Electrophotographic-recording Member And Process Of Producing The Same

Abstract

Polyepihalohydrin is quaternized with a trialkyl amine to produce an electroconductive polymer. The quaternized polyepihalohydrin is applied to paper to produce a recording element having an electroconductive surface adapted for electrographic printing.

Description

In the manufacture of paper having a printing surface adapted for electrographic printing, it previously has been found difficult to provide the paper with a coating of an electroconductive substance that is dispersible in water and has the necessary electroconductive properties. One group of compounds which has been found to be useful comprises a polymer consisting of a polymerized vinyl-benzyl quaternary ammonium compound, disclosed in U.S. Pat. No. 3,011,918 to Silvernail et al. However, paper coated with these compounds suffers from an objectionably strong aminelike odor which can only be reduced by lowering the pH of the coating to a very acid range in which corrosion of the coating apparatus is promoted. Further, these compounds are expensive and a more economical, as well as satisfactory, electroconductive polymer has been sought.

It would be a great advantage to the art if a water-dispersible polymer was found that had electroconductive properties and no significant disadvantages. It would also be an advantage to the art if a relatively simple method of imparting electroconductivity to a substrate could be devised.

OBJECTS

It is an object of this invention to produce an electroconductive polymer.

It is a further object of this invention to produce a polymer that is water soluble or water dispersible that can be used to produce a recording element having the electroconductive surface adapted for electrographic printing. Another object is to produce a paper having a surface adapted for electrographic printing.

Still another object of this invention is to devise a method of producing an electrographic recording member.

Further objects will be evident to those skilled in the art.

THE INVENTION

The invention relates to the manufacture of substrates having electroconductive properties useful when the substrate is employed as a recording element in an electrographic printing process. More particularly, this invention relates to paper having the electroconductive surface adapted for electrographic printing and containing a polymer comprised of quaternized polyepihalohydrin and preferably quaternized polyepichlorohydrin.

It has been discovered in accordance with the present invention that polymers of quaternized polyepihalohydrin can be prepared economically and can readily be applied as a coating to paper to produce a product having an electroconductive surface and possessing electroconductive properties over a wide relative humidity range. Paper coated with quaternized polyepihalohydrin, in accordance with the present invention, has a surface resistivity ranging from about 5.times.10.sup.8 to 1.times.10.sup.5 ohms per square centimeter over a relative humidity range of from about 8 to 75 percent.

THE POLYMERS

The electroconductive water-dispersible polymer has the formula: ##SPC1##

where X is a halogen selected from the group consisting of chlorine, bromine, and iodine, R is independently selected from the group consisting of methyl, ethyl and (C.sub.n H.sub.2n O).sub.y H, where y is an integer from 1 to 30, n is an integer from 1 to 4, and m is an integer from 5 to 2,000. Preferably, X is chlorine, R is methyl, and m is an integer from 20 to 100. This polymer can be easily prepared from the substantially complete quaternization of a trialkyl amine or a trioxyalkyl amine and polyepihalohydrin. Preferably, the polyepihalohydrin is polyepichlorohydrin and this is quaternized with trimethyl amine. Preferably the polymer is substantially completely quaternized, meaning the the polymer contains from 80 to 100 percent quaternary adducts having the formula: ##SPC2##

where X is a halogen selected from the group consisting of chlorine, bromine, and iodine, R is independently selected from the group consisting of methyl, ethyl, and (C.sub.n H.sub.2n O).sub.y H, where y is an integer from 1 to 30, n is an integer from 1 to 4, and m is an integer from 5 to 2,000. Partially quaternized polyhalohydrins have been tested and found that when the amount of quaternization is below 70 percent the paper lacks the necessary electroconductive activity. Therefore, as stated, the polymers should be from 80 to 100 percent quaternized and more preferably from 90 to 100 percent quaternized.

To produce the quaternary polyepichlorohydrin of the desired molecular weight, namely those having a molecular weight of from about 750 to 300,000, and preferably from 2,000 to 150,000, it is necessary to choose an appropriate molecular weight of the polyepihalohydrin. Polyepihalohydrins having molecular weights ranging from 450 to 180,000 have been tested and found to produce continuous films of coatings containing these polymers to paper without any operational difficulties. Preferably, the epihalohydrin has a molecular weight ranging from about 1,200 to 100,000.

The amine is preferably trimethyl or triethyl amine. But other amines could be used, such as methyl diethyl amine, ethoxy dimethyl amine, as well as mixtures of amines. The alkyl groups are independently selected from methyl, ethyl, and (C.sub.n H.sub.2n O).sub.y H, where y is an integer from 1 to 30, n is an integer from 1 to 4, and m is an integer from 5 to 2,000.

THE METHOD

The method of preparing the electrographic recording member of this invention comprises the following steps.

1. Coating a substrate, preferably paper, with a dispersion containing from 5 to 50 percent of a water-dispersible polymer having the formula ##SPC3##

where X is a halogen selected from the group consisting of chlorine, bromine, and iodine, R is independently selected from the group consisting of methyl, ethyl, and (C.sub.n H.sub.2n O).sub.y H, where y is an integer from 1 to 30, n is an integer from 1 to 4, and m is an integer from 5 to 2,000, so as to form a continuous coating in an amount corresponding to from 0.5 to 2.5 pounds per 3,000 square feet of the paper. The term dispersion includes solution, if the polymer is completely or partially water soluble.

2. Drying the coating of the water-dispersible polymer.

3. Applying a layer of an extender selected from the group consisting of starch, polyvinyl alcohol, polybutyl acetate, and polybutyl styrene.

4. Recoating with an electrographic photoconductive compound selected from the group consisting of the oxides, iodides, selenides, sulfides, and tellurides of zinc, antimony, aluminum, bismuth, cadmium, mercury, molybdenum and lead; selenium; arsenic trisulfide; lead chromate; and cadmium arsenide to form a final electrophotographic recording member.

To accomplish the above steps of preparing a substrate having an electroconductive surface coating, the electroconductive polymers of this invention can be applied as a continuous film to paper by coating, spraying dipping, brushing or by any other suitable application. The quaternized polymer is preferably applied to paper, as a coating, in the form of an aqueous dispersion or solution. The coated paper is then dried to produce a product having an electroconductive surface. Suitable or standard coating devices such as a blade coater, have been used and the coated paper has been dried by the use of radiant energy from heat lamps. The coating can be applied to paper at a range of from 0.5 to 2.5 pounds pickup per 3,000 square feet of paper. Other components can be formulated with this polymer such as clay, starch, pigments, etc.

For the substrate, paper is preferred, including high wet-strength paper coated or uncoated, having a thickness of from 3 to 6 mils. Other electrically conductive or semiconductive materials may be used, such, for example, as plastic films including cellophane, cloth, and metallic foils, e.g., aluminum and copper foils.

Preferably, the water-dispersible quaternized polyepihalohydrin is polyepichlorohydrin quaternized with trimethyl amine. The extender is preferably polyvinyl alcohol but could be any extender well known in the art. In certain conditions the extender could be eliminated. Preferably, the electrophotographic photoconductor is zinc oxide, which is a well-known extender.

Other particularly suitable photoconductors for use in the present process are inorganic products such as, for example, the oxides of antimony, aluminum, bismuth, cadmium, mercury, molybdenum and lead. As mentioned, preferred use is made of zinc oxide. When high-grade layers are to be manufactured, the zinc oxide to be used should be as pure as possible and advantageously is a product prepared by the so called French method, that is to say by atmospheric oxidation of zinc vapor. In any case the photoconductor should be finely divided and preferably have a particle size below 1 micron.

Other polymers may be mixed with the quaternized polyepihalohydrin before application of the coating to a paper substrate. A polymer, such as starch, may be used as a component of the coating formulation to prevent strike through of the electroconductive polymer by keeping the latter on the surface of the paper. While the use of a polymer such as starch adds very little to the electroconductive properties of the coated paper, it may be used for the above-indicated purpose. The starch-quaternized polyepihalohydrin coating may contain any proportion of starch up to about a ratio of about 1:1, starch to electroconductive polymer.

The electroconductive water-dispersible polymers are easily prepared. The following examples illustrate the preparation of the polymers.

EXAMPLE I

Thirty-eight hundred parts of epichlorohydrin is charged to a glass-lined reactor, agitated and sampled for water analysis. If the water content is too high (above 0.2 percent) a portion of the epichlorohydrin is distilled off, and the charge is maintained by the addition of fresh epichlorohydrin. After the water content is low enough, (below 0.2 percent) the vessel is shut in and cooled at 60.degree. C. under a nitrogen pressure of 3-5 p.s.i. A nitrogen blanket is maintained during the catalyst addition with the kettle open to the atmosphere through the condenser.

Approximately 160 pounds of 25 percent triisobutyl aluminum in toluene is added slowly under close supervision at 60.degree.-70.degree. C. until an exothermic reaction is noted. The temperature is allowed to rise controllably to 100.degree. C. with cooling as required. When the initial reaction subsides, the temperature is maintained at 100.degree.-110.degree. C. by catalyst additions until no more exothermic reaction is noted. The temperature is lowered to 80.degree.-85.degree. C.

Twenty-five gallons (208 pounds) of water are added below 85.degree. C. The batch is stripped at 22 inches vacuum (minimum) to a temperature of 100.degree.-110.degree. C. to remove 1-2 drums of condensate.

Calculate the total weight of reactor contents from materials added and removed. The charge in weight percent for the following step is as follows:

26.2 percent Reactor contents

73.8 percent 25 percent aqueous trimethylamine.

Add the trimethylamine below 80.degree. C. The kettle is vented briefly to bring it to atmospheric pressure.

The kettle is then closed from the atmosphere and heated to 100 p.s.i.g. which should be approximately 90.degree.-100.degree. C. Hold for 16 hours. Increase the temperature slowly keeping at 100 p.s.i.g. and hold at 130.degree.-140.degree. C. for 2 hours.

Cool to 70.degree.-80.degree. C. and neutralize to pH 5.5 to 6.5 with 250-500 pounds of 30 percent aqueous hydrochloric acid.

EXAMPLE II

Seven hundred fifty parts by weight epichlorohydrin (containing 0.64 part water) was placed in a reactor equipped with agitation and cooling under a nitrogen blanket. A solution of 25 percent triisobutyl aluminum in toluene was added in increments at 60.degree. C. until evidence of exothermic reaction appeared. Twenty-eight parts was required to initiate the reaction.

The heat of reaction increased the temperature of the reaction mixture to 115.degree. C. in 20 minutes. Temperature was maintained at 100.degree. C. to 115.degree. C. for 11/2 hours with cooling. During this time an increase in the apparent viscosity of the reaction mixture occurred. After the reaction subsided to the extent that cooling was no longer required, incremental catalyst addition was resumed at 75.degree. to 100.degree. C. and 12 parts was added during a 3 -hour period with the temperature maintained by the heat of the reaction. The temperature was maintained at 90.degree. to 100.degree. C. for additional 11/2 hours.

At the end of this period, 25 parts water was added to destroy residual catalyst, and the temperature was increased to 150.degree. C. over a 11/2 hour period to remove 106 parts condensate.

The residue was a pale amber viscous liquid which was soluble in toluene and xylene and insoluble in isopropyl alcohol.

EXAMPLE III

One hundred thirty-eight parts by weight of the product of Example II was placed in a pressure vessel equipped with agitation and heating along with 130 parts of a 3 -mole ethylene oxide adduct of dimethylamine and 182 parts of 25 percent solution of trimethylamine in water and heated at 100.degree. C. for 17 hours, during which time the pressure fell from 47 p.s.i.g. to a slight vacuum in the reactor. The reaction mixture was neutralized to a pH of 5.1 with 23 parts of 30 percent hydrochloric acid.

A clear brown viscous liquid was obtained which was very soluble in water.

EXAMPLE IV

Ninety-three parts by weight of the product of Example II was heater to 140.degree. C. with agitation and 177 parts of a 3 -mole ethylene oxide adduct of dimethylamine added in portions over a 1 -hour period. The reaction mass was cooled to 110.degree. C. and 50 parts water added. Heating was applied and the reaction mass held at reflux (112-116.degree. C.) for 5 hours, at which time 50 parts water was added and the mixture neutralized to a pH of approximately 6 with 35 parts 30 percent hydrochloric acid.

EXAMPLE V

One hundred seventy-six parts by weight of the product of Example II was heated at 150.degree. C. with agitation and 251 parts of a 5 -mole ethylene oxide adduct of dimethylamine was added over a 1 hour period. The temperature was held at 128.degree. C. for 4 hours, after which 100 parts water was added and the reaction mixture neutralized to a pH of about 6 with 29 parts 30 percent hydrochloric acid.

EXAMPLE VI

One hundred twenty-one parts by weight of the product of Example I was heated with 520 parts of 25 percent trimethylamine in water in a pressure vessel with agitation for 16 hours at 100.degree. C. Five hundred forty-nine parts of this product was neutralized to a pH of about 6 with 24 parts 30 percent hydrochloric acid.

EXAMPLE VII

Forty-two parts by weight of the product of Example II was heated with 81 parts of 7 -mole ethylene oxide adduct of dimethylamine and 59 parts 25 percent aqueous trimethylamine in a pressure vessel with agitation for 16 hours at 100.degree. C. Five hundred fifteen parts of this product was neutralized to a pH of about 6 with 51 parts 30 percent hydrochloric acid.

EXAMPLE VIII

Seventy parts by weight of the product of Example II was heated with agitation to 145.degree. C. and 199 parts of a 7-mole ethylene oxide adduct of dimethylamine was added over a 30 -minute period. The reaction mass was held at 130.degree. to 140.degree. C. for 4 hours and 50 parts water added. Heating was continued at reflux (112.degree. C.) for an additional 2 hours. Fifty parts water was added and the reaction mass neutralized to a pH of approximately 6 with 32 parts 30 percent hydrochloric acid.

EXAMPLES IX

Thirty-five parts by weight of the product of Example II was heated with 99 parts of an 11 -mole ethylene oxide adduct of dimethylamine and 46 parts 25 percent aqueous trimethylamine in a pressure vessel with agitation for 16 hours at 100.degree. C. Five hundred twenty-six parts of this product was neutralized to a pH of about 6 with 39 parts 30 percent hydrochloric acid.

Polyepibromohydrin and other amines may also be used to produce similar products.

ELECTROCONDUCTIVITY TEST

The coated substrate is tested for surface resistivity by a standard procedure substantially like that described in "Standard Methods of Test for Insulation Resistance of Electrical Insulation Materials," A.S.T.M. designation: D257-46.

In the practice for preparing a printed surface for an electrographic printing process the steps are followed as previously described in the method of preparing electrophotographic surfaces. A 40 percent solids concentration of the quaternized polymer of Example I in water was used. Five hundred volts potential was applied to a sheet of paper after conditioning at 20 percent relative humidity and 50 percent relative humidity for 36 hours. The results are listed in the following table. ##SPC4##

The papers used designated as No. 1 and No. 2 were standard papers used in the industry for electrophotography. For example, the paper weighs 80 grams per square meter and is made from a moderately beaten papermaking furnish of bleached chemical wood pulp, ground wood, and chemical clay filler and fiber, rosin size precipitated by aluminum sulfate.

This table shows that the paper has a much less surface resistivity and therefore a much greater conductance when the quaternized polymer is applied to the paper. Therefore, the polymer-coated paper met the standards of the industry for use in electrographic-printing processes.

Other quaternized polyepihalohydrins of the examples may be used and give good results as electroconductive polymers. Similarly, other substrates such as cellophane, cloth, and metallic foils could be used.

SUMMARY

From all of the above samples, it is apparent that polyepihalohydrins have molecular weights ranging from 450 to 180,000 can be quaternized to produce quaternized polyepihalohydrins which can be employed as coatings to impart electrical conductivity properties.

Various changes can be made in the illustrative examples specifically set forth above without departing from the spirit of our invention or the scope of the appended claims.

Claims

We claim:

1. A paper having a printing surface adapted for electrographic printing and containing on said surface a continuous coating in an amount corresponding to from 0.5 to 2.5 pounds per 3,000 square feet of the paper, of an electroconductive water-dispersible polymer having the formula: ##SPC5##

where claim: is a halogen selected from the group consisting of chlorine, bromine, and iodine, R is independently selected from the group consisting of methyl, ethyl and (C.sub.n H.sub.2n 0).sub.Y H where y is an integer from 1 to 30, n is an integer from 1 to 4, and m is an integer from 5 to 2,000

2. The paper of claim 1 in which X is chlorine, R is methyl and m is an integer from 20 to 100.

3. The paper of claim 1 in which the water-dispersible polymer comprises of from 80 to 100 percent quaternary adducts.

4. The paper of claim 3 in which the water-dispersible polymer comprises of from 80 to 100 percent quaternary adducts where X is chlorine, R is methyl and m is an integer of from 20 to 100.

5. A method of producing an electrophotographic-recording member which comprises the steps of:

A. coating a substrate with a dispersion containing from 5 to 50 percent by weight of a water-dispersible polymer having the formula: ##SPC6##

where X is a halogen selected from the group consisting of chlorine, bromine, and iodine, R is independently selected from the group consisting of methyl, ethyl and (C.sub.n H.sub.2n O).sub.y H, where y is an integer from 1 to 30, n is an integer from 1 to 4, and m is an integer from 5 to 2,000, so as to form a continuous coating in an amount corresponding to from 0.5 to 2.5 pounds per 3,000 square feet of the paper;

B. drying the coating of the water-dispersible polymer;

C. applying a layer of an extender selected from the group consisting of starch, polyvinyl alcohol, polybutyl acetate and polybutyl styrene; and

D. recoating with an electrophotographic photoconductor selected from the group consisting of the oxides, iodides, selenides, sulfides, and tellurides of zinc, antimony, aluminum, bismuth, cadmium, mercury, molybdenum and lead; selenium; arsenic trisulfide; lead chromate; and cadmium arsenide to form a final electrophotographic recording member.

6. The method of claim 5 in which the substrate is paper.

7. The method of claim 5 in which the extender is polyvinyl alcohol.

8. The method of claim 5 in which the photoconductor is zinc oxide.

9. The method of claim 5 in which X is chlorine, R is methyl and m is an integer of from 20 to 100.

10. The method of claim 5 in which the water-dispersible polymer is formed by the substantially complete quaternization of a trialkyl amine and polyepihalohydrin.

11. The method of claim 10 in which the water-dispersible polymer comprises of from 80 to 100 percent quaternary adducts.

12. The method of claim 11 in which the water-dispersible polymer comprises of from 80 to 100 percent quaternary adducts where X is chlorine, R is methyl and m is an integer of from 20 to 100.