JPS61110520A - Manufacture of film - Google Patents

Abstract

PURPOSE:To manufacture foamless film at high speed, by a method wherein a temperature rise of a part of a supporting material surface made of either a band or a drum whereon dope is not casted yet is prevented, in a solvent film manufacturing method. CONSTITUTION:Air shield plates 10a, 10b whose cross sections are in U-shaped state are kept provided so as to cover only a band part 2a wherein dope 3 is casted. The dope 3 made of cellulose acetate is casted on a support surface made of an endless band 2, hot air is fed to the air shield plates 10a, 10b and a film is manufactured by volatilizing a solvent. Although a side edge part of the dope becomes a high temperature than the central part and is apt to generate foaming, as a temperature rise of the side edge part is prevented by the air shield plate, a matter like this does not happen, dryness can be performed at a higher temperature than usual and a film manufacturing rate can be improved.

Description

[Detailed Description of the Invention] (Industrial Application Field) Generally, cellulose acetate, polycar H? Nate,
Films such as cellophane are manufactured using a solution casting method. The present invention improves this solution casting method.

(Prior Art) Film formation by the solution casting method is carried out using a casting apparatus as shown schematically in FIG. 4 or 5. In this method, a dope 3 in which a film-forming material is dissolved in a suitable solvent is cast from a casting port 1 onto a support made of a band 2 or a drum 8, most of the solvent is evaporated, and then a stripping section is formed. In this method, a film is produced by peeling off the film in step 6 and then evaporating the remaining solvent in a suitable drying device.

As shown in FIG. 6, which is a sectional view of the vicinity of the casting part of both apparatuses, the dope 3 was conventionally cast onto the center portions of the supports 2 and 8 when either of these apparatuses was used. The side edge portions were handled in the same way as the portions where the dope 3 was cast without being cast.

(Problems to be Solved by the Invention) The biggest problem with this solution film forming method is that the film forming speed is slow. If the cast film-forming material is peeled off after insufficient drying, a number of inconveniences may occur, such as a portion of the film-forming material remaining attached to the support surface19. Therefore, it is necessary to dry the material before removing it with a sieve to at least prevent such a situation from occurring, but since the drying speed of film-forming materials is generally slow, shortening the drying speed is the key to keeping the film-forming speed up. It had become.

In order to increase the drying speed, hot air is introduced to the surface of the support,
Heating was performed from the back side of the drum and band, but if this heat supply became excessive, the solvent would evaporate inside and foam would form within the film, so the heat supply was limited to prevent foaming. .

(Means for Solving the Problems) The present invention provides a means for maximizing the supply of heat.

The inventors of the present invention conducted a detailed study to elucidate the mechanism of this foaming, and found that, regardless of whether band casting equipment or drum casting equipment is used, when the heating temperature is increased, the foaming occurs first. It has been found that foaming begins near the side edges of the dope, and as the temperature is further increased, foaming spreads over the entire area of the dope.

As a result of further investigation into the cause, the following was discovered. That is, the portion of the support surface where the dope is cast is deprived of the latent heat of vaporization of the solvent, but the portion where the dope is not cast is not subject to such a load and therefore becomes higher in temperature. The side edges of the cast dope are affected by the high temperature of the non-cast portions and are more likely to foam than the center.

As the temperature is further increased, foaming begins to occur from the entire area of the dope, but this foaming does not expand continuously over the entire area as the heating temperature increases, but rather from foaming at the side edges. It was found that there was a difference in hot air temperature of about 10 to 30°C for foaming over the entire area.

The present invention was made based on such knowledge,
By preventing the temperature rise of the surface of the support on which Dogue is not cast, the heating temperature can be further increased and the drying time can be shortened.

That is, the present invention provides a method for producing a film by casting a dope onto a support, heating it to evaporate the solvent, and then peeling it off from the support, in which the dope is removed from the surface of the support. The present invention relates to a method for producing a film, characterized in that a temperature rise due to the heating in the non-cast portion is prevented.

The dope may be a normal one, such as cellulose acetate, polycarbonate, or cellulose xanthate) (IJ)
Each film-forming material such as aluminum is dissolved in a known solvent. For example, in the case of cellulose triacetate, use a mixed solvent of methylene chloride and methanol or ethanol.

TP is dissolved in a mixed solvent to which a poor solvent such as n-butanol, penzole, toluene, or cyclohexane is added.
It is prepared by further adding a plasticizer such as P.

The support may be either a band or a drum. The heating means for drying the dope cast on the support is not limited; in the case of a band casting device, heating the band surface, back surface, or both surfaces thereof with a heater or an infrared heater, or heating with hot air. , passing hot water through the drum, etc. may be used, and heating can be achieved by any one of these means or a suitable combination of these methods. In the case of drum casting equipment, the drum surface.

Heating by a heater or infrared heater on the back side or both sides thereof, heating with hot air, passing hot water through the drum, etc. may be used, and heating can be performed by any one of these means or an appropriate combination of these. .

The method of the present invention is a film forming method using such a band casting device or a drum casting device, and the dope is heated to dry the dope on the support surface where it is not cast. The feature is that it prevents the temperature from rising.

This prevention of temperature rise may be carried out by a method of blocking heat so that heating does not reach the part 1, or by a method of removing heat that has reached the part 1. Furthermore, both can be used together.

As a method of cutting off heat, if the heating means is hot air, for example, Fig. 1 shows an outline of the side surface, and Fig. 2 shows its A-A.
As shown in the partial sectional view, there is a method of blocking the wind with a wind shielding plate. The device in this example is a band casting device, with drums 4a and 4b.
The dope 3 is cast from the casting port 1 onto the endless band 2 which is suspended between the belts and runs by the driving rotation of the drum 4a.
A film obtained by blowing hot air 5a onto the cast dope 3 and drying it is peeled off from the band 2 by a peeling section 6. The hot air 5a travels on the band 2 in the traveling direction and leaves at the lower part of the drum 4b on the right side of FIG. On the other hand, hot air 5
b is sprayed onto the surface of the band 2 from the lower side of the drum 4a.

This hot air 5b advances against the advance of the band 2 and leaves at the bottom of the drum 4b. Wind shielding plate 10a.

10b, these hot air 5a, 5b are the dope 3 on the band 2 side.
It is provided so that it passes only through the part 2a that is being cast and does not come into contact with the part 2b that is not being cast. In the illustrated example, a wind shield plate having a U-shaped cross section is used (see FIG. 2).

The wind shielding plate is not limited to this example, and for example, in the example shown in FIG. 2, it may have only the side plates 101 and 102 and no top plate 103. This both side plate 101
．． The installation position of the dope 102 is not limited to right above the both ends 31 and 32 of the dope 3 being cast, but the point is that the entire surface of the dope 3 being cast is heated so that the dope 3 is flown. It is sufficient to place the unstretched band portion 2b at the most appropriate position where it is not heated. It goes without saying that the installation angles of the side plates 101 and 102 are not limited to the direction perpendicular to the band 20 surface. This wind shielding plate 10a.

10b can also be replaced with a curtain, air curtain, or the like.

These wind blocking means such as a wind blocking plate, curtain, or air curtain are usually provided throughout the flow path through which hot air flows on the band surface.

However, as the drying progresses, foaming becomes less likely to occur, so it is possible to omit the latter half, and as shown in Figure 1, it can also be omitted near the exhaust area where most of the heat of the hot air is consumed. can do.

The example in Fig. 1 is an example in which hot air 5a+5b is blown to the front side of the band 20 in a band casting device, but when the hot air is blown to the back side of the band 2, and in the case where it is blown to the front or back side of the drum in a drum casting device. You can also use each of the above methods as is.

On the other hand, as a method for removing the heat applied to the part of the support where the dope is not cast, for example, as shown in FIG. There is a method of providing the cooler 11 at the lower part of the band 2b which is not installed. In this example, a heater 7 for heating the upper part is disposed below the band 2a on which the dope 3 is cast.

The means for removing the heat is not particularly limited; for example, a refrigerant such as cold water or cold air may be used. In the case of cold air, it is also possible to blow it directly onto the band surface, in which case any of the above-mentioned wind blocking means can be used. Cooling should be limited to an appropriate temperature.

Too much cooling will have an adverse effect, such as reducing the drying rate of the side line portion of the cast dope. This cooling can be performed on both the front and back sides of the band, and can also be performed on either side of the drum. Regarding the cooling part, it is the same as the above example that it is particularly effective for the first half of drying.

Above, we have described the case of heating with hot air, but the heater,
Even in the case of heating by means such as an infrared heater, heating by passing hot water through the drum, etc., the temperature rise in the area where the dope is not cast can be prevented by the same means.

(Function) In the method of the present invention, by preventing the temperature rise of the part of the support surface where the dope is not cast, the influence of temperature on the side edge of the cast dope in that part is removed, and the side edge This prevents foaming in the first stage, which concentrates in the area.

(Example) A cellulose triacetate film having a dry thickness of 125 μm was produced by casting Dogue having the composition shown below using the apparatus shown in FIG.

Cellulose triacetate 17.4 parts Triphenyl phosphate 26 parts Methylene chloride 66 parts Methanol
58 parts Butanol 82 parts The upper limit temperature at which the hot air 5a does not foam when the wind shields 10a and 10b are not provided is 80°C, and when the temperature of the hot air 5b is fixed at 100°C, the stripping time is 2.1 It's been a minute. On the other hand, the wind shielding plate 10a.

When 10b is installed, the upper limit temperature of hot air 5a is 100℃
When the temperature of the hot air 5b was fixed at 100° C., the stripping time was shortened to 1.7 minutes.

(Effects of the Invention) In the method of the present invention, localized foaming in the first stage that starts as the heating temperature rises is eliminated, and heating can be carried out to an extreme temperature close to the temperature at which foaming starts on the entire surface. There is. As a result, the drying rate of the cast dope can be increased to the maximum, and the film forming rate can be increased.

[Brief explanation of drawings]

FIG. 1 is a side view showing an outline of an example of a casting apparatus used in the method of the present invention, and FIG. 2 is a sectional view taken along line A--A. FIG. 3 shows another example, and is a partial sectional view around the casting boundary. FIG. 4 is a side view showing an overview of a general band casting apparatus, and FIG. 5 is a side view showing an overview of a general drum casting apparatus. FIG. 6 is a partial sectional view of the support portion. ■...Casting port, 2... Band, 2a... Part where dope is cast, 2b... Part where dope is not cast, 3 - Dope, 31.32... side End, 4
a +4b ・Drum, 5a, 5b...Hot air, 6・
... Stripping part, 7... Heater, 8... Drum, 10a
, 10b... Wind shielding plate, 101.102... Side plate, 1
03...Top plate, 11...Cooler. Patent Applicant Fuji Photo Film Co., Ltd. Agent Patent Attorney 1) Hiroshi Naka Masa b Guidance Figure 2 Procedural Amendment (Voluntary) December 21, 1980 Commissioner of the Patent Office Manabu Shiga Manabu Shiga Patent Application for Indication of Case 1 No. 59-232390 2. Name of the invention 3. Process for producing film 3. Relationship with the person making the amendment Name of patent applicant (520) Fuji Photo Film Co., Ltd. 4. Agent address 21-3 Hatchobori 3-chome, Chuo-ku, Tokyo 104
No. 607 Claims (1) A method for producing a film by casting a dope onto a support, heating it to evaporate the solvent, and then peeling it off from the support, wherein A method for producing a film characterized in that a temperature rise due to the heating is prevented in a portion where the dope is not cast (2) The heating is performed by hot air, and the temperature rise prevention means is a casting process. (3) The method for producing a film according to claim 1, wherein the temperature rise prevention means is carried out by a wind shield that blocks the hot air at the side edge of the dope that is being cast. The method for manufacturing a film according to claim 1, which comprises cooling the unused portions with a refrigerant.

Claims (3)

[Claims] (1) In a method of manufacturing a film by casting a dope onto a support, heating it to evaporate the solvent, and then peeling it off from the support, the dope is not cast on the surface of the support. A film manufacturing method characterized by preventing a temperature rise due to the heating in the non-existent portions. (2) Claims in which the heating is performed by hot air, and the heating is performed by a wind shield that blocks the hot air at the side edge of the dove on which the temperature rise prevention means is cast. Method for producing the film described in item 1 (3) The method for producing a film according to claim 1, wherein the temperature rise prevention means is cooling the portion where the dope is not cast with a refrigerant.