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
1998-12-28
2002-06-18
Reddick, Judy M. (Department: 1713)
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...
C524S276000, C524S277000, C524S279000, C524S487000, C524S488000, C524S489000, C524S490000, C524S458000, C524S700000
Reexamination Certificate
active
06407160
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to a composite wax particle capable of dispersing in organic solvent media and providing a coated layer with superior physical characteristics.
BACKGROUND OF THE INVENTION
Waxes have widely been used in a surface coated layer to impart an article with improved barrier properties, antiblocking properties, rub and mar resistance, controlled releasing properties, slip and lubricity, and water repellency. For example, waxes have been used as a surface finish on candies, chocolate bars, chewing gums and similar products; as an additive in polishes on furniture, leather, floor, automobile and fruits, as pharmaceutical coating on pills, as a component in creams and lipsticks, as an additive in plastic film emulsions, carbon papers and inks, paints and varnishes, mold releases, metal casting, laminated cartons, water-proof compounds, and the like. To enhance the performance of the coated layer, for example, higher moisture impermeability and surface water repellency, superior surface lubricity and mar resistance, etc., it is highly desirable to include in the coated layer relatively high loadings or concentrations of wax. However, a high enough wax concentration to render the subsequent coating superior with physical characteristics results in coating compositions, especially non-aqueous coating compositions, which are highly unstable and very difficult to manufacture.
Aqueous wax dispersions of colloidal sizes (0.01 to 5 micron, typically in the range of from 0.01 to 1 micron) are generally known. Non-aqueous wax dispersions of colloidal sizes are difficult to prepare. Wax can be compounded into viscous non-aqueous media (viscosity greater than, for example, 1000 cps) by mechanical force. The problem with such an approach is that the particle size is difficult to predict and more difficult to reproduce. The resultant dispersions are not truly colloidal dispersions and on dilution wax particles will settle down or precipitate out.
Waxes are insoluble in most organic solvents, especially in polar organic solvents. Coatings can be made using highly toxic solvents such as propylene dichloride, which is on EPA P/U highly hazardous list.
It is well know in the art to incorporate wax in latex formulations. U.S. Pat. No. 4,569,896 teaches the production of a toner composition that includes resin particles of styrene methacrylate copolymer grafted or containing a low molecular weight wax plus a second resin composed of a terpolymer of styrene, acrylate and acrylonitrile. The developer also contains magnetite particles and carbon black. U.S. Pat. No. 5,034,454 describes the preparation of a crosslinkable water-dispersible acrylic copolymer wherein the polymerization is conducted in an organic solvent in the presence of a wax. The polymerization includes about 1 to 15 weight percent of a wax. U.S. Pat. No. 5,395,877 describes a process for the production of fortified vinyl latex rich in wax copolymerizing in an organic solvent in the presence of a wax under conditions to produce a low molecular weight resin. The copolymer is treated with ammonium hydroxide or aqueous alkali and used as a cosurfactant in a second aqueous emulsion polymerization of vinyl monomers to produce the fortified vinyl latex. U.S. Pat. No. 4,766,059 describes a method of making solid spherical beads having a mean size ranging from about 0.5 to about 20 microns. The polymer beads contain a polymeric resinous material and a water insoluble wax. The process of making such solid beads involves the use of water miscible or immiscible low boiling solvent to dissolve both polymeric materials and wax, and subsequently removal of the solvent or solvent mixture by evaporation. This requires large processing equipment and lengthy processing time, which increases the expenses. U.S. Pat. No. 5,695,919 describes a lubricant impregnated core/shell polymer particle, the polymer particle comprising a core portion which is insoluble in the organic medium and a shell portion which has an affinity for both the core portion and the organic medium. However, when the procedure is used to prepare a polymer shell containing a nonionic water soluble vinyl monomer, the resultant particle completely loses its affinity toward any organic solvent medium.
Support materials for an imaging element often employ auxiliary layers comprising glassy, hydrophobic polymers such as polyacrylates, polymethacrylates, polystyrenes, or cellulose esters, for example. One typical application for such an auxiliary layer is as a backing layer to provide resistance to abrasion, scratching, blocking, and ferrotyping. Such backing layers may be applied directly onto the support material, applied onto a priming or “subbing” layer, or applied as an overcoat for an underlying layer such as an antistatic layer, transparent magnetic layer, or the like. For example, U.S. Pat. No. 4,203,769 describes a vanadium pentoxide-containing antistatic layer that is overcoated with a cellulosic layer applied from an organic solvent. U.S. Pat. Nos. 4,612,279 and 4,735,976 describe organic solvent-applied layers comprising a blend of cellulose nitrate and a copolymer containing acrylic acid or methacrylic acid that serve as overcoats for antistatic layers.
Frequently, when the auxiliary layer serves as the outermost layer, as is the case for a backing layer, it is desirable for this layer to have a low coefficient of friction (COF) to provide proper conveyance properties and to protect the imaging element from mechanical damage during the manufacturing process or customer use. It is known to protect imaging elements against mechanical damage by coating them with a layer comprising a lubricant such as a wax. However, it has proven difficult to provide a single layer applied from organic medium that comprises both an abrasion-resistant polymer and a lubricant since it is difficult to find a coating medium that dissolves both the polymer and the lubricant and is at the same time attractive from an enviromental and health standpoint. In addition, it is difficult to form a stable dispersion of a lubricant such as a wax in an organic medium that may be added to a coating composition containing a dissolved, abrasion-resistant polymer. Therefore, in order to form a backing layer which can be applied from liquid organic medium that is both abrasion-resistant and has a low coefficient of friction one often applies two separate layers; a first layer which is comprised of an abrasion-resistant polymer and then a second layer which is comprised of a lubricant such as a wax. The need to apply these two separate layers increases both manufacturing complexity and cost.
It is an objective of the present invention to provide a wax particle which forms very stable dispersions in commonly used organic solvents at room temperature, which is compatible with film forming binders and various coating addenda, and which is highly effective in improving coating physical characteristics.
SUMMARY OF THE INVENTION
The present invention is a polymer particle which includes a wax phase containing a wax having a melting point of greater than 30° C. and a polymer phase. The wax in the wax phase contains greater than 80% by weight of the wax phase. The polymer phase is composed of a mono-alpha, beta-ethylenically unsaturated monomer free of ionic charge groups capable of addition polymerization to form a water soluble homopolymer and a mono-alpha, beta-ethylenically unsaturated monomer capable of addition polymerization to form a water insoluble homopolymer. The mono-alpha, beta-ethylenically unsaturated monomer free of ionic charge groups capable of addition polymerization to form a water soluble homopolymer constitutes from 1 to 40% by weight of the polymer phase.
DETAILED DESCRIPTION OF THE INVENTION
The composite wax particles of the present invention have a wax phase composed of greater than 80% by weight of a wax having a melting point of greater than 30° C. and a non-crosslinked polymer phase containing from 1 to 40% by weight of a polymerizable mono-alpha, beta
Bello James L.
Chen Janglin
Schwark Dwight W.
Wang Yongcai
Eastman Kodak Company
Reddick Judy M.
Wells Doreen M.
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