US3531362A - Spliced joint in coated web material and method of forming said joint - Google Patents

Description

Sept. 29, 1970 R. T. BOURNS ETAL 3,531,362

SPLICED JOINT IN COATED WEB MATERIAL AND METHOD OF FORMING SAID JOINT Filed Oct. 30, 1967 n W//"// m 6' Z/ lk 0 /2 Fla 2 LAW/FENCE G. M DONALD R/CHA/PD 7'. BOURNS.

. 4 ATTOR/V rs United States Patent Office 3,531,362 SPLICED JOINT IN COATED WEB MATERIAL AND METHOD OF FORMING SAID JOINT Richard T. Bourns and Lawrence G. McDonald, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Oct. 30, 1967, Ser. No. 679,083 Int. Cl. B32b 3/06 US. Cl. 161-39 Claims ABSTRACT OF THE DISCLOSURE A method for reducing coating disturbances at splices in a web being coated by treating the trailing edge of the splicing tape and the adjacent web surface with a material to prevent air entrainment in the coating.

Background of the invention In many manufacturing operations a substantially continuous web is coated with a liquid material, such as aqueous solutions or dispersions of hydrophilic colloids, see US. Pats. 2,681,294 and 2,739,891, which may then be dried to form the desired product. Such manufacturing processes are used in the manufacture of adhesive tapes, magnetic recording tapes and photographic films and papers, among others. In order to increase the efficiency, and consequently lower the cost, of manufacturing these products, the coating process generally is carried out in a substantially continuous manner. Inasmuch as the web or support for the coating can only be obtained in finite lengths, a new supply roll of the web must be periodically spliced to the end of the preceding supply roll so that the coating process may continue uninterruptedly.

It has been found that the most desirable way of splicing such webs is to utilize a splice tape extending across the web and joining the two adjacent pieces of the web together. It has also been found that applying the splice tape to the surface being coated provides fewer coating flaws than does the application of the splice tape to the back side of the web. However, even though the application of the splice tape to the coated side of the web results in fewer coating problems than do other methods of splicing, streaks and other defects have still been found in the coating downstream from the splice tape. Normally, the spliced section of the continuous web is cut from the finished product and is scrapped so that the defects in the coating occurring at the splice joint are not found in the final product. However, it has been found that under certain conditions, the splice joint may affect substantial lengths of the coated web following the splice. In many products, it is possible to cut out the affected portion of the web without substantially affecting the usability of adjacent portions. However, in many products this is not possible, and the entire web containing such defects must be scrapped.

As the speed of coating webs is increased and as the width of the web products is also increased, the value of the product being scrapped due to splice-imparted defects downstream from the splice have become excessive. This is even more true in high-cost products utilizing an expensive coating material which cannot be easily recovered from scrapped portions of the web. As a result, it has become increasingly important to minimize, it not eliminate, defects resulting from the splice from the coated web products. Moreover, the elimination of these defects must be accomplished without materially increasing the cost of the product.

Furthermore, the elimination of the splice-imposed defects must not in any way result in other, potentially less desirable defects in the coated product. Additionally,

3,531,362 Patented Sept. 29, 1970 the method of eliminating the splice-imposed defects must be readily accomplished without affecting the production rates now possible in high-speed coating machines.

Summary of the invention Accordingly, the present invention provides a method of treating a splice joint in a web to be coated, whereby the splice does not cause coating defects downstream of the spliced joint.

Many of the defects in coated webs appear to result from the entrainment of air in the coating deposited on the web or from the adherence of a small bubble of air to the coating nozzle, which then affects further portions of the coating deposited on the web. It has been found that such entrained air is picked up and such bubbles are generated as the coating drops down over the splice tape onto the surface of the web. The air being entrained appears to come from that trapped in the angle formed between the edge of the tape and the surface of the web.

Accordingly, the present invention provides a method of continuously coating a moving web with a layer of a substantially liquid material comprising the steps of moving the web past a coating head and depositing a layer of a substantially liquid material on a surface of the web. At spaced longitudinal intervals, a splicing member or tape is applied to the surface of the web being coated, with the splicing member forming a discontinuity in the web surface, at least at the downstream edge of the splicing member. Defects in the web coating are substantially reduced by preventing the entrainment of air from the downstream edge of the splice member.

More specifically, the elimination of air entrainment from the downstream edge of the spliced member is provided by coating the downstream edge of the splice membet and the adjacent web surface with an oily hydrophobic coating such as the marking solution from a felt tipped marker.

Additionaly, the prevention of entrainment of air from the downstream edge of the spliced member may be provided by feathering the downstream edge of the splice member.

Also, the elimination of air entrainment may be provided by coating the downstream edge of the splice member and the adjacent web surface with a coating of rubber cement.

The various features of novelty which characterize the present invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and the specific objects obtained by its use, reference should be had to the accompanying drawings and descriptive matter in which the preferred embodiments of the present invention are illustrated and described.

Brief description of the drawings FIG. 1 is a greatly enlarged schematic section through a spliced joint of a coated web which may be treated in accordance with the teachings of the present invention; and

FIG. 2 is a greatly enlarged schematic section through a spliced joint treated in accordance with an alternative method of the present invention.

Description of the preferred embodiment A sectional view through a web splice is illustrated in -FIG. 1, wherein the trailing end of one Web 10 is spliced to the leading end of a succeeding web 12 by a strip of splicing tape 14 which extends across the joint therebetween. In this illustration, the web moves past the coating station in the direction of arrow 16. The layer or coating 18 of a substantially liquid material, such as aqueous solutions (which term is also intended to include dispersions) of hydrophilic colloids and, more specifically, a gelatin-silver halide emulsion, is deposited at the coating section. It will be seen that the splice tape 14 creates a discontinuity in the surface of the web at both the leading and the trailing edges. It has been found that, as the spliced joint of the web moves past the coating station, the layer of substantially liquid material generally follows the discontinuous surface at the leading edge of the splice tape. However, a wedge of air 20 is trapped in the trailing edge of the splice tape and the coated layer does not closely follow the surface of the web at that point, especially at high coating speeds. The wedge of air 20 trapped between the coating material, the surface of the web, and the trailing edge of the splice tape has been found to become entrained in the liquid coating material as the coating material settles to the surface of the web. The entrained air may then be spread over the succeeding downstream portions of the web, causing defects in the coating which may result in rejection of the final product. More seriously, some of the trapped air 20 may form small bubbles which adhere to the surface of the coating nozzle and affect the stream of material flowing therethrough. These bubbles may persist for an extended length of time whereby all succeeding coating is affected. As a result, the amount of defective webs may be substantially greater than would be expected due to entrapment of air in the coating alone.

One method of preventing the entrainment of air in the subsequently coated web is illustrated in FIG. 2 (wherein similar reference numbers refer to similar elements) in which the trailing edge of the splice tape 14' is feathered or beveled so that no discontinuity is formed between the trailing edge thereof and the adjacent web surface. As a result of this treatment, no air is present at the trailing edge of the tape which may be entrained in the coating or which may adhere to the coating nozzle.

Another method of preventing the entrainment of air from the splice joint in the coating is to treat the trailing edge of the splice tape and the adjacent web surface with a filler material such as rubber cement, which performs substantially the same function as the feathered edge of the tape; i.e., filling the transition from the tape to the Web surface to eliminate the wedge of air at the trailing edge of the splice tape.

More surprising, however, is the discovery that air entrainment-caused coating defects may be substantially eliminated by coating the trailing edge of the splice tape and the adjacent web surface with a material which is not wet by the coating liquid and letting the volatile solvents evaporate before coating the web. In the coating of a water-based coating material, it has been found that superior results are obtained by simply marking the trailing edge of the splice tape and the adjacent web surface with a felt-tipped marking pen. As disclosed in US. Pat. 2,676,349, such marking pens have a marking ink which is comprised of a highly volatile carrier containing a pigment of finely divided solids. It has been found that one such marking solution carrier has a solvent composed substantially of aromatic hydrocarbons, predominately xylenes, and high flash naphtha. Apparently, this treatment prevents the immediate wetting of the trailing edge of the splice and the adjacent web surface by the coating material so that the coating material actually bridges the air wedge without permitting air to be entrained in the coating material or to form bubbles which may adhere to the coating nozzle as may occur when the coating material is immediately attracted to the web surface. More particularly, treatment of the trailing edge of the splice tape and the adjacent web surface with the solution from a Marks-A-Lot felt-tipped marking pen provided extremely satisfactory results.

It has also been found that an oily-hydrophobic material, such as a solution of oil in methyl-ethyl-ketone, also provides very satisfactory results.

Another material which has also been successful is a high flash naptha fraction containing a non-volatile fraction of oily material which also renders the web and tape surface non-wettable by the coating material.

While applying the treating coating to the web surface immediately adjacent the trailing edge of the splice tape, as by treating the web before applying the splice tape, provides satisfactory results, more desirable results are obtained by coating both the trailing edge of the splice tape and the surface of the web thereadjacent. At the same time, it has been found that merely coating the trailing edge of the splice tape alone does not eliminate the defects in the subsequent coating.

Accordingly, in the process of continuously coating the surface of a moving web with a substantially liquid material, the web is transversely spliced at spaced longitudinal intervals, resulting in a discontinuity in the surface being coated. The present invention prevents the formation of disturbances in the coating downstream from the spliced discontinuity by preventing entrainment of air in the coating, either by eliminating the Wedge of air at the downstream edge of the splice, or by the application of an oily-hydroprobic material to the splice discontinuity.

In extremely high speed coating operations it may be desirable to also treat similarly the leading edge of the splice tape.

An additional benefit of the preferred embodiment of the present invention; i.e., coating the splice with a marking pen, is the fact that the treated splice is readily apparent due to the color of the marking solution, so that any failure to treat the splice joint is readily apparent.

In addition, while the foregoing discussion has been directed to the formation of splices using a splice tape, the present splice treatment may be successfully applied to other types of splice joints such as lap joints between the two ends of the web.

We claim:

1. In the continuous coating of a moving web with a layer of an aqueous solution of hydrophilic colloids, the method of eliminating disturbances in the layer of said aqueous solution downstream from a spliced joint in the web comprising the step of preventing said aqueous solution from entraining air from the spliced joint by coating the web surface immediately downstream from the spliced joint with a hydrophobic oil prior to applying the layer of aqueous solution.

2. The invention according to claim 1 wherein the substantially hydrophobic oil is the marking solution from a felt-tipped marker.

3. The invention according to claim 1 wherein the spliced joint is formed with a splicing tape on the web surface to be coated.

4. In the continuous coating of a moving web with a layer of an aqueous solution of hydrophilic colloids, the method of eliminating disturbances in the layer of said aqueous solution downstream from a spliced joint formed with a splicing tape on the web surface to be coated comprising the step of forming a tapered transition from the downstream edge of the splicing tape surface to the web surface.

5. The invention according to claim 4 wherein the downstream edge of the splicing tape is feathered to the surface of the web.

6. The invention according to claim 4 wherein the transition is filled with an oily-hydrophobic material.

7. The invention according to claim 4 wherein the transition is filled with rubber cement.

8. The invention according to claim 1 wherein the hydrophobic oil consists essentially of a solution of oil in methyl-ethyl-ketone.

9. The method of coating a layer of an aqueous solution of hydrophilic colloids on a moving web comprising the steps of applying a splicing member to the surface of the web to be coated, said splicing member forming a discontinuity in the web surface at least at the downstream edge of said member, applying a hydrophobic oil material to the downstream edge of said member and the web surface adjacent thereto, and then moving the web and the splicing member past a coating head and depositing the layer on the web.

10. A web product having a splicing member applied to one surface of the web, said splicing member forming a discontinuity in the web surface on the downstream edge of the splicing member, said discontinuity and the surface of the web adjacent to and downstream of the discontinuity having a coat of an oily-hydrophobic material, and a coating layer of an aqueous solution of hydrophilic colloids disposed on said one surface of said web and said oily-hydrophobic material.

References Cited UNITED STATES PATENTS PHILIP DIER, Primary Examiner US. Cl. X.R.

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