Electroscopic printing powder

Claim 2

A developer mix for use in electrostatic printing to develop latent images including charged and uncharged areas of an image-bearing sheet, said developer mix comprising the combination of a. separate granular magnetically attractable carrier particles, and b. a developer powder comprising

Claim 3

a resin blend having a triboelectric relationship of opposite polarity with respect to said magnetically attractable granules and having a sharp melting point within the range of about 70*C. to about 165*C., said resin blend being formed by mixing the resin components in their molten state and being composed of i. a major portion of an infrangible thermoplastic polyamide resin formed by reacting a high molecular weight polyene fatty acid or esters thereof with an amine, and ii. a minor portion of a highly frangible thermo-plastic resin having a fracturing value not greater than 200 gram centimeters, the frangibility of the resins being measured by the falling ball method on a wafer of resin maintained at 100* F. and 3.75 centimeters in diameter and 0.5 centimeters in thickness, whereby developed images of substantially improved density can be formed over extended operating periods.

Claim 4

A developer mix as defined by claim 2 wherein the frangible resin is a maleic anhydride rosin-modified resin.

Claim 5

An electroscopic powder suitable for developing electrostatic charge images, said powder consisting essentially of frangible and infrangible thermoplastic resins combined when in their molten state to form a miscible mixture, said mixture having physical properties which are distinct from either of the components comprising said mixture, and having a melting range not greater than 8* F., a softening point not less than 130* F. and a melting point below the char point of paper to which it is applied, said frangible resin constituting 10 to 91 percent by weight of the electroscopic powder and having a fracturing value not greater than 200 grams centimeters, and said infrangible resin being a polyamide resin formed by reacting a high molecular weight polyene fatty acid or esters thereof with an amine and constituting 5 to 90 percent by weight of the electroscopic powder and having a fracturing value of at least 1000 gram centimeters, the fracturing value of the resins being measured at 100* F. by the falling ball method on a wafer of resin 3.75 centimeters in diameter and 0.5 centimeters in thickness.

Claim 6

The electroscopic powder of claim 4 wherein said powder has a melting point in the range of from 215* to 235* F.

Claim 7

The electroscopic powder of claim 4 wherein said powder is comprised of from 10 to 50 percent by weight of said polyamide resin and 50 to 90 percent by weight of a maleic anhydride rosin-modified resin.

Claim 8

The electroscopic powder of claim 4 wherein said powder is comprised of from 30 to 40 percent polyamide and 40 to 50 percent maleic anhydride rosin-modified resin and from 1 to 10 percent polyhydric alcohol fluxing agents.

Claim 9

The electroscopic powder of claim 4 wherein said powder is comprised of from 50 to 90 percent of said thermoplastic infrangible polyamide resin and from 5 to 40 percent of a frangible thermoplastic resin component selected from the group consisting of maleic anhydride rosin-modified resin, esterified diphenolic resin, and phenol-formaldehyde resins.

Claim 10

The electroscopic powder of claim 4 wherein said powder has a particle size range of from 1 micron to 74 microns with an average particle size of from 4 microns to 10 microns.

Claim 11

A developer mix for use with magnetic brush-type developing apparatus for rendering latent electrostatic charge images visible on electrostatic recording members by applying thereto an electroscopic powder, and subsequently fixing the adhered powder thereto, said developer mix comprising a granular electroscopic powder of colored thermoplastic particles mixed with larger magnetically attractable carrier particles each having a charge of opposite polarity, said thermoplastic powder having as one component a polyamide resin formed by reacting a high molecular weight polyene fatty acid or esters thereof with an amine heat blended with a second frangible resin component to form a composite electroscopic powder having a fracturing value of at least 400 gram centimeters and said polyamide resin having a fracturing value of at least 1000 gram centimeters.

Claim 12

The developer mix as claimed in claim 10 wherein said polyamide resin is present in an amount of from 50 to 90 percent by weight of said powder.

Claim 13

A developer mix as claimed in claim 10 wherein the second component is maleic-anhydride-polyhydricalcohol rosin-modified resin in an amount of from 9 to 50 percent by weight of the electroscopic powder.

Claim 14

The developer mix as claimed in claim 11 wherein the polyamide resin is a reaction product of polymerized linoleic acid and ethylenediamine.

Claim 15

The developer mix as claimed in claim 10 wherein the electroscopic powder has an average particle size in the range of from 4 microns to 10 microns.

Claim 16

An improved electrostatic developer mix including carrier particles and colored toner particles, wherein the improvement comprises said toner particles being a hot melt blend of an infrangible thermoplastic resin and a frangible thermoplastic resin wherein physical properties of the resulting blend are distinct from the properties of either of the separate components, said infrangible resin material being a polyamide resin formed by reacting a high molecular weight polyene fatty acid or esters thereof with an amine said polyamide resin having a fracturing value of at least 1000 gram centimeters and said frangible material having a fracturing value less than 200 gram centimeters and the fracturing of the blend being at least 400 gram centimeters.