Feldmuhle Aktiengesellschaft

Bayer Aktiengesellschaft

Feldmuehle Aktiengesellschaft

Kurt Riecke

Guido Dessauer

Franz Wirnitzer

Kurt Ramlow

Ferdinand Land

Gert Jabs

Manfred Dahm

Bernd Koglin

Hildegard Schnoring

In microcapsules of the type used for pressure-sensitive, carbonless copy papers, having walls formed from aliphatic diisocyanate and diamine and containing a solvent mixture with a dye precursor dissolved therein, the solvent mixture containing a component which easily dissolves the dye precursor and the capsule wall material and a component which only poorly dissolves the dye precursor and the capsule wall, the improvement comprising the poorly dissolving solvent component is an alkylbenzene having from 8 up to 14 C-atoms in the alkyl moiety; and the easily dissolving solvent component is selected from the group consisting of diisopropyl naphthalene, a hydrogenated terphenyl, an alkylated diphenyl, a diphenyl alkane, a chloroparaffin and a mixture thereof, the ratio of easily to poorly dissolving components ranging form 15:85 to 75:25 vol %, and being adjusted within this range so that a solution of the wall-forming aliphatic diisocyanate is just at the turbidity point in the mixture of easily dissolving and poorly dissolving components.

Microcapsules having capsule walls formed of aliphatic diisocyanate and

In microcapsules of the type used for pressure-sensitive, carbonless copy papers, having walls formed from aliphatic diisocyanate and diamine and containing a solvent mixture with a dye precursor dissolved therein, the solvent mixture containing a component which easily dissolves the dye precursor and the capsule wall material and a component which only poorly dissolves the dye precursor and the capsule wall, the improvement comprising the poorly disolving solvent component is an alkylbenzene having from 8 up to 14 C-atoms in the alkyl moiety; and the easily dissolving solvent component is selected from the group consisting of diisopropyl naphthaline, a hydrogenated terphenyl, an alkylated diphenyl, a diphenyl alkane, a chloroparaffin and a mixture thereof, the ratio of easily to poorly dissolving components ranging from 15:85 to 75:25 vol %, and being adjusted within this range so that a solution of the wall-forming aliphatic diisocyanate is just at the turbidity point in the mixture of easily dissolving and poorly dissolving components.

Microcapsules containing a color-former solution which is encapsulated in the form of a solution in an organic solvent in capsules of the polyaddition product of a diisocyanate corresponding to the following general formula: ##STR1## wherein n=3-6 and a diamine wherein a mixture of an alkyl naphthalene and an isoparaffin containing from 10 to 20 carbon atoms is used as the solvent for the color-former and the microcapsules are tempered for at least 2 hours at a temperature of from 60.degree. to 70.degree. C. after their formation.

Microcapsules and their preparation

Acceptor sheets for carbonless copying are prepared by coating a suitable substrate with an aqueous composition which, in addition to known dispersed acceptor materials, such as acid treated clays, contains at least one basic zinc salt substantially insoluble in water in an amount, as ZnO, of 2 to 50% by weight of the acceptor pigments on a dry basis, the composition having a pH below 7.

Coating composition for acceptor sheets in carbonless copying

In a donor material for carbonless copying which mainly consists of a carrier sheet and a multiplicity of frangible microcapsules containing a suitable dye precursor in a liquid medium and secured to one face of the sheet, spacer particles of soybean protein are interspersed in a relatively small amount between the microcapsules and project beyond the microcapsules away from the carrier sheet to protect the microcapsules against premature fracture.

Donor material for carbonless copying

A recording sheet consisting mainly of fibrous material is capable of displaying a colored image when contacted under pressure with substantially colorless crystal violet lactone and similar dye precursors if at least 3% of the fibrous material is constituted by uniformly distributed asbestos fibers. Sheets having adequate strength for carbonless copying should not contain more than 30% asbestos fibers. Stronger colors are obtained if the sheet further contains a mixture of .gamma.-alumina and .gamma.-alumina precursors in an amount of 2% to 20% of the weight of the fibrous material, the mixture containing 1% to 30% water volatile at 1000.degree. C, and being converted substantially entirely to .gamma.-alumina when heated from 300.degree. to 1000.degree. C.

Recording material containing asbestos

A mixture of .gamma.-alumina and its precursors containing 1 to 30% water volatile at 1000.degree. C converts normally colorless dye materials such as crystal violet lactone, malachite green lactone, benzoyl leuco methylene blue and N-phenylleukauramine to the corresponding colored dyes upon contact, and improves the results achieved with recording material consisting essentially of a fibrous web and a pigment composition secured to the fibers of the web if the mixture amounts to at least 10% of the weight of the pigment composition. Particularly strong and stable colors are produced if the fibrous web is coated with a pigment composition prepared from an aqueous dispersion of the mixture and other pigments on which a basic compound is deposited from a water-soluble zinc salt by means of hydroxyl ions.

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Kempen, Germany

Kurt Riecke