SU1736626A1 - Extrusion-type spraying arrangement - Google Patents

Abstract

Usage: the invention relates to the production associated with the coating of solutions on a flexible substrate, and can be used to improve the quality of the coating applied from low-viscosity emulsions and solutions, while reducing the thickness of the coating and increasing the productivity of the process. SUMMARY OF THE INVENTION: The extrusion device is provided with an overlay with a sharp edge of a nonwettable material fixed on the outer face of the upper plate, while the distance between the sharp edge of the overlay and the irrigation edge is in the range from 0 to 0.5 mm. 3 il.

Description

The invention relates to the production of coatings from solutions on a flexible substrate, and more specifically to a technique for producing photosensitive film photographic materials.

A free-flow extrusion irrigation device is known, consisting of several plane-parallel plates, which are tightened with screws to form capillary slots and distribution channels. The photoemulsions to be applied and the solutions flow under the pressure of the supply from the capillary slots to the inclined planes, forming a single or multilayer flow that flows freely into the hanging meniscus. The latter is formed between the moving substrate and the irrigation edge of the device. The dimensions and geometry of the hanging meniscus determine the minimum possible thickness of the liquid coating to be applied under strong equal conditions. Known ratio

. hi

ABOUT)

where hi is the thickness of the liquid layer on the irrigation edge;

PA - the thickness of the applied layer.

The magnitude of the stretch ratio J depends on the viscosity of the solution, the speed of movement of the substrate, the vacuum in the vacuum chamber of the extrusion device, the size of the irrigation gap, and a number of other factors. For given values of these factors, the value of J is constant and, as follows from relationship (1). a decrease in the thickness of the coating ha can be achieved only by reducing the thickness of the liquid layer on the irrigated edge-at the entrance to the hanging meniscus.

VI

WITH

oh oh oh

A disadvantage of the known device is the impossibility of obtaining thin coatings. This is due to the relatively large value of hi, on the one hand, and the impossibility of reducing it in the known device, on the other.

Extrusion irrigation devices with forced supply of solutions to the hanging meniscus are known, consisting of several plates assembled together with the formation of capillary slots and distribution channels. The upper and lower plates have upper and lower irrigation edges, facing the hanging meniscus.

In these devices, several capillary slits face with their output cuts into the hanging meniscus and the thickness of the liquid flow hi is determined approximately by the sum of the widths of the capillary slits. Therefore, due to the high value of hi, using these devices it is not possible to obtain thin coatings.

The closest to the present invention is extrusion devices, in which several individual capillary slots converge into one, at the output slice of which a hanging meniscus with a smaller value is formed.

When using these devices for irrigating low-viscosity solutions (with a dynamic viscosity below 50 cP), the process of forming the hanging meniscus and coating as a whole, in addition to the viscosity forces, is exerted by the surface tension and wetting forces. Due to the wetting of the hanging meniscus with the outer face of the upper plate of the irrigation device, the wetting boundary is formed at a distance from the irrigation edge. Here, the wetting angle is 38-40 °. Under these conditions, the thickness of the liquid flow at the base of the hanging meniscus is hi. defined as the shortest distance from the curvilinear upper free boundary of the meniscus to the wetting boundary at the lower irrigation edge, has a large value well exceeding the width of the capillary gap h0. Therefore, using the known device, it is not possible to reduce the thickness of the coating P2 applied to the moving substrate,

With the help of the known device, it is not possible to ensure the required quality of irrigation, which is especially acute when irrigating thin layers of low-viscosity emulsions and solutions. This is caused by the uneven drying of the solution at certain points on the wetting boundary on the outer face of the upper plate of the device, where the liquid

practically motionless, and a stagnant zone is formed. Such local drying leads to a distortion of the straightness of the wetting boundary and, as a result, to longitudinal stripes that reduce the quality of irrigation. Therefore, when irrigating using a known device, in addition to the need for constant monitoring of the quality of irrigation, it is necessary to periodically interrupt

0 application process to remove the solution’s dryness (cleaning and washing), which reduces the productivity of the process.

The purpose of the invention is to improve the quality of the coating applied from low viscosity

5 emulsions and solutions, while reducing the thickness of the coating and increasing the productivity of the process.

This goal is achieved by the fact that the known device, consisting of several plates assembled together with the formation of capillary slots and distribution channels, in which the upper and lower plates on the output slice of the capillary gap have upper and lower irrigation edges, is provided with an overlay with a sharp edge of a nonwettable material fixed on the outer face of the upper plate, while the sharp edge of the lining is located in any of the positions: from the position flush with the irrigation edge to the position at which The distance between the edges does not exceed 0.5 mm.

The presence of a lining made of a hydrophobic material, the sharp edge of which is located 5 flush with the upper irrigation edge or at a small (not more than 0.5 mm) distance from it, leads to a narrowing of the thickness of the liquid flow hi and according to the ratio (1) to a decrease in the thickness of the coating ha . The constriction of the liquid flow at the inlet to the meniscus leads to high values of the gradient of the shear strain rate at the flow separation point, i.e. exclusion of the quasi-stagnant zone. By virtue of this and the formation of a clear

5, the flow separation boundary with a discrete transition from non-wetting to wetting eliminates the drying of the solution on the separation line and the occurrence of irrigation bands. As a result, in addition to ensuring the very possibility

0 watering thin layers is achieved increasing its quality. At the same time, the elimination of the need to periodically interrupt irrigation for cleaning and washing the separation boundary leads to an increase in the productivity of the process.

FIG. 1 shows the device; in fig. 2 shows an embodiment of the patch as a separate plate; in fig. 3 shows an embodiment of an overlay assembled in one piece with the plate.

The device comprises upper and lower plates 1 and 2, screwed together with each other to form a distribution channel and a capillary gap. On the face cheeks 3, a fastening film 4 is installed with clamping screws 5, which are pressed into the plate 6, fixing the lining of the nonwettable material 7 on the outer face of the plate 1.

The lining can be made as a separate plate or film of non-wearable material with a sharp edge 8 (Fig. 2), or assembled with the plate 6 (Fig 3). In the latter case, a reciprocating displacement mechanism can be provided the faces of plate 1 and fixing the lining in any position relative to the upper irrigation edge 9 Fluoroplast or other material with low surface energy can be used as the lining material

The device works as follows.

When liquid is supplied from the capillary gap to the irrigation gap between the irrigation edges and the moving substrate, a hanging meniscus is formed. An acute edge of the pad of nonwettable material narrows the liquid flow hi at the base of the meniscus and thus provides the possibility of reducing the thickness of the applied coating.

Using a new element - lining with a sharp edge of non-wetted

The material allows thin layers of emulsions and solutions to be applied with high quality irrigation. The latter is achieved by eliminating the conditions for the formation of longitudinal strips on the liquid coating.

The use of the proposed device in irrigation conditions on laboratory or semi-production machines is most effective when one or two layers are applied simultaneously using an extrusion device with forced feeding of solutions into the hanging meniscus.

Claims (1)

Invention Formula An extrusion irrigation device consisting of several plates assembled together to form capillary slots and distribution channels, in which the upper and lower plates on the exit slice of the capillary slot have upper and lower irrigation edges, different in that improving the quality of the coating applied from low-viscous emulsions and solutions, while simultaneously reducing the thickness of the coating and increasing the productivity of the process, it is provided with a pad with a sharp edge of non-wetted material, fixed on the outer face of the upper plate, while the distance between the sharp edge of the lining and the irrigation edge is in the range from 0 to 0.5 mm. 1 Thebes. 2 "D-0