Paper making and fiber liberation – Processes and products – Mineral fiber
Reexamination Certificate
2001-07-27
2003-02-18
Fortuna, Jose A. (Department: 1731)
Paper making and fiber liberation
Processes and products
Mineral fiber
C162S152000, C162S179000, C162S158000
Reexamination Certificate
active
06521086
ABSTRACT:
The invention involves a glass fiber having a chemical sizing applied on the surface to allow the fiber to disperse quickly and uniformly in plain water, the sizing composition and the methods of making and using the sized fiber.
BACKGROUND
Inorganic staple fiber including glass fiber, ceramic fiber and mineral fiber like mineral, glass or slag wool have been used extensively for reinforcing numerous materials and for enhancing the fire resistance of products. For example, glass fiber has been used to reinforce and enhance the fire resistance and rating of gypsum board.
At least two processes are typically used for adding glass fiber in the manufacture of gypsum board. The first process feeds dried glass fiber having a low moisture content and a chemical sizing on the fiber into wetted calcined gypsum, usually while the wetted material is being mixed and transported in an auger mixer. The fiber is dispersed in the mix by the mixing action. The second process involves adding the fiber directly into the water to make a slurry for a gypsum board before other ingredients are added. The water is typically a low quality, such as tap water, well water, lake or river water, i. e. plant water. The second process using low quality water is preferred by some manufacturers. For the second process, it is necessary that the fiber disperse quickly and uniformly. If it doesn't, each cubic inch of the board won't have enough fibers to pass the fire test and excess fiber will have to be used to insure enough fibers are in each portion of the board.
Unfortunately, the low moisture fiber made for feeding into the wetted gypsum mixture does not disperse uniformly and quickly necessitating that excess dry fiber be used or that a dispersant be added to the water prior to adding the fiber. Some dispersants found to work marginally in dispersing the dry fiber are flammable, presenting an undesirable risk to the manufacturing plants using the fiber.
Other glass fiber products are available in both dried and having a higher moisture content, both with a chemical sizing thereon depending on the intended application. Almost all glass fibers have a chemical sizing on their surface to protect the surface from abrasion and scratches during manufacture and use which will substantially reduce the strength of the fiber. The chemical sizing also can function to aid dispersion and to provide a better bond between the glass fiber and a matrix that the fiber will reinforce, such as a plastic material, a resin binder, etc.
Dry glass fiber products intended for use in plastics products will not disperse sufficiently in water and therefore are not suitable. Various wet chop fiber products, i. e. undried, chopped continuous glass fiber for use in making nonwoven mats in wet process machines or paper machines also did not disperse sufficiently. The sizing on these latter fiber products is designed to cause the fiber to disperse well in a “whitewater” and to bond well to a urea formaldehyde or acrylic resin binder and apparently for that reason do not separate well in plain water, i. e. water without one or more dispersants added. Whitewater used in wet process machines for making mats, unlike plain water in the gypsum board slurry process, contain various viscosity modifiers, defoaming agents, dispersants and other chemical additives that permit the fibers to disperse as desired.
Therefore, there is a need for a fiber product having a chemical sizing thereon that will permit the fiber to disperse quickly, adequately and uniformly in plant water.
SUMMARY OF THE INVENTION
The present invention includes a staple inorganic fiber having a chemical sizing, having a very high surfactant level on its surface. The fibers resulting are advantageous in any process where it is desired to disperse inorganic fiber in plant water. The invention also includes a size composition for inorganic fibers and a method of making a chopped inorganic fiber product for use in dispersing in plant water in a process for making a fiber reinforced product such as gypsum board. The term “staple” includes fibers of various lengths under a few inches long. The fibers can all be of generally the same length or can be a mixture of lengths. For the present invention, lengths of less than 1.5 inches, such as one-half, one, three-fourths, one-quarter, etc. inch long are preferred. A length of one-half inch is particularly suitable for making gypsum board.
The novel size composition on the glass fiber comprises a plant water, deionized water, or distilled water, a high level of surfactant and preferably a film former polymer like polyvinyl alcohol, and can contain a biocide to retard microbial action. The surfactant is preferably a poly (Oxy-1,2-ethanediyl), alpha(2-(bis(2-Aminoethyl) Methyl-ammonio) Ethyl)-omega-Hydroxy-, N,N′-Di(C 14-18 and C 16-18 unsaturated) Acyl Derivs., Me Sulfate (Salts). The sizing composition contains about 0.1-1.2 wt. percent surfactant, preferably about 0.3-0.9 wt. percent and most preferably about 0.6+/−0.1 wt. percent. Other known surfactants compatible with water and known to act similarly to the family of surfactants mentioned just above can be used individually or in combination to replace all or a portion of the family of surfactants described just above.
The film former polymer is preferably present in amounts up to 1.5 wt. percent, preferably about 0.2-0.8 wt. percent and most preferably about 0.5+/−0.1 wt. percent. All weight percentages of the sizing composition are based on the total weight of the sizing including water. When a biocide is used, it is present in effective amounts for this function and that can vary depending on the particular biocide chosen.
The fiber product can be dry or can contain up to about 25 percent moisture. Preferably the fibers are glass fibers chopped in lengths less than 1.5 inches, such as one-half, one, three-fourths, one-quarter, etc. inch long. The fibers can be of any suitable diameter, preferably between 5-23 micron. The fibers have a loss on ignition, due to the chemical sizing on their surfaces, of about 0.08-0.24 percent and preferably about 0.1-0.21 wt. percent and most preferably about 0.13-0.19 percent with a target of about 0.16 wt percent. The surfactant is at least about 30 wt. percent of the LOI and preferably at least 40 wt. percent up to as much as about 60 wt. percent with a film former making up the remainder with the exception of a minor, effective amount of a biocide. The fibers are made according to known processes, but using the inventive size composition to coat the fibers in place of conventional sizing compositions. The invention also includes the method of using the inventive fibers in processes for making fiber reinforced products where the fibers are dispersed in plant water as an early step in the process, such as a process for making gypsum board.
DETAILED DESCRIPTION OF THE INVENTION
Chopped or staple inorganic fiber for use in reinforcements can be made using a number of different processes as is well known. The preferred process for making the preferred embodiment of the present invention which is a chopped sized glass fiber product is a well known process such as shown in U.S. Pat. Nos. 4,692,178, 4,194,896, and 3,869,268, the disclosures of which are incorporated herein by reference. Other processes for making mineral wool, staple glass or ceramic fibers having a chemical sizing on the longitudinal surfaces of the fibers would also be suitable. In the processes for making the preferred embodiments of the invention, which comprise continuously chopped fiber glass strands, glass fibers are pulled from fiberizers in a known way. A water mist is sprayed on the hot fibers to cool the fibers and then the fibers are pulled over a chemical sizing applicator where a chemical sizing, preferably an aqueous chemical sizing, is coated onto the fibers by bringing the fibers into contact with a curved surface having a layer of sizing thereon. The coated fibers are then pulled as a strand, usually along with several other strands of
Fortuna Jos'e A.
Johns Manville International Inc.
Touslee Robert D.
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