Multi-step pulp bleaching

a pulp bleaching and multi-step technology, applied in the field of multi-step pulp bleaching, can solve the problems of affecting affecting the quality of pulp fibers used in the original production of waste paper products, and affecting the quality of pulp fibers used in the original production of those waste paper products, and affecting the quality of pulp fibers. the effect of premium virgin or premium recycled fibers

Inactive Publication Date: 2008-04-17
GEORGIA PACIFIC CONSUMER PRODS LP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Recycling of other waste papers, like those from curbside residential recycling, is more costly and difficult.
Because those papers tend to include substantial groundwood content, the current technology used to recycle premium fibers is ill-suited for these lower grades of waste paper.
More specifically, the lower grade pulp fibers used in the original production of those waste paper products suffer from a decreased brightness over the premium virgin or premium recycled fibers.
Thus, the recycled fibers from those waste paper products cannot easily be used to create premium or near-premium quality consumer products like bath tissue, facial tissue, paper towels, and napkins, since consumers tend to prefer higher brightness fibers in these products.
Even though current technologies make it possible to recycle s...

Method used

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  • Multi-step pulp bleaching

Examples

Experimental program
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Effect test

example 1

[0074]The starting fibers in Example 1 were recycled cellulosic fibers collected prior to any bleaching step. The initial brightness of the recycled cellulosic fibers was 66.5 GE; the Kappa number of the recycled cellulosic fibers was 26.3; the delta a* of the recycled cellulosic fibers was 19.65. A description of the a* value and processes for determining that value are found in U.S. Published Patent Application Nos. 2004 / 0000383 and 2004 / 0079497, which are assigned to the assignee of this application and which are incorporated by reference herein in their entireties.

[0075]Those starting fibers were then bleached according to a conventional Eop / Y process. In particular, the fibers were bleached in a Quantum mixer under an alkaline peroxide step, with hydrogen peroxide as the alkaline peroxide agent, in conditions listed in Table 1 as “EOP Conditions.” The two 15-minute charges of oxygen at 60 PSIG involved pressurizing the quantum mixer to 60 PSIG for 15 minutes, relieving the mixe...

example 2

[0076]In Example 2, 0.3 grams of TAED powder (Clariant trade name PERACTIVE®-P) was added to a sample of the same starting recycled fibers used in Example 1. The fibers were then bleached using alkaline hydrogen peroxide under the EOP conditions listed in Example 1. The fibers were sampled after the first 15 minute oxygen charge and the fibers were measured to have a 74.7 GE brightness. After the second 15 minute oxygen charge, the fibers were measured to have a 76.4 GE brightness. The fibers were also tested and found to contain substantially no residual oxidant, indicating that bleaching was complete. The Eop / direct addition of TAED process of this Example 2 resulted in a larger brightness gain than the conventional Eop / Y bleaching process of Example 1.

example 3

[0077]In Example 3, an additional 0.5% hydrogen peroxide charge, at 10 lb / ton, was added to resulting fibers of Example 2 and retained under atmospheric pressure for two hours. The fibers surprisingly achieved a 78.5 GE brightness, or an additional 2.1 GE points over the resulting fibers from Example 2. The addition of hydrogen peroxide after complete bleaching, such as in Example 2, generally does not result in any significant brightness increase. However, this Eop / TAED+P process of Example 3 resulted in an unexpected additional brightness gain over the Eop / TAED process of Example 2, due to the continued bleaching effects of TAED in the presence of the additional hydrogen peroxide charge.

[0078]The fibers from this example contained 0.2 g / L, or approximately 0.2%, residual peroxide. That residual peroxide amounted to about 6% of the additional peroxide added, which is a good amount of consumption for a bleaching process.

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Abstract

A method for bleaching cellulosic pulp is disclosed, with one embodiment revealing a three-step bleaching method for cellulosic pulp comprising an activating bleach step, an alkaline peroxide step, and a reductive bleach step. The cellulosic pulp treated according to the present invention may possess a greater GE brightness gain than if treated according to conventional methods, while not suffering a significant loss of lignin. The cellulosic pulp may comprise recycled fibers, including those with high groundwood content. The bleaching method may also decrease the pH of the pulp.

Description

BACKGROUND OF THE INVENTION[0001]Methods for bleaching cellulosic fibers, including secondary or recycled fibers, are disclosed. In one embodiment, a method for bleaching recycled pulp fibers increases the brightness of the fibers without significant delignification. In a further embodiment, a method for bleaching cellulosic fibers involves at least two steps. In another embodiment, a method for bleaching cellulosic fibers reduces the pH of the pulp fibers by at least about 2 while also increasing the GE brightness by at least about 9.[0002]Considerable resources have been invested in determining effective ways to recycle the increasingly vast amount of waste paper generated each day. Presently, almost 100 percent of the highest quality grades of paper, like printer's clippings and white office waste, is recycled. Those grades are considered premium secondary or recycled fiber sources as the original, high quality of the chemically produced virgin paper fibers makes it relatively in...

Claims

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Application Information

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IPC IPC(8): D21B1/32D21C3/22
CPCD21C9/1057D21C9/1084D21C9/166D21C9/16D21C9/12
Inventor LEE, JEFFREY A.KEEN, STEPHANIE A.THOMAS, H. CHARLESSUMNICHT, DANIEL W.
Owner GEORGIA PACIFIC CONSUMER PRODS LP
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