The present invention relates to a method for producing a prepreg which contains reinforcing fibers and a matrix resin composition with the weight per square meter of the reinforcing fibers being 250-2,000 g/m2. The production method comprises the following steps (1)-(3): (1) a matrix resin composit
The present invention relates to a method for producing a prepreg which contains reinforcing fibers and a matrix resin composition with the weight per square meter of the reinforcing fibers being 250-2,000 g/m2. The production method comprises the following steps (1)-(3): (1) a matrix resin composition blending step for obtaining a matrix resin composition by mixing an epoxy resin, a radically polymerizable unsaturated compound, an epoxy resin curing agent and a polymerization initiator that generates radicals, in said step the content of the radically polymerizable unsaturated compound relative to 100% by mass of the total of the epoxy resin and the radically polymerizable unsaturated compound being 10-25% by mass; (2) a matrix resin composition impregnating step; and (3) a surface viscosity increasing step.
대표청구항▼
1. A method for producing a prepreg which contains reinforcing fibers and a matrix resin composition with the weight per square meter of the reinforcing fibers being 250-2,000 g/m2, the production method comprising the following steps (1)-(3): (1) a matrix resin composition blending step for obtaini
1. A method for producing a prepreg which contains reinforcing fibers and a matrix resin composition with the weight per square meter of the reinforcing fibers being 250-2,000 g/m2, the production method comprising the following steps (1)-(3): (1) a matrix resin composition blending step for obtaining a matrix resin composition having a viscosity of 12 Pa·s to 3,000 Pa·s at 30° C. by mixing an epoxy resin, a radically polymerizable unsaturated compound, an epoxy resin curing agent and a polymerization initiator that generates radicals, in said step the content of the radically polymerizable unsaturated compound relative to 100% by mass of the total of the epoxy resin and the radically polymerizable unsaturated compound being 10-25% by mass;(2) a matrix resin composition impregnating step for obtaining a prepreg precursor by impregnating a reinforcing fiber assembly being 250-2,000 g/m2 in weight with the matrix resin composition; and(3) a surface viscosity increasing step of obtaining a prepreg in which viscosity of the matrix resin composition is increased more in a superficial part than in a central part, by letting the polymerization initiator present in the superficial part of the prepreg precursor generate a radical, while not letting the polymerization initiator present in the central part generate a radical, whereinthe step (2) includes the following steps (2-i) to (2-iii):(2-i) a matrix resin composition applying step comprising applying the matrix resin composition only to one face of a first reinforcing fiber sheet A1 composed of consecutive reinforcing fiber bundles;(2-ii) a reinforcing fiber matrix laminating step comprising laminating a second reinforcing fiber sheet A2 composed of consecutive reinforcing fiber bundles onto the face of the fiber sheet A1 to which the matrix resin composition has been applied, wherein the matrix resin composition is only present on the A1 fiber sheet; and(2-iii) a pressurizing step comprising impregnating the A1 and the A2 fiber sheets with the matrix resin composition by pressurizing the A1 and A2 fiber sheets so that the matrix resin composition migrates outward from inside the A1 and the A2 fiber sheets to form the prepreg precursor. 2. The method for producing a prepreg according to claim 1, wherein a means for letting the polymerization initiator generate a radical in the above described step (3) is the following method (3-i): (3-i) a method of irradiating the prepreg precursor with an energy wave selected from a group consisting of: ultraviolet; infrared; visible light; and electron beam, with an incident intensity no greater than such an incident intensity that transmittance becomes 0% at a depth of 40% from a surface of the prepreg precursor with respect to a thickness of the prepreg precursor being 100%. 3. The method for producing a prepreg according to claim 2, wherein the polymerization initiator is α-aminoalkyl phenone or α-hydroxyalkyl phenone. 4. The method for producing a prepreg according to claim 1, wherein a means for letting the polymerization initiator generate a radical in the above described step (3) is the following method (3-ii): (3-ii) a method of heating the prepreg precursor from the outside in a non-contact state, for such a time period that a rate of temperature change becomes 0% at a depth of 40% from a surface of the prepreg precursor with respect to a thickness of the prepreg precursor being 100%. 5. The method for producing a prepreg according to claim 4, wherein the method (3-ii) is realized by high frequency heating. 6. The method for producing a prepreg according to claim 1, wherein the weight per square meter of the reinforcing fibers is 400-2,000 g/m2. 7. The method for producing a prepreg according to claim 1, wherein the weight per square meter of the reinforcing fibers is 500-2,000 g/m2. 8. The method for producing a prepreg according to claim 1, wherein in step (2-i), the matrix resin composition is applied only to one face of the first reinforcing fiber sheet A1 by: (i) a touch roller method in which the one face of the first reinforcing fiber sheet A1 contacts with the touch roller so that the matrix resin composition is applied only to the one face of the first reinforcing fiber sheet A1; or (ii) a die coating method in which the matrix resin composition is extruded from a resin bath and applied to the one face of the first reinforcing fiber sheet A1. 9. A method for producing a prepreg which contains reinforcing fibers and a matrix resin composition with the weight per square meter of the reinforcing fibers being 250-2,000 g/m2, the production method comprising the following steps (1)-(3): (1) a matrix resin composition blending step for obtaining a matrix resin composition having a viscosity of 12 Pa·s to 3,000 Pa·s at 30° C. by mixing an epoxy resin, a radically polymerizable unsaturated compound, an epoxy resin curing agent and a polymerization initiator that generates radicals, in said step the content of the radically polymerizable unsaturated compound relative to 100% by mass of the total of the epoxy resin and the radically polymerizable unsaturated compound being 10-25% by mass;(2) a matrix resin composition impregnating step for obtaining a prepreg precursor by impregnating a reinforcing fiber assembly being 250-2,000 g/m2 in weight with the matrix resin composition; and(3) a surface viscosity increasing step of obtaining a prepreg in which viscosity of the matrix resin composition is increased more in a superficial part than in a central part, by letting the polymerization initiator present in the superficial part of the prepreg precursor generate a radical, while not letting the polymerization initiator present in the central part generate a radical,wherein the step (2) includes the following steps (2-iv) to (2-vi):(2-iv) a matrix resin composition applying step comprising applying the matrix resin composition only to one face of a first reinforcing fiber sheet A1 composed of consecutive reinforcing fiber bundles or applying the matrix resin composition only to both a first face and a second face of the first reinforcing fiber sheet A1;(2-v) a reinforcing fiber matrix laminating step comprising laminating a second reinforcing fiber sheet A2 composed of consecutive reinforcing fiber bundles, and a third reinforcing fiber sheet A3 composed of consecutive reinforcing fiber bundles, onto the first face of the A1 fiber sheet and the second face of the A1 fiber sheet respectively, wherein the matrix resin composition is only present on the A1 fiber sheet; and(2-vi) a pressurizing step comprising impregnating the A1 fiber sheet, the A2 fiber sheet, and the A3 fiber sheet with the matrix resin composition by pressurizing the A1, the A2, and the A3 fiber sheets so that the matrix resin composition migrates outward from inside of the A1, the A2 and the A3 fiber sheets to obtain the prepreg precursor. 10. The method for producing a prepreg according to claim 9, wherein a means for letting the polymerization initiator generate a radical in the above described step (3) is the following method (3-i): (3-i) a method of irradiating the prepreg precursor with an energy wave selected from a group consisting of: ultraviolet; infrared; visible light; and electron beam, with an incident intensity no greater than such an incident intensity that transmittance becomes 0% at a depth of 40% from a surface of the prepreg precursor with respect to a thickness of the prepreg precursor being 100%. 11. The method for producing a prepreg according to claim 9, wherein the weight per square meter of the reinforcing fibers is 400-2,000 g/m2. 12. The method for producing a prepreg according to claim 9, wherein the weight per square meter of the reinforcing fibers is 500-2,000 g/m2. 13. The method for producing a prepreg according to claim 9, wherein in step (2-iv), the matrix resin composition is applied to only one face of the first reinforcing fiber sheet A1. 14. The method for producing a prepreg according to claim 9, wherein in step (2-iv), the matrix resin composition is applied only to the first reinforcing fiber sheet A1 by: (i) a touch roller method in which the one face or the both first and second faces of the first reinforcing fiber sheet A1 contacts the touch roller so that the matrix resin composition is applied to the one face or the both first and second faces of the first reinforcing fiber sheet A1; or (ii) a die coating method in which the matrix resin composition is extruded from a resin bath and applied to the one face or the both first and second faces of the first reinforcing fiber sheet A1.
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