Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2000-11-06
2002-06-25
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031620, C106S272000, C106S245000
Reexamination Certificate
active
06409811
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to anti-abrasion additives for inks. Such additives are chemicals mixed or dispersed into ink formulations in order to impart strength and anti-rub properties to such inks after printing. These additives are also called anti-mar, anti-rub, or anti-slip ink additives. Print on paper using inks containing these additives, for example, is protected against abrasion while maintaining slip properties when the ink, and the paper or other material, is subjected to a variety of smearing, smudging, and marring forces. Such forces occur during use, shipping, or handling of the paper.
The anti-abrasion additives of the present invention are most useful for heat-set, sheet-fed, and UV-coatable printing inks.
BACKGROUND OF THE INVENTION
Inks, particularly printing inks, must be provided with “strength” properties so that, after printing on paper or other substrates, the printing ink will not ruboff when the substrate surface is subjected to the normal abrasive forces encountered in use and handling. The printing ink, as modified by the ink manufacturer with anti-abrasion specialty chemicals, possesses improved mar resistance. Marring or “abrasion” of print detracts from the readability. Treated ink, after addition of these special additives, often also will have improved slip properties. Slip properties permit other printed pages to glide easily over the ink on a printed page without causing the ink to smudge.
In order to obtain these improved properties, anti-abrasion additives are added to printing ink formulations during manufacture by being mixed or ground into the ink formulation with pigments; added as a part of the final ink blend; or introduced at other times. Such additives are, for example, often dispersed into the precursor ink solvents or resins.
Commercial ink additives are often made in solid or powder form often as hard waxes. Harder waxes have proved difficult to mix satisfactorily or disperse into ink systems as additives. It has often been necessary to melt the wax additive as part of making the final printing ink. It ha s been found that anti-abrasion or rub qualities imparted by common commercial waxes are highly influenced by the melting temperature of a particular wax. Many waxes add ed to inks often result in only a small reduction in rub-off, not its complete elimination. The heat and movement imparted by the friction of constant rubbing in practice sometimes results in particles of the ink printed film continuing to spread to unprinted areas.
Progress does not always have no downside. Anti-abrasion hard waxes introduced into inks to solve the rub-off problem have caused other problems. Often, the more wax additive that is added to improve rub resistance, the more significant the decrease in desirable gloss of the printed ink, which is particularly unsatisfactory for quality magazines or prints. It is important to a publisher to minimize this reduction in gloss of printed ink. Accordingly, in most applications a compromise has to be achieved between the desired level of anti-rub properties and the a mount of gloss reduction.
An additive which requires heating, as do most hard wax anti-abrasion additive products, also presents additional manufacturing costs and handling problems. Since many anti-abrasion waxes are either solids or in powder form, they are often difficult to disperse into formulations, which are essentially liquid systems. In addition, there is the factor of increased cost associated with an ink containing relatively expensive anti-mar additives—reading a newspaper can be an experience requiring at a minimum a washing of ones hands. In the case of newspaper and certain magazine news inks, cost is an important factor and, therefore, many news inks do not ordinarily utilize anti-abrasion additives. Inexpensive magazine inks use only limited varieties and small amounts of additives.
Polyethylene waxes have been used as anti-abrasion additives in the ink industry. These waxes are normally incorporated by the ink manufacturer as dispersions of the wax in resins, generally of the same type as the ink formulations into which they are to be incorporated.
Anti-abrasion additives containing certain types of polytetrafluoroethylene (PTFE) are often the choice for heat-set inks, where the temperature of the drying apparatus does not cause them to significantly soften or melt. Particular kinds of polytetrafluoroethylene-based powders combined with organic chemicals have also been added directly to in-process inks using shear forces.
The incorporation of many commercial anti-abrasion additives presents similar conventional handling problems as are encountered with the dispersion of other types of solid or nearly-solid materials. When added to ink systems, these types of additive can agglomerate into clumps. When dispersed directly, uneven “wetting out” of the product has been reported resulting in the formation of lumps or globules whose core remains hard. Such agglomeration can be reduced in many cases by adding the additive to the system slowly with agitation. Slow dissolution, however, often influences the efficiency of specific ink manufacturing operations. Some chemicals have proved difficult to incorporate in industrial ink-making processes because they require long periods of time to dissolve. Both in simple ink resin solutions and, more particularly, in ink formulations comprising other chemicals and ingredients, extended agitation and aging periods are necessary before correct viscosity and dispersion is attained.
Ink manufacturers have continually searched for simple, fast, and effective ways of mixing anti-abrasion additives into ink systems. Because of this continuing desire and investigation, some commercial products are today used by ink fabricators as pourable liquid concentrates. These additives, in liquid form for inks and other compositions, usually involve taking the additive sold by a anti-abrasion additive manufacturing company and preparing a pre-mix liquid mixture or blend of the anti-abrasion additive and the ink vehicle.
Anti-rub PTFE-containing additives commercially available on the market include Protech 120, sold by Carroll Scientific, Inc. which is described as an 83% active compound containing a form of DuPont virgin Teflon®, which is a tradename for PTFE, and a synthetic blend of chemicals, with a petroleum distillate vehicle. Lawter International, sells an anti-rub hard wax ink additive product, designated Lawter SA-1021, which comprises a phenolic resin, a type of polytetrafluoroethylene (PTFE), and a petroleum oil. Commercial anti-rub additives containing PTFE have also been sold in the past which have contained small amounts of polyalphaolefins. All these products are believed to contain PTFE in an amount of 35% or greater.
A number of prior art patents describe ink additives. U.S. Pat. No. 5,024,700 describes the use of triethanolamine as an ink additive, which among other properties, is described as providing improved rub resistance to oil and resin-based ink compositions.
U.S. Pat. No. 5,158,606 describes a printing ink composition with a high degree of rub-off resistance comprising a dispersion of a pigment in a vehicle containing a C
7
-C
40
oil and a polymer latex emulsified in the dispersion. The patent further discloses that, where cost is not of paramount concern, a PTFE wax with petrolatum can be added to the oil/polymer latex ink composition.
U.S. Pat. No. 3,843,570 describes a porous material comprising PTFE obtained by polymerizing a monomer capable of forming a resin and discloses that the material is suitable with inks.
U.S. Pat. No. 5,591,796 discloses a pumpable anti-abrasion/slip additive comprising a mixture of about 40-70 wt. % polytetrafluoroethylene and polyalphaolefin. U.S. Pat. No. 5,749,949 discloses an anti-abrasion/slip additive comprising a mixture of about up to 60 wt. % polytetrafluoroethylene and about 25-45 wt. % pharmaceutical grade petrolatum. U.S. Pat. Nos. 5,591,796 and 5,749,949, owned by the assignee of the present invention, are incorpor
Gambino James
Tavares Bruce
Cronin Michael J.
Elementis Specialties, Inc.
Faison Veronica F.
Klemanski Helene
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