Aqueous dispersion resin composition, resin composition for a thermal recording layer, resin composition for a protection layer, and thermal recording material

1. An aqueous dispersion resin composition comprising:

a first polymer produced by polymerizing a first monomer component containing (meth)acrylamide and a first copolymerizable monomer that is copolymerizable with (meth)acrylamide, and

a second polymer produced by polymerizing a second monomer component containing a carboxy group-containing vinyl monomer and a second copolymerizable monomer that is copolymerizable with carboxy group-containing vinyl monomer, the second polymer being covered with the first polymer, and including core-shell particles consisting of the first polymer and the second polymer,

wherein the carboxy group-containing vinyl monomer content relative to 100 parts by mass of the second monomer component is 4 parts by mass or more and 10 parts by mass or less,

the carboxy group-containing vinyl monomer is methacrylic acid, and,

at least a portion of the carboxy group in the second polymer is neutralized after polymerizing the second monomer component, and then kept for 30 minutes or more.

2. The aqueous dispersion resin composition according to claim 1 , wherein the (meth)acrylamide content relative to 100 parts by mass of the first monomer component is 50 parts by mass or more and 100 parts by mass or less.

3. The aqueous dispersion resin composition according to claim 1 , wherein the first monomer component further contains a carboxy group-containing vinyl monomer and/or a hydroxyl group-containing vinyl monomer.

4. The aqueous dispersion resin composition according to claim 1 , wherein the second monomer component further contains (meth)acrylonitrile, and

the (meth)acrylonitrile content relative to 100 parts by mass of the second monomer component is 15 parts by mass or more and 90 parts by mass or less.

5. The aqueous dispersion resin composition according to claim 1 , wherein the first polymer content relative to 100 parts by mass of the second polymer is 5 parts by mass or more and 500 parts by mass or less.

6. The aqueous dispersion resin composition according to claim 1 , wherein the carboxylic acid salt formed by neutralizing at least a portion of the carboxy group is ammonium salt.

7. The aqueous dispersion resin composition according to claim 1 , wherein the carboxy group in the second polymer is neutralized by adding salt-containing water after polymerizing the second monomer component.

8. The aqueous dispersion resin composition according to claim 1 , wherein the first monomer component and/or the second monomer component further contains a sulfonic acid group-containing vinyl monomer and/or its salt.

9. The aqueous dispersion resin composition according to claim 8 , wherein when the first monomer component contains the sulfonic acid group-containing vinyl monomer and/or its salt, the content thereof relative to 100 parts by mass of a total of the first monomer component is 0.01 parts by mass or more and 20 parts by mass or less, and

when the second monomer component contains the sulfonic acid group-containing vinyl monomer and/or its salt, the content thereof relative to 100 parts by mass of a total of the second monomer component is 0.01 parts by mass or more and 20 parts by mass or less.

10. A resin composition for a thermal recording layer, wherein the resin composition is used for a thermal recording layer of a thermal recording material comprising a support layer, a thermal recording layer, and a protection layer; and

the resin composition for a thermal recording layer comprises the aqueous dispersion resin composition according to claim 1 .

11. A thermal recording material comprising a support layer,

a thermal recording layer laminated on one side in the thickness direction of the support layer, and

a protection layer laminated on one side in the thickness direction of the thermal recording layer,

wherein the thermal recording layer comprises a cured product of the resin composition for a thermal recording layer according to claim 10 .

12. The thermal recording material according to claim 11 produced by applying the resin composition for a thermal recording layer to the support layer by curtain coating, curing the resin composition for a thermal recording layer to form the thermal recording layer, and

laminating the protection layer on the thermal recording layer.

13. A resin composition for a protection layer, wherein the resin composition is used for protection layer of a thermal recording material, the thermal recording material comprises a support layer, a thermal recording layer, and a protection layer, and

the resin composition for a protection layer comprises the aqueous dispersion resin composition according to claim 1 .

14. A thermal recording material comprising a support layer,

a thermal recording layer laminated on one side in the thickness direction of the support layer, and

a protection layer laminated on one side in the thickness direction of the thermal recording layer,

wherein the protection layer comprises a cured product of the resin composition for a protection layer according to claim 13 .

15. The thermal recording material according to claim 14 produced by laminating the thermal recording layer on the support layer,

then applying the resin composition for a protection layer to the thermal recording layer by curtain coating, and curing the resin composition for a protection layer.