Paper making and fiber liberation – Processes and products – Non-fiber additive
Reexamination Certificate
1999-12-14
2002-03-19
Chin, Peter (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-fiber additive
C162S181200, C423S331000, C423S333000, C210S716000, C210S717000
Reexamination Certificate
active
06358365
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
The present application expressly incorporates by reference herein the entire disclosure of U.S. application Ser. No. 09/459,891, entitled “Cellulose Products and Processes for Preparing the Same”, which is concurrently filed with the present application.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to water-soluble metal silicate complexes, such as water-soluble metal silicate complexes containing at least one divalent metal. The present invention is also directed to processes for preparing water-soluble metal silicate complexes. The present invention further relates to waste water treatment processes using water-soluble metal silicate complexes. The present invention also relates to processes for preparing cellulose products, such as paper products, which processes involve adding at least one water-soluble metal silicate complex to a cellulose slurry, such as a paper slurry. Similarly, the present invention relates to processes for preparing cellulose products which processes involve adding at least one water-soluble metal silicate, such as a monovalent cation silicate, to a cellulose slurry so as to form a water-soluble metal silicate complex in the cellulose slurry. The present invention is also directed to cellulose products, such as paper products, containing water-soluble metal silicate complexes.
2. Background of the Invention and Related Art
Cellulose products, such as paperboards, tissue papers, writing papers, and the like are traditionally made by producing an aqueous slurry of cellulosic wood fibers, which may contain inorganic mineral extenders or pigments. The aqueous slurry is deposited on a moving wire or fabric to facilitate the formation of a cellulose matrix. The cellulose matrix is then drained, dried, and pressed into a final cellulose product. However, during the draining step, desired solid fibers, solid fines, and other solids are often removed along with the water. In this regard, solid fines include very short pulp fibers or fiber fragments and ray cells. Solid fines also include pigments, fillers, and other nonfibrous additives that may pass through the fabric during sheet formation. Furthermore, during draining, undesired water is often retained in the cellulose matrix. The removal of the desired solids and retention of undesired water adversely affects sheet formation, and thus yields cellulose products of lower quality. Further, the loss of desired solids is wasteful and costly to cellulose product manufacturers.
As a result, the paper industry continuously strives to provide processes for papermaking that improve the paper quality, increase productivity, and reduce manufacturing costs. Chemicals are often added to the fibrous slurry before the papermaking wire or fabric to improve drainage/dewatering and retention. These chemicals are called drainage and/or retention aids. Attempts have been made to add various drainage and/or retention aids in papermaking such as silicates, silica colloidals, microgels, and bentonites.
Papermaking retention aids increase the retention of fine furnish solids during the turbulent process of draining and forming the paper web. Without adequate retention of the fine solids, they are either lost to the process effluent or accumulate to high levels in the recirculating white water loop, causing potential deposit buildup and impaired paper machine drainage. Additionally, insufficient retention of the fine solids increases the papermaker's costs due to the loss of additives intended to be adsorbed on the fiber to provide the respective paper opacity, strength, or sizing properties.
For example, U.S. Patent No. 5,194,120 to Peats et al. discloses the addition of a cationic polymer and an amorphous metal silicate material to paper furnish to improve fines retention and drainage. The amorphous metal silicates of Peats et al. are white free-flowing powders, which form extremely small anionic colloidal particles when fully dispersed in water. These materials are usually synthesized by reacting a sodium silicate with a soluble salt of the appropriate metal ions, such as Mg
2+
, Ca
2+
, and/or Al
3+
, to form a precipitate which is then filtered, washed, and dried.
WO 97/17289 and family member U.S. Pat. No. 5,989,714 to Drummond relates to a method of controlling drainage and/or retention in the formation of a paper matrix by using metal silicate precipitates. The metal silicate precipitates of Drummond are prepared by mixing a soluble metal salt with a soluble silicate.
JP 63295794 A to Naka-Mura relates to a neutral or weakly alkaline papermaking process which includes adding to the pulp slurry a cationic, water-soluble polymer and an aqueous solution of sodium silicate.
JP 1072793 to Haimo discloses a method for making paper by directly adding an aqueous solution of sodium orthosilicate to the paper slurry. The orthosilicate solution of Haimo is prepared in a separate step (e.g., treatment of aluminum sulfate to adjust the pH) prior to being added to the paper slurry.
U.S. Pat. Nos. 4,927,498; 4,954,220; 5,185,206; 5,470,435; 5,543,014; 5,626,721; and 5,707,494 to Rushmere and Rushmere et al. relate to the use of polysilicate microgels as retention and drainage aids in papermaking. The microgels of many of these patents are manufactured by an on-site process by reacting polysilicic acid with an alkali metal to form microgels which are then added to a paper furnish.
U.S. Pat. No. 5,240,561 to Kaliski relates to the use of microgels in papermaking processes. The microgels of Kaliski are prepared by a two step process. The first step involves the preparation of a transient, chemically reactive subcolloidal hydrosol by blending the paper furnish with two separate solutions. The second step is to blend an aqueous solution containing at least one cross-linking agent with the furnishes resulting from the first step to cross-link the in-situ-formed chemically reactive subcolloidal hydrosol and synthesize (in-situ) the complex functional microgel cements. The resulting cements flocculate the paper furnishes to form paper sheets.
U.S. Pat. No. 4,753,710 to Langley et al. and U.S. Pat. No. 5,513,249 to Cauley are directed to the use of bentonite clays in paper making.
Despite many attempts to provide various types of drainage and retention aids, there still remains a need in the cellulose products industry to provide drainage and retentions aids that are cost effective and at the same time simple to use. In addition, there is still a need for a process of making cellulose products that yields significant improvements in retention and drainage while maintaining good formation of the cellulose product, e.g., paper sheet.
There is still a remaining need for improving retention and drainage, especially for improving drainage in large production of cellulose products where productivity is otherwise reduced due to slow water drainage through thick fibrous mats.
SUMMARY OF THE INVENTION
An object of the present invention is to provide water-soluble metal silicate complexes, such as metal silicate complexes containing at least one divalent metal.
A further object of the present invention is to improve retention and drainage control in making cellulose products, such as paper, by adding a water-soluble metal silicate complex to a cellulose slurry, such as a paper slurry, or by forming a water-soluble metal silicate complex in a cellulose slurry.
Another object of the present invention is to provide processes for preparing cellulose products which processes involve adding at least one water-soluble metal silicate complex to a cellulose slurry, such as a paper slurry.
A similar object of the present invention is to provide processes for preparing cellulose products which processes involve adding at least one monovalent cation silicate to a cellulose slurry, such as a paper slurry, so as to form water-soluble metal silicate complex in the cellulose slurry.
Still another object of the present invention is to provide cellulose products, such as
Taggart Tom E.
Tong Jimei
Zhang Fushan
Chin Peter
Greenblum & Bernstein P.L.C.
Hercules Incorporated
Hug Eric
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