Thermoplastic polyimide fabric prepreg preparation method and special device thereof

Abstract

The invention provides a thermoplastic polyimide prepreg preparation method and a special device thereof, and the preparation method comprises the steps of unwinding, cloth storage and desizing, primary impregnation, secondary impregnation, pre-drying, tertiary impregnation, drying and the like. The solvent method for preparing the high-performance thermoplastic prepreg is realized, and the problems that the prepreg is low in resin content, insufficient in impregnation, insufficient in flatness, easy to have air holes, hard spots and the like are solved; the method is high in preparation efficiency and low in abrasion, and the prepared prepreg fiber is uniform in impregnation, flat and smooth in surface and uniform in thickness, has high strength and impact resistance, can be stored for a long time and can be recycled; the method is suitable for manufacturing the resin prepreg which is high in melt viscosity and can be dissolved in a proper single or mixed solvent, and the prepared prepreg can be applied to manufacturing of light-weight high-performance parts in the fields of rail transit, aerospace, weapons and the like.

Description

Technical Field

[0001] The invention relates to the technical field of composite material molding, and in particular to a method for preparing a thermoplastic polyimide fabric prepreg. Background Art

[0002] The solvent method is a commonly used preparation method for thermosetting fabric prepregs, which usually involves impregnating the fiber fabric with a resin glue solution of a certain concentration, and then heating and drying out most of the solvent in the glue solution to obtain a uniformly impregnated fabric prepreg.

[0003] Most of the domestic preparation processes for high-performance thermoplastic composite materials have evolved from the preparation processes for thermosetting composite materials, or directly use the equipment for thermosetting fabric prepregs to prepare thermoplastic prepregs, without making targeted adjustments for certain specific resin properties. As a result, when high-performance thermoplastic prepregs are prepared by the solvent method, the resin content is low, the impregnation is insufficient, the prepreg flatness is insufficient, and defects such as pores and pitting are prone to exist.

[0004] For example, for the solvent method to prepare high-performance thermoplastic prepregs, for thermoplastic resins such as TPI, PEI, etc., compared with most thermosetting resin solutions, the viscosity is larger and it is more difficult to fully impregnate the reinforcing fibers. A low-solid content glue solution is required to impregnate the fibers. However, when the solid content of the glue solution is low, the resin content of the prepreg is also correspondingly low. Obviously, increasing the solid content of the glue solution can increase the resin content of the prepreg, but the difficulty of impregnation will increase accordingly; continuous secondary impregnation will increase the resin content of the prepreg, but the degree of increase is limited; after the prepreg is prepared, using the prepreg to repeat the process of preparing the prepreg will increase the resin content of the prepreg, but the preparation efficiency will be significantly reduced, and the friction with the equipment will also increase the probability of prepreg damage. Summary of the invention

[0005] Aiming at the problems of low resin content, insufficient impregnation, insufficient flatness of the prepreg, and easy existence of defects such as pores and pitting in the existing solvent method for preparing thermoplastic prepreg, the present invention provides a method for preparing a high-performance thermoplastic prepreg, and also provides a special device, which can improve the resin content of the prepreg while fully impregnating the fiber with resin, so as to prepare a high-performance thermoplastic composite material.

[0006] The present invention mainly realizes the solvent method preparation of high-performance thermoplastic prepreg through a primary dipping device and a drying device with special structural designs, and a design of fully impregnating the fabric with low-concentration glue and exhausting, pre-drying and shaping for a primary dipping, and increasing the amount of glue by secondary dipping and drying, thereby obtaining a high-performance thermoplastic prepreg with uniform impregnation, high resin content and smooth surface.

[0007] The preparation method of the present invention is different from the prior art in that: a three-dipping process is adopted, wherein a polyimide glue solution with a relatively low concentration (solid content of 1% to 10%) is used for the first dipping, and the fiber fabric is pre-impregnated by the strong penetration of the dilute solution, and a single-side gluing method is adopted, so that the solution with a relatively low concentration has sufficient time to fully impregnate the fiber fabric and exhaust the air in the fabric, so as to solve the problem that the polyimide is difficult to completely impregnate the fabric; a polyimide glue solution with a relatively high concentration (solid content of 10% to 30%) is used for the second and third dippings, and since the solubility of the polyimide polymer in the solvent is limited, the polyimide polymer in the solid state is preferably not impregnated with the fiber fabric. When the content reaches more than 30%, the polyimide cannot be completely dissolved, but swells to a paste and cannot be used. As the solid content increases, the difficulty of impregnating the fiber with the polyimide glue solution gradually increases. When a solution with a smaller solid content is used, it is difficult to increase the glue content of the prepreg. Therefore, the secondary and tertiary dipping methods are used to increase the glue amount or the glue content of the prepreg; two drying processes are adopted, in which the pre-drying section is used to dry out most of the solvents of the primary and secondary dipping, and to allow the polyimide to initially impregnate the fiber fabric and shape it; the drying section is used to thoroughly dry the residual solvent in the pre-drying section and the new solvent brought in by the tertiary dipping.

[0008] The specific technical solution adopted by the present invention is as follows:

[0009] A method for preparing thermoplastic polyimide fabric prepreg includes unwinding, cloth storage and desizing, primary dipping, secondary dipping, pre-baking, tertiary dipping and drying. The specific steps are as follows:

[0010] 1) Unwinding, cloth storage and desizing

[0011] The fiber fabric is unrolled, stored and then desized according to conventional processes;

[0012] 2) One-time dipping

[0013] The fiber fabric treated in step 1) is introduced into a primary dipping device, which consists of a dipping tank 3, a glue coating roller 2, a breathing roller 4 and a dipping roller 5; a polyimide glue solution with a solid content of 1% to 10% is weighed and poured into the dipping tank 3, the fiber fabric treated in step 1) is introduced to the glue coating roller 2 through a cloth guide roller 1, the fiber fabric is coated with glue, and then the coated fiber fabric is introduced into the dipping tank 3 through a breathing roller 4 and a dipping roller 5 to complete the primary dipping; the fiber fabric runs in the dipping tank 3 at a speed of 1 to 4 m / min, and the polyimide glue solution is a mixture of a thermoplastic polyimide resin and a solvent;

[0014] 3) Secondary dipping

[0015] The fiber fabric obtained in step 2) is subjected to secondary dipping using a conventional dipping device, wherein the solid content of the polyimide adhesive is 10% to 30%; the running speed of the secondary dipping fiber fabric is consistent with that of step 1);

[0016] 4) Pre-baking

[0017] The fiber fabric obtained in step 3) is placed in a drying device for pre-drying, and the pre-drying temperature is 30°C to 50°C lower than the boiling point of the solvent;

[0018] 5) Three times dipping

[0019] The fiber fabric obtained in step 4) is subjected to a third dipping process using a conventional dipping device. The dipping process is the same as the second dipping process. The solid content of the polyimide glue solution is 10% to 30%, which is adjusted according to the resin content of the prepared prepreg.

[0020] 6) Drying

[0021] The prepreg fabric 15 obtained in step 5) is placed in a drying device for drying to obtain a thermoplastic polyimide fabric prepreg, the drying temperature is (solvent boiling point -10 to +35)°C, and the drying time is not less than 5 minutes.

[0022] Furthermore, the dipping in step 2) is carried out at room temperature for 0.25 to 1 minute, and the fabric tension is constant to ensure that the fabric can be evenly and smoothly unfolded. The solvent is one or both of N,N-dimethylacetamide and N,N-dimethylformamide.

[0023] Preferably, the solid content of the polyimide glue in the first dipping step 2) is 5% to 8%.

[0024] Furthermore, in the step 4), for the mixed solvent, the boiling point of the solvent is a weighted average of the boiling points of the mixed solvent.

[0025] Furthermore, in step 6), for the mixed solvent, the boiling point of the solvent is a weighted average value of the boiling points of the mixed solvent, and the weighted average value of the boiling point of the mixed solvent is the sum of the products of the boiling points of each solvent and its mass percentage in the mixed solvent.

[0026] Preferably, the drying tunnel length of the drying device in step 4) is shorter than that in step 6), in order to allow some solvent to remain in the prepreg after prebaking (generally, the solvent residue is 5% to 15%), so as to maintain a certain degree of adhesion and prevent the prepreg from being too rigid and curling.

[0027] Preferably, the drying tunnel length of the drying device in step 4) is 4 to 6 m;

[0028] Preferably, the drying tunnel length of the drying device in step 6) is 5m to 20m, and the production speed is 1m / min to 4m / min.

[0029] The present invention also provides a one-time dipping device and a drying device for preparing thermoplastic polyimide fabric prepreg, wherein the one-time dipping device is composed of a dipping tank 3, a coating roller 2, a breathing roller 4 and a dipping roller 5, wherein the coating roller is composed of a thick stick and two thin rollers, wherein the two thin rollers are symmetrically distributed on both sides of the thick roller, and the center line of the three rollers is in a "V" shape; the breathing roller 4 is a roller that can be raised and lowered and adjusted, and is installed above the dipping tank 3 and can move up and down, and the relative position of the axis of the breathing roller 4 is located between the coating roller 2 and the dipping roller 5;

[0030] The "V" angle of the glue coating roller 2 is 90°~145° and is adjustable. The thicker roller is installed on the glue dipping tank 3, and its diameter is slightly less than 2 times the maximum glue height in the glue dipping tank. The lower 1 / 2 is located inside the glue tank, and the upper 1 / 2 is higher than the glue tank plane. The gap between the two fine rollers and the coarse roller should not be too large. It should be ensured that the fabric can form a certain coating on the upper surface of the coarse roller, and the wrap angle should be ≥10°. The lower surfaces of the two fine rollers are both higher than the glue liquid level. In this way, it is ensured that the fabric will not be directly immersed in the glue liquid when passing through the glue coating roller, and the exhaust will fail.

[0031] The breathing roller 4 can be installed on a movable support frame above the dipping tank 3 and driven by a motor to move freely up and down.

[0032] The devices used for the secondary and tertiary dipping of the present invention are conventional devices, which have the functions of conveying, dipping, squeezing glue liquid fabric and smoothing glue liquid.

[0033] The drying device is composed of a drying box body 13, an explosion-proof fan 8, a heating unit 9 and an exhaust gas treatment device 10, and the drying box, the explosion-proof fan 8, the heating unit 9 and the exhaust gas treatment device 10 are connected by pipelines; the heating unit 9 is fixedly installed on the top of the drying box body; the drying box body 13 is composed of a three-layer structure, the inner cavity of the box body is a cavity channel a, a cavity channel b is provided between the inner layer and the middle layer, and a cavity channel c is provided between the middle layer and the outer layer. A detachable hot air outlet device 12 is installed in the inner layer of the box body, and the cavity channel a is connected with the cavity channel b through the detachable hot air outlet device 12; the detachable hot air outlet device 12 is provided with a plurality of evenly distributed holes at one end away from the inner wall of the box; a plurality of one-way valves 16 are provided between the cavity channel a and the cavity channel c, and the number and position of the one-way valves are not limited. The cavity channel b is closed at the one-way valve installation position, the purpose of which is to allow the gas in the cavity channel a to flow to the cavity channel c under a certain pressure and prevent backflow.

[0034] Furthermore, the detachable hot air outlet device 12 is a trapezoidal structure with a hollow interior, which is staggered up and down, and the devices on the same side are evenly arranged, so that the fiber fabrics in the drying box can be blown by the hot air flow as evenly as possible; so that the fiber fabrics are suspended in the inner cavity of the drying box without touching the body of the drying box.

[0035] The length of the larger rectangular surface (i.e., the air outlet surface) of the trapezoidal body of the detachable hot air outlet device should be at least greater than the width of the fiber fabric, and the preferred length-to-width ratio is (3-6):1.

[0036] Preferably, the diameter of the holes arranged on the detachable hot air outlet device is 0.5 cm to 1 cm, and the hole density is 2500 holes / m 2 ~10000pcs / m 2 .

[0037] Furthermore, the lowest temperature of the drying box is controlled not higher than 40°C.

[0038] The drying tunnel length of the drying device can be flexibly selected according to the production speed and drying temperature. Under the same conditions, the higher the drying temperature, the shorter the required drying time (that is, the shorter the required drying tunnel length, or the faster the production speed). However, due to the limitation of the operating site, the drying tunnel length cannot be increased indefinitely. The drying of prepreg can be achieved by increasing the drying temperature or reducing the production speed. In the pre-baking stage, the drying time is shortened by 30s to 90s for every 10°C increase in the drying temperature. Under the same production speed, the drying tunnel length is shortened by 0.5 to 1.5m.

[0039] The drying temperature in step 6) of the present invention is higher than the pre-drying temperature in step 4) and the drying tunnel length is longer, the purpose of which is to completely dry out the solvent of the three dippings. Generally, the longer the drying section length is, the more conducive it is to drying the solvent, but the limitations of the site and the length of a single roll of fabric must also be comprehensively considered.

[0040] Since most solvents are volatile and flammable chemicals, the drying box adopts an explosion-proof design. The air is heated and pumped in through an explosion-proof motor, and the air inlet channel is separated from the exhaust gas outlet channel to avoid contamination of the pumped air. At the same time, it can more effectively take away the solvent in the pre-impregnated fabric. The exhaust gas containing the solvent is discharged in time under the action of the explosion-proof fan to avoid danger caused by excessive concentration; the solvent in the exhaust gas drops in temperature and condenses, and can be recycled.

[0041] Unwinding provides constant tension for the entire fabric to ensure stable and smooth unwinding of the fabric. The unwinding tension is set according to needs, generally set to 5N~50N; the cloth storage system is a mechanism that can adjust the total length of the fabric passing through it. When a roll of fabric in the unwinding mechanism is used up, by adjusting the storage length, time can be provided for connecting two rolls of fabric to ensure that the prepreg preparation is stable and continuous without stopping the machine; desizing is to decompose the sizing agent on the surface of the fabric by high-temperature heating and remove it under negative pressure; desizing is to remove the epoxy sizing agent with low temperature resistance on the surface of the fiber fabric to prevent the epoxy sizing agent from decomposing and producing impurities at higher processing temperatures, which will affect the performance of the polyimide prepreg molded products; the desizing temperature should be above the decomposition temperature of the sizing agent, and samples should be taken for scanning electron microscopy analysis. If there are clear grooves on the surface of the fiber and no other irregular impurities, it proves that the desizing treatment is completed, and the desizing time should be no less than 5 minutes.

[0042] In order to facilitate regular winding, a deviation correction device and a winding device can be used to regularly wind the prepreg. The deviation correction device is located on the front side of the winding device to timely correct the movement trajectory of the prepreg and make the prepreg roll neatly; the winding device is a winding device with a motor, which drives the roller to rotate through the motor to roll the prepreg. The deviation correction can adopt any form of photoelectric or mechanical deviation correction system, the purpose is to adjust the continuously prepared fabric prepreg in time, prevent the prepreg from deviating and twisting, keep the surface flat, and ensure neat winding. The winding can adopt one of several forms such as servo winding, magnetic powder controlled motor winding, and mechanical winding. The servo winding form is preferred. The winding speed should match the unwinding and glue impregnation speeds. At the same time, the winding should have a certain tension, generally set to 5N~50N, so that the prepreg is tightly wound on the paper tube.

[0043] According to production needs, multiple drying boxes can be connected in series to form a drying tunnel that meets the required length. The drying boxes can be temperature-controlled independently, and the number of series connections can be selected according to needs.

[0044] The prepreg prepared by the method of the invention can be used to prepare high-performance polyimide composite materials.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) The present invention adopts a three-time dipping process, wherein the first dipping adopts a polyimide glue solution with a relatively low concentration (solid content of 1% to 10%), and uses a single-time dipping device designed by the present invention to achieve single-side gluing to discharge air in the fabric, thereby solving the problem in the prior art that polyimide is difficult to fully impregnate the fabric; the second and third gluing adopt a polyimide glue solution with a relatively high concentration (solid content of 10% to 30%), thereby increasing the gluing amount and the glue content of the prepreg, and the three-time dipping solves the problem that thermoplastic polyimide is difficult to fully impregnate fabric fibers;

[0047] (2) The present invention adopts a two-stage drying process. The pre-drying stage mainly removes most of the solvents of the first and second dipping, and makes the polyimide initially impregnate the fiber fabric and shape it; the drying stage mainly thoroughly dries the residual solvent in the pre-drying stage and the newly introduced solvent in the third dipping.

[0048] (3) The present invention adopts a specially designed one-time dipping device. The one-time dipping device adopts a one-side dipping exhaust-breathing roller design. Compared with directly immersing the glue in the glue, it is more conducive to the discharge of air in the glue and fiber fabric, so as to achieve full impregnation of the fiber fabric with the glue. At the same time, the breathing roller increases the time and distance interval between the first dipping and the second dipping, which is conducive to increasing the dipping time, so that the glue can impregnate the fabric under the action of gravity, making the impregnation more complete. At the same time, the existence of the dipping roller makes the solvent of the first dipping evaporate more, and the glue adheres to the gap between the fabric, which is also beneficial to increasing the amount of glue.

[0049] The primary dipping device is equipped with a glue coating roller, which consists of three rollers, one thick and two thin rollers. The two thin rollers are distributed on both sides of the thick roller, and the center line of the three rollers is in a "V" shape. The dipping of the fabric is adjusted by adjusting the angle of the "V" shape. The larger the angle of the "V" shape, that is, the lower the two thin rollers are, the greater the contact area and pressure between the fabric and the thick roller, and the more complete the dipping and exhaust. The glue coating roller rotates to adhere to the glue liquid, and the glue liquid penetrates from one side of the fabric to the other side under the pressure of the roller, and the air between the fabrics is discharged at the same time.

[0050] The breathing roller 4 used is a roller that can be raised and lowered and adjusted. By adjusting the height of the breathing roller, the distance between the breathing roller and the dipping tank can be adjusted. When the breathing roller is in a higher position, the glue liquid can penetrate into the gaps between the fabric fibers again under the action of gravity to fully exhaust the gas. Secondly, the solvent in the glue liquid in the fabric has sufficient volatilization time. After the solvent evaporates, it is also beneficial to increase the amount of glue for dipping again.

[0051] The dipping roller 5 is a stainless steel roller with a smooth surface, which can rotate synchronously with the fabric to reduce the friction between the fabric and the roller and reduce fiber damage. During production, the fiber fabric runs under the dipping roller, which mainly plays a guiding and yarn spreading role to promote the impregnation of the glue liquid into the fabric fibers.

[0052] (4) The drying device provided by the present invention adopts a horizontal design and can independently control the temperature within a range of 40°C to 200°C. When in use, the air is heated by the heating unit 9 and then sent into the cavity channel b of the box by the explosion-proof fan 8, and blown out through the detachable hot air outlet device 12. The detachable hot air outlet device 12 is arranged in an up-and-down staggered manner. Under the action of the upper and lower hot air, the pre-impregnated fabric 15 is suspended in the drying box in a wave shape. The solvent in the pre-impregnated fabric 15 is heated and volatilized quickly and is carried away by the hot air flow. The hot air with the solvent flows through the cavity channel c of the box and is discharged to the exhaust gas treatment device 10 by the explosion-proof fan. In this way, the pre-impregnated fabric 15 The hot air flow and the solvent-free hot air flow are separated by the middle layer of the box, which prevents the solvent-free hot air flow from being contaminated by the hot air flow with solvent, further improving the solvent removal capacity; at the same time, the hot air flow with solvent is entirely coated on the outer layer of the solvent-free hot air flow to form an insulation layer, thereby realizing heat recovery, saving energy, and improving the utilization rate of thermal energy; when the hot air flow with solvent passes through the pipeline connected to the exhaust gas treatment device 10, due to heat exchange with the outside air, the solvent temperature drops below its boiling point and condenses into liquid, which is recycled by the solvent recovery device 11, and the uncondensed solvent enters the exhaust gas treatment device 10 for treatment and then discharged.

[0053] In addition, the drying device designed in the present invention can be used in series with multiple drying devices according to production needs, and the temperature can be controlled independently.

[0054] (5) The method for preparing thermoplastic polyimide fabric prepregs of the present invention can achieve three impregnations of the fiber fabric, with good fabric impregnation effect, uniform and sufficient fiber impregnation, and can still achieve good impregnation for thermoplastic resins with high melt viscosity such as TPI and PEI. At the same time, compared with the method of increasing the resin content by repeating the prepreg preparation process once with a prepreg product with a low resin content, the preparation method can achieve the preparation of a prepreg with a high resin content in one time, with high preparation efficiency, less wear, and higher corresponding prepreg strength; the prepreg prepared by the method of the present invention has uniform fiber impregnation, a smooth surface, and uniform thickness. Even with a high resin content, there will be no powdering or peeling. The prepreg has high strength and impact resistance, can be stored for a long time, and can be recycled.

[0055] The preparation method is suitable for the manufacture of resin prepregs with high melt viscosity and soluble in a single or mixed solvent. The prepared prepregs can be used in the manufacture of lightweight and high-performance parts in various fields such as automobiles, rail transportation, aerospace, and weapons after cutting and laying. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 Preparation flow chart of thermoplastic polyimide prepreg according to the present invention

[0057] Figure 2 Structural schematic diagram of a one-time dipping device according to the present invention

[0058] Figure 3 Structural schematic diagram of the drying device involved in the present invention

[0059] Among them: 1- cloth guide roller, 2- glue coating roller, 3- glue dipping tank, 4- breathing roller, 5- glue dipping roller, 6- metering roller, 7- smoothing roller, 8- explosion-proof fan, 9- heating unit, 10- exhaust gas treatment device, 11- recovery device, 12- removable hot air outlet device, 13- drying box body, 14- gas flow direction, 15- pre-impregnated fabric, 16- one-way valve, 17- cavity channel a, 18- cavity channel b, 19- cavity channel c. DETAILED DESCRIPTION

[0060] The specific implementation of the present invention is further described in detail below in conjunction with the examples and drawings. The following examples are only used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0061] The tensile properties of prepreg are tested in accordance with GB / T 1040.4-2006, the flexural properties are tested in accordance with GB / T1449-2005, the impact properties are tested in accordance with GB / T 1843-2008, the resin content is tested in accordance with GB / T 2577-2005, and the volatile content is tested in accordance with GB / T32788.3-2016.

[0062] Device Example 1

[0063] The one-time glue dipping device of the present invention is composed of a glue dipping tank 3, a glue coating roller 2, a breathing roller 4 and a glue dipping roller 5, a metering roller 6, and a smoothing roller 7. Figure 2 As shown, compared with the conventional dipping device, the one-time dipping device of the present invention adopts a glue coating roller 2 and a breathing roller 4 of a specific structure, wherein the glue coating roller 2 is composed of a thick stick and two thin rollers, wherein the thick roller is fixed in position and installed on the dipping tank 3, and its diameter is slightly less than 2 times the maximum height of the glue liquid in the dipping tank, and the lower 1 / 2 is located inside the glue tank, and the upper 1 / 2 is higher than the glue tank plane. The two thin rollers are symmetrically distributed on both sides of the thick roller, and the center line of the three rollers is in a "V" shape. The adjustment of the "V" angle can be achieved by symmetrically adjusting the positions of the thin rollers on both sides. The "V" angle can be adjusted in the range of 90° to 145°. The gap between the two thin rollers and the thick roller should not be too large, and it should be ensured that the fabric can form a certain coating on the upper surface of the thick roller, and the wrap angle should be ≥10°. The lower surfaces of the two thin rollers are both higher than the glue liquid level, so that it is ensured that the fabric will not be directly immersed in the glue liquid and the exhaust will fail when passing through the glue coating roller.

[0064] When preparing prepreg, the fiber fabric is wavy in shape of "Ω" and passes through the lower side of one fine roller, the upper side of the coarse roller, and the lower side of the other fine roller in turn, so that the fabric wraps the coarse roller and the fine roller on the upper side of the coarse roller, and the wrapping area and pressure of the fabric on the coarse roller are adjusted by adjusting the "V" angle, thereby adjusting the glue amount and the glue penetration pressure here.

[0065] The breathing roller 4 is an adjustable roller that can be raised and lowered. It is installed on a movable support frame above the dipping tank 3. It is driven by a motor to move freely up and down, thereby adjusting the vertical distance between the lifting roller and the glue, so that after dipping, there is sufficient time for the glue to fully penetrate the fabric. The relative position of the axis of the breathing roller 4 is between the glue coating roller 2 and the dipping roller 5. The metering roller 6 is located above the rear of the dipping tank and has a smooth surface. The width of the gap between the two metering rollers is adjustable. When the fabric with glue passes through the gap between the two rollers, the excess glue is squeezed out under the squeezing action of the two rollers. Behind the metering roller is the smoothing roller 7, which consists of an upper and lower roller. Its surface is smooth. When prepreg passes through the upper and lower rollers of the smoothing roller, the glue is evenly flattened and coated on the surface of the fiber fabric under the pressure of the rollers.

[0066] The drying device of the present invention is composed of a drying box body 13, an explosion-proof fan 8, a heating unit 9 and an exhaust gas treatment device 10. Figure 3 As shown, the lowest temperature of the drying box is not higher than 40°C, and the drying box body 13 is composed of a three-layer structure. The inner cavity of the box is a cavity channel a, a cavity channel b is provided between the inner layer and the middle layer, and a cavity channel c is provided between the middle layer and the outer layer. Removable hot air outlet devices 12 are installed on the box body on both sides of the cavity channel a. The drying box body 13 is open at both ends, and the box body is closed at the opening section. The opening should be as small as possible to avoid excessive heat loss, but it should ensure that the fiber fabric passes smoothly through the openings on both sides without friction with the box body.

[0067] A plurality of one-way valves 16 are provided between cavity channel a and cavity channel c. Cavity channel b is closed at the one-way valve installation position and is not connected with cavity channel a and cavity channel c. The number and position of the one-way valves are not limited. The purpose is to allow the gas in cavity channel a to flow to cavity channel c under a certain pressure and prevent backflow.

[0068] The detachable hot air outlet device 12 is a trapezoidal structure with a hollow interior. The smaller rectangular surface of the trapezoidal body is connected to the drying box body and communicates with the cavity channel b. The larger rectangular surface is approximately parallel to the fabric and has a large number of evenly distributed through holes. The hole diameter is 0.5 to 1 cm and the hole density is 2500 / m 2 ~10000pcs / m 2The length direction of the detachable hot air outlet device is perpendicular to the running direction of the fabric, and its width direction is parallel to the running direction of the fabric. It is installed on the box body on the upper and lower sides of the cavity channel a. The length of the larger rectangular surface of the trapezoidal body (i.e., the air outlet surface) should be at least greater than the width of the fiber fabric, and the length-to-width ratio is preferably 3 to 6. The detachable hot air outlet devices 12 are arranged in sequence up and down along the running direction of the fabric, and the devices on the same side are evenly arranged, in order to make the fiber fabric in the drying box as evenly blown by the hot air flow as possible; so that the fiber fabric is suspended in the inner cavity of the drying box without touching the box body of the drying box.

[0069] The heating unit 9 is fixedly installed on the top of the drying box body. The explosion-proof fan 8, the heating unit 9, the drying box body 13 and the exhaust gas treatment device 10 are connected in sequence through pipelines. When the equipment is running, the explosion-proof fan 8 starts to suck air into the heating unit 9 for heating, forming a certain amount of high-temperature gas, which flows into the cavity channel b in the drying box body 13 and is blown out through the detachable hot air outlet device 12. The hot air flow contacts the pre-impregnated fabric more evenly and takes away the solvent therein. At the same time, under the action of the hot air, the pre-impregnated fabric is suspended in the cavity channel a of the drying box in a "wave shape". The hot air with the solvent flows into the cavity channel c through the one-way valve 16 and is discharged under the action of the explosion-proof fan 8. When passing through the pipeline connected to the exhaust gas treatment device 10, the solvent condenses into a liquid and is recycled by the solvent recovery device 11. The uncondensed solvent enters the exhaust gas treatment device 10 for treatment and then is discharged. The gas flow direction 14 is shown Figure 3 shown.

[0070] Multiple drying devices can be combined and used according to production needs, and each drying device can be independently temperature controlled.

[0071] Method Example 1

[0072] The main parameters for preparing glass fiber reinforced thermoplastic polyimide fabric prepreg:

[0073] Glass fiber fabric: satin, length 200m, width 1000mm, thickness 0.18mm; resin: thermoplastic polyimide, glass transition temperature 350℃, solvent N,N-dimethylacetamide (DMAC, boiling point about 165℃). Production speed: 2m / min.

[0074] A method for preparing a glass fiber reinforced thermoplastic polyimide fabric prepreg, such as Figure 1 As shown, the following steps are included:

[0075] S1 unwinding, cloth storage and desizing:

[0076] The glass fiber fabric is installed on the unwinding mechanism, and the unwinding tension is set to 10N. The unwinding mechanism can automatically adjust the unwinding speed according to the tension of the glass fiber fabric to maintain a constant tension; the glass fiber fabric is passed through the cloth storage mechanism, and the total storage length is 5 to 20m; then desizing is carried out, and the desizing furnace is heated to 380℃ to 400℃, and the length of the desizing furnace is 10m, and the epoxy sizing agent on the surface of the glass fiber is removed by high temperature.

[0077] S2 one-time dipping:

[0078] The fiber fabric treated in step 1) is introduced into a primary dipping device (such as Figure 2 As shown); weigh a polyimide glue solution with a solid content of 5% to 10% and pour it into the dipping tank 3, guide the fiber fabric treated in step 1) to the glue roller 2 through the cloth guide roller 1, and apply glue to the fiber fabric. The fiber fabric forms a certain wrap angle on the glue roller 2, and the wrap angle is 10° to 145°. Under the squeezing action of the glue roller, the glue roller rotates and the glue adhered to the glue roller will penetrate and impregnate from the side close to the glue roller to the other side of the fabric, and the air between the fabrics is smoothly discharged; then it is introduced into the dipping tank 3 through the breathing roller 4, and after dipping with the dipping roller 5, the excess glue is removed by the metering roller 6 and smoothed by the smoothing roller 7, and the dipping is completed; the running speed of the fiber fabric in the dipping tank 3 is 2m / min. (Consistent with the production speed)

[0079] S3 secondary dipping:

[0080] A conventional dipping device is used. Compared with the primary dipping tank, the difference between the secondary dipping tank and the primary dipping tank is that the secondary dipping tank does not have the coating roller 2 and the breathing roller 4 of the primary dipping tank. The polyimide glue solution with a solid content of 20% is weighed and poured into the secondary dipping tank, and the fiber fabric that has been dipped once is introduced into the secondary dipping tank. The secondary dipping is completed through the action of the dipping roller, metering roller and smoothing roller in the secondary dipping tank; the running speed of the secondary dipped fiber fabric is consistent with step 2).

[0081] S4 pre-baking:

[0082] The temperature of the pre-baking section is set at 120-130°C, and the length of the pre-baking section is 4m. It is mainly used to remove part of the solvent introduced during step 2) and step 3) and retain a certain amount of solvent residue so that the prepreg has a certain laying property and does not warp or wrinkle. At the same time, the solvent should not be too much. On the one hand, if there is too much solvent, it is difficult to ensure the increase of the glue amount in the three dipping processes. On the other hand, if there is too much solvent, it is easy to stick to the roller.

[0083] S5 triple dipping:

[0084] The fiber fabric obtained in the previous step is dipped for the third time using a conventional dipping device. The dipping device and dipping process are the same as the second dipping. The solid content of the polyimide glue is 20%, and the gap between the metering rollers is 0.3-0.5 mm, preferably 0.4 mm.

[0085] S6 Drying:

[0086] The prepreg fabric obtained in step 5) is placed in a drying device for drying at a drying temperature of 155-200°C. The drying box is divided into four temperature zones and connected in series, that is, four drying devices are connected in series, each temperature zone is about 4m long, and the temperature ranges from low temperature to high temperature are 155°C, 160°C, 170°C, and 180°C, respectively. Because the temperature is too low, the solvent evaporates too slowly, the efficiency is low, and the oven length is required to be long. If the temperature is too high, the solvent evaporates too quickly, which easily causes pitting on the surface of the prepreg.

[0087] S7 web guiding and winding:

[0088] The thermoplastic polyimide fabric prepreg obtained in step 6) is corrected and rolled up with a rolling tension of 10N.

[0089] The properties of the prepared thermoplastic polyimide fabric prepreg are shown in Table 1.

[0090] Method Example 2

[0091] The difference from method example 1 is that a mixed solvent [DMAC / DMF (N,N-dimethylformamide) = 1 / 1 (mass ratio)] and different process parameters are used, the boiling point of DMAC is 165° C., the boiling point of DMF is 153° C., and the weighted average boiling point of the mixed solvent is 159° C. (weighted average boiling point of the mixed solvent = 165*1 / 2+153*1 / 2). The specific steps are as follows:

[0092] S1 unwinding, cloth storage and desizing are the same as S1 in method embodiment 1.

[0093] S2 is dipped in glue once, which is the same as S2 in method example 1.

[0094] S3 secondary dipping is the same as S3 in method example 1.

[0095] S4 pre-baking:

[0096] The temperature of the pre-baking section is set at 109-129°C, and the length of the pre-baking section is 4m. It is mainly used to remove part of the solvent introduced during step 2) and step 3) and retain a certain amount of solvent residue so that the prepreg has a certain paving property and does not warp or wrinkle. At the same time, the solvent should not be too much. On the one hand, if there is too much solvent, it is difficult to ensure the increase of the glue amount in the three dipping processes. On the other hand, if there is too much solvent, it is easy to stick to the roller.

[0097] S5 is dipped three times, which is the same as S5 in method example 1.

[0098] S6 Drying:

[0099] The prepreg fabric obtained in step 5) is placed in a drying device for drying at a drying temperature of 149-194°C. The drying box is divided into four temperature zones and connected in series, that is, four drying devices are connected in series, each temperature zone is about 4m long, and the temperature zones are 150°C, 155°C, 165°C, and 180°C from low temperature to high temperature, respectively. Because the temperature is too low, the solvent evaporates too slowly, the efficiency is low, and the oven length required is long. If the temperature is too high, the solvent evaporates too quickly, which easily causes pitting on the surface of the prepreg.

[0100] S7 deviation correction and winding are the same as S7 in method embodiment 1.

[0101] The properties of the prepared thermoplastic polyimide fabric prepreg are shown in Table 1.

[0102] Comparative Example 1

[0103] The difference from method embodiment 1 is that the pre-baking process is reduced, and the specific steps are as follows:

[0104] S1 unwinding, cloth storage and desizing are the same as S1 in method embodiment 1.

[0105] S2 is dipped in glue once, which is the same as S2 in method example 1.

[0106] S3 secondary dipping is the same as S3 in method example 1.

[0107] S4 is three-time dipping, which is the same as S5 in method example 1.

[0108] S5 drying is the same as S6 in method embodiment 1.

[0109] S6 deviation correction and winding are the same as S7 in method embodiment 1.

[0110] The properties of the prepared thermoplastic polyimide fabric prepreg are shown in Table 1.

[0111] Comparative Example 2

[0112] The difference from method embodiment 1 is that the first dipping device is a conventional dipping device. The specific steps are as follows:

[0113] S1 unwinding, cloth storage and desizing are the same as S1 in method embodiment 1;

[0114] S2 is a one-time dipping, in which the fiber fabric treated in step 1) is introduced into a conventional dipping device. Compared with Example 1, there is no glue coating roller and breathing roller, and the fiber fabric is directly and completely immersed in the glue solution to complete a one-time dipping. The solid content of the polyimide glue solution (solvent: DMAC) is 5% to 10%, and the running speed of the fiber fabric in the dipping tank I is 2m / min.

[0115] S3 secondary dipping is the same as S3 in method embodiment 1;

[0116] S4 pre-baking is the same as S4 in method embodiment 1;

[0117] S5 is dipped three times, which is the same as S5 in method example 1;

[0118] S6 drying, which is the same as S6 in method embodiment 1;

[0119] S7 deviation correction and winding are the same as S7 in method embodiment 1.

[0120] The properties of the prepared thermoplastic polyimide fabric prepreg are shown in Table 1.

[0121] Comparative Example 3

[0122] The difference from method embodiment 1 is that a conventional drying device is used. The specific steps are as follows:

[0123] S1 unwinding, cloth storage and desizing are the same as S1 in method embodiment 1;

[0124] S2 is dipped in glue once, which is the same as S2 in method example 1.

[0125] S3 secondary dipping is the same as S3 in method embodiment 1;

[0126] S4 pre-drying is the same as S4 in method embodiment 1, but this embodiment uses a conventional drying device, the drying box has no separate heating partition, and there is no three-layer box design;

[0127] S5 is dipped three times, which is the same as S5 in method example 1;

[0128] S6 drying is the same as S6 in method embodiment 1, but this embodiment uses a conventional drying device, the drying box has no separate heating partition, and there is no three-layer box design;

[0129] S7 deviation correction and winding are the same as S7 in method embodiment 1.

[0130] The properties of the prepared thermoplastic polyimide fabric prepreg are shown in Table 1.

[0131] Comparative Example 4

[0132] The difference from method example 1 is that the concentration of the glue solution used for the first dipping is relatively high, with a solid content of 20%. The specific steps are as follows:

[0133] S1 unwinding, cloth storage and desizing are the same as S1 in method embodiment 1;

[0134] S2 is a one-time dipping. In this embodiment, the solid content of the glue solution used for the one-time dipping is 20%, and the rest is the same as S2 in method embodiment 1.

[0135] S3 secondary dipping is the same as S3 in method embodiment 1;

[0136] S4 pre-baking is the same as S4 in method embodiment 1;

[0137] S5 is dipped three times, which is the same as S5 in method example 1;

[0138] S6 drying, which is the same as S6 in method embodiment 1;

[0139] S7 deviation correction and winding are the same as S7 in method embodiment 1.

[0140] The properties of the prepared thermoplastic polyimide fabric prepreg are shown in Table 1.

[0141] Comparative Example 5

[0142] The difference from method example 1 is that the solid content of the glue used in the second and third dipping is as low as 8%. The specific steps are as follows:

[0143] S1 unwinding, cloth storage and desizing are the same as S1 in method embodiment 1;

[0144] S2 is dipped in glue once, which is the same as S2 in method example 1.

[0145] S3 secondary dipping, in this embodiment, the solid content of the glue solution used for secondary dipping is 8%, and the rest is the same as S3 in method embodiment 1;

[0146] S4 pre-baking is the same as S4 in method embodiment 1;

[0147] S5 is three times of dipping, and the solid content of the glue solution used in the three times of dipping in this embodiment is 8%, and the rest is the same as S5 in method embodiment 1;

[0148] S6 drying, which is the same as S6 in method embodiment 1;

[0149] S7 deviation correction and winding are the same as S7 in method embodiment 1.

[0150] The properties of the prepared thermoplastic polyimide fabric prepreg are shown in Table 1.

[0151] Comparative Example 6

[0152] The difference from method example 1 is that the solid content of the glue used in the second and third dipping is higher than 32%. The specific steps are as follows:

[0153] S1 unwinding, cloth storage and desizing are the same as S1 in method embodiment 1;

[0154] S2 is a one-time dipping. In this embodiment, the solid content of the glue solution used for the one-time dipping is 20%, and the rest is the same as S2 in method embodiment 1.

[0155] S3 secondary dipping, in this embodiment, the solid content of the glue solution used for secondary dipping is 32%, and the rest is the same as S3 in method embodiment 1;

[0156] S4 pre-baking is the same as S4 in method embodiment 1;

[0157] S5 is three times dipped in glue. In this embodiment, the solid content of the glue solution used for the three times dipped in glue is 32%, and the rest is the same as S5 in method embodiment 1;

[0158] S6 drying, which is the same as S6 in method embodiment 1;

[0159] S7 deviation correction and winding are the same as S7 in method embodiment 1.

[0160] The properties of the prepared thermoplastic polyimide fabric prepreg are shown in Table 1.

[0161] Table 1 Thermoplastic polyimide fabric prepreg prepreg properties

[0162]

[0163] It can be seen from Table 1 that the prepregs prepared in Examples 1 and 2 of the present invention have excellent mechanical properties.

[0164] In comparison, the resin content of Comparative Example 1 is relatively low. This is because Comparative Example 1 has no pre-baking process, but instead undergoes two consecutive dips (the third dip is performed directly after the second dip). Since the glue on the fiber fabric is still in a flowing state after the second dip, part of the glue will be driven out of the prepreg under the pressure of gravity and the squeeze of the metering roller, making it difficult to increase the glue amount on the prepreg.

[0165] Although the resin content of Comparative Example 2 is close to that of Example 1, the tensile, bending, impact and other strengths are lower than those of Example 1. This is because the conventional dipping device is used for the one-time dipping in Comparative Example 2. Compared with Example 1, there is no glue coating roller and breathing roller. The fiber fabric is directly and completely immersed in the glue liquid to complete the one-time dipping. The lack of exhaust process can easily lead to bubble inclusion, which can easily lead to insufficient impregnation of the glue liquid into the fabric fiber, and the mechanical properties of the prepreg are affected.

[0166] Although the resin content of Comparative Example 3 is close to that of Example 1, its tensile, bending, impact and other strengths are lower than those of Example 1. This is due to the conventional drying device used in Comparative Example 3. First, the conventional drying device has no temperature partition. When the drying temperature is set to a high level, the solvent evaporates in large quantities at the same time, which easily causes bubbling on the surface of the prepreg, resulting in pitting and insufficient fiber impregnation. When the drying temperature is set to a low level, although the bubbling or pitting phenomenon is controlled, the solvent volatilization is not sufficient, and the volatile content is high, resulting in reduced mechanical properties of the prepreg. Second, the conventional drying device has no multi-layer design and no solvent recovery device in the drying box body, and its heat and solvent utilization rate are obviously relatively lower than the drying device designed in the present invention. At the same time, the conventional drying device has no multi-layer design in the drying box body, and the solvent-free hot air and the exhaust gas containing the solvent cannot be fully isolated, resulting in the obstruction of solvent volatilization in the prepreg, the high volatile content, and the affected mechanical properties of the prepreg.

[0167] The tensile, bending and impact strengths of Comparative Example 4 are lower than those of Example 1. This is because the concentration of the glue used in the first dipping is too high, and the increase in the concentration of the glue will inevitably lead to an increase in the viscosity of the glue, and a decrease in the impregnation and penetration ability of the glue on the fiber fabric. If the glue does not fully impregnate the fiber, the corresponding prepreg performance will decrease.

[0168] The tensile, bending and impact strengths of Comparative Example 5 are lower than those of Example 1. This is because the concentration of the glue used in the secondary and tertiary dipping is too low. Although multiple dippings are used, the resin content of the prepreg is still low, and the mechanical properties of the prepreg are low.

[0169] The tensile, bending and impact strengths of Comparative Example 6 are lower than those of Example 1. This is because the concentration of the glue used in the secondary and tertiary dipping is too high, the resin glue is close to a paste, and the fluidity and impregnation are poor. Although multiple dippings are used, the viscosity of the resin glue is poor, the fiber cannot be fully impregnated, and the resin adhering to the surface of the prepreg is also less, resulting in a low resin content in the prepreg and low mechanical properties of the prepreg.

Claims

1. A method for preparing thermoplastic polyimide fabric prepreg, comprising unwinding, storing and desizing, characterized in that: It also includes primary dipping, secondary dipping, pre-baking, tertiary dipping and drying. The specific steps are as follows: 1) Unwinding, cloth storage and desizing The fiber fabric is unrolled, stored and then desized according to conventional processes; 2) One-time dipping The fiber fabric treated in step 1) is introduced into a primary dipping device, which is composed of a dipping tank (3), a glue coating roller (2), a breathing roller (4) and a dipping roller (5); a polyimide glue solution with a solid content of 1% to 10% is weighed and poured into the dipping tank (3); the fiber fabric treated in step 1) is introduced onto the glue coating roller (2) through a cloth guide roller (1) to coat the fiber fabric with glue, and then the coated fiber fabric is introduced into the dipping tank (3) through a breathing roller (4) and a dipping roller (5) to complete the primary dipping; the fiber fabric runs in the dipping tank (3) at a speed of 1 to 4 m / min; the polyimide glue solution is a mixture of a thermoplastic polyimide resin and a solvent; 3) Secondary dipping The fiber fabric obtained in step 2) is subjected to secondary dipping using a conventional dipping device, wherein the solid content of the polyimide adhesive is 10% to 30%; the running speed of the secondary dipping fiber fabric is the same as that of step 1); 4) Pre-baking The fiber fabric obtained in step 3) is placed in a drying device for pre-drying, and the pre-drying temperature is 30°C to 50°C lower than the boiling point of the solvent; 5) Three times dipping The fiber fabric obtained in step 4) is dipped three times using a conventional dipping device, the solid content of the polyimide glue solution is 10% to 30%, and the dipping process is the same as step 3); 6) Drying The prepreg fabric (15) obtained in step 5) is placed in a drying device for drying to obtain a thermoplastic polyimide fabric prepreg; the drying temperature is (solvent boiling point -10 to +35)°C, and the drying time is not less than 5 minutes.

2. The method for preparing a thermoplastic polyimide fabric prepreg according to claim 1, characterized in that: The first dipping in step 2) is carried out at room temperature for 15 to 60 seconds.

3. The method for preparing a thermoplastic polyimide fabric prepreg according to claim 1, characterized in that: The solid content of the polyimide glue in step 2) is 5% to 8%.

4. The method for preparing thermoplastic polyimide fabric prepreg according to claim 1, characterized in that: The solvent is one or two of N,N-dimethylacetamide and N,N-dimethylformamide; for a mixed solvent, the boiling point of the solvent in step 4) and step 6) is a weighted average of the boiling points of the mixed solvent, and the weighted average of the boiling points of the mixed solvent is the sum of the products of the boiling points of each solvent and their mass percentage in the mixed solvent.

5. The method for preparing thermoplastic polyimide fabric prepreg according to claim 1, characterized in that: The drying tunnel length of the drying device in step 4) is shorter than the drying tunnel length in step 6).

6. The method for preparing thermoplastic polyimide fabric prepreg according to claim 5, characterized in that: In the step 6), the drying tunnel length of the drying device is 5m to 20m, and the prepreg running speed is 1 to 4m / min.

7. The device for preparing thermoplastic polyimide fabric prepreg according to any one of claims 1 to 6, characterized in that: The invention comprises a primary glue dipping device and a drying device. The primary glue dipping device is composed of a glue coating roller (2), a glue dipping tank (3), a breathing roller (4) and a glue dipping roller (5). The glue coating roller (2) is composed of a thick stick and two thin rollers. The two thin rollers are symmetrically distributed on both sides of the thick roller. The center line of the three rollers is in a "V" shape. The "V" shape angle is 90° to 145°. The breathing roller (4) is a roller that can be raised and lowered and adjusted. It is installed above the glue dipping tank (3) and can move up and down. The relative position of the axis of the breathing roller (4) is between the glue coating roller (2) and the glue dipping roller (5).

8. The device for preparing thermoplastic polyimide fabric prepreg according to claim 7, characterized in that: The drying device is composed of a drying box body (13), an explosion-proof fan (8), a heating unit (9) and an exhaust gas treatment device (10), wherein the drying box body (13), the explosion-proof fan (8), the heating unit (9) and the exhaust gas treatment device (10) are connected by pipelines; the heating unit (9) is fixedly installed on the top of the drying box body (13); the drying box body (13) is composed of a three-layer structure, the inner cavity of the box body is a cavity channel a (17), a cavity channel b (18) is provided between the inner layer and the middle layer, and a cavity channel c (19) is provided between the middle layer and the outer layer; a detachable hot air outlet device (12) is installed in the inner layer of the box body, and the cavity channel a is connected with the cavity channel b through the detachable hot air outlet device (12); a plurality of evenly distributed holes are provided at one end of the detachable hot air outlet device (12) away from the inner wall of the box body; and a plurality of one-way valves (16) are provided between the cavity channel a and the cavity channel c.

9. The thermoplastic polyimide fabric prepreg special device according to claim 8, characterized in that: The detachable hot air outlet device (12) is a trapezoidal structure with a hollow interior, and is arranged in an alternating manner up and down, and the detachable hot air outlet devices on the same side are evenly arranged.

10. The device for preparing thermoplastic polyimide fabric prepreg according to claim 9, characterized in that: The diameter of the holes on the detachable hot air outlet device is 0.5 to 1 cm, and the hole density is 2500 / m 2 ~10000pcs / m 2 The ratio of the length of the air outlet surface of the detachable hot air outlet device to the width of the fiber fabric is (3-6):1.

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