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Strength additives for tissue productsRelated Patent Categories: Paper Making And Fiber Liberation, Processes And Products, Non-fiber Additive, Synthetic ResinStrength additives for tissue products description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060027349, Strength additives for tissue products. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] In the art of tissue making and papermaking, many additives have been proposed for specific purposes, such as increasing wet strength, improving softness, or controlling wetting properties. For instance, in the past, wet strength agents have been added to paper products in order to increase the strength or otherwise control the properties of the product when contacted with water and/or when used in a wet environment. For example, wet strength agents are added to paper towels so that the paper towel can be used to wipe and scrub surfaces after being wetted without the towel disintegrating. Typical wet strength agents are also added to facial tissues to prevent the tissues from tearing when contacting fluids. In some applications, wet strength agents are also added to bath tissues to provide strength to the tissues during use. When added to bath tissues, however, the wet strength agents should not prevent the bath tissue from disintegrating when dropped in a commode and flushed into a sewer line. Typical wet strength agents added to bath tissues are sometimes referred to as temporary wet strength agents since they only maintain wet strength in the tissue for a specific length of time. [0002] Although great advancements have been made in providing wet strength properties to paper products, various needs still exist to increase wet strength properties in certain applications, or to otherwise better control the wet strength properties of paper products. [0003] For instance, a reoccurring need in the production of tissue products is to improve the softness of the product at a given geometric mean tensile strength. In other words, one objective in producing tissue products is to produce a product having high softness and high strength. In the past, softness was increased by adding debonders to the web which reduced hydrogen bonding of the fibers. Strength was then built back into the web by adding various strength agents, such as a polyaminoamide epichlorohydrin. Although epichlorohydrin resins are well suited for this purpose, the resins are generally not biodegradable. As such, there is a need not only to develop strength agents that improve the strength of paper webs without substantially impacting softness, but there is also a need to develop a biodegradable strength agent that can be used as a replacement to traditional epichlorohydrin resins. SUMMARY OF THE INVENTION [0004] The present invention is generally directed to paper products having improved strength properties due to the presence of a strength agent. The strength agent can increase the tensile strength of the paper product in either the dry state or the wet state. In one embodiment, the strength agent is added to a tissue product, such as a facial tissue, a bath tissue, a paper towel, an industrial wiper, and the like. [0005] In one embodiment, the paper product of the present invention includes a fibrous web containing cellulosic fibers. The fibrous web is treated with a strength agent comprising a derivatized polyethylene oxide. The strength agent is present in the fibrous web in an amount sufficient to increase the tensile strength of the web. [0006] The derivatized polyethylene oxide can contain derivative groups in an amount from about 0.5 percent to about 25 percent by weight. The derivatized polyethylene oxide can be present in the fibrous web in an amount from about 0.05 percent to about 10 percent by weight of fibers contained in the web. The derivatized polyethylene oxide can be incorporated into the fibrous web by pretreating fibers with the polymer and then forming the web. Alternatively, the derivatized polyethylene oxide can be topically applied to at least one surface of the fibrous web. [0007] An added benefit of the strength agents disclosed in the present invention is that they can enhance the tactile feel of the product when used in the wet stated. Many textile materials have an increased coefficient of friction on their surfaces when wet. For example, clothing such as shirts and other garments are harder to put on or take off when wet or when going on over wet skin. In a like manner, many wiping products, such as facial tissues, bath tissues, paper towels, and the like, also experience this same phenomenon. For instance, tissue products typically have more drag across the surface when wet than when in the dry state. Increased drag can be noticed even if the tissue product has a smooth surface and/or has been chemically treated so as to have a very low coefficient of friction in the dry state. Thus, a tissue that is used in the wet state may have an actual tactile sensory feel that is quite different than the same tissue used in the dry state. This increased coefficient of friction may not only be less desirable to the user but may also lead to a high level of slough when wet. [0008] Other features and aspects of the present invention are discussed in greater detail below. BRIEF DESCRIPTION OF THE DRAWINGS [0009] A full and enabling disclosure of the present invention, including the best mode thereof to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures in which: [0010] FIG. 1 is a schematic diagram of one embodiment of a process for forming paper webs that can be used in the present invention; and [0011] FIG. 2 is a perspective view of another alternative embodiment of a process for producing paper webs that may be used in the present invention. [0012] Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the present invention. DETAILED DESCRIPTION OF THE INVENTION [0013] It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention. [0014] In general, the present invention is directed to treating a paper product, such as a tissue product, with a strength agent comprising a derivatized polyethylene oxide. For example, a base web containing pulp fibers can be treated with a derivatized polyethylene oxide. The derivatized polyethylene oxide can be crosslinked in the web to provide both wet and dry strength. [0015] The use of a derivatized polyethylene oxide to improve the strength properties of a base web has been found to provide various advantages and benefits. For example, the present inventors have discovered that the derivatized polyethylene oxide can increase the strength of the base web without significantly impacting the stiffness of the web, which is one measure of the softness of the web. For example, it has been found that the tensile strength of the web can be increased, such as the TEA (Total Energy Absorbed) of the web, without a significant increase in the tensile modulus of the web. Furthermore, the additives of the present invention can be used to provide for an enhanced feel when the product is moist. The additives of the present invention show significantly lower coefficient of friction values when used in the moist state compared to products not containing these strength additives. [0016] The derivatized polyethylene oxides of the present invention can be used to replace traditional epichlorohydrin resins (or any resins made from chloropropyl alcohol). The derivatized polyethylene oxides are more environmentally friendly and are generally biodegradable. Thus, paper webs can be produced having improved strength properties without containing any of the epichlorohydrin resins used in the past. It may, however, at times be advantageous to use the strength additives of the present invention in conjunction with the standard polyamidoamine epichlorohydrin resins broadly known in the art. [0017] A derivatized polyethylene oxide may be formed by reacting a polyethylene oxide with one or more monomers to provide a functional group on the polyethylene oxide polymer. The derivative groups can be placed in the backbone of the polyethylene oxide or can be pendent groups. The derivative groups can be present in the polymer in an amount from about 0.5 percent to about 25 percent by weight, such as from about 0.5 percent to about 10 percent by weight. [0018] Prior to being derivatized, polyethylene oxides can have the following general formula: R.sup.1O--(CH.sub.2CH.sub.2CH.sub.2O).sub.n R.sup.2 wherein R.sup.1 and R.sup.2 are hydrogen or organofunctional groups. R.sup.1 and R.sup.2 can be the same or different. [0019] In general, the molecular weight of the polyethylene oxide that is derivatized is not critical as long as enough derivatized groups can be placed on the polymer that are capable of crosslinking in sufficient quantity with cellulose for a desired result. For many applications, the molecular weight of the polyethylene oxide that is derivatized is greater than about 20,000, and particularly greater than about 50,000. As used herein, molecular weight can be determined by rheological measurements. In one embodiment, for instance, the polyethylene oxide can have a molecular weight of from about 100,000 to about 2 million. [0020] High molecular weight polyethylene oxides are available from various commercial sources. Examples of polyethylene oxide resins that can be derivatized and used in the present invention are commercially available from the Union Carbide Corporation and are sold under the trade designations POLYOX N-205, POLYOX N-750, POLYOX WSR N-10 and POLYOX WSR N-80. The above four products are believed to have molecular weights of from about 100,000 to about 600,000 (g-mol). The polyethylene oxide resins may optionally contain various additives such as plasticizers, processing aids, rheology modifiers, antioxidants, UV light stabilizers, pigments, colorants, slip additives, antiblock agents, etc. Continue reading about Strength additives for tissue products... Full patent description for Strength additives for tissue products Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Strength additives for tissue products patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Strength additives for tissue products or other areas of interest. ### Previous Patent Application: Method for producing paper or board and a product produced by the method Next Patent Application: Method for producing a fibrous material web and monitoring system Industry Class: Paper making and fiber liberation ### FreshPatents.com Support Thank you for viewing the Strength additives for tissue products patent info. IP-related news and info Results in 0.14319 seconds Other interesting Feshpatents.com categories: Computers: Graphics , I/O , Processors , Dyn. Storage , Static Storage , Printers 174 |
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