Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
1999-04-23
2001-04-03
Lee, Howard C. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S063000, C536S069000, C536S124000
Reexamination Certificate
active
06211358
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method for preparing a solution of cellulose acylate to be used for producing a cellulose acylate film suitable for silver halide photographic light-sensitive material and liquid crystal image display device. The invention also relates to a cellulose acylate film produced by such method. A chlorinated carbon hydride such as methylene chloride is usually used in a solution of cellulose triacetate for producing a cellulose triacetate film for silver halide photographic light-sensitive material or a liquid crystal image displaying device. Methylene chloride (boiling point: 41° C.) is usually used as a suitable solvent for cellulose triacetate, because it has a low boiling point and is easily dried in the casting and drying processes in the course of the film production. Recently, however, the use of chlorinated compounds has become regulated. Accordingly, a production method of cellulose triacetate film using no methylene chloride is required. Acetone (boiling point: 56° C.), methyl acetate (boiling point: 56.3° C.), tetrahydrofuran (boiling point: 65.4° C.), 1,3-dioxolan (boiling point: 75° C.), nitromethane (boiling point: 101° C.), 1,4-dioxane (boiling point: 101° C.), epichlorohydrin (boiling point: 116° C.), and N-methylpyrrolidone (boiling point: 202° C.) are other known solvents capable of dissolving cellulose triacetate. However, according to results of practical dissolving experiments, these organic solvents have various disadvantages including explosive fumes and high boiling point.
Among the above-mentioned, acetone, although having a low boiling point, cannot dissolve cellulose triacetate by ordinary methods even though it swells the cellulose triacetate. Recently, it has been attempted to dissolve cellulose triacetate in acetone for producing fiber or film.
C. M. G. Cowie et al. report in “Die Makromolekulare Chemie”, 135, p.p. 105-114, 1971 that a dilute solution having a concentration of from 0.5 to 5% by weight can be obtained by chilling a mixture of cellulose triacetate (acetalized degree of 60.1 to 61.3%) and acetone at a temperature of from −80° to −70° C. and thereafter heating the mixture. Such method for dissolving at a low temperature is called a chilling dissolving method. Kamide Kenji et al. described a spinning technology using the chilling dissolving method in “Dry Spinning from an Acetone Solution of Cellulose Triacetate” Seni Kikai Gakkai Shi vol. 34. No. 7, p.p. 57-61, 1981.
In Japanese Patent Publication Open to Public Inspection, herein after referred to as JP O.P.I., Nos. 9-95544 and 9-95557, it is proposed, based on the above-mentioned technology, to dissolve cellulose triacetate by the chilling dissolving method using a solvent substantially composed of acetone or a mixture of acetone and another organic solvent and to use the resulting solution for producing a film.
JP O.P.I. No. 9-95538 describes a film produced by the use of a solution in which cellulose triacetate is dissolved by the chilling dissolving method in a solvent selected from ethers, ketones and esters other than acetone. Preferred solvents are 2-methoxyethyl acetate, cyclohexane, ethyl formate and methyl acetate.
In JP O.P.I. No. 10-45804, a mixed fatty acid ester of cellulose capable of being dissolved in a solvent such as acetone and methyl acetate is proposed, in which an acetyl group and an acyl group having 3 or more carbon atoms have a specific relation.
The cellulose triacetate film cast from the cellulose triacetate solution which is prepared by the chilling dissolving method has problems such as inferior flatness and high haze, both of which have large fluctuations.
Moreover, the viscosity of solution prepared by the chilling dissolving method cannot be controlled suitably, and the viscosity of the solution is too high to be transported through piping for the casting thereof. Accordingly film formation is difficult since high pressure is necessary to transport the solution.
Cellulose acylate having a high substitution degree of the acyl group other than the acetyl group is insufficient in the physical properties. Therefore, as a practical matter, cellulose acetate having a low substitution degree of acyl groups can only be used. When the substitution degree of the acyl group is high, a specific dissolving method such as the chilling dissolving method is not necessary. However, when the substitution degree of the acyl group is low, the chilling dissolving method is necessary to dissolve it, and the above-mentioned problems remain.
Generally, a cellulose triacetate film is produced by a method called a “solution casting method” in which a solution of cellulose triacetate is cast on a substrate endlessly run and peeled, and the solvent is evaporated from the formed web. When the viscosity of the solution to be cast is excessively high, leveling of the solution on the substrate is insufficient, and in an extreme case the surface of the film is rough. Thus a film inferior in flatness is formed. Usually, a cellulose acylate solution having a viscosity within the range of from 0.5 Pa-s (5 pois) to 50 Pa-s (500 pois) is preferable for obtaining a cellulose triacetate film having a good flatness. The viscosity of cellulose acylate solution can be lowered by decreasing the polymerization degree of cellulose acylate or lowering the concentration of the solution. However, such means is difficult to apply for practical use since the film produced by such method has less mechanical strength and requires a great deal of time and energy to evaporate the solvent. Japanese Patent No. 61-40095 describes that the film formation can be easily performed by reducing the content of alkali-earth metal such as calcium and magnesium to not more than 30 ppm of the cellulose acetate because the viscosity of the solution obtained by dissolving the cellulose acetate at ordinary pressure and temperature using methylene chloride as an organic solvent, is considerable lowered. Although there is no description regarding the haze in this publication, it has been found as a result of experiments by the inventor using a chilling dissolving method that a cellulose acylate solution containing alkali-earth metal in an amount more than a certain value tends to be easily made turbid and the film made from such solution has a high haze. To limit the use of the chlorinated solvent as low as possible, it is necessary to solve the problems that a dope prepared by the use of an organic solvent such as acetone tends to be turbid, the film formed from such dope has a high haze and the turbidity and the haze can vary. The resolution of such the problems is important if one is to utilize the chilling dissolving method.
The object of the invention is to provide a production method of a cellulose acylate solution low in turbidity, using a non-chlorinated solvent rather than chlorinated solvents such as methylene chloride, and to provide a cellulose acylate film having a considerably low haze and excellent in the transparency; and production method using the solution.
The inventors found according to their study on the preparation method in which cellulose acylate can be sufficiently dissolved in a non-chlorinated solvent and the solution using the solvent has hardly any haze, and their study on a cellulose acylate transparent film having a low haze and a producing method therefor, that the content of alkali-earth metal in cellulose acylate relates to the turbidity and the haze, and the instability the turbidity and the haze is dependent on the content.
SUMMARY OF THE INVENTION
The object of the invention can be attained by a method for preparing a solution of cellulose acylate comprising the steps of
chilling a first organic solvent containing substantially no chlorinated organic solvent at a temperature of from −100° C. to −10° C.,
mixing cellulose acylate containing an alkali-earth metal compound in an amount of from 10 ppm to 100 ppm with said chilled first organic solvent to form a mixture,
swelling the cellulose acylate in the mixture, and
dis
Honda Makoto
Yajima Takatoshi
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Konica Corporation
Lee Howard C.
LandOfFree
Method for preparing solution of cellulose acylate method... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for preparing solution of cellulose acylate method..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for preparing solution of cellulose acylate method... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2442325