Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-03-21
2003-07-08
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C528S480000, C528S482000, C528S490000
Reexamination Certificate
active
06590023
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to methods for treating components of coatings for paper for ink jet printing applications and in particular, to the manufacture of coatings of the type used to enhance ink drying and produce higher quality printed images so that the coatings contain reduced amounts of undesirable substances.
BACKGROUND OF THE INVENTION
Ink jet printing methods utilize printheads having orifices which eject ink droplets onto a print medium. For higher quality, higher resolution printing applications, the orifices of the printheads have been increased in number and their diameter significantly reduced in size. Accordingly, for full color printed images, inks are formulated to include dyes and/or pigments and various carriers and/or solvents which are resistant to drying or otherwise clogging the nozzle holes of the printhead. Such ink formulations, however often adversely affect the properties of the ink deposited on the print medium resulting in longer drying times and/or color mixing or bleeding of the images resulting in poorer quality images.
Various print media may be used for ink jet printing applications depending on the ink formulations. Such media include cellulosic webs, synthetic papers, polymeric films and the like. As advances in ink jet printing have occurred, specialty papers containing exotic coatings have been developed. Such specialty papers are often more expensive than uncoated papers and may contain coatings which are not compatible with the wide variety of ink formulations being used or developed for ink jet printing applications.
Despite the abundance of specialty webs for ink jet printing, cellulosic webs remain the most widely used print media. Cellulosic webs are made by conventional paper making techniques wherein a fibrous pulp is deposited on a wire screen and dried to form a web. Accordingly, the webs contain minute pores or voids between the cellulosic fibers for absorption of liquids therein. The porosity of the webs may be changed by use of additives such as clays and the like which may change the hydrophilic properties of the webs so that the webs absorb or repel aqueous and/or organic fluids which may be used as carrier fluids in ink formulations.
Ideally, it is desirable for only the carrier fluid of the ink formulation to penetrate into the web thereby depositing colorant on the outer surface of the web. Balancing the properties of the ink formulations so that the formulations are adaptable for use with a wide variety of print media is extremely difficult. It is even more difficult to provide ink formulations which may be used on uncoated or plain paper webs. Print medium adaptable to accept improved dye and/or pigment based ink formulations has been achieved by coating the medium, generally paper, with coatings based on an aqueous polymer of epichlorohydrin and dimethylamine, preferably just prior to printing. However, it has been discovered that paper coated in this manner can contain undesirable substances and have an unpleasant odor. Accordingly a need exists for a manner of treating coating formulations of this type to remove undesirable substances and reduce undesirable odor characteristics.
SUMMARY OF THE INVENTION
With regard to the above and other objects and advantages thereof, the invention relates to a method for reducing the amount of undesirable components in a polyamine coating formulation to provide a coating formulation having a substantially undetectable odor and less than about 1 ppm chlorinated compounds.
In a preferred embodiment, the method includes the steps of:
(a) adjusting the pH of one or more components of the coating formulation having the undesirable substances to a pH in the range of from about 8.0 to about 9.0.
(b) contacting each pH adjusted component with an activated carbon material, the activated carbon material being present in an amount of from about 0.5 to about 2.0% (wt/wt).
filtering each treated component and combining same with other components to yield a treated coating formulation having a substantially undetectable odor and less than about 1 ppm chlorinated compounds.
In another aspect, the invention provides a method of treating a coating formulation prior to its introduction onto a web to be printed by an ink jet printer.
In a preferred embodiment, the method includes the steps of:
a) determining the nature and amount of undesirable substances in a polyamine component of the coating formulation,
b) adjusting the pH of the component,
c) contacting the pH adjusted component with a first activated carbon material,
d) filtering the thus treated component,
e) contacting the thus treated component with a second activated carbon material, and
f) filtering the thus treated component and combining it with other components of the coating formulation to yield a treated coating formulation having a reduced amount of the undesirable substances.
The components of the coating formulations preferably treated in accordance with the invention are aqueous polymers of epichlorohydrin and dimethylamine to control ink permanence on the printed web. Such components, if untreated, typically exhibit undesirable odor characteristics and contain undesirable substances including chlorinated hydrocarbons.
The invention advantageously enables substantial removal of the unpleasant odor characteristics and the undesirable substances.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention relates to methods for treating formulations of the type which are coated onto cellulosic webs, preferably immediately prior to printing, in order to promote ink drying and color fastness and reduce ink smearing and/or bleeding. Treatment of the formulations in accordance with the invention removes undesirable substances from the formulations and/or reduces undesirable characteristics such as unpleasant odor. Formulations particularly suited for treatment in accordance with the invention are coating formulations provided by an aqueous polymer of epichlorohydrin and dimethylamine.
In this regard, it is noted that the treatment is directed to treating the aqueous polymer component of a coating formulation prior to combining it with other components of the coating formulation. However, as treating the aqueous polymer component affects characteristics of the coating formulation, treatment of the aqueous polymer component is sometimes referred to herein as treatment of the coating formulation. Thus, quantities referred to herein, e.g., % (wt/wt), refer to relative amounts with regard to the aqueous polymer component.
For the purpose of example, preferred coating compositions which have been observed to be particularly suitable for treatment in accordance with the invention are described herein. As will be shown, these compositions may be treated in accordance with the invention to remove undesirable substances and undesirable characteristics, such as unpleasant odor.
PREFERRED COATING FORMULATIONS
For the purpose of example only, it is noted that preferred formulations for treatment in accordance with the invention may include a polyhydric alcohol selected from the group consisting of glycol-based solvents having a surface tension ranging from about 25 to below about 45 dynes/cm, such as 1,2-propanediol, dipropylene glycol, tripropylene glycol, and the like as well as mixtures of such solvents having desired surface tension properties.
It has been observed that the method of the invention is particularly suitable for treating such formulations having the glycol-based solvent present in the coating formulation in an amount of from about 25 to about 96 percent by weight of the formulation, preferably from about 25 to about 75 percent by weight and most preferably from about 25 to about 60 percent by weight of the formulation. For example, 100 percent by weight 1,2-propanediol and a mixture containing from about 75 to about 100 percent by weight 1,2-propanediol and from about 0 to about 25 percent by weight dipropylene glycol.
Such exemplary coating formulations may also include a polyvalent metal salt, preferabl
Brady John A.
Cain Edward J.
LaRose David E.
Lexmark International Inc.
Wyrozebski Lee Katarzyna I
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