Paper making and fiber liberation – Processes and products – Non-fiber additive
Reexamination Certificate
1999-12-14
2002-04-30
Chin, Peter (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-fiber additive
C162S181200
Reexamination Certificate
active
06379501
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to processes for preparing cellulose products, such as paper products which include adding at least one aluminum compound and at least one water-soluble silicate to a cellulose slurry, such as a paper slurry. In particular, the present invention is directed to processes for preparing the cellulose products, such as paper products which include substantially simultaneously or sequentially adding at least one aluminum compound and at least one monovalent cation silicate or water-soluble metal silicate complex to a cellulose slurry, such as a paper slurry. In addition, the present invention is directed to compositions containing at least one aluminum compound and at least one water-soluble metal silicate. The present invention is also directed to cellulose products, such as paper products containing at least one water-soluble metal silicate complex.
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, fibers, 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 the 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.
For example, U.S. Pat. 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, but 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 U.S. Pat. No. 5,989,714 to Drummond relate 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 soluble metal salt with 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 10 72,793 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 has to be 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 these patents are manufactured by an on-site process by reacting polysilicic acid with an alkali metal to form microgels. The microgels are then added to 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. The process of Kaliski is a two-step process that is complicated and time consuming.
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 clay in paper making.
Despite many attempts to provide various types of drainage and retention aids, there still remains a need in the paper industry to provide a process for making cellulose products, such as paper products with excellent drainage and retention that are cost effective and at the same time simple to use. In addition, there is still a need for a cellulose product making process that yields significant improvements in retention and drainage while maintaining good formation of the paper sheet.
There is still a remaining need for a drainage for use in large production of paper products where productivity is not reduced due to slower water drainage through a thicker fibrous mat.
SUMMARY OF THE INVENTION
The present invention is directed to a process for preparing cellulose products which includes substantially simultaneously adding to cellulose slurry (1) at least one aluminum compound, and (2) at least one water-soluble silicate. The water-soluble silicate can be a monovalent cation silicate or a water-soluble metal silicate complex. The water-soluble metal silicate complex can be a reaction product of a monovalent cation silicate and divalent metal ions.
The molar ratio of the aluminum compound to the water-soluble silicate, based on Al
2
O
3
/SiO
2
, is from about 0.1 to 10, preferably from about 0.2 to 5, and more preferably from about 0.5 to 2.
Examples of the aluminum compound include, but are not limited to, alum, AlCl
3
(aluminum chloride), PAC (polyaluminum chloride), PAS (polyaluminum sulfate), PASS (polyaluminum silicate sulfate), and/or poly aluminum phosphate, preferably alum, PAC, and/or PAS, and more preferably alum and/or PAC.
Suitable monovalent cation silicates of the present invention include, but are not limited to, sodium silicate, potassium silicate, lithium silicate, and/or ammonium silicate, preferably sodium silicate and/or potassium silicate, and more preferably sodium silicate. The sodium silicate preferably has an SiO
2
/Na
2
O weight ratio in the range from about 2 to 4, more preferably from about 2.8 to 3.3, and most preferably from about 3.0 to 3.5.
The water-soluble metal silicate complex of the present invention can include at least one of monovalent cation silicate and divalent metal silicate. Examples of the divalent metal silicate include, but are not limited to magnesium silicate, calcium silicate, zinc silicate, copper silicate, iron silicate, manganese silicate, and/or barium silicate. More preferably, the divalent metal silicate includes magnesium silicate, calcium silicate, and/or zinc silicate. Most preferably, the divalent metal silicate includes magnesium silicate and/or calcium silicate.
The water-soluble divalent metal silicate complex is in accordance with the following formula:
(1−y)M
2
O·yM′
Tong Jimei
Zhang Fushan
Hercules Incorporated
Samuels Gary A.
LandOfFree
Cellulose products and processes for preparing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cellulose products and processes for preparing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cellulose products and processes for preparing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2851557