JPS6027562B2 - Method for manufacturing cellulose acetate film - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing cellulose acetate film using a solution casting method. More specifically, one layer is formed by casting from two casting ports,
The present invention relates to a method for increasing the production rate of cellulose acetate film. In the conventional method of obtaining a cellulose acetate film by casting a solution from a single casting port onto a smooth band or drum-shaped casting surface, the drying process on the casting surface is rate-limiting, and the production rate is slow. This limits us. That is, unless the side of the cast solution in contact with the casting surface is completely dried and solidified, it cannot be peeled off from the casting surface. In addition, rapid drying causes foaming in the cast layer to promote evaporation of the solvent, and if the cast layer is peeled off in a dry state, residual peeling occurs on the cast surface, causing the flatness of the film to deteriorate. This may lead to negative effects such as impairing transparency and transparency. Therefore, this method has the disadvantage that the manufacturing speed is extremely slow. 2
In the solution casting method, which is carried out using two casting ports, the film formed on the support is peeled off using the first casting port, and a second casting is performed on the side that was in contact with the support surface. Japanese Patent Publication No. 44-20235 discloses a method of removing defects on the surface of a film due to cloudiness, scratches, pinholes, etc., and obtaining a film that is smooth on both the front and back surfaces and has optical properties. However, in such a method, even if small defects are removed by the second casting, non-uniform expansion occurs and large irregularities appear on the film, making it impossible to produce a high-quality film. As a result of intensive research into increasing the manufacturing speed of cellulose acetate film without impairing its quality, the present inventors used two casting holes on the same support surface to dry the first casting layer. A second casting is performed before peeling off from the support surface.
The above objective could be fully achieved by obtaining a fused single film. In the method according to the present invention, compared to the conventional method of obtaining a film using one casting port, the drying efficiency of the film on the support surface is increased, and furthermore, the method of the present invention improves the drying efficiency of the film on the support surface, and furthermore, Since it can be peeled off, it has become possible to significantly increase manufacturing speed. More surprisingly, the film produced by this method is peeled from the support surface with a considerable amount of solvent contained inside the film, and after drying, the plasticizer distribution in the thickness direction of the film is uniform; Furthermore, the curling of the film was significantly improved. The drawing shows a sectional view of the apparatus used in the method according to the invention. In the figure, 1 is the first casting port, 2 is the layer cast from the first casting port, 3 is a support that moves in the direction of the arrow, 4 is the second casting port, and 5 is the layer cast from the second casting port. The spread layer, 6 is the synthesized coating, and 7 is the peeling position of the cast coating from the support. In the method according to the present invention, first, a cellulose acetate solution is uniformly cast onto the surface of the support 3 moving from the first casting port 1. The cast solution 2 is moved together with the support 3 and dried. The cellulose acetate solution is further cast onto the cast layer 2 through the second casting port 4 without peeling off the cast layer 2. The synthesized film 6 is fused into a single film by the action of the solvent, moves with the support 3, evaporates the solvent contained therein, and, after becoming peelable from the support 3, reaches the peeling position 7 of the cast film. In this step, the cellulose acetate film is peeled off from the support 3 and dried from both sides to obtain a cellulose acetate film. In addition, 8 is a peeling roll. A first object of the present invention is to provide a method for producing a cellulose acetate film using a solution casting method, and to provide a means for significantly increasing the production rate. A second object of the present invention is to provide a means for producing a high-quality cellulose acetate film with little curl. A third object of the present invention is to provide a means for producing a high-quality photographic film base with good flatness. A further object of the present invention is to provide a method for producing a cellulose acetate film by casting a cellulose acetate solution from two casting ports on the same support surface, in which the cellulose acetate solution is cast from a first casting port onto the support surface. Casting an amount equivalent to 10 to 90% of the final finished film thickness,
After drying and before peeling from the support surface, an amount of cellulose acetate corresponding to the amount remaining at a position separated from the first casting port by a distance of 30 to 60% of the distance between the first casting port and the peeling position. The solution is cast onto the layer formed by casting from the first casting port, dried until it can be peeled from the support surface, and the amount of residual solvent relative to cellulose acetate in the fused cast layer is 8.
This can be achieved by peeling off from the surface of the support at a weight % of at least . The support referred to in the present invention is shown in the drawing as a structure consisting of an endless band and two drums, but this may include other types,
For example, it may be one drum or the like. There is no limit to the type of the two casting ports used in the present invention,
All types of casting ports commonly used in solution casting methods, such as slit die and doctor types, apply to each. The cellulose acetate solution according to the present invention consists of a cellulose acetate plasticizer and an organic solvent for dissolving these. Cellulose acetate includes cellulose triacetate and the like, and preferably has a bound acetic acid content of 60 to 62%. Phosphate ester plasticizers include triphenyl phosphate, tricresyl phosphate, triethyl phosphate, biphenyl diphenyl phosphate, and phthalate ester plasticizers such as dimethyl phthalate, diethyl phthalate, and dimethoxylate. Glycolic acid esters such as tylphthalate, ethyl phthalylethyl glycolate, toluenesulfonamide, triacetin, etc. are used alone or in combination. Moreover, the plasticizer content is preferably 5 to 3% by weight based on cellulose acetate. As the organic solvent, a chlorinated hydrocarbon, preferably methylene chloride is used as the main solvent,
As a subsolvent, a saturated aliphatic alcohol having 1 to 6 carbon atoms, preferably methanol, ethanol, n-propanol, isopropanol. /Zenol, n-butanol, isoptanol, sec
-butanol, tert-butanol, n-hexyl alcohol, etc. Furthermore, carbon compounds having 3 to 7 carbon atoms and cyclic aliphatic hydrocarbons, preferably cyclohexane, methylcyclohexane, etc. Fatty acid esters include ethyl acetate,
Propyl acetate, etc. Ketones include methyl ethyl ketone, methyl isobutyl ketone, etc., and ethers include methylcetate. There are mixed solvents that are a mixture of one or more selected from Solv, tetrahydrofuran, etc., and aromatic hydrocarbons having 6 carbon atoms, preferably benzene, monochlorobenzene, etc. The proportion of the organic solvent in the cellulose acetate solution is about 75 to 95% by weight, preferably 80 to 92% by weight. Further, it is preferable that the proportion of the main solvent chlorinated hydrocarbon in the organic solvent is 70 to 95% by weight as a standard. Preferred organic solvent composition examples for the cellulose acetate solution used in the present invention are shown below, but the present invention is not limited thereby. (The numbers in parentheses are
Indicates weight %. ) {1) Methylene chloride (70-9
5) 10 methanol (5-30) '21 Methylene chloride (70-95) + Koyu/ru (5-30) '3} Methylene chloride (70-9
0) 10 methanol + (5-15) 10 cyclohexane (5
~15)

[41 methylene chloride (70-90) ten ethanol (5-15) ten cyclohexane (5-15) [51 methylene chloride (80-93) ten methanol (2-7) ten n-butanol (5-13) [6l Methylene chloride (80-93) 10-ethanol (2-7) 10-n-butanol (5-13) '71 Methylene chloride (80-93) 10-methanol (2-7) 10-isobutanol (5-13) [8} Methylene Chloride (80-93) Decetaethanol (2-7) Decisobutanol (5-13) The casting amount per unit time of the cellulose acetate solution diluted by the first casting port in the present invention is a, It is cast through two casting ports. The amount of cellulose acetate solution cast per unit time is b
If this is the case, then the shoe side hoe/first casting will be a point, and the second casting will be a point, which contributes to the thickness of the finished film, but in the present invention, it will be 0. 1～〇. 9 (therefore, points = 0.9 to 0.1) are applied. More preferably, for the layer formed by casting the cellulose acetate solution used in the second casting in the first casting,
If it has so-called solubility, the score is 〇. ４〜〇． 8(
Therefore, Ken = 〇. 6～〇. It is best to apply within the range of 2), where pseudo-points with no solubility = 0. 2～〇． It is best to apply it in the range of 6 (therefore, heat = 0.8 to 0.4). The organic solvent composition in which the cellulose acetate solution cast from the second casting port has a dissolution chamber relative to the first casting layer includes methylene chloride (87-95% by weight), methanol or ethanol (5-95% by weight). 13% by weight). In addition, for the organic solvent composition of the cellulose acetate solution that does not have dissolving ability, the above-mentioned organic solvent composition examples '1' and '21
There are also those containing methanol or ethanol of 1% by weight or more, and those containing a third component other than methylene chloride, methanol, and ethanol as shown in (3) to (■). The second casting port in the method is preferably located at a distance from the first casting point that is 30 to 60% of the distance between the first casting point and the separation point. The solutions used in the first and second casting may be the same solution or different solutions.In the method of the present invention, the autumn festival in which the casting layer is peeled from the support surface;
Although it can be removed with a large amount of residual solvent,
The object of the present invention is effectively achieved when the amount of solvent remaining relative to cellulose acetate is 8% by weight or more. The finished cellulose acetate film obtained by the method of the present invention has a thickness of 0.5 or less, more preferably 0.5 or less.
It is best to have 3 shelves or less. In the present invention, there are no restrictions on drying the cast layer after it has been peeled off from the support, and a conventional method of drying from both sides can be applied. Furthermore, it is also possible to dry the peeled layer without shrinking it by using a tenter or closely arranging rolls. The effects of the present invention will be shown below in Examples. Example 1 - 10 pieces of cellulose acetate (combined acetic acid amount: 61.4%) were dissolved in a mixed organic solvent of 55 parts of methylene chloride, 65 parts of methanol, and 65 parts of cyclohexane, and triphenyl fluoride was added to this solution. After adding and dissolving 15 parts of eight, the mixture was filtered and defoamed to prepare a cellulose acetate solution. The above cellulose acetate solution was cast in the following ratio and amount through two casting holes located on six endless stainless steel strips installed in two drums, and after peeling off the cast layer from the stainless steel strip. The drying process was completed while being conveyed by a number of rolls, and a cellulose acetate film having a thickness of 40 mm was produced. The distance between the first casting hole and the peeling point was about the same as a shoe, and the second casting hole was positioned exactly in the middle of the distance between the first casting hole and the peeling point. The ratio of the amount of cellulose acetate solution cast from the first and second casting ports contributing to the final finished film thickness of 140 µm and the maximum film forming speed in each case are shown. As is clear from this example, the method according to the present invention achieved a film forming rate more than twice that of the conventional single-layer casting method. Further, the film after drying had little curl, had good flatness, and was satisfactory as a base for a photographic support. Example 2 Cellulose acetate (combined acetic acid amount 6
1.4%) 10 parts were dissolved in a mixed organic solvent of 52 parts of methylene chloride and 13 parts of methanol, and 15 parts of triphenyl phosphate was added to this solution and dissolved.
Filtration and defoaming were performed to prepare a cellulose acetate solution. A cellulose acetate film was produced using the cellulose acetate solution in the same manner as described in Example 1. The results are shown below. The film after drying had little curl and good flatness. In this example, almost the same results were obtained even when ethanol was used instead of methanol. Example 3 10 parts of cellulose acetate (combined acetic acid amount: 61.4%) was dissolved in a mixed organic solvent of 61 parts of methylene chloride and 40 parts of methanol, and 15 parts of triphenyl phosphate was added to this solution. After dissolution, filtration and defoaming were performed to prepare a cellulose acetate solution. A cellulose acetate film was produced using the cellulose acetate solution in the same manner as described in Example 1. The results are shown below. The film after drying had little curl and had good flatness. In this example, almost the same results were obtained even when ethanol was used instead of methanol. Example 4 10 parts of cellulose acetate (combined acetic acid amount 61.4%), 55 parts of methylene chloride, 30 parts of methanol,
The mixture was dissolved in a mixed organic solvent containing 65 parts of n-butanol, and 15 parts of triphenyl phosphate was added and dissolved in this solution, followed by filtration and defoaming to prepare a cellulose acetate solution. The above cellulose acetate solution was placed on an 8h long endless stainless steel band attached to a hanger drum.
After thinning and peeling from the stainless steel strip using several casting ports, drying is completed while conveying with many rolls to a film thickness of 140.
A cellulose acetate film was produced. At this time, the amounts of cellulose acetate solution cast from the first and second casting ports were adjusted to contribute 45% and 55%, respectively, to the finished film thickness of 140A. Furthermore, the distances between the first casting point and the peeling point are 5 machines, and the second casting point is 0.8 m, 2 m, 2.5 m, 2.8 m, and 4 m apart from the first casting point, respectively. It was located somewhere. The results are shown below. All of the films after drying had little curl and had good flatness and were satisfactory as bases for photographic supports. In this example, almost the same results were obtained even when isoptanol was used instead of n-butanol.

[Brief explanation of the drawing]

The drawing is a cross-sectional view of the apparatus used in the method according to the present invention. 1... First casting port, 3... Support body,
4...Second casting port, 7...Peeling position.

Claims (1)

[Claims] 1. Cast an amount of cellulose acetate solution on the support surface from the first casting port to a thickness equivalent to 10 to 90% of the final finished film thickness, dry it, and before peeling it off from the support surface, A cellulose acetate solution for second casting in an amount corresponding to the remaining thickness is poured at a position separated from the first casting port by a distance of 30 to 60% of the distance between the first casting port and the peeling position. The amount of residual solvent with respect to cellulose acetate in the cast layer that was cast from the first casting port, dried, and fused was 80%.
A method for producing a cellulose acetate film, characterized in that it is peeled off from the surface of the support at % by weight or more, and further dried from both sides. 2. When the cellulose acetate solution for second casting has the ability to dissolve the layer cast from the first casting port, the final finished film thickness is The method for producing a cellulose acetate film according to claim 1, wherein an amount corresponding to 40 to 80% of the thickness of the cellulose acetate film is cast. 3 Cellulose acetate solution contains 87 to 95% by weight of methylene chloride and 5 to 1% of methanol or ethanol.
The method for producing a cellulose acetate film according to claim 2, having a solvent composition of 3% by weight. 4 When the cellulose acetate solution for second casting has the ability to dissolve the layer cast from the first casting port, the final finished film thickness is 2
The method for producing a cellulose acetate film according to claim 1, wherein the cellulose acetate film is cast in an amount corresponding to a thickness of 0 to 60%. 5 The cellulose acetate solution contains 70 to 87% by weight of methylene chloride and 13 to 87% by weight of methanol or ethanol.
The method for producing a cellulose acetate film according to claim 4, having a solvent composition of 30% by weight. 6 Cellulose acetate solution contains 70 to 90% by weight of methylene chloride and 5 to 1% of methanol or ethanol.
5. The method for producing a cellulose acetate film according to claim 4, having a solvent composition of 5% by weight and 5 to 15% by weight of synchlohexane. 7 Cellulose acetate solution contains 80-90% by weight of methylene chloride, 2-7% methanol or ethanol
5. The method for producing a cellulose acetate film according to claim 4, having a solvent composition of 5 to 13% by weight of n-butanol. 8 The cellulose acetate solution contains 80-93% by weight of methylene chloride and 2-7% of methanol or ethanol.
5. The method for producing a cellulose acetate film according to claim 4, having a solvent composition of 5% to 13% by weight of iso-butanol.