GB2604615A

GB2604615A - Apparatus and method for prepreg

Info

Publication number: GB2604615A
Application number: GB2103258.6A
Authority: GB
Inventors: Jonathan Whitham Andrew
Original assignee: Cygnet Texkimp Ltd
Current assignee: Cygnet Texkimp Ltd
Priority date: 2021-03-09
Filing date: 2021-03-09
Publication date: 2022-09-14
Anticipated expiration: 2041-03-09
Also published as: GB2604615B; GB202103258D0

Abstract

A double belt press 300 for prepreg fabrication, comprising: a pair of endless belts 310, 320 arranged to form a pair of adjacent runs, wherein each belt comprises a self-releasing outer surface 314, 324 and an inner surface 316, 326, a processing passage 330 defined between the outer surfaces; and a heating zone (302, fig 3) comprising a first pair of rollers (340, fig 3) configured to engage the inner surfaces of the endless belts to press together and heat the adjacent runs. The first pair of rollers may comprise a first hard roller (342, fig 3) and a first soft roller (344, fig 3), wherein the first hard roller may be actively heatable and the first soft roller is not heatable. The heating zone may comprise a first heater (381, fig 3) at the inner surface of the first endless belt. A cooling zone (304, fig 3) may comprise a pair of coolers (392, 394, fig 3), each cooler may comprise a water-cooled plate. The belts may comprise polytetrafluoroethylene forming the self-releasing outer surface. A doctor blade (3100, fig 4) and a solvent applicator (3200, fig 4) may remove residue. A method of prepreg fabrication is also provided.

Description

APPARATUS AND METHOD FOR PREPREG

FIELD

[1] The present disclosure relates in general to an apparatus and a method for processing of fibrous materials and particularly to an apparatus and a method for prepreg fabrication.

BACKGROUND

[2] A prepreg is a reinforcing material that may be applied to a structure and cured thereon to make a reinforced structure. Fabrication of a prepreg involves fully impregnating a fibrous material with a polymer resin, such that the polymer resin is distributed substantially uniformly over the outer surfaces of the fibrous material as well as throughout the fibrous material. According to some known prepreg fabrication processes, the polymer resin is transferred onto the fibrous material utilising a transfer sheet, which may also be also known as a 'release sheet'. The polymer resin is first applied onto the transfer sheet and is subsequently transferred from the transfer sheet onto the fibrous material.

SUMMARY

[3] Known transfer sheets comprise a paper base with a coating thereon. The coating provides a self-releasing surface, i.e. a 'non-stick' surface, to prevent residue of polymer resin on the transfer sheet upon removal from the fibrous material following impregnation. Examples of suitable coatings may include silicone, paraffin or polytetrafluoroethylene. However, these transfer sheets are not recyclable as a result of the coating. Known processes therefore rely on the transfer sheets as a non-recyclable consumable, making these processes resource-intensive and wasteful.

[4] Furthermore, removal of the transfer sheet from the prepreg may cause defects in the resin-coated surface of the prepreg. Although the transfer sheet is silicone-coated, individual segments of resin are known to adhere to the transfer sheet such that upon removal of the transfer sheet defects may occur.

[5] Hence an alternative apparatus and method for prepreg fabrication is highly desirable. According to the present disclosure there is provided an apparatus and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

[6] According to an example, there is provided a double belt press for prepreg fabrication. The double belt press comprises a pair of endless belts arranged to form a pair of adjacent runs. Each belt of the pair of endless belts comprises an outer surface and an inner surface. The outer surface is provided to be self-releasing, i.e. 'non-stick'. A processing passage is defined between the self-releasing outer surfaces along the adjacent runs. A heating zone is defined, which comprises a first pair of rollers configured to engage the inner surfaces of the endless belts to press together and heat the adjacent runs.

[7] The double belt press is operable without transfers sheets, thereby removing the need for this consumable in the fabrication process. Moreover, it follows that the double belt press does not require a complex paper feed/un-feed system, thereby simplifying the double belt press and reducing cost in both components and operation.

[8] The first pair of rollers may comprise a first hard roller and a first soft roller. The first hard roller comprises a first hard roller surface, while the first soft roller comprises a first soft roller surface. The first hard roller is harder than the first soft roller surface. The double belt press may be equipped with different configurations of rollers and is not restricted to a "chrome-only" setup, i.e. a configuration of exclusively chrome rollers, as may be the case for certain conventional systems. Thus, flexibility may be improved and cost reduced without impairing operation.

[9] The first hard roller may be actively heatable. The first soft roller may not be actively heatable.

[10] The endless belts may be arranged to converge at the first pair of rollers to form an entry for receiving fibrous material into to the processing passage.

[11] The heating zone may comprise a second pair of rollers provided along the adjacent runs. Thus, further heating may be provided. The second pair of rollers may be configured to engage the inner surfaces of the endless belts to press together and heat the adjacent runs.

[12] The second pair of rollers may comprises a second hard roller and a second soft roller. The second hard roller comprises a second hard roller surface and the second soft roller comprises a second soft roller surface. The second hard roller surface is harder than the second soft roller surface. As set out above with reference to the first pair of rollers, flexibility may thus be improved and cost reduced without impairing operation.

[13] The second hard roller may be actively heatable. The second soft roller may not be actively heatable.

[14] The double belt press may comprise exactly two pairs of rollers configured to press together the adjacent runs, i.e. no further rollers configured to press together the adjacent runs than the first pair and the second pair of rollers. The double belt press may be operable with exactly two pairs of compression rollers, whereas conventional means for prepreg fabrication may require at least three pairs of compression rollers.

[15] The heating zone may comprise a first heater at the inner surface of the first endless belt. The first heater may be located between the first pair of rollers and the second pair of rollers. Thus, further heating may be provided, for example in order to improve maintaining of operational temperature within the processing passage.

[16] The heating zone may comprise a second heater at the inner surface of the second endless belt. The second heater may be located between the first pair of rollers and the second pair of rollers. The second heater may be provided in addition to the first heater or as an alternative to the heater. Where the first heater and the second heater are provided, i.e. a dual-heater configuration is provided, this may further improve maintaining of operating temperature particularly where the endless belts are of considerable thickness, e.g. thickness in a range of 0.5 millimetres to 1 millimetre or more.

[17] At least one of the first heater and the second heater may be displaceable between a first heater position and a second heater position. In the first heater position, the respective heater is not in contact with the respective inner surface. In the second heater position, the respective heater is in contact with the respective inner surface. Thus, an "ironing" effect may be achieved by engaging the belt with the heater to further improve heat transfer. Unlike for certain existing systems, engaging the belt with the heater may not adversely affect performance, for example as a result of a change in belt geometry.

[18] The double belt press may further comprise a first pair of deflection rollers. The endless belts are arranged to converge from the first pair of deflection rollers towards the first pair of rollers.

[19] The heating zone may comprise a pair of pre-heaters located between the first pair of deflection rollers and the first pair of rollers. The pair of pre-heaters is arranged to extend along the belts without contacting the belts and configured to heat the belts. A single pre-heater may alternatively be provided. By providing at least one pre-heater, further heating may be achieved particularly for purposes of raising the temperature towards operational temperature.

[20] The double belt press may comprise a second pair of deflection rollers. The endless belts diverge at the second pair of deflection rollers, thereby defining an exit of the processing passage.

[21] A cooling zone comprising a pair of coolers may be located between the hot zone and the second pair of deflection rollers. A first cooler of the pair of coolers may be located at the inner surface of the first endless belt. A second cooler of the pair of coolers may be located at the inner surface of the second endless belt. Alternatively either the first cooler or the second cooler may be provided. The cooling section of the belt press may lower the temperature of the endless belts. Depending on the materials and resins being processed, the cooling effect may be adjusted to suit the process.

[22] At least one of the first cooler and the second cooler may be displaceable between a first cooler position and a second cooler position. In the first cooler position, the respective cooler is not in contact with the respective inner surface. In the second cooler position, the respective cooler is in contact with the respective inner surface. Similar to the heaters engaging the endless belts for an ironing effect, heat transfer may be improved by causing the cooler to engage the belt. Unlike for certain existing systems, engaging the belt with the cooler may not adversely affect performance.

[23] At least one of the first cooler and the second cooler may comprises a water-cooled plate extending along and configured to cool the adjacent runs.

[24] The endless belts may comprise polytetrafluoroethylene forming the self-releasing outer surface. A durable and temperature-resistant solution may be provided utilising endless belts made of PTFE with a support fabric. Such belts may be more durable than a silicone-coated belt.

[25] The heating zone may be configured to reach an operating temperature of up to 300 degrees Celsius.

[26] The first endless belt may have a thickness of at least 0.5mm. The first belt may have a thickness of up to 1.2 millimetres.

[27] The second endless belt may have a thickness of at least 0.5mm. The second belt may have a thickness of up to 1.2 millimetres.

[28] The double belt press may comprise a doctor blade extending across the outer surface of the first belt or the outer surface of the second belt. The doctor blade is configured to engage the respective outer surface and remove therefrom residue carried thereon. A doctor blade may be provided for each endless belt. Such cleaning means may improve performance over prolonged time periods, for example where the self-releasing property of the endless belts diminishes.

[29] The double belt press may comprise an applicator configured to apply a solvent onto the outer surface of the first endless belt or the second endless belt and remove therefrom residue carried thereon. An applicator may be provided for each endless belt. Such cleaning means may improve performance over prolonged time periods, for example where the self-releasing property of the endless belts diminishes.

[30] There is provided a method of prepreg fabrication. The method comprises providing a pair of endless belts arranged to form a pair of adjacent runs. The method further comprises revolving the pair of endless belts to co-directionally drive the adjacent runs. The method further comprises feeding a fibrous material and a polymer resin into a processing passage defined between self-releasing outer surfaces of the endless belts along the adjacent runs, thereby causing the pair of endless belts to engage the fibrous material and the polymer resin. The method further comprises passing the fibrous material between a first pair of rollers configured to heat and press together the adjacent runs, thereby heating and compressing the fibrous material to cause the polymer resin to fully impregnate the fibrous material. The method further comprises releasing the fibrous material from an exit of the processing passage, the pair of endless belts diverging at the exit of the processing passage and the self-releasing outer surfaces of the belts separating from the fibrous material.

[31] The method may further comprise coating the fibrous material with the polymer resin prior to feeding the fibrous material and the polymer resin into the processing passage.

[32] The method may further comprise coating at least one of the endless belts with the polymer resin in order to thereby feed the polymer resin into the processing passage.

BRIEF DESCRIPTION OF DRAWINGS

[33] For a better understanding of the invention, and to show how example embodiments may be carried into effect, reference will now be made to the accompanying drawings in which: Figure 1 is a view of system for prepreg fabrication; Figure 2 is a perspective view of an impregnation station of the system of Figure 1; Figure 3 is a side view of the impregnation station; and Figure 4 is another side view of the impregnation station.

DESCRIPTION OF EMBODIMENTS

[34] The present disclosure relates to an apparatus for fabrication of a prepreg and a method of fabrication of a prepreg. Prepreg is understood to also include towpreg as an example of a narrow prepreg. The apparatus and method are applicable to all suitable fibrous materials, such as nonwovens or fabrics.

[35] Figure 1 is a side view of an example system for fabrication of a prepreg. The system comprises a creel 10, a coating station 20, an impregnation station 30, and an accumulator winder 40. In Figure 1, the fabrication process is from left to right, such that fibrous material 50 is conveyed from the creel 10, through the coating station 20 and the impregnation station 30, and to the accumulator winder 40.

[36] The creel 10 is configured to supply the fibrous material 50. Examples of suitable creels and fibrous materials are known in the art. As regards the fibrous material 50, it is noted that this may comprise a fibre or fabric. Examples of such fibres and fabric include natural and synthetic materials, such as petrochemical-based fibres, metallic, glass or carbon fibres.

[37] The fibrous material 50 is conveyed from the creel 10 to the coating station 20. The coating station 20 is configured to apply a coat of polymer resin 60 to the fibrous material 50. Thus, a surface (or 'major surface') of the fibrous material 50 is coated. Examples of suitable coating stations 20 for coating the fibrous material 50 are known in the art.

[38] The fibrous material 50 is conveyed from the coating station 20 through the impregnation station 30, where an application of heat and compression causes the resin applied to the fibrous material 50 to liquify and permeate the fibrous material 50. Thus, resulting in full impregnation of the fibrous material 50, i.e. embedding the fibrous material 50 in the resin. It is noted that full impregnation may be achieved without relying on non-recyclable transfer sheets.

[39] The fibrous material 50 is conveyed from the impregnation station 30 to the accumulator winder 40 configured to wind the fibrous material 50 for storage. Examples of suitable accumulator winders are known in the art.

[40] Figure 2 is a side view of the impregnation station 30. The impregnation station 30 comprises a double belt press 300 configured to process the fibrous material 50. In particular, the double belt press 300 is configured to heat and compress the fibrous material 50, thereby liquifying resin applied to the fibrous material 50 and pressing said resin into the fibrous material 50.

[41] The double belt press 300 comprises a pair of endless belts 310, 320, i.e. a first endless belt 310 and a second endless belt 320. The endless belts 310, 320 (or 'conveyor belts' or 'revolving belts') are closed loops configured to revolve on predetermined closed paths.

[42] Each belt 310, 320 comprises an outer surface 314, 324 and an inner surface 316, 326. The outer surface 314, 324 and the inner surface 316, 326 correspond to a pair of major surfaces the belt, i.e. the opposite sides of the belt 310, 320. The outer surface 314, 324 is a first major surface of the belt 310, 320 and faces away from a region enclosed by the belt 310, 320. The inner surface 316, 326 is a second major surface of the belt 310, 320 and faces the region enclosed by the belt 310, 320.

[43] The pair of endless belts 310, 320 is arranged to form a pair of adjacent runs 318, 328. More particularly, a first run 318 of the first endless belt 310 and a second run 328 of the second endless belt 320 are arranged parallel and in opposition. Thus, the outer surfaces 314, 324 of the adjacent runs 318, 328 are mutually opposing, i.e. face each other.

[44] A processing passage 330 is defined between the adjacent runs 318, 318. In Figure 2, the adjacent runs 318, 318 are illustrated as spaced apart, but in use the adjacent runs 318, 318 may be contacting each other. The endless belts 310, 320 are configured to revolve such that the adjacent runs 318, 328 are driven co-directionally, i.e. into the same direction. Hence a conveyor direction 331 is defined. In Figure 2, the conveyor direction 331 is indicated by a corresponding arrow. The belts 310, 320 converge at an entry 332 to the processing passage 330 and diverge at an exit 334 of the processing passage 330. The fibrous material 50 enters the processing passage 330 at the entry 332 (or 'material entry') and leaves the processing passage 330 at the exit 334 (or 'material exit'). With respect to the conveyor direction 331, the entry 332 is an 'upstream' end of the processing passage 330 while the exit 334 is a 'downstream' end of the processing passage 330.

[45] In use, the fibrous material 50 is conveyed through the processing passage 330 in the conveyor direction 331. The fibrous material 50 being passed through the processing passage 330 is exposed to heat and compression, thereby melting the resin carried on the fibrous material 50 and forcing the resin into the fibrous material 50. Subsequently the resin is hardened by being cooled before exiting the processing passage 330. Suitably the double belt press 300 comprises a plurality of rollers 340, 350, 360, 370 and heat exchangers 380, 390 configured to compress, heat and cool the fibrous material 50. According to the present example, the rollers and heat exchangers extend across the whole width of the endless belts 310, 320.

[46] Figure 3 is a side view of the double belt press of Figure 2.

[47] The belt press 300 is generally divided into a heating zone 302 and a cooling zone 304. With respect to the conveyor direction 331, the heating zone 302 is located 'upstream' and the cooling zone 304 is located 'downstream'. Accordingly, the fibrous material 50 conveyed through the belt press 300 is first conveyed through the heating zone 302 and subsequently conveyed through the cooling zone 304.

[48] The heating zone 302 is configured to raise the temperature of the belts 310, 320 to an operating temperature and to maintain said operating temperature. When conveying the fibrous material 50 through the belt press 300, heat is transferred from the belts 310, 320 to the fibrous material 50, thereby heating and ultimately liquefying the fibrous material 50 and the resin carried thereon.

[49] The heating zone 302 comprises multiple pairs of rollers 340, 350, 360 and multiple pairs of heaters 380. The heaters and at least some of the rollers are configured to heat the endless belts 310, 320 and so transfer heat to the fibrous material 50 being conveyed through the processing passage 330. Suitably the rollers and the heaters are located on the inside of the endless belts 310, 320, i.e. configured to heat the inner surfaces 316, 326 of the belts 310, 320.

[50] A first pair of rollers 340 is provided at the entry 332 to the processing passage 330. The first pair of rollers 340 is configured to cause heating and compression of the fibrous material 50 conveyed through the processing passage 50. A pair of rollers configured to heat and compress is also referred to as a pair of heated compression rollers or calendaring rollers.

[51] The first pair of rollers 340 engages the inner surfaces 316, 326 of the endless belts 310, 320 at the entry 332 to the processing passage 330. More particularly, the first pair of rollers 340 comprises a first upper roller 342 and a first lower roller 344. The first upper roller 342 is configured to engage the inner surface 316 of the first endless belt 310, while the first lower roller 344 is configured to engage inner surface 318 of the second endless belt 320.

[52] The first pair of rollers 340 is further configured to press the endless belts 310, 320 together, i.e. configured to 'compress' or 'compact'. Suitably, the first upper roller 342 and the first lower roller 344 are configured to press against each other, thereby pressing together the endless belts 310, 320 extending between the first pair of rollers 340.

[53] The first pair of rollers 340 is further configured to heat the endless belts 310, 320. Suitable at least one of the first upper roller 342 and the first lower roller 344 is heated. According to the present example, the first upper roller 342 is heated.

[54] The first pair of rollers 340 is configured to cause the endless belts 310, 320 to converge, thereby defining the entry 332 to the processing passage 330.

[55] A second pair of rollers 350 is provided along the processing passage 330, 'downstream' from the first pair of rollers 340. That is to say, in use the endless belts 310, 320 move from the first pair of rollers 340 towards the second pair of rollers 350. The second pair of rollers 350 is arranged similar to the first pair of rollers 350, in that the second pair of rollers 350 is configured to engage the inner surfaces 316, 326 of the adjacent runs 318, 328 to heat and press together the adjacent runs 318, 328. More particularly, a second upper roller 352 is configured to engage the inner surface 316 of the first endless belt 310, while a second upper roller 354 is configured to engage inner surface 318 of the second endless belt 320. The second upper roller 352 and the second lower roller 354 are configured to press against each other, thereby pressing together the endless belts 310, 320 extending between the second pair of rollers 350.

[56] The second pair of rollers 350 is further configured to heat the endless belts 310, 320. Suitable at least one of the second upper roller 352 and the second lower roller 354 is heated. According to the present example, the second upper roller 352 is heated.

[57] A third pair of rollers 360 is provided 'upstream' from the first pair of rollers 340. In other words, the first pair of rollers 340 is located between the second pair of rollers 350 and the third pair of rollers 360. In use, the endless belts 310, 320 move from the third pair of rollers 360 towards the first pair of rollers 340. The third pair of rollers 360 is arranged to engage the inner surfaces 316, 326 of the endless belts 310, 320 in order to deflect the endless belts 310, 320. A third upper roller 362 of the third pair of rollers 360 is configured to deflect the first endless belt 310, while a third lower roller 364 of the third pair of rollers 360 is configured to deflect the second endless belt 320. The third pair of rollers 360 may also be referred to as a pair of deflection rollers.

[58] A pair of heaters 381, 382 is provided along the processing passage 330. The pair of heaters 381, 382 is provided the entry 332 to the processing passage 330 and the exit 334 of the processing passage 330. More particularly, the pair of heaters 381, 382 is located between the first pair of rollers 340 and the second pair of rollers 350.

[59] An upper heater 381 (or 'first heater') of the pair of heaters is located at the inner surface 316 of the first endless belt 310. Similarly, a lower heater 382 (or 'second heater') of the pair of heaters is located at the inner surface 326 of the second endless belt 320. The lower heater 382 and the upper heater 381 are located between the first pair of rollers 340 and the second pair of rollers 350.

[60] The heaters 381, 382 are arranged to extend along the adjacent runs 318, 328. That is to say, the upper heater 381 is provided inside the first belt 310 and faces the inside surface 316 of the first belt 310. The lower heater 382 is provided inside the second belt 320 and faces the inside surface 326 of the second belt 320. The heaters 381, 382 are spaced apart from the endless belts 310, 320. In particular, the first heater 381 is spaced apart from the inside surface 316 of the first belt 310 and the second heater 382 is spaced apart from the inside surface 326 of the second belt 320. Hence, the heaters 381, 382 are configured to heat the adjacent runs 318, 328 without contacting the adjacent runs 318, 328.

[61] A pair of pre-heaters 383, 384 is provided between the third pair of rollers 360 and the first pair of rollers 340. The pair of pre-heaters 383, 384 is arranged similar to the pair of heaters 381, 382. In particular, an upper pre-heater 383 (or 'first pre-heater') of the pair is provided inside the first belt 310, facing the inside surface 316 of the first belt 310. A lower pre-heater 384 (or 'second pre-heater') of the pair is provided inside the second belt 320, facing the inside surface 326 of the second belt 320. The pre-heaters 383, 384 are spaced apart from the endless belts 310, 320, with the upper pre-heater 383 spaced apart from the inside surface 316 of the first belt 310 and the lower pre-heater 384 spaced apart from the inside surface 326 of the second belt 320.As shown in Figure 3, the pair of pre-heaters 383, 384 is configured to heat the endless belts 310, 320 without contacting the endless belts 310, 320.

[62] The cooling zone 304 follows the heating zone 302. The cooling zone 304 is configured to lower the temperature of the belts 310, 320. When conveying the fibrous material 50 through the belt press 300, heat is transferred from the fibrous material 50 and the resin to the belts, thereby cooling the fibrous material 50 and the resin.

[63] The cooling zone 304 comprises a cooler 390 and a fourth pair of rollers 370. The cooler 390 is provided between the hot zone 302 and the fourth pair of rollers 370. The cooler 350 extends along the pair of adjacent runs 318, 328 and is configured to draw heat from the belts 310, 320, thereby cooling the fibrous material 50 and the resin conveyed through the processing passage 330.

[64] The cooler 390 comprises a pair of coolers 392, 394. A first cooler 392 is provided inside the first belt 310 and a second cooler 394 is provided inside the second belt 320. The first cooler 392 faces the inside surface 316 of the first belt 310 without contacting said inside surface 316, while the second cooler 394 faces the inside surface 326 of the second belt 320 without contacting said inside surface 326.

[65] The fourth pair of rollers 370 is located 'downstream' of the cooler 390 and defines the exit 334 of the processing passage 330, causing the endless belts 310, 320 to diverge on their return trip to the entry 332. Thus, the endless belts 310, 320 move from the fourth pair of rollers 370 towards the third pair of rollers 360. More particularly, a fourth upper roller 372 of the fourth pair of rollers 370 is configured to deflect the first endless belt 310, while a fourth lower roller 374 of the fourth pair of rollers 370 is configured to deflect the second endless belt 320. The fourth pair of rollers 370 may also be referred to as a second pair of deflection rollers.

[66] According to the present example, the fourth pair of rollers 370 is not configured to press together the adjacent runs 318, 328, i.e. is not a pair of compression rollers.

[67] Figure 4 is another side view of the impregnation station 30.

[68] The first upper roller 342 is provided as a hard roller 342, while the first lower roller 344 is provided as a soft roller 344. For example, the hard roller 342 may be a chrome roller and the soft roller 344 may be a rubber roller. Similarly, the second upper roller 352 is provided as a hard roller 352, while the second lower roller 354 is provided as a soft roller 354. The hard roller 342, 352 defines a first roller surface 343, 353 which is harder than a second roller surface 345, 355 of the soft roller 344, 354. That is to say, pressing together the hard roller 342, 352 and the soft roller 344, 354 may cause the first roller surface 343, 353 to deform the second roller surface 345, 355.

[69] The soft roller 344, 354 is resiliently deformable. That is to say, the soft roller 344, 354 is deformable from an initial shape to a deformed shape and biased to reassume the initial shape.

[70] The first upper roller 342 and the second upper roller 352 are heated, i.e. actively heated, whereas the first lower roller 344 and the second lower roller 354 are not actively heated. It is therefore understood that the first pair of rollers 340 or the second pair of rollers 350 being configured to heat the processing passage 330 requires at least one of the rollers of the pair 340, 350 to be heated. According to the present example, the upper rollers 342, 352 are heated. It is further noted that the lower rollers 344, 354 may in use nevertheless reach an elevated temperature as a result of the heated upper rollers 342, 352.

[71] The upper heater 381 is displaceable between a first position 385 (or 'first heater position') and a second position 386 (or 'second heater position). In the first position 385, the upper heater 381 is spaced apart from the inner surface 316 and is not in engagement with the inner surface 316 of the first endless belt 310. In the second position 386, the upper heater 381 is in engagement with the inner surface 316 of the first endless belt 310.

[72] The upper pre-heater 383 is displaceable between a first position 387 (or 'first pre-heater position') and a second position 388 (or 'second pre-heater position'). In the first position 387, the upper pre-heater 383 is spaced apart from the inner surface 316 and is not in engagement with the inner surface 316 of the first endless belt 310. In the second position 388, the upper pre-heater 383 is in engagement with the inner surface 316 of the first endless belt 310.

[73] The first cooler 392 is displaceable between a first position 396 and a second position 398. In the first position 396, the first cooler 392 is spaced apart from the inner surface 316, i.e. is not in engagement with the inner surface 316 of the first endless belt 310. In the second position 398, the first cooler 392 is in engagement with the inner surface 316 of the first endless belt 310.

[74] The impregnation station 30 comprises means for cleaning of the endless belts 310, 320. In particular, the impregnation station 30 may be provided with mechanical cleaning and/or chemical cleaning. According to the present example, the first endless belt 310 is provided with mechanical cleaning while the second endless belt 320 is provided with chemical cleaning.

[75] The impregnation station 30 comprises a doctor blade 3100. The doctor blade 3100 is configured to engage the outer surface 314 of the first endless belt 310 at a suitable location. More particularly, the doctor blade 3100 is configured to scrape away any resin deposits from the endless belt 310.

[76] The impregnation station 30 comprises an applicator 3200, such as an open-cell foam, with a suitable solvent for removal of the resin used. The applicator 3200 is configured to apply the solvent to the outer surface 324 of the second endless belt 320 at a suitable location. The applicator 3200 is configured to chemically dissolve and retain resin residue carried on the endless belt 320.

[77] In operation, the endless belts 310, 320 are driven by one or more pairs of driving rollers. According to the present example, the endless belts 310, 320 are driven by the fourth pair of rollers 370. The fourth pair of rollers 370 is configured to co-directionally drive the adjacent runs 318, 328 of the belts 310, 320 and at the same speed, i.e. revolve synchronously.

[78] The heating zone 302 is configured to reach an operating temperature of up to 300 degrees Celsius, which may be chosen in view of the properties of the resin. According to the present example, the endless belts 310, 320 are made from PTFE with a suitable support fabric and hence able to withstand temperatures of up to 300 degrees Celsius.

[79] The fibrous material 50 is conveyed towards the entry 332 of the processing passage 330. Already at this point the fibrous material 50, as well as the resin carried thereon, is being heated by means of the belts 310, 320 that are heated by the pre-heaters 383, 384.

[80] Upon passage of the entry 332 to the processing passage 330, the fibrous material 50 and the resin are being compressed and heated by the belts 310, 320 that are being pressed together and heated by the first pair of rollers 340. Continuing along the processing passage 330, the fibrous material 50 passes the pair of heaters 381, 382 configured to maintain the fibrous material 50 and the resin at an elevated temperature. The fibrous material 50 passes through the second pair of rollers 350 which again compress and heat the fibrous material 50 and the resin.

[81] The fibrous material 50 then enters the cooling zone 304. The cooling zone 304 is configured to actively lower the temperature of the fibrous material 50 and the resin. According to the present example, the cooling zone 304 utilises active cooling by means of the water-cooled plates 392, 394.

[82] Finally, the fibrous material 50 exists the processing passage 330 at the exit 334 where the belts 310, 320 are separated from the fibrous material 50 and the resin. By this point, the temperature of the fibrous material 50 and the resin has been lowered sufficiently such that the self-releasing outer surfaces of the belts 310, 320 can release the fibrous material 50 such that defects may be minimised.

[83] The belts 310, 320 may be made from any material or combination of materials providing a suitable self-releasing property. For example, a suitably treated stainless steel belt may be utilised. According to the present example, the belts 310, 320 are made from polytetrafluoroethylene, also known as PTFE, with a support fabric.

[84] Depending on the choice of belt material, the heating zone 302 may be configured to reach temperatures of up to 300 degrees Celsius. Particularly where PTFE is utilised, the endless belts 310, 320 may be operable at such an operational temperature without diminishing the self-releasing property of the endless belts 310, 320.

[85] The belts 310, 320 according to the present example have a thickness of approximately 1 millimetre. More generally, the belts 310, 320 may have a thickness in a range of 0.5 millimetres and 1.5 millimetres.

[86] According to the present example, the coolers 392, 394 comprise water-cooled plates 392, 394.

[87] According to the present example, the applicator 3200 is configured to apply acetone.

[88] According to the example described above, the fibrous material 50 is provided from the creel 10. According to other examples, different sources of fibrous material may be utilised, for example a driven fabric unwind for rolls of woven material.

[89] According to the example described above, the prepreg is wound by the accumulator winder 40 for storage. According to other examples, the process is fed directly into further manufacturing steps without being wound for storage.

[90] The third pair of rollers 360 may be (actively) heated, but according to the present example is not provided as heated.

[91] The upper heater 381 is configured to engage and disengage the first endless belt 310 by displacing the upper heater 381 towards the second position 386 and the first position 385, respectively. According to other examples, the lower heater 382 is displaceable between a first position 385 and a second position 386 to engage/disengage the second belt 320. According to yet further examples, both heaters 381, 382 are so configured.

[92] The upper pre-heater 383 is configured to engage and disengage the first endless belt 310 by displacing the upper pre-heater 383 towards the second position 388 and the first position 387, respectively. According to other examples, the lower pre-heater 383 is displaceable between a first position 387 and a second position 388 to engage/disengage the second belt 320. According to further examples, both pre-heaters 383, 384 are so configured.

[93] The first cooler 392 is configured to engage and disengage the first endless belt 310 by displacing the first cooler 392 towards the second position 398 and the first position 396, respectively. According to other examples, the second cooler 394 is displaceable between a first position 396 and a second position 398 to engage/disengage the second belt 320. According to yet further examples, both pre-heaters 381, 382 are so configured.

[94] According to the above example, the coolers 392, 394 are provided as water-coolers. However, any suitable type of cooling may be utilised, such as air-cooling.

[95] According to the example describes above, resin is supplied as a coating on the fibrous material 50. According to other examples, resin may be supplied by alternative means. For example, at least one of the endless belts may be coated with resin, thereby feeding a resin-coated endless belt into the processing passage as opposed to resin-coated fibrous material 50. According to another example, a hot melt sheet is utilised to provide the resin.

[96] In summary, exemplary embodiments of an apparatus and a method of prepreg fabrication have been described. The described exemplary embodiments provide for an improved apparatus and method. Additionally, the described exemplary embodiments are convenient to manufacture and straightforward to use.

[97] The apparatus may be manufactured industrially. An industrial application of the example embodiments will be clear from the discussion herein.

[98] Although preferred embodiment(s) of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made without departing from the scope of the invention as defined in the claims.

Claims

CLAIMS1. A double belt press (300) for prepreg fabrication, the double belt press comprising: a pair of endless belts (310, 320) arranged to form a pair of adjacent runs (318, 328), wherein each belt comprises a self-releasing outer surface (314, 324) and an inner surface (316, 326), a processing passage (330) defined between the self-releasing outer surfaces (314, 324) along the adjacent runs (318, 328), and a heating zone (302) comprising a first pair of rollers (340) configured to engage the inner surfaces (316, 326) of the endless belts (310, 320) to press together and heat the adjacent runs (318, 328).
2. The double belt press according to claim 1, wherein the first pair of rollers (340) comprises a first hard roller (342) and a first soft roller (344), the first hard roller (342) comprising a first roller surface (343) and the first soft roller (344) comprising a second roller surface (345), the first roller surface (343) being harder than the second roller surface (345).
3. The double belt press according to claim 2, wherein the first hard roller (342) is actively heatable and the first soft roller (344) is not activelyheatable.
4. The double belt press according to any preceding claim, wherein the endless belts (310, 320) are arranged to converge at the first pair of rollers (340) to form an entry (332) for receiving fibrous material (50) into to the processing passage (330); and the heating zone (302) comprises a second pair of rollers (350) provided along the adjacent runs (318, 328), the second pair of rollers (350) configured to engage the inner surfaces (316, 326) of the endless belts (310, 320) to press together and heat the adjacent runs (318, 328).
5. The double belt press according to claim 4, wherein the second pair of rollers (350) comprises a second hard roller (352) and a second soft roller (354), the second hard roller (352) comprising a first roller surface (353) and the second soft roller (354) comprising a second roller surface (355), the first roller surface (353) being harder than the second roller surface (355).
6. The double belt press according to claim 5, wherein the second hard roller (342) is actively heatable and the second soft roller (344) is not actively heatable.
7. The double belt press according to claim 4 to 6, wherein the double belt press (300) comprises no further pair of rollers configured to press together the adjacent runs other than the first pair of rollers (340) and the second pair of rollers (350).
8. The double belt press according to any one of claim 4 to 7, the heating zone (302) comprising a first heater (381) at the inner surface (316) of the first endless belt (310), the first heater (381) located between the first pair of rollers (340) and the second pair of rollers (350).
9. The double belt press according to claim 8, the heating zone (302) comprising a second heater (382) at the inner surface (326) of the second endless belt (320), the second heater (382) located between the first pair of rollers (340) and the second pair of rollers (350).
10. The double belt press according to claim 8 or 9, wherein the first heater (381) or the second heater (382) is displaceable between a first heater position (385) and a second heater position (386), in the first heater position (385) the respective heater (381, 382) is not in contact with the respective inner surface (316, 326) and in the second heater position (386) the respective heater (381, 382) is in contact with the respective inner surface (316, 326).
11. The double belt press according to any preceding claim, further comprising: a first pair of deflection rollers (360), wherein the endless belts (310, 320) are arranged to converge from the first pair of deflection rollers (360) towards the first pair of rollers (340), and the heating zone (302) comprising a pair of pre-heaters (383, 384) located between the first pair of deflection rollers (360) and the first pair of rollers (340), the pair of pre-heaters (383, 384) arranged to extend along the belts (310, 320) without contacting the belts (310, 320) and configured to heat the belts (310, 320).
12. The belt press according to any preceding claim, further comprising a second pair of deflection rollers (370), wherein the endless belts (310, 320) diverge at the second pair of deflection rollers (370), thereby defining an exit (334) of the processing passage (330); and a cooling zone (304) comprising a pair of coolers (392, 394) between the hot zone (340) and the second pair of deflection rollers (370), a first cooler (392) of the pair of coolers at the inner surface (316) of the first endless belt (310), a second cooler (394) of the pair of coolers at the inner surface (326) of the second endless belt (320).
13. The double belt press according to claim 12, wherein the first cooler (392) or the second cooler (394) is displaceable between a first cooler position (396) and a second cooler position (398), in the first cooler position (396) the respective cooler (392, 394) is not in contact with the respective inner surface (316, 326) and in the second cooler position (398) the respective cooler (392, 394) is in contact with the respective inner surface (316, 326).
14. The belt press according to claim 12 or 13, wherein each cooler (392, 394) comprises a water-cooled plate (392, 394) extending along and configured to cool the adjacent runs (318, 328).
15. The belt press according to any preceding claim, wherein the belts (310, 320) comprise polytetrafluoroethylene forming the self-releasing outer surface (314, 324).
16. The belt press according to any preceding claim, wherein the heating zone (302) is configured to reach an operating temperature of up to 300 degrees Celsius.
17. The double belt press according to any preceding claim, wherein the first endless belt (310) has a thickness of at least 0.5mm, and the second endless belt (320) has a thickness of at least 0.5mm.
18. The double belt press according to any preceding claim, further comprising a doctor blade (3100) extending across the outer surface (314) of the first belt (310) or the outer surface (324) of the second belt (320), the doctor blade (3100) configured to engage the respective outer surface (314, 324) and remove therefrom residue carried thereon.
19. The double belt press according to any preceding claim, further comprising an applicator (3200) configured to apply a solvent onto the outer surface of the first belt or the second belt and remove therefrom residue carried thereon.
20. A method of prepreg fabrication, the method comprising: providing a pair of endless belts arranged to form a pair of adjacent runs, revolving the pair of endless belts to co-directionally drive the adjacent runs, feeding a fibrous material and a polymer resin into a processing passage defined between self-releasing outer surfaces of the endless belts along the adjacent runs, thereby causing the pair of endless belts to engage the fibrous material and the polymer resin, passing the fibrous material between a first pair of rollers configured to heat and press together the adjacent runs, thereby heating and compressing the fibrous material to cause the polymer resin to fully impregnate the fibrous material, releasing the fibrous material from an exit of the processing passage, the pair of endless belts diverging at the exit of the processing passage and the self-releasing outer surfaces of the belts separating from the fibrous material.
21. The method according to claim 20, further comprising: coating the fibrous material with the polymer resin prior to feeding the fibrous material and the polymer resin into the processing passage.
22. The method according to claim 20, further comprising: coating at least one of the endless belts with the polymer resin in order to thereby feed the polymer resin into the processing passage.