Method for manufacturing a resin-coated steel sheet for drawn-and-ironed cans

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 thermoplastic polyester resin having an alloying ratio, as represented by one of formulas (a) or (b) below, of 20 to 80% where (a) and (b) are as follows:
• ##EQU3## where T.sub.m1 and T.sub.g1 are respectively the melting point and the glass-transition temperature, in .degree. C., of the crystalline polyester resin, T.sub.m2 and T.sub.g2 are respectively the melting point and the glass-transition temperature, in .degree. C., of a random copolymer of a polyester resin having a monomer composition equal to that of the thermoplastic polyester resin, T.sub.m3 and T.sub.g3 are respectively the melting point and the glass-transition temperature, in .degree. C., of the thermoplastic polyester resin;
• coating the thermoplastic polyester resin by means of a T-die onto one side of a steel sheet which is tin-coated on both sides, wherein said thermoplastic polyester resin as applied on the steel sheet 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 resin quickly to prevent further crystallization of the thermoplastic polyester resin.

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

• providing a mixture containing a crystalline polyester resin and a non-crystalline polyester resin;
• reacting said resins, by means of thermal fusion, to produce a 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.sub.m1 and T.sub.g1 are respectively the melting point and the glass-transition temperature, in .degree. C., of the crystalline polyester resin, T.sub.m2 and T.sub.g2 are respectively the melting point and the glass-transition temperature, in .degree. C., of a random copolymer of a polyester resin having a monomer composition equal to that of the thermoplastic polyester resin, T.sub.m3 and T.sub.g3 are respectively the melting point and the glass-transition temperature, in .degree. C. of the thermoplastic polyester resin;
• providing a steel sheet which is tin-coated on both sides and wherein one side is further coated with a non-crystalline polyester resin layer;
• coating the thermoplastic polyester resin by means of a T-die onto the non-crystalline polyester resin layer, wherein said thermoplastic polyester resin as applied on said layer 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 resin quickly to prevent further crystallization of the thermoplastic polyester resin.

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

• providing a mixture containing a crystalline polyester resin and a non-crystalline polyester resin;
• reacting said resins, by means of thermal fusion, to produce a 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% where (a) and (b) are as follows:
• ##EQU5## where T.sub.m1 and T.sub.g1 are respectively the melting point and the glass-transition temperature, in .degree. C. of the crystalline polyester resin, T.sub.m2 and T.sub.g2 are respectively the melting point and the glass-transition temperature, in .degree. C. of a random copolymer of a polyester resin having a monomer composition equal to that of the thermoplastic polyester resin, T.sub.m3 and T.sub.g3 are respectively the melting point and the glass-transition temperature, in .degree. C. of the thermoplastic polyester resin;
• coating the thermoplastic polyester resin by means of a T-die onto one side of a steel sheet which is tin-coated on both sides, and further coating the coated thermoplastic polyester resin by means of a T-die with a second crystalline polyester resin, wherein said thermoplastic polyester resin as applied on the steel sheet 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 thermoplastic polyester resin.

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 thermoplastic polyester resin having an alloying ratio, as represented by formulas (a) or (b) below, of 5 to 50% where (a) and (b) are as follows:
• ##EQU6## where T.sub.m1 and T.sub.g1 are respectively the melting point and the glass-transition temperature, in .degree. C., of the crystalline polyester resin, T.sub.m2 and T.sub.g2 are respectively the melting point and the glass-transition temperature, in .degree. C., of a random copolymer of a polyester resin having a monomer composition equal to that of the thermoplastic polyester resin, T.sub.m3 and T.sub.g3 are respectively the melting point and the glass-transition temperature, in .degree. C., of the thermoplastic polyester resin;
• coating the thermoplastic polyester resin by means of a T-die onto a chromate-treated side of a steel sheet, which is tin-coated on the other side, wherein said thermoplastic polyester resin as applied on the steel sheet 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 resin quickly to prevent further crystallization of the thermoplastic polyester resin;
• and
• drawing and ironing the resultant resin-coated steel sheet to from a can, with the resin-coated side of the steel sheet forming the inside of the can.

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 thermoplastic polyester resin having an alloying ratio, as represented by one of formulas (a) or (b) below, of 20 to 80% where (a) and (b) are as follows:
• ##EQU7## where T.sub.m1 and T.sub.g1 are respectively the melting point and the glass-transition temperature, in .degree. C., of the crystalline polyester resin, T.sub.m2 and T.sub.g2 are respectively the melting point and the glass-transition temperature, in .degree. C., of a random copolymer of a polyester resin a having a monomer composition equal to that of the thermoplastic polyester resin, T.sub.m3 and T.sub.g3 are respectively the melting point and the glass-transition temperature, in .degree. C., of the thermoplastic polyester resin;
• coating the thermoplastic polyester resin by means of a T-die onto one side of a steel sheet which is tin-coated on both sides, wherein said thermoplastic polyester resin as applied on the steel sheet 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 resin quickly to prevent further crystallization of the thermoplastic polyester resin;
• and
• drawing and ironing the resultant resin-coated steel sheet to from a can, with the resin-coated side of the steel sheet forming the inside of the can.

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

• providing a mixture containing a crystalline polyester resin and a non-crystalline polyester resin;
• reacting said resins, by means of thermal fusion, to produce a 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:
• ##EQU8## where T.sub.m1 and T.sub.g1 are respectively the melting point and the glass-transition temperature, in .degree. C., of the crystalline polyester resin, T.sub.m2 and T.sub.g2 are respectively the melting point and the glass-transition temperature, in .degree. C., of a random copolymer of a polyester resin having a monomer composition equal to that of the thermoplastic polyester resin, T.sub.m3 and T.sub.g3 are respectively the melting point and the glass-transition temperature, in .degree. C., of the thermoplastic polyester resin;
• providing a steel sheet which is tin-coated on both sides and wherein one side is further coated with a non-crystalline polyester resin layer;
• coating the thermoplastic polyester resin by means of a T-die onto the non-crystalline polyester resin layer, wherein said thermoplastic polyester resin as applied on said layer 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 resin quickly to prevent further crystallization of the thermoplastic polyester resin;
• and
• drawing and ironing the resultant resin-coated steel sheet to from a can, with the resin-coated side of the steel sheet forming the inside of the can.

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

• providing a mixture containing a crystalline polyester resin and a non-crystalline polyester resin;
• reacting said resins, by means of thermal fusion, to produce a thermoplastic polyester resin having an alloying ratio, as represented by one of formulas (a) and (b) below, of not less than 50% and less than 100% where (a) and (b) are as follows:
• ##EQU9## where T.sub.m1 and T.sub.g1 are respectively the melting point and the glass-transition temperature, in .degree. C., of the crystalline polyester resin, T.sub.m2 and T.sub.g2 are respectively the melting point and the glass-transition temperature, in .degree. C., of a random copolymer of a polyester resin having a monomer composition equal to that of the thermoplastic polyester resin, T.sub.m3 and T.sub.g3 are respectively the melting point and a glass-transition temperature, in .degree. C., of the thermoplastic polyester resin;
• coating the thermoplastic polyester resin by means of a T-die onto one side of a steel sheet which is tin-coated on both sides, and further coating the coated thermoplastic polyester resin by means of a T-die with a second crystalline polyester resin, wherein said thermoplastic polyester resin as applied on the steel sheet 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 prevent further crystallization of the thermoplastic polyester resin;
• 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.