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JP-7137211-B2 - Aqueous pigment dispersion

JP7137211B2JP 7137211 B2JP7137211 B2JP 7137211B2JP-7137211-B2

Inventors

  • 川口 太生

Assignees

  • 花王株式会社
  • 花王株式会社

Dates

Publication Date
20220914
Application Date
20181228
Priority Date
20171228

Claims (12)

  1. A method for producing an aqueous pigment dispersion, comprising the following steps 1 and 2. Step 1: A step of applying a shear stress to a pigment mixture containing a pigment, a (meth)acrylic resin (A) having an acid group, and a polyester resin (B) to obtain a dispersion by dispersing. : A step of cross-linking the dispersion obtained in step 1 using a cross-linking agent (C)
  2. The amount of the cross-linking agent (C) used in step 2 is a ratio of the number of molar equivalents of the crosslinkable functional groups of the (meth)acrylic resin (A) to the number of molar equivalents of the acid groups of the (meth)acrylic resin (A), which is 0.00. The method for producing a water-based pigment dispersion according to claim 1 , wherein the ratio is 12 or more and 0.65 or less.
  3. The mass ratio of polyester resin (B) to (meth)acrylic resin (A) in the pigment mixture in step 1 [polyester resin (B)/(meth)acrylic resin (A)] is 0.15 or more and 15 or less. A method for producing an aqueous pigment dispersion according to claim 1 or 2 .
  4. 4. The method for producing an aqueous pigment dispersion according to any one of claims 1 to 3, wherein the means for applying shear stress is to use a high-pressure homogenizer.
  5. 5. The method for producing a water-based pigment dispersion according to claim 4, wherein the treatment pressure when performing the dispersion treatment using a high-pressure homogenizer is 60 MPa or more and 300 MPa or less.
  6. 6. The method for producing a water-based pigment dispersion according to claim 4, wherein the number of passes is 3 or more and 30 or less when performing the dispersion treatment using a high-pressure homogenizer.
  7. 7. The method for producing an aqueous pigment dispersion according to any one of claims 1 to 6, further comprising the following steps 1-1 and 1-2 before step 1. Step 1-1: A step of dispersing a pigment in a (meth)acrylic resin (A) having an acid group to obtain a preliminary dispersion. Step 1-2: An emulsion of a polyester resin (B) is added to the preliminary dispersion obtained in step 1-1 to obtain a pigment, a (meth)acrylic resin (A) having an acid group, and a polyester resin ( B) obtaining a pigment mixture comprising
  8. The method for producing an aqueous pigment dispersion according to any one of claims 1 to 7, wherein both the (meth)acrylic resin (A) and the polyester resin (B) have an acid group.
  9. The method for producing an aqueous pigment dispersion according to any one of claims 1 to 8, wherein the cross-linking agent (C) is a polyglycidyl ether compound of a polyhydric alcohol having a hydrocarbon group with 3 to 8 carbon atoms.
  10. The mass ratio of the pigment in the total solid content of the water-based pigment dispersion [pigment/(total solid content of the water-based pigment dispersion)] is 0.25 or more and 0.85 or less, according to any one of claims 1 to 9 A method for producing an aqueous pigment dispersion.
  11. The mass ratio of the pigment to the total amount of the pigment and the (meth)acrylic resin (A) in the water-based pigment dispersion [pigment/(pigment+(meth)acrylic resin (A))] is 0.3 or more and 0.3. 95 or less, the method for producing a water-based pigment dispersion according to any one of claims 1 to 10.
  12. A method for producing a water-based ink, comprising mixing the water-based pigment dispersion according to any one of claims 1 to 11 and an organic solvent.

Description

TECHNICAL FIELD The present invention relates to a water-based pigment dispersion and a method for producing the water-based pigment dispersion. In the field of commercial printing and industrial printing such as label printing used for product packaging printing and advertisements, PET (polyethylene terephthalate), PVC (polyvinyl chloride), PE (polyethylene), PP (polypropylene), NY (nylon), etc. 2. Description of the Related Art Solvent-based inks, UV curable inks, etc. have conventionally been used for printing on resin printing media. On the other hand, from the viewpoints of environmental load reduction, energy saving, safety, etc., as printing methods using water-based inks, ink jet recording methods, flexographic printing methods, and gravure printing methods are required. In addition, from the viewpoint of weather resistance and water resistance of printed matter, water-based inks using pigments as colorants have become mainstream. However, since the resin print medium is non-absorbent and the water-based ink does not permeate the inside of the print medium, the pigment particles contained in the water-based ink remain on the surface of the print medium. Therefore, conventional water-based inks are insufficient in adhesion to the printing medium and scratch resistance, and various attempts have been made to improve these problems. For example, in Patent Document 1, for the purpose of obtaining a colored film having both light resistance and abrasion resistance and obtaining an aqueous pigment dispersion having excellent storage stability, a pigment and a (meth)acrylic ester are disclosed. An aqueous pigment dispersion containing a resin and a polyurethane resin, wherein the resin component contains a large amount of a (meth)acrylic acid ester resin as a non-volatile matter, and the polyurethane resin has an average dispersed particle diameter within a specific range. Dispersions and the like are disclosed. In Patent Document 2, for the purpose of providing an aqueous pigment dispersion composition exhibiting excellent dispersibility and the like, and an aqueous ink composition in which the resulting coating film exhibits excellent image density and the like and exhibits excellent gloss, Disclosed are specific aqueous polyurethane dispersion resins, pigment aqueous dispersion compositions comprising pigments and dispersants, and the like. In Patent Document 3, for the purpose of providing a pigment dispersion or the like having excellent glossiness and storage stability of an ink composition, a pigment, an aqueous medium, a hydrophobic monomer and a hydrophilic monomer are co-prepared. It contains at least a polymer resin, a urethane resin, and a cross-linking agent, and the effective solid content weight ratio of the amount of the cross-linking agent added (amount of cross-linking agent/(copolymer resin of hydrophobic monomer and hydrophilic monomer and urethane resin and the total amount)) is within a specific range. Patent Document 4 describes water-based inks that have excellent adhesion and glossiness to recording media made of resin such as PET, PVC, PP, and NY, and also have excellent blocking resistance during storage of recording media after printing. It contains polyester resin particles and modified polyolefin resin particles, the resin constituting the polyester resin particles contains an amorphous polyester having a glass transition temperature within a specific range, and the mass ratio of the polyester resin particles to the modified polyolefin resin particles is specified. Water-based inks are disclosed that range from . JP-A-2004-131586Japanese Patent Application Laid-Open No. 2013-53200JP 2005-48016 AJP 2016-222896 A [Aqueous Pigment Dispersion] The aqueous pigment dispersion of the present invention is an aqueous pigment dispersion in which a pigment is dispersed in an aqueous medium using a polymer dispersant, the polymer dispersant comprising a (meth)acrylic resin (A) and a polyester resin (B). and The term "aqueous medium" means a medium in which water accounts for the largest proportion of the medium in which the pigment is dispersed. The water-based pigment dispersion of the present invention has excellent storage stability and can give good printed matter having excellent adhesion and high print density. It can be suitably used as a water-based pigment dispersion for ink-jet inks, and is particularly preferably used as a water-based pigment dispersion for inkjet inks. The water-based pigment dispersion of the present invention has excellent storage stability, and when used in water-based inks, both adhesion to non-water-absorbent printing media and print density can be improved. Although the reason is not clear, it is considered as follows. In the water-based pigment dispersion of the present invention, it is presumed that the pigment is dispersed in the water-based medium while the polymer dispersant is adsorbed or immobilized on the surface of the pigment. By containing the