Paper making and fiber liberation – Processes and products – Conditioning – preparing or repairing of apparatus
Reexamination Certificate
2001-03-22
2002-10-08
Nguyen, Dean T. (Department: 3629)
Paper making and fiber liberation
Processes and products
Conditioning, preparing or repairing of apparatus
C162S174000, C162S168100, C162S181800, C162SDIG004
Reexamination Certificate
active
06461477
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods for inhibiting the deposition of organic contaminants in pulp and papermaking systems.
BACKGROUND OF THE INVENTION
The deposition of organic contaminants (i.e., pitch and stickies) on surfaces in the papermaking process is well known to be detrimental to both product quality and the efficiency of the papermaking process. Some components occur naturally in wood and are released during various pulping and papermaking processes. Two specific manifestations of this problem are referred to as pitch (primarily natural resins) and stickies (adhesives or coatings from recycled paper). Pitch and stickies have many common characteristics including: hydrophobicity, tackiness, low surface energy, and the potential to cause problems with deposition, quality, and efficiency in the process as mentioned above.
The term “pitch” can be used to refer to deposits composed of organic constituents which may originate from these natural resins, their salts, as well as coating binders, sizing agents, and defoaming chemicals which may be found in the pulp. In addition, pitch frequently contains inorganic components such as calcium carbonate, talc, clays, titanium and related materials.
Stickies is a term that has been increasingly used to describe deposits that occur in the systems using recycled fiber. These deposits often contain the same materials found in “pitch” deposits in addition to adhesives, hot melts, waxes, and inks. All of the aforementioned materials have many common characteristics including: hydrophobicity, defoamability, tackiness, low surface energy, and the potential to cause problems with deposition, quality, and efficiency in the process. Table I shows the complex relationship between pitch and stickies discussed here.
TABLE I
Pitch
Stickies
Natural Resins (fatty and resin acids, fatty esters,
X
X
insoluble salts, sterols, etc.)
Defoamers (oil, EBS, silicate, silicone oils,
X
X
ethoxylated compounds, etc.)
Sizing Agents (Rosin size, ASA, AKD, hydrolysis
X
X
products, insoluble salts, etc.)
Coating Binders (PVAC, SBR)
X
X
Waxes
X
Inks
X
Hot Melts (EVA, PVAC, etc.)
X
Contact Adhesives (SBR, vinyl acrylates,
X
polyisoprene, etc.)
The deposition of organic contaminants, such as pitch and stickies, can be detrimental to the efficiency of a pulp or paper mill causing both reduced quality and reduced operating efficiency. Organic contaminants can deposit on process equipment in papermaking systems resulting in operational difficulties in the systems. The deposition of organic contaminants on consistency regulators and other instrument probes can render these components useless. Deposits on screens can reduce throughput and upset operation of the system. This deposition can occur not only on metal surfaces in the system, but also on plastic and synthetic surfaces such as machine wires, felts, foils, Uhle boxes and headbox components.
Historically, the subsets of the organic deposit problems, “pitch” and “stickies” have manifested themselves separately, differently and have been treated distinctly and separately. From a physical standpoint, “pitch” deposits have usually formed from microscopic particles of adhesive material (natural or man-made) in the stock which accumulate on papermaking or pulping equipment. These deposits can readily be found on stock chest walls, paper machine foils, Uhle boxes, paper machine wires, wet press felts, dryer felts, dryer cans, and calendar stacks. The difficulties related to these deposits included direct interference with the efficiency of the contaminated surface, therefore, reduced production, as well as holes, dirt, and other sheet defects that reduce the quality and usefulness of the paper for operations that follow like coating, converting or printing.
From a physical standpoint, “stickies” have usually been particles of visible or nearly visible size in the stock which originate from the recycled fiber. These deposits tend to accumulate on many of the same surfaces that “pitch” can be found on and causes many of the same difficulties that “pitch” can cause. The most severe “stickies” related deposits however tend to be found on paper machine wires, wet felts, dryer felts and dryer cans.
Methods of preventing the build-up of deposits on the pulp and paper mill equipment and surfaces are of great importance to the industry. The paper machines could be shut down for cleaning, but ceasing operation for cleaning is undesirable because of the consequential loss of productivity, poor quality while partially contaminated and “dirt” which occurs when deposits break off and become incorporated in the sheet. Preventing deposition is thus greatly preferred where it can be effectively practiced.
In the past stickies deposits and pitch deposits have typically manifested So themselves in different systems. This was true because mills usually used only virgin fiber or only recycled fiber. Often very different treatment chemicals and strategies were used to control these separate problems.
Current trends are for increased mandatory use of recycled fiber in all systems. This is resulting in a co-occurrence of stickies and pitch problems in a given mill. It is desirable to find treatment chemicals and strategies which will be highly effective at eliminating both of these problems without having to feed two or more separate chemicals.
It was suggested that gelatin could be used as a remedy for pitch control. U.S. Pat. No. 5,885,419, the entire content of which are wherein incorporated by reference discloses blood-related proteins such as albumins and globulins for preventing pitch/stickies deposition in the pulp and paper industry. However, the milk protein used in the patent proved to be ineffective. The patent does not reveal the physical/chemical properties of this milk protein; however, its poor performance indicates the exclusion of he high molecular weight whey proteins which surprisingly found to be very effective in this invention.
BRIEF SUMMARY OF THE INVENTION
The present invention provides for compositions and methods for inhibiting the depositions of organic contaminants from pulp and papermaking systems.
The present invention provides for methods for inhibiting the deposition of organic contaminants, such as pitch and stickies, in pulp and papermaking systems. The methods comprise adding to the pulp or applying to the surfaces of papermaking machinery an effective deposition inhibiting amount of a combination of a whey protein and a cationic polymer.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to methods for inhibiting the deposition of organic contaminants from pulp on the surface of papermaking machinery in pulp and papermaking systems comprising adding to pulp or applying to the surfaces of the paper making machinery an effective deposition inhibiting amount of a whey protein. The present invention provides for methods for inhibiting the deposition of organic contaminants, such as pitch and stickies, from pulp and papermaking systems.
Organic contaminants include constituents which occur in the pulp (virgin, recycled or combinations thereof) having the potential to deposit and reduce paper machine performance or paper quality. These contaminants include but are not limited to natural resins such as fatty acids, resin acids, their insoluble salts, fatty esters, sterols; and other organic constituents such as ethylene bis-stearamide, waxes, sizing agents, adhesives, hot melts, inks, defoamers, and latexes which may deposit in papermaking systems.
There are two fundamentally different groups of proteins present in milk, casein and whey. Casein proteins are heat insensitive. Whey proteins are heat sensitive. Table I shows the major differences in properties between casein and whey proteins, including the major proteins in each group and their percentage contribution to the total protein in milk.
TABLE I
Properties of Milk Proteins and Their Major Components
Protein
Protein in
Type
Structures and properties
Individual Proteins
milk %
Casein
Contains strongly hydrophobi
Gu Qu-Ming
Nguyen Duy T.
Hercules Incorporated
Nguyen Dean T.
Rossi Joanne M.
Samuels Gary A.
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