Paper making and fiber liberation – Processes and products – Mineral fiber
Reexamination Certificate
2001-03-08
2004-08-03
Chin, Peter (Department: 1731)
Paper making and fiber liberation
Processes and products
Mineral fiber
C162S164100, C162S166000, C162S167000, C162S168100, C524S216000, C524S512000, C525S518000
Reexamination Certificate
active
06770169
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to glass fiber mats and a process for their production.
Glass fiber mats are composed of glass fibers held together by a binder material. These mats are commonly used in the production of asphalt-containing roofing shingles. A problem with current glass mat manufacturing technology is that the glass mats exhibit a poor balance of tensile strength and tear strength. Although it is known how to increase either tear or tensile strength individually, a formulation or process change made to increase one of these properties will simultaneously decrease the other. Commercial manufacturers of glass fiber mats have long felt a need to have a glass fiber mat in which this balance of properties is improved.
U.S. Pat. No. 4,430,158 (Jackey et al.) discloses a method of preparing a glass fiber mat having improved wet tensile strength by using a binder composition containing a urea formaldehyde resin and 0.01-5 percent of a water-soluble, anionic surfactant, said surfactant having a hydrophobic segment of 8-30 carbon atoms and an anionic segment selected from among carboxy, sulfate ester, phosphate ester, sulfonic acid and phosphonic acid groups. Jackey states that using his binder in an amine oxide white water system gives glass mats that retain up to 79 percent of their dry tensile strength under wet conditions.
U.S. Pat. No. 4,917,764 (Lalwani et al.) discloses that glass fiber mats having improved strength and fiber wetability can be prepared by incorporating 1-6 percent of certain carboxylated styrene butadiene latexes into a urea formaldehyde resin solution and using that solution as a binder.
U.S. Pat. No. 5,518,586 (Mirous) discloses preparation of glass mats using a binder comprising a urea formaldehyde resin plus a water-insoluble anionic phosphate ester in a hydroxyethyl cellulose white water system. Mirous states that Jackey's system gives no improvement in tear strength. Mirous also states that when glass fibers are dispersed in white water containing a polyacrylamide viscosity modifier, high mat tear strengths have been achieved with latex fortification of urea formaldehyde resins.
As a matter of commercial reality, despite the wealth of information in the prior art, glass mat manufacturers desire an affordable binder system that would give increased tear strength and a good balance of tear strength and tensile strength. Current commercially available binder systems do not meet these criteria; they provide satisfactory tear or tensile strength, but not both.
SUMMARY OF THE INVENTION
This invention relates to a method for improving the balance of tensile strength and tear strength of cured, latex-modified urea formaldehyde (UF) resin-bound glass fiber nonwoven mats. The invention is also directed to the glass fiber nonwoven mats produced by the method, and to the binder composition used in the method. The mats are useful in, for example, the manufacture of roofing shingles.
In one aspect the invention is a process for preparing a glass fiber mat, the process comprising: (a) forming a wet glass fiber mat; (b) applying to the wet glass fiber mat a binding amount of a binder comprising: a urea formaldehyde resin, 0.5-15% by weight of a latex, based on the dry weight of the urea formaldehyde resin and the latex, and 0.5-15% by weight, based on the dry weight of the latex solids, of a salt or free acid of an anionic organic phosphate ester surfactant; and (c) curing the binder.
The invention also includes a binder composition comprising a urea formaldehyde resin and 0.5-15% of an emulsion polymer, based on the dry weight of the urea formaldehyde resin and the emulsion polymer, and 0.5-15%, based on the dry weight of the emulsion polymer solids, of a salt or free acid of an anionic organic phosphate ester surfactant. In another aspect, the invention includes a binder composition comprising: (a) a urea formaldehyde resin; (b) 0.5-15% by weight of an emulsion polymer, based on the dry weight of the urea formaldehyde resin and the emulsion polymer, the emulsion polymer containing phosphorus in its polymer molecule as 0.1 to 10% by weight of the polymerized residue of an anionic phosphate group-containing monomer, or from 0.1 to 2 weight percent of the polymerized residue of a perphosphate initiator, or a combination of these, based on the solids of the emulsion polymer; and (c) optionally 0.5-15% by weight, based on the dry weight of the emulsion polymer solids, of a salt or free acid of an organic phosphate ester surfactant. The mat produced using the binder of the invention is also part of the invention.
The present invention enables production of a glass fiber nonwoven mat with a surprisingly improved balance of dry tensile strength and tear strength.
DETAILED DESCRIPTION OF THE INVENTION
The method of the invention employs a binder and glass fibers.
The binder of the invention comprises a UF resin, an emulsion polymer, and a molecule containing a phosphate moiety. The emulsion polymer may also be the molecule containing the phosphate moiety. The molecule containing a phosphate moiety can be incorporated into the binder in several ways. For example, it can be in the aqueous emulsion polymer in the form of a surfactant that is in the reaction mixture when the emulsion polymer is prepared, or it can be in the form of a reactive surfactant that is in the reaction mixture when the emulsion polymer is prepared, or it can be in the form of a perphosphate initiator used when the emulsion polymer is prepared, or it can be added as a surfactant during the formulation of the UF resin, the emulsion polymer or the binder. The phosphate moiety-containing molecule can be incorporated into the binder using any combination of these techniques. For example, the binder may comprise both a surfactant and an emulsion polymer prepared using at least one phosphate group-containing surfactant monomer or perphosphate initiator.
Urea formaldehyde resins are well known and widely commercially available. Examples of commercially available urea formaldehyde resins include CASCO-RESIN C-802B and CASCO-RESIN 520HT, which are available from Borden, Inc. Mixtures of UF resins can be employed. The UF resin is employed in an amount sufficient to provide structural integrity both to the glass mat during processing into a shingle and to the shingle itself. The UF resin suitably is from about 85 to 99.5 weight percent of the binder, based on the dry weight of the UF resin and emulsion polymer in the binder, preferably is from about 88 to about 95 weight percent of the binder, and most preferably is from about 89 to about 93 weight percent of the binder.
Emulsion polymers, such as carboxylated styrene butadiene latexes, are well known and widely commercially available. The emulsion polymers employed in the present invention are copolymers prepared from emulsion polymerization of a monomer mixture comprising at least one of the following: styrene or one or more substituted styrenes; a diene such as butadiene or one or more substituted dienes; vinyl esters such as vinyl propionate, vinyl acetate and isopropenyl acetate; (meth)acrylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and methyl methacrylate; vinyl chloride; acrylonitrile or methacrylonitrile; and the like. Also included are functional monomers such as ethylenically unsaturated carboxylic acid monomers, for example, acrylic acid, methacrylic acid, itaconic acid, fumaric acid and the like; and acrylamide or substituted acrylamides. Copolymers of styrene, butadiene, and a carboxylic acid monomer, optionally including-a phosphate-group-containing surfactant monomer, are preferred. Methods of preparing emulsion polymers are well-known to those skilled in the art. Mixtures of emulsion polymers can be employed.
In one embodiment of the invention, the monomer mixture can include a phosphate group-containing polymerizable surfactant monomer such as, for example the phosphate ester of 2-hydroxyethyl methacrylate, which is commercially available as T MULZ 1228 from Harc
Chin Peter
Dow Reichhold Specialty Latex LLC
Myers Bigel & Sibley Sajovec, PA
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