JPS60111241A - Manufacture of photographic support - Google Patents

Abstract

PURPOSE:To prevent blocking with a cooling roll and staining due to cooling by blowing cold air on the face of a molten polyolefin film extruded from the T-die of an extruder to cool its surface of the film from the side of a cooling roll, and then, coating a paper base with said molten polyolefin resin. CONSTITUTION:The molten resin temp. at the outlet of the T-die 4 of an extruder is controlled to 280-320 deg.C, the face of the resin to be brought into contact with a paper base 1 is activated by the corona treatment in advance, and cold air of 15-30 deg.C temp. is blown from a slip-shaped bar 5 against the face of the molten polyolefin resin 2 on the side facing a cooling roll 7 to cool the film 2. This molten film 2 is allowed to flow on the paper base 2 and both are joined with the cooling roll 7 and a press roll 6. As a result, blocking with the cooling roll 7 and staining of this rool 7 are prevented without lowering adhession of the film 2 with the paper base 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is intended to prevent blocking with cooling rules and staining of cooling rolls in the production of photographic supports in which one or both sides of paper are coated with polyolefin resin, and to prevent the cooling rolls from being blocked and to avoid staining the cooling rolls. The present invention relates to a method for producing a photographic support that does not cause a decrease in the adhesive strength of a polyolefin resin.

Furthermore, it relates to a manufacturing method that does not cause these problems even when the coating speed is increased.

The current photographic support is Mill!, a photographic paper. In order to speed up processing, it is common to coat one or both sides of paper with a polyolefin resin to make it waterproof. A method for coating paper with polyolefin resin such as polyethylene or polypropylene is extrusion, in which molten polyolefin resin is extruded into a film from an extrusion-like T-die, allowed to flow onto the traveling paper, and then bonded together using cooling rolls and press rolls. A coating method is used.

For photographic supports, pigments, dispersants, etc. are blended with polyolefin resin for performance reasons, and problems such as blocking due to poor peeling between the resin and cooling roll during extrusion coating and product contamination due to cooling roll stains occur. Especially as a photographic support, this poses a serious quality problem. Furthermore, although it is important to increase the coating speed to increase productivity and reduce costs, increasing the coating speed significantly increases product contamination due to sieve blocking and cooling roll stains, and also increases the risk of contamination between polyolefin resins and paper substrates. The problem of decreased adhesive strength also occurs.

The problem of blocking with the cooling roll causes striped or linear uneven gloss on the surface of the product, or small convex swelling called blisters, which makes the product unusable in terms of image formation for photography. Furthermore, if blocking occurs strongly, the coated paper will be cut at the part where it peels off from the cooling roll, making it impossible to process it.

Photographic supports include mirror supports, rough supports, matte supports, fine-grain supports, etc., depending on the state of surface patterning, but mirror supports pose a particular problem.

In addition, the problem of product contamination due to cooling roll dirt is that low molecular weight substances, stabilizers, dispersants, etc. in the polyolefin resin adhere to the cooling roll, and this is transferred to the product, causing surface glare and uneven gloss, making it impossible to commercialize the product. However, the extrusion process must be stopped and the cooling roll must be cleaned, which significantly impedes processability. As with laminated papers such as general wrapping paper and printing paper, blocking and cooling roll stains increase as the coating speed increases. The same goes for the decrease in adhesive strength between resins and paper substrates, but the paper substrate used as a photographic support is made by increasing the water content in the base paper to prevent discharge fog due to static electricity, adding conductive agents, etc., and increasing the size of the paper substrate. , the need for high smoothness, and the fact that the resin contains pigments, dispersants, etc. are factors that reduce the adhesive strength between the resin and the paper substrate, which decreases significantly when the coating speed is increased. . Photographic paper with low adhesion deteriorates its appearance. Particularly in the developing process, processing liquid may seep into the cut edges of the paper, causing discoloration and distortion of the image. Furthermore, if the adhesion is insufficient when cutting the photographic paper into a predetermined size, whisker-like stretched polyolefin products will occur at the cut end, resulting in poor cutting and poor appearance.

It has been known that blocking and cooling stains can be improved by lowering the resin temperature; however, lowering the resin temperature deteriorates adhesion. Lowering the temperature of the cooling roll is also an improvement, but there are limits. For example, if the temperature is lowered too much, moisture in the air will condense, causing other problems. There is also a method of adding a release agent, but none is sufficiently suitable for use as a photographic support.

There is a method of creating a temperature difference on both sides of the film using the T-die of the extruder, but the fluidity of the molten resin inside the extruder T-die is disturbed, making it difficult to obtain a stable film, and there is a limit to the temperature difference. Not enough effect. Regarding adhesion, methods such as corona treatment, flame treatment, heating treatment of the base paper surface, and ozone treatment of the molten film are known, but none of these methods lowers the resin temperature to a level that does not cause blocking or cooling roll stains. It was difficult to achieve the desired adhesion. As a result of various studies on these countermeasures, we have found a method that solves the problem of blocking with the cooling roll and cooling stains without impairing the adhesion between the resin and the paper substrate even when the coating speed is increased, resulting in the present invention. That is, the surface of the paper base in contact with the resin was activated in advance, and the surface of the molten polyolefin resin film extruded through the T die of the extruder was blown onto the cooling roll side to cool the surface of the molten film.
This is a method for producing a photographic support, which comprises coating a paper substrate with the molten polyolefin resin.

Furthermore, cold air is blown onto the surface of the molten polyolefin resin film extruded through the T-die of the extruder on the cooling roll side to cool the molten film surface, and ozone-containing gas is blown onto the molten film surface on the side that is in contact with the paper substrate. The method for producing a photographic support is characterized in that the paper substrate is then coated with the molten polyolefin resin.

More specifically, the temperature of the molten resin at the T-die outlet of the extruder is set to 2.
The surface of the paper base in contact with the resin was activated by corona treatment at 80 to 320°C, and the surface on the cooling roll side of the molten polyolefin resin film extruded from the T-die of the extruder was heated to 15 to 30°C. The surface of the molten film is cooled by blowing cold air through a slit-shaped hole or a bar with predetermined holes in a cylinder. The speed of the cold air at this time is 6
m/see to 14 m/see is preferred. This molten film, whose surface has been cooled, is allowed to flow down onto the paper substrate and bonded together using a cooling roll and a press roll. This prevents blocking of the cooling roll and dirt on the cooling roll without reducing the adhesion between the resin and the paper substrate. found that it can be prevented. Furthermore, ozone-containing gas at a temperature of 20°C to 70°C is applied to the molten film surface of the molten polyolefin resin film extruded from the T-die of the extruder on the side that contacts the paper substrate, preferably in an amount of 1ff of the molten polyolefin resin film/300F of the molten polyolefin resin film. By combining the method of spraying from a slit-shaped bar or a cylindrical bar with predetermined holes, the adhesive strength will not decrease even if the resin temperature at the exit of the T-die of the extruder is increased to 250°C to 300°C. We have discovered a method for producing a photographic support that can prevent blocking with the cooling roll and the cooling roll without causing any of these problems, and that does not cause these problems even when the coating speed is increased.

A temperature of 15°C to 30°C is effective for blowing cold air, a temperature of 30°C or higher is less effective, and a temperature of 15°C or lower increases the cost of expanding the cold air. The speed of cold air is 6 m/sec ~ 1
4 m/- is preferred, but any speed is acceptable as long as it cools the molten film surface.

An effective temperature of the ozone-containing gas blown onto the side of the molten film in contact with the paper substrate is 20°C to 70°C. 20℃
If it is less than 70°C, the temperature of the resin surface will be lowered, and if it is higher than 70°C, ozone will decompose and the effect will be low. It is effective to spray ozone in an amount of 1 to 300 wg per molten resin, and it is efficient to use it while checking the adhesion depending on the resin temperature and coating speed. If the amount of ozone is less than 1 m9, the effect will be small, and if it is more than 300 m, the adhesion effect will remain flat and it will be uneconomical.

Regarding the resin temperature at the T-die exit of the extruder, a temperature of 280°C to 320°C is particularly effective when only cold air is blown. Linear adhesion tends to decrease below 280°C, and the coating speed decreases at temperatures higher than 320°C. As the amount increases, the effect on blocking and cooling dirt tends to decrease. Furthermore, when using the ozone-containing gas blowing method in combination, a resin temperature of 250°C to 300°C is particularly effective. When used in conjunction with the ozone-containing gas blowing method, it is expected that the adhesion strength will improve.
As a result, by lowering the resin temperature to, for example, 300° C. or lower, it becomes possible to reduce decomposition and deterioration of the resin.

Examples will be described below. Note that the present invention is not limited to the examples.

Examples 1 to 12 and Comparative Examples 1 to 3 Paper used as a photographic support with a basis weight of 1702/- has a density of 0.
A mixed resin of 75% by weight of low-density polyethylene of 918 f/crd and 25% by weight of high-density polyethylene of density 0.962 f/di, 10% by weight of anatase-reduced titanium dioxide and 0.5% by weight of the mixed resin. A polyethylene resin composition in which 1 it% of zinc stearate is uniformly dispersed is extrusion coated. Also, the other side has a density of 0.91
50% by weight of 8fA low density polyethylene and density 0.96
A photographic support is prepared by extrusion coating a polyethylene composition comprising 50% by weight of 2 f/m high density polyethylene. At this time, the running speed of the paper base was set to 15
0 m/min.

and 180 m/min, and the resin temperature at the extruder outlet was 260 m/min.
The conditions are set from ℃ to 340℃, and the paper substrate is activated by corona treatment, and the cold air that is blown onto the cooling roll side of the molten resin film is cooled using compressed air from a compressor and blown onto the paper substrate side. For the ozone-containing gas, an ozone generator manufactured by Nippon Ozone ■ was used, and the amount of ozone generated was 40 ozone using air as the raw material, and the ozone concentration was adjusted to the processing speed for polyolefin resin 1rI? Hit 1■～300
It was carried out with a throughput of 11v. The cold air and the ozone-containing gas were blown using a cylindrical bar with holes of 1.5× diameter drilled at 5 m intervals. The results are shown in Table-1.

The evaluation of the effect in Table 1 is as follows. Blocking property was evaluated as 1 to 1 by observing the fluctuation when it was separated from the cooling roll and the surface condition of the photographic support.
The students were divided into 0 classes and scored.

■ Cooling stain resistance is determined by observing the dirt on the cooling roll and the appearance of spiders on the surface of the photographic support.
The students were divided into 0 classes and scored.

(2) Adhesion was evaluated by storing the photographic support at 50° C. for 12 hours, peeling off the resin from the base paper surface, measuring the area of fluff on the base paper surface, and grading the results into classes from 1 to 10.

As a photographic support, a support with a score of 4 or less in any one of the above three evaluations is rejected as a product.

Table 1 As described above, according to the present invention, blocking and cooling roll stains are significantly improved, and productivity can be improved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing one embodiment of the invention. 1. Paper base 2 Melt polyolefin film &　Ozone-containing gas spraying device 4. T-die 5.-Cold air blowing device 6. Pressure roll 7. Cooling roll a Collection roll Figure 1

Claims (1)

[Scope of Claims] 1. A method for producing a photographic support, which comprises activating one side of a paper base, and then extruding and coating the surface of the running paper base with a polyolefin resin through a T die of an extruder, A method for producing a photographic support, which comprises blowing cold air at 15°C to 30°C onto the cooling roll side of a molten polyolefin resin film extruded through a T-die of an extruder. 2. The method for producing a photographic support according to claim 1, which comprises blowing an ozone-containing gas onto the paper substrate side surface of the molten polyolefin resin film extruded from a T-die of an extruder. & The temperature of the molten resin at the T-die exit of the extruder is 280℃~3
The method for producing a photographic support according to claim 1, wherein the temperature is 20°C. The temperature of the molten resin at the T-die exit of the extruder is 250℃~3
The method for producing a photographic support according to claim 2, wherein the temperature is 00°C. 5. For photography according to claim 2, 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 to 300 capes per molten film. Method for manufacturing a support. 6. The method for producing a photographic support according to claim 1 or 2, wherein the activation treatment on the paper substrate is a corona discharge treatment.