Self-adhesive prepreg

Abstract

A self-adhesive prepreg comprising a fiber reinforced layer having a first side and a second side, the first side of the fiber reinforced layer being pre-impregnated with a self-adhesive resin composition. The self-adhesive prepreg may be used as a structural reinforcement and is particularly suited for direct bonding to oily or oily galvanized steel in the automotive, aerospace and other sheet metal manufacturing industries.

Description

Technical Field

[0001] The present invention relates to a self - adhesive prepreg, a process for preparing a self - adhesive prepreg, the use of a self - adhesive prepreg as a structural reinforcement, a method for structurally reinforcing an article using a self - adhesive prepreg, and a structurally reinforced article obtained by such a method. The present invention particularly relates to the use of a self - adhesive prepreg that exhibits good bonding properties to oil - coated steel or oil - coated galvanized steel as a structural reinforcement in the automotive industry, aerospace industry, wind turbines, and other sheet metal manufacturing industries.

Background Art

[0002] Prepreg is a term used to describe fibers and / or fabrics (textiles) pre - impregnated with an uncured and cure - ready resin. The fibers can be in the form of tows or fabrics. Tows or fabrics generally contain a plurality of fine fibers, commonly referred to as filaments. The fiber material may be in the form of a plurality of fiber tows, each containing a plurality of fiber filaments for forming each tow. The tows may be stitched or woven to form a fabric. The selection of the fiber reinforcement and resin in the prepreg varies depending on the application for which the composite material formed from the cured prepreg will be used and the properties required for that application.

[0003] Composite materials are widely used in the automotive, aerospace, construction industries including the wind turbine industry, and other sheet metal manufacturing industries. The methods by which such composite materials are used vary according to the particular application concerned, which in the automotive industry includes use as lightweight rigid body panels, engine bays, exhaust ducts, and fuel system components; in the aerospace industry includes use as engine blades, brackets, interiors, nacelles, propellers or rotors, single aisle wings, and wide body wings; in the construction industry includes use as load-bearing panels and infill panels, pressure pipes, tank liners, and roofs; or in the wind turbine industry includes use as rotor blades and nacelles, among others. Some of the initial uses have been documented in detail. For example, the use of soybean fibers in the production of phenolic resin composites for plastic automotive prototypes by Ford Motor Company (Detroit, Michigan, United States of America) in the early 1940s, or the use of flax in the production of flax-reinforced composite fuselages for single-seat fighter aircraft such as the Supermarine Spitfire by Aero Research Limited (Duxford, Cambridgeshire, United Kingdom) in the mid-1940s.

[0004] Composite materials for some applications can be manufactured in-situ at the intended location from the relevant fiber reinforcement and resin matrix. However, this approach has a number of problems such as the reproducibility of the manufacturing process and the homogeneity of the resulting composite material. In particular, since air bubbles cannot be sufficiently removed from the mixture of the fiber reinforcement and the resin matrix, variations can occur in the desired physical properties of the final composite material. These problems have been largely overcome by the use of prepregs. Prepregs can be manufactured off-site by specialized manufacturers in a highly uniform and consistent manner. Such prepregs are generally supplied sandwiched between two layers of backing to prevent the prepregs from sticking together. The backing layer can be easily removed at the intended location. The prepregs can be laid up (constructed) using a manual or automated layup process in a mold, or in a tool, or in a vacuum bag before being subjected to the final curing process which generally involves the application of heat and pressure.

[0005] Some degree of residual tack of the prepreg is usually desirable to ensure that the prepreg remains fully functional. For example, such a degree of residual tack of the prepreg is desirable to take on a complex mold shape when manually laid up, or to continue to adhere to adjacent prepregs laid up successively (sequentially) in multiple layers or stacks for the purpose of making the structural rigidity of the cured composite material even greater. The residual tack of the prepreg varies depending on the composition of the resin matrix, and there is often a trade-off between the tack of the prepreg and the flexibility or "drape" of the prepreg that enables it to be formed inside the mold. Japanese Patent Laid-Open No. 09-194612 discloses, for example, a prepreg containing reinforcing fibers and a matrix resin, having an adhesiveness T of 0.025 MPa or more and a drapability D of 150 GPa or less. In this document, the adhesiveness T is defined as the peel strength after pressing a 50×50 mm prepreg sample under a load of 0.11 MPa, and the drapability D is defined as the flexural modulus of the prepreg measured by a three-point bending test.

[0006] For certain applications, a prepreg that can be directly adhered to the substrate before curing is required. This eliminates the need for a release film for the applied adhesive. The use of self - adhesive prepregs as surface thin layers or skin sheets for the purpose of joining to a honeycomb core to form sandwich panels that can be used in various applications (such as aircraft floor panels) that require a combination of high structural rigidity and light weight is well - known. European Patent No. 0798102, for example, discloses a sandwich structure having a honeycomb and / or foam core material and an outer layer. This core material is based on a resin - impregnated fiber carrier material and is connected to the outer layer using a cured self - adhesive prepreg. The prepreg includes a core layer of a fiber carrier material and an auxiliary fiber material that forms a surface layer. The fiber carrier material of the core layer is characterized in that it has a greater weight per unit area than the auxiliary fiber material. The weight ratio of resin to fiber material in the surface layer is characterized in that it is higher than the weight ratio in the core layer. The fiber material structure of the fiber carrier material and the auxiliary fiber material is characterized in that it is impregnated with a thermosetting resin and the resin is converted to the B - stage.

[0007] For sandwich panels, multiple approaches to increasing the strength of bonding a self - adhesive prepreg skin sheet to a honeycomb core focus on forming thermosetting or thermoplastic fillets that extend from the self - adhesive surface of the skin sheet into the tubular structures of the honeycomb core during curing. International Publication No. WO 2005 / 113652, for example, discloses a prepreg composition composed of fibers and a prepreg resin, which includes a thermosetting resin, a curing agent, and a plurality of thermoplastic polymers, wherein more than 10% of each thermoplastic polymer is soluble in the prepreg resin. The resulting prepreg composition is used as a self - adhesive prepreg for creating honeycomb structures useful for various applications. This document teaches, contrary to expectations, that the inclusion of thermoplastic polymers as reinforcing agents that are partially or fully soluble in the prepreg resin further results in the formation of plastic fillets that assist in bonding the prepreg to the honeycomb structure during curing. European Patent No. EP 1303570 discloses a resin composition used in combination with fibers to form a self - adhesive prepreg sheet applied to a core material for forming a sandwich panel. The prepreg resin includes a thermosetting resin, a curing agent, and a viscosity modifier. The prepreg resin further includes specific thermoplastic particles, such as densified particles of polyether sulfone or polyetherimide, which are used to control the formation of fillets and the flow characteristics of the prepreg resin while bonding the prepreg to the core material.

[0008] International Publication No. WO 2018 / 174217 teaches that, based on fillet formation, bonding a self - adhesive prepreg skin sheet to a honeycomb core in a sandwich panel results in insufficient peel strength of the skin sheet bonded to the core. This document discloses a method for improving the bonding of a self - adhesive prepreg skin sheet to a honeycomb core, including increasing the drapeability of the skin sheet onto the core by laminating a self - adhesive prepreg containing a non - woven fabric impregnated with a second thermosetting resin onto a base prepreg containing a fiber - reinforced material impregnated with a first thermosetting resin.

[0009] Various approaches to fabricating sandwich panels using a self - adhesive prepreg as the above - mentioned skin sheet are beset with certain disadvantages. For example, as an example of such a disadvantage, there may be a need to include a thermoplastic polymer in addition to a thermosetting polymer as a resin component, or a need to use additional non - woven fiber or fabric layers in the prepreg, which may require additional industrial process steps. Further, the aforementioned approach and many other approaches in this field relate to certain problems in bonding the prepreg to a honeycomb core to form a sandwich panel that is widely used as an aircraft floor panel. Other applications where self - adhesive prepregs have found utility include, for example, an adhesive prepreg strip for manufacturing a copper - clad laminate for printed circuit board manufacturing, as disclosed in Chinese Patent No. 202688253(U), or, for example, something that insulates structural components in the manufacture of an electric motor for use in an automobile, as disclosed in JP - A - 2010 - 155877. However, prepregs are widely used in many different applications in the automotive, wind turbine, construction, and other sheet metal manufacturing industries. Such applications often require a prepreg that is bonded to oil - coated steel or oil - coated galvanized steel as a structural component or reinforcement layer, but such prepregs may be exposed to adverse or extreme weather conditions over a long period. Also, traditional methodologies generally require the use of a structural adhesive to bond such parts or layers to a substrate.

Summary of the Invention

[0010] The present invention aims to overcome some of the above problems and / or generally bring about improvements.

[0011] In accordance with the present invention, there is provided a prepreg, use, process, stack, method, and article as described hereinafter or as defined in any one of the appended claims.

[0012] Accordingly, in a first aspect of the present invention, a prepreg is provided that includes a fiber-reinforced layer having a first side and a second side, wherein the first side of the fiber-reinforced layer is pre-impregnated with a self-adhesive resin composition. Self-adhesiveness in this context refers to a resin composition that is adapted to adhere to a metal substrate that provides desirable adhesion properties at ambient temperature.

Mode for Carrying Out the Invention

[0013] The fiber-reinforced layer includes a fiber material that can be in the form of a sheet or a continuous mat or continuous filaments. In other embodiments, the fiber-reinforced layer may include natural fibers or staple fibers that are short. The fiber material may be in the form of a plurality of fiber tows, each containing a plurality of fiber filaments for forming each tow. The tows may be sewn or woven to form a fabric. The fiber-reinforced layer has a first side and a second side. In one embodiment, the fiber-reinforced layer is substantially flat, and the first side and the second side of this layer are defined by the upper surface and the bottom surface of the plane containing the fiber reinforcement. In other embodiments, the fiber-reinforced layer is curved, and the first side and the second side of this layer are defined by its curved upper surface and bottom surface. In a further embodiment, the fiber-reinforced layer has an irregular surface having flat regions and curved regions. The layer may be relatively thin and may have a relatively narrow edge (edge: end). In some embodiments, the layer of fiber-reinforcing material has a thickness of 100 μm, 200 μm, 300 μm, 400 μm, or 500 μm. In other cases, the fiber-reinforced layer may be relatively thick and may have a relatively wide edge. In some embodiments, the layer of fiber-reinforcing material has a thickness of 500 μm or more, 600 μm or more, 700 μm or more, 800 μm or more, 900 μm or more, or 1000 μm or more. In a particular embodiment, at least one of the first side or the second side of the fiber-reinforced layer is defined by the edge of the layer. In one embodiment, the fiber-reinforced layer is flat and relatively thick, the first side is defined by the surface of the plane containing the fiber-reinforced layer, and the second side is defined by the plane containing the edge of the fiber-reinforced layer. Here, the two planes are orthogonal to each other. In other embodiments, neither the fiber-reinforced layer nor the first side and the second side are defined by a geometrically regular surface.

[0014] The fibers can be made of natural materials such as cotton, linen, hemp, wool, silk, glass fibers, carbon fibers, mineral fibers, etc., semi-synthetic materials such as rayon, viscose, modal, etc., or synthetic materials such as carbon, polyester, nylon, acrylic, synthetic glass, etc. In some embodiments, the fiber reinforcement includes carbon fibers or glass fibers.

[0015] In one embodiment, the fiber reinforcement is in the form of a non-woven fiber material such as a veil or a discontinuous fiber fleece. Suitable glass and carbon veils or metal-coated carbon veils are commercially available under the trade name Optiveil from Technical Fibre Products Limited (Burnside Mills, Kendal, Cumbria, United Kingdom).

[0016] In another embodiment, the fiber reinforcement is in the form of a fabric. In this embodiment, the warp and weft of the fabric may be formed from fiber tows or fiber filaments. In other embodiments, the fiber reinforcement is in the form of a non-woven fabric or non-woven mat. In this form, instead of a conventional weaving process, non-structural sewing threads such as polyester threads are used to avoid inconsistencies, and two or more layers of fiber tows are joined together. The fiber tows or filaments in adjacent layers may be in different spatial orientations with respect to each other, such as a fabric consisting of two layers of unidirectional fiber tows where the fiber tows of the first layer are at an angle of -45° and the fiber tows of the second layer are at an angle of +45° with respect to the forward axis in two two-dimensional planes containing both layers. Such non-woven fabrics may be biaxial or multiaxial depending on the number of layers of fiber tows at different angles. By using sewing instead of weaving to hold the layers of fiber tows together, the drapeability of the resulting non-woven fabric is improved, thereby reducing the tendency for the formed fabric and prepreg to shrink from it, i.e., to form grooves or undulations, when laid up in a mold. Therefore, this type of designed fabric is often called a non-crimp fabric (NCF).

[0017] Suitable woven and non-woven fabrics for use in composite materials are commercially available from many specialized manufacturers, including Chomarat Textiles Industries (Esher, Surrey, United Kingdom), Hexcel Reinforcements UK Limited (Narborough, Leicestershire, United Kingdom), and Zhenshi Group Hengshi Fibreglass Fabrics Co., Ltd. (Tongxiang Economic Development Zone, Jiaxing Zhejiang, 314500 China). In one embodiment, the fabric is a biaxial non-woven fabric of carbon or glass fibers such as BB200, BB600 or BB1200.

[0018] Hybrid or mixed fiber systems may also be envisioned. The use of cracked (i.e., strain-to-failure) or selectively discontinuous fibers can be advantageous in facilitating the layup of products according to the present invention and improving its ability to be molded.

[0019] The surface mass of the fibers in the fiber reinforcement is generally in the range of 80 - 4000 g / m 2 . In some embodiments, the surface mass of the fibers is in the range of 100 - 2500 g / m 2 , 150 - 2000 g / m 2 , 150 - 1200 g / m 2 , 200 - 1200 g / m 2 , 200 - 600 g / m 2 , or 200 - 400 g / m 2 , or in the range of any combination thereof. The number of carbon filaments can vary from 3000 to 320,000, and preferably can vary from 6,000 to 24,000. Fibers with a linear density of 600 - 2400 tex are particularly suitable for glass fiber reinforcements.

[0020] The fibers may be used in a unidirectional form or as a nonwoven mat, fabric, multi-axial fabric or non-crimp fabric. Combinations of these reinforcing forms may also be utilized.

[0021] The self-adhesive resin composition, and, if present, the second resin composition, may be loaded onto the fiber reinforcement in an amount such that the resin loading is in the range of 20 to 90% by weight, based on the total weight of the resin and fiber reinforcement present in the prepreg. In some embodiments, the fiber reinforcement is in the form of a veil or a fleece of discontinuous fibers, and the resin loading is in the range of 20 to 90% by weight, 30 to 90% by weight, 40 to 90% by weight, or 50 to 90% by weight, based on the total weight of the resin and fiber reinforcement present in the prepreg, or in the range of any combination thereof. In other embodiments, the fiber reinforcement is in the form of a fabric, nonwoven or non-crimp fabric or mat, and the resin filling is in the range of 20 to 90% by weight, 20 to 80% by weight, 20 to 70% by weight, 20 to 60% by weight, 20 to 50% by weight, or 30 to 50% by weight, based on the total weight of the resin and fiber reinforcement, or in the range of any combination thereof.

[0022] For certain applications, the reinforcement may act as a support for the self-adhesive resin composition and as providing other functional or structural advantages. The reinforcement may act not only as a support for the self-adhesive resin composition but also as for controlling the thickness of the adhesive layer such that the self-adhesive resin composition is surely present with an optimum minimum bond line thickness between the two surfaces being joined.

[0023] The fiber reinforcement layer may also improve the flow of the adhesive composition during curing of the self-adhesive resin composition and / or it may improve handling.

[0024] In the foregoing embodiments, it is important that the reinforcement, regardless of whether its form is a veil, fleece, fabric, or otherwise, should not interfere to a significant extent with the adhesion properties of the self-adhesive resin composition.

[0025] In a first aspect of the present invention, the first side of the fiber-reinforced layer is pre-impregnated with a self-adhesive resin composition. In one embodiment, only the first side of the fiber-reinforced layer is pre-impregnated with the resin composition, so that the second side of the fiber-reinforced layer is not impregnated and the prepreg is a semi-prepreg. In a further embodiment, the second side of the fiber-reinforced layer is pre-impregnated with the same self-adhesive resin composition as the first side so that the prepreg is symmetric. In another embodiment, the second side of the fiber-reinforced layer is pre-impregnated with a second resin composition having different properties from the self-adhesive resin composition so that the prepreg is asymmetric. Depending on the particular application in which the prepreg is used, the second resin composition may be an adhesive composition having different properties from a self-adhesive resin composition, such as a low-adhesion adhesive composition, for example. In other cases, the second resin composition may be a conventional prepreg resin matrix and / or may be substantially or completely non-adhesive. In one embodiment, the second resin composition is substantially non-adhesive and the self-adhesive resin composition can be joined to the second resin composition when a plurality of prepregs are continuously laid up to form a stack of prepregs. In a final embodiment of the present invention, the use of a second resin composition having a simpler formulation for impregnating the second side of the fiber-reinforced layer can reduce the amount of self-adhesive resin composition required to form a prepreg or stack of prepregs that can play a role in reducing the cost of the overall industrial process. Examples of the second resin composition may include an internal release agent that promotes the removal of the article from the mold after curing.

[0026] The self - adhesive resin composition used in the present invention exhibits good lap - shear strength and good adhesion to oil - coated steel or oil - coated galvanized steel even at ambient temperature and elevated temperatures, and even in the situation of not containing nitrile rubber as a reinforcing agent. However, by including such nitrile rubber and / or core - shell rubber as a reinforcing agent in the composition, other advantages can be brought about, such as increasing the resistance to crack formation. In one embodiment, the self - adhesive resin composition has a lap - shear strength (double - shear strength) of steel - to - steel or galvanized - steel - to - galvanized - steel that is at least 20 MPa at ambient temperature. The lap - shear strength of steel - to - steel can be measured in accordance with BS EN2243 - 1:2005 available from the British Standards Institution (389 Chiswick High Road, London, W4 4AL, United Kingdom), or ISO 204:2009 and / or ISO 527 - 2:2012 available from the ISO Central Secretariat (Chemin de Blandonnet 8, CP 401 - 1214, Vernier, Geneva, Switzerland), which is the International Organization for Standardization. In a further embodiment, the self - adhesive resin composition has a lap - shear strength of steel - to - steel or galvanized - steel - to - galvanized - steel in the range of 20 - 40 MPa, 22 - 35 MPa, 25 - 35 MPa, or 25 - 30 MPa, or any combination thereof.

[0027] The self-adhesive resin composition exhibits good peel strength when tested at ambient temperature at an aluminum-aluminum joint during curing. The peel strength value of aluminum against aluminum can be measured in accordance with BS EN2243-2:2005, which is available from the British Standards Institution (389 Chiswick High Road, London W4 4AL, United Kingdom). In one embodiment, the self-adhesive resin composition has a peel strength of at least 80 N / 25 mm at ambient temperature. In other embodiments, the self-adhesive resin composition has a peel strength in the range of 80 - 250 N / 25 mm, 85 - 230 N / 25 mm, 90 - 180 N / 25 mm, 95 - 150 N / 25 mm, or 100 - 130 N / 25 mm, or any combination thereof.

[0028] In another embodiment, the cured self-adhesive resin composition has an initial cure Tg (peak loss modulus, E’’Tg) of 70 - 160 °C. The cure Tg is measured in accordance with ASTM D7028-7(2015) (Standard Test Method for Glass Transition Temperature (DMA Tg) of Polymer Matrix Composites by Dynamic Mechanical Analysis (DMA)), which can be obtained from ASTM International (100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, Pennsylvania, 19428-2959, USA). The Tg in the wet state or the retained Tg after hot wet aging is measured by isothermally curing an uncured, raw adhesive composition at 150 °C for 15 minutes, exposing the cured composition to water at 70 °C for 14 days, and then measuring the Tg of the sample using the same measurement standard, ASTM D7028. The retained Tg is expressed as a percentage of (Tg in the wet state / initial cure Tg) × 100.

[0029] In a further embodiment, the self-adhesive resin composition has an initial curing Tg in any one of the ranges of 80 to 150 °C, 90 to 145 °C, or 100 to 140 °C, or in the range of any combination thereof. In one embodiment, the self-adhesive resin composition has an E’’Tg retention of at least 70%, preferably at least 75%, preferably at least 80% after hot wet aging at 70 °C for 14 days.

[0030] The self-adhesive resin composition used in the present invention can be cured under conditions that do not require heating at an elevated temperature for a long period of time. In one embodiment, the self-adhesive resin composition is cured by heating at a temperature of 140 °C to 170 °C within 60 minutes.

[0031] The components of the self-adhesive composition used in the present invention will be described in detail below. For example, such a composition may include a one-part or one-component (1K) epoxy resin system that already contains a curing agent so that no additional components are required for the composition to be cured. Generally speaking, 95% curing defines an epoxy resin-containing composition in which enough reaction sites have been consumed such that the mechanical properties and heat resistance of the cured composition are within the desirable property ranges for that composition, in order to bring about the desirable mechanical and chemical performance characteristics. It is possible to expend additional time and additional energy to obtain the final 5% of curing, but this will not lead to a significant improvement in mechanical properties or thermal properties. Differential scanning calorimetry (DSC) is utilized to monitor the time to reach 95% curing. To measure the degree of curing using digital scanning calorimetry, the heat released during the curing reaction is correlated with the total heat for complete curing. This can be measured as follows. A reference resin sample is heated from 10°C to 250°C at a rate of 10°C / min to complete curing (100%), and the heat generated ΔHi is recorded. At this time, the degree of curing of a specific resin sample having the same composition as the reference resin sample can be measured by heating the sample under the conditions of a desired temperature, a desired rate, and for a desired time to cure the sample under these conditions and measuring the heat ΔHe generated by this curing reaction. At this time, the degree of curing (curing %) is Curing % = [(ΔHi - ΔHe) / ΔHi] × 100 [%] (where ΔHi is the heat generated by heating the uncured resin from 10°C to 250°C until complete curing, and ΔHe is the heat generated by the resin cured to a specific degree that has been heated to the desired temperature at the desired rate.) is defined by

[0032] In one embodiment, the self - adhesive resin composition is cured to 95% by heating at a temperature of 140°C to 170°C within 60 minutes, preferably within 45 minutes. In a further embodiment, the adhesive composition is cured to 95% at a temperature of 150°C to 160°C within 20 minutes, or at a temperature of 160°C to 170°C within 10 minutes, or in any combination thereof. The adhesive composition may be cured at a temperature of approximately 170°C within 5 minutes, preferably within 2.5 minutes. In other embodiments, the adhesive resin composition can be cured by heating the composition within 150 seconds up to 150°C, preferably within 120 seconds. This can be desirable in applications where the self - adhesive prepreg according to the present invention is intended to be used to obtain structural reinforcement, and it is important that the prepreg be adhered to and cured on the substrate in - situ as quickly as possible.

[0033] The self-adhesive resin composition may contain a corrosion inhibitor. This is particularly desirable when the fiber-reinforced layer contains carbon fibers or other conductive fibers that may promote the corrosion process. This is particularly desirable in applications where a prepreg or a structure reinforced with a prepreg according to the invention may be exposed to an element. The corrosion inhibitor may include, for example, in particular, molybdenum salts which are salts containing molybdenum oxoanions, calcium nitrite, rare earth metal salts, zinc phosphate or other metal phosphates, in particular chromium salts such as chromates, or inorganic corrosion inhibitors such as lanthanoid compounds. In some applications, the self-adhesive prepreg according to the invention can be adhered to an oil-coated steel or oil-coated galvanized steel structure that may be exposed to adverse or extreme weather conditions, for example in a wind turbine. In one embodiment, the corrosion inhibitor is an inorganic corrosion inhibitor that does not contain chromates or other chromium salts. This is due to the risk that such salts will leach out over time and contaminate the environment. In another embodiment, the corrosion inhibitor is an inorganic phosphate or polyphosphate. Suitable inorganic phosphates or polyphosphates include Heucophos® ZPA (zinc aluminum orthophosphate), Heucophos® ZMP (basic zinc molybdate orthophosphate hydrate), Heucophos® CMP (calcium phosphate complex modified with an electrochemically active magnesium compound), Heucophos® ZAPP (zinc aluminum polyphosphate hydrate), Heucophos® SAPP (strontium aluminum polyphosphate hydrate), Heucophos® SRPP, Heucophos® CAPP, Heucophos® ZAM Plus and Heucophos® ZCP Plus, which are commercially available from Heubach GmbH (Langelsheim, Germany). In one embodiment, the inorganic corrosion inhibitor is strontium aluminum polyphosphate hydrate.

[0034] The corrosion inhibitor may include an organic corrosion inhibitor. Effective organic corrosion inhibitor compounds generally contain heteroatoms with lone pairs of electrons such as nitrogen, oxygen, sulfur, and phosphorus, as well as structural moieties with π electrons that interact favorably with metals in the absorption process. Compounds containing nitrogen may include amines, pyridine derivatives, quaternary ammonium salts, triazole derivatives, Schiff bases, amino acids, and indazoles. Compounds containing nitrogen and sulfur atoms may include imidazole derivatives, thiadiazole derivatives, and thiazole derivatives. Compounds containing sulfur may include thiourea derivatives and sulfonates. Compounds containing nitrogen and oxygen may include oxazole derivatives, phthalimide, and plant extracts / natural extracts. Non-limiting examples of some of the aforementioned classes of organic compounds include 2-(4-nitrophenyl)benzimidazole, (6-methyl-3-oxopyridazin-2-yl)acetate, Schiff base, L-cysteine, imidazoline isomers, N-decyl-3-amino-1,2,4-triazole, and adenosine. The corrosion inhibitor may be a metal salt of an organic compound. One suitable compound is zinc-5-nitroisophthalate. This is commercially available from Heubach GmbH (Langelsheim, Germany) under the trade name Heucorin® RZ. In one embodiment, the corrosion inhibitor includes an inorganic corrosion inhibitor combined with an organic corrosion inhibitor. The inorganic corrosion inhibitor and the organic corrosion inhibitor can provide a synergistic effect with respect to the suppression or reduction of the corrosion process. In one embodiment, the corrosion inhibitor includes a combination of zinc-5-nitroisophthalate and strontium aluminum polyphosphate hydrate.

[0035] The corrosion inhibitor can be present in the self-adhesive resin composition in an amount of 0.05 to 10% by weight, preferably in an amount of 0.5 to 2% by weight based on the total weight of the composition. When an inorganic corrosion inhibitor is used in combination with an organic corrosion inhibitor, the inorganic corrosion inhibitor can be present in an amount of 0.5 to 2% by weight based on the total weight of this composition, and the organic corrosion inhibitor can be present in an amount of 0.01 to 0.5% by weight. The effectiveness of corrosion prevention was evaluated by a salt spray corrosion test.

[0036] The self-adhesive resin composition in the present invention may contain any suitable polymerizable component generally used in adhesives for one-part or one-component structures, including anaerobic adhesives. In particular, for example, those based on polyfunctional methacrylate monomers such as dimethacrylate and trimethacrylate, epoxy adhesives, reactive acrylic adhesives, especially those based on monofunctional acrylate or methacrylate monomers, ultraviolet (UV) light-curable adhesives, especially those based on vinyl ether, vinyl ether ester, urethane vinyl ether and alicyclic epoxy, polyurethanes, reactive hot melt polyurethanes (RHMU), cyanoacrylates, and reactive polysulfones including polysulfone / polyethersulfone (PES), especially aminophenyl-functional reactive polysulfones. The self-adhesive resin composition based on an epoxy resin system is particularly preferred in the present invention considering the flexibility of such systems and the wide range of properties that can be obtained, especially when the prepreg is asymmetric and contains a second resin composition in addition to the self-adhesive resin composition.

[0037] In one embodiment, the self-adhesive resin composition, by the total weight of the composition, (a) 1 to 45% aromatic epoxy resin; (b) 5 to 60% novolac epoxy resin; (c) 1 to 10% curing agent; and optionally (d) 0.05 to 10% corrosion inhibitor.

[0038] In the last embodiment of the present invention, the self-adhesive resin composition contains, as will be described hereinafter, (a) at least one aromatic epoxy resin, and in addition (b) at least one novolac epoxy resin. Components (a), (b), and (c) together form a one-component epoxy resin system that has been catalyzed. The aromatic epoxy resin referred to herein, when present, is an epoxy resin containing at least one aromatic unit in the main chain or side chain. Typically, the aromatic epoxy resin contains at least one aromatic epoxide moiety such as, for example, glycidyl ether, and when present, preferably contains this at the terminal position of the main chain or side chain of the resin. Examples of aromatic epoxy resins that can be used include reaction products of phenol (phenol and formaldehyde) and epichlorohydrin, peracid epoxies, glycidyl esters, glycidyl ethers, reaction products of epichlorohydrin and aminophenol, reaction products of epichlorohydrin and glyoxal tetraphenol, and the like. Examples of the phenol referred to above include polynuclear phenols (i.e., compounds having at least two phenolic functional groups). A typical example of a polynuclear phenol is bisphenol.

[0039] The aromatic epoxy resin can be in solid form or semi-solid form, or a blend thereof. Suitable epoxy resins may include a blend of two or more epoxy resins selected from monofunctional epoxy resins, difunctional epoxy resins, trifunctional epoxy resins, and / or tetrafunctional epoxy resins. Examples of suitable difunctional epoxy resins include those based on bisphenol F, bisphenol A (optionally brominated), phenol, aromatic glycidylamine, naphthalene, or any combination thereof.

[0040] Suitable solid or semi-solid aromatic epoxy resins are commercially available under the trade name Araldite® from Huntsman Advanced Materials (Switzerland) (S.A., Monthey, Switzerland). Suitable high molecular weight basic solid epoxy resins include Araldite® GT 6097, Araldite® GT 6099, Araldite® GT 6609, Araldite® GT 6610, Araldite® GT 6810-1, Araldite® GT 7077, and Araldite® GT 16099. Suitable medium to low weight basic solid epoxy resins include Araldite® GT 6063, Araldite® GT 6063, Araldite® GT 6064, Araldite® GT 6071, Araldite® GT 6084-2, Araldite® GT 6703, Araldite® GT 7004, Araldite® GT 7071, and Araldite® GT 7072. Suitable semi-solid basic epoxy resins include Araldite® GY 280 and Araldite® LY1589. Both are available from Huntsman Advanced Materials, and Epokukdo YD-134 and Epokukdo YD-136 are commercially available from Kukdo Chemical Company Limited (Seoul, South Korea). However, aromatic epoxy resins are not limited to those mentioned above and include other solid and semi-solid basic epoxy resins commonly used as epoxy adhesives. These are commercially available from many manufacturers and producers.

[0041] The aromatic epoxy resin is a silane compound represented by the following Chemical Formula 1

Chemical Formula

[0042] In Chemical Formula 1, R is an aliphatic or aromatic alkylene group, and R 1 , R 2 and R 3 are each independently an aliphatic alkyl group or an aromatic alkyl group. The use of the silane-modified epoxy resin prepared from the compound of Chemical Formula 1 is described in European Patent No. 2799509, and this related disclosure is incorporated herein by reference. Examples of the silane-modified epoxy resin suitable for use in the present invention may include KSR-176, KSR-177, KSR-276, KSR-900, etc. These are commercially available from Kukdo Chemical Company Limited (Seoul, South Korea).

[0043] In one embodiment, the silane-modified epoxy resin is a bifunctional epoxy resin. For example, the epoxy resin may be a silane-modified epoxy resin based on diglycidyl ether of bisphenol A or bisphenol F. In a further embodiment, the silane-modified epoxy resin is a polyfunctional epoxy resin. The higher functionality provided by the bifunctional or polyfunctional silane-modified epoxy resin may be useful for improving the performance of the adhesive composition for specific applications.

[0044] In a further embodiment, the silane-modified epoxy resin is an alkoxysilane-modified epoxy resin or an aryloxyalkoxysilane-modified epoxy resin. For example, in Chemical Formula 1, R may be selected from the group consisting of C 1 ~C 20 alkylene group, arylene group, arylalkylene group, and alkylarylene group, and R 1 , R 2 and R 3 may each independently be selected from the group consisting of C 1 ~C 20 alkyl group, aryl group, arylalkyl group, and alkylarylene group.

[0045] The silane-modified epoxy resin can have an epoxy equivalent weight (EEW) of 170 to 1,000 grams / equivalent (g / eq). Preferably, the silane-modified epoxy resin has an EEW of 170 to 700 g / eq. In some embodiments, the silane-modified epoxy resin has an EEW in the range of 190 to 220 g / eq, 240 to 270 g / eq, 450 to 500 g / eq, or 600 to 700 g / eq, or any combination thereof.

[0046] The silane-modified epoxy resin may be present in an amount of 1 to 15% by weight based on the total weight of the composition. In some embodiments, the silane-modified epoxy resin is present in an amount of 3 to 12% by weight, 4 to 10% by weight, 4 to 8% by weight, or 5 to 7.5% by weight, or any combination thereof, based on the total weight of the composition.

[0047] The inventors have found that a self-adhesive resin composition containing a silane-modified epoxy resin provides good lap shear strength (peel shear strength) and good adhesion to oil-coated steel or oil-coated galvanized steel at room temperature and elevated temperatures, even in the absence of nitrile rubber as a reinforcing agent. The self-adhesive resin composition also has a desired glass transition temperature (peak loss modulus, E’’Tg), which indicates good retention of E’’Tg after hot wet aging.

[0048] The self-adhesive resin composition used in the present invention includes at least one novolak epoxy resin. The novolak epoxy resin may be a phenol novolak epoxy resin, a cresol novolak epoxy resin, a bisphenol A novolak epoxy resin, or a dicyclopentadiene novolak epoxy resin, or any combination thereof. Examples of suitable novolak epoxy resins include YDPN-631 (phenol novolak epoxy resin), YDPN-638 (phenol novolak epoxy resin), YDCN-500-1P (cresol novolak epoxy resin), YDCN-500-4P (cresol novolak epoxy resin), YDCN-500-5P (cresol novolak epoxy resin), YDCN-500-8P (cresol novolak epoxy resin), YDCN-500-10P (cresol novolak epoxy resin), YDCN-500-80P (cresol novolak epoxy resin), YDCN-500-90P (cresol novolak epoxy resin), KBPN-110 (bisphenol A (BPA) novolak epoxy resin), KBPN-115 (BPA novolak epoxy resin), KBPN-120 (BPA novolak epoxy resin), KDMN-1065, KDCP-130 (dicyclopentadiene (DCPD) epoxy resin), KDCP-150 (dicyclopentadiene (DCPD) novolak epoxy resin), and KDCP-130EK80, manufactured by Kukdo Chemical Company Limited (Seoul, South Korea); XD1000 (DCPD novolak epoxy resin) available from Nippon Kayaku Co., Ltd. (Tokyo, Japan); and SCT-150 (phenol novolak epoxy resin) manufactured by Shin-A T&C (Seoul, South Korea), but are not limited thereto. In one embodiment, the novolak epoxy resin is a phenol novolak epoxy resin or a dicyclopentadiene epoxy resin.

[0049] The novolak epoxy resin may generally be present in an amount of 5 to 60% by weight, based on the total weight of the composition. In some embodiments, the novolak epoxy resin may be present in an amount in the range of 5 to 55%, 6 to 50%, 7 to 45%, or 8 to 45% by weight, based on the total weight of the composition, or in any combination thereof. In a composition containing a phenol novolak epoxy resin or a cresol novolak epoxy resin, the phenol novolak epoxy resin or the cresol novolak epoxy resin may be present in an amount of 5 to 20% by weight, based on the total weight of the composition. In some embodiments, the phenol novolak epoxy resin or the cresol novolak epoxy resin may be present in an amount in the range of 5 to 18%, 6 to 16%, 8 to 14%, or 10 to 12% by weight, based on the total weight of the composition, or in any combination thereof. In a composition containing a dicyclopentadiene novolak epoxy resin, the dicyclopentadiene novolak epoxy resin may be present in an amount of 5 to 60% by weight, based on the total weight of the composition. In some embodiments, the dicyclopentadiene novolak epoxy resin may be present in an amount in the range of 5 to 55%, 10 to 50%, 15 to 45%, or 20 to 45% by weight, based on the total weight of the composition, or in any combination thereof.

[0050] The reactivity of the epoxy resin is indicated by its epoxy equivalent weight (EEW), and the lower the EEW, the higher the reactivity. The epoxy equivalent weight can be calculated as follows: (molecular weight of the epoxy resin) / (number of epoxy groups per molecule). Alternatively, it can be calculated using the epoxy value, which can be defined as follows: epoxy value = 100 / epoxy equivalent weight. To calculate the number of epoxy groups per molecule: (epoxy value × molecular weight) / 100. To calculate the molecular weight: (100 × number of epoxy groups per molecule) / epoxy value. To calculate the molecular weight: epoxy equivalent weight × number of epoxy groups per molecule.

[0051] In one embodiment, the phenol novolac epoxy resin has an EEW of 150 to 250 g / equivalent. In a further embodiment, the phenol novolac epoxy resin has an EEW in any one of the ranges of 150 to 240 g / equivalent, 155 to 235 g / equivalent, 160 to 230 g / equivalent, or 165 to 200 g / equivalent, or any combination thereof.

[0052] In one embodiment, the cresol novolac epoxy resin has an EEW of 150 to 250 g / equivalent. In a further embodiment, the cresol novolac epoxy resin has an EEW in any one of the ranges of 160 to 240 g / equivalent, 170 to 230 g / equivalent, 180 to 220 g / equivalent, or 190 to 215 g / equivalent, or any combination thereof.

[0053] The cresol novolac epoxy resin is generally solid at room temperature. In a further embodiment, the cresol novolac epoxy resin has a softening point in any one of the ranges of 45 to 100 °C, 50 to 95 °C, 60 to 85 °C, or 65 to 80 °C, or any combination thereof.

[0054] In one embodiment, the dicyclopentadiene novolac epoxy resin has an EEW of 200 to 300 g / equivalent. In a further embodiment, the dicyclopentadiene novolac epoxy resin has an EEW in any one of the ranges of 230 to 290 g / equivalent, 240 to 270 g / equivalent, 240 to 260 g / equivalent, or 245 to 255 g / equivalent, or any combination thereof. In one embodiment, the dicyclopentadiene novolac epoxy resin has an epoxy equivalent of approximately 245 to 260 g / equivalent.

[0055] The dicyclopentadiene novolac epoxy resin is generally solid at room temperature. In a further embodiment, the dicyclopentadiene novolac epoxy resin has a softening point in any one of the ranges of 60 to 90 °C, 65 to 75 °C, 68 to 78 °C, 75 to 85 °C, or 79 to 81 °C, or any combination thereof.

[0056] The curing agent used in the present invention may be any single curing agent generally used for epoxy adhesives, or any combination of curing agents. In one embodiment, the curing agent is an amine or a latent amine curing agent. The amine may be an aliphatic, alicyclic, aromatic, or aromatic structure having one or more amino moieties. Exemplary amine curing agents include ethylenediamine, diethylenediamine, diethylenetriamine, triethylenetetramine, propylenediamine, tetraethylenepentamine, hexaethyleneheptamine, hexamethylenediamine, cyanoguanidine, 2-methyl-1,5-pentamethylenediamine, 4,7,10-trioxatridecane-1,13-diamine, aminoethylpiperazine, and the like. Exemplary curing agents include dicyanopolyamides such as dicyandiamide (DICY). 4,4'-Diaminodiphenylsulfone (4,4'-DDS) or 3,3'-diaminodiphenyl (3,3'-DDS), and a mixture of DICY and DDS can also be beneficially used as latent amine curing agents. Dihydrazides such as adipic acid dihydrazide (ADH) and isophthalic acid dihydrazide (IDH), polyamines such as Ancamine® 2441 (Evonic Resource Efficiency GmbH, Marl, Germany), and boron trifluoride monoethylamine (BF3-MEA) complexes such as Anchor 1040 (Air Products Limited, Walton on Thames, Surrey, United Kingdom) are also suitable as latent curing agents.

[0057] In another embodiment, the curing agent is a mixture of a urea-based curing agent component combined with an imidazole curing agent component. The imidazole curing agent may be an imidazole compound or an imidazole adduct. Suitable imidazole curing agents are from the following group of components: 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium-trimellitate, 1-cyanoethyl-2-phenylimidazolium-trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine powder, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct dehydrate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct dehydrate, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a], 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-phenylimidazoline-2,4-diamino-6-vinyl-1,3,5-triazine, 2,4-diamino-6-vinyl-1,3,5-triazine isocyanuric acid adduct, or 2,4-diamino-6-methacryloyloxyethyl-1,3,5-triazine, and may be selected from one or more of them.

[0058] In one embodiment, one or more curing agents may be separated, for example, by encapsulating the curing agent in order to prevent direct contact between the curing component of the curing agent and the remaining portion of the resin matrix with other components of the adhesive composition. In one embodiment, the curing agent is present in an amount of 1 to 10% by weight based on the total weight of the composition. In a further embodiment, the curing agent is present in an amount of 2 to 9% by weight, 3 to 8% by weight, 4 to 7% by weight, or 5 to 6% by weight based on the total weight of the composition, or any combination thereof.

[0059] The self-adhesive resin composition may further include a reinforcing agent. In one embodiment, the reinforcing agent includes a core-shell rubber such as a core-shell rubber manufactured by Kaneka Corporation (Tokyo, Japan) under the trade name Kane Ace (registered trademark) or Kane Ace MX (registered trademark). Examples of such core-shell rubbers include Kane Ace (registered trademark) MX-150, MX-153, MX-154, MX-257, MX-134, MX-135, MX-136, MX-139, MX-267, MX-215, MX-217, MX-236, MX-550, MX-551, and MX553, all of which are epoxy resin-based. The core-shell rubber may be present in an amount of 5 to 30% by weight based on the total weight of the composition. In a further embodiment, the core-shell rubber is present in an amount of 10 to 30% by weight, 15 to 30% by weight, or 20 to 30% by weight based on the total weight of the composition, or any combination thereof.

[0060] In another embodiment, the reinforcing agent includes nitrile rubber or a nitrile rubber adduct. Suitable rubber reinforcing agents include functionalized butadiene acrylonitrile copolymers such as carboxyl-terminated butadiene-acrylonitrile (CTBN) rubber or rubber adducts, and amine-terminated butadiene-acrylonitrile (ATBN) rubber or rubber adducts. Exemplary CTBN rubbers or ATBN rubbers are available from Schill and Seilacher “Struktol” GmbH (Hamburg, Germany) under the trade names Struktol®, Polydis® 3604, 3611, 3614 and 3619. The nitrile rubber may be present in an amount of 1 to 40% by weight, based on the total weight of the composition. In a further embodiment, the nitrile rubber is present in an amount of 2 to 35% by weight, or 3 to 33% by weight, or any combination thereof, based on the total weight of the composition. In one embodiment, the self-adhesive resin composition includes a dicyclopentadiene novolak epoxy resin and a nitrile rubber or nitrile rubber adduct, and the nitrile rubber or nitrile rubber adduct is present in an amount of 1 to 15% by weight, preferably 1 to 10% by weight, based on the total weight of the composition. In another embodiment, the self-adhesive resin composition includes a phenol novolak epoxy resin or a cresol novolak epoxy resin and a nitrile rubber or nitrile rubber adduct, and the nitrile rubber or nitrile rubber adduct is present in an amount of 10 to 40% by weight, preferably 20 to 40% by weight, based on the total weight of the composition.

[0061] In one embodiment, the adhesive composition further includes an oil absorbent. The oil absorbent may include an epoxy component or resin having a linear aliphatic nonpolar adduct. In one embodiment, the oil absorbent may include an epoxy nitrile rubber adduct of the type described heretofore. In another embodiment, the oil absorbent includes an inorganic filler. The particle size of the inorganic filler may range from 50 microns to 500 microns, preferably 100 to 200 microns. One preferred inorganic filler is CaCO 3 which can provide additional oil absorbency due to its porous microstructure. Suitable CaCO 3The filling material is available under the trade name Minfil® from Omya UK Limited (Steeple Morden, Royston, Hertfordshire, United Kingdom). In other embodiments, examples of the oil absorbent include silica, fumed silica, kaolin clay, or absorbent polymers such as polypropylene, polyethylene, and polyvinyl. The oil absorbent may be present in an amount of 1 to 10% by weight, preferably 5 to 10% by weight, based on the total weight of the composition.

[0062] In a further embodiment, the self - adhesive resin composition, by the total weight of the composition, (a) 1 to 45% aromatic epoxy resin; (b) 5 to 60% novolac epoxy resin; (c) 1 to 10% curing agent; (d) 0.05 to 10% corrosion inhibitor; (e) 1 to 40% rubber reinforcing agent; and (f) 1 to 10% inorganic filler.

[0063] In a further embodiment, the corrosion inhibitor of 0.05 to 10% in component (d) in the foregoing embodiment is omitted.

[0064] In another embodiment, the self - adhesive resin composition, by the total weight of the composition, (a) 1 to 45% of one or more base (unfilled) epoxy resins; (b) 5 to 60% novolac epoxy resin; (c) 1 to 10% curing agent; (d) 5 to 30% core - shell rubber; (e) 1 to 40% nitrile rubber - modified epoxy resin; (f) 1 to 10% inorganic filler; (g) 0.05 to 0.5% metal salt of an organic compound; and (h) 0.5 to 2% inorganic polyphosphate.

[0065] In one embodiment, the adhesive composition according to the present invention further comprises a curing accelerator. The curing accelerator may be a urone-type curing accelerator based on a substituted urea. Suitable urea-based materials include materials available under the name DYHARD® from Alzchem Group AG (Trostberg, Germany), and urea derivatives such as those commercially available as UR200, UR300, UR400, UR600, and UR700. In one embodiment, the urone curing accelerator is 4,4'-methylenediphenyl bis(N,N-dimethylurea) (CAS No. 10097-09-3), which is commercially available from Emerald Performance Materials (Moorefield, New Jersey, USA) under the trade name Omicure® U52M. The curing accelerator may be present in an amount of 1 to 15 wt%, preferably 5 to 10 wt%, based on the total weight of the composition.

[0066] In a further embodiment, the self-adhesive resin composition, by the total weight of the composition, (a) 1 to 50% of an aromatic epoxy resin; (b) 10 to 30% of a polyethersulfone; (c) 1 to 10% of an ethylene vinyl acetate copolymer; and (d) 1 to 10% of a curing agent.

[0067] Suitable aromatic epoxy resins and curing agents are as described above. The self-adhesive resin composition may also include a curing accelerator such as a urone-based curing accelerator of the type described above.

[0068] Suitable polyethersulfone (PES) resins include the powder grades SumikaExcel® 3600P, 4100P, 4800P, 5003P, 5200P, 5400P, and 5900P, the non-reinforced pellet grades SumikaExcel® 3600G, 4100G, and 4800G, and the glass fiber-reinforced pellet grades SumikaExcel® 3601GL30, 3601GL20, 4101GL30, and 4101GL20, which are commercially available from Sumitomo Chemical Co., Ltd. (Tokyo, Japan).

[0069] Suitable ethylene vinyl acetate copolymers include DuPont™ Elvax® 750, 760, 760Q, 770, 670, 660, 650Q, 560, 550, 470, 460, 450, 440, 420, 410, 360, 350, 265, 260, 250, 240W, 220W, 150, 150W, 40L-03, 40W, 4355, 4320, 4310, 4260, 760A, 660A, 560A, 550A, 470A, 460A, 450A, 420A, 360A, 265A, 260A, 250A, or 240A, which are commercially available from E.I. du Pont de Nemours and Company (Wilmington, Delaware, United States of America).

[0070] In this embodiment, the self-adhesive resin composition containing polyethersulfone and ethylene vinyl acetate may also contain an oil absorbent. The oil absorbent may include an epoxy component or resin having a linear aliphatic non-polar adduct. In one embodiment, the oil absorbent may include the types of epoxy nitrile rubber adducts described heretofore. In another embodiment, the oil absorbent includes an inorganic filler. The size of the particles of the inorganic filler may be in the range of 50 microns to 500 microns, preferably 100 to 200 microns. One preferred inorganic filler is CaCO 3 which can provide additional oil absorbency due to its porous microstructure. Suitable CaCO 3is available under the trade name Minfil® from Omya UK Limited, Steeple Morden, Royston, Hertfordshire, United Kingdom. In other embodiments, absorbents include silica, fumed silica, kaolin clay, or absorbent polymers such as polypropylene, polyethylene, and polyvinyl. The absorbent may be present in an amount of 1 to 30% by weight, preferably in an amount of 5 to 25% by weight, based on the total weight of the composition.

[0071] In a further embodiment, the self - adhesive resin composition, by the total weight of the composition, (a) 1 to 50% aromatic epoxy resin; (b) 10 to 30% polyethersulfone; (c) 1 to 10% ethylene vinyl acetate copolymer; (d) 1 to 10% curing agent; (e) 1 to 30% inorganic filler; and (f) 1 to 5% curing accelerator.

[0072] In another embodiment, the prepreg according to the invention in the first aspect further comprises an adhesive layer on one or both sides of a fiber - reinforced layer pre - impregnated with resin. After pre - impregnating the self - adhesive resin composition and optionally a second resin composition into the prepreg, the adhesive layer can be applied to the prepreg, for example, by applying a film of a suitable adhesive resin to the surface of the prepreg or by spraying a solution of a suitable resin composition onto the surface of the prepreg.

[0073] In a further aspect, the present invention provides the use of a prepreg according to the first aspect of the present invention for bonding to oiled steel or oiled galvanized steel as a structural reinforcement. The oiled steel or oiled galvanized steel can form parts of a structure that require further industrial process steps. In one embodiment, the prepreg is for bonding to an oiled or oiled galvanized steel blank that is subjected to pressing or pressure. The blank may be for use in the automotive industry, for example, a door panel or a trunk or bonnet cover. In other embodiments, the prepreg may be for use as a structural reinforcement in component parts for a wind turbine, including a nacelle or rotor blade, or in component parts for the aerospace industry, including a nacelle, propeller or rotor, a single-passage wing, and a wide-body wing.

[0074] In another aspect, the present invention provides a process for preparing a self-adhesive prepreg or semi-prepreg, comprising applying a film of a self-adhesive resin composition to a first side of a fiber-reinforced layer, optionally applying a film of the self-adhesive resin composition or a second resin composition to a second side of the fiber-reinforced layer, and compressing the film-coated layer under vacuum.

[0075] In a further aspect, the present invention provides a stack of self - adhesive prepregs according to the present invention in its first aspect. The prepregs may be laid up continuously. In one embodiment, the prepreg is asymmetric and the stack of prepregs has one outermost side that is self - adhesive and one outermost side that includes a standard resin matrix. Such an arrangement can be appropriate when the self - adhesive surface of the stack is intended to provide structural rigidity only to the structure to which this self - adhesive surface is joined. In another embodiment, both sides of the stack of self - adhesive prepregs can be self - adhesive. In a final embodiment of the present invention, the prepregs used to make the stack are symmetric and may include a self - adhesive resin composition as the only resin composition. Alternatively, the prepregs in the stack are asymmetric and may be laid up continuously except for the last prepreg which may be laid up discontinuously such that the self - adhesive resin composition side is outermost. The stack may include a plurality of plies (layers) of prepregs to obtain a desired thickness depending on the particular application for which the stack is intended. In a repair application, for example, a repair material for a final product may have a thickness of 5 mm and the stack may include 2 to 10 plies or layers of prepregs. In other embodiments, the stack may include prepregs of 2 to 100 plies, 3 to 90 plies, 4 to 80 plies, 5 to 70 plies, 6 to 60 plies, 7 to 50 plies, 8 to 40 plies, 9 to 30 plies, or 10 to 20 plies, or any combination thereof. In other applications, the stack of prepregs may be thicker or thinner. For example, for leaf spring applications, the stack of prepregs can be on the order of several millimeters to several centimeters thick.

[0076] In another aspect, the present invention provides a method for structurally reinforcing an article. This includes bringing into contact the adhesive surface of the self-adhesive prepreg according to the present invention in its first aspect, or the adhesive surface of the stack of self-adhesive prepregs according to the present invention in the foregoing aspect, with the article, and curing the prepreg in-situ (in place). The self-adhesive prepreg according to the present invention may be used in the automotive industry to provide structural rigidity and / or to reduce the weight of structural components such as parts of a working body shell or other body panels, such as doors, wings, bonnets, trunk covers, bumpers, etc. In one embodiment, the prepreg is used to provide structural reinforcement to vertical or substantially vertical metal supports of an automobile, including but not limited to A-pillars, B-pillars, C-pillars, D-pillars, etc.

[0077] In a further aspect, the present invention provides a structurally reinforced article obtainable by the method according to the present invention of the foregoing aspect.

Examples

[0078] Example 1 Adhesive composition 1 was prepared from the following: 5.18 g of KSR-177 (a silane-modified epoxy resin manufactured by Kukdo Chemical Company Limited, Seoul, South Korea), 5 g of Struktol® Polydis® 3611 (a CTBN rubber manufactured by Schill and Seilacher “Struktol” GmbH, Hamburg, Germany), 12 g of Araldite® GT6071 (a type 1 bisphenol A epoxy resin manufactured by Huntsman Advanced Materials (Switzerland) GmbH, Basel, Switzerland), 21.5 g of Kane-Ace® MX-153 (a core-shell rubber toughener manufactured by Kaneka Corporation, Tokyo, Japan), 37.5 g of XD1000 (a dicyclopentadiene novolac epoxy resin manufactured by Nippon Kayaku Co., Ltd., Tokyo, Japan), 8 g of Minfil L50 BT (a calcium carbonate filler manufactured by Omya UK Limited, Royston, Hertfordshire, UK), 1 g of Heucophos® SAPP (an inorganic corrosion inhibitor which is a strontium aluminum polyphosphate hydrate manufactured by Heubach GmbH, Langelsheim, Germany), 0.12 g of Heucorin® RZ (a zinc-5-nitroisophthalate organic corrosion inhibitor manufactured by Heubach GmbH, Langelsheim, Germany), 0.2 g of Araldite® DW 0135 Blue (a solventless colored paste manufactured by Huntsman Advanced Materials (Switzerland) GmbH, Basel, Switzerland), 5 g of Dyhard® 100E (a dicyandiamide curing agent manufactured by Alzchem Group Ag, Trostberg, Germany), and 4.5 g of Omicure® U52M (a curing agent manufactured by Emerald Performance Materials, Moorefield, New Jersey, USA).

[0079] The adherent composition 2 was prepared from the following. 15 g of Araldite® GT6099N (a type 9 bisphenol A epoxy resin manufactured by Jubail Chemical Industries Co. (JANA) (Jubail, Saudi Arabia)), 30 g of Struktol® Polydis® 3611 (a CTBN rubber manufactured by Schill and Seilacher “Struktol” GmbH (Hamburg, Germany)), 27 g of YD-136 (a semi-solid epoxy resin manufactured by Kukdo Chemical Company Limited (Seoul, South Korea)), 9.78 g of YDPN 638 (a phenol novolac epoxy resin manufactured by Kukdo Chemical Company Limited (Seoul, South Korea)), 8 g of Minfil® L50 BT (a calcium carbonate filler manufactured by Omya UK Limited, Royston, Hertfordshire, UK), 1.1 g of Heucophos® SAPP (an inorganic corrosion inhibitor which is a strontium aluminum polyphosphate hydrate manufactured by Heubach GmbH (Langelsheim, Germany)), 0.12 g of Heucorin® RZ (a zinc-5-nitroisophthalate organic corrosion inhibitor manufactured by Heubach GmbH (Langelsheim, Germany)), 0.2 g of Araldite® DW 0135 Blue (a solventless colored paste manufactured by Huntsman Advanced Materials (Switzerland) GmbH (Basel, Switzerland)), 4.8 g of Dyhard® 100E (a dicyandiamide curing agent manufactured by Alzchem Group Ag (Trostberg, Germany)) and 4 g of Omicure® U52M (a curing agent manufactured by Emerald Performance Materials (Moorefield, New Jersey, USA)).

[0080] Resin matrix composition 3 was prepared from the following components. 9.7 g of SCT-150 (a cresol novolak epoxy resin manufactured by Shin-A T&C (Seoul, South Korea)), 9.7 g of XD1000 (a dicyclopentadiene novolak epoxy resin manufactured by Nippon Kayaku Co., Ltd. (Tokyo, Japan)), 16.5 g of YDPN 638 (a phenol novolak epoxy resin manufactured by Kukdo Chemical Company Limited (Seoul, South Korea)), 15.5 g of Araldite® GT6071N (a type 1 bisphenol A epoxy resin manufactured by Huntsman Advanced Materials (Switzerland) GmbH (Basel, Switzerland)), 1.5 g of Aerosil® R202 (a hydrophobic fumed silica manufactured by Evonik Resource Efficiency GmbH (Hanau-Wolfgang, Germany)), 1.5 g of PAT®-656 / B3R (an internal mold release agent manufactured by E&P Wurtz GmbH&Co.KG (Bingen am Rhein, Germany)), 19.4 g of Kane-Ace® MX-153 (a core-shell rubber toughening agent manufactured by Kaneka Corporation (Tokyo, Japan)), 6.8 g of Technicure® ADH-J (a pulverized adipic acid dihydrazide curing agent manufactured by A&C Catalysts, Inc. (Linden, New Jersey, USA)), 5.82 g of MDU-11M (U52M) (a curing agent manufactured by Emerald Performance Materials (Moorefield, New Jersey, USA)), and 13.58 g of Epikote® 828 (a liquid epoxy resin of medium viscosity manufactured by Hexion Speciality Chemicals, Inc. (Columbus, Ohio, USA)).

[0081] A sample film of the adhesion composition 1 or the adhesive composition 2 was laminated onto the surface of a 150 mm × 150 mm piece of the BB600 fabric, and a sample film of the resin matrix composition 3 was laminated onto the back surface of each piece of the BB600 fabric to form a single - ply asymmetric self - adhesive prepreg. The weight of the adhesion composition 1, the adhesive composition 2, or the resin matrix composition 3 present in the film layer was calculated to obtain an asymmetric prepreg having a total adhesive / resin content of 50% based on the total weight of the prepreg. The prepreg was cut into 25 mm × 12.5 mm (with 12.5 mm overlap) for the lap - shear strength test. The asymmetric two - ply of the adhesive prepreg 1 or the adhesive prepreg 2 was stacked with the adhesive side outermost and the resin matrix side innermost, and cured between clean galvanized steel substrates at a temperature of 150 °C for 15 minutes. The resulting lap - shear strength (MPa) was measured in accordance with BS EN2243 - 1:2005.

[0082] The cured prepreg stack (two - ply) made from the BB600 fabric pre - impregnated with the adhesion composition 1 and the resin matrix composition 3 showed a lap - shear strength of 19.5 MPa on clean galvanized steel, having an SD value of 0.9 and a CV value of 4.5. The defective state was an aggregated state in the adhesive.

[0083] The cured prepreg stack (two - ply) made from the BB600 fabric pre - impregnated with the adhesive composition 2 and the resin matrix composition 3 showed a lap - shear strength of 21.2 MPa on clean galvanized steel, having an SD value of 1.9 and a CV value of 9. The defective state was an aggregated state in the adhesive.

[0084] Example 2 Similar to Example 1, the adhesion compositions 1 and 2 and the resin matrix composition 3 were prepared.

[0085] A sample film of the adhesion composition 1 or the adhesive composition 2 was laminated onto the surface of a 150 mm × 150 mm piece of BB200 fabric, and the resin matrix composition 3 was laminated onto the back surface of each piece of BB200 fabric to form a single - ply asymmetric self - adhesive prepreg. The weight of the adhesion composition 1, the adhesive composition 2, or the resin matrix composition 3 present in the film layer was calculated to obtain an asymmetric prepreg having a total adhesive / resin content of 50% based on the total weight of the prepreg. The prepreg was cut into 25 mm × 12.5 mm (with a 12.5 mm overlap) for the lap - shear strength test. The asymmetric two - ply of the adhesive prepreg 1 or the adhesive prepreg 2 was stacked with the adhesive side outermost and the resin matrix side innermost and cured between clean zinc - plated steel substrates at a temperature of 150 °C for 15 minutes. The lap - shear strength (MPa) of the resulting product was measured according to BS EN2243 - 1:2005.

[0086] The cured prepreg stack (two - ply) made from the adhesion composition 1 showed a lap - shear strength of 22.6 MPa on clean zinc - plated steel with an SD value of 0.7 and a CV value of 3.2. The defective state was an aggregated state in the adhesive.

[0087] The cured prepreg stack (two - ply) made from the adhesive composition 2 showed a lap - shear strength of 24.7 MPa on clean zinc - plated steel with an SD value of 1.1 and a CV value of 4.6. The defective state was an aggregated state in the adhesive.

[0088] Example 3 Similar to Example 1, the adhesion composition 1 was prepared.

[0089] A sample film of the adhesion composition 1 was laminated onto the front and back surfaces of a 150 mm × 150 mm piece of BB200 fabric to form a single-ply symmetric self-adhesive prepreg 1. The weight of the adhesion composition 1 present in the film layer was calculated to obtain a symmetric prepreg having a total content of the adhesion composition of 50% based on the total weight of the prepreg. The prepreg was cut into 25 mm × 12.5 mm (with a 12.5 mm overlap) for the lap shear strength test. The symmetric single-ply of the adhesive prepreg 1 was cured between clean zinc-plated steel substrates at a temperature of 150 °C for 15 minutes. The two symmetric plies of the adhesive prepreg were sequentially stacked and cured between clean zinc-plated steel substrates at a temperature of 150 °C for 15 minutes. The lap shear strength (MPa) obtained as a result of both the single-ply symmetric prepreg and the double-ply symmetric prepreg of the adhesion composition 1 was measured in accordance with BS EN2243-1:2005.

[0090] The cured prepreg (1 ply) made from the adhesion composition 1 showed a lap shear strength of 25.2 MPa on clean zinc-plated steel with an SD value of 0.2 and a CV value of 0.8. The defective state was an aggregated state in the adhesive.

[0091] The cured prepreg stack (2 plies) made from the adhesion composition 1 showed a lap shear strength of 23.2 MPa on clean zinc-plated steel with an SD value of 0.9 and a CV value of 3.7. The defective state was an aggregated state in the adhesive.

[0092] Example 4 Similar to Example 1, the adhesion composition 2 was prepared.

[0093] A sample film of the adhesion composition 2 was laminated onto the front and back surfaces of a 150 mm × 150 mm piece of BB600 fabric to form a single-ply symmetric self-adhesive prepreg 2. The weight of the adhesion composition 2 present in the film layer was calculated to obtain a symmetric prepreg having a total content of the adhesion composition of 50% based on the total weight of the prepreg. The prepreg was cut into 25 mm × 12.5 mm (with a 12.5 mm overlap) for the lap shear strength test. The symmetric single-ply of the adhesive prepreg 1 was cured between clean zinc-plated steel substrates at a temperature of 150 °C for 15 minutes. The two symmetric plies of the adhesive prepreg were sequentially stacked and cured between clean zinc-plated steel substrates at a temperature of 150 °C for 15 minutes. The lap shear strength (MPa) obtained for both the single-ply symmetric prepreg and the double-ply symmetric prepreg of the adhesion composition 1 was measured in accordance with BS EN2243-1:2005.

[0094] The cured prepreg (1 ply) made from the adhesion composition 2 showed a lap shear strength of 26.2 MPa on clean zinc-plated steel, with an SD value of 1.8 and a CV value of 6.8. The defective state was an aggregated state in the adhesive.

[0095] The cured prepreg stack (2 plies) made from the adhesion composition 1 showed a lap shear strength of 24.9 MPa on clean zinc-plated steel, with an SD value of 1.4 and a CV value of 5.5. The defective state was an aggregated state in the adhesive.

[0096] The inventors have found that the self-adhesive prepreg (asymmetric prepreg) prepared according to the present invention from BB600 or BB200 fabric impregnated on one side with a self-adhesive resin composition containing a corrosion inhibitor and on the other side with a standard resin matrix composition containing an internal release agent showed good lap shear strength on clean zinc-plated steel. The asymmetric two-ply prepreg showed increased lap shear strength for the BB200 fabric compared to the BB600 fabric.

[0097] The inventors have found that the self-adhesive prepreg (symmetric prepreg) prepared according to the present invention from a BB600 or BB200 fabric impregnated on both sides with a self-adhesive resin composition containing a corrosion inhibitor exhibited good lap shear strength on clean galvanized steel. In the test fabrics used (BB200 and BB600), there was almost no change in the lap shear strength between prepregs including single ply (1 ply) of the fabric and 2-ply (2 ply) stack of the fabric. The best lap shear strength results were obtained for both adhesive compositions using the BB200 fabric. The aspects or embodiments that may be included in the present invention are summarized as follows. [1]. A prepreg comprising a fiber-reinforced layer having a first side and a second side, wherein the first side of the fiber-reinforced layer is pre-impregnated with a self-adhesive resin composition. [2]. The prepreg according to item 1 above, wherein the second side of the fiber-reinforced layer is also pre-impregnated with the self-adhesive resin composition. [3]. The prepreg according to item 1 above, wherein the second side of the fiber-reinforced layer is pre-impregnated with a second resin composition. [4]. The prepreg according to item 3 above, wherein the second resin composition is non-adhesive. [5]. The prepreg according to item 3 or 4 above, wherein the second resin composition contains an internal release agent. [6]. The prepreg according to any one of items 3 to 5 above, wherein the second resin composition has substantially the same curing rate as the self-adhesive resin composition. [7]. The prepreg according to any one of items 1 to 6 above, wherein the self-adhesive resin composition can be cured by heating at a temperature of 140 to 170 °C within 60 minutes. [8]. The prepreg according to any one of items 1 to 7 above, wherein the cured self-adhesive resin composition has a lap shear strength of at least 20 MPa at ambient temperature. [9]. The prepreg according to any one of items 1 to 8 above, wherein the cured self-adhesive resin composition has a peel strength of at least 100 N / 25 mm at ambient temperature.

[10] . The prepreg according to any one of items 1 to 9 above, wherein the self-adhesive resin composition contains a silane-modified epoxy resin.

[11] . The prepreg according to any one of items 1 to 10 above, wherein the self-adhesive resin composition contains an epoxy novolac resin.

[12] . The prepreg according to item 11 above, wherein the self-adhesive resin composition containing the epoxy novolac resin contains a dicyclopentadiene novolac epoxy resin or a phenol novolac epoxy resin.

[13] . The prepreg according to any one of items 1 to 12 above, wherein the self-adhesive resin composition contains a core-shell rubber reinforcing agent and / or a carboxyl-terminated butadiene-acrylonitrile rubber reinforcing agent or an amine-terminated butadiene-acrylonitrile rubber reinforcing agent.

[14] . The prepreg according to any one of items 1 to 13 above, further comprising a corrosion inhibitor.

[15] . The prepreg according to item 14 above, wherein the corrosion inhibitor is a metal salt of an organic compound.

[16] . The prepreg according to item 14 above, wherein the corrosion inhibitor is an inorganic polyphosphate.

[17] . The self - adhesive composition contains, based on the total weight of the composition, (a) 1 to 45% of an aromatic epoxy resin; (b) 5 to 60% of a novolac epoxy resin; (c) 1 to 10% of a curing agent; and optionally, (d) 0.05 to 10% of a corrosion inhibitor The prepreg according to any one of items 1 to 16 above.

[18] . The prepreg according to any one of items 1 to 16 above, wherein the self - adhesive resin composition contains a polyethersulfone resin.

[19] . The self - adhesive composition contains, based on the total weight of the composition, (a) 1 to 50% of an aromatic epoxy resin; (e) 10 to 30% of a polyethersulfone; (f) 1 to 10% of an ethylene - vinyl acetate copolymer; and (g) 1 to 10% of a curing agent The prepreg according to item 18 above.

[20] . The prepreg according to any one of items 1 to 19 above, wherein the fiber - reinforced layer contains non - woven fabric fibers, preferably veils, or discontinuous fiber fleeces.

[21] . The prepreg according to item 20 above, wherein the resin content on the first side and / or the second side of the pre - impregnated fiber - reinforced layer is 30 wt% to 90 wt%.

[22] . The prepreg according to any one of items 1 to 19 above, wherein the fiber - reinforced layer contains woven fibers or fabrics.

[23] . The prepreg according to any one of items 1 to 20 above, wherein the fiber - reinforced layer contains a non - woven fabric.

[24] . The prepreg according to item 22 or 23 above, wherein the resin content on the first side and / or the second side of the pre - impregnated fiber - reinforced layer is 30 wt% to 50 wt%.

[25] . The prepreg according to any one of items 1 to 24 above, wherein the fiber - reinforced layer has a density of 200 to 400 grams per square meter.

[26] . Use of the prepreg according to any one of items 1 to 25 above for bonding to oil - coated steel or oil - coated galvanized steel as a structural reinforcement.

[27] . A process for preparing a self - adhesive prepreg or semi - prepreg, comprising applying a film of a self - adhesive resin composition to a first side of a fiber - reinforced layer, optionally applying a film of the self - adhesive resin composition or a film of a second resin composition to a second side of the fiber - reinforced layer, and compressing the film - coated layer under vacuum.

[28] . A stack of self - adhesive prepregs according to any one of items 1 to 25 above, wherein both outer surfaces of the stack are self - adhesive.

[29] . A method for structurally reinforcing an article, the method comprising contacting the article with the adhesive surface of the self-adhesive prepreg according to any one of Items 1 to 25 above, or the adhesive surface of the stack of the self-adhesive prepreg according to Item 28 above, and curing the prepreg in situ.

[30] . A structurally reinforced article obtained by the method according to Item 29 above.

Claims

1. A prepreg comprising a fiber-reinforced layer having a first side and a second side, wherein the first side of the fiber-reinforced layer is pre-impregnated with a self-adhesive resin composition, wherein the self-adhesive composition is either (i) a self-adhesive composition comprising, based on the total weight of the composition: (i) with respect to the total weight of the composition, (a) 1 to 45% aromatic epoxy resin; (b) 5 to 60% novolac epoxy resin; (c) 1 to 10% curing agent; and optionally, (d) 0.05 to 10% corrosion inhibitor or (ii) a self-adhesive composition comprising, based on the total weight of the composition: (ii) with respect to the total weight of the composition, (a) 1 to 50% aromatic epoxy resin; (e) 10 to 30% polyethersulfone; (f) 1 to 10% ethylene vinyl acetate copolymer; and (g) 1 to 10% curing agent wherein the self-adhesive resin composition comprises a silane-modified epoxy resin as the aromatic epoxy resin, and the self-adhesive resin composition does not contain a methoxy group-containing silane-modified epoxy resin obtained by subjecting a bisphenol-type epoxy resin and a methoxysilane partial condensate to a dealcoholization reaction, prepreg.

2. The prepreg according to claim 1, wherein the second side of the fiber-reinforced layer is also pre-impregnated with the self-adhesive resin composition.

3. The prepreg according to claim 1, wherein the second side of the fiber-reinforced layer is pre-impregnated with a second resin composition.

4. The prepreg according to claim 3, wherein the second resin composition contains an internal release agent.

5. The prepreg according to claim 3 or 4, wherein the second resin composition has a substantially the same curing rate as the self-adhesive resin composition.

6. The prepreg according to any one of claims 1 to 5, wherein the self-adhesive resin composition can be cured by heating at a temperature of 140 to 170 °C within 60 minutes.

7. The prepreg according to any one of claims 1 to 6, wherein the cured self-adhesive resin composition has a lap shear strength of at least 20 MPa at ambient temperature.

8. The prepreg according to any one of claims 1 to 7, wherein the cured self-adhesive resin composition has a peel strength of at least 100 N / 25 mm at ambient temperature.

9. The prepreg according to claim 1, wherein the self-adhesive resin composition containing the epoxy novolac resin contains a dicyclopentadiene novolac epoxy resin or a phenol novolac epoxy resin.

10. ​ The prepreg according to any one of claims 1 to 9, wherein the self-adhesive resin composition contains a core-shell rubber reinforcing agent and / or a carboxyl-terminated butadiene-acrylonitrile rubber reinforcing agent or an amine-terminated butadiene-acrylonitrile rubber reinforcing agent.

11. The prepreg according to claim 1, wherein the corrosion inhibitor is a metal salt of an organic compound.

12. The prepreg according to claim 1, wherein the corrosion inhibitor is an inorganic polyphosphate.

13. The prepreg according to any one of claims 1 to 12, wherein the fiber-reinforced layer contains nonwoven fibers.

14. The prepreg according to claim 13, wherein the fiber-reinforced layer contains, as the nonwoven fibers, a veil or a discontinuous fiber fleece.

15. The prepreg according to claim 13 or 14, wherein the resin content on the first side and / or the second side of the pre-impregnated fiber-reinforced layer is 30% by weight to 90% by weight.

16. The prepreg according to any one of claims 1 to 12, wherein the fiber-reinforced layer contains woven fibers or fabrics.

17. The prepreg according to any one of claims 1 to 14, wherein the fiber-reinforced layer contains a nonwoven fabric.

18. The prepreg according to claim 16 or 17, wherein the resin content on the first side and / or the second side of the pre-impregnated fiber-reinforced layer is 30% by weight to 50% by weight.

19. The prepreg according to any one of claims 1 to 18, wherein the fiber-reinforced layer has a density of 200 to 400 grams per square meter.

20. Use of the prepreg according to any one of claims 1 to 19 for bonding to oil-coated steel or oil-coated galvanized steel as a structural reinforcement.

21. A process for preparing a self-adhesive prepreg or semi-prepreg, comprising applying a film of a self-adhesive resin composition to a first side of a fiber-reinforced layer, optionally applying a film of the self-adhesive resin composition or a film of a second resin composition to a second side of the fiber-reinforced layer, and compressing the film-coated layer under vacuum, wherein the self-adhesive composition is (i) Based on the total weight of the composition, (a)1 to 45% aromatic epoxy resin; (b)5 to 60% novolac epoxy resin; (c)1 to 10% curing agent; and optionally, (d)0.05 to 10% corrosion inhibitor a self-adhesive composition comprising, or (ii) Based on the total weight of the composition, (a) 1 to 50% of an aromatic epoxy resin; (e) 10 to 30% of a polyethersulfone; (f) 1 to 10% of an ethylene vinyl acetate copolymer; and (g) 1 to 10% of a curing agent is any one of the self-adhesive compositions, wherein the self-adhesive resin composition contains a silane-modified epoxy resin as the aromatic epoxy resin, the self-adhesive resin composition does not contain a methoxy group-containing silane-modified epoxy resin obtained by subjecting a bisphenol-type epoxy resin and a methoxysilane partial condensate to a dealcoholization reaction, process.

22. A stack of self-adhesive prepregs according to any one of claims 1 to 19, wherein both outer surfaces of the stack are self-adhesive.

23. A method of structurally reinforcing an article, the method comprising contacting the article with the adhesive surface of a self-adhesive prepreg according to any one of claims 1 to 19 or the adhesive surface of a stack of self-adhesive prepregs according to claim 22, and curing the prepreg in situ.

24. A structurally reinforced article obtained by the method according to claim 23.

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