Methods To Control Organic Contaminants In Fibers

Abstract

Methods to control organic contaminants in fibers are described. One method involves contacting the fibers with a) diatomaceous earth and b) detackifier, or an ester hydrolyzing enzyme, or both, for a sufficient time and in a sufficient amount to control the organic contaminants present in the fibers. This method is effective to reduce stickies in paper mill furnish formed with recycled fibers. A method for pitch control in paper mill furnish formed with virgin fibers is also provided. Resulting paper products formed from the processed fibers are also described as well as methods to make them.

Description

[0001]This application claims the benefit under 35 U.S.C. §119(e) of prior U.S. Provisional Patent Application No. 61 / 585,684, filed Jan. 12, 2012, which is incorporated in its entirety by reference herein.BACKGROUND OF THE INVENTION[0002]The present invention relates to papermaking processes and more particularly relates to controlling the organic contaminants present in certain types of fibers used to make paper or similar types of fiber containing products.[0003]Organic contaminants are present in paper pulp that tends to deposit on processing surfaces and equipment, causing maintenance problems and production inefficiencies. Organic contaminants of significant concern in this regard include “stickies” and pitch, with the former generally associated with recycled pulp sources while the latter with virgin pulp supplies.[0004]Conventional recycling of old paper products such as old newsprint, old corrugated containers, and mixed office waste is an important aspect of paper mills to...

AI Technical Summary

Benefits of technology

The present invention provides methods to control organic contaminants in fibers and to process recycled and virgin pulp fibers in a way that organic contaminants are controlled. The methods involve contacting the recycled fibers with diatomaceous earth and at least one detackifier or at least one ester hydrolyzing enzyme for a sufficient time and in a sufficient amount to control stickies present in the recycled fibers. The combination of diatomaceous earth and detackifier or enzyme results in synergistic reductions in sticky amounts from recycled fibers and improved control of stickies compared to either diatomaceous earth, detackifier, or enzymes alone. The methods can be cost-effective as compared to conventional stickies or pitch control programs and can provide reduced downtime, increased machine runnability, reduced furnish cost, improved converting efficiency, increased brightness, improved effective residual ink concentration, improved sheet quality, and / or reduced solvent usage.

Problems solved by technology

Organic contaminants are present in paper pulp that tends to deposit on processing surfaces and equipment, causing maintenance problems and production inefficiencies.

Once caustic agents are used, some yellowing of the fibers can occur which may result in a need to bleach the fibers.

The variable nature of stickies is one of the reasons that controlling or removing them can be difficult and unpredictable.

Also, the use of recycled fiber has been increasing and is expected to continue growing, making stickies a more significant problem.

Recycled paper fibers contain many components that when repulped in recycle fiber plants become stickies.

Stickies deposit on machine surfaces, fabrics, wires, felts, rolls and dryers and lead to problems such as wet end breaks, pressroom breaks, dryer section breaks, holes, sheet defects, and high dirt counts.

These deposits and associated problems lead to a significant amount of downtime yearly.

Floating removes intermediate size stickies (50-300 microns), which are troublesome, because they are small enough to be accepted by screening and cleaning but too large to be removed by washing.

Measuring and controlling stickies in a recycled paper manufacturing process has always been a challenge.

Variations in recycled paper quality and the trend to increase the amount of waste paper incorporated into each ton of pulp produced are each contributing factors that make this challenge even more difficult to address.

These variations make predicting the amount of stickies that are entering a mill's system troublesome.

However, additional stresses on the screens and cleaner banks such as high furnish consistency, improper in-screen dilution, improper reject rates, and differential pressure control problems will facilitate the acceptance of formed macrostickies (Gallagher, 1997).

These materials remain tacky in the paper making process, leading to the “stickies” label (Doshi, 1997).

Once the materials are incorporated into the furnish, they are difficult to remove, since they are deformable in nature and are often close to the specific gravity of water.

These physical characteristics present a different screening and cleaning challenge as these contaminants slip through screens and cleaners (Scholz, 1997) that are designed to allow water and fiber to be accepted.

Even if the cleaning and screening systems do perform properly and do remove most of the macrostickies, the remaining microstickies may cause problems.

However, they often agglomerate in the paper making process leading to macrostickies formation

The cost of stickies deposition is a significant one.

Preventing the agglomeration of microstickies is also an issue in addition to the microstickies problem.

Pitch deposition on process equipment in paper making systems using virgin pulp supplies also can result in operational problems and production inefficiencies.

Pitch deposits may also break off resulting in spots and defects in the final paper product which decrease the quality of the paper.

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