WO2003101719A2

WO2003101719A2 - Polyurethane spread-laminated composites and methods of manufacture

Info

Publication number: WO2003101719A2
Application number: PCT/US2003/017309
Authority: WO
Inventors: Mark Tolan
Original assignee: Alive Surftec
Priority date: 2002-05-31
Filing date: 2003-05-30
Publication date: 2003-12-11
Also published as: WO2003101719A3; AU2003240480A1; AU2003240480A8

Abstract

Laminated composites, such as aquatic sport devices, having a rigid core covered on at least one side by a fiber reinforcing material impregnated with an aromatic or aliphatic polyurethane resin are disclosed. For example, surfboards having such a composite structure are disclosed. Methods are also provided for fabricating laminated composites by spread-lamination, for example by hand spread-coating the fiber reinforcing material with the polyurethane resin and curing the resin such that the reinforcing material and the resin form a laminated layer adhered to the rigid core.

Description

POLYURETHANE SPREAD-LAMINATED COMPOSITES AND METHODS OF MANUFACTURE

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

[0001] This invention relates to polyurethane shaped reinforced composites and their method of manufacture.

DESCRIPTIONOFTHERELATEDART

[0002] Current sail boards, surfboards and similar aquatic sports devices are constructed with a one piece rigid foam or composite core that is coated with a structural adhesive, which is obtained by impregnating, spread-coating or laminating a woven or mat (i.e. non- woven) reinforcing material with a resin, such as a polyester or epoxy resin. Fiberglass fabric is a prime example of a woven reinforcing material used in such a structure.

[0003] There are multiple fabrication techniques used to make such aquatic sports devices. With one technique, a shaped core is first formed, and then covered with an outer protective structural adhesive or resin skin. In this technique, the resin can be used as an adhesive to "glue" a pre-formed mat-reinforced layer to the shaped core. Additionally, shaped upper and lower sections can be joined together to form an aquatic sport device with a generally hollow interior. Each section is formed with a generally sandwich construction including a high strength outer skin, an inner skin spaced from the outer skin, and a core formed from a filler material which is sandwiched between the inner and outer skins. The inner and outer skins are formed, for example, from one or more layers of a cured thermosetting resin that has been impregnated into a fabric material.

[0004] It is also known to use polyurethane structural adhesives to adhere parts fabricated from fiberglass reinforced polyester (FRP) materials. These FRP materials are also commonly referred to as sheet molding compound. Typical commercially available polyurethane structural adhesives are described in U.S. Patent Nos. 3,935,051 and 4,552,934. [0005] In a related procedure, fiberglass mat is formed by treating fiberglass with a water-dispersible, polyurethane-forming binder and curing the binder so formed to obtain a fiberglass mat.

[0006] With another technique, a thermoforming process is used to blow a resin into a mold to form the outer skin of the composite. Reinforcing fibers may be used as fillers or a fabric line the walls of the mold to be impregnated by the resin injected to form a shell. After the shell is formed, a foam is then injected into the hollow of the mold to produce the core. However, the expense of designing and manufacturing molds is considerable. In addition, controlling the uniformity with which the thermosetting resin impregnates the fabric is difficult.

[0007] An alternative procedure that does not require molds is known as "spread-lamination." In spread-lamination, the protective resin-impregnated layer is formed directly on a core. However, the innate problems of this procedure has heretofore limited spread laminations to easily controlled quick set resins such as epoxy, vinyl ester and polyester resins. The common method of laying up such "quick-setting" epoxy, vinyl ester and polyester resins by spread lamination depends on the liquid resins having two properties: a relatively low viscosity and a long, controllable gel time. Typically the amount of catalyst applied to the resin mixture allows the laminator to control the amount of time during which the resin can be worked before it reaches its critical set point of sudden hardening or "goes off. Because the initial catalyzed resin has a low viscosity and the impact strength of these laminating resins after cured are also relatively low, such resins are applied in excess compared to what is needed to fully coat the glass. Application of excess resin provides greater impact resistance and compensates for "drain out," a term used to describe the effect of losing wetness (resin layer thickness or coverage) at areas of lamination that are on a slope. To correct this problem, additional applications of resin are required during the "laying up" period to properly maintain the thickness of the resin before the resin attains its critical set point, at which time the resin suddenly cross-links or gels. Agitation (e.g. hand-working the resin to smooth it ) past the critical gel set point will impair the uniformity of strength and thickness of the laminate. Thus, it is difficult to form a continuous layer of resin of uniform thickness (especially without formation of "air holes") using such quick setting resins for spread lamination, hi addition, excess resin adds inefficient weight to the composite.

[0008] Use of polyurethane resins, which are not quick setting but instead gel by a relatively slow process of spreading crosslinking in the polymer, has heretofore been unknown for spread lamination of aquatic sport devices and other sculpted laminates known in the trade as reinforced composites. Yet use of polyurethane resins would be highly desirable because polyurethanes can be very "tough" or "rugged" (high tensile strength with relatively high flexural strength and elongation) whereas polyester and epoxy resins are brittle, having a relatively low flexural strength and elongation.

[0009] Whatever the mode of manufacture, the core of an aquatic sport device does not always add significantly to its strength, but the weight of the core material contributes significantly to the weight of the finished device. Other factors that determine the weight of the finished device are the number of layers of the reinforcing material contained in the structural adhesive and the depth of the layer of resin skin atop or beneath the mat reinforcing material. In particular, excess weight results if the resin coating is thicker than is needed to just impregnate the mat used to reinforce the composite structure, adhere it to the core, and obtain a reasonably smooth outer surface.

[0010] High performance surfboards and other similar aquatic sports devices, such as paddleboards, sailboards, kayaks, and the like, have flex patterns that are important to their respective performance characteristics.

[0011] Strength in a sports device such as high performance surfboards and other similar aquatic sports devices, such as paddleboards, sailboards, kayaks, and the like depends largely upon the properties of the components— the foam, wood or synthetic/composite core, the reinforcing material (e.g., fiberglass) and the resin coating—and their ability to bond together. In general, however, the resin, which bonds the reinforcing material to the core, is the structural component that imparts strength to the system by dispersing force into the reinforcing material during impact. Also if the resin coating cracks under stress or strain, water can infiltrate the core and destroy the performance of the sports device. And impact of the sports device on the ocean floor or on other solid objects can cause "dings" that impair the appearance and/or functionality of the device.

[0012] It is desirable that the components of the sandwiched composite or sports device be resistant to deterioration by UN light, which tends to cause yellowing of resin coatings and/or cause surface roughening and deterioration of the components, with the result that overall appearance, strength and performance of the product is compromised. Prior-art materials and composites have generally been deficient in UN resistance.

[0013] Thus, there is a need in the art for improved polyurethane laminated composites and for materials and methods for manufacture of polyurethane spread-lamination composites, for aquatic sport devices.

SUMMARY OF THE INVENTION

[0014] The invention solves the above described and other problems in the art by providing improved laminated composites comprising a rigid core having a compressive strength in the range from about 25 psi to about 200 psi, and flexural strength in the range from about 50 psi to 150 psi. At least one layer of a woven or mat reinforcing material is adhered to the core by means of an aromatic or aliphatic polyurethane resin formed by mixing of a two component system having a liquid viscosity in the range from 300 cps to about 2,000 cps and gel time of about of about 3 to 60 minutes after the mixing. The reinforcing material and the polyurethane resin form a laminate layer adhered to the core.

[0015] In another embodiment, the invention provides surfboards comprising a pre- shaped rigid core having a density in the range from about 1 pcf to about 5 pcf; and at least one layer of a woven or mat reinforcing material adhered to the core by an aromatic or aliphatic polyurethane resin formed by mixing of a two component system having a liquid viscosity in the range from 300 cps to about 2,000 cps and a gel time of about of about 3 to 60 minutes after the mixing, such that the reinforcing material and the polyurethane resin form a laminate shell enclosing the core that has a tensile strength of at least 10,000 psi and a flexural strength of at least 50,000 psi. [0016] In yet another embodiment, the invention provides laminated aquatic sports devices comprising a core having a density in the range from about 1 pcf to about 45 pcf. At least one layer of a woven or mat reinforcing material is adhered to the core by an aromatic or aliphatic polyurethane resin formed by mixing of a two component system or equivalent one component system with blocked reactants having a liquid viscosity in the range from 300 cps to about 2,000 cps and a gel time of about of about 3 to 120 minutes after the mixing. The laminated layer has a tensile strength of at least 10,000 psi and a flexural strength of at least 13,000 psi.

[0017] In another embodiment, the invention provides methods for forming a laminated composite by spread-lamination wherein at least one layer of a woven or mat reinforcing material is adhered to at least one surface of a core by spread-coating the material and core simultaneously with a liquid two-component aromatic or aliphatic polyurethane resin formed by mixing of a two-component aromatic or aliphatic polyurethane resin system having a viscosity of about 300 cps to about 2,000 cps and a gel time of about 3 to about 60 minutes after the mixing, and curing the resin such that the reinforcing material and the resin form a laminated layer on the at least one surface.

[0018] In still another embodiment, the invention provides laminated aquatic sport devices formed by adhering at least one layer of a woven or mat reinforcing material to at least one surface of a rigid core in the shape of a desired aquatic sport device by spread- coating the material with a liquid two-component aromatic or aliphatic polyurethane resin formed by mixing of a two-component aromatic or aliphatic polyurethane adhesive system having a viscosity of about 500 cps to about 750 cps when mixed, and curing the resin such that the reinforcing material and the resin form a laminated layer on at least one surface, thereby forming a laminated sport device.

[0019] In yet another embodiment, the invention provides improved surfboards formed by a method comprising adhering at least one layer of a woven or mat reinforcing material to at least one surface of a core by spread-coating the material with a liquid two-component aromatic or aliphatic polyurethane resin formed by mixing of a two-component aromatic or aliphatic polyurethane adhesive system having a viscosity of about 500 cps to about 750 cps when mixed, and curing the resin. [0020] In another embodiment, the invention provides prepregs formed by saturating at least one layer of a woven or mat reinforcing material applied to at least one surface of a rigid core with a liquid two-component aromatic or aliphatic polyurethane resin formed by mixing of a two-component aromatic or aliphatic polyurethane resin system having a viscosity of about 300 cps to about 2,000 cps and a gel time of about 3 to about 60 minutes after the mixing, to form a prepreg, wherein the resin is not allowed to gel, and storing the prepreg under storage conditions that prevent gelling of the resin system.

DETAILED DESCRIPTION OF THE INVENTION

[0021] The invention provides a new approach to the design and manufacture of laminated composites, including aquatic sports devices, boat hulls, and the like.

[0022] In one embodiment according to the invention, there are provided laminated composites comprising a rigid core having a density in the range from about 1 psf to about 45 psf. At least one layer of a woven or mat reinforcing material is adhered to the core by means of an aromatic or aliphatic polyurethane resin formed by mixing of a two component system having a liquid viscosity in the range from 300 cps to about 2,000 cps and a gel time of about of about 3 to 60 minutes after the mixing. The reinforcing material and the polyurethane resin form a laminate layer adhered to the core and may have a tensile strength of at least about 10,000 psi or more and a flexural strength of at least 50,000 psi or more. In some embodiments, the reinforcing material and the polyurethane resin form a laminate shell enclosing the core and the laminate shell has a tensile strength of at least 12,000 psi and a flexural strength of at least 55,000 psi.

[0023] The polyurethane resin system can be selected from any known in the art if so long as upon mixing of the two component system the mixture has a liquid viscosity in the range from 300 cps to about 2,000 cps, for example in the range from about 600 cps to about 700 cps, and a gel time of about 3 minutes to about 8 hours, for example, in the range from about 5 minutes to 20 minutes for systems that are not exposed to vacuum (e.g. vacuum bagged) and 2-3 hours for systems that are exposed to vacuum as described below.

[0024] The resin provides the bonding adhesion of the woven or mat reinforcing material to the core. The ability of this resin to disperse force to the reinforcing material and core during impact is what imparts strength to the composite. Therefore, the greatest flexural, tensile and elongation strengths are generally imparted to the composite by selection of a resin rated as having the greatest flexural, tensile and elongation strength. It is also important that the resin adhere to the reinforcing material and core.

[0025] The components of the two component system include an isocyanate component. The isocyanate component of the resin, for example, can comprise an organic polyisocyanate in which part of the isocyanate groups have been modified by reaction with one or more isocyanate-reactive compounds. Suitable polyisocyanates can include aliphatic and cycloaliphatic polyisocyanates. Such isocyanates include those having the formula:

Q(NCO)_n

in which n is a number from 2 to about 5 (for example 2 to 3) and Q is an aliphatic hydrocarbon group containing 2 to about 18 (for example 6 to 10) carbon atoms, or a cycloaliphatic hydrocarbon group containing 4 to about 15 (for example 6 to 15) carbon atoms. Further examples of suitable polyisocyanates include ethylene diisocyanate; 1,4-tetramefhylene diisocyanate; 1,6-hexamethylene diisocyanate; 1,12-dodecane diisocyanate; cyclobutane-l,3-diisocyanate; cyclohexane-1,3- and -l,4-diisocyanate, and mixtures of these isomers; l-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (see, e.g. German Auslegeschrift 1,202,785 and U.S. Pat. No. 3,401,190), bis (4- isocyanatocyclohexyl methane (Desmodur W), α, , α', α'-tetramethylxylylene diisocyanate

[0026] In one embodiment, substituted and unsubstituted aromatic and/or alicyclic diisocyanates are used in the two component system according to the invention. Suitable aromatic diisocyanates for use according to the invention include, for example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, xylylene diisocyanate, p,p'-diphenylmethane- diisocyanate, p-phenylene diisocyanate, naphthalene diisocyanate, dianisidine diisocyanate, 4,4'-diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, 3,3'-dichloro-4,4'-diphenylmethane diisocyanate; mixtures of one or more of the above, and the like. Suitable alicyclic diisocyanates for use according to the invention include 4,4'-dicyclohexylmethane diisocyanate and hydrogenated xylylene diisocyanate.

[0027] Suitable modified polyisocyanates can be prepared by the reaction of organic polyisocyanates such as described above with one or more compounds containing isocyanate-reactive groups, such as hydroxyl, amino, urethane ureas, carboxyl, biurets, allophanates, thiol groups (for example hydroxyl and/or amino groups) and various blocking groups known in the art and having a functionality about 2 to about 6, such that up to about 10 (for example less than 5) equivalent percent of the isocyanate groups have been modified. In one embodiment, the modified polyisocyanate can have one or more carbon moieties (-CH2-, ≡CH, etc) replaced with a heteroatom (such as N, S, O) as long as the isocyanate and resultant urethane, have a stability comparable to a one not having the substitution.

[0028] A second component of the two component polyurethane system is a polyol or polyol blend. Suitable polyether polyols include polyethers prepared, for example, by the polymerization of epoxides such as ethylene oxide, propylene oxide, butylene oxide, or epichlorohydrin, optionally in the presence of Lewis acids such as BF₃, or prepared by chemical addition of such epoxides, optionally added as mixtures or in sequence, to starting components containing reactive hydrogen atoms, such as water, alcohols, or amines. Examples of starting components include ethylene glycol, 1,3- or 1,2-propanediol, 1,2-, 1,3-, or 1,4-butanediol, trimethylolpropane, pentaerythritol or dipentaerythritol, diethyentriamine, and the like.

[0029] Two component polyurethane systems generally include in one component a catalyst used to promote the urethane chain extension and crosslinking reactions (by reaction of NCO groups with a residual OH group of a diol, or triol, respectively, for example) upon mixing of the two components of the system together. Such catalysts can be selected from tin compounds such as, for example, various stannous carboxylates like stannous acetate, stannous octoate, stannous laurate, stannous oleate and the like, or dialkyl tin salts of carboxylic acids such as dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate, dibutyltin di-2-ethylhexoate, dilauryltin diacetate, dioctyltin diacetate and the like. Similarly, there can be used a trialkyltin hydroxide, dialkyltin oxide or dialkyltin chloride. As an alternative, various tertiary amines can be used, such as triethylamine, triethyanolamine, benzyldimethylamine, triethylenediamine and tetramethylbutanediamine. The tin catalysts, when utilized, are generally used in amounts of 0.5 parts or less, i.e., in the range of about 0.01 to 0.5 parts, by weight per 100 parts of prepolymer. The tertiary amine catalysts, when utilized, can be used in amounts of 0.01 to about 5 parts by weight per 100 parts of prepolymer. However, at least 0.01 part of at least one type of catalyst should be present. Particularly suitable catalysts are organomercury or organic bismuth compounds wherein the organic portion is an aliphatic, for example an alkyl having from 2 to 20 carbon atoms. The amount of such an organomercury catalyst used is generally from about 0.01 to about 1.0 part by weight per 100 parts by weight of the prepolymer.

[0030] If it is desired that the polyurethane resin of the invention have a color or hue, any conventional pigment or dye can be utilized in conventional amounts. Hence, any pigment known to the art and to the literature can be utilized as for example titanium dioxide, iron oxide, carbon black, and the like, as well as various dyes provided that they do not prevent the desired urethane reaction.

[0031] The quantity of isocyanate-reactive amine is selected to be sufficient to produce a viscosity in the range from about 300to about 2000 centipoises when the two components are mixed. For example, about 0.05 to about 10 percent by weight of the isocyanate- reactive amine based on the total quantity of the curative component can be used to achieve a mixture having a resistance to flow in this range.

[0032] Inert powdered fillers, such as clay, talc, asbestos, titanium dioxide, powdered calcium carbonate, whiting, zinc oxide, barytes, basic magnesium carbonate, water insoluble soaps, blanc fixe, aluminate, hydrated alkali silico aluminate and litharge can also be included. Normally the amount of filler may vary from a low of 5 parts to a high of 200 parts, for example being about 50 to 100 parts, per hundred parts of reactive hydrogen containing compound or compounds (e.g. polyols). The amount of filler should be adjusted to yield a mixture having the desired resistance to flow. The exact amount is inversely related to density of the filler. Suitable fillers include silicate-containing minerals, such as antigorite, serpentine, hornblends, amphibiles, chrysotile, talc, mica, and kieselguhr; metal oxides such as kaolin, aluminum oxides, titanium oxides, and iron oxides; metal salts such as chalk and heavy spar (barium sulfate); inorganic pigments such as cadmium sulfide and zinc sulfide; and glass, and the like. Preferred fillers, such as talc, are substantially inert under the conditions encountered when the components of the invention are mixed. Fillers may be used either individually or in admixture. The fillers may be added to either or both components of the two component system in quantities totaling about 10 to about 40 percent by weight based on the total quantity of the filled polyurethane adhesive.

[0033] In addition to the fillers described above, other auxiliary agents and additives may optionally be used in the preparation of the adhesives of the invention. Suitable auxiliary agents and additives may include, for example, additional catalysts for the polyisocyanate-polyaddition reaction, drying agents, surface-active additives, anti-foaming agents, pigments, dyes, UN stabilizers, plasticizers, and fungistatic or bacteriostatic substances, such as those described in European Patent Application 81,701 at column 6, line 40, to column 9, line 31.

[0034] Exemplary core materials suitable for use as the core in the invention composites can be selected from such known materials as polymer foam, ceramics, wood, rubber, metal and the like, that have a density of 1 pcf to about 45 pcf, for example in the range from about 2 pcf to 10 pcf, and a compressive strength in the range from about 25 psi to about 200 psi, for example at least 50 psi to provide rigidity to the composite and compressive and flexural strength.

[0035] When the core is a polymer foam, the polymer foam may be selected from known "rigid" foams having the above described density, such as polyurethane, polyethylene, extruded, expanded polystyrene, polyester, polyisocyanurate and the like. Composites made from an open celled surface foam core, such as is formed when a foam core is carved, sawed or cut to shape, provide the advantage that the polyurethane resin penetrates and/or adheres to the interior of the open cells in the core surface.

[0036] Extruded polystyrene foam, which has been used as the base for construction of boats and surfboards, provides a closed cell foam core, so the core can be water resistant. Polystyrene foam is desirable in applications where water penetration is to be avoided. [0037] Polyurethane foams are particularly suitable for use with polyurethane resins because adherence of the resin to the foam is strong, and may be due in part to cross-linking of the resin to the foam.

[0038] Another type of foam that can be used in formation of laminates according to the invention methods is polyurethane/unsaturated polyester hybrid foam as described in U.S. Patent No. 5,604,266.

[0039] The invention composites are well illustrated by laminated surfboards, but it should be understood that surfboards are only one embodiment or illustration of the invention composites. Invention surfboards comprise a shaped, relatively rigid core having a density in the range from about 1 pcf to about 5 pcf with at least one layer of a woven or mat reinforcing material as is known in the art, such as glass, carbon fiber, nylon, polyester, metal, aramid fibers, such as poly-para-phenylene terephthalamide (aramid) fiber (Kevlar®) and meta-aramid, poly(meta-phenyleneisophthalamide) (Nomex ®), and the like, adhered to the core so as to completely cover the surface of the core by means of an aromatic or aliphatic polyurethane resin having the properties described herein.

[0040] The invention surfboards are designed to undergo elastic shape deflection in the range from about 1% to about 80%, for example at least 10%. In addition, the invention surfboards will have one or more of the following properties: a Shore D hardness in the range from about 25 to about 95, a surface that withstands a compressive stress in the range from about 25 psi to about 80,000 psi, for example as measured by the ASTM C365 Standard Test Method for Flatwise Compressive Properties of Sandwich Cores, but modified as described in Example 2 herein, and a flexural strength in the range from about 50 psi to about 100,000 psi as measured, for example by the ASTM D790 Long Beam Flexural Strength test. Generally, the weight to length ratio of the invention surfboards is in the range from about 0.5 pounds/ft. to about 4 pounds/ft, for example in the range from about 0.5 pounds/ft. to about 2.5 pounds/ft. To achieve different flex properties, the invention surfboards optionally may contain one or more stringers running along the length of the core. A stringer is a ridged material, typically wood, but can be made of any composite known in the art and runs nose to tail. [0041] Polyurethane resin systems used in invention composites and methods are is formed by mixture of a two component system that comprises an aliphatic or aromatic isocyanate prepolymer component containing a polyisocyanate in which part of the isocyanate groups have been modified by reaction with one or more isocyanate-reactive compounds and an aromatic or aliphatic polyol component. Aliphatic polyurethane resins are preferred for producing surfboards and other aquatic sport devices with enhanced UN resistance. Also, aliphatic polyurethane resins cure to form semi-crystalline substance, providing enhanced resistance to cracking and excellent elongation properties. For example, the combination of dicyclohexylmethane-4, 4' diisocyanate and a polyether polyol can be used in such a system. The ratio of isocyanate prepolymer component to polyol component in the two component polyurethane system is advantageously selected in the range from about 100:60 to 1:1 by weight and from about 100:60 to 1:1 by volume.

[0042] Optionally, the polyurethane system can contain one or more solvents, for example, water and water-miscible, low-boiling solvents, for example inert organic solvents including ketones such as methyl ethyl ketone, hydrocarbon solvents, aromatic solvents such as toluene, ethyl acetate, n-methyl pyrrolidone, and the like. Aqueous dispersions which are prepared using such inert organic solvents will contain volatile organic compounds unless such solvents are stripped from the dispersions prior to use. Alternatively, the two component system can be 100% solids (i.e., free from water and other solvents).

[0043] Materials that can be used as the woven or mat reinforcing material in the invention surfboards and other laminated composites include, without limitation thereto, glass, carbon fiber, Kevlar®, Νomex®, nylon, polyester, metal and the like, strand mat, surface mat, nonwoven fabric or Victoria lawn that is composed of a glass fiber, a glass fiber/organic fiber composite, an organic fiber or a carbon fiber to provide strength to the composite and to aid in keeping the thickness of the resin layer uniform. Such reinforcing materials will commonly have a tensile strength in the range of about 10,000 psi to about 70,000 psi, for example from about 12,000 psi to about 50,000 psi, or from about 15,000 psi to about 40,000 psi and a flexural strength in the range from about 50,000 psi to about 90,000 psi, for example from about 55,000 psi to about 75,000 psi, or from about 60,000 psi to about 70,000 psi. The tensile strength and flexural strength of the laminate layer in the aquatic device will be at least as great as that of the woven or mat reinforcing material contained in the laminate layer.

[0044] For surfboards and most aquatic devices, one up to about 20 layers of such a woven or mat reinforcing material can be successfully adhered to the core by the invention methods; however, it should be kept in mind that the weight of the composite is increased as each additional layer is added due to the weight of the additional layers and the weight of the additional resin that is required to fully wet and impregnate multiple layers of the mat or cloth material. For production of boat hulls, additional layers of a woven or mat reinforcing material are used.

[0045] An example of a woven or mat reinforcing material for use in the invention composites is fiberglass, for example fiberglass cloth, in which thin strands of glass are woven together into a fabric. The strands can be coated with a bonding agent as is known in the art to increase adherence of the resin. Pigments are sometimes added to the glass for cosmetic reasons. The strength of fiberglass lies in the weave of the fabric. Depending on the desired characteristics of the composite or surfboard, different weights and weaves of fiberglass are used. The weaves come in some basic categories and are commercially available. E-glass is rated as having the flattest, weakest weave. The fibers lay flat and there is less overlap between fibers, providing a weaker matrix. S-glass is rated as having the strongest, twisted weave. The fibers in S-glass run both horizontally and vertically and the overlap provides a stronger matrix. For example, Hexcell Corporation supplies an E, S, and a directional cloth called RWG, and JPS Company also makes E, S, and a directional cloth called Warp™.

[0046] Another factor to consider in selection of the fiberglass is whether a warp glass would provide more support in a particular area of stress. For a surfboard or other elongated sports device, fiberglass with a higher warp rating means more fibers run from nose to tail rather than rail to rail. A 50/50 fiberglass has equal numbers of fibers per sq inch running from nose to tail as from rail to rail. The overall break strength nose to tail is enhanced by selection of a higher warp nose to tail. [0047] Polyurethane foams are conventionally produced by mixing a polyisocyanate component of at least one diisocyanate or polyisocyanate with a polyol component of at least one polyether polyol or polyester polyol, in the presence of at least one catalyst and at least one propellant and optionally in the presence of various auxiliaries and additives well known in polyurethane chemistry. These additives also optionally include foam stabilizers. The high molecular weight polyol makes up the largest percentage of the foam formulation. The diisocyanate is of lower molecular weight and forms an exceptionally strong cross-link structure with the polyol.

[0048] The properties of the polyurethane foams may be adjusted within wide ranges by use in conjunction with low molecular weight diols as chain extenders or with triols and amines as cross linkers.

[0049] Mainly water, carbon dioxide or halogen alkanes are used as propellants. Selection of the propellant depends, inter alia, on the reaction mixture to be foamed and the required strength as well as further properties of the final formed foam. Besides water, fluorochlorohydrocarbons (FCHC), hydrogen fluorochlorohydrocarbons (HFCHC), hydrogen fluorohydrocarbons (HFHC) or special carbamates in particular, have been used as propellants for the production of harder polyurethane foams. Due to the known ecological problems associated with the said halogen-containing propellants, their use is continuously decreasing in the field of integral foams. However, use of hydrocarbons, such as isomeric pentanes or cyclopentanes, as a propellant involves the risk of easy flammabihty of the substances.

[0050] Tertiary amines and tin organic compounds generally serve as catalysts for producing polyurethane foams. Tertiary amines are conventionally used for the above- mentioned integral foam systems. Co-catalysis by metal catalysts is possible. The foams produced with the aid of amine catalysts have various disadvantages. The amine catalysts remain in the foam, but are not firmly bound there. Thus, in the course of time, and particularly after high-temperature aging, a long-lasting constant odor results. The gradual gaseous emission of amines may also be associated with health stresses to the user. European patent 0 121 850 describes the use of certain carbamates which carry hydroxyl groups as propellants for polyurethane foams and carbamates can also function as propellants.

[0051] A special variant of mold foaming is reaction foam casting, which is also referred to as the Reaction Injection Molding (RIM) process. Flexible to semi-hard moldings are obtained from integral foam, which characteristically has a compact edge zone integrally joined to a light cellular core within a molding made from the same PUR material.

[0052] The density of the foam determines the rigidity of the foam. In the invention composities and methods of their preparation, foam having a density in the range from about 1 pcf to 5 pcf is commonly used. A polyurethane foam having such a density can be prepared by mixing a polyol mixture comprising a polyol, water and a catalyst with a polyisocyanate, and foaming the resulting mixture.

[0053] In another embodiment, the invention provides a unique one step method for forming a laminated composite by spread-lamination in which a woven or mat reinforcing material is adhered to a core or blank in one step without the woven or mat reinforcing material having been preformed into a rigid structural component.

[0054] The invention methods for forming a laminated composite by spread-lamination comprise adhering at least one layer of a woven or mat reinforcing material as described herein to at least one surface of a rigid core by spread-coating the material with a liquid two-component aromatic or aliphatic polyurethane resin formed by mixing of a two-component aromatic or aliphatic polyurethane resin system having a viscosity of about 300 cps to about 2,000 cps, for example a liquid viscosity of about 600 cps to about 700 cps, or about 650 cps, and a gel time of about 3 to about 60 minutes after the mixing, for example about 12 minutes to about 20 minutes, or about 14 minutes after the mixing is desirable. The procedure for spread-coating comprises rapidly working the resin on the material so as to thoroughly wet the material and surface of the core; removing excess resin prior to gelling of the resin, applying pressure to the gelled resin to create a uniform continuous layer; and curing the resin.

[0055] A molded core or a raw blank of core material cut and shaped to desired dimensions is used as the rigid core for the sport device. For example, the core material can be a closed cell foam blank that is cut and/or shaped to desired dimensions. A fiberglass cloth is cut to fit the shape of the core and spread evenly, but loosely on the surface of the core. The fiberglass cloth is not preformed into stiffened panels. The two component polyurethane resin system is mixed (in the presence of a catalyst, if needed) and then, when needed and if necessary, put in a vacuum chamber to remove any air bubbles created in the resin during mixing. The mixed and bubble-free resin is poured without delay over the surface of the reinforcing materials, such as a fiberglass cloth. Alternatively, a sprayer can be used to apply the liquid resin to the surface of the reinforcing material. The liquid resin is then rapidly spread over the surface of the reinforcing material so as to accomplish thorough wetting of the fiberglass or other mat or woven material. In one embodiment of the invention methods, the spreading is performed by hand using an instrument, such as a squeegee, having an edge or surface that can be used to push the resin through the fiberglass and into open cells of the core (to form the "cherry coating"). Alternatively, a comparable mechanical action can be used to spread the resin over the fiberglass and apply pressure to push the resin through the fiberglass and into contact with the underlying core.

[0056] Once the fiberglass is wet, if excess resin has been applied it can now be removed from the surface of the forming composite during the gradual cross-linking of the polymer and prior to gelling of the resin to achieve a uniform layer of resin having a minimum thickness. If it is desired to maximize the strength to weight ratio of the composite, the layer of resin should be no deeper than the thickness needed to just impregnate and cover the surface of the woven or mat reinforcing material. To achieve a heavier laminate, the resin coating atop the reinforcing material can be thicker. As the resin advances toward the gel point, pressure can be applied to the laminate to smooth out any inconsistencies in uniformity (i.e., without formation of air pockets where the underlying fiberglass weave is exposed) (During application of pressure to the gelled resin, it is possible to push the resin into open cells of an open-celled core.

[0057] It is recommended to allow the resin to cure at room temp before application of heat to minimize shrinkage and distortion. In order to reach full cure the resin must be baked at an elevated temperature, although the temp cannot be raised past a level that would inhibit the strength of the core material. Generally heat curing is in the range from about 37.7 ° C to 82 °C for a period of about 3 to about 48 hours. Curing may optionally comprise applying a vacuum to the surface of the gelled resin to create mechanical pressure on the laminate during its cure cycle. Pressurizing the laminate serves one or more of the following functions: removing air trapped between layers of the laminate, compacting the fiber layers for efficient force transmission among fiber bundles and preventing shifting of fiber orientation during curing, reducing humidity. Most importantly, pressuring the laminate before and/or during cure optimizes the fiber-to-resin ratio in the composite. Pressurizing can be accomplished in a vacuum chamber or by placing the composite in a vacuum bag as is known in the art to hold the system in place through the gel stage and, if desired, into the full cure. The negative pressure commonly applied for vacuum curing is about -30 mmHg, or approximately one atmosphere of negative pressure. The application of vacuum during curing does not alter the gel time or the method for spread-coating of the reinforcing material with the resin system as described herein..

[0058] If desired, the invention methods can further comprise coating the composite with a sanding coat of resin, for example, filing the edges from the composite and applying a sanding coat of the urethane resin (a "hot coat") in which a wax surfacing agent is added to make the composite easier to sand. The composite can further be sanded to a smooth surface. For example, commercially available 3M sand papers can be used starting with a high grit grade and progressing to a low grit grade. After sanding, the surface can be polished and/or further waxed and buffed to impart a shine to the surface.

[0059] The invention methods for spread-lamination manufacture of composites and aquatic sports devices are designed to overcome many problems that are not encountered when urethane resins or other branching polymer resins are used in molding of composites. For example, in mold technology, the viscosity and thickness of the layer of resin applied are not critical issues. Pressurizing the mold is a proven way of controlling the results for most applications when urethane polymers are used in molds.

[0060] However, the expense of designing and manufacturing molds is avoided in the invention methods. This is particularly advantageous when laminating fiberglass to large surfaces or surfaces with changing curvatures (i.e. concavities), such as aquatic sports devices. In manufacture of such objects, feasibility of molds drops considerably. Spread lamination is usually is the procedure of next choice; however, the innate problems of the design and curing properties of branching resins have limited spread laminations to easily controlled quick set resins such as epoxy, vinyl ester and polyester resins.

[0061] The prior art methods of laying up such "quick-setting" epoxy, vinyl ester and polyester resins by spread lamination depends on the liquid resins having two properties: the liquids must have a relatively low viscosity and a long controllable gel time. Typically the amount of catalyst applied to the resin mixture allows the laminator to control the amount of time in which the resin can be worked before it reaches its critical set point of sudden hardening or "goes off. Because viscosity is low and the flexural strength of the laminating resins is relatively low, resin is applied in excess proportionately to what is needed to properly reinforce the glass. Application of excess resin provides greater impact resistance and compensates for "drain out" a term used to describe the effect of losing wetness / resin coverage at areas of lamination that are on a slope. However, this excess resin adds inefficient weight to the composite.

[0062] In spread-lamination using "quick setting" epoxy, vinyl ester and polyester resins, timing is very important, the goal being to get everything perfect just before the resin "goes off." Although the relatively low viscosity of resins used in the prior art spread-lamination methods allows for ease of wetting the fiberglass, once the fiberglass is wet, the system typically does not maintain uniformity due to the long gel time allowing for drain out of the resin at areas of slope. To correct this problem, additional coatings of resin are required during the "laying up" period to properly maintain the thickness of the resin before the resin attains its critical set point, at which time the resin suddenly cross-links. Agitation past the critical gel set point in the prior art methods will impair the uniformity of strength and thickness of lamination.

[0063] By contrast, the invention methods for urethane spread-lamination do not rely on relatively low viscosity resins and long gel times for the system to "lay out" (become uniform in thickness due to low viscosity and forces of gravity). This makes the wetting of the glass more difficult but provides the advantage that drain out is avoided during the prolonged gelling. Although urethane resins have been considered difficult or impossible to utilize in spread lamination techniques (e.g., hand-lamination) because progressive cross- linking between molecules provides resistance to spreading of the resin, a technique for spread lamination of polyurethane resins has been long sought and is highly desirable because the highly-cross linked urethane resins provide superior physical characteristics. Accordingly, the invention provides laminates with increased weight to strength properties as well as superior impact resistance and flexibility. The already high viscosity of the resin mixture has excellent sag resistance during spread lamination, which allows the laminator to focus on maximizing the resin coverage while using the least amount of resin, rather than focusing on compensating for drain out as in the prior art methods. This change in focus calls for the laminator to achieve wetting of the cloth as soon as possible after mixing of the resin so that as the resin cures, the developing matrix of chemical bonds and polymerized chains maximizes support the reinforcing material. This has shown to be a benefit in strength and overall quality of lamination. We have discovered that if the cloth is rapidly wet using either spray application or squeegees, the long chain/crosslinking framework that is created as the resin cures around the lay of the fibers provides superior support of the reinforcing material, while using a minimum amount of resin.

[0064] Due to the increased sag resistance in polyurethane resins that develops during the gel time, once the resin has wet the glass, the laminator then has time to add resin to fix problem areas, such as air bubbles, twists in the glass, the lay of the fabric, areas needing extra resin support, and the like and/or apply the appropriate pressure with the squeegee to draw out any excess resin. Although polyurethane resins do not reach a point at which the resin suddenly "goes off, due to increased cross-linking of the resin, a point is reached at which further spreading or pressure will have no effect on the resin. Consequently, it is important to have achieved the desired thickness and spread of the resin prior to this point.

[0065] The invention technique of quick wetting and then drawing off the maximum amount of resin does not work in methods of spread-lamination employing quick-setting resins, such as epoxy, vinyl ester and polyester resins, because the low viscosity of the liquid resin will cause "airing out", a term that refers to formation of areas in which there is not enough resin coverage around the fibers, thus creating pockets of air within the weave. Although thickeners can be added to epoxy, vinyl ester and polyester resins to increase their sag resistance, such thickeners pose additional problems in quick setting resins. Addition of thickeners prevents the resin from properly laying out (achieving a uniform thickness by gravity) and at the same time prevent the laminator from drawing off excess resin during the gel time, because the resin still needs a settling time to properly cross-link. Thickeners in such quick setting resins also sacrifice the ability to easily wet the glass. Ease of wetting the glass / low viscosity in common laminations are very important in order for the laminator to properly get the system ready for the gel set stage.

[0066] In addition, if more than one lamination step is desired, in the invention methods, no preparatory work is required between laminations in order to facilitate bonding. The ease of applying multiple layers of spread lamination, one at a time, is an advantage not provided by prior art methods of spread lamination.

[0067] Furthermore, the invention composites are readily sanded once cured due to the high shear strength and tensile strength of urethane resins, especially if the resin has been cured at a temperature of at least 130 °C.

[0068] When repairs are needed and additional urethane resin is not available or easy to apply, blemishes on the surface of the invention sport device can be repaired using non- urethane resins, such as the quick setting resins, without difficulty. A sealing coat of a quick-setting resin can be used to fill any porosity or flaw in the urethane lamination. In addition, a cosmetic look can be achieved that is not possible with urethane resin by applying a top cosmetic coat of a non-urethane resin. Because the quick-setting resins are less expensive than urethane resins, sealing the urethane laminated composite with a quick setting resin can effect a cost savings. Compatibility of the urethane composite with these less expensive and rapidly curing resins is a great advantage.

[0069] The invention methods are particularly well suited for manufacture of aquatic sport devices and other laminated objects having sculpted contours. For example, in addition to surfboards, which are merely illustrative in the description of the invention, body boards, kayaks, paddleborards, sailboards, and the like, can be made using the invention methods for spread lamination with polyurethane resins.

In still another embodiment, the invention provides prepregs comprising one or more layers of mat or woven reinforcing material that has been s saturated with a urethane resin as described herein and stored at storage conditions that prevent gelling of the resin system. The urethane resin can be hand spread, for example using a hand squeegee to press the surface of the reinforcing material flush with the core (so no air pockets remain) or a roller machine can be used to apply pressure to the surface to assure that the reinforcing material is thoroughly saturated. By either method, the resin is worked into the reinforcing material so as to thoroughly wet the material and surface of the core, removing excess resin, and applying pressure to the resin to create a uniform continuous layer, but the resin is not allowed to gel.

[0070] If the resin contains a catalyst of a type does not require oven heating or UN light for curing and thus cures at room temperature, the prepreg is stored at a lowered temperature to delay the gelling of the urethane resin. The longer the desired shelf-life of the prepreg, the lower the storage temperature. The average temperature of prepreg storage to prevent gelling is in the range from about -18 °C to about 5 °C. If the resin system is of the type that is activated by UN light, the storage conditions comprise the absence of UN light.

[0071] When a core used in production of an invention laminate composite contains a steep angle or an angle past the vertical, application of an invention prepreg to the core followed by application of vacuum to the composite during the gel stage, and optionally, during curing of the resin, is advantageous. However there is usually an extra material cost involved in using this method.

[0072] The invention is illustrated by the following non-limiting examples.

EXAMPLE 1

ASTM D-628 - Test of Tensile Properties

[0073] Tensile properties of two types of sample laminates were performed in accordance with ASTM D638 using the type IN configuration. Properties obtained were Ultimate Stress, Modulus and Ultimate Strain. Tests were performed at 73 °F and 50% relative humidity. Sample A was made of 23 layers of 4 ounce E type fiberglass ( Hexell Corporation, , Seguine, TX) impregnated with an epoxy resin (Type 2100, Resins Research Epoxy Systems, Indialantic FL) having 2 parts resin to one part hardener and cured according to manufacturer's instructions. The samples were .479 inch in width and 0.164- 0.169 inch in thickness. Sample Type 2 was made of 23 layers of the fiberglass of Type A, but impregnated with a two component polyurethane resin system of 4, 4'-dicyclohexyl diisocyantate and polyether polyol catalyzed by an organomercury catalyst (WC 184, BJB Enterprises, Bloomington, CA) cured according to manufacturer's instructions. The samples were .488-.490 inch in width and 0.166-0.196 inch in thickness.

[0074] Sample Type 2 was made of 23 layers of the fiberglass of Type A, but impregnated with a two component polyurethane resin system of 4, 4'-dicyclohexyl diisocyantate and polyether polyol catalyzed by an organomercury catalyst (WC 184, BJB Enterprises) cured according to manufacturer's instructions. The samples were .488-.490 inch in width and 0.166-0.196 inch in thickness.

[0075] The results of the tensile tests are summarized below in Table 1.

Table 1

EXAMPLE 2

Compression Testing Of Full Composites

[0076] Ball Deformation of the sandwich panel was performed per ASTM C365 Standard Test Method for Flatwise Compressive Properties of Sandwich Cores, except that a 1-1/2" steel ball was placed on top of the sandwich panel to exert the compressive force, rather than a flat steel member. A load was applied through a United Loadframe at a constant rate of travel of 0.05" per minute. The point at which the initial load dropped was recorded as failure.

[0077] Various sample blocks with the dimensions 6" (length) x 6 " (width) x 3" (depth) were tested with the force applied to the center of the 6" x 6" sides (SI), which were formed of a laminated layer (layer A) of 2 plies of 4 oz E fiberglass (Hexcel Corporation) that covered only the plane of that surface. The layer on top of layer A (layer B) covered the same area but also wrapped down the sides of the block, which each had a dimension 3" x 6".

[0078] Sample 3 : The fiberglass layers were laid up by hand with epoxy resin (Formula 2100, 2 parts resin 1 part hardener by volume (Resin Research Epoxy Systems,) using the techniques known in the art for quick setting resins and as described herein. The laminate surface of layer A was coated again after gelling with a second layer of the same (un- reinforced) epoxy resin. The core material was 2 pcf extruded polystyrene foam (Dow Chemical, (Dow Chemical, Midland, Michigan

[0079] Sample 4: The fiberglass layers were laid up by hand with Ortho polyester resin (Somar 249 catalyzed with MEKP - 925, Norox, Azusa CA) using the techniques known in the art for quick setting resins and as described herein. The laminate surface of layer A was coated again after gelling with a second layer of the same (un-reinforced) polyester resin, with a common over the counter paraffin wax dissolved in styrene as a surfacing agent. The core material used was 2 pcf open cell polyurethane foam (Clark Foam, Westminster, CA).

[0080] Sample 5: The fiberglass layers were reinforced and adhered in the same step with aliphatic urethane resin (WC- 784, 1:88 by volume (BJB Enterprises). The laminate surface of layer A was coated again after gelling with a second layer of the same (un- reinforced) aliphatic urethane resin. The core material was 2 pcf extruded polystyrene foam (Dow Chemical).

[0081] Sample 6 was the same as Sample 5, except that the core material used was 2 pcf open cell polyurethane foam (Clark Foam). [0082] The results of the compression testing of full composites are summarized below in Table 2.

Table 2

EXAMPLE 3

Testing of Overall Flexural Strength And Maximum Yield Of Full Composite

[0083] Long Beam Flexural Strength testing was performed per ASTM D790 and per ASTM C393 using both a three-point and four-point reaction setup. In both setups the bottom span was set to 32-inches. The four-point test used a Vi-span setup where the span of the top was set to 16", yielding an 8" reaction distance. The 3 -point setup had a single point at mid-span yielding a 16" reaction distance. Ultimate load and plots of the load vs. deflection were generated for all tests.

[0084] Various composites samples with the dimensions 3.5' (length) x 4 " (width) x 1" (depth) were tested with the force applied to the surfaces of the 3.5' x 4" sides (SI & S2), which were formed of a laminated layer (Layer A) of 2 plies of 4oz E fiberglass (Hexcel Corporation) which covered only the plane of that surface. The layer on top of layer A (layer B) covered the same area but also wrapped down the sides of the block with the dimensions 3.5' x 1".

[0085] Sample 7: The fiberglass layers were laid up by hand with epoxy resin (Formula 2100, 2 parts resin 1 part hardener by volume (Resin Research Epoxy Systems), using the techniques the techniques known in the art for quick setting resins and as described herein. The laminate surface of layer A was coated again after gelling with a second layer (layer B) of the same (un-reinforced) epoxy resin. The core material was 2 pcf extruded polystyrene foam (Dow Chemical).

[0086] Sample 8: The fiberglass layers were laid up by hand with Ortho polyester resin (Somar 249 catalyzed with MEKP - 925 produced by Norox) using the techniques known in the art for quick setting resins and as described herein. The laminate surface of layer A was coated again after gelling with a second layer (layer B) of the same (un-reinforced) polyester resin, with a common over the counter paraffin wax dissolved in styrene as a surfacing agent. The core material used was 2 pcf open cell polyurethane foam (Clark Foam).

[0087] Sample 9: The fiberglass layers were reinforced and adhered in the same step with aliphatic urethane resin (WC- 784, 1 :88 by volume, BJB Enterprises). The laminate surface of layer A was coated again after gelling with a second layer (layer B) of the same (un-reinforced) aliphatic urethane resin. The core material was 2 pcf extruded polystyrene foam (Dow Chemical).

[0088] Sample 10 was the same as Sample 9, except that the core material used was 2 pcf open cell polyurethane foam Clark foam.

[0089] The results of the testing of full composites for flexural strength and maximum yield are summarized below in Table 3.

Table 3

EXAMPLE 4 Impact properties of composite

[0090] Impact resistance testing was performed using a 1-1/2" diameter steel ball weighing 0.5 pounds that was dropped from various heights. Up to 20-drops were made at adjusted heights. Pass and Fail observations were made visually. Any form of "spider webbing" constituted a failure. A table was generated showing the foot-pounds of force generated and a pass or fail was recorded for each impact. The data was analyzed per ASTM D5420 and the threshold level for pass/fail was calculated.

[0091] Various composite samples with the dimensions 3.5' (length) x 4 " (width) x 1" (depth) were tested with the force applied to the surfaces of the 3.5' x 4" sides (SI & S2), which had had a laminated layer (Layer A) of 2 plies of 4 oz E fiberglass (Hexcel Corporation), which covered only the plane of that surface. The layer on top of layer A (layer B) covered the same area but also wrapped down the sides of the block with the dimensions 3.5' x 1". [0092] Sample 11 : The fiberglass layers were laid up by hand with epoxy resin (Formula 2100, 2 parts resin 1 part hardener by volume (Resin Research Epoxy Systems), using the techniques known in the art for quick setting resins and as described herein. The laminate surface of layer A was coated again after gelling with a second layer (Layer B) of the same (un-reinforced) epoxy resin. The core material was 2 pcf extruded polystyrene foam (Dow Chemical).

[0093] Sample 12: The fiberglass layers were laid up by hand with Ortho polyester resin (Somar 249 catalyzed with MEKP - 925) (Norox) using the techniques known in the art for quick setting resins and as described herein. The laminate surface of layer A was coated again after gelling with a second layer (layer B) of the same (un-reinforced) polyester resin, with a common over the counter paraffin wax dissolved in styrene as a surfacing agent. The core material used was 2 pcf open cell polyurethane foam (Clark Foam).

[0094] Sample 13: The fiberglass layers were reinforced and adhered in the same step with aliphatic urethane resin (WC- 784, 1:88 by volume (BJB Enterprises). The laminate surface of layer A was coated again after gelling with a second layer (layer B) of the same (un-reinforced) aliphatic urethane resin. The core material used was 2 pcf open cell polyurethane foam (Clark Foam).

[0095] Sample 14: The fiberglass layers were reinforced and adhered in the same step with aliphatic urethane resin (WC- 784, 1 :88 by volume, made by BJB enterprises). The laminate surface of layer A was coated again after gelling with a second layer (layer B) of the same (un-reinforced) aliphatic urethane resin (WC- 784, 1 :88 by volume (BJB Enterprises). The core material used was 2 pcf open cell polyurethane foam (Clark Foam).

[0096] Sample 15was the same as Sample 14, except that the core material was 2 pcf extruded polystyrene foam (Dow Chemical).

[0097] Results of the impact tests are summarized in Table 4 below. Table 4

[0098] Numerous modifications and variations of the invention are possible in light of the above teachings and, therefore, within the scope of the appended claims, the invention may be practiced otherwise than as particularly described.

Claims

WHAT IS CLAIMED IS:

1. A laminated composite comprising: a rigid core having a compressive strength in the range from about 25 psi to about 200 psi, and at least one layer of a woven or non- woven fiber reinforcing material adhered to the core by means of an aromatic or aliphatic polyurethane resin to, said polyurethane resin being formed by mixing of a two component system and having a liquid viscosity at the mixing temperature in the range from 300 cps to about 2,000 cps and a gel time of about of about 3 to 60 minutes after the mixing, wherein the reinforcing material and the polyurethane resin form a laminate layer adhered to the core.

2. The composite of claim 1 wherein the laminate layer has a tensile strength of at least about 10,000 psi and a flexural strength of at least 50,000 psi.

3. The composite of claim 1 wherein the reinforcing material and the polyurethane resin form a laminate shell enclosing the core and the laminate shell has a tensile strength of at least 12,000 psi and a flexural strength of at least 55,000 psi.

4. The composite of claim 1 wherein the laminate layer has an Izod impact of at least 1.0 ft.-lb/in.

5. The composite of claim 1 wherein the two component system comprises an aliphatic or aromatic isocyanate prepolymer component comprising a polyisocyanate in which part of the isocyanate groups have been modified by reaction with one or more isocyanate-reactive compounds and an aromatic or aliphatic polyol component.

6. The composite of claim 5, wherein the organic polyisocyanate is dicyclohexylmethane-4, 4' -diisocyanate.

7. The composite of claim 5, wherein the polyol is polyether polyol.

8. The composite of claim 5, wherein the ratio of isocyanate prepolymer component to polyol component in the two component system is in the range from about 100:70 to 1:1 by weight and from about 100:70 to 1:1 by volume.

9. The composite of claim 1, wherein the core is selected from polymer foam, wood, rubber and metal with a density of 1 pcf to 45 pcf.

10. The composite of claim 9, wherein the core is a polymer foam selected from polyurethane, polyethylene, extruded polystyrene and expanded polystyrene.

11. The composite of claim 10 wherein the polymer foam core has open cells at the surface thereof.

12. The composite of claim 10, wherein the polymer foam is polyurethane.

13. The composite of claim 1, wherein the gel time is in the range from about 12 minutes to about 16 minutes.

14. The composite of claim 1, wherein the viscosity is in the range from about 600 cps to about 700 cps.

15. A surfboard comprising: a pre-shaped rigid core having a density in the range from about 1 pcf to about 5 pcf; and at least one layer of a woven or mat reinforcing material adhered to the core by an aromatic or aliphatic polyurethane resin, said resin being formed by mixing of a two component system having a liquid viscosity in the range from 300 cps to about 2,000 cps and a gel time of about of about 3 to 60 minutes after the mixing, wherein the reinforcing material and the polyurethane resin form a laminate shell enclosing the core, said laminate shell having a tensile strength of at least 10,000 psi and a flexural strength of at least 50,000 psi.

16. The surfboard of claim 15 wherein the laminate shell has an Izod impact of at least 1.0 ft.-lb/in.

17. The surfboard of claim 15, wherein the two component system comprises an aliphatic or aromatic isocyanate prepolymer component comprising an organic polyisocyanate in which part of the isocyanate groups have been modified by reaction with one or more isocyanate-reactive compounds and an aromatic or aliphatic polyol component.

18. The surfboard of claim 17, wherein the organic polyisocyanate is dicyclohexylmethane-4, 4' diisocyanate.

19. The surfboard of claim 17, wherein the polyol is a polyether polyol.

20. The surfboard of claim 15, wherein the woven or non- woven fibrous material is selected from glass, carbon fiber, aramid fiber, and nylon.

21. The surfboard of claim 15, wherein the core is a polymer foam selected from polyurethane, polyethylene, extruded polystyrene and expanded polystyrene.

22. The surfboard of claim 21 wherein the polymer foam core has open cells at the surface thereof.

23. The surfboard of claim 22, wherein the polymer foam is polyurethane.

24. A surfboard of claim 15, wherein the surfboard undergoes elastic shape deflection in the range from about 1% to about 80%.

25. A surfboard of claim 24, wherein the elastic shape deflection is at least 10%.

26. The surfboard of claim 15, wherein the two component system is 100% solids.

27. The surfboard of claim 15, wherein the gel time is in the range from about 12 minutes to about 16 minutes.

28. The surfboard of claim 15, wherein the viscosity is in the range from about 600 cps to about 700 cps.

29. The surfboard of claim 15, wherein the laminate shell has a Shore D hardness in the range from about 25 to about 95.

30. The surfboard of claim 15, wherein the laminate shell withstands a compressive stress of at least 25 psi.

31. The surfboard of claim 15, wherein the weight to length ratio is in the range from about 0.5 pounds/ft. to about 4 pounds/ft.

32. The surfboard of claim 31 , wherein the weight to length ratio is in the range from about 0.5 pounds/ft. to about 2 pounds/ft.

33. The surfboard of claim 15, further comprising one or more stringers running along the length of the core.

34. A method for forming a laminated composite by spread-lamination, said method comprising: adhering at least one layer of a woven or mat reinforcing material to at least one surface of a rigid core by spread-coating the material with a liquid two-component aromatic or aliphatic polyurethane resin formed by mixing of a two-component aromatic or aliphatic polyurethane resin system having a viscosity of about 300 cps to about 2,000 cps and a gel time of about 3 to about 60 minutes after the mixing, and curing the resin such that the reinforcing material and the resin form a laminated layer on the at least one surface, thereby forming a laminated composite.

35. The method of claim 34, wherein the spread-coating comprises: working the resin on the material so as to thoroughly wet the material and surface of the core, removing excess resin prior to gelling of the resin, and applying pressure to the gelled resin to create a uniform continuous layer; and

36. The method of claim 34, wherein the two component aromatic or aliphatic polyurethane adhesive comprises an isocyanate prepolymer component containing an aromatic or aliphatic polyisocyanate in which part of the isocyanate groups have been modified by reaction with one or more isocyanate-reactive compounds and an aliphatic polyol component.

37. The method of claim 34, wherein the two-component aromatic or aliphatic polyurethane resin has a viscosity of about 600 cps to about 700 cps.

38. The method of claim 34, wherein the two component resin has a gel time of about 12 minutes to about 20 minutes after the mixing.

39. The method of claim 34, wherein the reinforcing material is selected from glass, carbon fiber, aramid fiber, and nylon.

40. The method of claim 34, wherein the core is selected from polymer foam, wood, rubber and metal with a density of 1 pcf to 5 pcf.

41. The method of claim 40, wherein the core has a compressive strength of at least 25 psi and a flexural strength of at least 50 psi.

42. The method of claim 34, wherein the spread-coating is performed by hand.

43. The method of claim 34, wherein the material is fiberglass cloth.

44. The method of claim 34, wherein the pressure is applied to the gelled resin by hand.

45. The method of claim 44, wherein the pressure is applied to the gelled resin by repeatedly drawing an instrument over the surface of the gelled resin.

46. The method of claim 45, wherein the pressure is applied by a squeegee held at an angle to the surface of the gelled resin.

47. The method of claim 46, wherein a squeegee is used to remove the excess resin.

48. The method of claim 34, wherein the spread-coating is by mechanical dispensing device.

49. The method of claim 48, wherein the mechanical dispensing device is a sprayer.

50. The method of claim 49, wherein the mechanical dispensing device is a mechanical spreader.

51. The method of claim 34, wherein the curing comprises heat curing the sport device at a temperature of about 37.7 ° C to 82 °C.

52. The method of claim 51 , wherein the curing is for a period of about 3 to about 48 hours.

53. The method of claim 35, wherein the pressure application comprises applying a vacuum to the surface of the gelled resin.

54. The method of claim 53, wherein the composite is placed in a bag for application of the vacuum to the surface of the gelled resin.

55. The method of claim 35, wherein the method further comprises sanding the cured resin coating.

56. The method of claim 42, wherein from one to ten layers of the fiberglass cloth are applied.

57. A laminated aquatic sport device, said sport device being formed by a method comprising: adhering at least one layer of a woven or mat reinforcing material to at least one surface of a rigid core in the shape of a desired aquatic sport device by spread-coating the material with a liquid two-component aromatic or aliphatic polyurethane resin formed by mixing of a two-component aromatic or aliphatic polyurethane adhesive system having a viscosity of about 500 cps to about 750 cps when mixed, and curing the resin such that the reinforcing material and the resin form a laminated layer on at least one surface, thereby forming a laminated sport device.

58. The sport device of claim 57, wherein the spread-coating comprises: working the resin on the material so as to thoroughly wet the material and surface of the core, removing excess resin prior to gelling of the resin, and applying pressure to the gelled resin to create a uniform continuous layer.

59. The sport device of claim 57, wherein the cured resin and the reinforcing material form a laminated layer having a compressive strength of at least 25 psi and a flexural strength of at least 20,000 psi.

60. The sport device of claim 57 wherem the two component system comprises an aliphatic or aromatic isocyanate prepolymer component comprising an organic polyisocyanate in which part of the isocyanate groups have been modified by reaction with one or more isocyanate-reactive compounds and an aromatic or aliphatic polyol component.

61. The sport device of claim 60, wherein the organic polyisocyanate is dicyclohexylmethane-4, 4' -diisocyanate.

62. The sport device of claim 60, wherein the polyol is polyether polyol.

63. The sport device of claim 60, wherein the core is selected from polymer foam, wood, rubber and metal with a density of 1 pcf to 5 pcf and a compressive strength of at least 25 psi and a flexural strength of at least 50 psi.

64. The method of claim 57, wherein the resin is spread-coated by hand.

65. The method of claim 57, wherein the material is fiberglass cloth.

66. The method of claim 57, wherein the pressure is applied to the gelled resin by hand.

67. The method of claim 66, wherein the pressure is applied to the gelled resin by repeatedly drawing an instrument over the surface of the gelled resin.

68. The method of claim 66, wherein the pressure is applied by a squeegee held at an angle to the surface of the gelled resin.

69. The method of claim 66, wherein a squeegee is used to remove the excess resin.

70. The method of claim 57, wherein the resin is applied to the material by a mechanical dispensing device.

71. The method of claim 70, wherein the mechanical dispensing device is a sprayer.

72. The method of claim 57, wherein the spread-coating is by a mechanical spreader.

73. The method of claim 57, wherein the curing comprises heat curing the sport device to a temperature of about 37.7 ° C to 82 °C.

74. The method of claim 73 wherein the curing is for a period of about 3 to about 48 hours.

75. The method of claim 57, wherein the curing comprises applying a vacuum to the surface of the gelled resin.

76. The method of claim 75, wherein the device is placed in a bag for application of the vacuum to the surface of the gelled resin.

77. The method of claim 57, wherein the sport device is a boat hull.

78. The method of claim 57, wherein the sport device is a body board.

79. The method of claim 57, wherein the sport device is a kayak.

80. The method of claim 57, wherein the sport device is a paddleboard.

81. The method of claim 57, wherein the sport device is a sailboard.

82. The method of claim 57, wherein the sport device is a surfboard.

83. A prepreg formed by a method comprising: saturating at least one layer of a woven or mat reinforcing material applied to at least one surface of a rigid core with a liquid two-component aromatic or aliphatic polyurethane resin formed by mixing of a two-component aromatic or aliphatic polyurethane resin system having a viscosity of about 300 cps to about 2,000 cps and a gel time of about 3 to about 60 minutes after the mixing, to form a prepreg, wherein the resin is not allowed to gel, and storing the prepreg under storage conditions that prevent gelling of the resin system.

84. The prepreg of claim 83, wherein the resin system cures at room temperature and the storage conditions comprise a temperature in the range from about -18 °C to about 5 °C.

85. The prepreg of claim 83, wherein the resin system cures with UV light and the storage conditions comprise the absence of UV light. working the resin on the reinforcing material so as to thoroughly wet the material and surface of the core, removing excess resin, and applying pressure to the resin to create a uniform continuous layer.