US3427258A - Electrostatic image developer powder composition - Google Patents

Description

United States Patent 3,427,258 ELECTROSTATIC IMAGE DEVELOPER POWDER COMPOSITION Ralph E. Trease, Toledo, Ohio, assignor to Owens- Iilinois, Inc., a corporation of Ohio No Drawing. Filed Nov. 12, 1965, Ser. No. 507,518 US. Cl. 252-500 7 Claims Int. Cl. H0111 1/04;H01c 1/00 ABSTRACT OF THE DISCLOSURE This invention relates to a novel, finely divided, encapsulated, decorative ink particle having an outer layer or coating of organic amine and an intimately dispersed core of dicarboxylic acid and organic resin, the ink particle having a resistivity of 10 to ohmcentimeters.

This invention pertains generally to the field of electrostatic printing. More particularly, the invention relates to novel compositions of matter and to a means for imparting electrical conductivity to the surface of a composition of matter.

Electrostatic printing has application for the printing and decorating of many surfaces, such as glass, ceramics, textiles, plastics, paper and paperboard type products and other articles of commerce. The electrostatic printing process, as generally employed for printing and decorat ing, consists in moving powder particles through imagedetining apertures of a screen or stencil to the printable or decorable surface. Of course, other conventional printing techniques like offset printing, wherein the imageforming powder is first transferred through an image screen to another surface, then by offset from this surface to the printable or decorable surface, may be used in the electrostatic printing art.

In arrangement of the general types immediately described, various problems can result from the powder particle. For example, if the resistivity of the particle is high, the powder may require precharging by corona techniques or by triboelectric means, in which cases the polarity of the electrical field must be oriented in accordance with the polarity of the charge on the particle. Also, a triboelectric charged particle may lead to undesirable effects, as the particle with its surface charge tends to agglomerate at the screen aperture and block said apertures. Moreover, it is diflicult to control particles with said surface charges as these particles, when in immediate contact with other particles or surfaces, tend to adhere elecotrostatically or by virtue of their triboelectrically acquired charges to htese surfaces or with themselves. This uncontrolled adherence may lead to inconsistent effects and often necessitates the need for cleaning the electrostatic printing apparatus.

It will be appreciated by those skilled in the art that if powder particles are compounded with reduced resistivity and with an electrically conductive layer on the surface of said particle, the tendency to avoid adherence would satisfactorily increase the usefulness of the powder particle. Likewise, it will be further appreciated by those versed in the art that particles possessing controllable movement would have a definite commercial value and would also represent a useful contribution to the art.

Accordingly, it is an object of the present invention to provide a means for modifying the high electrical resistivity of powder particles for use in the electrostatic printing art.

A further object of this invention is to provide a means for controlling the movement of particles by the formation of electrically conductive powder particles.

A still further object of this invention is to provide a means for reducing the electrical resistivity of resins.

3,427,258 Patented Feb. 11, 1969 Yet another object of this invention is to provide a novel composition of matter.

Another object of this invention is to provide a novel composition of matter comprising a resin, an organic acid and a polyamine.

Another object of the invention is to provide an electrically conductive layer on the surface of a resin.

Other objects and features of the invention will become apparent by reference to the following specification and claims.

In attaining the objects of this invention, it has now been surprisingly found that powder particles can be made with reduced resistivity by applying a surface layer of an amine type compound on the surface of the powder particle. The composition of matter is generally prepared by blending into an organic resin while in the molten or fiuid state an organic acid. If the acid is a liquid, as a dimer fatty acid, it may also function as a plasticizer to soften and lower the softening point of this resinous blend. To provide opacity or color, pigments may be dispersed in the resin blend.

Next, the molten or fluid blend is cooled to its solid state, entraining the organic acid in the solid resin. The solid mass is then processed, usually by pulverizing, to the desired shape and to the desired particle size. The surface of the resin-acid particle is then coated by treating said surface with a liquid amine type compound which is capable of chemically reacting with the entrained organic acid. The surface treatment of the particle will result in a chemical combining of the amine with that portion of the organic acid which is at the surface of the solid resin particle, to form a polyamine salt and/or a polyamide compound as a surface layer. This polyamine layer serves to encapsulate that portion of the organic acid which is not at the surface of the resin composition and which acid is not available to react with the added amine. The polyamine layer also serves as an electrically conductive layer on the surface of a nonconductive resin composition.

When the composite particle is ruptured by the application of energy, heat, pressure, etc., the surplus entrained acid becomes available to further react with the polyamine layer and to essentially effectively neutralize both its chemical and electrical characteristics.

The resins suitable for use in the instant invention are of the organic type. Exemplary of organic resins are the polyamide type resins. Polyamides are generally thought of as condensation products which contain recurring amide groups. These resins may be formed by means well known to the art, that is, by the condensation of diamines with diacids. As examples of polyamides may be mentioned ethylenediamine and sebacic acid, propylenediamine and sebacic acid, tetramethylenediamine and adipic acid, tetramethylenediamine and suberic acid, pentamethylenediamine and malonic acid, pentamethylenediamine and octadecanedioic acid, hexamethylenediamine and adipic acid, octamethylenediamine and sebacic acid, decamethylenediamine and oxalic acid and the like. The polyamide resins suitable for use in the present invention include the commercially available polyamide resins, for example, the polyamide resin Scope 3.0, which is the resinous derivative of diphenolic acid characterized by a softening point of 98 C. to 102 C., an acid value of 3.75 maximum, an amine value of 8.50 maximum, and a specific gravity of 0.99; the thermoplastic resins known commercially as Versalon, for example, Versalon 1112, as characterized by a softening point of 105 C. to C., a specific gravity of 0.955, and a tensile strength at 75 F. of 1900-2100 p.s.i.; Versalon 1175 as characterized by a softening point of C. to C., a tensile strength of l950-2400 at 75 F. and a specific gravity of 0.925- 0.975; and, the commercially available polyamide resins known as Polymid 1144 characterized by an acid value of 3.4, an amine value of 4.8, a melting point of 99 C. to 104 C., and a specific gravity of 0.99; the polyamide resin Polymid 1155 with an acid value of 5, an amine number of 5, a specific gravity of 0.98; the polyamide resin Polyamid 1060 with an acid value of 4.0, an amine value of l-2, a melting point of 112 C. to 113 C., and a specific gravity of 0.97; and the polyamide resin known commercially as Polymid 1074, characterized by an acid value of less than 6, an amine value of less than 6, a melting point of 102 C. to 108 C., and a specific gravity of 0.98. Other polyamide thermoplastic resins, such as Versamid 900 with an amine value of 4, a specific gravity of 0.98 and a softening point of ISO-190 C.; and Versamid 950 with an amine value of 4, a specific gravity of 0.98 and a softening point of 90100 C. may be used in the mode and manner of the invention. Generally, the polyamide resins used herein will have an acid value of about 3 to 5, an amine value of 1 to 8.5 and a specific gravity of about 0.92 to 0.99. The commercially available dimer acid sold under the trade name 'Empol may also be used for forming varied polyamide resins, by reacting the dimer acids with various amines. The dimer acids such as Empol 1018, Empol 1022 and Empol 1024 are aliphatic acids having two carboxyl groups and up to 36 carbon atoms.

Other resins which may be used for the purpose of the present invention include the commercially available polymers like polyvinyl chloride, polyvinylidene chloride, polyethylene, copolymer vinyl acetate with ethylene, copolymer vinyl acetate with vinyl benzoate, melamineformaldehyde resins, aldehyde resins, ketone resins, polypropylene and the like.

The pigments that may be used in the present particle are those pigments which are conventionally used in the art. Both white and colored pigments may be used, and the composition may include one or more pigments in the composition. As an example of pigments may be cited lithopone, titanium dioxide, zinc oxide, white lead, iron blues, chrome yellows and the like.

The amines used for coating the organoresin powder particle may be a diamine, a triamine, or a hetrocyclic diamine. The diamine may be characterized by the structure NH Y--NH wherein Y is an alkylene, an alkaryl or an aryl group. The alkylene group may be straight or branched chain, with the alkylene chain containing from about 1 to about 20 carbon atoms. The alkylene chain of l to carbon atoms is the now preferred alkylene radical. As examples of alkylene groups may be mentioned ethylene, propylene, tetramethylene, hexamethylene, decamethylene and the like. -As example of diamines may be mentioned ethylenediamine, propylenediamine, pentamethylenediamine, octamethylenediamine, hexamethylenediamine and the like. The alkaryl radical generally contains from '1 to carbon atoms and it may be exemplified by groups such as phenylethyl, propylphenyl, hexylphenyl, phenylnonyl, decylphenyl and the like. As examples of aryl and hetrocyclic diamines may be mentioned phenyl and piperazine. The triamines used for the purpose of the instant invention may be characterized by the general formula wherein X is an alkylene group. The alkylene group may be a straight or a branched chain alkylene group and the alkylene group for the two Xs may be the same or different. Generally, the alkylene group will contain from 1 to 10 carbon atoms, and may be exemplified by the above-mentioned groups. As examples of triamines may be mentioned diethylenetriamine, methylethyltriamine, dipropylenetriamine and the like.

The acids that are suitable for the blending with the organoresinous base particle generally include the dibasic organic acids containing two carboxyl radicals, and have the general formula COOH(CH COOH, wherein n is from 1 to 20. Examples of dicarboxylic acids are: malonic, succinic, glutaric, adipic, pimelic, suberic, aze laic, sebacic, brassic, brassylic and reccellic. Also, the commercially available dimers of fatty acids containing from 1 to 36 carbon atoms may be used in the mode and manner of the invention. The dimer acids are known commercially as Empol. The dimer acids are aliphatic acids containing two carboxyl groups and up to 36 carbon atoms. The amount of amine in the surface coating is essentially the chemical equivalent to the amount of acid in the internal resin particle.

The following examples are representative of the mode and manner of performing the invention and are not to be construed as limiting the invention.

EXAMPLE I A powder particle was prepared by intimately blending 5 grams of succinic acid into 25 grams of Scope 30 polyamide resin. The blend was heated to 250 F. to effectively melt the reagents into an intimate blend. The melt, after cooling to room temperature was ground in a Waring Blendor, to a fine powder. The powder had a resistivity of about 10 ohm-cm.

Next, the powder was surface coated with 2.5 grams of diethylenetriamine to coat the resin particle with a layer of the amine. The freshly prepared resin-acid particle with the amine layer had a resistivity of about 2 10 ohm-cm. After drying over night, the amine coated particle had a resistivity of about 4 10 ohm-cm. The coated particle was very active in the parallel plate test.

EXAMPLE II Following the procedure of Example I, 5 grams of diphenolic acid were mixed with 25 grams of Scope 30 resin, heated to about 250 F., cooled to room temperature and ground to a powder. The particle containing the diphenolic acid did not appear to possess any detectable measurable conductive activity.

The powder was then coated with 1 gram of diethylenetriamine to effect encapsulation of the resin base particle. The freshly coated particle exhibited resistivity of about 1X10 ohm-cm, while the dried particle exhibited resistivity of about 3 l0 ohm-cm. This particle was moderately active in a parallel plate test.

EXAMPLE III Following the procedures described above, a liquid dimer acid, Empol 1022 was mixed with grams of Versamid 900 and 30 grams of Empol 1022. The mix was heated to 280 F., cooled and pulverized as before, and the solid particles exhibited a resistivity of about 10 ohm-cm.

The particle was surface treated with 5 grams of diethylenetriamine and the measured resistivity of the particle was about 5X10 ohm-cm. The particle exhibited very good activity in a parallel plate test.

* EXAMPLE IV A composition containing a pigment in addition to the resin and the acid was prepared by mixing 67 grams of Scope 30, 133 grams of TiO and 30 grams of Empol 1022. The mix was melted, cooled, pulverized, dried and then surface treated with 5 grams of diethylenetriamine. The particle had a resistivity of 10 ohm-cm. and was very active in the parallel plate test. The powder with the amine coat was ground in a hammer mill and the resistivity of this powder was about 2X10 ohm-cm.

EXAMPLE V Following the procedure described immediately above, a composition of matter was prepared by melting together 30 grams of Scope 30, 60 grams of TiO; and 9 grams of Empol 1022. The resin base particle, coated with 2 grams of diethylenetriamine exhibited a resistivity of 9x10 ohm-cm. After pulverizing in a hammer mill, the measured resistivity was about 1.8 ohm-cm.

EXAMPLE VI A composition prepared from 60 grams of ethylenediamine and grams of succinic acid formed, after heating, a friable salt which appeared to be unsatisfactory as a resin binder. If 280 grams of diphenolic acid were used in place of the succinic acid, a resinous mass was formed, but its resistivity was about 10 ohm-cm.

The electrical properties of the powders are conveniently referred to in terms of its electrical resistivity. In the particular examples, the desired resistivity of the powder was between 10 and 10 ohm-centimeters, as measured by a standard cylindrical cell technique. In measuring resistivity by the standard cylindrical cell technique, the powder to be measured is poured into a cylindrical container of electrical insulating material to form an unpacked cylindrical body of known cross-sectional area and axial length. The unpacked powder is then compressed by reducing its axial length by a known amount and the electrical resistance of the packed cylindrical powder body is then measured by applying an electrical potential across its axial length. These measurements were made by means of a Keithly Electrometer model 610A.

The parallel plate test consists essentially of two parallel conductive surfaces generally separated by about a one-fourth inch air gap. A potential is applied across the plates forming an electrical field. When a powder is placed in this field, the powder is attracted to the plate possessing the opposite polarity. At this latter plate the charge of the particle is reversed and the particle then moves toward the original plate. This parallel plate test indicates activity in an electrical field.

Powder resistivities of between 10 and 10 ohmcentimeters, as measured by the above technique are satisfactory for the purpose of this invention. Powders having a higher resistivity may require precharging by corona technique or triboelectrification technique. The present invention, by controlling the particle formation and its electrical properties, aid in controlling the particle movement and tends to reduce the undesirable and inconsistent effects mentioned above.

While the illustrative embodiments of the invention have been described with particularity, it will be understood that various modifications will be apparent and can readily be made by those skilled in the art without departing from the scope and spirit of the invention.

I claim:

1. As a composition of matter, a decorative ink powder consisting of finely divided particles, each particle having an intimately dispersed core of dicarboxylic acid and synthetic organic resin and an :amine coating on the surface of the core which is chemically reactive with the acid, the amount of said amine coating being in excess of the stoichiometric amount required to react with that portion of the acid which is at the surface of the core.

2. The composition according to claim 1 wherein the dicarboxylic acid is of the general formula COOH(CH -CO OH clic diamines wherein Y and X are alkylene, aryl and alkaryl.

7. The composition of claim 1 wherein the ink powder has a resistivity of 10 to 10 ohm-centimeters.

References Cited UNITED STATES PATENTS 2,263,007 11/1941 McNally et al.

2,624,725 6/ 1953 Bjorksten et al 260-935 2,832,697 3/ 1958 Walles l1769 2,921,048 1/1960 Bell et al. 26045.9 2,979,403 3/ 1961 Giaimo 961 3,013,997 12/1961 Color et al. 26023 3,234,017 2/1966 Heyl et a1 252621.

LEON D. RODSOL, Primary Examiner.

J. D. WELSH, Assistant Examiner.

U.S. Cl. X.R.