JPH0736148A - Production of photographic base - Google Patents

Abstract

PURPOSE:To prevent blocking with a cooling roll and staining by cooling without impairing the adhesion of a molten polyolefin resin and a paper base even if a coating speed is increased by blowing cold air to the surface on the cooling roll side of the film of this resin and blowing an ozone-contg. gas to the surface on the paper base side. CONSTITUTION:The surface for contact with the resin of the paper base 1 is previously subjected to an activation treatment by a corona treatment. The cold air kept at 15 to 30 deg.C is blown from a bar 5 of a slit type to the surface on the cooling roll 7 side of the molten polyolefin resin film 2 extruded from a T die 4 of an extruder, by which the film is cooled. Further, an ozone-contg. gas kept at 20 to 70 deg.C is blown from a bar 3 of a slit type to the side in contact with the paper base 1 of the molten polyolefin resin film 2 extruded from the T die 4 of the extruder. Such cooling is combined, by which the degradation in the adhesive power is obviated and the staining is prevented even if the resin temp. in the outlet of the T die 4 of the extruder is kept at 250 to 300 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prevents the blocking of cooling rolls and stains of cooling rolls, and prevents the stains of the cooling rolls in the production of a photographic support comprising one or both sides of paper coated with a polyolefin resin. The present invention relates to a method for producing a photographic support that does not cause a decrease in adhesive strength. Further, the present invention relates to a manufacturing method which does not cause these problems even if the coating speed is increased.

[0002]

2. Description of the Related Art Today's photographic supports are generally made water-resistant by coating a polyolefin resin on one or both sides of the paper in order to accelerate the development of photographic paper. A method for coating paper with a polyolefin resin such as polyethylene or polypropylene is to extrude the melted polyolefin resin from a T-die of an extruder into a running paper, and let it flow down onto the paper. The coating method is used.

Due to the performance of the photographic support, a polyolefin resin is blended with a pigment, a dispersant and the like, which causes blocking problems due to poor peeling between the resin and the cooling roll during extrusion coating and product contamination due to stains on the cooling roll. Especially as a photographic support, it becomes a serious problem in terms of quality. Further, it is important to increase the coating speed in order to increase the productivity and reduce the cost, but increasing the coating speed remarkably increases the product contamination due to blocking and stains on the cooling roll, and increases the polyolefin resin and the paper substrate. The problem of reduced adhesive strength also occurs.

The problem of blocking with a cooling roll is that striped or linear unevenness of gloss is generated on the surface of the product or a small convex blister called a blister, which is unusable from the viewpoint of image formation for photography. Further, the coated paper is cut at the portion where it is peeled from the cooling roll where blocking is strongly generated, and it becomes impossible to process. The photographic support is a problem particularly in the case of a mirror-like support such as a mirror-like support, a rough surface (mat) support, a silk-like support, a fine-grain support, etc., depending on the surface-molded state.

Further, the problem of product contamination due to stains on the cooling roll is that low molecular weight substances in polyolefin resin, stabilizers and dispersants, etc., adhere to the cooling roll and are transferred to the product, causing glare and uneven gloss on the product. However, it is necessary to stop the extrusion process and clean the cooling roll, which significantly impairs processability. As in the case of general wrapping paper and laminated paper such as printing paper, blocking and cooling roll stain increase as the coating speed increases.

The same applies to the reduction of the adhesive force between the resin and the paper substrate, but the paper substrate as a photographic support increases the water content in the base paper as a countermeasure against discharge fog caused by static electricity, and it also contains a conductive agent. Addition, strong size, and high smoothness are required, and the fact that the resin is mixed with pigments and dispersants is also a factor that reduces the adhesive strength between the resin and the paper substrate, which is remarkable when the coating speed is increased. descend.

A printing paper having a low adhesive strength has a poor appearance, and in particular, in the development processing step, the processing liquid invades from the cut end portion to cause discoloration and the image is distorted. If the adhesion is insufficient when cutting the photographic paper into a predetermined size, a whisker-shaped polyolefin stretched product is generated at the cut end, resulting in poor cutting and poor appearance.

[0008] It has been publicly known that the blocking and cooling stains are improved by lowering the resin temperature, but if the resin temperature is lowered, the adhesion deteriorates. There is a limit to reducing the temperature of the cooling roll, but there is a limit. For example, if the temperature is lowered too much, moisture in the air will condense and another problem will occur. There is also a method of adding a release agent, but none is sufficiently suitable for a photographic support. There is a method of making a temperature difference between both sides of the film by using the T-die of the extruder. However, the fluidity of the molten resin in the T-die of the extruder is disturbed and it is difficult to obtain a stable film. No effect. Regarding adhesion, corona treatment of the base paper surface, flame treatment, heating treatment, ozone treatment of molten film, etc. are known, but the resin temperature is lowered to a level where blocking or cooling roll contamination does not occur even if any method is used. And it was difficult to obtain the desired adhesion.

[0009]

The problem to be solved by the present invention is to study various measures to solve these problems, and to block or cool the cooling roll without damaging the adhesion between the resin and the paper base even if the coating speed is increased. Finding a way to get rid of dirt.

[0010]

[Means for Solving the Problems] That is, the surface of the paper base that comes into contact with the resin is activated in advance, and the surface of the molten polyolefin resin film extruded from the T die of the extruder is cooled by blowing cold air onto the surface of the film. Cooling the film surface,
Production of a photographic support characterized in that an ozone-containing gas is blown to a surface of a molten polyolefin resin film to be adhered to a paper substrate to enhance the adhesiveness of the molten polyolefin resin film, and then the paper substrate is coated with the molten polyolefin resin. Is the way.

More specifically, the surface of the paper base that comes into contact with the resin is activated by corona treatment in advance, and the surface of the molten polyolefin resin film extruded from the T die of the extruder on the cooling roll side has a temperature of 15 ° C to 30 ° C. Means for cooling the surface of the molten film by blowing cold air from a slit type bar or a bar having a predetermined hole formed in a cylinder, and a portion of the side of the molten polyolefin resin film extruded from the T-die of the extruder which is in contact with the paper substrate. The temperature on the surface of the molten film is 20 ° C to 70 ° C.
The ozone-containing gas at a temperature of 2 ° C is combined with a slit-type bar or a means in which a cylindrical bar is provided with predetermined holes to increase the resin temperature at the T-die outlet of the extruder to 2 ° C.
For photographic use, even at 50 ° C to 300 ° C, it is possible to prevent blocking with the cooling roll and stains on the cooling roll without lowering the adhesive strength, and even if the coating speed is increased, these problems do not occur. A method for manufacturing a support has been found.

The temperature of the cold air blown by the cold air is 15 to 30 ° C.
Is effective, and less than 30 ° C.
Cold air below ℃ will increase the cost. The speed of cold air is 6m /
sec to 14 m / sec is preferable, but if the surface of the molten film can be cooled, any speed may be used as long as the force of the wind does not cause wrinkles on the film surface or the surface becomes non-uniform after resin coating. The effective temperature of the ozone-containing gas blown to the side of the molten film that contacts the paper substrate is 20 ° C to 70 ° C. If the temperature is lower than 20 ° C, the temperature of the resin surface is lowered, and if the temperature is higher than 70 ° C, ozone is decomposed and the effect is small. The amount of ozone sprayed is 1 mg per 1 m ² of molten resin
300 mg is effective, and it is effective to use it while confirming the adhesiveness by the resin temperature and the coating speed. If the amount of ozone is less than 1 mg, the effect is small, and if it exceeds 300 mg, the effect of adhesion is flat and uneconomical.

The resin temperature at the exit of the extruder T die is 280 ° C. to 320 ° C. when only blowing cold air is effective.
If it is less than 100%, the adhesive strength tends to be lowered, and the resin temperature cannot be greatly lowered, but the resin temperature when the ozone-containing gas blowing method is used in combination is particularly 250 ° C. to 30 ° C.
0 ° C is effective. That is, when both the cold air blowing means and the ozone-containing gas blowing means are used together, the adhesive strength can be expected to be improved, and the resin temperature can be greatly lowered in order to prevent blocking and cooling stains remarkably. Further, even if the resin coating speed is increased by that much, the same quality as the photographic support obtained at a normal coating speed can be maintained. Further, by lowering the resin temperature to, for example, 300 ° C. or lower, it becomes possible to reduce decomposition and deterioration of the resin.

[0014]

[Examples] Examples will be described below. The present invention is not limited to the embodiments.

Examples 1 to 8 and Comparative Examples 1 to 4 75% by weight of low density polyethylene having a density of 0.918 g / cm ³ and 0.962 g / density on a paper used as a photographic support having a basis weight of 170 g / m ^2. uniformly dispersed extrusion coating a polyethylene resin composition was 10% by weight of anatase type titanium dioxide and 0.5 wt% of zinc stearate respect cm ³ of high density polyethylene 25% by weight of the mixed resin in the mixed resin . On the other side, the density is 0.918 g /
cm ³ low density polyethylene 50% by weight and density 0.962
A photographic support is prepared by extrusion coating a polyethylene composition comprising 50% by weight of high density polyethylene, g / cm ³ . At this time, the traveling speed of the paper substrate is 15
0 m / min and 180 m / min, the resin temperature at the extruder outlet was set to 240 ° C to 340 ° C respectively, and the corona treatment was performed for the activation treatment of the paper substrate, and the molten resin film was sprayed on the cooling roll side. The cold air is used by cooling compressed air from a compressor, and the ozone-containing gas blown to the paper substrate side is an ozone generator manufactured by Nippon Ozone Co., Ltd. The treatment amount was 1 mg to 300 mg per 1 m ^{2 of the} polyolefin resin. The cold air and the ozone-containing gas were blown by using a cylindrical bar having holes each having a diameter of 1.5 mm at 5 mm intervals. The results are shown in Table 1.

[0016]

[Table 1]

The effects shown in Table 1 are evaluated as follows. The blocking property is 1 to 10 by observing the fluctuation when leaving from the cooling roll and the surface condition of the photographic support.
The results were divided into classes and graded. The cooling stain resistance is 1 to 1 by observing the stain condition of the cooling roll and the cloudiness of the surface of the photographic support.
Scored by classifying as 0. Adhesiveness was measured after storing the photographic support at 50 ° C for 12 hours,
The resin was peeled from the surface of the raw paper, the area of fuzz on the surface of the raw paper was measured, and the classification was performed by classifying into 1 to 10. As a photographic support, a product having a rating of 4 or less in any of the above three evaluations is unacceptable as a product.

[0018]

[Effects of the Invention] 1 on the surface of the molten polyolefin resin film extruded from the T die of the extruder on the cooling roll side.
By blowing a cool air of 5 ° C to 30 ° C and blowing an ozone-containing gas onto the surface of the molten polyolefin resin film that is to be bonded to the paper substrate, blocking and cooling roll stains can be prevented even if the resin coating speed is increased. Since the paper base and the resin layer have good adhesion without gloss unevenness and glare, a photographic support can be obtained without impregnation of the developing solution at the time of development and cutting defects due to the generation of polyolefin stretched products at the time of cutting. As described above, according to the present invention, blocking and stains on the cooling roll can be remarkably improved, and productivity can be improved.

[Brief description of drawings]

FIG. 1 blows cold air from a cooling roll side to a molten polyolefin film extruded from a T-die of an extruder and ozone-containing gas from a paper base side, and a paper base is made of the molten polyolefin film by a cooling roll and a pressure roll. FIG. 3 is a schematic view of a method for producing a photographic support to be coated. 1. Paper substrate 2. Molten polyolefin film 3. Ozone-containing gas spraying bar 4. T-die 5. Cold air spraying bar 6. Pressure roll 7. Cooling roll 8. Take-up roll

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Claims (4)

[Claims] 1. After activating one surface of a paper substrate, a polyolefin resin is applied to the surface of the running paper substrate by means of an extruder T.
In the method for producing a photographic support which is extrusion-coated with a die, the surface of the film of the molten polyolefin resin extruded from the T-die of the extruder on the cooling roll side is 15 ° C to 3 ° C.
A method for producing a photographic support, characterized in that cold air of 0 ° C. is blown and an ozone-containing gas is blown to the surface of the paper substrate side. 2. The temperature of the molten resin at the T die outlet of the extruder is 2
The method for producing a photographic support according to claim 1, wherein the temperature is from 50 ° C to 300 ° C. 3. The photographic support according to claim 1, wherein the temperature of the ozone-containing gas blown onto the molten resin film is 20 ° C. to 70 ° C., and the amount of ozone blown is 1 mg to 300 mg per 1 m ^{2 of the} molten film. Production method. 4. The method for producing a photographic support according to claim 1, wherein the activation treatment on the paper substrate is a corona discharge treatment.