Title of Invention

"METHOD OF OBTAINING A POLYESTER RESIN COATED METAL SHEET"

Abstract

[ PROBLEM] To provide a metal sheet covered with polyester resin in which decorative design is given to polyester resin film with high strength and excellent formability by embossing the polyester film. [MEAS FOR SOLVING THE PROBLEM] A metal sheet is covered with nonoriented polyester resin layer or polyester resin layer comprised of resin with low crystallinity and crystalline polyester resin, in which uneven touch is given to the surface of the above-mentioned resin layer by embossing the surface thereof.

Full Text

The present invention relates to a method of obtaining a polyester resin coated metal sheet. [RELATIONAL ART] Heretofore, metal sheet coated with soft plasticized polyvinyl chloride as well as polyolefin mainly composed of polyethylene or polypropylene, thermoplastic acrylic resin, resin including fluorine, or biaxially stretched polyester film and others is used for cases or internal parts for office apparatus such as electric tool/electronic apparatus, acoustic apparatus, office apparatus such as copying machine /printer and others. Polvinyl chloride resin is excellent in economical efficiency, embossin ability, formability and others. However, since it includesgenerally abundant plasticizer and film thereof is soft, there are problems such as bleeding of plasticizer onto the surface with the passage of long period of time and environmental deterioration caused by hydrogen chloride generated when it is burnt. Therefore, polyolef in resin including polyethylene or polypropylene as main component is investigated as a substitutional resin for polyvinyl chloride. Film made of each of these resins alone has excellent embossing ability, chemical resistance and others, and is harder than plasticized polyvinyl chloride resin. However, when the polyolefin resin is laminated with metal sheet and formed, a part formed thereof is made white so that decorative design is marred. Further, there is a case where rubber component is mixed in polyolef in resin in order to prevent the whitening phenomenon. In this case, produced film is as soft at the same level as that of platicized polyvinyl chloride. Further, thermoplastic acrylic resin and fluoride resin have peculiar characteristic, respectively, however, films of those resins are as soft at the same level as platicized polyvinyl chloride. In recent years, biaxially stretched polyester film including polyethylene terephthalate (PET) as main component deserves attention as substance which is laminated with metal sheet. As biaxially stretched polyester film has high hardness, it is excellent in destruction resistance of film (generation of breakage, crack and others) . However, the adhesion of PET film with metal, sheet is apt. to be poor in formed part of the laminate since strength of the film is too high. Further there is a disadvantage, that decorative design cannot be given to biaxially stretched polyester film by forming uneven patterns by embossing work. [PROBLEM WHICH INVENTION IS TO SOLVE] As above-mentioned, metal sheet coated with various resins including plasticized polyvinyl chloride is used for cases or internal parts for electric tool/electronic apparatus, acoustic apparatus, office apparatus such as copying machine/printer and others. However, since in either case, there are various disadvantages, metal sheet coated with resin which has high strength and excellent formability, and to which decorative design can be given by embossing is desired. The present invention aims at overcoming disadvantages of conventional resin coated metal sheet, and provides metal sheet coated with polyester resin in which decorative design is given to polyester resin film having high strength and excellent formability by embossing. [MEANS FOR SOLVING THE PROBLEM] The present invention relates to a method of obtaining a polyester resin coated metal sheet said method comprising: (a) extruding polyester resin hot-melted directly on the metal sheet of the kind such as herein described (b) giving uneven patters on the extruded resin layer by means of an embossing roll when the extruded resin is in the hot-melted state, and (c) thereafter laminating the extruded-molded film with the metal sheet characterized in that the said polyester resin layer has a main component of crystallize polyester resin and is blended with a resin of low crystallization of 5 to 10 wt% wherein said crystalline polyester resin is crystalline copolymer polyester in which both component is substituted for polyethylene terephthalate, polybutyl terephthalate or for a part of their multivalent acid component or multivalent alcohol component. Metal sheet coated with polyester resin is characterized in that the metal sheet coated with polyester resin comprises nonoriented polyester resin layer having uneven patterns thereon. Metal sheet coated with polyester resin is characterized in that the polyester resin described is polyethylene terephthalate. Further, metal sheet coated with polyester resin is characterized in that the polyester resin described is polybutylene terephthalate. Further, metal sheet coated with polyester resin is characterized in that the polyester resin in is characterized in that the polyester resin described is crystalline copolymerized polyester in which a portion of polybasic acid component or polyhydric alcohol component of polyethylene terephthalate is substituted by other component. Metal sheet coated with polyester resin is characterized in that resin made of chips of waste polyethylene terephthalate is used for the polyestere resin described. Metal sheet coated with polyester resin is characterized in that the polyester resin described is composed of any two or more of polyethylene terephthalate, polybutylene terephthalate, crystalline copolymerized polyester in which a portion of polybasic acid component or polyhydric alcohol component of polyethylene terephthalate is substituted by other component, or resin made of chips of waste polyethylene terephthalate. Metal sheet coated with polyester resin is characterized in that the metal sheet coated with polyester resin has layer of resin having uneven patterns thereon, wherein the polyester resin comprises nonoriented polyester resin as main component and 5 ~ 40 % by weight resin with low crystallinity. Metal sheet coated with polyester resin is characterized in that the crystalline polyester resin described is any one of polyethylene terephthalate, polybutylene terephthalate, or crystalline copolymerized polyester in which a portion of polybasic acid component or polyhydric alcohol component of polyethylene terephthalate or polybutylene terephthalate is substituted by other component. Metal sheet coated with polyester resin is characterized in that the crystalline polyester resin described is resin made of chips of waster polyethylene terephthalate. Further, metal sheet coated with polyester resin is characterized in that the crystalline polyester resin described is composed of any two or more of polyethylene terephthalate, polybutylene terephthalate, crystalline copolymerized polyester in which a portion of polybasic acid component or polyhydric alcohol component of polyethylene terephthalate is substituted by other component, or resin made of chips of waste polyethylene terephthalate. Metal sheet coated with polyester resin described is characterized in that the polyester resin with low crystallinity described is any one of copolymerized polyester in which a portion of polybasic acid component or polyhydric alcohol component of polyethylene terephthalate or polybutylene terephthalate is substituted by other component, polycarbonate, or polyolefin. [FORM OF WORKING OF THE INVENTION] The present invention was aimed at finding a nonpolyvinyl chloride resin which does not generate injurious gas such as hydrogen chloride when being incinerated so as to be environment-friendly, and has high hardness as well as excellent formability and embossing ability. As a result of diligent study, it was found that nonoriented polyester resin is most excellent Accordingly, it is essential that polyester resin with which metal sheet is coated is nonoriented resin in the present invention. Polyester resin, which is film-formed with monoaxially or biaxially stretching, is tough, and excellent in mechanical characteristic, chemical resistance, solvent resitance and others. However, decorative design cannot be given to the polyester resin film by forming objective uneven patterns by embossing. Further, stretched film is not desirable since it has so tough that the adhesion to metal sheet is poor in the formed portion. [0008] In the present invention, nonoriented polyester resin with which metal sheet is covered is polymer in which polybasic acid represented by terephthalic acid and polyhydric alcohol represented by ethylene glycol are condensation-polymerized. In the present invention, polyethylene terephthalate, polybutylene terephthalate, or one copolymerized polyester or mixture of two or more of them in which a portion of polybasic acid component or polyhydric alcohol component of polyethylene terephthalate or polybutylene terephthalate is substituted by other component, can be available. Further, mixture of two or more of these polyester resins can also be available. As polybasic acid other than terephthalic acid used in the copolymerized polyester resin, aromatic dicarboxylic acid such as isophthalic acid, orthophthalic acid or 1. 4 cyclohexanedioarboxylic acid or aliphatic dicarboxylic acid such as adipic acid, sebacic acid, or dodecanedione acid can be used. Further, as polyhydric alcohol other than ethylene glycol used in the copolymerized polyester resin, any one expressed by general formula HO-(CH 2 ) n-OH such as 1, 2 propione glycol, 1, 4 butanediol or others can be used. [0009] Further, in recent years, polyethylene terephthalate is extensively used as a container stock for various bevarage or seasoning. In this respect,on the other hand, waste polyethylene terephthalate container or the like collected is tried to be made into resin chip and to be reused as resin substance. Chips of waste polyethylene terephthalate collected can be used as polyester resin in the present invention. [oo10] Further, in the present invention, examination was made in detail about basic physical properties of polyester resin and characteristic of metal sheet covered with polyester resin. As a result, it was found which greatly controls characteristic of the metall sheet covered with resin. Crystallinity of polyester resin is generally evaluated by the methods using X ray, differential scanning calorimeter(DSC), density and others. The crystallinity is influenced by the condition of heat treatment and the temperature of resin,and the crystallinity of polyethylene terephthalate and polybutylene terephthalate which are crystalline resin reaches usually 30 to 50%. When the polyester resin is formed by copolymerization in the above-mentioned method, the crystallinity lowers depending on the kind or the compounding amount of polybasic acid or polyhydric alcohol, and in some cases, the resin with low crystallinity or noncrystalline resin can be obtained. Accordingly, it is different to precisely distinguish crystalline polyester resin from resin with low crystallinity or noncrystalline polyester resin. [0011] Accordingly, in the present invention, the resin, in which an exothermic peak caused by crystallization of resin and an endothermic peak caused by melting of resin are clearly shown in differential scanning calorimeter (DSC) as shown in Fig 1 and Fig 2, when the resin is hot-melted, then quenched and thereafter the temperature of resin is raised at 10 0C /min, and when resin is melted and then the temperature of resin is reduced to room temperature at 10 °C /min, is regarded as a crystalline polyester resin. And the resin, in which an exothermic peak caused by crystallization of resin and an endothermic peak caused by melting of resin are not shown in the same differential scanning calorimeter(DSC), as shown in Fig 3, is regarded as a resin with low crystallinity or noncrystalline resin. Hereupon, the exothermic peak temperature shown when raising temperature is generally referred to as the low temperature crystallization temperature (T C 1 ), and the endothermic peak temperature shown when reducing temperature from the condition of resin being melted is generally referred to as the high temperature crysta1lization. temperature (T-C—2 ) . [0012] When the polyester resin is measured by a differential scanning calorimeter(DSC), it is shown that the resin having the higher crystallinity of resin has, the lower low temperature crystallization temperature (T C 1 ) and the higher high temperature crystallization temperature (T c 2 ) . In case of polybutylene, the low temperature crystallization temperature (T C 1 ) is not clearly shown, however, the high temperature crystallization temperature (T C 2 ) is shown near 200 °C . On the other hand, in the resin with low crystallinity or noncrystalline resin, the endothermic peak caused by crystallization is not clearly shown. [0013] In the present invention, the influence of blending ratio of a crystalline polyester resin and a resin with low crystallinity or, noncrystalline resin on the properties of the metal sheet covered with resin was examined. As a result, it was found that the polyester resin mainly composed of crystalline polyester resin and including low crystallinity or noncrystalline resin has high hardness and is excellent in the impact-formability, the embossing ability, and the heat resistance of the embossment, and the crystalline polyester resin was desirably blended with 5 to 40% weight resin with low crystallinity or noncrystalline resin. When the blending ratio of the resin with low crystallinity or noncrysralline resin is less than 5% by weight, the effect of blending cannot be obtained. On the otherhand , it is undisirsbie that the blending ratio of it 'exceeds 40% by weight Since the heat resistance of the embossment lowers. Further, the crystalline polyester resin is the one having an it is more disirable that exothermic peak caused by crystallization of resin above glass transition temperature (Tg) , and less than 170 °C . [0014] Further, as a resin with low crystallinity or noncrystalline resin, the resin such as copolymerised polyester resin in which a portion of polybasic acid component or polyhydric alcohol component of polyethylene terephthalate or polybutylene terephthalate is substituted by other component, as well as polycarbonate, polyolefin elastomer, polyallylate, vinyl polymer, nylon or phenoxy resin, can be used in the present invention. In case of copolymerized polyester resin, the higher ratio of polybasic acid component or polyhydric alcohol component to be copolymerised produces a, resin with low crystallinity or noncrystallinr resin, in which an endothermic peak caused by crystallization of resin is not clearly shown in the measurement by differential scanning calorimeter (DSC) . [0015] In the present invention, the thickness of polyester resin with which a metal sheet is covered is not specially restricted, but determined for the purpose, preferably 20 to 300 µm in general. For some purpose, it is possible to color polyester resin by adding pigment, dye and others to it. [0016] As a metal sgeet use in the presentt invention, cold-rolled steel sheet, aluminium sheet, stainless steel sheet, copper plate, as well as and one of these metal sheets on which various plating or chemical treatment is given can be used. In some cases, a layer of primer or adhesive can be lain between the metal sheet and the polyester resin layer. Furthermore, a coloring layer can be provided as the upper layer or the lower layer of the polyester resin layer. [0017] In addtion, as a method of obtaining a metal sheet covered with polyester resin, a method in which a metal sheet is covered by extrudinq resin hot-melted directly on the metal sheet by means of an equipment such as extruder, thereafter uneven patterns are given on the extruded resin layer by means of an embossing roll when the extruded resin is in the state of being hot-melted, or another method in which a resin film is preformed by extrusion-molding resin hot-melted by means of an equipment such as extruder, thereafter the extrusion-molded film is laminated with the metal sheet, one available in the present invention and either of these two methods can be applied for the purpose. In case of the latter method, embossing forming can be made either on the preformed film before the film is laminated with the metal sheet, or on the preformed film after the film has been laminated with the metal sheet. [0018] Properties of the polyester resin and the characteristic of the metal sheet covered with polyester of the present invention were evaluated in the following way . (1) Properties of the resin Properties such as crystalline characteristics of the polyester resin and other resins used in the present invention were measured by a diffelential scanning calorimeter(DSC). When raising the temperature at 10 °C /min and when reducing temperature of the resin to room temperature at 10 °C /min after melting the resin, the point of inflection shown between 0 °C and 100 °C was regarded as the glass transition temperature (Tg), the exothermic peak temperature shown between 100 °C and 200 °C was regarded as the crystallization temperature (when raising temperature : T C 1 , when reducing temperature : T C 2 ) , and the endothermic peak temperature shown between 200 °C and 270 °C was regarded as the melting point (Tm). (2) Hardness of the polyester resin and the resin used in comparative examples Hardness of the polyester resin layer of the present invention was evaluated by means of a pencil hardness tester defined in JIS K 5401 and using pencils defined in JIS S 6006. The order of hardness marks is shown to be 9H, 8H...H, F, HB, 2B...6B from hardest side, wherein 9H indicates to be most hard, and 6B indicates to be most soft. (3) Evaluation of the embossing ability and evaluation of the heat resitance of embossment Evaluation of the embossing ability of the polyester resin layer of the present invention was made by heating the metal sheet covered with Dolvester resin to a temperature of between temperature-20 to- 20 • • lower than the melting point of the resin and the melting point of the resin and thereafter pressing the metal sheet covered with polyester resin with a grained embossing roll having unevnenness of average roughness R a 1 : 5 µm. Further, embossing was made the for polyvinyl chloride film at 200 to 220 °C , and for polyolefin film at 140 to 170 t ,respetively. used as comparative examples of the present invention. The standard of evaluation was defined as in the following, in which evaluation was made in three ranks by observation with naked eye. O: good, : slightly inferior, X : inferior Further, the heat resitance of embossment was evaluated in three ranks as in the following by keeping sample embossed in the above-mentioned way in an atmosphere of 120 °C for five days, thereafter measuring average roughness R a 2 . and obtaining a ratio of the retained average roughness. Ratio of the retained average roughness =Ra2/RalX 100 (%) O : Ratio of the retained average roughness 80 to 100% A : 50 to 80%, X : less than 50% (4) Evaluation of the impact-formability of the polyester resin and the resin used in comparative examples Impact-formability of the metal sheet covered with polyester resin of the present invention was tested by means of a du Pont impact tester difined in JIS K 5400 (the size of impacting portion: diameter l/2in, test load: 1kg, and falling height: 50cm). The evaluation was made in four ranks by observation with naked eye as in the following. ©: Crack of film cannot be found at all, O: Fine cracks are slightly found in some portion of film fine cracks are found fairly in some portion of film, X : Remarkable cracks are found in film. [0019] [EXAMPLES] Then, the present invention is explained in detail by examples. [0020] Examples 1 ~ 17 The metal sheets covered with polyester resins were maunufactured by heating electrogalvanized steel sheets with 0.5 min. thickness on which chromate treatment was made with treatment amount 20g/m 2 , Heat-laminating,the metal sheets with films of polyester resins shown in table 1 and 2, and thereafter giving unevenness to the films at temperature 20 °C lower than melting points (Tm) of the respective resins by means of an embossing roll (grain embossing having unevnenness of average roughness Ra — 5µm) . Results of the evaluation are shown in table 1 and 2 . [0021] [TABLE i] [0022] [TABLE 2] [0023] The metal sheets covered with polyester resins of Examples 1 ~ 17 of the present invention have high hardness and in so excellent in formability, as well as have uneven touch given by embossing and so has [0024] Comparative examples 1 ~ 1 0 The metal sheets covered with resins of comparative examples 1 ~ 3 were manufactured by applying a conventional adhesive with 5 µm dry film thickness to electrogalvanized steel sheets with 0.5 min. thickness on which chromate treatment was made with treatment amount 20g/m 2 , thereafter heating at 200 °C to harden the adhesive, and then immediately heat-laminating the metal sheets with resin films shown in Table. 3 through the applied adhesive on the metal sheets, and thereafter giving unevenness to the films by means of an embossing roll (grain embossing having average roughness of surface Ra — 5 µm, temperature: Comparative examples 1 and 2; 200 °C , comparative example 3; 145 °C ). Further, the metal sheets covered with resins of comparative examples 4 ~ 10 were manufactured by heating the same electrogalvanized steel sheets, and laminating the heated electrogalvanized steel sheets with films of polyester resins shown in tables 3 and 4, and thereafter giving unenvenness to the films at temperature 20 °C lower than melting points (Tm) of the respective resins by an embossing roll (grain embossing having average roughness of surface Ra = 5 µm) . Results of the evaluation are shown in tables 3 and 4 . [0025] [TABLE 3] [0026] F TSRT.F A 1 [Table 4] [0027] Comparative examples 1 and 2 are cases of steel sheets covered with polyvinyl chloride resin, wherein when the amount of plasticizer is small, polyvinyl chloride film has high hardness and so is excellent in embossing ability, however, inferior in impact-workability. On the othterhand. when the amount of plasticizer increases, it has good impact-formability good, however, it is softer. [0028] Comparative example 3 is examples of a steel sheet covered with polyolefin resin, wherein the embossing ability is good, however, the hardness of the film of polyolefin resin is softer as compared with the polyester resin film in the metal sheet covered with polyester resin of the present invention. [0029] Comparative examples 4 ~ 6 are examples of steel sheets covered with biaxially stretched polyester resin, wherein the biaxially stretched polyester resin film has high hardness, so it is remarkably inferior in the embossing ability. [0030] Comparative examples 7 and 8 are examples of laminates covered with films composed of resin with low crystallinity or noncrystalline resin alone, wherein the hardness of the film is high and so excellent in the embossing ability and impact-formability, however, remarkably inferior in the heat resitance of embossment. [0031] Comparative example 9 is an example of the laminate covered with a film composed of crystalline polyester resin and polyester resin with low crystallinity, wherein since the blending ratio of resin with low crystallinity is high, the film is remarkably inferior in heat resitance of embossment. [0032] Comparative example 10 is an example of the laminate covered with a film composed of crystalline polyester resin and noncrystalline resin, wherein since the blending ratio of polyester resin with low crystallinity is high, the film is remarkably inferior in heat resitance of embossment. [0033] [EFFECT OF INVENTION] According to the present invention, a metal sheet covered with polyester resin film having high hardness and so excellent in formablity, and having decorative design given by embossing forming can be obtained. [BRIEF DESCRIPTION OF THE DRAWINGS] [FIG. i] An example of measurement of diffelential scanning calorimeter (DSC) of a crystalline polyester resin. [FIG. 2] An another example of measurement of diffelential scanning calorimeter (DSC) of a crystalline polyester resin. [FTG. 3] An example of measurement of diffelential scanning calorimeter (DSC) of a resin with low crystallinity. Document in which chemical formula and others are mentioned Specification [TABLE 1] (Table Removed) Document IB rtiidi ctieeical foraula tod others tre Kntianed Specification CTABLE 2) (Table Removed) Document in which chemical formula and others are mentioned Specification [TABLE 3] (Table Removed) Document in which chemical formula and others are mentioned Specification [TABLE 4] (Table Removed) WE CLAIM: 1. Method of obtaining a polyester resin coated metal sheet said method comprising: (a) extruding polyester resin hot-melted directly on the metal sheet of the kind such as herein described (b) giving uneven patters on the extruded resin layer by means of an embossing roll when the extruded resin is in the hot-melted state, and (c) thereafter laminating the extruded-molded film with the metal sheet characterized in that the said polyester resin layer has a main component of crystalline polyester resin, and is blended with a resin of low crystallization of 5 to 10 wt% wherein said crystalline polyester resin is crystalline copolymer polyester is which both component is substituted for polyethylene terephthalate, polybutyl terephthalate, or for a part of their multivalent acid component or multivalent alcohol component. 2. A method as claimed in claim 1, wherein said crystalline polyester resin is a resin composed of chips of waste polyethyleneterephthalate. 3. A method as claimed in claim 1, wherein said crystalline polyester resin is crystalline copolymer polyester in which another component is substituted for polyethylene terephthalate, polybutyl terephthalate, or for a part of their multivalent acid component or multivalent alcohol component, or said crystalline polyester resin is at least two sorts of resins composed of chips of waste polyethyleneterephthalate. 4. A method as claimed in claim 2, wherein said resin of low crystallization is copolymer polyester in which another component is substituted for a part of multivalent acid component or multivalent alcohol component or polyethyleneterephthalate; copolymer polyester in which another component is substituted for a part of multivalent acid component or multivalent alcohol component of polybutyleneterephthalate; or polycarbonate. 5. A method substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Documents:

276-del-1998-abstract.pdf

276-del-1998-claims.pdf

276-del-1998-correspondence-others.pdf

276-del-1998-correspondence-po.pdf

276-del-1998-description (complete).pdf

276-del-1998-drawings.pdf

276-del-1998-form-1.pdf

276-del-1998-form-13.pdf

276-del-1998-form-19.pdf

276-del-1998-form-2.pdf

276-del-1998-form-4.pdf

276-del-1998-form-6.pdf

276-del-1998-gpa.pdf