An eco-friendly long-lasting heat-sensitive paper, comprising a substrate layer, a base color layer, a heat-sensitive covering layer, and a protective layer that are arranged sequentially from bottom to top,
- wherein the heat-sensitive covering layer is prepared as follows:
- coating a heat-sensitive covering layer raw material on the base color layer, and oven-drying a resulting product, wherein the heat-sensitive covering layer raw material is an emulsion obtained by mixing an acrylic hollow microsphere with a host resin, and a mass ratio of the acrylic hollow microsphere to the host resin in the emulsion is 3:2 to 5:1;
- wherein the heat-sensitive covering layer raw material is prepared by the following process:
- S1-1:
- preparation of the acrylic hollow microsphere:
- S1-1-1:
- in parts by weight, adding 8 to 24 parts of sodium 2-ethylhexyl sulfate, 15 to 40 parts of magnesium nitrate, and 5 to 15 parts of sodium dodecyl sulfate (SDS) to 400 to 600 parts of deionized water to obtain a precursor dispersion, adding 30 to 60 parts of a sodium hydroxide aqueous solution dropwise to the precursor dispersion under continuous stirring, and continuously stirring a resulting mixture for 20 min to 60 min to obtain a dispersion as an aqueous phase;
- S1-1-2:
- in parts by weight, mixing 100 parts of a monomer with a regulating agent A, adding 2 to 8 parts of dibenzoyl peroxide, a regulating agent B, and 40 to 60 parts of a foaming agent, and thoroughly mixing a resulting mixture to obtain an oil phase,
- wherein the monomer is a mixture of methyl methacrylate (MMA), ethyl methacrylate (EMA), methacrylic acid (MAA), an acrylamide, and styrene, and in the monomer, a mass fraction of the EMA is 22% to 34%, a mass fraction of the MAA is 18% to 30%, a mass fraction of the acrylamide is 12% to 24%, a mass fraction of the styrene is 5% to 10%, and the MMA accounts for the balance;
- the foaming agent is a mixture of isooctane and n-hexane, and a mass ratio of the isooctane to the n-hexane is 2:1;
- the regulating agent A is dipropylene glycol diacrylate (DPGDA);
- the regulating agent B is one or a mixture of two or more selected from the group consisting of 2,2′-methylene-bis(4,6-di-tert-butylphenyl phosphate) basic aluminum, sodium 2,2′-methylenebis(4,6-di-tert-butylphenyl)phosphate, and bis(4-tert-butyl-benzoate)aluminum hydroxide;
- and a mass ratio of the regulating agent A to the regulating agent B is 3:2 to 5:1;
- and
- S1-1-3:
- mixing the aqueous phase and the oil phase, stirring a resulting mixed phase at 4,000 rpm to 10,000 rpm to obtain a mixture, and transferring the mixture to a reactor;
- and subjecting the mixture to a reaction at 8 kPa to 15 kPa and 45° C. to 65° C. for 16 h to 30 h, cooling and filtering a resulting reaction system, and washing and drying a resulting solid product to obtain the acrylic hollow microsphere;
- and
- S1-2:
- preparation of the heat-sensitive covering layer raw material:
- with a mass ratio of the acrylic hollow microsphere to the host resin being 3:2 to 5:1, adding the acrylic hollow microsphere to an emulsion of the host resin, and thoroughly stirring a resulting mixture to obtain an emulsion formed by the acrylic hollow microsphere and the host resin, which is the heat-sensitive covering layer raw material.