Use of starch dispersions as binder in coating compositions and process for preparing the starch dispersions
Coating compositions comprising a pigment and starch dispersion of discrete crosslinked starch particles in an aqueous liquid. The dispersion may be used as coating color for paper. A preferred process of preparing the dispersion of starch particles comprises (a) obtaining a mixture of starch and an aqueous liquid; (b) processing the mixture using shear forces in the presence of a crosslinker in an extruder; and (c) injecting a hydroxylic liquid into the extruder and dispersing the mixture inside the extruder or outside the extruder or both inside and outside the extruder to obtain the dispersion.
1. A method for the preparation of a pigmented coating composition, which comprises: mixing a pigment and a binder comprising a starch dispersion of discrete cross-linked starch particles in an aqueous liquid, wherein,
the particle size distribution of the discrete-cross-linked starch particles in the starch dispersion ranges from 200 nm to 100 μm, and
the starch dispersion has a solid content ranging from 25 to 50% by weight.
2. A method for the preparation of a pigmented coating composition, which comprises: mixing a pigment and a binder comprising a starch dispersion of discrete cross-linked starch particles in an aqueous liquid, wherein,
the particle size distribution of the discrete-cross-linked starch particles in the starch dispersion ranges from 200 nm to 100 μm, and
the pigmented coating composition comprises:
(a) 100 parts by weight of pigment; and
(b) 1 to 300 parts by weight of starch, all based on dry weight.
3. The method according to claim 2 , wherein the pigmented coating composition further comprises a synthetic latex.
4. The method according to claim 3 , wherein the pigmented coating composition comprises:
(a) 100 parts by weight of pigment;
(b) 1 to 300 parts by weight of starch; and
(c) 1 to 20 parts by weight of synthetic latex, all based on dry weight.
5. A method for coating a substrate, comprising:
coating a substrate with a pigmented coating composition;
said pigmented coating composition obtained by mixing a pigment and a binder comprising a starch dispersion of discrete cross-linked starch particles in an aqueous liquid, wherein,
the particle size distribution of the discrete-cross-linked starch particles in the starch dispersion ranges from 200 nm to 100 μm.
6. The method according to claim 5 , wherein the substrate is selected from the group consisting of paper, cardboard and plastic film.
7. A method for the preparation of a pigmented coating composition, comprising:
mixing a pigment and a binder comprising a starch dispersion of discrete cross-linked starch particles in an aqueous liquid to form a coating composition, wherein,
the coating composition has a solids content ranging from 50 to 64% by weight, and
the starch particles in the starch dispersion range from 200 nm to 100 μm in size.