Paper for photographic purposes

Abstract: A paper for photographic containing a nonionic antifoamer of which the components do not include silicone nor propylene oxide, a paper for photograph containing a nonionic mineral oil antifoamer of which the components include silicone or silicone-modified silica and having a pH of 3.5 to 5.5 measured by the cool water extracting method, and a paper for photograph which contains a water-soluble aluminum salt and at least one of rosin sizing agent, polyacrylamide or polyamide-epoxy resin and has a pH of 3.5 to 6.0 measured by the cool water extracting method. In the above papers for photograph, silicone and propylene oxide which are harmful with respect to photographic properties are removed, or propylene oxide is removed and silicone is rendered harmless by adjusting the pH to an acidic range. Or, particular sizing agent and paper strongs agent less affecting photographic properties within a particular acidic range are selected.

Description: This invention relates to a method for preparing a paper for photographic purposes, such as a packaging material for photographic photosensitive materials and a support for photographic paper. In general, unbleached kraft papers including speciality papers such as unbleached clupak paper and unbleached Duostress paper are inferior in photographic properties irrespective of the pH of the papers, for example neutral papers having a pH measured by the cool water extracting method (JIS P-8133) in the range of 6.5-9. Accordingly, unbleached kraft paper cannot be used in the portion to touch photographic photosensitive materials directly, and for example, it is used as the outer sheet of a double sheet bag shown in Japanese Patent KOKAI No. 62-53829. "Photographic properties" of a paper material means the influence of the material upon a photographic material, e.g. regarding fogging, slippage in the sensitivity and decrease in the developed density. Photographic materials are only insignificantly affected by (paper) materials having good photographic properties. It is known to wash with a great quantity of well water in the pulp washing process and the paper making process. Further, it is known to add special additives (Japanese Patent KOKOKU No. 58-43730) and to remove or stabilize harmful substances affecting photographic properties. RO 88160 describes antifoaming agents useful in pulp, paper and leather processing, containing polyethyleneglycol (a nonionic surfactant), polyethoxylated ricinoleic triglyceride (i.e., a fatty acid compound), 16 to 18 fatty alkyl ethers, a liquid hydrocarbon and water. JP-A-75 059503 relates to pulp slurries containing a polyacrylamide in admixture with nonionic surfactants having an HLB of less than 12, fatty acids and fatty acid amides and/or fatty amines. From US-A-4107073 an antifoam composition useful in pulping and paper making processes is known which consists of a water-based emulsion comprising amongst other components silica and paraffin oil. US-A-3592731 and DE-C-3606806 relate to a photographic paper base comprising fatty acid and/or fatty acid salts and aluminium salts as well as anionic and cationic polyacrylamide and an epoxy fatty acid amide, the pH value of the paper pulp being in the range of 3.5 to 5. Double sheet bags are expensive and their workability in a dark room is inferior, since the space between the outer sheet and the inner sheet is liable to be opened by hand instead of opening the inner sheet. Furthermore, the photographic properties of unbleached kraft paper, e.g. improved by adding a special additive, are still not sufficient. On the other hand, bleached kraft paper has excellent photographic properties, and can be used as a single sheet bag. However, it is expensive, and physical strength such as surface strength is insufficient. It is the object of the invention to provide an inexpensive paper for photographic purposes which has excellent photographic properties and physical strength. The inventors investigated the influences of various additives added through the manufacturing process of unbleached kraft paper, and found that certain antifoaming agents adversely affect the photographic properties. In the prior art the antifoaming agent used in the washer process of the manufacturing process of unbleached kraft paper is a nonionic mineral oil of which the principal component is silicone, and the antifoaming agent used in the screening process and in the mixer process is a nonionic surfactant of which the principal component is propylene oxide. The inventors found that the silicone and propylene oxide remained in the kraft paper, and affected the photographic properties. Thus, the present invention provides a method of preparing a paper comprising subjecting unbleached kraft pulp to a washer process with a nonionic mineral oil antifoamer containing no silicone, then subjecting the thus obtained pulp to a screening process and to a mixing process with a nonionic surfactant antifoamer containing no propylene oxide. Moreover, the inventors found that, when the nonionic surfactant of which the principal component is propylene oxide was absent, the adverse affect of silicone could be eliminated by adjusting the pH [measured by the cool water extracting method (JIS P-8133)] to 3.5 to 5.5. The present invention therefore further provides a method of preparing a paper comprising subjecting unbleached kraft pulp to a washer process with a nonionic mineral oil antifoamer containing silicone or silicone-modified silica and then subjecting the thus obtained pulp to a screening process and a mixer process with a nonionic surfactant antifoamer containing no propyleneoxide wherein the pH value of the paper stock is adjusted to 3.5. to 5.5. A sizing agent and a paper strengthening agent are generally added in order to improve the surface strength and delamination resistance of a paper. Further a water-soluble aluminum salt is added in order to improve the retention of the sizing agent and the paper strengthening agent. However, when the quantity of the water-soluble aluminum salt is increased in order to improve the retention effectively, the manufactured paper is rendered acidic, and the photographic properties become worse. The inventors investigated the influences of various sizing agents and paper strengthening agents, and found that certain sizing agents and paper strengthening agents do not adversely affect the photographic properties under acidic conditions, though they adversely affect said properties under neutral conditions. This means that rosin sizing agents and paper strengthening agents of polyacrylamides and polyamide-epoxy resins do not adversely affect photographic properties within the pH range of 3.5. to 6.0. Therefore, the present invention additionally provides a method of preparing a paper comprising adding to unbleached kraft pulp a water-soluble aluminium salt and at least one of a rosin sizing agent, a polyacrylamide and a polyamide-epoxy resin, and adjusting the pH value of the paper stock to 3.5 to 6.0. The paper obtained according to the methods of the present invention can be used for photographic purposes, such as a packaging material for photographic photosensitive materials, light-shielding paper, support for photographic papers, pads, carton boxes, cores, guard sheets, leader paper and materials for composing instant photographs. The nonionic antifoaming agent, which does not contain silicone or propylene oxide, includes mixtures of a nonionic surfactant and a fatty acid and/or a fatty acid compound such as a fatty acid amide, a fatty acid ester or a fatty acid metal salt, mixtures of a polyglycol and a fatty acid and/or fatty acid compound such as a fatty acid amide, a fatty acid ester or a fatty acid metal salt, emulsifying pine oils, and nonionic fatty acids. Preferable nonionic antifoaming agents are mixtures of a nonionic surfactant and a fatty acid compound, and particularly preferred nonionic antifoaming agents contain a mixture of anonionic surfactant and a fatty acid amide as the principal component. Polyoxyethylene sorbitan laurate is also particularly preferred. Preferable nonionic surfactants contain halides of hydrocarbons or a mixture thereof as the principal component. The silicones harmful for photographic properties are, for example, diorganopolysiloxanes, polyoxyalkylene-modified polysiloxanes, dimethylpolysiloxanes, dimethyldichlorosilane, diethylpolysiloxanes, methylphenylpolysiloxanes, polydimethylpolydiphenylsiloxane copolymers, polymethyl-3,3,3,-trifluoropropylsiloxanes and polydimethylchloropropylmethylsiloxanes. Propylene oxide also called 1,2-epoxypropane is reactive, and it is e.g. miscible with water and ethanol. When propylene oxide is heated with alumina, it produces propionaldehyde which adversely affects photographic photosensitive materials. In the first method of the present invention, a suitable quantity of the antifoaming agent is in the range of 10 to 1500 g/pulp ton in the pulp washer process, 5 to 600 g/pulp ton in the pulp screening process and less than 1 % per pulp weight in the mixer process. The paper for photographic purposes obtained according to the first method of the present invention does not adversely affect photographic photosensitive materials regardless of the pH thereof, because the antifoaming agent does not contain silicone or propylene oxide which otherwise cause sensitivity slippage and fogging. This paper is inexpensive, and its physical strength is great. The nonionic mineral oil antifoaming agent used in the second method of the present invention contains silicone or silicone-modified silica and a nonionic surfactant. The silicone may be selected from those mentioned previously, and the silicone-modified silica is a fine powder of silica treated with the silicone. A particularly preferred nonionic mineral oil antifoaming agent is polyoxyalkylene-modified polysiloxane blended with dimethylpolysiloxane, silica and a nonionic surfactant in view of excellent foam-extinguishing ability and foam-breaking ability. A suitable quantity of the nonionic mineral oil antifoaming agent is in the range of 100 to 1000 g(stock solution)/pulp ton. When the quantity is less than 100 g/pulp ton, the foam-extinguishing effect is insufficient. On the other hand, when the quantity is beyond 1000 g/pulp ton, the photographic properties are adversely affected. In the above paper for photographic purposes obtained according to the second method of the present invention, the adverse affects of silicone and silicone-modified silica upon the photographic properties are reduced by adjusting the pH within the prescribed range, and necessary foam-extinguishing effects in the paper manufacturing process are secured by the silicone or silicone-modified silica. When the nonionic mineral oil antifoaming agent is used, the pH measured by the cool water extracting method (JIS P-8133) is adjusted to 3.5 to 5.5. When the pH is lower than 3.5, the increase of sensitivity is great. On the other hand, when the pH is higher than 5.5, the increase of sensitivity is also great. The pH is adjusted by the quantity of additives, such as aluminum sulfate. An acid, such as chloric acid, sulfuric acid, citric acid or oxalic acid, may be added, if necessary. According to the third method of the present invention, a water-soluble aluminum salt and at least one of a rosin sizing agent, a polyacrylamide and a polyamide-epoxy resin are used. Therein the water-soluble aluminum salt is added for fixing the sizing agent and the paper strengthening agent on the fibers of the pulp. Examples of the water-soluble aluminum salt are aluminum sulfate, aluminum chloride, poly(aluminum chloride) and poly(aluminum hydroxide). The quantity of the water-soluble aluminum salt is determined so that the pH measured by the cool water extracting method (JIS P-8133) of the paper for photographic purposes is within the range of 3.5 to 6.0. It is for example influenced by the pH of the pulp, the quantity of various additives and the kind of the water-soluble aluminum slat. A usual quantity of the water-soluble aluminum salt is 0.5 to 10 wt. %, preferably 1 to 6 wt. %, of the dry weight of pulp. The rosin sizing agents are divided into three groups, which are gum rosin, tall oil rosin and wood rosin. Maleic anhydride or fumaric anhydride is added to the rosin with heating to produce maleinized rosin or fumaric-induced rosin. An alkali is added to obtain a solution of a fortified rosin sizing agent. The maleinized rosin or fumaric-induced rosin is suspended in water with an emulsifier to obtain an emulsion-type rosin sizing agent. Polyacrylamide acts as a paper strengthening agent, and exhibits additional effects such as the improvement in the fixation of fillers and fine fibers and the improvement in drainage ability. In order to improve the fixation to the pulp, a part of the amide groups is changed to carboxyl groups. The carboxyl group-induced polyacrylamide is fixed on the fibers of the pulp through aluminum sulfate. In order to obtain a suitable modification rate of the polyacrylamide, about 10 % of the amide groups are changed to carboxyl groups. Polyamide-epoxy resin is used as a non-formaldehyde resin. It exhibits a high ability as a wet paper strengthening agent. The quantity of the rosin sizing agent, polyacrylamide and polyamide-epoxy resin is suitably 0.05 to 10 wt. %, preferably 0.2 to 5 wt. %, of the dry weight of the pulp. The pH measured by the cool water extracting method (JIS P-8133) is 3.5 to 6.0. When the pH is lower than 3.5, the increase of sensitivity is great. On the other hand when the pH is higher than 6.0, the increase of sensitivity is also great. The pH is adjusted by the quantity of additives, such as aluminum sulfate. An acid, such as chloric acid, sulfuric acid or oxalic acid, may be added, if necessary. In the paper for photographic purposes obtained according to the third method of the present invention, the water-soluble aluminum salt improves the retention of the sizing agent and the paper strengthening agent, and adjusts the pH within the range of 3.5 to 6.0. The rosin sizing agent, polyacrylamide and polyamide-epoxy resin improves the surface strength. The adjustment of the pH within the range of 3.5 to 6.0 renders compounds, such as the rosin sizing agent, harmless for the photographic properties. As indicated above, the paper for photographic purposes, obtained according to the methods of the invention is used for packaging materials for photographic photosensitive materials, light-shielding paper, support for photographs, pad, carton box, core, guard sheet, leader paper and materials for composing instant photographs. Preferably, the paper is used as the inner surface layer of the laminated film formed in a single sheet bag to touch the emulsion face of the photosensitive materials. In the following, the invention is described in more detail by way of examples. Example 1 A nonionic antifoaming agent containing a fatty amide and silicone as the principal components ("PRONAL K -302N", trade name) was rendered water-soluble by removing the silicone. An unbleached kraft pulp was prepared wherein 500 g/pulp ton of the above nonionic antifoaming agent were added in the pulp washer process and 200 g/pulp ton of the same antifoaming agent was further added in the pulp screening process of the pulp washing process. The unbleached kraft pulp was beaten up to a CPPA standards drainage rate of 450 ml to produce a pulp slurry. Polyacrylamide was added to the pulp slurry in an amount of 1.0 wt. % of the pulp and aluminum sulfate was added in an amount of 3.0 wt. % of the pulp. A handmade paper of pH 4.5 having an areal weight of 70 g/m 2 was prepared from the above paper stock by using a TAPPI type handmaking machine. Example II A paper was prepared as in Example 1, except that the amount of aluminum sulfate was 0.3 wt. % of the pulp and the pH was adjusted to 7.2. Comparative Example I An unbleached kraft paper of pH 4.3 was prepared in the same manner as in Example I, except that 500 g/pulp ton of the nonionic antifoaming agent ("PRONAL K-302N") without the water-solubilization treatment was added in the pulp washer process of the pulp washing process instead of the water-soluble antifoaming agent obtained from "PRONAL K-302N" in Example I. Further, 200 g/pulp ton of a nonionic antifoaming agent containing propylene oxide and ethylene oxide as the principal components ("PRONAL S-121", trade name) were added in the process instead of 200 g/pulp ton of the water-soluble antifoaming agent. Comparative Example II An unbleached kraft paper of pH 7.0 was prepared in the same manner as in Comparative Example I before and in the pulp washer process, and in the same manner as in Example II after the pulp washer process. The photographic properties and surface strength of the above products were measured. The results are summarized in Table 1. Invention Comparative I II I II pH of Paper 4.5 7.2 4.3 7.0 Acidic Neutral Acidic Neutral Photographic Properties (Contact) Slippage in Sensitivity of Green Coloring Layer 0 0 +0.02 +0.02 Slippage in Sensitivity of Blue Coloring Layer +0.01 0 +0.04 +0.04 Slippage in Sensitivity of Red Coloring Layer 0 0 +0.03 +0.03 Surface Strength (Wax No.) 12A 10A 12A 10A Test Method: pH of Paper: Measured by the cool water extracting method according to JIS P-8133 Photographic Properties (Contact): The emulsion face of a color photographic printing paper was contacted with the handmade paper, and kept at 50°C for 3 days without humidity conditioning. Then, each photographic printing paper was developed in a conventional manner, and each color concentration was measured by using a densitometer. Each numerical value in the table is the difference do the value of the paper not contacted with the reagent. Surface Strength: Measured according to JIS wax method of JIS P-8129 Example III 500 g/pulp ton of a nonionic antifoaming agent ("PRONAL K-302N") was added to an unbleached kraft pulp, and the unbleached kraft pulp was beaten up to a CPPA standards drainage rate of 450 ml. The pH measured by the cool water extracting method (JIS P-8133) of the beaten pulp was adjusted to 4.5 by adding aluminum sulfate. A handmade unbleached kraft paper having an areal weight of 70 g/m 2 was prepared from the above paper stock by using a TAPPI type handmaking machine. Comparative Example III An unbleached kraft paper prepared in the same manner as the product of Example III, except that the pH of the beaten pulp was adjusted to 7.0 by adding aluminum sulfate. The photographic properties of the above products were measured, and the results are shown in Table 2. Invention III Comparative III pH of Paper 4.5 7.0 Photographic Properties (Contact) Slippage in Sensitivity of Blue Coloring Layer +0.01 +0.05 Slippage in Sensitivity of Green Coloring Layer 0 +0.03 Slippage in Sensitivity of Red Coloring Layer 0 +0.02 Photographic Properties (Gas) Slippage in Sensitivity of Blue Coloring Layer 0 +0.02 Slippage in Sensitivity of Green Coloring Layer +0.01 +0.02 Slippage in Sensitivity of Red Coloring Layer 0 +0.01 Test Method: Photographic Properties (Gas): The emulsion face of a color photographic printing paper was faced to the handmade paper through a perforated sheet, and kept at 50°C for 3 days without humidity conditioning. Then, each photographic printing paper was developed in a conventional manner, and each color concentration was measured by using a densitometer. Each numerical value in the table is the difference to the value of the paper not contacted with the reagent. Example IV An unbleached kraft pulp was beaten up to a CPPA standards drainage rate of 450 ml by a mill, and to the beaten pulp was added 0.3 wt. % of a rosin sizing agent (fortified rosin sizing agent), 2 wt. % of an anionic polyacrylamide as the paper strengthening agent and 3 wt. % of aluminum sulfate as the water-soluble aluminum salt. A handmade paper of pH 4.5 (measured by the cool water extracting method of JIS P-8133) having an areal weight of 70 g/m 2 was prepared from the above paper stock by using a TAPPI type handmaking machine. Comparative Example IV This paper was a handmade paper of pH 7 measured by the cool water extracting method prepared in the same manner as the product of Example IV, except that the amount of aluminum sulfate was changed to 1.5 wt. %. Comparative Example V A handmade paper of pH 7 measured by the cool water extracting method was prepared in the same manner as the product of Example IV, except that the amount of aluminum sulfate was changed to 1.5 wt. % and that polyacrylamide was not added. Comparative Example VI A handmade paper of pH 4.5 measured by the cool water extracting method was prepared in the same manner as the product of Example IV, except that 2 wt. % of a melamine resin was added instead of polyacrylamide. Example V A handmade paper of pH 4.7 (measured by the cool water extracting method) having an areal weight of 70 g/m 2 was prepared in the same manner as the product of Example IV, except that no rosin-sizing agent was added. Comparative Example VII A handmade paper of pH 4.6 (measured by the cool water extracting method) was prepared in the same manner as the product of Example V, except that 2 wt. % of modified starch ("PEPARIN", trade name) was used instead of polyacrylamide. The photographic properties of the above products were measured, and the results are shown in Table 3. Invention Comparative Invention Comparative IV IV V VI V VIII pH of Paper 4.5 7.0 7.0 4.5 4.7 4.6 Photographic Properties (Contact) Slippage in Sensitivity of Green Coloring Layer +0.01 +0.08 +0.04 +0.05 +0.01 +0.03 Slippage in Sensitivity of Blue Coloring Layer 0 +0.06 +0.05 +0.07 +0.02 +0.03 Slippage in Sensitivity of Red Coloring Layer +0.01 +0.03 +0.02 +0.06 +0.01 +0.07

Claims: A method of preparing a paper comprising subjecting unbleached kraft pulp to a washer process with a nonionic mineral oil antifoamer containing no silicone, then subjecting the thus obtained pulp to a screening process and to a mixing process with a nonionic surfactant antifoamer containing no propyleneoxide. The method according to claim 1 wherein said nonionic mineral oil antifoamer is present in an amount of 10 to 1500 g/pulp ton in the pulp washer process and said nonionic surfactant antifoamer is present in an amount of 5 to 600 g/pulp ton in the screening process. A method of preparing a paper comprising subjecting unbleached kraft pulp to a washer process with a nonionic mineral oil antifoamer containing silicone or silicone-modified silica and then subjecting the thus obtained pulp to a screening process and a mixer process with a nonionic surfactant antifoamer containing no propyleneoxide wherein the pH value of the paper stock is adjusted to 3.5 to 5.5. The method of claim 3 wherein the quantity of the antifoamer is 100 to 1000 g (stock solution)/pulp ton. A method of preparing a paper comprising adding to unbleached kraft pulp water-soluble aluminium salt and at least one of a rosin sizing agent, a polyacrylamide and a polyamide-epoxy resin, and adjusting the pH value of the paper stock to 3.5 to 6.0. The method of claim 5 wherein the quantity of the water-soluble aluminium salt is 0.5 to 10 wt. %, of the dry weight of the pulp, and the quantity of the rosin sizing agent, polyacrylamide and the polyamide-epoxy resin is 0.05 to 10 wt. % of the dry weight of the pulp. The use of an unbleached kraft paper containing a nonionic antifoamer which does not include silicone and propyleneoxide for photographic purposes. The use of an unbleached kraft paper containing a nonionic mineral oil antifoamer which includes silicone or silicone-modified silica and which has a pH value of 3.5 to 5.5 measured by the cool water extracting method (JIS P-8133) for photographic purposes. The use of an unbleached kraft paper which contains a water-soluble aluminium salt and at least one of a rosin sizing agent, a polyacrylamide or a polyamide-epoxy resin and which has a pH value of 3.5 to 6.0 measured by the cool water extracting method (JIS P-8133) for photographic purposes. The use of any one of claims 7 to 9 wherein the paper is used as a packaging material for photographic photosensitive materials, light-shielding paper, support for photographic papers, pads, carton boxes, cores, guard sheets, leader paper and materials for composing instant photographs.

Inventors: AKAO MUTSUO, INOUE KOJI, AKAO, MUTSUO, INOUE, KOJI
Applicants: FUJI PHOTO FILM CO LTD, FUJI PHOTO FILM CO., LTD.
Application year: 1989
Main classification: G03C1
IPC codes: G03C1, D21H21