PULTRUSION WITH CURE BY ULTRAVIOLET RADIATION

Abstract: Pultrusion with cure by ultraviolet (UV) radiation, art for manufacturing FRP wherein a continuous reinforcing material, most commonly, glass roving is first impregnated with a curable liquid resin and pulled through a UV transmittent die, for instance, glass, having a desired cross section and a sufficient length to effect the cure and, during passage through such a die, the continuous resinous material or FRP material is subjected to exposure to UV radiation to complete the pultrusion. The present improvement lies in prevention of sticking trend of the uncured resinous material onto the internal wall of the die, whereby pultruded products having good regeneration of a die section were hardly attained conventionally. the present invention proposes elimination of the sticking trend by coating on internal wall of the glass die, further proposes use of a pipe die having a short length which is insufficient to complete the cure reactions, and then, after passing through such a die, the FRP material to be cured is introduced into a medium liquid of UV transmittent type, for instance, water, so as to have static liquid pressure and therein the material is exposed to UV radiation.

Description: This invention relates to the production of fiber reinforced plastics, which will be noted FRP. In particular, this invention relates to shaping of FRP by the art of pultrusion. The term "pultrusion" is generally used to mean the art for manufacturing FRP wherein a continuous reinforcing material, most commonly, a filamentary material, is first impregnated with a curable or polymerizable liquid resin and pulled through a die having a desired cross section to shape the impregnated resinous material with polymerization cure into a cured product having a continuous length having a uniform cross section which has been molded by the die. EP-A-0 118 079 discloses a heatable hollow mold having an inner low friction layer for producing a fiber product. This product is formed by continuously heating the basic material by the way of microwave means. EP-A-0 206 545 is related to a devisable recoating mold forming a cavity when closed for recoating optical waveguide fibers with a UV-curable resin. The mold includes means for introducing UV-light into the cavity for curing the resin. In pultrusion, because any polymerizable or curable liquid resin may be utilized, polymerization or cure by radiation of ultraviolet ray, which will be noted UV, has conventionally been studied. However, a difficulty involved in a curing process by UV radiation has been a strong sticking trend of uncured or half-cured liquid resin onto the die inside surfaces, with which the resin is in contact during the process from initial liquid stage to cured solid stage. Specifically, a commonly applied die was a pipe made of glass, which is not absorptive of UV and, through the glass wall externally, UV was radiated at internally travelling target things to be cured. In such a process, a sticking or adhering trend of the resin onto the internal face of the glass pipe was inevitable which demands more powerful pull force and, even if such an operation were maintained with overcoming force, it was not possible to avoid occurrence of deposit or layering of polymerized resin thereon with time, which would impede exact regeneration with products of an applied die section shape, thus commonly rendering thinner or deformed cross sections. This invention is intended to provide pultrusion with cure by UV radiation free of such conventional difficulty as noted above. And the intended pultrusion process is accomplished in this invention by the following manner. Firstly, the glass die, which is meant for a die having a length sufficient to effect the cure, is improved by an internal coating or compositing with a UV transmissive material having more repulsion or rejection to the sticking trend, for instance, with a silicone or fluorine compound. Alternatively, the pipe die is made of a UV transmissive plastic, for instance, polyethylene or polypropylene and thereon internally coated with a silicone or fluorine compound as noted above. Otherwise, the pipe die itself is made of such a material as more repulsive to the sticking, for instance, an appropriate silicone or fluorine resin. Secondly, apart from employing a pipe die having a suitable length sufficient to complete the whole cure reactions therein, the impregnated material or FRP material is pulled into a die having a short length insufficient to complete the cure, but sufficient to effect impressing or shaping of the die cross section with the impregnant material at substantially uncured stage and just subsequently, the uncured continuous material is introduced into a UV transmissive, liquid medium which is substantially immiscible with the resin being cured, and therein the impregnated material is exposed to UV radiation. The UV transmissive, medium liquid comprises, for instance, water or silicone oils. And in the second art, the die may be made of a metal, for instance, stainless steel which is not UV transmissive, or of the improved glass or plastic pipe as mentioned in the first art. Further, the die may be modified to be a connection of a stainless pipe at a base portion extended forwardly with the improved glass or plastic pipe as mentioned in the first art. This modified version of the die design is effective when very initial stage of the whole cure is planned to occur during passage in the die and such a device is desirable in lateral or horizontal pull as will be described and illustrated hereinlater. Said curable liquid resin, when it is in the form of a liquid mass, called coating material, may be unsaturated polyester, which is most commonly produced by reacting maleic and/or fumaric acid with propylene glycol followed by thinning with styrene, or unsaturated acrylate, for instance, ester acrylate, epoxy acrylate, urethane acrylate. A UV sensitizer, which will be incorporated in a coating material, may be chosen from a conventional group known to be effective in UV cure. Said reinforcing filamentary material may be glass fiber or other inorganic fibers; for instance, boron fiber, otherwise, organic fibers; for instance, nylon, polyester, polyethylene, polypropylene so far as they are substantially UV transmissive. However, carbon fiber which is commonly manufactured by carbonization of acrylic fiber is excepted, because of UV absorptive property. Example of said silicone and fluorine resin may be any of those known as silicone resin or silicone rubber; fluorine resin or fluorine rubber. Glass may be any kind of glass which the term "glass" customarily includes, for instance, quartz. Fig. 1 schematically shows a lateral pultrusion with use of a pipe die having a sufficient length to complete a cure attempted. Fig. 2 similarly shows a vertical or upward pultrusion with passage through a medium liquid. Fig. 3 similarly shows a lateral pultrusion with passage through a medium liquid. As will be understood, the embodiment of Fig. 1 belongs to the first art and those of Figs. 2 and 3 belong to the second art in terms used in the foregoing paragraphs. Fig. 4 schematically shows a longitudinal section of a tip portion of a die or mandrel which is provided with skin/core double ports, wherein such two ports will be often used to make FRP by the core port and to form non FRP annular coverage or skin or cladding by the skin port. These drawings are given by way of illustrating the inventive embodiments and therefore these should not be construed to limit the present invention. Embodiments will be first explained with reference to the drawings, wherein a like numeral indicates a like part through these drawings. 1 is a reinforcing filamentary material in the form of roving or two or the like, which is converted to be impregnated form as noted above, wherewith an arrow line indicates a travelling direction. 2 is a coating material or mass of a curable liquid resin. 3 is a unit for UV radiation, wherein arrow lines symbolize radiation. 4 is a pipe die, which may be of circular section, otherwise, it may be of non circular section to manufacture some profiled product, for instance, T-shaped section or canal section. 5 is a UV lamp. 6 is a medium liquid. Further, 1a is a guide roller, 2a is a coating material tank, 4a is an exit nozzle, 6a is a medium liquid tank. In Fig. 4, 10 is a core stream, 10D is the diameter thereof, 10W is a die wall therefor, and 11 is a skin stream, 11D is the diameter thereof, 11W is a die wall therefor. In the case the of Fig. 1 embodiment, the die should be a kind of the improved ones as noted before and a medium liquid is not involved. In the case of the Fig. 2 embodiment, the die may be short in length and may be made of a UV absorptive material, for instance, stainless steel. In the case the of Fig. 3 embodiment, the die may be a modified one as noted before. Making reference to Figs. 2 and 3, these two cases employ a medium liquid, on which account the upward pull (Fig. 2) requires a liquid seal construction with the entry die 4 which is mounted at the bottom of the unit 3. At a point where the continuous resinous material or may be called FRP material is pulled out of the die tip, the material is still at substantially uncured or nearly liquid state, whereat it receives static liquid pressure, proportional to the depth of the liquid, which will serve to avoid disintegration of the material. Then, UV radiation initiates solidification of skin of the resinous material. As the material travels upward with lessening pressure, curing reaction progresses with penetration into the core portion of the material. Therefore, the change in liquid pressure and progress in cure are well balanced in this process. In contrast, the Fig. 3 process must move the continuous resinous material in a direction transversal to the direction of gravity. Therefore, some skin cure of the material by UV radiation is desired to take place while the material is travelling inside the die or before being pulled out of the die, in order to avoid disintegration thereof. For this purpose, a modified die as described before is suitable, because such a die can receive UV radiation in its forward portion. Further, this process requires a liquid seal construction at two places; at the entry die and also at the exit nozzle. It is to be noted here that a medium liquid will serve as compacter to apply pressure to a resinous material as noted before and further it will serve as a coolant to reactions taking place, which are often exothermic and wherein furious local exothermic trend should be avoided to prevent the finished rod surfaces from damage or having an impaired look, for which purpose the double port die will be effective, as will be illustrated later. The continuous resinous material or FRP material thus cured, accordingly, which may be called prutruded rod or pole, will be normally wound around a roll. If the rod is so rigid as to be unsuitable for winding, it will be cut into some convenient length. Such finishing jobs will be done with artisan knowledge. Example 1 In the Fig. 1 embodiment, pultrusion was conducted under the following experimental conditions. Mold; a tube made of PTFE, a kind of fluorine resin, inner dia.= 2 mm, outer dia.= 4 mm, length = 30 cm. UV lamp; a high pressure UV lamp, air cooling, 80 w/cm, 1 kw, two lamps. Coating material; ester acrylate (brandnamed ARONIX M6100 by TOA GOSEI CO.) 100 parts. UV sensitizer; benzildimethyl ketal (brandnamed IRGACURE 651 by CIBA-GEIGY) 2 parts. Internal mold release; 2 parts. Filamentary material; glass roving. Pultrusion speed; 5 m/min. Finished rod has superior quality. Example 2 In the Fig. 2 embodiment, pultrusion was conducted under the following conditions: Mold; made of stainless steel, inner dia.= 2.0 mm. UV lamp: high pressure UV lamp, 80 w/cm, 1 kw, one lamp. Coating material; ester acrylate (brandnamed ARONIX M6100 by TOA GOSEI CO.) 100 parts. UV sensitizer; (benzildimethyl ketal, brandnamed IRGACURE 651 by CIBA-GEIGY) 4 parts. Filamentary material; glass roving. Medium liquid; water. Pultrusion speed; 10 m/min. Finished rod has superior quality, which is compared as below to a control experiment wherein the cure was conducted in the air. Product of Ex. 2 Control Surface Finish: improved impaired Surface Hardness: over 80 under 60 Dia.of Finished Rod: 1.92 ± 0.05 1.90 ± 0.1 Note 1.In the surface finish, "improved" indicates that there are no sticky remains and "impaired" indicates that there is some scarred or undercured remain. 2.The surface hardness is by Shore D. 3.Unit is mm. The fact that a smaller ± range is obtained with the inventive product indicates that the inventive pultrusion is superior in regenerating a given shape of a die or mold section. Example 3 In Fig. 2 embodiment, polyethylene (PE) roving was used as replacement for glass roving in the foregoing. Coating material; ester acrylate (brandnamed ARONIX M6100 by TOA GOSEI CO.) 100 parts. UV sensitizer; (benzildimethyl ketal, brandnamed IRGACURE 651 by CIBA-GEIGY) 4 parts. Mold; stainless, circular section, dia. = 1.5 mm. Medium liquid; water. Pultrusion speed; 5 m/min. Finished rod has superior quality. Example 4 The double port die, of which tip portion is as shown in Fig. 4, was used to mold a skin/core structured rod. Such structure formation is useful to further improve a surface look of the finished rod. Production of skin/core structured rod will dispense with an after-finish job of top coating on the pultruded rods. Industrial Applicability The present invention will be applied to produce rod, pole, rope products etc., when it comes to non-cut products, it may be a lengthy rope, which will be used as, for instance, a rope for exploring a deep sea bottom; a retainer rope or tension member for a bundle of data transmission fibers to be set for a long distance.

Claims: A method of pultrusion for continuously producing a reinforced profile having a desired cross-section comprising the following steps: a) impregnating a continuous reinforcing material (1) with a UV-curable resin (2), b) pulling the impregnated continuous reinforcing material (1) through a pipe die (4) having a cross-section corresponding to' the cross-section of the product to be obtained, the die (4) being made of a material capable of transmitting UV-rays and which is provided on its inner surface with a material capable of transmitting UV-rays and which resists sticking with the UV-curable resin, and c) irradiating the impregnated continuous reinforcing material (1) during its passage through the die (4) with the UV-rays to substantially cure the UV-curable resin. Method according to claim 1, characterized in that a pipe die (4) is made of glass. Method according to claim 1 or 2, characterized in that a material which is capable of transmitting UV-rays and which resists sticking with the UV-curable resin is a silicon or fluorine based compound or resin. A method of pultrusion for continuously producing a reinforced profile having a desired cross-section comprising the following steps: a) moving a resinous reinforcing material (1) through a pipe die (4) having a length insufficient to effect the cure, but sufficient to effect a shaping of the resinous material (1) to be cured corresponding to the cross-section of the die (4), b) introducing the material (1) into a liquid medium (6) capable of transmitting UV-rays and also immiscible with the resin being cured, and c) exposing the material (1) to UV-radiation during passage in the liquid medium (6). Method according to claim 4, characterized in that the pipe die (4) is made of a UV-absorptive material. Method according to claim 4, characterized in that the pipe die (4) is connected with a die portion capable of transmitting UV-rays and which is provided on its inner surface with a material capable of transmitting UV-rays and which resists sticking with the UV-curable resin. Method according to any of claims 4 to 6, characterized in that the pultrusion is conducted vertically upward or horizontally. Method according to any of claims 4 to 7, characterized in that the liquid medium (8) is water or silicone oil. Method according to any of claims 4 to 8, characterized in that the pipe die (4) is of a double-port type to form a skin/core structured product. Method according to any of claims 1 to 9, characterized in that the pipe die (4) has a circular section or a profiled non-circular section. An apparatus for pultrusion comprising: a) means (2a) for impregnating a continuous reinforcing material (1) with a UV-curable resin (2), b) a pipe die (4) for receiving the continuous reinforcing material (1) impregnated with the UV-curable resin and for curing the resin, said pipe die (4) having a cross-section corresponding the cross-section of the product to be obtained, being made of a material capable of transmitting UV-rays, and being provided on its inner surface with a material capable of transmitting UV-rays and being resistant to sticking with the UV-curable resin, c) means (5) for irradiating the pipe die (4) with UV-rays, d) means for pulling the impregnated continuous material (1) through the pipe die (4). A pultrusion apparatus comprising: a) means (2a) for impregnating a continuous reinforcing material (1) with a UV-curable resin (2), b) a pipe die (4) for receiving the impregnated continuous reinforcing material (1), said pipe die (4) having a length insufficient to effect cure, of the UV-curable resin but sufficient to effect shaping of the impregnated continuous reinforcing material (1), c) a liquid medium (6) being capable of transmitting UV-rays and being immiscible with the UV-curable resin, d) means (5) for irradiating the liquid medium (6) with UV-rays, and e) means for moving the impregnated continuous reinforcing material (1) through the pipe die (4) and the liquid medium (6). Apparatus according to claim 11 or 12, characterized in that the pipe die (4) is made of glass. Apparatus according to any of claims 11 to 13, characterized in that the pipe die (4) has a circular or a profiled non-circular section. Apparatus according to any of claims 11 to 14, characterized in that the die (4) is a double port die which forms a skin/core structure.

Inventors: KANZAKI, TAKASHI
Applicants: TOYO BOSEKI KABUSHIKI KAISHA, TOYO CLOTH CO., LTD.
Application year: 1988
Main classification: B29C35
IPC codes: B29C35, B29C70, B29L31, C08J5, B29C67, B29K105