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Publication numberUS3206323 A
Publication typeGrant
Publication dateSep 14, 1965
Filing dateJun 12, 1962
Priority dateJun 12, 1962
Publication numberUS 3206323 A, US 3206323A, US-A-3206323, US3206323 A, US3206323A
InventorsFrank D Miller, John J Wheeler
Original AssigneeEastman Kodak Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Coating high viscosity liquids
US 3206323 A
Abstract  available in
Images(1)
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Claims  available in
Description  (OCR text may contain errors)

Sept. 14, 1965 F. D. MILLER ETAL COATING HIGH VISCOSITY LIQUIDS Filed June 12, 1962 INVENTORS BY MK A/TRTMRNEYS Eomlnw E M3310 2250583 E52 op wuSwn m FRANK 0. MILLER JOHN J WHEELER E953 mm; $6035 23 United States Patent 3,206,323 COATING HIGH VlSCOSlTY LIQUIDS Frank D. Miller and John J. Wheeler, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed June 12, 1962, Ser. No. 201,869 3 Claims. (Cl. 117-34) This invention relates to a method for coating fluid compositions, and more particularly to a method for coating viscous fluids at high speeds.

Previous attempts to coat high viscosity fluids upon nonpermeable web support-s at high speeds such as at least 200 feet per minute have generally been unsatisfactory, primarily because air bubbles are entrapped under the coatings. The formation of these bubbles can be suppressed by the coating technique which involves supplying a ribbon of fluid coating from a stationary coating device, contacting the ribbon with a moving web support and subjecting the side of the ribbon adjacent the web support to a low-er pressure (pressure differential) than the opposite side of the ribbon, as described in U.S. Patent 2,681,294, issued on June 15, 1954 to Beguin. This coating technique allows good coatings at moderate speeds, but as the coating speeds are increased to 300 feet per minute and higher, correspondingly higher pressure differentials must be maintained to prevent bubble formation. However, the use of high pressure differentials introduces other problems in obtaining good coatings. For example, at high pressure differentials, it is difficult to hold the web support on the coating roll. In addition, it is diflicult to obtain coatings free of longitudinal streaks. Therefore, it appears desirable to provide a method for coating viscous fluids onto web supports at high speeds which overcomes the difficulties encountered by prior art methods.

One object of our invention is to provide a method of coating viscous fluids onto web supports at high speeds. Another object of our invention is to provide a method of coating viscous fluids onto web supports at high speeds without forming air bubbles in the coating. A further object of our invention is to provide a method of coating viscous fluids onto nonpermeable web supports at high speeds without the use of high differential pressures. Still another object of our invention is to provide a method of coating viscous fluids onto nonpermeable web supports at speeds above 200 feet per minute. A further object of our invention is to provide a method of coating viscous photographic emulsions onto nonpermeable support-s, such as baryta coated paper or cellulose ester film base, at speeds above 200 feet per minute.

Other objects of our invention will appear herein.

We have found that viscous fluids may be coated onto a web support at high speeds by the coating method which comprises forming a ribbon containing a distinct layer of the viscous fluid and a distinct layer of a low viscosity fluid coating composition, contacting the side of the ribbon composed of the layer of low viscosity fluid coating composition with a web support having an electrostatic potential different than that of said ribbon, simultaneously supplying the ribbon and the web support while moving the support across and in contact with the ribbon, and subjecting that side of the ribbon having the layer of low viscosity fluid coating composition to a lower pressure than the other side of the ribbon.

The drawing represents a diagrammatic view illustrating an apparatus which may be used to practice the coating method of the invention. The web support 1 is passed around a grounded metal roll 2 and under a device 3 for imparting a charge to web support 1. The web support 1 is then passed around guide roll 4 and thence around 3,205,323 Patented Sept. 14, 1965 grounded metal coating roll 5, .and past a stationary coating device 6 having inlet means 7 for a low viscosity liquid coating composition and an inlet means 8 to supply the viscous fluid coating composition. The low viscosity fluid coating 7 and the viscous fluid coating 8 pass through orifices L and L, respectively, and are simultaneously coated onto the web support 1 in distinct layer relationship as indicated at 10 and 11. A vacuum chamber 12 is provided to subject the ribbon of coating fluids to a lower pressure on the side of the ribbon composed of the layer of low viscosity fluid coating composition than the opposite side of the ribbon, and is provided with an evacuation pipe 13 attached to evacuating means not shown.

The utilization of a flow of ionized air to render a web or other sheet material electrically neutral or'to distribute an electrical charge on the surface thereof is well known in the art, and apparatus for generating such flows of ionizedair are disclosed in US. Patents 1,678,869, which was granted to M. Morrison on July 31, 1938, and 2,497,604, which was granted to P. Henry et al. on February 14, 1950.

The method of simultaneously applying multiple coatings is described in US. Patent 2,761,791, issued September'4, 1956, to T. A. Russell. Apparatus for applying simultaneously a plurality of coatings is described in US. Patents 2,761,417, issued September 4, 1956 to T. A. Russell et al., and 2,761,418, issued September 4, 1956 to T. A. Russell.

The method of coating fluids onto a support which involves employing a lower pressure on the side of the ribbon of coating composition adjacent to the web support than the pressure on the opposite side of the ribbon is described in U.S. Patent 2,681,294, issued June 15, 1954 to Beguin.

Our invention will be further illustrated by the following examples which demonstrate the necessity for incorporating all the aspects of applicants combination to achieve high speed coating of viscous fluids.

Example 1 A high viscosity 30% gelatin solution, having a viscosity of 3,000 cps., was coated at 110 F. onto cellulose ester film base at the rate of .5 to .18 lb. per square feet using a pressure differential of 4 inches of water pressure. The maximum speed of coating which could be achieved without the formation of undesirable bubbles was 213 feet per minute.

Example 2 A gelatin solution having a viscosity of 2,500 cps. was coated onto cellulose ester film base at the rate of .5 to .18 lb. per 100 square feet. A pressure differential of 26 inches of water pressure was required to achieve a good coating at a coating speed of 300 feet per minute. At a coating speed of 500 feet per minute, a pressure differential of 49 inches of water pressure failed to prevent the formation of bubbles in the coating.

Example 3 The procedure of Example 1 was followed except that a low viscosity (15 cps.) gelatin coating was simultaneously coated with the viscous fluid of Example 1 so that the low viscosity coating was adjacent the film base, in accordance with the method described by Russell US. Patent 2,761,791, at the rate of .04 lb. per 100 square feet. The maximum speed which could be achieved without the formation of bubbles was 280 feet per minute.

Example 4 A high viscosity 30% gelatin solution having a viscosity of 3,000 cps., was coated at F. on to cellulose ester film base to which had been imparted an electrostatic charge of 950 field volts. Bubbles were formed in the coating at a coating speed of 213 feet per minute.

Example A high viscosity gelatin solution, having a viscosity of 3,000 cps., was simultaneously coated (in accordance with the method described by Russell U.S. Patent 2,761,791) With a low viscosity (15 cps.) gelatin solution at 110 F. onto a cellulose ester film base to which had been imparted an electrostatic charge of 950 volts as measured against a grounded metal roll. The low viscosity gelatin solution was applied adjacent the film base at the rate of .04 lb. per 100 square feet with the high viscosity gelatin solution thereover at the rate of .5 to .18 lb. per 100 square feet. A pressure differential of 4 inches of water pressure was maintained in accordance with the method described by Beguin U.S. Patent 2,681,294. No bubbles were formed in coatings obtained at the coating rate of 500 feet per minute. The coatings were highly satisfactory in all respects.

The above examples demonstrate that a highly unexpected increased rate of coating high viscosity fluids on a web support is achieved when (1) a low viscosity fluid coating composition is simultaneously coated with the high viscosity coating composition, applying the layer of low viscosity fluid coating adjacent the support, by forming a ribbon containing a layer of the high viscosity fluid and the low viscosity fluid in bridging relationship between a stationary coating device and the Web support, (2) subjecting that side of the ribbon having the layer of low viscosity composition to a lower pressure than the opposite side of the ribbon, and (3) maintaining an electrostatic potential difference between the ribbon and the web support prior to the point of contact thereof. The examples further show that a drastic limitation in coating speed occurs when any one of the three requirements are omitted from the inventive method.

7 Our invention is generally applicable to coating viscous fluids at high speed onto web supports, particularly nonpermeable web supports such as a cellulose ester film base or baryta coated paper. The invention is especially well suitedto the coating of fluid gelatinous coating compositions, such as gelatino-silver-halide photographic emulsions and antih-alation pelloid backings, such as carbon black dispersed in gelatin. The low viscosity fluid may advantageously be a gelatinous fluid coating composition.

Other suitable low viscosity fluid coating compositions may be employed.

The viscosity of the fluids which may be coated in accordance with our invention range from 1,000 to 60,000 cps. Especially good results are achieved with fluid coating compositions having a viscosity in the range of 2,000 to 4,000 cps.

In some instances, it may be desirable to provide web supports having various coatings over the high viscosity fluid coating. Such coatings may be coated simultaneously With the high viscosity coating or subsequently applied either before or after drying the first high viscosity coating. These coatings may range from low to high viscosity.

The low viscosity coating compositions which are employed in the invention should have a viscosity of about 5 to cps., with particularly good results being achieved with coatings of 5 to 20 cps.

The differential pressure which may be employed in carrying out the invention may be from 1" to 10" of water pressure and preferably is about 4 inches of water pressure.

While we have found it convenient to obtain the required potential diflference between the web support and the coating fluid by the apparatus shown herein, there are many other means of achieving this potential difference which will be readily apparent to those skilled in the art.

The important consideration is that there be a different electrostatic potential between the web support and the coating composition prior to the point of contact. This total difference in potential should be between 800 and 10,000 volts, and preferably is about 950 volts.

The invention has been described in detail With particular reference to preferred embodiments thereof but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

-We claim:

1. The method of coating a fluid having a viscosity of 1,000 to 60,000 cps. onto a nonpermeable web support at speeds in excess of about 300 ft./min. which comprises:

(1) forming a ribbon containing both a layer of the fluid coating and an outer layer of a fluid coating having a viscosity of 5 to 50 ops,

(2) subjecting that side of the ribbon composed of the layer of fluid having a viscosity of 5 to 50 cps. to a lower pressure than the other side of the ribbon, the diiference in pressure being from about 1 to about 10 inches of Water pressure,

(3) contacting the side of the ribbon composed of the fluid having a viscosity of 5 to 50 cps. with a nonpermeable web support having an electrostatic potential different than that of said ribbon, said electrostatic potential difierence being from 800 to 10,000 volts, and

(4) simultaneously supplying the ribbon and moving the web support across and in contact with the ribbon.

2; The method of claim 1 wherein the fluid coating having a viscosity of 1,000 to 60,000 cps. is a gelatino silver halide emulsion, the fluid coating having a viscosity of 5 to 50 cps. is a gelatinous fluid and the web support is selected from the group consisting of baryta coated paper and cellulose ester film base.

3. The method of coating a gelatino silver halide emulsion having a viscosity of 2,000 to 4,000 cps. at speeds in excess of about 300 ft./-min. onto a web support selected from the group consisting of baryta coated paper and cellulose ester film base which comprises:

(1) forming a ribbon containing both a layer of the gelatino silver halide emulsion and an outer layer of a gelatinous fluid having a viscosity of 5 to 25 cps,

(2) subjecting the side of the ribbon composed of the layer of gelatinous fluid to a lower pressure than the other side of the ribbon, the difference in pressure being about 4 inches of water pressure,

(3) contacting the side of the ribbon composed of the gelatinous fluid with said web support, said web support having an electrostatic potential different than that of said ribbon, said electrostatic potential difference being about 950 volts, and

(4) simultaneously supplying the ribbon and moving the web support across and in contact with the ribbon.

References Cited by the Examiner UNITED STATES PATENTS 1,678,869 7/28 Morrison 317-2 2,497,604 2/50 Henry. et a1 28-22 2,681,294 6/54 Beguin 117-34 2,761,791 9/56 Russell 117-34 2,952,559 9/60 Nadeau 117-34 3,082,144 3/63 Haley 117-34 X WILLIAM D. MARTIN, Primary Examiner. MURRAY KATZ, Examiner.

Patent Citations
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3335026 *Jul 16, 1963Aug 8, 1967Gevaert Photo Prod NvMethod for coating liquid compositions employing electrostatic field
US3501330 *Oct 22, 1965Mar 17, 1970Agfa Gevaert NvManufacture of electrophotographic materials
US3502494 *Nov 4, 1966Mar 24, 1970Fuji Photo Film Co LtdProcess and apparatus for continuous fluid coating of a traveling web
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US3526528 *Oct 27, 1966Sep 1, 1970Fuji Photo Film Co LtdMultiple doctor coating process and apparatus
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US3547682 *Mar 15, 1968Dec 15, 1970Hercules IncComposite polyolefin extrusion coating of substrates
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Classifications
U.S. Classification430/531, 427/482, 118/621, 118/411, 118/50, 118/50.1
International ClassificationB05C5/02, B29C47/06, G03C1/74, B29C47/88, B05D1/26, B05C9/06
Cooperative ClassificationB05C5/0254, B05C9/06, G03C1/74, B29C47/8845, B29C47/145, B29C47/0021, B29C47/065, B29C47/0019, B05D1/26
European ClassificationB05D1/26, B29C47/14B, B29C47/06P, B05C5/02F, B29C47/88C4B, B05C9/06, G03C1/74