Resin-coated steel sheet for drawn-and-ironed cans and drawn-and-ironed cans manufactured therefrom

• US 5,714,273 A
• Filed: 03/18/1994
• Issued: 02/03/1998
• Est. Priority Date: 11/15/1989
• Status: Expired due to Term

• Current Assignee: Mitsui Chemicals Incorporated (Mitsui Chemicals)
• Original Assignee: Mitsui Petrochemical Industries, Ltd., Nippon Steel Corporation
• Inventors: Hiraoka, Takashi, Niimi, Hiroji, Yoshihara, Ryoichi, Wake, Ryousuke
• Primary Examiner(s): Simmons, David A.
• Assistant Examiner(s): GRAY, LINDA LAMEY
• Application Number:
  US08/210,747
• Time in Patent Office: 1,418 Days
• Field of Search: 428/622, 428/623, 428/621, 428/626, 428/659, 428/666, 428/458, 220/454, 220/455, 220/456, 220/457, 220/458
• US Class Current: 428/626
• CPC Class Codes: B65D 25/14 Linings or internal coatings of containers made by folding or erecting blanks made of paper B65D5/56 ; linings for domestic water storage heaters F24H1/183
• CPC Class Codes: C08L 67/02 Polyesters derived from dicarboxylic acids and dihydroxy compounds C08L67/06 takes precedence
• CPC Class Codes: C09D 167/02 Polyesters derived from dicarboxylic acids and dihydroxy compounds C09D167/06 takes precedence
• CPC Class Codes: Y10T 156/1033 Flexible sheet to cylinder lamina
• CPC Class Codes: Y10T 428/12542 More than one such component
• CPC Class Codes: Y10T 428/12569 Synthetic resin
• CPC Class Codes: Y10T 428/31681 Next to polyester, polyamide or polyimide [e.g., alkyd, glue, or nylon, etc.]

Abstract

A resin-coated steel sheet for drawn-and-ironed cans and a method of producing the resin-coated steel sheet. The resin-coated steel sheet has a steel sheet with a tin-coat on each side and a resin layer of a first crystalline thermoplastic polyester resin on one of the tin-coats and a second non-crystalline thermoplastic polyester resin on the first crystalline thermoplastic polyester resin. The first crystalline thermoplastic polyester resin has an alloying ratio of: 50≦alloying ratio <100. The second non-crystalline thermoplastic polyester resin has an alloying ratio of 0<alloying ratio <50. The method includes thermal fusion of a mixture of 95-5 percent by weight of a crystalline polyester resin and 5-95 percent of a non-crystalline polyester resin to produce the first crystalline thermoplastic polyester resin and the second non-crystalline thermoplastic polyester resin. The first crystalline thermoplastic polyester resin and the second non-crystalline thermoplastic polyester resin are coated onto the tin-coated steel sheet using two-layer extrusion T-die and then cooled quickly.

Claims

1. A resin-coated steel sheet for DI cans, obtained by a method comprising:

providing a mixture containing 95 to 5% by weight of a crystalline polyester resin and 5 to 95% by weight of a non-crystalline polyester resin;

reacting said resins, by means of thermal fusion, to produce a first thermoplastic polyester resin having an alloying ratio, as represented by one of formulas (a) or (b) below, of not less than 50% and less than 100% and a second thermoplastic polyester resin having an alloying ratio, as represented by one of formulas (a) or (b) below, of greater than 0% and less than 50% where (a) and (b) are as follows;

##EQU2## where T_m1 and T_g1 are respectively the melting point and the glass-transition temperature, in °

C., of the crystalline polyester resin, T_m2 and T_g2 are respectively the melting point and the glass-transition temperature, in °

C., of a random copolymer of a polyester resin having a monomer composition equal to that of the respective first and second thermoplastic polyester resins, T_m3 and T_g3 are respectively the melting point and the glass-transition temperature in °

C., of the respective first and second thermoplastic polyester resins;

coating the first and second thermoplastic polyester resins by means of a two-layer extrusion T-die onto one side of a two-sided steel sheet tin-coated on both sides, so that a layer of the first thermoplastic polyester resin is interposed between the tin-coated steel sheet and a layer of the second thermoplastic polyester resin, wherein said first thermoplastic polyester resin retains a degree of crystallinity low enough to assure satisfactory adhesion to the tin-coated steel sheet, even after DI working, while said second thermoplastic polyester resin is in non-crystalline condition and is to be converted by DI working into a crystalline resin layer to assure a satisfactory stripping-out property; and

cooling the coated resins quickly to prevent further crystallization of the layers of the first and second thermoplastic polyester resins.

2. A process for producing a resin-coated steel sheet for DI cans, comprising:

providing a mixture containing 95 to 5% by weight of a crystalline polyester resin and 5 to 95% by weight of a non-crystalline polyester resin;

reacting said resins, by means of thermal fusion, to produce a first thermoplastic polyester resin having an alloying ratio, as represented by one of formulas (a) or (b) below, of not less than 50% and less than 100% and a second thermoplastic polyester resin having an alloying ratio as represented by one of formulas (a) or (b) below, of greater than 0% and less than 50% where (a) and (b) are as follows;

##EQU3## where T_m1 and T_g1 are respectively the melting point and the glass-transition temperature, in °

C., of the crystalline polyester resin, T_m2 and T_g2 are respectively the melting point and the glass-transition temperature, in °

C., of a random copolymer of a polyester resin having a monomer composition equal to that of the respective first and second thermoplastic polyester resins, T_m3 and T_g3 are respectively the melting point and the glass-transition temperature, in °

C., of the respective first and second thermoplastic polyester resins;

coating the first and second thermoplastic polyester resins by means of a two-layer extrusion T-die onto one side of a two-sided steel sheet tin-coated on both sides, so that a layer of the first thermoplastic polyester resin is interposed between the tin-coated steel sheet and a layer of the second thermoplastic polyester resin, wherein said first thermoplastic polyester resin retains a degree of crystallinity low enough to assure satisfactory adhesion to the tin-coated steel sheet, even after DI working, while said second thermoplastic polyester resin is in non-crystalline condition and is to be converted by DI working into a crystalline resin layer to assure a satisfactory stripping-out property; and

cooling the coated resins quickly to prevent further crystallization of the layers of the first and second thermoplastic polyester resins.

3. A drawn and ironed can produced by drawing and ironing a resin-coated steel sheet, wherein the resin-coated steel sheet is obtained by a method comprising:

providing a mixture containing 95 to 5% by weight of a crystalline polyester resin and 5 to 95% by weight of a non-crystalline polyester resin;

reacting said resins, by means of thermal fusion, to produce a first thermoplastic polyester resin having an alloying ratio, as represented by one of formulas (a) or (b) below, of not less than 50% and less than 100% and a second thermoplastic polyester resin having an alloying ratio, as represented by one of formulas (a) or (b) below, of greater than 0% and less than 50% where (a) and (b) are as follows;

##EQU4## where T_m1 and T_g1 are respectively the melting point and the glass-transition temperature, in °

C., of the crystalline polyester resin, T_m2 and T_g2 are respectively the melting point and the glass-transition temperature, in °

C., of a random copolymer of a polyester resin having a monomer composition equal to that of the respective first and second thermoplastic polyester resins, T_m3 and T_g3 are respectively the melting point and the glass-transition temperature, in °

C., of the respective first and second thermoplastic polyester resins;

coating the first and second thermoplastic polyester resins by means of a two-layer extrusion T-die onto one side of a two-sided steel sheet tin-coated on both sides where the one side with the first and second resins forms the inside of the can, so that a layer of the first thermoplastic polyester resin is interposed between the tin-coated steel sheet and a layer of the second thermoplastic polyester resin, wherein said first thermoplastic polyester resin retains a degree of crystallinity low enough to assure satisfactory adhesion to the tin-coated steel sheet, even after DI working, while said second thermoplastic polyester resin is in non-crystalline condition and is to be converted by DI working into a crystalline resin layer to assure a satisfactory stripping-out property; and

cooling the coated resins quickly to prevent further crystallization of the layers of the first and second thermoplastic polyester resins.

4. A process for producing a drawn and ironed can, comprising:

providing a mixture containing 95 to 5% by weight of a crystalline polyester resin and 5 to 95% by weight of a non-crystalline polyester resin;

reacting said resins, by means of thermal fusion, to produce a first thermoplastic polyester resin having an alloying ratio, as represented by one of formulas (a) or (b) below, of not less than 50% and less than 100% and a second thermoplastic polyester resin having an alloying ratio, as represented by one of formulas (a) or (b) below, of greater than 0% and less than 50% where (a) and (b) are as follows;

##EQU5## where T_m1 and T_g1 are respectively the melting point and the glass-transition temperature, in °

C., of the crystalline polyester resin, T_m2 and T_g2 are respectively a melting point and a glass-transition temperature, in °

C. of a random copolymer of a polyester resin having a monomer composition equal to that of the respective first and second thermoplastic polyester resins, T_m3 and T_g3 are respectively the melting point and the glass-transition temperature, in °

C., of the respective first and second thermoplastic polyester resins;

coating the first and second thermoplastic polyester resins by means of a two-layer extrusion T-die onto the side of a two-sided steel sheet tin-coated on both sides, so that a layer of the first thermoplastic polyester resin is interposed between the tin-coated steel sheet and a layer of the second thermoplastic polyester resin, wherein said first thermoplastic polyester resin retains a degree of crystallinity low enough to assure satisfactory adhesion to the tin-coated steel sheet, even after DI working, while said second thermoplastic polyester resin is in non-crystalline condition and is to be converted by DI working into a crystalline resin layer to assure a satisfactory stripping-out property;

cooling the coated resins quickly to produce a resin-coated steel sheet and to prevent further crystallization of the layers of the first and second thermoplastic polyester resins; and

drawing and ironing the resultant resin-coated steel sheet to form a can, with the resin-coated side of the steel sheet forming the inside of the can.