CA1170125A - Conductive films containing plastic particles and a conductive agent - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An improved conductive film comprising a polymeric film-former, a conductive agent, and an amount of plastic particles sufficient to enhance the performance of the conductive agent. The film may or may not be treated with a solvent capable of substantially coalescing said plastic particles. A preferred film-former is a copolymer of at least 60% ethylenically unsaturated polymerizable monomer having non-polar functionality and about 3% to about 40% of a polymerizable olefinically unsaturated monomer having polar functionality. A preferred conductive agent is an anionic conductive polymer. The present invention has particular application in the preparation of electrostatic masters.

Description

The present invention relates to a novel process for making conductive paper containing elec-troconductive films and such conductive paper prepared by the process. The present invention has particular application in the preparation of electrostatic masters for lithographic prin-ting, and will be described with particular reference to the same, although it will be apparent to those skilled in the art that the present invention has other applications, for instance the preparation of electroconductive copy paper for use in electrophotoyraphic methods of reproduction, conductive backings for carpets, and antistatic treatment for films which ordinarily are dielectric.
In the photoelectrostatic process, a layer oE photo-sensitive zinc oxide or other photosensitive material, dispersed in a high dieletric binder, is first given a blanket negative electrostatic charge, for instance in the presence of a carona discharge. An image is then projected onto the charged surface using light at wave lengths to which the zinc oxide is sensitive, causing the electrostatic charge to be dissipated in the illuminated areas. The latent image in the form of a negative charge is developed with a toner or developer, which may be either a dry developer powder with an opposite charge, or a wet developer. The latter is a suspension or dispersion of toner or colored pig~lent in a suitable organic carrier. The resulting deposited image powders or colored pigments are then fixed, usually by the application of heat~ solvent evaporation, or pressure, to form a permanent image.
It is well known that the substrate or subcoats lmder the photosensit:ive coat must have a minimum conductivity to prevent a dielectric barrier which leads to toning or reverse imaging in the finished copy. Many types of compounds for this purpose have been used or proposed to treat the sub-strate, for instance paper, or to be added to subcoats applied to the paper. These include hygroscopic inorganic salts, humectants, conductive carbon black, electroconductive polymers, anionic polymers such as sulfonates, phosphates and carbonates, and cationic conductive polymers, principally quaternary ammonium resins. The ca~ionic conductive polymers are generally preferred because of their ability to impart a high degree of conductivity to a subcoat even at low humidity, and because of other properties. However, they suffer from the disadvantage of being high in cost. In addition, substantial water resistance is usually desired of a subcoat. Binders suitable for this purpose are film-forming water resistant latices, such as styrene-butadiene or polyvinyl acetate, bu~ the cationic con-ductive polymers are incompatible with such latices. The use of other conductive agents is generally inadequate, due to either a lack of compatability or the amount of conductive material that would have to be used which would significantly impair water resistance.
Carbon black has been used as a conductive agent with latex coatings. It has ~he advantage that it does not signifi-cantly increase the hydrophilicity of the film. However, carbon black imparts a color to the base paper which might be considered objectionable. Because of this color, at low coat weights, a very unsightly sheet is obtained.
In addition, the amount of conductivity obtained from carbon black is very dependent Oll the degree of milling and is known to be erratic.

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Manufacturing problems such as cleanup and contamination of equipment present serious barriers to the use of this tech-nology. In practice, a coater has to be dedicated to this type of production. In addition, carbon unduly increases the cost of the master base paper.
In the case of electrostatic masters for lithographic printing, a special problem exists. The master is first imaged and then is placed on a plate cylinder of an off-set duplicating press. The overall surface of the plate is treated wi~h an aqueous wet-out or fountain solution whic~h wets all portions of the plate except those areas which have been imaged or are water-repellent. The press inking rolls then pass over the surface of the plate and deposit a film of ink only on the ink-receptive imaged areas. In the printing operation the ink from the imaged areas is transferred in reverse to a rubber off-set blanket which in turn prints directly onto a paper sheet so as to form a copy.
If the aqueous fountain solution works into the body of the paper, the surface of the plate may become less completely wetted-out by water because water has withdrawn from the surface into the plate. Therefore, the surface may not repel the printing ink and areas of the surface which should be perfectly blank will darken or "tone".
In addition, absorption of water into the base paper is likely to cause fiber swelling and dimensional expansion in a cross-machine direction in turn causing buckle or what is known as cockle of the master. As the master enters various nips on the printing press, the cockle is flattened creating a crease; this crease then picks up ink which reproduces on copies causing a streak.

Conventional barrier coatings used in the construct.ion of lithographic paper masters are described in United States patent Nos. 3,298,831l issued to Lau; 3,653,894, issued to Levy;
3,839,033, issued -to ~atsuno; and 3,787,235, issued to Honjo.
The use of natural and synthet.ic adhesives to prov.ide surf~ce strength and water resistance to lithographic masters are summarized in TAPPI monograph ~os. 36 and 37, by the Technical Association of the Pulp and Paper Industry (TAPPI), .~tlanta, Georgia.
The present invention provides a process for makiny a water resistant, coated, conductive paper having a conductive film on a paper substrate comp.rising the steps of: applying to said paper substrate a conductive water based, barrier coat formulation characterized by the presence thereIn of a film forming amount of a polymeric film former which is water soluble or water dispersible, a conductive amount of conducti~e agent, and an amount of organic ! water insoluble and film former insoluble, thermoplas-tic non film-forming plastic particles~
having a particle size in the range of from about 0.01-20 microns sufficient to enhance the conductivity of th.e conduct.ive agent; and drying the coated paper substrate, the film having a moisture content equivalent to that obtained by conditioning the film to a humidity of about 50% or higher.
~ ccording to one preferred embodiment o~ the in~enti:on, a paper substrate which prior to the coating process as described above has been precoated with a precoat compris~ng filler and binder, and dried The precoat may include from about 10% to 20% o:E the total filler content of organic, water insoluble film-former insoluble, thermoplastic non film-forming plastic particles having a particle s;~ze in the range of from about 0.01 to 20 m;~crons~

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According to still preferred embodiment of the invention, the precoated and then coated with the film forming polymer, is overcoated with a composition containing an organic solvent to partially coalesce the plastic particles. The most preferred composition is a zinc oxide slurry for rendering the surface photoconductive.
Although the present invention is not limited to any particular theory as to the reason for its e~fectiveness, it is believed that the .~

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plas-tic particles open -the film sufficient -to allow the penetrat-ion or retention of moisture which enhances conductivity. Because of the improved conductivity, the amount of conductive agent, which is hydrophilic, can be reduced, in turn improving water resistance. Alternatively, the present invention provides a means for obtaining higher conductivity than heretofore available where maximum conductivity is desired.
The present invention is directed to a film containing the plastic particles and a conductive agent. The film is applied to a paper substrate, and it is applied from an aqueous system, which may be a solution or emulslon.
In an embodiment of the present invention, in the pre-paration of electrostatic masters, the film of the present in-vention is applied to a paper substrate as a barrier coat and is first dried. Either by retention of water in the drying process or by conditioning of the paper at 50P6 or higher relative humidity, water is caused to be bound to the conductive agent by virture of hydration. This improves conductivity~ The incorpor-ation of plastic particles in this invention allows the conductive film to breathe or retain water from the atmosphere. The con-ductive film is then treated with a solvent capable of coalescing the plastic particles, such as from a zinc oxide top-coat wherein the zinc oxide is dispersed in toluene. The plastic particles swell or dissolve which resul-ts after evaporation of the solvent in the plastic particles being cast as coalesced, semi- or totally continuous water resistant film. Again, although not intending to be bound by theory, it is believed that the con-tinuous film seals in the water bound to the conductive agent, the bound water in turn enhancing performance of the conductive agent in the electrostatic master.

Formation of a coalesced film from the plastic particles .h~' '~
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is disclosed in United States Patent No. 4,272,569 lssued June 9, 1981. As disclosed therein, coalescence of the plastic particles can be carried out by application of a solvent such as toluene to the barrier coat independent of an prior to the zinc oxide coat, if desired.
A large number of prior patents have been granted on the use of plastic particles in paper coating formulations. Rep-resentative United States patents are Nos. 3,96~,319; 3,949,138;
3,799,800; 3,996,056, and 3,281,267. Insofar as is known, no patents have issued disclosing the use of plastic particles in a film or coating formulation to obtain improved conductivity.
Examples of suitable materials which may be employed in the preparation of plastie particles, sensitive to a solvent such as toluene, to effect water or solvent resistance, include polystyrene, polyvinyl acetate and copolymers thereof, polyvinyl butyral and copolymers thereof, polyacrylates and copolymers thereof, and mixtures of any of the above.
A suitable range of sizes for the plastic particles used in the present invention is about 0.01 to about 20 microns. The amount of plastic particles employed in the conductive film may vary over a wide range, depending upon properties desired of the film, for instance between about 5% and about 100%, based on the dry weight or solids weight of the film-forming polymer or other binder composition employed. Preferably, however, the plastic particle content is about 20 to about 40% based on the dry weight of film-forming polymer.
It is well known to add particulate inorganic material to polymeric films. For instance, an inorganic f;ller such as calcium carbonate or clay is a very common film additive, particularly in the paper coating art. Such ~,t~

fillers may function to open a plastic fi:Lm in somewhat the same way the plastic particles of the present invention open a film.
Still, conventional fillers are no-t w:ithin the scope of the present invention. Usually, a conductive film, whether for an electrostatic master, for carpet backing, or for some other application, must possess other properties than conductivity; for instance water or solvent hold-out. Conventional inorganic fillers, while opening the film, may adversely affect such other properties. For instance, conventional inorganic fillers may themselves be water absorptive, adversely affecting water or solvent hold-out. The plastic particles of the present invention constitute an improvement over the use of inorganic fillers in that they have less of an effect on the overall film integrity.
Broadly, the film-former of the present invention can be any synthetic or natural polymer having film-forming prop-erties, such as natural binders, including starch, modified starch, casein, and soybean protein; or modified starch binders such as oxidized, enzyme-converted or hydroxyethylated starch;
and synthetic binders including the styrene-butadiene latexes;
the acrylic resin emulsions, especially aqueous dispersions of polymers of copolymerized ethylenically unsaturated carboxylic acid; the latexes of copolymers of butadiene and acrylonitrile, vinyl acetate and the acrylates, butadiene and methyl metha-crylate, vinyl chloride and vinylidene chloride; and homopolymers of butadiene, methyl methacrylate, vinyl acetate, chloroprene, vinyl chloride, and butyl methacrylate; as well as polymeric materials which are at least partially soluble in an aqueous media such as polyvinyl alcohol, partially hydrolyzed polyvinyl acetate and totally or partially hydrolyzed polymers of styrene and maleic anhydride.

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In a preferred embodiment, the film-former is a copolymer of at least 606 ethylenically unsaturated poly.merizable monomer having non-polar functionality, such as ethylene or propylene, and about 3% to about 40% of a polymerizable olefinically un-saturated monomer having polar functionality, such as acrylic, methacrylic or crotonic acid, or salt thereof. An especially preferred such copolymer is an ethylene acrylic acid copolymer marketed under the trademark XD 8931 by Dow Chemical Company, containing about 80% ethylene and 20% acrylic acid~ Such co-polymers are disclosed in United States Patent Nos. 3,520,861 and 3,799,901.
The amount of film former employed should be at least abinding amount, although more than a binding amount may be used for improved picking resistance and other properties. By binding amount, it is meant sufficient to bind the solids of the coating formulation to a substrate. Normally, it ~ill be at least about 10% of the coating formulation.
In addition to plastic particles, the film or coating of the present invention can contain other pigment materials, for instance, clay, silica, calcium carbonate and alumina, which may be added to the plastic particle ~ormulation to provide properties such as smoothness to the film or coat. The nascent film or coating of the present invention may be formed or applied in any way, for instance with equipment well known in the art oE
coating, examples of such equipment being a size press, a rol]
coater, a blade coater, an air knife, and a rod coater.
~ he present invention is useful with all conductive agents that are compatible with the film forming polymer being used. Included are conductive agents such as conductive carbon, anionic and cationic conductive polymers, montmorillonite clays, hydrated alumina, colloidal alumina and silica~ conductive salts, and humectants. Particularly effective :results are ob-tained with anionic conductive resins such as sodium polystyrene sulfonate (SPSS) and sulfonated styrene maleic anhydride (SSMA).
Another particularly effective conductive agent is a hydroxy~
alkyl-trialkyl ammonium salt such as choline chloride, compatible with most conventional film-forming binders. Choline chloride and methods for making the same are disclosed in United States patent No.2,655,541. Choline chloride is obtainable either as a dry free-flowing powder or in solution form. One suitable formulation of choline chloride is a 70% aqueous, clear solution sold by Diamond Shamrock, Co. under the trademark "Nopco Choline Chloride 70%".
This solution can be added directly to the binder/plastic particle formulation.
In place of chlorine the negatively charged radical of the compound can be a phosphate, sulphate, acetate, nitrate or other halide. The hydrogen substituting groups on the nitrogen atom can be any alkyl radical having from 1-3 carbon atoms or mixtures thereof, e.g.,trimethyl, triethyl and dimethylethyl.
Reference can also be had to Miller patent No.3,798, -032, on the use of choline chloride as a conductive agent in coating formulations. No reference is made in this patent to enhancing conductivity by employing plastic particles in the formulation.

_ 9 _ ~ ~'7(~ ~ Z 3 Also illustrative of a suitable electroconductive agent is a quaternary am~onium salt such as bis (2-hyclroxyethyl) dimethyl ammonium chloride, described in patent No. 3,928,695. ~le salt is used to prepare an electroconductive latex said to be particularly useful as a textile backing composition. Other United States patents of interest on electroconductive films are 3,814,703; 3,681,070; and 3,898,185.
The amount of conductive agent employed is dependent upon the type of agent used, and also on the dieIectric properties of the filmrformer. Generally, the conductive agent will be employed in small quantities, for instance in the range of about 2-10%, preferably about 5% + 2% With further addition oE the conductive material, a trade-off with water resistance can be expected.
More particularly, the amount of conductive agent should be sufficient to establish in combination with the plastic particles a resistivity of less than akout 1011 ohms per square.
In certain cases, it may be desirable to employ a precoat or subcoat underneath the conductive coat of the present invention, particularly in the preparat~on of paper based products where water resistance is desired; or with ot~er types of substrates sensitive to abso~ption of 2Q water. Ihe function of the precoat also is to smooth irregularities in the surface of the base paper or other substrate. Such precoats are well known and will compr;~se typically a styrene-butadiene, acrylic or poly-vinyl acetate latex or polymer formulati`on containing conventional barrier additives such as protein, casein, clay, pigments and fillers~
Prefera~ly, the precoat formulations of the present invention also compr~se an am~unt of plastic particles, in the range of about 10-20%
based on the total filler content, to enhance water resistance.

Where total or substantial coalescence of the plastic particles is desired, the plastic partieles in the conductive coat of the present invention should be sensi-tive to a solvent as toluene, benzene, xylene, chlorinated aliphatic compounds such as methylene chloride, and ketones such as acetone and methylethy:L ketone. By sensiti~e, it is meant that the plastie particles becc~e swollen or partially or totally dissolved by the solvent to which they are exposed, such that when the solvent used is evaporated, a semi- or totally continuous plastic film is formed. In -this regard, the diserete plastie partieles of the present invention shouLd be non film-forming under eonclitions of formiLation and coat applieation, wa-ter insoluble, and insoluble in the partieuLar binder employed in the conductive eoating formulation.
By "non filmrforming", it is meant that the dispersed plastie partieles do not eoalesee to form a fi`lm at ambient temperature on eoat application, or at temperatures and pressures seleeted to dry or finish the coated substrate, In the case of preparation of lithographie masters or electro-eonduetive paper for use in eleetrophotographie methcds of reproduction, where a photoconduetive topcoat is applied over the conduetive eoat, the solvent of the pho-toconduetive eoat such as toluene may eonstitute, as indieated, the agent for eausing eoaleseence of the plastie partieles in the conductive eoat.
Alternatively, the present invention can be earried out without any eoaleseence of the plastic particles tc~ards preparation of an improved conductive film.

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In the manufacture of the coatings of the present invention, conventional methods known in the art can be employed.
Specifically, the coat formulations can be applied at coat weights desired, depending upon properties required using con-ventional equipment mentioned above. A subcoat or precoat may or may not be used. Following application of the conductive coat, the coat is dried and may be calendared, again depending upon application and use of the final product. If water resistance is desired in the fina] product, a preferred range for the coat weight of a precoat is about 0.5-15 pounds per side per 3,300 sq.
ft. A preferred range for the coat weight of the conductive coat then is about 0. 2 to 10 po~mds per side per 3,300 sq. ft. Norm-ally, the conductive coat will be applied to only the functional side of the substrate, where water resistance is required, but it may be desirable to apply it to both sides, for instance to avoid curl.
In the following examples, percentages are weight percentages ~mless otherwise specified.
E XAMP LE
This Example illustrates the dramatic improvement in efficiency of anionic conductive polymers achieved by ~he use of an amount of plastic particles in preparation of a conductive film. A stock solution of a 10% solids sodium polystyrene sulfon-ate ~SPSS), 500,000 molecular weight, marketed by National Starch Co. under the trademark Versa TL 500, was made and added to a first series of solutions of ethylene acrylic acid ~EAA), marketed by Dow Chemical Co. under the trademark XD 8931; and to a second series of ethylene acrylic acid solutions containing an amount of styrene plastic particles DPP-722 trademark Dow Chemical Co., in the proportion of 75% EAA,25% plastic pigment, dry basis. The conductive polymer was added, in the several samples, in the ~7(~

proportions of 1%, 2.5%, 5%, lO%, 15% and 20%, clry basis, total weight of the resulting formulations.
In add:ition, a similar series of blends (with and without plastic particles) were made employing a sulfonated styrene maleic anhydride polymer Versa 78-~301, trademark National Starch, at the 1%, 2.5%,5%,10%~1~0and 20% levels. In the preparation of all of these formulations, no incompatibilities were noted.
Ten mil thick wet films were cast on Mylar film and oven dried three minutes at 150C.* r~le films were conditioned at 50%
relative humidity and the surface electrical resistivities (SER) were determined with a Keithley Elec~rometer. The following Table l shows the effect of sodium polystyrene sulfonate and sulfonated styrene maleic anhydride polymer, at different levels in ethylene acrylic acid films, on the surface electrical resistivity. As the amount of conductive polymer is increased, the surface electrical resistivity decreases. This is expected. In addition, however, the table shows the dramatic decrease in surface electrical resistivity achieved by the addition of an amount of plastic particle to the respective formulations, dramatically illustrating the improved efficiency of the conductive polymers achieved by the presence of plastic particles. ~or instance, the addition of 25%
Dow plastic pigment to Versa TL 500 at 5% with ethylene acrylic acid, yielded a ten thousand-fold decrease in resistivity, or ten thousand-fold increase in conductivity. This is unexpected.
Significant improvements were also obtained at the 2.5% and 10%
levels of conductive agent, the practical limits of use of con-ductive agents.
The significance of this example is that an effective conductivity of, by way of example, less than 101l ohms/square resistance, can be obtained by the use of much lower levels of *In this example, there was no surface treatment of the cast films following drying, such as with a solvent capable of causing coalescence of the plastic particles when used.

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conduc-tive agent than would otherwise be necessary. For instance, 5% Versa Tl.-50n conduc-tive polymer wi-th DP-722 plastic particles gives nearly the same resistivity as 10% Versa TL-S00 without plastic particles. Although the data with Versa 78-4301 is less dramatic, a similar advantage was achi.eved with this conduc-tive polymer. Since the conductive agents are hydrophilic, this means that a more water resistant film can be obtained without losing conductivity.

Conductive Resistivi-ty Agent oms/square_ with without % Versa TL-500 plast:ic particles pla ic particles ] 3.50 x 10143 7 x 101~

2.5 1.06 x lOlo 6.5 x 1014 5.0 7.50 x 109 5.5 x lOlo 10.0 1.05 x 18 1.3 x 10 8 15.0 3.3 x 1~ 1.13 x 18 20.0 1.9 x 10 1.08 x 10 % Versa 78-4301 l 2.5 x lol41 7 x 10141~
2.5 2.8 x lOlo 2.8 x lOlo 5.0 1.8 x 18 9.5 x 10 9 10.0 7.5 x 18 1.20 x 10 15.0 2.8 x 10 1.8 x 108 20.0 1.7 x 108 1.1 x 108 Again, the reason for the effectiveness of the present invention is believed to be that the plastic particles open the film an amount sufficient to allow the penetration of some moisture~ sufficient to markedly increase conductivity. At the same time, the integrity of the film was maintained so that very little or no loss of overall water resistance was noted due to the presence of the plastic particles.
For instance, in the case of the use of Versa TL-500, at the 5% and 10% levels, the presence of the DPP--722 plastic particles had very little effect on the percentage water ab-7~

sorption after one hour immersion. At 5% level of addi~ion, it remalned constant at about 2-3%. In the samples employing 5%
Versa 78-4301, the presence of plastic particles also had little effect on water resistance; water absorption here after one hour immersion increasing slightly from about 6% to about 8.5%.
EXAMPLE II
This example illustrates the improvement of the present invention achieved with the use of plastic particles, in combi-nation with a conductive polymer, in the preparation of a litho-graphic master.
A paper whose basis weight was 61 lbs. per 3,300 sq. ft. and contained a wet-strength resin, was given to both sides a conventional precoat of 7 lbs. per 3,300 sq.ft. per side. This coat consisted of, on a weight basis, about 80% clay, about 5% soybean protein and about 15% styrene-butadiene latex ~including about 10% melamine formaldehyde cross-linking resin based on latex weight). The paper was dried, given a light calendaring between two steel rolls and then was coated in a first series of runs with two barrier coating formulations, one consisting of ethylene acrylic polymer (Dow XD-8931, trademark Dow Chemical Co.) in combination with varying amounts of sodium polystyrene sulfonates (SPSS), marketed under the trademark Versa TL 500, molecular weight 500,000, by National Starch, and a second series of runs with the same ethylene acrylic polymer, and varying amounts of conductive polymer, in combination with 25%
styrene plastic particles (Dow 722, trademark Dow Chemical Co.), based on the weight of ethylene acrylic polymer. The coating formulations were applied by rod coating on the precoated base at a coat weight of about 3.3 lbs. per side per 3,300 sq. ft.

The paper in each run was then coated with a 50% zinc oxide dispersion in toluene containing about 5% vinyl acetate-f~

l'7~Z5 acrylic binder at a coat weight of 23.5 lbs. per 3,300 sq. ft.
and was then dried. The samples were imaged with a dry toner, Addressograph-Multigraph 2300 Copier at a No.6 exposure. The amount of mot-tle and background present was judged to be very poor (VP), poor (P), fair (F), good (G), or very good (VG), relative to a standard commercial procluct. These data are presented in the followi.ng Table II. All samples were conditioned to about 50% relative humidity prior to testing.
TABLE II

Physical Properties of ZnO Coated Masters on Conductive Barrier Coated Paper Using Plastic Particles and a 5Onductive Raw Stock % % Barrier Coat 60 minute Image(l) Dow 722 in Versa TL 500 weight Cob~ Test Test Barrier Coat in Barrier Coat lb/3300 sq.ft. g/m2 0 1.0 0.5 10.8 P
0 1.0 1.0 4.5 F
0 1.0 3.3 2.1 F
0 1.0 5.0 1.6 P

1.0 0.5 9.7 G
1.0 1.0 5.2 VG
1.0 3.3 2.4 VG
1.0 5.0 1.8 G
(1) AM 2300 copier #6 exposure From the data in Table II, it is apparent that very good imaging characteristics can be obtained if 25% plastic pigment is incorporated with 1% Versa TL 500 without any sacrifice in water resistance (Cobb Test). By comparison, if no plastic pigment is used, poor or marginal imaging characteristics are obtained. This appears to hold true over a ten-fold increase in coat weight. Alternatively, one can obtain very good imaging characteristics at higher levels of con-ductive agent but at loss in water resistance and corresponding run length of the master. For instance, it was found that a 2.5% addition of Versa TL 500 gave very good imaging characteristics but could result at a coat weight of 1 lb/ream in a 50% loss in water resistance (Cobb Test 11.2 vs. 5 ).
The Cobb Test is a standard test for measuring water absorp-tion, described in TAPPI Standards ~ Testing Methods P441M.
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Claims (14)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for making a water resistant, coated, conductive paper having a conductive film on a paper substrate comprising the steps of:
applying to said paper substrate a conductive water based, barrier coat formulation characterized by the presence therein of a film forming amount of a polymeric film former which is water soluble or water dispersible, a conductive amount of conductive agent, and an amount of organic, water insoluble and film former insoluble, thermoplastic non film-forming plastic particles having a particle size in the range of from about 0.01 - 20 microns sufficient to enhance the conductivity of the conductive agent; and drying the coated paper substrate, the film having a moisture content equivalent to that obtained by conditioning the film to a humidity of about 50%
or higher.

2. The process as defined in claim 1 wherein the paper substrate prior to the coating process of claim 1 has been pre-coated with a conventional precoat and dried, said precoat comprising filler and binder.

3. A process as defined in claim 2 wherein the precoat includes from about 10% to 20% of the total filler content of organic, water insoluble film-former insoluble, thermoplastic non film-forming plastic particles having a particle size in the range of from about 0.01 to 20 microns.

4. A process as defined in claim 3 wherein the dried and coated paper substrate is overcoated with a solvent containing composition to partially coalesce the plastic particles.

5. A process as defined in claim 4 wherein the solvent con-taining composition is a zinc oxide slurry for rendering the surface photoconductive.

6. The process according to claim 1 wherein said plastic particles are present in an amount of about 20-40%, based on the total weight, dry basis.

7. A process according to claim 1, 2 or 3, wherein the con-ductive agent is a polystyrene sulfonate, a sulfonated styrene maleic anhydride or a hydroxyalkyl-trialkyl ammonium salt.

8. A process according to claim 4, 5 or 6, wherein the con-ductive agent is a polystyrene sulfonate, a sulfonated styrene maleic anhydride or a hydroxyalkyl-trialkyl ammonium salt.

9. A process according to claim 1, 2 or 3, wherein the plastic particles are of polystyrene.

10. A process according to claim 4, 5 or 6, wherein the plastic particles are of polystyrene.

11. A process according to claim 1, 2 or 3, wherein the film former is a copolymer of at least 60% ethylenically unsaturated polymerizable monomer having non-polar functionality and about 3% to about 40% of a polymerizable olefinically unsaturated monomer having polar functionality.

12. A process according to claim 4, 5 or 6, wherein the film former is a copolymer of at least 60% ethylenically unsaturated polymerizable monomer having non-polar functionality and about 3% to about 40% of a polymerizable olefinically unsaturated monomer having polar functionality.

13. A water resistant coated conductive paper made by the process of claim 1, 2 or 3.

14. A water resistant coated conductive paper made by the process of claim 4 or 5.