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  Infusion fabric allowing high resin infusion ratesUSPTO Application #: 20080085650Title: Infusion fabric allowing high resin infusion rates Abstract: A reinforcement fabric includes a first layer of collimated continuous fibers, a second layer selected from a group consisting of veil, continuous filament mat, chopped strand mat, direct chopped mat, direct continuous mat, collimated continuous fibers, woven fabric, non-woven fabric, scrim and combinations thereof as well as a surface adhesive that adheres the first and second layers together. The surface adhesive is selected from a group consisting of hot melt adhesive and web bonded adhesive. The surface adhesive has a melt flow index range of about 5 to about 500 at room temperature and about 900 to about 1300 at application temperature. A method is also provided for the production of the reinforcement fabric. (end of abstract) Agent: Owens Corning - Granville, OH, US Inventor: David R. Hartman USPTO Applicaton #: 20080085650 - Class: 442366 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20080085650. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION [0001]This invention relates generally to an infusion or reinforcement fabric that may be molded into large composite structures as well as to a method for producing such a fabric. BACKGROUND OF THE INVENTION [0002]Reinforcement fabrics made from fibrous materials formed into woven, knitted and non-woven material, are well known in the art. Yarns of glass, carbon and aramid are typically formed into fabrics, and a plurality of layers of fabric are stacked and cut into dry fabric kits or preforms. The preforms are then infused or impregnated with a resin binder and cured to form a rigid composite. [0003]Typically, the preforms include one or more layers of oriented fiber material that are assembled and shaped prior to insertion into a mold for resin injection. The mold is closed and resin is then injected into the mold to infiltrate between the fibers to complete the composite part. [0004]In order to obtain the desired strength and structural integrity in the final part it is necessary to maintain the directional orientation of the fibers during the resin impregnation and molding process. This can be accomplished in one of two ways. In the first, the unidirectional fibers are stitched together or held together by transverse fibers. Unfortunately, stitching generally reduces the toughness of the composite. Further, the stitching and/or transverse fibers generally slow the impregnation process and make the unidirectional fibers more difficult to wet out. [0005]Alternatively, the unidirectional fibers may be held in place by preimpregnation with resin. While generally sufficient to hold the fibers together during resin infusion and molding, the resin used for preimpregnation has an unfortunate tendency to interfere or slow resin impregnation during the molding process thereby making it difficult to properly wet out the unidirectional fibers. [0006]The present invention relates to an improved infusion fabric that better optimizes kitting, preforming, conformability to tooling, resin infusion rate, consolidation thickness, surface aesthetics and composite structural performance in a range of closed molding processes including VIP, RTM and RTM Lite or VARTM processes. This represents the full range of composite closed molding processes used by marine, wind, construction, transportation and industrial customers. More specifically, the reinforcement fabric of the present invention provides sufficient stiffness to hold vertical mold surfaces and maintain fiber alignment for optimal composite mechanical properties like compressive strength and strain to failure. Simultaneously, the fabric allows very rapid resin infusion rates to insure complete wet out of the fibers and optimal molding of components with the highest quality. SUMMARY OF THE INVENTION [0007]In its simplest form, the reinforcement fabric comprises (a) a first layer of collimated continuous fibers, (b) a second layer selected from a group consisting of veil, continuous filament mat, chopped strand mat, direct chopped mat, direct continuous mat, collimated continuous fibers, woven fabric, non-woven fabric, scrim and combinations thereof and (c) a surface adhesive. The surface adhesive adheres the first and second layers together. The surface adhesive is selected from a group consisting of a hot melt adhesive and a web bonded adhesive. The surface adhesive has a melt flow index range of about 5 to about 500 at melt temperature and about 900 to about 2500 at application temperature. In one possible embodiment the reinforcement fabric is stitchless, relying completely upon the surface adhesive to hold the collimated continuous fibers in alignment. [0008]The collimated continuous fibers are selected from a group of materials consisting of glass fibers, carbon fibers, graphite fibers, vitreous carbon fibers, non-graphite carbon fibers, boron monolithic graphite fibers, boron monolithic non-graphite carbon fibers, silicone, aramid, ceramic fibers, thermoset polymer fibers, thermoplastic polymer fibers, natural fibers and mixtures thereof. The second layer is constructed from a material selected from a group of materials consisting of glass fibers, carbon fibers, graphite fibers, vitreous carbon fibers, non-graphite carbon fibers, boron monolithic graphite fibers, boron monolithic non-graphite carbon fibers, silicone, aramid, ceramic fibers, thermoset polymer fibers, thermoplastic polymer fibers, natural fibers and mixtures thereof. [0009]More specifically describing the invention the collimated continuous fibers have a strand size of between about 100 to about 10,000 tex and a filament diameter of between about 9 to about 30 microns. In a typical application, the collimated continuous fibers have a strand size of between about 600 to about 8,000 tex and a filament diameter of between about 12 to about 26 microns. [0010]The chopped fibers have a strand size of between about 1,000 to about 8,000 tex and a filament diameter of between about 6 to about 30 microns. The chopped fibers have a tex of between about 10 to about 1,000 in split strands. The filaments in the veil are stranded, fully dispersed or a combination of stranded and fully dispersed. In addition the reinforcement fabric includes a size having reagents selected from a group consisting of water, acetic acid, a lubricant, a film former, a silane coupling agent, a biocide and mixtures thereof. [0011]The surface adhesive is formulated or selected from a group consisting of PE, microcrystalline wax, EVA, modified EVA, ethylene-acrylic ester copolymer, ethylene-acrylic ester-maleic anhydride terpolymers, copolyesters, copolyamides, amorphous polypropylene, synthetic rubbers, acrylic block copolymers, and combinations thereof. Where the surface adhesive is a web bonded adhesive, it is characterized by a tack of between about 0.5 and about 1 N/m. [0012]The reinforcement fabric has a weight per unit area of between about 0.5 and about 3 kg/sm and comprises between about 30 and about 80 weight percent first layer, between about 20 and about 70 weight percent second layer and between about 0.1 and about 2 weight percent surface adhesive. The surface adhesive is applied at an areal weight of between about 2 and about 30 gsm. [0013]In accordance with an additional aspect of the present invention a method is provided for producing a reinforcement fabric. That method comprises: (a) forming a collimated sheet of continuous fibers; (b) providing a surface adhesive selected from a group consisting of a hot melt adhesive and a web bonded adhesive having a melt flow index range of about 5 to about 500 at melt temperature and about 900 to about 2500 at application temperature; and (c) consolidating the collimated sheet with a layer of material selected from a group consisting of veil, continuous filament mat, chopped strand mat, direct chopped mat, direct continuous mat, collimated continuous fibers, woven fabric, non-woven fabric, scrim and combinations thereof. [0014]The forming step includes the additional steps of feeding a plurality of continuous fibers from a creel and providing the surface adhesive as a web. The forming step may also include the making of the surface adhesive into a web in line. Further the forming step may include the extruding of the surface adhesive as a hot melt. Where the surface adhesive is a hot melt the method includes the applying of the hot melt adhesive in a pattern selected from a group consisting of a sinusoidal pattern, a loop pattern, a straight line pattern and combinations thereof. The surface adhesive is applied at an areal density of between about 2 and about 30 gsm. Further the method includes completing the consolidating at a rate of between about 50 and about 500 meters/minute. [0015]In accordance with an additional aspect of the present invention the reinforcement fabric comprises a surfacing veil, a continuous filament mat, at least one sheet of collimated continuous fibers, a layer of woven or non-woven fabric and a surface adhesive. The surface adhesive is selected from a group consisting of a hot melt adhesive and a web bonded adhesive having a melt flow index range of about 5 to about 500 at melt temperature and about 900 to about 2500 at application temperature. [0016]In accordance with still another aspect of the present invention the reinforcement fabric comprises a surfacing veil, an infusion media layer selected from a group of materials consisting of veil, continuous filament mat, chopped strand mat, direct chopped mat, direct continuous mat, collimated continuous fibers, woven fabric, non-woven fabric, scrim and combinations thereof, a sheet of collimated continuous fibers, a first reinforcing layer of unidirectional fabric extending in a direction about +45 degrees relative to the collimated continuous fibers, a second reinforcing layer of unidirectional fabric extending in a direction about -45 degrees relative to the collimated continuous fibers and a surface adhesive. The surface adhesive is selected from a group consisting of a hot melt adhesive and a web bonded adhesive having a melt flow index range of about 5 to about 500 at melt temperature and about 900 to about 2500 at application temperature. The reinforcement fabric may also include a second sheet of collimated continuous fibers and a surfacing adhesive underlying the second reinforcing layer. [0017]In accordance with yet another aspect of the present invention a reinforcement fabric comprises a surfacing veil, a continuous filament mat, at least one sheet of collimated continuous fibers, a first reinforcing layer of unidirectional fabric extending in a direction of about +45 degrees relative to the collimated continuous fibers, a second reinforcing layer of unidirectional fabric extending in a direction of about '45 degrees relative to the collimated continuous fibers and a surface adhesive selected from a group consisting of a hot melt adhesive and a web bonded adhesive having a melt flow index range of about 5 to about 500 at melt temperature and about 900 to about 2500 at application temperature. The reinforcement fabric further comprises a layer of chopped fibers. In addition the reinforcement fabric may further include at least one additional reinforcing layer underlying the second reinforcing layer. [0018]In the following description there is shown and described several different embodiments of this invention, simply by way of illustration of some of the modes best suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments and its several details are capable of modification in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive. BRIEF DESCRIPTION OF THE DRAWINGS [0019]The accompanying drawings incorporated in and forming a part of the specification, illustrate several aspects of the present invention, and together with the description serve to explain certain principles of the invention. In the drawings: [0020]FIG. 1 is a schematical side elevational view of one possible embodiment of the reinforcement fabric of the present invention; Continue reading... Full patent description for Infusion fabric allowing high resin infusion rates Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Infusion fabric allowing high resin infusion rates 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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