DE2044780B2 - Gray paper opaque to actinic light and process for its manufacture - Google Patents

Description

55

The invention relates to gray paper, impermeable to actinic light, for photographic purposes, made of fibrous materials with a content of water-dispersible black pigments and / or water-soluble black dyes of 1.3 to 3.8% g / m ² . The paper is mainly used in the silver salt diffusion process. It also relates to a method for producing such a paper.

Black paper which is impermeable to actinic light and contains black pigments, in particular Soot, or black, water-soluble dyes, is known. When using for photographic Purposes, these papers have the disadvantage that for the production of an opaque, dazzling white Surface multiple white coatings must be applied. Since the weight of these coatings is Relative to the weight of the actual paper is high, these are known to have white coatings provided papers are heavy and have only a low strength.

It is also known e.g. B. according to French patent specification 14 31160, titanium pigments, e.g. titanium dioxide and / or fibrous potassium titanate, and / or finely divided magnesium silicate or aluminum oxide as Use fillers for paper.

A combination of these known types of fillers is not known

The object of the invention is to improve the known black ones while achieving a higher opacity Papers for photographic purposes by increasing their strength and reducing the proportion of black pigments and / or dyes.

This object is achieved in that a paper described at the outset is additionally used as titanium pigment 14 to 26 g / m ^{2 of} titanium dioxide and / or fibrous potassium titanate and, based on the weight of the titanium pigment, 1.5 to 15% colloidal particles of hydrous magnesium silicate or hydrous aluminum oxide contains homogeneously distributed

Papers which contain carbon black as the black pigment are particularly suitable.

In the papers according to the invention, up to 10% of the titanium pigment can be replaced by another filler be replaced, e.g. B. by sodium silicoaluminate

The particles of the magnesium silicate are preferably about 20 nm in diameter and the particles of the aluminum oxide is preferably about 30 nm in diameter.

If desired, the papers according to the invention can have a white pigmented side on the one hand Have coating. On the other hand, the paper can be rough, pigmented, against water and solvent resistant coating.

A process according to the invention for producing such papers is characterized in that an aqueous pulp of the fibrous materials forming the paper, an aqueous slurry of the titanium pigment and adding an aqueous slurry of the colloidal particles, each individually or in admixture with one another, then adding an aqueous slurry of the black pigment and / or the black dye, adjusts the slurry to an acidic pH value by adding alum and adjusts it in the usual way processed into paper and this dries.

Then, on one side of the finished paper, a white pigmented coating and optionally on the other side a rough, pigmented, water and solvent resistant coating be applied.

The papers according to the invention bring progress with them that there is already a single white one on them Coating is sufficient to provide a dazzling white surface layer required for reproduction purposes to obtain, while with the known black papers at least two such coatings are required are. This is not a simple addition of the effect of the fillers, but, as tests have shown to have a synergistic effect that is beyond the additive effect of the ingredients goes far beyond.

The examples illustrate some embodiments of the invention. Under "%" is always "weight percent" to understand.

example 1

A 2% aqueous dispersion of hydrous magnesium silicate and an aqueous 50% dispersion of titanium dioxide in rutile form containing 10% sodium silicoaluminate were prepared separately, wherein a high speed mixer was used. The dispersion of titanium dioxide contained an additional 0.3% sodium hexametaphosphate, based on the weight of the titanium dioxide, to make the dispersion to facilitate the pigment particles. The two dispersions were given in the above Sequence of a 3% slurry of sulfite kraft pulp added. This pulp became one Grind of about 350 has been refined, the grind being given in "Canadian degrees of freedom" and was determined by the TAPPI method T-227 m-58. There was 0.5% magnesium silicate and 10% of the Filler pigments added based on the weight of the fibers. Before making the opaque paper 2% cationic starch was added on a Fourdrinier machine to improve filler retention (cf. Pages 688, 689, Vol. 18, Kirk-Othmer, "Encyclopedia of Chemical Technology") and about 1% water repellant Resin glue, both based on the content of fibers. By adding alum the pH adjusted to about 4.5. Then 1.5%, based on the amount of fibers, were predispersed Add soot immediately after adding the cataeonic starch. A paper was then made according to conventional procedures made that did not contain any knots or holes. The paper was pressed and dried in the usual way. The finished paper was sized with 6% oxidized starch. Then it was calendered with a machine, in order to obtain a smooth surface for the further coatings.

The gray paper obtained had a thickness of 0.19 mm, a weight of 170 grams per square meter and contained 15.5 grams of fillers and 2.1 grams of carbon black per square meter. The fillers and the others Additives were practically completely retained by the paper because the white water was in circulation was held. The paper obtained had a uniform gray color and was completely opaque.

Examples II and III

Following the procedure of Example I, additional gray papers were made that looked similar. Different from Example I the dispersions of magnesium silicate and titanium dioxide were mixed, before they were added from the fiber suspension. Table I shows further differences.

Table I. Example II Example III

Amount of filler retained,%, calculated as ash

Opacity of the paper

Example II Example III

Thickness, millimeters 0.18 0.19 Weight, g / m ² 166 165 Fillers, g / m ² 18.4 19.0 Carbon black, g / m ² 2.36 2.5

Completely

93

Completely

60

65

Example IV

The 0.19 mm thick gray paper, which was produced according to Example I, was ^{coated on one side in an amount of 50 g / m 2} with an aqueous coating comprising 62 parts of titanium dioxide, 38 parts of barium sulfate, 10.8 parts of gelatin and 6 parts of glycerine. The sheet obtained was completely opaque and completely white on the coated side without the gray color of the paper showing through.

Example V

A gray paper according to Example II was coated in two stages in an amount of 45 g / m ² with an aqueous mixture containing 100 parts of titanium dioxide, 12 parts of gelatin and 6 parts of glycerol. The paper coated in this way was calendered again. A latex coating containing 55 parts of polyvinylidene chloride, 5 parts of titanium dioxide and 0.19 part of carbon black was applied to the opposite side of the paper in an amount of 18 g / m ^2.

Example VI

A gray paper according to Example I was coated according to Example V, with the exception that the rear The coating was 0.025 millimeters thick and made of unpigmented high density polyethylene that was applied by extrusion.

Conventional gelatin image-receiving layers were applied to the papers according to Example V and Example VI. The image receiving papers thus obtained could, in combination with an image negative, the one has an opaque coating on the back, can be used successfully in a silver salt diffusion process, developing outside of the darkroom, d. H. in the presence of actinic light. In in each case the photographic prints were satisfactory with no stains or defects by the light falling through.

Example VII

Following the procedure of Example I, a 0.2 mm thick gray paper was made. In this was the magnesium silicate replaced by 0.5% hydrous aluminum oxide. It contained 13.5% fillers, based on the weight of the fibers. The paper weighed 166 grams per square meter and contained per square meter 19.5 grams of fillers and 2.3 grams of carbon black. The fillers were retained in an amount of 93%, as emerged from the determination of the ashes. The paper produced in this way was uniformly gray and completely opaque.

Example VIII

Following the procedure of Example I, a 0.2 mm thick gray paper was made. The fillers consisted

based on 7% titanium dioxide and 7% potassium titanate on the amount of paper fiber. The paper weighed 154 grams per square meter and contained 20 grams of titanium pigments and 2.2 grams of carbon black per square meter. The filler was in a lot held by 93%. The resulting gray paper was completely opaque.

The comparison of the opacities of papers, one of which was produced according to Example I and three others were generally made in the same manner, but (A) the hydrous magnesium silicate was omitted or (B) the titanium pigment was omitted or (C) the carbon black was omitted, gave the following Results:

Paper according to example I:

clear negative, no black spots,

Paper A (no hydrous magnesium silicate):
many black spots,

Paper B (no titanium pigment): many black spots, Paper C (no soot): negative turned dark.

Claims (8)

Patent claims: 1. For actinic light opaque gray paper for photographic purposes made of fibers with a content of water-dispersible black pigments and / or water-soluble black dyes of 1.3 to 3.8 g / m ² , characterized in that the paper is also used as Titanium pigment contains 14 to 26 g / m ^{2 of} titanium dioxide and / or fibrous potassium titanate and, based on the weight of the titanium pigment, 1.5 to 15% colloidal particles of hydrous magnesium silicate or hydrous aluminum oxide, homogeneously distributed 2. Paper according to claim 1, characterized in that up to 10% of the titanium pigment by a usual filler are replaced. 3. Paper according to claim 1 or 2, characterized in that it is hydrous magnesium silicate with particle diameters of 20 nm. 4. Paper according to claim 1 or 2, characterized in that it is hydrous aluminum oxide with particle diameters of 30 nm. 5. Paper according to one of claims 1 to 4, characterized in that it is on one side has a conventional white pigmented coating. 6. Paper according to claim 5, characterized in that it is on the white pigmented coating opposite side a usual rough, pigmented, resistant to water and solvents has a permanent coating. 7. A method for producing paper according to any one of claims 1 to 4, characterized in that that an aqueous pulp of the fibrous materials forming the paper is an aqueous slurry of the titanium pigment and an aqueous slurry of the colloidal particles, by themselves or in a mixture with one another, added, then an aqueous slurry of the black pigment and / or the black dye is added, adjusted to an acidic pH value by adding alum and the slurry thus obtained is processed into paper in the usual manner and this is dried. 8. The method according to claim 7 for the production of paper according to claim 5 or 6, characterized in that that on one side of the paper the white pigmented coating and optionally on the other side the rough, pigmented, water and solvent resistant coating brings up.