occurs, and the QTV test results also deteriorate.

  In addition, the ratio of the peripheral speed of the coating roll to the traveling speed of the belt-shaped metal plate is increased by 1.8 times to 2.3 times, so that the coating roll smoothly receives the paint lifted from the paint pan by the supply roll, and the strip metal Since it can deliver continuously to a board, the coating film of uniform thickness can be continuously formed on a strip | belt-shaped metal plate.

  In addition, when the peripheral speed ratio of the coating roll with respect to the traveling speed of the belt-shaped metal plate is less than 1.8 times, the coating roll lifts the paint lifted by the supply roll, that is, the paint supplied by the supply roll to the coating roll. It cannot be received smoothly and delivered to the belt-shaped metal plate. As a result, the coating amount varies and a uniform film thickness cannot be secured.

  On the other hand, when the peripheral speed ratio of the coating roll with respect to the running speed of the belt-shaped metal plate exceeds 2.3 times, the scattering of the coating from the coating roll becomes intense, and the vicinity of the coating roll becomes dirty with the paint or after coating. Defects such as the occurrence of spotted patterns occur due to the paint scattered on the surface of the band-shaped metal plate.

  Further, according to the invention of claim 2, by setting the running speed of the belt-shaped metal plate to 120 m / min to 170 m / min, high-speed coating equivalent to the conventional solution type thermosetting paint can be performed. Even in that case, the surface of the resulting coating film does not show rough skin or flow, and a coating film having a uniform film thickness can be obtained.

  Further, according to the invention of claim 3, the coating film coated on the surface of the belt-like metal plate by passing the belt-like metal plate coated with the resin paint in a thin film shape through a heating furnace heated to a high temperature. The solvent in the coating film is dried and vaporized, and at least most of the quaternary amorphous polyethylene naphthalate resin in the coating film is melted, and then the band-shaped metal plate is rapidly cooled. The original amorphous polyethylene naphthalate resin layer is thinned and smoothed. Therefore, there is an advantage that the processing followability of the coating film on the surface of the metal plate is enhanced when forming a metal can, a can lid, or the like from the belt-shaped metal plate. The forming process is performed by, for example, punching and drawing a cup from the above-described band-shaped metal plate, and further performing a redrawing process and / or a redrawing and ironing process, so that a cap, a drawn can, a deep drawn can, Further, it is a process for forming a drawn iron can and the like, and further a process for further processing the formed deep drawn can or the drawn iron can to form a bottle-shaped can. Alternatively, a basic lid having the basic shape of a can lid is formed by punching and drawing from the above belt-shaped metal plate, and the basic lid is drawn, beaded, scored, punched at the opening, Can lid for bottom lid and easy-to-break can lid by performing two or more processes such as curling of the opening, pasting of the film-like lid for closing the opening, curling of the outer periphery of the lid, etc. This is a process for forming an easy-to-open can lid or the like. Further, according to the invention of claim 3, by appropriately selecting the combination of the resin constituting the film-like lid and the resin constituting the coating film, in other words, the resins having good adhesion can be obtained. By selecting, when the opening formed beforehand is sealed with a film-like lid, there is an advantage that the adhesion between the film-like lid and the opening is also increased.

  In addition, as a means of rapidly cooling after melting the thermoplastic resin of the coating film, an air cooling method that is a method of cooling the coating film by blowing air at a room temperature or air at a temperature lower than normal temperature to the surface of the band metal plate, A water cooling method in which the metal plate is allowed to pass through cold water to cool the coating film can be employed. For example, a combination of both methods, for example, the temperature of the strip metal plate is first cooled to about 130 ° C. to 120 ° C. by an air cooling method, and then the temperature of 45 ° C. or lower by passing the strip metal plate through cold water. After that, the band-shaped metal plate may be taken out of the water to dry the surface moisture. In addition, the temperature of the band-shaped metal plate when taking out from water is preferably 35 ° C. or higher in order to easily remove the moisture on the surface.

  The polyester copolymer which is a quaternary amorphous polyethylene naphthalate resin in the present invention uses 2,6-naphthalenedicarboxylic acid or a lower alkyl ester thereof and terephthalic acid or a lower alkyl ester thereof as a dicarboxylic acid component. In addition, ethylene glycol and 1,4-cyclohexanedimethanol can be used as the glycol component.

  In the production of the polyester copolymer, the first step in which the dicarboxylic acid component and the glycol component are transesterified, and the second polymer in which the low polymer of the reaction product obtained in the first step is further polycondensed. It is divided into processes.

  Explaining the first step, the reaction with the 2,6-naphthalenedicarboxylic acid component may be either ethylene glycol or 1,4-cyclohexanedimethanol, or a mixture of both. Also good. The terephthalic acid component may be reacted with either ethylene glycol or 1,4-cyclohexanedimethanol, or a mixture of both. Further, the transesterification reaction of the 2,6-naphthalenedicarboxylic acid component and the transesterification reaction of the terephthalic acid component may be performed separately. Alternatively, one transesterification reaction may be performed in advance, and the other transesterification reaction product may be mixed during or after the reaction.

  One preferred method is to combine a 2,6-naphthalenedicarboxylic acid component and ethylene glycol, and a terephthalic acid component in combination with 1,4-cyclohexadimethanol, and separately transesterify them to obtain a low transesterification weight. This is a method of obtaining a coalescence and subjecting it to the second step.

  The esterification reaction is achieved by reacting a 2,6-naphthalenedicarboxylic acid component and a terephthalic acid component with approximately 0.8 times mol or more, preferably 1 to 5 times mol of a glycol component. The transesterification synthesis method by the transesterification reaction in the first step can be performed according to a known method that can be carried out in the reaction vessel.

  The catalyst used in the transesterification reaction may be any catalyst that can be used for the synthesis of polyester such as polyethylene terephthalate. For example, Li, Na, K, Mg, Ca, Sr, Ba, Zn, Ge, Ti, Cr, Mn And salts of metal carboxylic acid alcoholate, oxide or acetate selected from the group consisting of Sb and Co. These may be used alone or in combination of two or more. The amount of catalyst used is about 10 to 1000 mmol (mmol)% with respect to the dicarboxylic acid component. The temperature suitable for the transesterification reaction is in the range of 150 to 260 ° C, preferably in the range of 220 to 240 ° C. The reaction time is a predetermined reaction rate or more, usually 80% or more, and may be carried out until there is almost no distillation of the lower alcohol produced as a result of the reaction.

  The second step will be described. In the second step, the low polymer product obtained in the first step is heated under reduced pressure to perform a polycondensation reaction. In the present invention, as the polycondensation catalyst, before and after the start of the second step, specifically, after the first step is substantially finished and at a time when the intrinsic viscosity (intrinsic viscosity) does not exceed 0.2 dl / g. For example, polycondensation reaction is performed by adding one or two or more of carboxylic acid, alcoholate, or oxide of a metal selected from the group consisting of Mn, Ge, Sn, and Ti in addition to Sb. The amount of the catalyst used may be about 10 to 1000 mmol (mmol)% with respect to the dicarboxylic acid component. At this time, various additives such as a light-resistant agent, a heat stabilizer, an antistatic agent, a light-shielding agent, and a pigment can be added singly or in combination as necessary.

  After the polycondensation catalyst is added, the process enters a second step in which a copolymer having a high degree of polymerization is obtained by a deglycolization reaction.

  In the polymerization reaction of the second step, the reaction temperature is gradually raised by heating the system as the reaction proceeds. That is, it is heated to about 270 to 310 ° C. at 200 to 250 ° C. at the start of the reaction. Further, the pressure in the reaction system is gradually reduced, and at the start of the reaction, the pressure is normally 1.3 kPa or less, preferably 0.13 kPa or less at normal pressure. Furthermore, the time required for the polymerization reaction by this dissolution method is determined by the intrinsic viscosity of the product obtained. However, if it is too long, it is economically disadvantageous and the thermal decomposition reaction proceeds simultaneously. Therefore, the reaction is carried out for 0.5 to 5 hours, preferably 1 to 4 hours.

  When the polymerization is completed, the polymer of the polyester copolymer is discharged from the reaction vessel pressurized with nitrogen gas, cooled, cut, and then arranged in a desired shape. Subsequently, the polyethylene naphthalate resin, which is a polyester copolymer, is dried under a flow of air or an inert gas or under reduced pressure. The drying conditions such as the drying temperature and drying time, the drying method, the drying equipment, etc. can be appropriately selected from those used for drying thermoplastic polyesters.

  Next, embodiments of the present invention will be described. FIG. 1 is a perspective view showing the main part of a roll coating apparatus for carrying out the coating method of the present invention, and FIG. 2 shows the relationship between each roll of the roll coating apparatus shown in FIG. It is the schematic (schematic diagram of the state seen from the back side of Drawing 1). 1 and 2, reference numeral 1 denotes a paint pan, and the paint 2 is stored in the paint pan 1. Reference numeral 3 denotes a supply roll (or a pickup roll). The supply roll 3 has a part of its lower part immersed in the paint 2 of the paint pan 1, and the rotational force in the paint pan 1 The coating material 2 is pumped up and supplied to the coating roll (or applicator roll) 4 facing with a narrow gap at the upper position. Reference numeral 5 denotes a backup roll (or support roll), which faces the coating roll 4 with a slight gap through which the belt-like metal plate 6 can pass. The supply roll 3, the coating roll 4 and the backup roll 5 rotate in the directions of the arrows in FIGS. 1 and 2, respectively, and the strip metal plate 6 moves in the direction of the arrows. Note that reference numeral 2 ′ in FIG. 2 indicates the paint pumped up by the supply roll 3. In this embodiment, a metal roll whose outer surface is a metal surface is used as the supply roll 3, a rubber roll whose outer surface is coated with butyl rubber having a hardness of 40 is used as the coating roll 4, and a backup roll 5. A metal roll having a metal surface on the outer surface was used.

  Reference numeral 7 denotes a DC motor, which rotates the supply roll 3 about its axis. Reference numeral 8 denotes another DC motor, and the DC motor 8 rotates the coating roll 4 around its axis. In addition, a variable speed volume knob is provided for adjusting the rotational speed of each of the motors 7 and 8 and the rolls 3 and 4.

  Reference numeral 9 indicates a knob for adjusting the nip pressure between the supply roll 3 and the coating roll 4, and reference numeral 10 indicates a nip pressure between the backup roll 5 and the coating roll 4. In addition, reference numeral 11 denotes a stepping motor. In order to adjust the nip pressure between the supply roll 3 and the coating roll 4, the operation is performed by the operation of the knob 9 described above, and the supply roll 3 is moved to the coating roll 4. It is comprised so that it may move in the direction which approaches or separates from the side. Reference numeral 12 denotes a harmonic drive, which is operated by the operation of the knob 10 to adjust and drive the nip pressure between the backup roll 5 and the coating roll 4, and the coating roll 4 and the supply roll 3 are connected to the backup roll 5. It is comprised so that it may move in the direction which approaches or separates from the side.

  Further, reference numeral 17 denotes a speed variable volume that variably adjusts the rotational speed of the supply roll 3, and reference numeral 18 denotes a speed variable volume that variably adjusts the rotational speed of the coating roll 4.

[Examples and Comparative Examples]
Next, the coating method of this invention is demonstrated with an Example and a comparative example. The present invention is not limited to these. Moreover, the intrinsic viscosity of the thermoplastic resin used in the following Example and the comparative example, the composition ratio of the resin, and the average primary particle diameter of the resin were measured by the following method.

[Measurement of intrinsic viscosity (or intrinsic viscosity) of thermoplastic resin used for coating]
In a mixed solution of phenol: tetrachloroethane = 60: 40 (weight ratio), a thermoplastic resin (polyethylene naphthalate resin) used for coating is dissolved, and the intrinsic viscosity of this solution is determined by Sun Electronics Co., Ltd. , Using an automatic viscometer (AVL-6C).
Fine particles of thermoplastic resin (polyethylene naphthalate resin) dispersed in an organic solvent were hydrolyzed in a basic solution. The components of 2,6-naphthalenedicarboxylic acid / terephthalic acid and 1,4-cyclohexanedimethanol / ethylene glycol were quantified by chromatography, and the composition ratio was determined as follows. 2,6-naphthalenedicarboxylic acid (2,6NDCA) 85 mol% / terephthalic acid (TPA) 15 mol%, ethylene glycol (EG) 60 mol% / 1,4-cyclohexanedimethanol (1,4-CHDM) 40 mol%.

  The morphology and size of the thermoplastic resin particles used for coating were measured with a scanning electron microscope (JSM-639OLA, manufactured by JEOL Ltd.). The measurement was performed using a measuring device (LB-550, manufactured by Horiba, Ltd.). These lead to an average primary particle size.

Prepare a coil of 3004H191 aluminum alloy plate with a thickness of 0.300 mm, a width of 956 mm, and a length of 3000 m (having phosphoric acid chromate treatment on both sides). While running the aluminum alloy plate at a speed of / min, the following coating material is applied on one surface under the following conditions with the coating apparatus shown in FIG. 1, and the target film thickness after drying becomes 1.5 μm. After coating, the highest temperature zone is set to about 266 ° C., and the lowest temperature zone is passed through an oven having a cooling zone that blows air at 30 ° C. After drying and melting, the coating was quenched to smooth the coating.
・ Diameter of supply roll ・ ・ ・ ・ ・ ・ 250mm
・ Diameter of painting roll ・ ・ ・ ・ ・ ・ 264mm
・ Nip pressure between supply roll and coating roll ・ ・ ・ ・ 441 Newton (N)
・ Rotation speed of supply rolls ・ ・ ・ 214rpm
・ Number of rotations of coating roll ... 333rpm
・ Peripheral speed of the supply roll: 168 m / min ・ Peripheral speed of the coating roll: 276 m / min ・ Ratio of the peripheral speed of the supply roll to the traveling speed of the aluminum alloy sheet: 1.40 times Peripheral speed ratio of coating roll to running speed of aluminum alloy plate ... 2.30 times used paint Thermoplastic resin ... Quaternary amorphous polyethylene terephthalate resin [resin component is dicarboxylic acid component 85 mol% of 2,6-naphthalenedicarboxylic acid (2,6NDCA), 15 mol% of terephthalic acid (TPA), glycol components are 60 mol% of ethylene glycol (EG) and 40 mol% of 1,4-cyclohexanedimethanol (1,4-CHDM) The intrinsic viscosity (IV) is 0.62 dl / g, the glass transition point (Tg) is 110 ° C., and there is no melting point (amorphous)
Primary average particle diameter of thermoplastic resin: about 300 nm (100-500 nm)
Ratio of resin solids in paint ... 10% by weight
Solvent used: Mixture of 60% by weight of dimethylacetamide (DMAC) and 30% by weight of ethyl alcohol

The coating material having the above composition was applied by the above method and then dried. The surface state of the obtained coating film was visually evaluated and a test piece (3 cm × 3 cm = 9 cm ² ) 3 cm long and 3 cm wide was cut out from the coated metal plate, and QTV (Quick) was applied to the test piece by the following method. Test Value) measurement was performed. The number of measurements is five (the same applies to the following Examples 2 to 6 and Comparative Examples 1 to 6).

  First, a circular iron plate is accommodated in the center of a plastic container having a through-hole at the bottom, and an electric current body connected to the lower surface of the iron plate is protruded from the through-hole of the container bottom wall to the outer side of the bottom wall, Further, prepare one electrode terminal extending to a position near the side wall of the container (the gap between the through hole at the bottom of the container and the current-carrying member is sealed with a sealing material), and an iron plate on the iron plate of this container After placing a sponge with substantially the same diameter as that of the electrode, an electrolysis in which a small amount of surfactant (for example, Rapisol A-80 from Nippon Oil & Fats Co., Ltd.) was added to 1% saline in this container. After injecting the liquid to about half the height of the sponge, place a coated metal plate test piece (3cm x 3cm) with the coating surface facing the sponge, and lightly press it against the sponge surface. An electric current consisting of an ammeter and two electrodes After connecting the test piece with the alligator clip connected to the electrode terminal near the side wall of the container with the alligator (mouth) clip connected to one electrode of the measuring instrument (QTV measuring device) and the other electrode Apply a voltage of 6V between the electrodes for 3 seconds, and measure the value of the flowing current. If there is no defect in the coating film, almost no current flows (less energization amount). On the other hand, if there is a defect such as discontinuity of the coating film, a large amount of current flows (energization amount increases). In this QTV measurement, even when the number of measurements was one, even if the energization amount exceeded 1 mA, it was determined to be unacceptable. The results are shown in Table 1 (QTV measurement values indicate the upper and lower limit values of five measurement values).

The conditions of the coating apparatus and the paint are exactly the same as in Example 1 except that the traveling speed of the aluminum alloy plate was 150 m / min, the rotation speed of the supply roll was 229 rpm, and the rotation speed of the coating roll was 380 rpm. Coating was performed under the same conditions, and a coating film was formed under the same heating and cooling conditions. The coating film performance test was also conducted in the same manner as in Example 1.
・ Rotation speed of supply roll ・ ・ ・ ・ ・ ・ 229rpm
・ Rotating speed of painting roll ・ ・ ・ ・ 380rpm
・ Peripheral speed of supply roll ・ ・ ・ ・ 180m / min ・ Peripheral speed of coating roll ・ ・ ・ ・ ・ ・ 315m / min ・ Ratio of feed roll to speed of aluminum alloy plate ・ ・ ・ 1.20 Double: Ratio of peripheral speed of coating roll to running speed of aluminum alloy plate ... 2.10 times The surface state of the obtained coating film was visually evaluated and QTV was measured. The results are shown in Table 1.

The coating was performed under the same conditions as in Example 2 except that the running speed of the aluminum alloy plate was 170 m / min, the rotation speed of the supply roll was 260 rpm, and the rotation speed of the coating roll was 379 rpm. The coated aluminum alloy plate was passed through an oven and heated and cooled to form a coating film. The coating film performance test was also conducted in the same manner as in Example 2.
・ Rotation speed of supply roll ・ ・ ・ ・ ・ ・ 260rpm
・ Rotating speed of coating roll ・ ・ ・ ・ ・ ・ 379rpm
・ Peripheral speed of supply roll ・ ・ ・ ・ ・ ・ 204m / min ・ Peripheral speed of coating roll ・ ・ ・ ・ ・ ・ 314m / min ・ Ratio of feed roll peripheral speed to aluminum alloy plate running speed ・ ・ ・ 1.20 The peripheral speed ratio of the coating roll to the traveling speed of the double aluminum alloy plate: 1.85 times The surface condition of the obtained coating film was visually evaluated and the QTV measurement was performed on the test piece. The results are shown in Table 1.

Except that the rotation speed of the coating roll was set to 389 rpm, coating was performed under the same conditions as in Example 3, and a coating film was formed under the same heating and cooling conditions. The coating film performance test was also conducted in the same manner as in Example 3.
・ Rotation speed of supply roll ・ ・ ・ ・ ・ ・ ・ 260rpm
・ Rotation speed of painting roll ・ ・ ・ ・ ・ ・ 389rpm
・ Peripheral speed of supply roll ・ ・ ・ 204m / min ・ Peripheral speed of coating roll ・ ・ ・ ・ 322m / min ・ Ratio of peripheral speed of supply roll to running speed of aluminum alloy sheet ・ ・ ・ 1 .20 times the peripheral speed ratio of the coating roll to the running speed of the aluminum alloy plate: 1.89 times The surface condition of the obtained coating film was visually evaluated and QTV measurement was performed on the test piece. The results are shown in Table 1.

Except that the rotation speed of the supply roll was 281 rpm, coating was performed under exactly the same conditions as in Example 4, and a coating film was formed under the same heating and cooling conditions. The coating film performance test was also conducted in the same manner as in Example 4.
・ Rotation speed of supply roll ・ ・ ・ ・ ・ ・ 281rpm
・ Rotation speed of painting roll ・ ・ ・ ・ ・ ・ 389rpm
・ Peripheral speed of supply roll ・ ・ ・ ・ ・ 221m / min ・ Peripheral speed of coating roll ・ ・ ・ ・ 322m / min ・ Ratio of feed roll to speed of aluminum alloy plate ・ ・ ・ 1 .30 times the peripheral speed ratio of the coating roll to the running speed of the aluminum alloy plate: 1.89 times The surface condition of the obtained coating film was visually evaluated and QTV measurement was performed on the test piece. The results are shown in Table 1.

The conditions of the coating apparatus and the paint conditions other than that the coating roll was changed to a roll having a diameter of 268 mm were exactly the same as in Example 5, and the coating film drying and cooling conditions were also in Example 5. A coating film was formed in the same manner. The coating film performance test was also conducted in the same manner as in Example 5.
・ Rotation speed of supply roll ・ ・ ・ ・ ・ ・ 281rpm
・ Rotation speed of painting roll ・ ・ ・ ・ ・ ・ 389rpm
・ Peripheral speed of supply roll ・ ・ ・ ・ 221m / min ・ Peripheral speed of coating roll ・ ・ ・ ・ 327m / min ・ Ratio of supply roll to speed of aluminum alloy plate ・ ・ ・ 1.30 The peripheral speed ratio of the coating roll to the traveling speed of the double aluminum alloy plate: 1.92 times The surface state of the obtained coating film was visually evaluated and QTV measurement was performed on the test piece. The results are shown in Table 1.

Comparative Example 1

Except that the rotation speed of the supply roll was set to 138 rpm and the rotation speed of the coating roll was set to 260 rpm, the conditions of the coating apparatus and the coating conditions were the same as those in Example 1, and the coating film was applied under the same heating and cooling conditions. Formed. The coating film performance test was also conducted in the same manner as in Example 1.
・ Rotation speed of supply roll ・ ・ ・ ・ ・ ・ ・ 138rpm
・ Number of rotation of painting roll ・ ・ ・ ・ ・ ・ ・ 260rpm
・ Peripheral speed of supply roll ・ ・ ・ 108m / min ・ Peripheral speed of coating roll ・ ・ ・ ・ ・ ・ ・ 216m / min ・ Ratio of supply roll to speed of aluminum alloy plate ・ ・ ・ 0 .90 times-Peripheral speed ratio of coating roll to running speed of aluminum alloy plate: 1.80 times The surface condition of the obtained coating film was visually evaluated and QTV measurement was performed on the test piece. The results are shown in Table 1.

Comparative Example 2

The coating apparatus conditions and coating conditions were the same as those in Comparative Example 1 except that the aluminum alloy plate travel speed was 150 m / min, the supply roll rotation speed was 286 rpm, and the coating roll rotation speed was 344 rpm. A film was formed under the same heating and cooling conditions. The coating film performance test was also performed in the same manner as in Comparative Example 1.
-Number of rotations of supply roll ... 286 rpm
・ Rotating speed of painting roll ・ ・ ・ ・ 344rpm
・ Peripheral speed of supply roll ・ ・ ・ 225m / min ・ Peripheral speed of coating roll ・ ・ ・ ・ ・ ・ ・ 285m / min ・ Ratio of supply roll to speed of aluminum alloy plate ・ ・ ・ 1 .Times.50: Peripheral speed ratio of coating roll to running speed of aluminum alloy plate: 1.90 times The surface condition of the obtained coating film was visually evaluated and QTV measurement was performed on the test piece. The results are shown in Table 1.

Comparative Example 3

The conditions of the coating apparatus and the coating conditions except that the traveling speed of the aluminum alloy plate was 170 m / min, the rotation speed of the supply roll was 152 rpm, and the rotation speed of the coating roll were 266 rpm were applied under exactly the same conditions as in Comparative Example 1. Furthermore, a coating film was formed under the same heating and cooling conditions. The coating film performance test was also performed in the same manner as in Comparative Example 1.
・ Rotation speed of supply roll ・ ・ ・ ・ ・ ・ 152rpm
・ Rotating speed of painting roll ・ ・ ・ ・ ・ ・ 266rpm
・ Peripheral speed of supply roll ・ ・ ・ ・ 119m / min ・ Peripheral speed of coating roll ・ ・ ・ ・ 221m / min ・ Ratio of supply roll to speed of aluminum alloy plate ・ ・ ・ 0.70 Double: Ratio of peripheral speed of coating roll to running speed of aluminum alloy plate: 1,30 times The surface condition of the obtained coating film was visually evaluated and QTV measurement was performed on the test piece. The results are shown in Table 1.

Comparative Example 4

Except that the rotation speed of the supply roll was set to 216 rpm and the rotation speed of the coating roll was set to 328 rpm, the conditions of the coating apparatus and the paint conditions were applied under exactly the same conditions as in Comparative Example 3, and the coating film was applied under the same heating and cooling conditions. Formed. The coating film performance test was also performed in the same manner as in Comparative Example 3.
・ Rotation speed of supply roll ・ ・ ・ ・ ・ ・ 216rpm
・ Rotating speed of painting roll ・ ・ ・ ・ ・ ・ 328rpm
・ Peripheral speed of supply roll ・ ・ ・ ・ ・ ・ 170m / min ・ Peripheral speed of coating roll ・ ・ ・ ・ 272m / min ・ Ratio of peripheral speed of supply roll to running speed of aluminum alloy sheet ・ ・ ・ 1.00 The peripheral speed ratio of the coating roll with respect to the traveling speed of the double aluminum alloy plate: 1.60 times The surface condition of the obtained coating film was visually evaluated and QTV measurement was performed on the test piece. The results are shown in Table 1.

Comparative Example 5

The coating apparatus conditions and the coating material conditions were the same as in Comparative Example 4 except that the rotation speed of the coating roll was 389 rpm, and a coating film was formed under the same heating and cooling conditions. The coating film performance test was also performed in the same manner as in Comparative Example 4.
・ Rotation speed of supply roll ・ ・ ・ ・ ・ ・ 216rpm
・ Rotation speed of painting roll ・ ・ ・ ・ ・ ・ 389rpm
・ Peripheral speed of supply roll ・ ・ ・ ・ ・ ・ 170m / min ・ Peripheral speed of coating roll ・ ・ ・ ・ 322m / min ・ Ratio of peripheral speed of supply roll to running speed of aluminum alloy sheet ・ ・ ・ 1.00 The peripheral speed ratio of the coating roll to the running speed of the double aluminum alloy plate: 1.89 times The surface condition of the obtained coating film was visually evaluated and the test piece was subjected to QTV measurement. The results are shown in Table 1.

Comparative Example 6

The conditions of the coating apparatus and the coating conditions except that the rotation number of the supply roll was 238 rpm were applied under exactly the same conditions as in Comparative Example 5, and a coating film was formed under the same heating and cooling conditions. The coating film performance test was also performed in the same manner as in Comparative Example 5.
・ Rotation speed of supply roll ・ ・ ・ ・ ・ ・ 238rpm
・ Rotation speed of painting roll ・ ・ ・ ・ ・ ・ 389rpm
・ Peripheral speed of supply roll ・ ・ ・ ・ 187m / min ・ Peripheral speed of coating roll ・ ・ ・ ・ 322m / min ・ Ratio of peripheral speed of supply roll to running speed of aluminum alloy sheet ・ ・ ・ 1.10. The peripheral speed ratio of the coating roll to the running speed of the double aluminum alloy plate: 1.89 times The surface condition of the obtained coating film was visually evaluated and the test piece was subjected to QTV measurement. The results are shown in Table 1.

  In the present example and the comparative example, the peripheral speed ratio of the coating roll to the traveling speed of the belt-shaped metal plate was only implemented up to 2.30. This is because stable production of the paint cannot be achieved. The reason why the traveling speed of the metal plate is set to 170 m / min is because of the capability of the used coating apparatus.

  From the results of Examples 1 to 6 and Comparative Examples 1 to 6 shown in Table 1, the conditions under which the coating material rich in thixotropic property on the strip metal plate can be applied thinly and uniformly on the surface of the strip metal plate are as follows. The peripheral speed ratio of the supply roll is in the range of 1.20 to 1.40, and the peripheral speed ratio of the coating roll to the traveling speed of the strip metal plate is in the range of 1.80 to 2.30. I can read (understand) that it is time.

  That is, even if the peripheral speed ratio of the coating roll with respect to the traveling speed of the belt-shaped metal plate is within the range of 1.80 to 1.90, the peripheral speed ratio of the supply roll to the traveling speed of the belt-shaped metal plate is 1.20. If it is out of the range of 1.40 (for example, Comparative Example 1, Comparative Example 2, Comparative Example 5, Comparative Example 6), the coating film has uneven thickness, or the coating film is too thin, resulting in corrosion resistance. Becomes worse (the energization value becomes larger). On the other hand, in Examples 1 to 6, no unevenness of the surface state of the coating film was observed, and the flat plate energization value (mA) was small in the range of 0.1 to 0.8 mA. It can be understood that the corrosion resistance is improved when a beverage, food, or chemical container is manufactured using a metal plate provided with a film.

  As described above, the coating method of the present invention is applied to a resin coating in which resin fine particles having an average primary particle diameter of 10 to 1000 nm mainly composed of a quaternary amorphous polyethylene naphthalate resin are dispersed in a solvent. The coating roll is supplied to a coating roll facing the supply roll with a narrow gap at a position above the supply roll by immersing and rotating the lower portion of the supply roll. The coating material is uniformly and thinly coated on the strip-shaped metal plate that travels in a narrow gap between the coating roll and the backup roll, and the circumference of the supply roll with respect to the traveling speed of the strip-shaped metal plate is The supply roll is rotated at a high speed so that the speed ratio is 1.2 to 1.4 times, and the paint composed of the amorphous polyester resin particles is pumped up. The amorphous polyethylene naphthalate resin particles dispersed in the solvent have properties similar to liquids, and the supply roll sufficiently pumps up the amount of paint necessary for coating (around the supply roll). It is attached to the water and pumped up). The coating roll is arranged so as to face the supply roll through a narrow gap, and the coating roll is rotated so that its outer peripheral surface travels in a direction opposite to the traveling direction of the belt-shaped metal plate. At the same time, the peripheral speed ratio of the coating roll with respect to the traveling speed of the belt-shaped metal plate is set to 1.8 to 2.3 times (the peripheral speed of the coating roll is higher than the peripheral speed of the supply roll). The pumped paint is transferred to the coating roll facing through a narrow gap and attached to the strip metal plate running in the opposite direction to the rotation direction of the coating roll so as to have a thin and uniform thickness. Then, when the coating film is dried by heating and then cooled, the coating film thinly coated on the surface of the belt-shaped metal plate has a uniform and smooth surface. That is, according to the coating method of the present invention, a coating film having a thin film thickness and a smooth surface can be obtained on the surface of the belt-shaped metal plate.

  In the above embodiment, the case where the resin solid content of the paint is a thermoplastic resin (quaternary amorphous polyethylene naphthalate resin) has been described, but in the present invention, the thermoplastic resin particles include a curing agent, Additives such as thermosetting resins may be added. That is, it may be preferable to add a thermosetting resin or the like from the viewpoint of improving the adhesion of the coating film, the scratch resistance of the coating film, the fracture resistance of the coating film, and the like. Examples of preferable thermosetting resins include unsaturated polyester resins, acrylic resins, epoxy resins, urethane resins, melamine resins, phenol resins, urea resins and the like, and these can be added alone or in admixture of two or more. As addition amount of a thermosetting resin, 1-20 weight part is preferable with respect to 100 weight part of thermoplastic resin particles, and 5-15 weight part is more preferable.

It is a perspective view which shows the principal part of the roll coating apparatus in this invention. It is a figure which shows typically the relationship between each roll and strip | belt-shaped metal plate of the roll coating apparatus in this invention. It is a figure which shows typically the roll coater which applies a natural coat to a strip | belt-shaped metal plate. It is a figure which shows typically the roll coater which reverse-coats a strip | belt-shaped metal plate.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Paint pan, 2 ... Paint, 3 ... Supply roll, 4 ... Paint roll, 5 ... Backup roll, 6 ... Strip | belt-shaped metal plate.

Claims (3)

The dicarboxylic acid component is composed of naphthalenedicarboxylic acid and terephthalic acid, and the glycol component contains a resin component mainly composed of a quaternary amorphous polyethylene naphthalate resin composed of ethylene glycol and cyclohexanedimethanol, and Using a resin paint in which particles having an average primary particle diameter of 10 to 1000 nm of the resin component are dispersed in a solvent, the lower part of the supply roll is immersed in the resin paint stored in the paint pan and rotated. The resin paint is supplied to the coating roll facing the supply roll with a narrow gap above the supply roll, and travels through the narrow gap between the coating roll and the backup roll. In the method of coating the resin paint uniformly and in the form of a thin film on the belt-shaped metal plate with the coating roll,
The coating roll is rotated in a direction opposite to the direction in which the belt-shaped metal plate travels, and the peripheral speed ratio of the coating roll with respect to the traveling speed of the belt-shaped metal plate is 1.8 times to 2.3 times.
A method for coating a belt-shaped metal plate, characterized in that a peripheral speed ratio of the supply roll to a traveling speed of the belt-shaped metal plate is 1.2 to 1.4 times.   The strip metal plate coating method according to claim 1, wherein a travel speed of the belt metal plate is 120 m / min to 170 m / min.   The belt-shaped metal plate coated with the resin paint in a thin film is passed through a heating furnace heated to a high temperature to dry and evaporate the solvent in the coating film of the resin paint formed on the surface of the belt-shaped metal plate. And at least most of the quaternary amorphous polyethylene naphthalate resin in the coating film is melted, and then the surface of the coating film is made smooth by cooling the strip metal plate. The method for coating a strip-shaped metal plate according to claim 1 or 2, characterized in that:

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