Coating composition for producing a layer composite

Abstract

A coating composition for producing a layer composite, including a) a modified or unmodified polyvinyl alcohol, b) an alkylene/(meth)acrylic acid copolymer, c) a crosslinker, and d) one, two or more than two, pigments. The layer composite is used as food packaging, entry ticket, gaming ticket, car park ticket, or the like. A mixture of alkylene/(meth)acrylic acid copolymer and modified or unmodified polyvinyl alcohol is used in a layer of a layer composite, to the use of a coating composition for producing a layer composite.

Claims

1. A layer composite comprising: a carrier layer; and an enhancement layer, produced from a coating composition, comprising: an acetoacetyl-modified polyvinyl alcohol; an alkylene/(meth)acrylic acid copolymer; wherein the alkylene (methyl) acrylic acid polymer is ethylene/acrylacid copolymer; a crosslinker; and at least one pigment:, wherein the layer composite comprises: a heat-sensitive recording layer which is disposed between the carrier layer and the coating composition and which comprises a dye precursor and a color developer, and the color developer on exposure to heat is able to induce color formation in the dye precursor, wherein the heat-sensitive recording layer comprises an acetoacetyl-modified polyvinyl alcohol and wherein at least one pigment in the coating composition comprises two pigments, which are kaolin, in a mass fraction of 0.3 to 0.4 and precipitated silica, in a mass fraction of 0.02 to 0.04, which has a mean particle size in the range from 6 to 10 ?m, determined by particle size analysis by a laser diffraction method.

2. The coating composition as claimed in claim 1, wherein during the formation of the enhancement layer after the application of the coating composition, the crosslinker has crosslinked the acetoacetyl-modified polyvinyl alcohol and/or the alkylene/(meth)acrylic acid copolymer with one another, to result in a crosslinked polymer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an image of a square of heat sensitive recording material; and

(2) FIG. 2 is an image of a square of heat sensitive recording material.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Inventive Example 1

(3) A coating composition according to one aspect of the invention is prepared. The coating composition is prepared by mixing the constituents in Table 1.

(4) TABLE-US-00001 TABLE 1 Mass fractions w(x) Component Constituent (BD) Pigment Kaolin (Trade name: ASP 179) 0.30 to 0.40 Pigment Silica (Trade name: Sipernat 22S) 0.020 to 0.040 Polyvinyl Acetoacetyl-modified PVA (Trade 0.05 to 0.15 alcohol name: Gohsenx Z-410) Polyvinyl Acetoacetyl-modified PVA (Trade 0.20 to 0.50 alcohol name: Gohsenx Z-200) Additive Zinc stearate (Trade name: Hidorin 0.05 to 0.07 Z-7-30) Crosslinker Polyamidoamine epichlorohydrin 0.015 to 0.035 resin (Trade name: Giluton 20XP) Alkylene/ Ethylene acrylic acid copolymer 0.015 to 0.040 (meth)acrylic (Trade name: Aquacer 1061) acid copolymer Crosslinkers Sodium/calcium glyoxylate (Trade 0.005 to 0.020 name: SPM-01/SPM-02)

(5) A coating composition according to one aspect of the invention is obtained, and can be used for producing layer composites (e.g., heat-sensitive recording materials).

Inventive Example 2

(6) The sheetlike substrate used is a carrier paper having a mass per unit area of 64 g/m.sup.2, produced on a fourdrinier paper machine from bleached and ground hardwood and softwood pulps, with addition, based on the overall solids content (BD) of the pulp supplied to the paper machine, of 0.008 mass fraction of resin size as a stock sizing, and also of other customary adjuvants.

(7) Applied to the front side is an interlayer comprising calcined kaolin as pigment, styrene-butadiene latex as binder and, in addition to other auxiliaries, starch as cobinder, this interlayer being applied with a mass per unit area of 9 g/m.sup.2, using a coating knife.

(8) Applied atop this pigmented interlayer, using a roller blade coater, is a heat-sensitive recording layer having a mass per unit area of 2.5 g/m.sup.2. The aqueous coating slip used for this purpose contains the following components, according to the formulation reproduced in Table 2:

(9) TABLE-US-00002 TABLE 2 Amounts in mass fractions w(x) (BD), based on the total mass of the heat-sensitive recording layer Dye 3-Dibutylamino-6-methyl-7- 0.10 to 0.20 precursor anilinofluoran (ODB-2) Color N-(p-Toluenesulfonyl)-N-3-(p- 0.20 to 0.30 developer toluenesulfonyloxyphenyl)urea (Pergafast? 201 (BASF)) Sensitizer Benzyl 2-naphthyl ether (BNE) 0.20 to 0.30 Binder Ethylene-vinyl alcohol copolymer 0.10 to 0.20 (RS 2117) Binder Acetoacetyl-modified PVA (Trade 0.010 to 0.025 name: Gohsenx Z-200) Sensitizer Methylolamide dispersion (Hidorin 0.015 to 0.030 D757) Additive Paraffin wax (Hidorin J 157) 0.010 to 0.025 Additive Zinc stearate (Hidorin SZ 40) 0.010 to 0.025 Optical Hexasodium 2,2-{vinylenebis[(3- 0.003 to 0.007 brightener sulfonato-4,1- phenylene)imino[6- morpholino-1,3,5-triazine-4,2- diyl]imino]}bis(benzene-1,4- disulfonate; CAS No. 52301-70-9; Ciba Speciality Chemicals Inc.; Basel; CH)

(10) After the heat-sensitive recording layer has been applied, it is dried and calendered.

(11) Applied atop this dried, heat-sensitive recording layer, using a roller blade coater, is a coating composition of the invention, prepared according to inventive example 1, with a mass per unit area of 2 g/m.sup.2.

(12) A heat-sensitive recording material is obtained which is a layer composite.

(13) The heat-sensitive recording material produced has extremely good offset-printability and extremely good water resistance.

Comparative Example 1

(14) Comparative example 1 is carried out in analogy to inventive example 2, but without the addition of silica as pigment and without the addition of the ethylene-acrylic acid copolymer. Instead the amount of kaolin and acetoacetyl-modified PVA (Trade name: Gohsenx? Z-200) is adapted accordingly.

(15) Determination of Water Resistance:

(16) Squares each measuring 5 cm times 10 cm were cut out from the heat-sensitive recording material under test, from inventive example 2 and comparative example 1.

(17) The squares cut out were each folded in the middle, so that two 5 cm times 5 cm regions of the coating side were lying one against the other. The fold was opened and the coating side was wetted with one drop of water. The fold was then closed again and pressed together. The folded and wetted squares were placed between two glass plates, and a filter paper was placed between the squares. The glass plates were weighted down and left to stand for 24 hours. The squares were then separated, carefully unfolded, and dried in an oven at 90? C. for one hour. The squares were subsequently taken from the oven and weighted down.

(18) The square produced from the heat-sensitive recording material produced according to inventive example 2 could be unfolded without detachment of the surface, the surface having a uniform black coloration. An image of the square is shown in FIG. 1.

(19) The square produced from the heat-sensitive recording material produced according to comparative example 1 exhibited detachment of the surface on unfolding, and the surface did not have a uniform black coloration. An image of the square is shown in FIG. 2. It can be assumed that during offset printing there is detachment of the surface and that on storage under damp conditions it is not possible to ensure thermal printability.

(20) Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.