US2996646A - Antistatic device - Google Patents

Description

Aug. 15, 1961 R. M, WILSON ANTISTATIC DEVICE Filed Jan. 9, 1957 n l I l l RichardMWilson INVENTOR. Q BY N.

ATTORNEYS United States Patent Oiice 2,996,646 Patented Aug. 15, 1961 2,996,646 ANTISTATIC DEVICE Richard M. Wilson, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Jan. 9, 1957, Ser. No. 633,224 7 Claims. (Cl. 3'17-2) This invention relates to antistatic apparatus. More particularly it relates to a special roll construction which may be used in conjunction with the handling of photographic tilm under conditions where static electricity may be generated.

Itis well-known in industry that the handling of webs or `other attenuated material such as the passage of film over rollers or in sliding contact lwith other apparatus parts, particularly under conditions of high speed, considerable static electricity may be generated with the attendant problems and diiiiculties. While the problem of the generation of static electricity is encountered in a number of fields, such as in the textile industry, the paper making industry and the like, the problem' may be especially troublesome in the photographic field. That is, for example, in the manufacture of photographic film where the film carries a light-sensitive layer, it is apparent that static discharge, if it occurs in the vicinity of the light-sensitive coating, may cause damage thereto. Of course, in industry at large, as for example in industries Where webs are coated with coatings containing volatile solvents, the discharge of static electricity can present the hazard of igniting solvent vapors.

Accordingly, a considerable amount of work has been done in the field for reducing or minimizing the generation of static. Much of this work appears to involve applying so-called antistatic surface coatings on the materials being processed. That is, a considerable number of chemical compositions have been suggested which may be applied as treating agents or dressing to textiles, paper and the like for minimizing the formation of static. For example, in the photographic industry there is frequently applied to photographic film a separate layer known as an antistatic layer. There are, of course, many other procedures which have been suggested, such as wetting the surfaces and the like.

While, as indicated, considerable work has been carried out which can be generically referred to as surface treatment of the material being processed, there has been some work done `on apparatus construction and design for minimizing the static problem. For example, a number of apparatus constructions .have been provided which contain conducting devices adapted to be positioned in the vicinity of the moving web material, which conducting devices tend to drain off the static charges. Although the prior apparatus :and processes have aided in combating the static problem, as far as I am aware there is no complete procedure or apparatus that has been developed which entirely combats the problem.

It is apparent, therefore, that the development of means which further assist in reducing or minimizing static represents a highly desirable result. After extended investigation I have found apparatus construction which has substantial utility in the vhandling of web materials under conditions where static electricity may be generated. My apparatus is particularly useful in that it can be incorporated into existing equipment with a minimum of reconstruction and may be readily used in the conveying or other handling of web products which continue to carry the customary coatings or layers including antistatic coatings.

This invention has for one object to provide a construction feature on devices, which devices may be used in the conveying or handling of web material under conditions where static may be generated. A particular object is to provide devices which are useful in the photographic industry under conditions of contacting the photographic product wherein static electricity may be generated. A still further object is to provide devices of the ltype indicated wherein an antistatic component, rather than being present as a surface treatment, is internally incorporated into said devices or a part of said devices. A still further object is to provide a composite roll of a construction particularly adapted for the handling and conveying of photographic film under conditions where static electricity may be generated but wherein said roll construction minimizes or combats said static. A still further object is to provide devices of the type indicated Which lend themselves to ready and economical incorporation in existing equipment as a substitute or replacement for parts now in use which tend to produce a rather high quantity of static electricity.

I have found that certain parts of the equipment used in photographic work for handling film under conditions where static is generated may be constructed of plastic materials in which certain chemical agents, as will be described in detail hereinafter, are incorporated internally in said plastic. This internal incorporation in the plastic is in contrast to the surface treatment which has heretofore been employed. I have found that in so making these parts which contact the web material of plastic having internally incorporated chemical agent, that the generation of static is substantially minimized. I have further found in the construction of my invention that if the surface becomes dirty, such surface may be washed, shaved off or otherwise restored and the antistatic properties are still present. This is of considerable advantage over prior art procedures where the mere surface treatment was relatively temporary and incapable of restoration.

While my invention may be applied in the manufacture of various photographic equipment such as dark slides for sheet film holders, camera parts, conveyor parts in continuous processing equipment or conveyor parts for the handling of powders and other nely divided materials and the like, I will illustrate my invention with particular reference to a roll construction such as may be used in various photographic equipment wherein photographic rdm is conveyed at relatively high speeds.

For assistance in understanding of the present invention reference is made to the attached drawing forming a part of the present application. In the attached drawing the single figure shows a cross-section of a roll in accordance with the present invention.

In the attached drawings 2 and 3 are metal end plugs for forming the end portion of my roll. Such end plugs are provided with enlarged bored center sections 4 and 6 through which suitable axle members 7 and 8 may be extended. These axle means upon which the rolls may rotate would be carried in conventional bearing members 9 and 11. `It is suicient to point out that the various parts just referred to which govern the rotatability of the roll would be constructed in sufficiently careful practice so that the roll would be run true.

The end plugs 2 and 3 are provided at -12 and 13 with diange or skirt portions which are adapted to receive the outer cylinder `or tube member 14.

This tube member, as well as the end members, may be constructed from aluminum. This outer cylinder is fastened to the end plugs as at 16 and 17 by welding or in some other suitable manner.

Over this cylinder or tube member 14 in particular, and also preferably over the surface of end plugs 2 :and 3, there is positioned the plastic member of the present invention, designated 18.

In the broader aspects of this invention this plastic material may be comprised of various types of plastic.

However, it is preferred to employ a plastic essentially comprised of Ia phenol formaldehyde condensation product impregnated in a fibrous material. In any event, the plastic has thoroughly incorporated into it (rather than a surface treatment) certain chemical agents which will be described in detail hereinafter. This plastic having the agent internally inconporated therein, is inmly alixed to the outer surface of the roll. In this instance that the laminated `phenol formaldehyde product is employed in accordance with the preferred embodiment, such laminated plastic may be wound onto cylinder 14 then by heating, pressing and the like treatment, caused to attach firmly thereto.

In further detail, laminated phenol formaldehyde plastic sheet can be wound onto tube 14 while it is rotating on a mandrel. After a sufficient thickness, which may vary from 1/10 up to 1A", has been wound onto the metal cylinder under tension, the winding may be caused to set up with heat, leaving a surface which is then finished by machining to the desired degree of smoothness. The aforementioned Winding under tension is usually under sufficiently high tension as to impart pressure on the layer.

The roll of the present invention having the external plastic surface in which plastic surface certain chemical agents are internally incorporated, will operate in contact with moving webs without the generation of Vas much static as is experienced when, for example, metals rolls are employed. However, with my novel construction just described wherein there is a metal center such as the aluminum parts just described, such metal parts apparently may act as a conductor to drain oif static electricity through axle 7 and 8 and into the framework of the structure supporting the rolls.

Further details concerning plastic composition, the internally yincorporated chemical agent and other related data will be apparent from the following:

There are several plastic compositions in which the antistatic agents of the presentv invention may be incorporated for making the outer surface 18. However, I have found that the readily available commercial phenol formaldehyde condensation products comprise very useful plastic for the present invention. These plastic materials which are usually thermosetting may be made by the condensation of a phenol with an aldehyde by reacting these ingredients together for a period of time in the presence of either acid or alkaline catalysts. Usually alkaline catalysts such as sodium hydroxide, the various amines and the like may be used. However, the reaction of the phenol and the aldehyde to produce the resinous condensation product may also be carried out in the presence of certain acids. Also, while I refer to phenol, suitable plastics may also be derived from the reaction product of cresol, xylenols and the like phenolic homologues. Since various methods of manufacturing such phenol formaldehyde condensation products are known in the art, and since the exact condensation product is not a limitation on the present invention, further description on this aspect does not appear to be required. It appears adequate .to indicate that a suitable plastic material is manufactured or obtained.

Then this plastic material has thoroughly incorporated therewith a content of chemical agent which will act as an antistatic. One suitable procedure for incorporating the agent into the plastic comprises dissolving the plastic in a solvent and then adding a solution of the agent to the solution of .the plastic with mixing. In the instance of phenol formaldehyde plastics various common solvents may be employed such as, for example, ethyl alcohol. The solvent solution of the plastic is frequently referred to as a varnish. Then, as just pointed out, to the varnish is added a content of the Iantistatic agent or agents which it is desired to thoroughly incorporated Within the plastic.

The agent which I prefer to incorporate in the plastic is a sodium salt of the disulfonic acid formed by condensing two groups of naphthalene sulfonic acid with formaldehyde. This sodium salt of the disulfonic acid product just mentioned may be dissolved in water and the aqueous solution added to the varnish and thoroughly mixed therewith. Further details concerning the prepara* tion of this particular chemical additive may be found in British Patent 7,137 of 1913.

While the chemical agent just mentioned is the preferred additive, there are other chemical agents which may be employed. For example, in a comparable manner chemicals `such as: alkylated aryl polyether alcohols such as polyethylene oxide derivative of tertiary octyl phenoxy ethanol (Triton X100, mfg. by Rohm & Haas Co.) or Stearyl, dimethyl benzyl ammonium chloride (Triton X400, mfg. by Rohm & Haas Co.) can be incorporated in the plastic.

In accordance with my preferred embodiment, the above-described solutions lof the phenolic polymer containing the antistatic agent thoroughly mixed therewith would be employed lto impregnate a brous material such as paper or a fabric. In the impregnating process a roll of the web material, such as cotton fabric, on a mandrel is unwound over a guide means through the bath containing the plastic having the antistatic therein. From this impregnating bath the fabric is Withdrawn in contact with a scraper or other means for removing excess plastic from the fabric. The fabric which has been impregnated with the plastic containing the antistatic agent of the present invention, is then drawn through a long drying chamber heated in some suitable manner such as with hot air in order to remove most of the alcohol solvent above mentioned. This solvent, of course, may be collected in a recovery plant and reused.

In many instances it is preferred that a small amount of `solvent remain in the impregnated fabric since this prevents the plastic from becoming inflexible, thereby rendering further fabrication more diicult.

The impregnated material thus obtained in sheet form may then be wound under tension around the aluminum cylinder 14 in as many layers as is desired to produce an outer plastic `coating of from lAO" up to 1A" or more in thickness. The roll thus covered with the plastic may then be subjected to further treatment under heat and pressure for eliminating residual solvent, as well as causing the plastic to harden, thereby producing a roll which may be machined to a smooth finish.

In most instances where my roll is to be brought in contact with photographic film, I prefer to roughen the plastic surface somewhat by slightly 4abrading the plastic surface of the rol-l with an abrasive paper known as Trimite paper of a size varying from 1 to 400. This roughening of the surface of the roll is usually insuflcient that the roughness is visible to the eye. However, the roughness of the surface, of course, could be observed upon microscopic examination with a glass of low magnification. A further understanding of my invention will be obtained from consideration of the following examples which are set forth to illustrate the preferred embodiment.

Example I In accordance with this example the plastic solution which was prepared comprised about 450 lbs. of a phenol formaldehyde varnish. The source of the phenol formaldehyde condensation product was a commercial material known as Bakelite. To this varnish was added approximately 25 lbs. of the above-mentioned sodium salt of a disulfonic acid formed by condensing two groups of naphthalene sulfonic acid with formaldehyde. This chemical compound was dissolved in about 45 lbs. of water and the aqueous ysolution was thoroughly mixed into the varnish so that the chemical agent was well distributed through the plastic.

This plastic-additive liquid was then used to impregnate cotton duck in a manner as described above so that the cotton duck contained a content of plastic to the extent of approximately 45-55%. The cotton duck containing this plastic was then subjected to a temperature of approximately 300 F. for a short period of time to further polymerize the materials and harden the product.

The sheet thus obtained was then tightly wound onto an aluminum cylinder as already described, to a thickness of 1/s" in order to form the plastic roller in accordance with the present invention. The surface of the resultant roller was roughened slightly with abrasive paper.

Example II In accordance with this example a varnish solution containing the same additive as set forth in the preceding example was made up. However, in this example the liquid was employed to impregnate paper. The paper, after impregnation, was subjected to a brief heating at above 175 F. to obtain further polymerization. The impregnated paper was applied to an aluminum cylinder for forming a plastic exterior on the roll as in the preceding example.

The rolls produced in accordance with the above examples were rst tested by vigorous rubbing. No substantial static charge developed on the rolls of the present invention. On the other hand, comparable vigorous rubbing was performed on stainless steel rolls which had customr arily been used, and showed the presence of a rather substantial static charge.

'Ihen the rolls in accordance with the present invention were tested in contact with photographic film and a comparison made against stainless steel rolls which were used under substantially comparable conditions. The method used is substantially as described in H. W. Cleveland, I. S. M. P. T. E. 55, 37-44, July 1950.

In certain of these tests the film speed was 60 ft./min., film tension (35 mm. strip) 650 grams, angle of wrap film makes with test roller 60 degrees, relative humidity 50 percent, and room temperature 75 F.

The summary of data below arrived at from these various tests indicate the following:

When photographic films have an electrostatic charge level sufficiently high as to cause damage to photo-sensitive layers, it has been found that rollers made according to my invention will reduce the electrostatic charge on the film from 20% to 90% whereas a reduction of from only to 45% can be realized with stainless steel rollers. In each case the lower percentages are found in measurements taken when a non-conducting surface contacts the rollers while the higher percentages are found when the film surfaces contacting the rollers are conducting in nature.

Furthermore, when a photographic film which has no electrostatic charge is passed over several rollers in succession, it will tend to electrify at each roller passage until an equilibrium potential is reached. It has been found when using the rollers described in my invention, the equilibrium level will be only about 5 to 50% of that found in stainless steel rollers. The lower percentage is found with films having a conducting surface, while the higher percentage is found with films having a non-conducting surface.

The rolls of the present invention can be readily substituted for conventional metal rolls in photographic processing machines and will, from the mechanical standpoint, handle the film with equal facility but with less static problems as just indicated.

While in the above examples I have shown my roll made from a plastic containing a fabric type of material, and generally prefer that the plastic contain some bonding media, my invention is not limited to this exact construction. For example, in place of the cotton fabric described above, fiber glass and other similar materials may be used for the base which is impregnated. While, as indicated, phenol formaldehyde condensation products are preferred because of their favorable electrical and mechanical properties, in the broader aspects of the present invention the use of other suitable plastics is contemplated, as well as other methods of applying the plastic to the parts to which it is desired to give enhanced antistatic properties. For example, cellulose ester molding pellets may have thoroughly incorporated therewith the same additives as described in detail above. This molding material then may be melt extruded around the rolls in a manner generally comparable to the extrusion of insulation around wires. Likewise, while I have illustrated my invention with particular reference to rolls, the plastic of the present invention may be applied to other parts of photographic equipment where the parts are in contact with the moving film, and thereby reduce static generation. For example, on dark slides for sheet film holders the slide may be manufactured of plastic impregnated with the antistatic agent in accordance with the present invention.

The percentage of the antistatic agent may be varied from about 5% based on the weight of the plastic to as high an amount as is reasonably compatible without materially reducing the strength of the plastic. However, usually not more than about 20% will be required.

Other modifications and uses which may be made are of the following type:

For example, various other types of rollers may be manufactured in a similar manner for use in equipment employed for processing photographic film. The principles of the present invention may be used in processes where dirt accumulation is incurred by the presence of an electrostatic charge to minimize such accumulation; other uses may occur to those skilled in the art.

It is believed apparent from the foregoing description that improved apparatus parts have been provided, which parts have particular value in utilization under conditions where static may be generated but with considerably lessened and reduced static formation.

I claim:

l. A roll means particularly adapted for use in handling light-sensitive photographic film products under conditions where contact with the roll may cause static electricity generation, said roll comprising aluminum end cores provided with means `for receiving axle members, said end cores carrying skirt portions for receiving an aluminum cylinder member for forming the roll structure, a layer of laminated phenol fomaldehyde condensation plastic impregnated web encircling at least a major part of said aluminum cylinder, said plastic having a content of at least 5% of a sodium salt of an acid formed by condensing two groups of naphthalene sulfonic acid with formaldehyde thoroughly incorporated throughout said plastic, the external surface of said roll structure being slightly roughened, said roll exhibiting improved antistatic properties.

2. A process of restoring the antistatic properties of a roll having a structure in claim l which comprises removing a small portion of the plastic surface of said roll.

3. A process in accordance with claim 2 wherein the restoration is accomplished by soaking and washing the surface.

4. The process in accordance with claim 2 wherein the restoration is accomplished by mechanically scraping a thin layer from the surface.

5. An apparatus part particularly useful for contacting photographic film products under conditions where static electricity may be generated, said part being comprised of a metal inner portion and the outer portion which contacts the film being comprised of a relatively hard, machinable plastic section between V10 and 1A" thick, said plastic having incorporated substantially throughout the plastic a content of the sodium salt of disulfonic acid formed by condensing two groups of naphthalene sulfonic acid with formaldehyde.

6. A roll for use under conditions where static may be generated comprising a metal inner member, said metal inner member carrying an outer layer of plastic over substantially the entire metal member, said plastic being essentially comprised of a laminated phenol formaldehyde condensation product which contains 5 to 50% of a sulfonic acid derivative antistatic agentv thoroughly distributed throughout said plastic.

7. 'Apparatus parts for use in the photographic industry Where said parts contact photographic film under conditions where static may be generated, Said part being composed principally of a relatively hard plastic which may be machined and which contains distributed throughout the plastic 5-50% of a sulfonie derivative antistatic agent whereby said part exhibits improved antistatic properties.

References Cited in the le of this patent UNITED STATES PATENTS Hazell J an. 22, 1935 Cutler Aug. 20, 1935 Little Dec. 23, 1941 Kennedy Nov. 17, 1942 Harkins July 11, 1944 Holst Apr. 3, 1945 Rockoif Mar. 9, 1948 Luaces Apr. 12, 1949 Famulener Feb. 5, 1952 Garrett Nov. 18, 1958

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