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  Controlled flow polymer blends and products including the sameUSPTO Application #: 20080045102Title: Controlled flow polymer blends and products including the same Abstract: The present invention is directed to polymer blends having controlled flow properties. The polymer blends can be useful in various applications including bonding systems and additive delivery systems, which can provide durable binding and/or delivery and/or affixing of additives. The polymer blends can include at least two different components, at least one being a polymer component having a higher molecular than the other of the components. When heated to an activating temperature, the resultant blend exhibits desirable flow or wet out properties without applied pressure. Despite the controlled flow properties, the blends do not exhibit blocking or fusing properties typically associated with high flow polymer materials. (end of abstract) Agent: Summa, Allan & Additon, P.A. - Charlotte, NC, US Inventor: Gerald Timothy Keep USPTO Applicaton #: 20080045102 - Class: 442 59 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20080045102. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001]The present invention relates to polymer blends and articles including the same. More particularly, the present invention relates to polymer blends having useful flow or wetting properties without undesirable blocking properties and to products including the same. BACKGROUND OF THE INVENTION [0002]Fibrous materials having various functionalities are useful in many different applications. Often, it can be useful to treat a fibrous material to impart or enhance a particular property thereof, such as flame retardance, UV resistance, and the like. [0003]The functionality of a fibrous material can be modified by introducing a suitable additive into the fibrous structure. Many natural fibers exhibit polar functionality (such as hydroxyl functionality found in cotton fibers), due at least in part to the biological origins of such materials. Nonetheless, functional groups present in many natural fibrous materials can exhibit limited reactivity, and accordingly, additive formulations can simply sit in a bead and not wet out the substrate. [0004]Natural (plant and animal) fibers can be blended with synthetic fibers to formulate functionalized fibrous materials. The differences in physical properties between synthetic and natural fibers, however, can result in phenomena like pilling, which can reduce the desirability and effectiveness of the blend. Other treatments for imparting functionality to natural fibrous materials may be limited to use with liquid vehicles. Yet, to penetrate a fibrous material sufficiently to provide adequate bonding, the fibrous materials are typically saturated with the liquid, which results in a large volume of solution to be handled, removed from the fabric, and disposed in compliance with environmental regulations. [0005]It can be difficult to introduce functional additives into synthetic fibrous materials as well. For example, the crystallinity of certain substrates, such as polypropylene fibrous articles, can present a relatively hard, non-reactive surface to a would-be binder. Many polyester copolymers such as are used as binders in nonwoven fabrics also do not adhere well to polypropylene and/or do not meet needed temperature-flow profiles. Further, the effectiveness of an additive may depend on surface area presentation. For example, silver antimicrobial agents operate via release of silver ions. Yet such activity can be impeded if the antimicrobial agent is buried deep within a treated synthetic fiber or fabric. It can be difficult, however, to locate an active agent on or near the surface of a synthetic fiber, and this difficulty can be acerbated in applications dictating relatively minor amounts of the active agent. [0006]In addition to the issue of effectively introducing an additive into a fibrous material, it can also be difficult to impart permanency to the treated product. Topical treatments can exhibit limited durability or can be readily reversed, particularly when the fibrous material is exposed to washing, cleaning solvents, and other environmental forces that the material itself may be able to withstand, but a coating may not. Even for solvent based additive systems, which can generally withstand numerous washings, there is a desire to move away from solvent based systems due to environmental concerns. [0007]In addition, the additive carrier or binder should have adequate thermal flow to allow it to be applied under commercially feasible conditions and time frames, for example, at lower bonding temperatures and/or residence times. Many polymer systems with high molecular weights (which can be desirable for the requisite physical properties) may lack flowability sufficient to penetrate through a fibrous material. Accordingly, the use of high molecular weight polymer systems may require the application of pressure, such as by calendering. Further, high molecular weight polymer systems may require relatively high bonding temperatures and/or residence times, which can increase energy costs and bonding times associated with using the same. [0008]Polymers have been developed for use in applications requiring relative good flow, such as hot melt adhesion and coating applications. Such polymers can have relatively high melt flow rates so as to impart desirable flow properties to the resultant product. Such polymers, however, typically have lower molecular weights, and thus can exhibit excessive molecular mobility and can be generally tacky or block at normal warehousing and handling conditions. Stated differently, products formed of polymers having relatively high melt flow rates can become "sticky" or "tacky" and thus tend to block, that is, to stick together, when subjected to conditions of elevated temperatures and increased humidity, such as associated with the commercial transportation and warehousing of products. Such polymers can also stick to and bind up on processing equipment, thereby decreasing manufacturing efficiencies. [0009]Various techniques have been proposed to reduce the tendency of high flow polymers to block. Anti-tack agents are offered commercially to improve the block resistance of various polymers. Although useful, many anti-tack agents are only marginally effective, and further may be effective only with specific types of polymers. BRIEF SUMMARY OF THE INVENTION [0010]The present invention is directed to polymer blends exhibiting desirable flow properties without also exhibiting the blocking properties typically associated with high flow polymers. The polymer blends of the invention are capable of substantially wetting out a surface at a flow activating temperature without requiring the application of substantial pressure. Yet despite the melt flow properties of the blends, the polymer blend after applying and solidifying further exhibits blocking resistance properties, thereby facilitating manufacturing and downstream storage and transportation of products produced using the polymer blends. [0011]The polymer blends of the invention include at least two, or more, components that differ from one another with regard to molecular weight. The polymer blend includes a first blend component including at least one polymer having a first molecular weight and a second blend component including at least one compound having a second molecular weight that is less than the first molecular weight of the at least one polymer of the first blend component. The molecular weight of the at least one polymer of the first blend component is sufficiently high to prevent the substantial wet out of the at least one polymer of the first blend component without the application of pressure at the activating temperature of the blend. The second molecular weight of the at least one compound of the second component of the blend is sufficiently low so that the at least one compound of the second component of the blend exhibits a level of molecular mobility sufficient to limit its usefulness by itself for the production of an article such as a fiber or fabric. The at least one compound of the second component of the blend may, for example, exhibit such a high level of molecular mobility that when processed alone, its usefulness is limited because it may be susceptible to blocking, and/or because it may exhibit too much creep, and/or it may have inadequate melt strength or viscosity to be processed. Yet together the blend components can provide a combination of properties including sufficient flow for fiber formation and/or wet-out of a desired substrate without causing problems associated with blocking or creep. [0012]The polymer blends of the invention can be useful in the production of products, such as binder fibers, that can be tailored to exhibit a range of various properties, such flow rates, activation temperatures, melt strengths, blocking temperatures, and the like, depending on the desired application of the product. The inventor has surprisingly found that polymer blends can be prepared of at least two components having high and low molecular weights, relative to one another, that can exhibit a melt strength that is higher than expected given the resulting viscosity of the blend. This is particularly surprising and useful in that it allows the production of articles, such as fibers, from materials that can have unusually low viscosity when remelted, as for instance when used as a binder fiber. The invention accordingly can provide a mechanism to fine tune polymer formulations for specific applications. [0013]In exemplary embodiments of the invention, at least one of the components can include a substantially crystalline polymer, which can promote a sharp flow profile. In other exemplary embodiments of the invention, at least one of the components can include a functionalized polymer component, such as a maleic anhydride functionalized polyolefin, which can improve wetting and/or adhesive properties of the blend. In yet other embodiments of the invention, the polymer blend can include at least one additive. [0014]One exemplary polymer blend of the invention capable of substantially wetting out a surface at a flow activating temperature without requiring the application of substantial pressure, the polymer blend further having blocking resistance properties, can include at least about 10 percent by weight, based on the total weight of the polymer blend, of a first blend component including at least one polymer having a first molecular weight and a glass transition temperature T.sub.g, and at least about 10 percent by weight, based on the total weight of the polymer blend, of a second blend component including at least one substantially crystalline compound having a second molecular weight that is less than the first molecular weight of the at least one polymer of the first blend component and having a melting point that is greater than the T.sub.g of the at least one polymer of the first blend component. In this embodiment of the invention, at least one of the first and second components can include a functionalized polymer, such as a functionalized polyolefin, including maleic anhydride modified polyolefins. [0015]In other aspects, the present invention also provides a polymeric bonding system and bonding methods using the same. The polymeric bonding system of the invention can be in the form of an article, such as a fibrous material, film, foam, coating, a particulate material, and the like, formed of the polymer blend and combinations thereof. [0016]Other aspects of the invention are directed to a polymeric delivery system and additive delivery methods using the same. The polymeric delivery system of the invention can include the polymer blend described herein in combination with an additive, and can also be provided in the form of an article, such as a fibrous material, film, foam, coating, a particulate material, and the like. The polymer delivery system can be applied to a substrate and treated (heated) to promote flow and form a coating. In this embodiment of the invention, the coating can be relatively low add on, can be substantially discontinuous (for example small islands) or substantially continuous, and/or can be applied in a pattern by various techniques. The coating may also be thin and/or flexible, which can aid durability. [0017]The polymer bonding system and the polymeric delivery system of the invention and associated methods can be useful in the production of various articles, including fibrous webs, yarns, and the like and can secure additives to various substrates including natural fibers having limited polar functionality. [0018]Another aspect is directed to composite articles that include a matrix material and the polymer blend of the invention. The matrix material can be selected from fibrous materials, such as synthetic and natural fibers, and cellulosic materials, such as wood fibers and particles. The composite articles can further include an additive. An exemplary embodiment of this aspect of the invention includes an article formed of cotton fibers having an additive, such as an antimicrobial additive, dispersed throughout via fibers formed of a mixture of the polymer blend of the invention and the antimicrobial additive. [0019]Yet another aspect of the invention is directed to an activatable yarn. The activatable yarn includes a plurality of fibrous materials formed of a synthetic polymer having a first molecular weight and a functionalized additive for promoting adhesion of the synthetic polymer to another material and having a second molecular weight that is less than the first molecular weight of the synthetic polymer. Exemplary embodiments of this aspect of the invention include polyolefin and polyester yarns including a maleic anhydride modified polyolefin functionalized additive or an amine functionalized additive. BRIEF DESCRIPTION OF THE DRAWINGS [0020]Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and in which: Continue reading... Full patent description for Controlled flow polymer blends and products including the same Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Controlled flow polymer blends and products including the same 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. 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