Production system for preparing thermoplastic prepreg by slurry method

Abstract

The present invention discloses a production system for preparing thermoplastic prepreg by a slurry method, comprising: a sizing agent removal device, a dipping tank, a drying device, a pultrusion die and a winding device arranged along the direction of fiber travel, the dipping tank being connected to a slurry concentration regulating device, the slurry concentration regulating device comprising: a buffer barrel, the slurry outlet of the buffer barrel being connected to the slurry inlet of the dipping tank, a reflux pipe for reflux-transporting the slurry in the dipping tank to the buffer barrel being arranged between the buffer barrel and the dipping tank; the buffer barrel being connected to a sample detection pool through a slurry sample delivery pipeline, a viscometer being arranged in the sample detection pool; a high-concentration slurry storage tank connected to the buffer barrel; a slurry dispersion barrel, respectively connected to the buffer barrel and the high-concentration slurry storage tank, for injecting slurry of corresponding concentration into the buffer barrel and the high-concentration slurry storage tank; a raw material tank connected to the slurry dispersion barrel. The production system for preparing thermoplastic prepreg by a slurry method of the present invention can adjust the concentration of the slurry.

Description

Technical Field

[0001] The invention relates to a prepreg production system, in particular to a production system for preparing thermoplastic prepreg by a slurry method. Background Art

[0002] Resin-based composite materials, also known as fiber-reinforced plastics, are composite materials that use organic polymers as the matrix and glass fiber, carbon fiber, basalt fiber or aramid fiber as reinforcement. They are currently widely used in various fields such as life and production. At present, the preparation of thermoplastic prepregs is difficult and the cost is relatively high. Domestic and foreign research institutions and enterprises have successively developed a variety of thermoplastic prepreg preparation processes, such as powder method, film method, fiber hybrid method, solution method, melt extrusion method, in-situ polymerization method, etc.

[0003] At present, the large-scale production of thermoplastic carbon fiber prepreg in my country is in its infancy, the equipment and process are not mature enough, and there is no large-scale thermoplastic carbon fiber prepreg production line that can operate stably. Most of the mature thermoplastic products in the international market are produced by TenCate and Gurit. They use solvent & melt impregnation process and powder melt impregnation process to prepare prepreg, but due to the high equipment price and subsequent maintenance cost, the final product price is high, which affects the popularity of thermoplastic carbon fiber prepreg.

[0004] The preparation of thermoplastic prepreg by mud process is to use the mud method to evenly infiltrate and disperse ultrafine resin powder into the fiber bundle, and heat the fiber to make the resin fully infiltrate the fiber, so as to facilitate the production of prepreg with high melting point and high viscosity resin (such as PEEK). The main technical bottleneck of this process is that the concentration of resin slurry is not controlled: when the fiber passes through the dipping tank, a large amount of resin powder is taken away, resulting in the slurry concentration in the dipping tank gradually becoming thinner with the extension of production time, and the prepreg resin content cannot be kept constant, which directly affects the product quality and continuous industrial production. In addition, there is no resin melt extrusion impregnation roller in the mud method thermoplastic prepreg production line, and the resin melt impregnation fiber is mainly carried out through the pultrusion die. In the prior art, the mold cavity of the pultrusion die is a uniform cross-section, the resin impregnation effect of this type of mold is poor, and the resin is easily accumulated at the mold entrance, which affects the fiber entering the mold and causes damage and breakage. Summary of the invention

[0005] Purpose of the invention: In view of the problems existing in the prior art, the present invention provides a production system for preparing thermoplastic prepreg by a slurry process, which can adjust the concentration of the slurry.

[0006] Technical solution: The production system for preparing thermoplastic prepreg by the slurry method of the present invention comprises: a sizing agent removal device, a dipping tank, a drying device, a pultrusion die and a winding device arranged along the fiber travel direction, the dipping tank is connected to a slurry concentration regulating device, and the slurry concentration regulating device comprises:

[0007] A buffer tank, the slurry outlet of the buffer tank is connected to the slurry inlet of the dipping tank, and a reflux pipe is provided between the buffer tank and the dipping tank for refluxing and transporting the slurry in the dipping tank to the buffer tank; the buffer tank is connected to a sample detection pool through a slurry sample transport pipeline, and a viscometer is provided in the sample detection pool;

[0008] A high-concentration slurry storage tank, connected to the buffer tank for injecting high-concentration slurry into the buffer tank;

[0009] A slurry dispersion tank, connected to the buffer tank and the high-concentration slurry storage tank respectively, for injecting slurries with corresponding concentrations into the buffer tank and the high-concentration slurry storage tank;

[0010] A raw material tank, connected to the slurry dispersion tank for injecting raw materials into the slurry dispersion tank.

[0011] In the production process of thermoplastic prepreg, the fiber first passes through a sizing agent removing device to remove the sizing agent of the fiber during the traveling process, then enters the dipping tank to impregnate the slurry, then enters a drying device to evaporate the moisture, and then enters a pultrusion die for pultrusion and is wound by a winding device. To avoid the problem that the fiber continuously impregnates the slurry resulting in a decrease in the slurry concentration, the present invention provides a slurry concentration adjusting device to adjust the slurry concentration. Two concentrations of slurries are prepared in the slurry dispersion tank: slurry a and slurry b, and the concentration of a > the concentration of b. The concentration of a: 30 - 60%, the concentration of b: 5 - 40%, and the concentrations are all mass percentages. The slurry b is the actual slurry concentration required during the production process, and the viscosity of the slurry at this concentration is measured and transported into the buffer tank. The prepared high-concentration slurry a is transported to the high-concentration slurry storage tank. The slurry b circulates in the dipping tank and the buffer tank, and the viscosity of the slurry in the buffer tank is detected by a viscometer. Once it drops to a certain extent, the high-concentration slurry storage tank injects high-concentration slurry into the buffer tank to adjust the slurry to a suitable concentration.

[0012] Preferably, a liquid level gauge is provided in the buffer tank; mechanical stirrers are provided in the buffer tank, the slurry dispersion tank, and the high-concentration slurry storage tank. When the slurry liquid level in the buffer tank is insufficient, the slurry in the slurry dispersion tank is replenished to the buffer tank. When the slurry liquid level in the slurry dispersion tank is sufficient, the pipeline transportation between the slurry dispersion tank and the buffer tank is closed.

[0013] Slurry circulation transportation is realized between the buffer tank and the dipping tank, and mechanical dispersion in the buffer tank to prevent the slurry from settling during long-term use. At the same time, the slurry concentration in the buffer tank is kept consistent with the slurry concentration in the dipping tank.

[0014] Preferably, the outer wall of the buffer barrel is provided with a heat-insulating jacket; the outer wall of the dipping tank is provided with a heat-insulating jacket. The slurry temperature has a significant effect on the viscosity, especially the temperature change caused by seasonal changes. The heat-insulating jacket plays a heat-insulating role, and the heat-insulating jacket can be connected to a thermostatic water tank to control the temperature at 25±3℃.

[0015] The slurry in the buffer tank keeps flowing and is prone to shaking, so the viscometer test sample needs to be transported separately to a special container, namely the sample test pool, and the container needs to remain relatively still. The slurry liquid to be transported and tested needs to flow slowly into the test sample pool (liquid flow rate <80cc / min), and the liquid level in the sample pool must be stable.

[0016] The production system for preparing thermoplastic prepreg by the slurry method also includes a control module. Automatic control can be achieved to avoid errors caused by manual detection or replenishment of slurry as much as possible. The control module, such as a PLC control module, inputs the slurry control viscosity and the allowable viscosity fluctuation range into the PLC control module, continuously and uninterruptedly extracts the slurry in the buffer glue barrel to the sample detection pool, and timely monitors the change in slurry viscosity. When the viscometer detects that the slurry viscosity is lower than the lower limit, the high-concentration slurry storage tank replenishes the slurry to the buffer glue barrel. When the viscometer detects that the slurry concentration is close to the upper limit, the replenishment of the high-concentration slurry is stopped.

[0017] Preferably, the production system for preparing thermoplastic prepreg by the slurry process further comprises a creel arranged upstream of the sizing agent removal device.

[0018] The pultrusion die comprises:

[0019] The upper mold has a first heating section, wherein the bottom surface of the first heating section includes a first inclined surface and a first flat surface connected to each other;

[0020] A lower mold having a second heating section, wherein a top surface of the second heating section comprises a second inclined surface and a second flat surface connected to each other;

[0021] The first inclined plane and the second inclined plane are arranged opposite to each other, and a V-shaped mold cavity with a V-shaped longitudinal section is formed between the first inclined plane and the second inclined plane or between the planes where the two are located. The first plane and the second plane are basically parallel to form a first uniform cross-section mold cavity, and the narrow mouth of the V-shaped mold cavity is connected to the first uniform cross-section mold cavity.

[0022] In the pultrusion die of the present invention, the fiber impregnated with resin enters from the wide opening of the V-shaped cavity, passes through the V-shaped cavity, and enters the first constant cross-section cavity through the narrow opening of the V-shaped cavity. On the one hand, the V-shaped cavity can reduce the contact area between the fiber and the cavity wall, relieve the friction between the fiber and the die, avoid fiber damage and die blockage. On the other hand, when the fiber impregnated with polymer travels along the cavity, it is always under pressure from the die, and the pressure transmission gradually compacts, which is beneficial to fiber impregnation and elimination of voids in the prepreg. Preferably, the taper of the V-shaped cavity is 0.01-20 degrees, preferably 0.01-10 degrees, which can achieve better impregnation and avoid fiber damage effects.

[0023] The overall length of the die is 250-700 mm to ensure that the resin can be completely melted. Preferably, the horizontal projection lengths of the first inclined surface and the second inclined surface are the same, both being 160-460 mm, which is determined according to the taper size of the V-shaped cavity of the die. The ratio of the die inlet gap to the inclined surface length is equal to the tangent value of the taper. The size of the die length determines the size of the resin impregnation extrusion force and the extrusion time, which can achieve better extrusion impregnation effects; the lengths of the first plane and the second plane are the same, both being 90-240 mm, which has a better shaping effect on the surface of the prepreg, making the surface appearance of the prepreg good and the thickness uniform.

[0024] The first constant cross-section cavity can control the thickness of the prepreg finished product and ensure that the prepreg has a good appearance. A support member is provided between the first plane and the second plane. Through the support of the support member, the first plane and the second plane are substantially parallel to form the first constant cross-section cavity. By adjusting the support height of the support member, the thickness of the prepreg finished product can be adjusted and controlled.

[0025] Heating tubes are provided in both the first heating section and the second heating section. Through the heating of the heating tubes, heat is conducted to the heating section to realize the heating of the fiber. The heating tubes can be heated by electric heating, and the heating temperature is 200-500 °C. The heating tubes are evenly distributed inside the die to ensure the uniformity of the temperature.

[0026] The upper die includes a first cooling section connected to the first heating section, and the lower die includes a second cooling section connected to the second heating section; the bottom surface of the first cooling section has a third plane, the third plane is connected to the first plane and is in the same horizontal plane, and the top surface of the second cooling section has a fourth plane, the fourth plane is connected to the second plane and is in the same horizontal plane.

[0027] The third plane and the fourth plane are substantially parallel to form a second constant cross-section cavity. For temperature-sensitive crystalline polymers, slow cooling makes the resin approach a static isothermal process, which is easy to generate large spherulites, making the product brittle and reducing the mechanical properties. By rapidly cooling and reducing the temperature in the second constant cross-section cavity, the crystallization time of the polymer is reduced, the crystallinity can be reduced, and the impact toughness can be improved.

[0028] Both the first cooling section and the second cooling section are provided with cooling medium flow channels inside. The cooling medium flowing through the cooling medium flow channels cools the second equal - cross - section die cavity, and the cooling medium flow channels are evenly distributed inside the first cooling section and the second cooling section. The cooling medium can be cooling water, and the temperature of the cooling water is controlled at - 20 - 0 °C.

[0029] A first heat insulation plate is provided between the first heating section and the first cooling section, and a second heat insulation plate is provided between the second heating section and the second cooling section; the bottom surface of the first heat insulation plate is in the same horizontal plane as the first plane, and the top surface of the second heat insulation plate is in the same horizontal plane as the second plane. The heat insulation plates are used to separate the heating section from the cooling section to avoid thermal deformation of the mold caused by excessive temperature difference, which affects the accuracy. The cooling section needs to be close to the heating section to facilitate the timely cooling of the prepreg. The thickness of the heat insulation plate is ≥10 mm and ≤30 mm.

[0030] The upper mold and the lower mold are detachably connected, which is convenient for later maintenance, cleaning and gap adjustment.

[0031] Beneficial effects:

[0032] The concentrations of the slurries are different, and their corresponding viscosities are also different. The present invention can judge the change of the slurry content by detecting the slurry viscosity, can more intuitively obtain the usage of the slurry, and the viscosity index is easier to monitor. Based on this, the present invention provides a production system for preparing thermoplastic prepreg by the slurry method, which has a simple structure and strong industrial operability, and ensures the stable resin content during the continuous production of the slurry - method thermoplastic prepreg.

[0033] The viscosity detection is separated from the buffer tank to avoid the influence of mechanical stirring or slurry circulation on the accuracy of the viscometer detection due to shaking. Through the stirring in the buffer tank and the slurry circulation between the buffer tank and the dipping tank, the stable time of the slurry is increased, and the phase separation of heterogeneous substances in a short time is avoided, which affects the fiber resin content.

[0034] By means of high - temperature pyrolysis, the sizing agent on the fiber is removed, thereby improving the adhesion between the resin and the fiber.

[0035] The ultra - fine resin powder is evenly impregnated and dispersed into the fiber bundle by the slurry method, and the resin fully impregnates the fiber by heating through the pultrusion die.

[0036] Design the pultrusion die. High melting point and high viscosity resin can be fully melted through the heating section during the forming process, and the resin melt can uniformly impregnate the fibers through extrusion to reduce the bubble porosity in the prepreg. Through the V-shaped die cavity, the resin and fibers slowly enter and contact the die, avoiding resin accumulation at the die entrance, and at the same time, it can slow down the damage and fracture of the fibers when entering the die. Through the cooling section, rapid cooling and temperature reduction can slow down the crystallinity during the production of crystalline resin and improve toughness. By changing the support height of the support, multiple specifications of prepregs can be produced with the same set of dies. Brief Description of the Drawings

[0037] Figure 1 It is a schematic structural diagram of the production system for preparing thermoplastic prepreg by the slurry method of the present invention;

[0038] Figure 2 It is a schematic structural diagram of the pultrusion die for preparing thermoplastic prepreg by the slurry method;

[0039] Figure 3 It is a schematic structural diagram of the support part;

[0040] Figure 4 It is a top view of the die;

[0041] Figure 5 It is a schematic structural diagram of the lower die. Detailed Embodiments

[0042] The present invention will be further clarified below with reference to specific embodiments.

[0043] Such as Figure 1, the production system for preparing thermoplastic prepreg by the slurry method of the present invention includes: a yarn rack 1001 arranged along the fiber traveling direction, a sizing agent removing device 1002, an impregnation tank 1003, a drying device 1004, a pultrusion die 1005 and a winding device 1006. The impregnation tank is connected with a slurry concentration adjusting device, and the slurry concentration adjusting device includes a buffer tank 1007, a high-concentration slurry storage tank 1008, a slurry dispersion tank 1009, a raw material tank 1010, and a sample detection pool 1011. Among them, the fiber is wound on the yarn rack, and the sizing agent removing device is used to remove the sizing agent on the fiber. The sizing agent removing device is a heating device, such as an infrared heating device, which pyrolyzes the sizing agent on the fiber at high temperature, enabling the resin to better adhere to the fiber surface and improving its compatibility. The heating needs to reach 250 - 500 °C. The sizing agent removing device can specifically be composed of two upper and lower infrared heaters, and the two upper and lower heaters can adjust the height, and the maximum heater temperature reaches 500 °C. The fiber passes through the middle of the two upper and lower heaters, and the sizing agent is fully pyrolyzed by adjusting the heater height and temperature. The impregnation tank is used for the fiber to impregnate the slurry. The drying device 1004 is used to dry the solvent water of the adhered slurry. After the solvent (water) volatilizes, the adhered resin is melted by high-temperature heating and pultrusion through the pultrusion die, achieving the effect of the fiber with the molten viscosity of the resin, and making it into a certain specification. Specifically, the drying device can be an infrared oven. The infrared oven is divided into five sections in sequence along the length, and each section has two upper and lower infrared heaters. Each group of heaters can be independently set the temperature, and the temperature range is 0 - 750 °C. Starting from when the fiber comes out of the impregnation tank and enters the infrared oven, it evenly enters the 1st, 2nd, 3rd, 4th, and 5th sections; the drying process is divided into two stages: In the first stage, the infrared heating temperature is set at 110 - 200 °C, mainly in the 1st to 4th sections. The temperature setting in this stage is mainly to remove the moisture on the fiber, avoiding too high volatile content or large porosity in the prepreg. In the second stage, that is, the 5th section of the oven, the heating temperature is set according to the melting point of the material, generally 20 °C lower than the melting point of the material. This stage is to enable the resin to start melting and have a certain viscosity, and increasing the temperature helps the resin to quickly melt and impregnate the fiber in the pultrusion die. Finally, the pultruded material is wound. According to the differences in resin type, resin content, and resin mechanical properties, a suitable winding method for the sample needs to be selected. For example, if the sample is thick, it can be made into a plate, and if the sample is easy to bend, it can be wound by bending.

[0044] For the slurry concentration adjusting device, the raw material tank 1010 is used to store various raw materials. There are multiple raw material tanks 1010, which are connected to the slurry dispersion tank 1009 and used to inject the raw materials of each slurry into the slurry dispersion tank 1009.

[0045] A stirring device 1012 is provided in the slurry dispersion tank 1009 and is used to stir and disperse various raw materials to form a slurry.

[0046] The bottom outlet of the slurry dispersion tank 1009 is connected to the main slurry output pipe. The main slurry output pipe is connected to two output branch pipes through a three-way pipe joint 1013. One of the output branch pipes is connected to the high-concentration slurry storage tank 1008, which is used to transport high-concentration slurry into the high-concentration slurry storage tank 1008 when high-concentration slurry is prepared in the slurry dispersion tank. The other output branch pipe is connected to the buffer tank 1007, which is used to transport low-concentration slurry into the buffer tank 1007 when low-concentration slurry (i.e., the slurry concentration required normally) is prepared in the slurry dispersion tank.

[0047] The bottom outlet of the high-concentration slurry storage tank 1008 is connected to the buffer tank 1007 through an output pipe with a pump 28-e, which is used to inject high-concentration slurry into the buffer tank. A mechanical stirring device 1012 is provided in the high-concentration slurry storage tank 1008 to prevent the slurry from settling.

[0048] The slurry outlet at the bottom of the buffer tank 1007 is connected to the slurry inlet of the dipping tank 1003 through an output pipeline with a pump 28-b. A reflux pipe is provided between the buffer tank 1007 and the dipping tank 1003 to transport the slurry in the dipping tank back to the buffer tank, and the reflux pipe is equipped with a pump 28-c; the slurry circulates between the buffer tank and the dipping tank. A mechanical stirring device 1012 is also provided in the buffer tank 10017. The bottom of the buffer tank 1007 is connected to the sample detection pool 1011 through a slurry sample transport pipeline with a pump 28-d, and a viscometer 1014 is provided in the sample detection pool.

[0049] A heat preservation jacket is provided outside the dipping tank 1003 to avoid the influence of temperature change on viscosity measurement. It is also preferable to provide a heat preservation jacket on the outer wall of the buffer tank. The structure of the heat preservation jacket is not shown in detail in the figure, but those skilled in the art know how to set it and how to externally connect the above-mentioned heat preservation jackets to a constant temperature water bath to achieve the function of constant temperature, which is a conventional means. An ultrasonic vibrator is also provided in the dipping tank, which is not shown in the figure. Through ultrasonic vibration, the fibers are further spread out to facilitate the impregnation of the resin slurry into the fiber bundle.

[0050] During the production process of thermoplastic prepreg, the fibers are first passed through a sizing agent removing device to remove the sizing agent on the fibers during their movement, then enter the dipping tank to impregnate the slurry, then enter the drying device to evaporate the moisture, and then enter the pultrusion die for pultrusion and are wound by a winding device. To avoid the problem of the slurry concentration decreasing due to continuous impregnation of the fibers with the slurry, the present invention provides a slurry concentration adjusting device to adjust the slurry concentration. Two concentrations of slurry are prepared in the slurry dispersion tank: slurry a and slurry b, and the concentration of a > the concentration of b. Concentration of a: 30 - 60%, concentration of b: 5 - 40%, and both concentrations are mass percentages. First, the high-concentration slurry a is prepared and transported to the high-concentration slurry storage tank through pump 28-a. Then, slurry b is prepared. Slurry b is the actual slurry concentration required during the production process, and the viscosity of the slurry at this concentration is measured and transported to the buffer tank through pump 28-a. Slurry b circulates in the dipping tank and the buffer tank. The slurry in the buffer tank is transported to the sample detection pool for viscosity detection. Once it drops to a certain extent, the high-concentration slurry storage tank injects high-concentration slurry into the buffer tank through pump 28-e, and the injection stops when the slurry reaches the appropriate concentration. The sample detection pool 1011 is also connected to an overflow pipe to send the excess slurry back to the buffer tank.

[0051] Furthermore, a liquid level gauge can also be provided in the buffer tank, which is not specified in detail in this figure; when the slurry liquid level in the buffer tank is insufficient, the slurry in the slurry dispersion tank is replenished to the buffer tank, and when the slurry liquid level in the slurry dispersion tank is sufficient, the pipeline transportation between the slurry dispersion tank and the buffer tank is closed. The driving of various pumps and agitators in this system can be driven by electricity or air source, but in order to avoid the signal interference caused by the current signal to the viscometer, it is preferably powered by an air source.

[0052] This embodiment also provides the structure of the pultrusion die, such as Figures 2 - 5 , including an upper die 1 and a lower die 2.

[0053] The upper die 1 includes a first heating section 3 and a first cooling section 4 connected to the first heating section 3, and the lower die 2 includes a second heating section 5 and a second cooling section 6 connected to the second heating section 5.

[0054] The bottom surface of the first heating section 3 includes a connected first inclined surface 301 and a first flat surface 302, and the top surface of the second heating section 5 includes a connected second inclined surface 501 and a second flat surface 502. The first inclined surface 301 and the second inclined surface 501 are arranged oppositely, and a V-shaped die cavity 7 with a V-shaped longitudinal section is formed between the first inclined surface 301 and the second inclined surface 501 or between the planes where they are located. The first flat surface 302 and the second flat surface 502 are substantially parallel to form a first equal-section die cavity 8, and the narrow opening of the V-shaped die cavity 7 communicates with the first equal-section die cavity 8. The taper d of the V-shaped die cavity is 0.01 - 20 degrees, preferably 0.01 - 10 degrees, and specifically can be 1.3° in this embodiment.

[0055] A support member 9 is provided between the first plane 302 and the second plane 502. The support member can be a gasket, and the gasket is fixed by an internal hexagonal screw. The gasket is fixed to the lower mold and supported by the support member. The first plane 302 and the second plane 502 are substantially parallel to form a first constant cross-section die cavity. By adjusting the support height of the support member, the gap between the upper and lower molds can be adjusted, that is, the thickness of the prepreg product can be controlled. The support member can also limit the width of the prepreg product. There are two support members, which are located on both sides of the upper and lower molds.

[0056] Uniformly distributed heating tubes 14 are provided in both the first heating section 3 and the second heating section 5. The heating sections are heated by an electric heating method, and the heating temperature is 200 - 500 °C. The number of heating tubes in each heating section is not particularly limited and is set according to the heating size and temperature of the mold, generally at least 5.

[0057] The bottom surface of the first cooling section 4 has a third plane 401, and the third plane 401 is connected to the first plane 302 and is on the same horizontal plane. The top surface of the second cooling section 6 has a fourth plane 601, and the fourth plane 601 is connected to the second plane 502 and is on the same horizontal plane. The third plane 401 and the fourth plane 601 are substantially parallel to form a second constant cross-section die cavity 10. For temperature-sensitive crystalline polymers, slow cooling makes the resin close to a static isothermal process, which is easy to generate large spherulites, making the product brittle and reducing the mechanical properties. By rapidly cooling and lowering the temperature in the second constant cross-section die cavity 10, the crystallization time of the polymer is reduced, the crystallinity can be reduced, and the impact toughness can be improved. Cooling medium flow channels 11 are provided inside both the first cooling section 4 and the second cooling section 6. The cooling medium can be cooling water, and the temperature of the cooling water is controlled at -20 - 0 °C.

[0058] A first heat insulation plate 12 is provided between the first heating section 3 and the first cooling section 4, and a second heat insulation plate 13 is provided between the second heating section 5 and the second cooling section 6. The adjacent heating sections, heat insulation plates, and cooling sections can be fixed by welding or screw fixing. The bottom surface of the first heat insulation plate 12 is respectively connected to the first plane 302 and the third plane 401, and the three are on the same horizontal plane. The top surface of the second heat insulation plate 13 is respectively connected to the second plane 502 and the fourth plane 601, and the three are on the same horizontal plane. The heat insulation plate can prevent the mold from being thermally deformed due to excessive temperature difference, which affects the accuracy.

[0059] Tool steel is selected as the mold material for the upper mold and the lower mold. The tool steel needs to withstand 500 °C, and the thermal deformation coefficient should be small, and the hardness should reach HRC 70.

[0060] The overall length of the mold is 250 - 700 mm to ensure that the resin can be completely melted. The horizontal projection lengths of the first inclined surface 301 and the second inclined surface 501 are the same, both being 160 - 460 mm (i.e., the length of the V-shaped cavity 7); the lengths of the first flat surface 302 and the second flat surface 205 are the same, both being 90 - 240 mm (i.e., the length of the first constant cross-section cavity 8); the lengths of the third flat surface 401 and the fourth flat surface 601 are the same, both being 50 - 150 mm (i.e., the length of the second constant cross-section cavity). The inner part of the mold cavity needs to be mirror-polished and chrome-plated, and the surface precision of the cavity needs to reach 0.001 - 0.05 mm, specifically 0.02 mm.

[0061] The upper mold and the lower mold are detachably connected. During use, the lower mold is fixed on the support table, the support member is placed between the upper and lower molds (such as between the first flat surface and the second flat surface) and fixed to the lower mold, and the gap between the two molds is controlled by adjusting the thickness of the support member. After the upper mold and the lower mold are closed, screws are needed for fixation to prevent the upper and lower misalignment of the mold. The heating tube is externally connected to the circuit to achieve the heating of the heating section, and the cooling medium flow channel is connected to the ice water machine through the pipeline to achieve the circulating flow of the cooling medium. The fiber impregnated with resin enters the cavity from the mold inlet II (the wide opening of the V-shaped cavity), the resin passes through the V-shaped cavity, the resin is melted by the heating of the heating section, the mold gap gradually decreases, the pressure transmission gradually compacts, the resin is gradually squeezed into the fiber bundle, then it passes through the second constant cross-section cavity for rapid cooling and temperature reduction, and the fiber comes out from the mold outlet I and is cooled and wound up.

[0062] In the prior art, for the mold with a constant cross-section cavity, the upper and lower surfaces of the inner wall of the cavity are parallel structures, and the extrusion and impregnation effect of the mold on the resin is not significant, resulting in uneven impregnation of the prepreg resin. However, in the present invention, by designing a new mold, a V-shaped structure is presented inside the mold, which can gradually provide an extrusion force to fully impregnate the resin into the fiber. During production, no problem of uneven impregnation in the mold with a constant cross-section cavity is found, the bubble porosity is greatly reduced, the damage to the fiber is small, and the breakage of the fiber is avoided.

[0063] Generally speaking, it is possible to manually operate this production system without an additional automatic control module to realize the operation of this production system. However, for the consideration of production automation, it is better to set up a PLC control module. The PLC control module adopts an existing conventional structure, generally including a CPU, an input unit and an output unit electrically connected to the CPU. In the present invention, the input unit can be electrically connected to a liquid level gauge and a viscometer, receive the liquid level signal and the viscosity signal, and then feedback them to the CPU. The CPU issues instructions to the output unit, and the output unit is electrically connected to each pump, valve, etc., and controls the start and stop of the corresponding pump, valve, etc. according to the instructions. The control module is not an improvement point of the present invention and can be set up conventionally by those skilled in the art, so it will not be elaborated in detail. In addition, in this production system, the transmission of fibers is carried out through each conveyor roller, which is a conventional operation in this field and is not an improvement point, so it will not be elaborated in detail.

Claims

1. A production system for preparing thermoplastic prepreg by slurry method, characterized in that, Comprising: A sizing agent removing device (1002), an impregnating tank (1003), a drying device (1004), a pultrusion die (1005) and a winding device (1006) arranged along the fiber traveling direction. The impregnating tank is connected with a slurry concentration adjusting device, and the slurry concentration adjusting device includes: A buffer tank (1007), the slurry outlet of the buffer tank is connected with the slurry inlet of the impregnating tank, and a return pipe for refluxing and transporting the slurry in the impregnating tank to the buffer tank is provided between the buffer tank and the impregnating tank; the buffer tank is connected with a sample detection pool through a slurry sample conveying pipeline, and a viscometer is arranged in the sample detection pool; A high-concentration slurry storage tank (1008), connected with the buffer tank, for injecting high-concentration slurry into the buffer tank; A slurry dispersion tank (1009), respectively connected with the buffer tank and the high-concentration slurry storage tank, for injecting slurries with corresponding concentrations into the buffer tank and the high-concentration slurry storage tank; A raw material tank (1010), connected with the slurry dispersion tank, for injecting raw materials into the slurry dispersion tank; The pultrusion die includes: An upper die, having a first heating section (3), the bottom surface of the first heating section includes a connected first inclined surface (301) and a first flat surface (302); A lower die, having a second heating section (5), the top surface of the second heating section includes a connected second inclined surface (501) and a second flat surface (502); The first inclined surface and the second inclined surface are arranged oppositely, and a V-shaped die cavity (7) with a V-shaped longitudinal section is formed between the first inclined surface and the second inclined surface or between the planes where they are located. The first flat surface and the second flat surface are substantially parallel to form a first equal-section die cavity (8), and the narrow opening of the V-shaped die cavity is communicated with the first equal-section die cavity; The taper of the V-shaped die cavity is 0.01 - 20 degrees; The horizontal projection lengths of the first inclined surface and the second inclined surface are the same, both being 160 - 460 mm; the lengths of the first flat surface and the second flat surface are the same, both being 90 - 240 mm; The upper die includes a first cooling section (4) connected with the first heating section, and the lower die includes a second cooling section (6) connected with the second heating section; the bottom surface of the first cooling section has a third flat surface (401), the third flat surface is connected with the first flat surface and is in the same horizontal plane, the top surface of the second cooling section has a fourth flat surface (601), the fourth flat surface is connected with the second flat surface and is in the same horizontal plane; a first heat insulation board is provided between the first heating section and the first cooling section, and a second heat insulation board is provided between the second heating section and the second cooling section; the thickness of the heat insulation board is ≥10 mm and ≤30 mm.

2. The production system for preparing thermoplastic prepreg by the slurry method according to claim 1, characterized in that, A liquid level gauge is arranged in the buffer tank; a mechanical stirrer is arranged in the buffer tank, the slurry dispersion tank and the high-concentration slurry storage tank.

3. The production system for preparing thermoplastic prepreg by the slurry method according to claim 1, characterized in that, A heat preservation jacket is arranged on the outer wall of the buffer tank; a heat preservation jacket is arranged on the outer wall of the impregnating tank.

4. The production system for preparing thermoplastic prepreg by the slurry method according to claim 1, characterized in that, It further includes a yarn rack arranged upstream of the sizing agent removing device.

5. The production system for preparing thermoplastic prepreg by the slurry method according to claim 1, characterized in that, A support member (9) is arranged between the first flat surface and the second flat surface.

6. The production system for preparing thermoplastic prepreg by the slurry method according to claim 1, characterized in that, The upper die and the lower die are detachably connected.

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