Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic phosphorus compound – wherein the phosphorus is...
Reexamination Certificate
1994-03-02
2001-02-20
Johnson, Jerry D. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic phosphorus compound, wherein the phosphorus is...
C106S213100, C106S287240, C524S140000
Reexamination Certificate
active
06191079
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to lubricant additives for coating moving paper and paper board web materials.
Paper and paper board web material is frequently coated to improve properties such as appearance and printability. The coating process involves applying a coating mixture to the paper as it moves at high speed through a coating apparatus. These coatings are typically composed of: (a) pigments, such as Kaolin clay, titanium dioxide, calcium carbonate or silicates; (2) adhesive binders, such as starches, styrene butadiene latex, or polyvinyl acetates; and (3) additives, which improve or modify specific properties and characteristics of the coating mixture.
A number of chemical phenomena and physical forces (particularly shear forces) can have a detrimental effect, e.g., destroying the integrity and uniformity of both the coating mixture and the coating as it is applied to the paper sheet. When this occurs, costly problems develop both in the application of the coating and in the finish and quality of the coated paper. These problems are widely known to manufacturers of coated papers.
These problems are greatly magnified as the speed of the web moving through the coating apparatus is increased, causing increased shear forces on the coating mixture being applied. Increased speed causes problems in viscosity control, calcification, streaking, whiskering, and generally poor “runnability” (performance) of the coating. These problems ultimately result in a poor quality coated sheet. Uniformity of the coating mix at these high shear levels is critical.
2. Discussion of Related Art
Typically, lubricant additives, such as calcium stearate dispersions or polyethylene emulsions, have been used as an additive to the coating mixture to improve the performance and uniformity of the coating and the overall integrity of the coating mixture. The main function of a lubricant additive in a coating mixture is to increase the lubricity of the coating. However, many other effects of lubricants are known to the art of coating paper. For example, such characteristics as rheological properties, plasticity, smoothness, coating gloss, anti-dusting and improved printing qualities, can be affected by the use of coating lubricants.
In U.S. Pat. No. 4,766,015 there is provided a lubricant additive mixture adapted for combination with an aqueous-based paper or paper board coating mixture. The additive mixture comprises a fatty acid, a surfactant, and a phospholipid composition such as a lecithin. Likewise, a paper coating composition is disclosed in U.S. Pat. No. 4,183,766 wherein the effectiveness of pigment coating compositions for printing paper stock is enhanced by the use of phosphate esters of aliphatic alcohols or their salts therein. However, there is a constant need for better or improved systems in paper coating color formulations.
DESCRIPTION OF THE INVENTION
Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term “about”.
It has now been found that polyoxyalkylene mono- and di-esters of phosphoric acid, and polyoxyalkylene mono- and di-esters of phosphoric acid salts significantly improve the properties of aqueous coatings for rapidly moving webs, such as paper webs.
In one aspect of this invention there is provided a method of applying an aqueous-based coating to a rapidly moving paper or paper board web wherein a lubricant additive comprising a polyoxyalkylene mono- or di-ester of phosphoric acid or a salt thereof is included in the coating mixture to be applied to the web. By aqueous-based is meant that the vehicle for the coating mixture is water or water and a water-miscible liquid.
The lubricant additive of this invention comprising a polyoxyalkylene mono- or di-ester or mixtures thereof of a phosphoric acid salt may have a structure according to the following formula 1 or formula 2
wherein R represents a hydrophobic tail such as an alkyl group, alkenyl group, aryl group, alkylaryl group, alkenyl aryl group, arylalkyl group, arylalkenyl group, or hydroxyalkyl group, n is an integer from about 1 to about 50, m is an integer from 0 to about 50, and n+m is preferably from about 1 to about 15.
The coating composition to be applied to the web may contain (1) pigments such as kaolin clay, calcium carbonate, titanium dioxide, etc., (2) binders such as starches, styrene butadiene rubber latexes, polyvinyl acetate latexes, and (3) other conventional additives in such compositions, including a nonionic, cationic and anionic surfactant.
The coating composition is applied to a paper or paper board web traveling at least 500 feet per minute, and generally much faster, for example, over 3500 feet per minute. In addition, a short-dwell application method may be employed, that is, a method wherein the coating composition is applied to the web under pressure while a device such as a doctor blade controls thickness of the coating composition. The coating composition preferably has a solids content of between about 50 and about 75% by weight, wherein the solids comprise on a weight basis, 8 to 12% binder, 80 to 90% pigment, and 0.5 to 1.5% lubricant additive selected from a polyoxyalkylene mono- and di-ester of phosphoric acid, and a polyoxyalkylene mono- and di-ester of phosphoric acid salt. To make the coating composition, a lubricant additive mixture containing 20 to 100% polyoxyalkylene mono- or di-ester or mixtures thereof of phosphoric acid or a salt thereof, 0 to 80% fatty acid or fatty acid salts, urea, molasses, corn syrup, ethoxylated glycerol or ethoxylated, propoxylated glycerol, and 0 to 3% emulsifier is provided and then mixed with a pigment-containing formulation. The coating composition may include a plasticizer such as a polyol, for example, a glycol, particularly dipropylene glycol.
The resulting coating composition enables a high solids content and can be used in high-speed paper coating equipment such as short-dwell equipment. The preferred coating composition contains clay pigment such as Kaolin clay, but other coatings may contain calcium carbonate, titanium dioxide, silica, zinc oxide, aluminum powder, synthetic polymers, talc, and diatomaceous earth.
In a further aspect of this invention, there is provided a lubricant additive suitable for combination with an aqueous-based paper or paper board coating composition, comprising a polyoxyalkylene mono- or di-ester or mixtures thereof of phosphoric acid, or a polyoxyalkylene mono- or di-ester or mixtures thereof of a phosphoric acid salt, a fatty acid, alkali metal salt of a fatty acid, or alkaline earth metal salt of a fatty acid, urea, molasses, corn syrup, ethoxylated glycerol, ethoxylated propoxylated glycerol and appropriate emulsifiers. The coating composition is preferably an aqueous slurry adapted for application to a rapidly moving web. The invention enables desirable Theological properties at high solid loading in the slurry, thus reducing the energy consumed to dry the liquid from the coated product. In addition, the invention maintains the smoothness and integrity of high-solid coatings, reducing unevenness or calcification. Specifically, the invention greatly improves the rheological properties and runnability of the wet coating at high speeds and in shear stress systems. In addition, this invention improves the characteristics of the dried coated paper.
This invention allows the use of coating mixtures in excess of 50% solids by weight. The lubricant can be supplied at 100% active ingredient level. This feature allows the coating formulator to prepare coating mixtures at desirable high solids levels and reduces the amount of water present in the mixture which must be subsequently dried after application.
This invention improves the runnability of the coating mixture in high speed coaters and good results have been obtained on many types of coating equipment. The coating additive contributes to the production of a
Klima Rudolph
Krasniewski John
Rodriguez Jose Maria
Geo Specialty Chemicals, Inc.
Johnson Jerry D.
Rankin, Hill Porter & Clark LLP
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