Method for manufacturing thermoplastic polyimide fabric prepreg and special device thereof

Abstract

The application provides a thermoplastic polyimide prepreg preparation method and a special device thereof, and preparation includes unwinding, cloth storage and desizing, one-time impregnation, secondary impregnation, pre-drying, three-time impregnation and drying and the like. The application adopts three-time impregnation process and special one-time impregnation device and drying device, realizes solvent method preparation of high-performance thermoplastic prepreg, and solves the problems of low resin content, insufficient impregnation, insufficient flatness of the prepreg, and defects such as air holes and pitting. The method has high preparation efficiency and less wear, the prepared prepreg has uniform fiber impregnation, smooth surface, uniform thickness, high strength and impact resistance, can be stored for a long time and recycled, and is suitable for manufacturing of resin prepreg with high melt viscosity and soluble in proper single or mixed solvent. The prepared prepreg can be applied to the manufacturing of lightweight high-performance parts in the fields of rail transportation, aerospace, weapons and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite material forming, in particular to a preparation method of thermoplastic polyimide fabric prepreg. BACKGROUND

[0002] The solvent method is a common preparation method of thermosetting fabric prepreg, which usually involves impregnating the fiber fabric with a certain concentration of resin glue solution, and then removing most of the solvents in the glue solution by heating to obtain a uniformly impregnated fabric prepreg.

[0003] In China, the preparation process of high-performance thermoplastic composites is mostly evolved from the preparation process of thermosetting composites, or directly uses the equipment for preparing thermosetting fabric prepreg to prepare thermoplastic prepreg. No specific adjustment is made for the characteristics of certain resins, resulting in low resin content, insufficient impregnation, insufficient flatness of the prepreg, and defects such as air holes and pitting when preparing high-performance thermoplastic prepreg by the solvent method.

[0004] For example, for the preparation of high-performance thermoplastic prepreg by the solvent method, compared with most thermosetting resin solutions, the viscosity of thermoplastic resins such as TPI and PEI is larger, and it is more difficult to fully impregnate the reinforcing fibers. Therefore, a low-solid-content glue solution is used 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 impregnation difficulty will increase accordingly. Continuous double impregnation can increase the resin content of the prepreg, but the degree of increase is limited. After the preparation of the prepreg is completed, using the prepreg to repeat the process of preparing the prepreg can increase the resin content of the prepreg, but the preparation efficiency is obviously reduced, and the friction with the equipment also increases the damage probability of the prepreg. SUMMARY

[0005] In view of the problems of low resin content, insufficient impregnation, insufficient flatness of the prepreg, and defects such as air holes and pitting in the existing solvent method for preparing thermoplastic prepreg, the present application provides a preparation method of high-performance thermoplastic prepreg, and also provides a special device. The resin is fully impregnated into the fibers, and the resin content of the prepreg is increased, so that high-performance thermoplastic composites are prepared.

[0006] The present application mainly realizes the solvent method for preparing high-performance thermoplastic prepreg by using a special structure design of the first impregnation device, the drying device, and the design of fully impregnating the fabric with a low-concentration glue solution, exhausting, first impregnation pre-drying, and second impregnation drying to increase the glue amount. A high-performance thermoplastic prepreg with uniform impregnation, high resin content, and flat surface is obtained.

[0007] The preparation method of the present application is different from the prior art in the following aspects: three impregnation processes are adopted, wherein the first impregnation process adopts polyimide glue solution with small concentration (solid content 1%~10%), the strong penetration of the dilute solution is used to pre-impregnate the fiber fabric, and the single-sided glue application mode is adopted, so that the solution with small concentration has sufficient time to fully impregnate the fiber fabric and discharge the air in the fabric, thereby solving the problem that the polyimide is difficult to completely impregnate the fabric; the second and third impregnation processes adopt polyimide glue solution with large concentration (solid content 10%~30%), because the solubility of the polyimide polymer in the solvent is limited, when the solid content is more than 30%, the polyimide cannot be completely dissolved, but swells to a paste state and cannot be used, and with the increase of the solid content, the difficulty of impregnating the fiber with the polyimide glue solution also gradually increases, and when the solution with small solid content is used, the glue content of the prepreg is difficult to increase, therefore, the second and third impregnation processes are adopted to increase the glue content or the glue content of the prepreg; two drying processes are adopted, wherein the pre-drying section is used to dry most of the solvent of the first and second impregnation processes, and to preliminarily impregnate and shape the polyimide in the fiber fabric; the drying section is used to completely dry the residual solvent in the pre-drying section and the solvent newly brought in by the third impregnation process.

[0008] The specific technical solutions adopted by the present application are as follows:

[0009] A thermoplastic polyimide fabric prepreg preparation method, comprising unwinding, fabric storage and desizing, first impregnation, second impregnation, pre-drying, third impregnation, drying, and the specific steps are as follows:

[0010] 1) unwinding, fabric storage and desizing

[0011] The fiber fabric is unwound, stored and desized according to the conventional process;

[0012] 2) first impregnation

[0013] The fiber fabric treated in step 1) is introduced into the first impregnation device, which is composed of an impregnation tank 3, a glue applying roller 2, a breathing roller 4 and an impregnation roller 5; the polyimide glue solution with a solid content of 1%~10% is weighed and poured into the impregnation tank 3, the fiber fabric treated in step 1) is introduced onto the glue applying roller 2 through the fabric guide roller 1, the fiber fabric is coated with glue, and then the coated fiber fabric is introduced into the impregnation tank 3 through the breathing roller 4 and the impregnation roller 5, to complete the first impregnation; the running speed of the fiber fabric in the impregnation tank 3 is 1~4 m / min, and the polyimide glue solution is a mixture of thermoplastic polyimide resin and solvent;

[0014] 3) second impregnation

[0015] The conventional impregnation device is used for the second impregnation of the fiber fabric obtained in step 2), and the solid content of the polyimide glue solution is 10%~30%; the running speed of the second impregnated fiber fabric is consistent with that of step 1).

[0016] 4) Pre-baking

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

[0018] 5) Third dipping

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

[0020] 6) Drying

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

[0022] Further, the first dipping in step 2) is carried out at room temperature, the dipping time is 0.25-1 min, and the fabric tension is constant to ensure that the fabric can be evenly and flatly unfolded, and the solvent is one or both of N,N-dimethylacetamide and N,N-dimethylformamide.

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

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

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

[0026] Preferably, the length of the drying channel of the drying device in step 4) is less than the length of the drying channel in step 6), which is to keep a certain tackiness of the prepreg after the residual solvent (usually 5-15%) is removed by pre-baking, so as to prevent the prepreg from being too hard and curling.

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

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

[0029] The application also provides a primary impregnation device and a drying device specially used for preparing thermoplastic polyimide fabric prepreg, the primary impregnation device is composed of an impregnation tank 3, a glue coating roller 2, a breathing roller 4 and an impregnation roller 5, the glue coating roller is composed of a thick roller and two thin rollers, the two thin rollers are symmetrically distributed on the two sides of the thick roller, and the center line of the three rollers is in the shape of a V; the breathing roller 4 is a liftable roller installed above the impregnation tank 3 and can move up and down, and the relative position of the axis of the breathing roller 4 is between the glue coating roller 2 and the impregnation roller 5.

[0030] The angle of the V-shaped glue coating roller 2 is 90-145° and can be adjusted, the thick roller is installed on the impregnation tank 3, and the diameter of the thick roller is slightly smaller than 2 times the maximum height of the glue liquid in the impregnation tank, the lower half of the thick roller is in the impregnation tank, and the upper half of the thick roller is higher than the plane of the impregnation tank, the gap between the two thin rollers and the thick roller should not be too large, and the fabric can form a certain coating on the upper surface of the thick roller to ensure that the included angle is greater than or equal to 10°, and the lower surfaces of the two thin rollers are higher than the liquid level of the glue liquid, so that the fabric can not directly immerse in the glue liquid when passing through the glue coating roller and the exhaust is not invalid.

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

[0032] The device used for secondary impregnation and tertiary impregnation is a conventional device, which has the functions of conveying, impregnation, extruding glue liquid and fabric and wiping glue liquid.

[0033] The drying device is composed of a drying box body 13, an explosion-proof fan 8, a heating unit 9 and a waste gas treatment device 10, and the drying box, the explosion-proof fan 8, the heating unit 9 and the waste gas treatment device 10 are connected through pipelines; the heating unit 9 is fixedly installed at the top end of the drying box body; the drying box body 13 is composed of three layers, the inner cavity of the box body is a cavity passage a, a cavity passage b is arranged between the inner layer and the middle layer, a cavity passage c is arranged between the middle layer and the outer layer, the inner layer of the box body is provided with a detachable hot air outlet device 12, the cavity passage a is communicated with the cavity passage b through the detachable hot air outlet device 12; a plurality of uniformly arranged holes are arranged at the end of the inner wall of the cavity passage a away from the box body; a plurality of one-way valves 16 are arranged between the cavity passage a and the cavity passage c, the number and position of the one-way valves are not limited, and the cavity passage b is closed at the position of the one-way valve, so that the gas in the cavity passage a flows to the cavity passage c under a certain pressure and prevents backflow.

[0034] Further, the detachable hot air outlet device 12 is a hollow trapezoidal body structure, and the devices are arranged in an up-and-down staggered manner and uniformly arranged on the same side, so that the fiber fabric in the drying box can be blown by the hot air flow as uniformly as possible; and the fiber fabric is suspended in the inner cavity of the drying box body and does not touch the drying box body.

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

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

[0037] Further, the minimum temperature of the drying oven is not higher than 40℃.

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

[0039] The drying temperature in step 6) is higher than the pre-drying temperature in step 4), and the length of the drying channel is longer, which aims to completely dry the solvent of the third impregnation. Generally, the longer the length of the drying section, the more conducive to the drying of the solvent. However, the site and the length of the single fabric roll should also be considered.

[0040] Since the solvent is mostly a volatile and flammable chemical, the drying oven is designed to be explosion-proof. The air is pumped in by the explosion-proof motor after being heated, and the air inlet channel is separated from the exhaust gas outlet channel, which avoids the pollution of the pumped air and can effectively remove the solvent in the prepreg. The exhaust gas containing solvent is discharged in time under the action of the explosion-proof fan to avoid the risk of excessive concentration. The solvent in the exhaust gas is cooled and condensed, and can be recycled.

[0041] ​The unwinding provides constant tension for the whole fabric, guarantees that the fabric is stably and flatly unwound, sets the unwinding tension according to the need, and generally sets 5N-50N; the fabric 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, the length of the fabric storage can be adjusted to provide time for the connection of two rolls of fabric, and guarantee that the prepreg preparation is stably and continuously carried out without stopping; the desizing is to decompose the sizing agent on the surface of the fabric by high-temperature heating and remove it under negative pressure; the desizing is to remove the epoxy sizing agent with low temperature resistance on the surface of the fiber fabric, prevent the decomposition of the epoxy sizing agent at a higher processing temperature to produce impurities, and affect the performance of the polyimide prepreg molded product; the desizing temperature should be above the decomposition temperature of the sizing agent, the sampling is analyzed by scanning electron microscopy, the outer surface of the fiber has clear grooves, and no other irregular impurities, which proves that the desizing treatment is completed, and the desizing time should be not less than 5min.

[0042] In order to facilitate regular winding, a deviation correcting device and a winding device can be used to regularly wind the prepreg, the deviation correcting device is located in front of the winding device, timely corrects the movement track of the prepreg, and makes the prepreg winding neat; the winding device is a coiling device with a motor, the motor drives the roller to rotate, and the prepreg is coiled. The deviation correction can adopt any one of photoelectric, mechanical and other forms of deviation correction system, the purpose is to timely adjust the continuously prepared fabric prepreg, prevent the prepreg from deviating and twisting, keep the surface flat, and guarantee that the winding is neat. The winding can adopt one of several forms of servo winding, magnetic powder control motor winding and mechanical winding, and the preferred form is servo winding. The winding speed should match the unwinding and glue immersion speed, and 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 the production needs, a plurality of drying boxes can be connected in series to form a drying channel with a length meeting the needs, the drying boxes can be independently temperature-controlled, and the number of series connection can be selected according to the needs.

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

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

[0046] (1) The application adopts three glue immersion processes, one of which uses polyimide glue with a small concentration (solid content 1%-10%) and a one-time glue immersion device designed by the application to discharge air in the fabric on one side and solve the problem that polyimide is difficult to fully immerse the fabric in the prior art; the other two use polyimide glue with a large concentration (solid content 10%-30%) to increase the amount of glue and the glue content of the prepreg, and three times of glue immersion solves the problem that thermoplastic polyimide is difficult to fully immerse the fabric fibers;

[0047] (2) The drying of the present application adopts two-stage drying process, the pre-drying stage mainly dries most of the solvents of the first and second dipping glues, and makes the polyimide preliminarily dip the fiber fabric and shape; the drying stage mainly dries the residual solvents of the pre-drying stage and the newly brought solvents of the third dipping glue.

[0048] (3) The present application adopts a specially designed first dipping glue device. The first dipping glue device adopts the design of one side dipping glue exhaust-breathing roller, which is more conducive to the exhaust of air in the glue and fiber fabric compared with direct dipping in glue, realizes the sufficient dipping of the glue to the fiber fabric, and the breathing roller increases the time and distance interval between the first dipping glue and the second dipping glue, which is conducive to increasing the dipping time, making the glue dip the fabric under the action of gravity, making the dipping more sufficient. At the same time, the existence of the dipping roller makes the solvent of the first dipping glue more volatile, and the glue adheres to the gap between the fabric, which is also conducive to improving the glue amount.

[0049] A glue applying roller is arranged in the first dipping glue device, which is composed of one thick roller 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 the shape of "V". By adjusting the angle of the "V" shape, the dipping condition of the fabric is adjusted. The larger the angle of the "V" shape, the greater the contact area and pressure of the fabric with the thick roller, and the more sufficient the dipping and exhaust. The glue adheres to the glue applying roller, and the glue penetrates from one side of the fabric to the other side under the pressure of the roller, while the air between the fabric is exhausted.

[0050] The breathing roller 4 is a liftable and adjustable roller, 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 at a higher position, firstly, the glue penetrates into the gap of the fabric under the action of gravity, and the air is fully exhausted, secondly, the glue in the fabric has sufficient time to volatilize, and after the solvent volatilizes, it is also conducive to improving the glue amount of the second dipping glue.

[0051] The dipping roller 5 is a smooth stainless steel roller, which can rotate synchronously with the fabric to reduce the friction between the fabric and the roller and reduce the damage to the fiber; during production, the fiber fabric runs under the lower part of the dipping roller, and the dipping roller mainly plays a guiding and spreading role to promote the dipping of the glue to the fabric fiber.

[0052] (4) The drying device provided by the application adopts a horizontal design and can independently control temperature in a range of 40-200 DEG C. When in use, air is heated by the heating unit 9 and then sent into the cavity passage b of the box body by the explosion-proof fan 8, and is blown out through the detachable hot air outlet device 12. The detachable hot air outlet device 12 is arranged in an upper-lower staggered manner, and the pre-impregnated fabric 15 is suspended in the drying box in a wavy shape under the action of the upper and lower hot air. The solvent in the pre-impregnated fabric 15 is rapidly volatilized by heating and is taken away by the hot air flow. The hot air flow with solvent is discharged to the waste gas treatment device 10 through the cavity passage c of the box body. In this way, the hot air flow with solvent and the hot air flow without solvent are separated by the middle layer of the box body, so that the hot air flow without solvent is prevented from being polluted by the hot air flow with solvent, and the solvent removal capacity is further improved. Meanwhile, the hot air flow with solvent is entirely wrapped in the outer layer of the hot air flow without solvent to form a heat preservation layer, heat recovery is realized, energy is saved, and the heat energy utilization rate is improved. When the hot air flow with solvent passes through the pipeline connected with the waste gas treatment device 10, the solvent temperature is lowered to below the boiling point of the solvent due to heat exchange with external air, and the solvent is condensed into liquid and is recycled by the solvent recycling device 11. The solvent that is not condensed is discharged after being treated by the waste gas treatment device 10.

[0053] In addition, the drying device designed by the application can be used in series according to production needs, and can be independently controlled in temperature.

[0054] (5) The thermoplastic polyimide fabric prepreg preparation method disclosed by the application realizes three times of impregnation on the fiber fabric, and the fabric impregnation effect is good, the fiber impregnation is uniform and sufficient, and better impregnation can be realized for thermoplastic resins such as TPI and PEI with relatively large melt viscosity. Meanwhile, compared with the method of improving the resin content by repeating the prepreg preparation process once for the finished product with low resin content, the method can realize the preparation of the prepreg with high resin content once, and has high preparation efficiency, less wear, and higher corresponding prepreg strength. The prepreg prepared by the method has uniform fiber impregnation, smooth surface, and uniform thickness, and even high resin content will not cause powder and skin falling, and 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 resins with high melt viscosity and soluble in single or mixed solvents, and the prepared prepreg can be applied to the manufacture of lightweight high-performance parts in various fields of automobiles, rail transportation, aerospace, weapons, etc. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 The thermoplastic polyimide prepreg preparation flowchart

[0057] Figure 2 The structure diagram of the once impregnation device

[0058] Figure 3 The structure diagram of the drying device

[0059] Wherein: 1 - cloth guide roller, 2 - glue roller, 3 - dipping tank, 4 - breathing roller, 5 - dipping roller, 6 - metering roller, 7 - smoothing roller, 8 - explosion-proof fan, 9 - heating unit, 10 - waste gas treatment device, 11 - recovery device, 12 - detachable 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 embodiments of the present application will be further described in detail below in conjunction with the examples and drawings. The following examples are only used to illustrate the present application, but cannot be used to limit the scope of the present application.

[0061] The tensile properties of the prepreg are tested according to GB / T 1040.4-2006, the bending properties are tested according to GB / T 1449-2005, the impact properties are tested according to GB / T 1843-2008, the resin content is tested according to GB / T 2577-2005, and the volatile content is tested according to GB / T 32788.3-2016.

[0062] Device embodiment 1

[0063] The one-time dipping device of the present application is composed of a dipping tank 3, a glue roller 2, a breathing roller 4, and a dipping roller 5, a metering roller 6, and a smoothing roller 7, as shown in Figure 2 Compared with conventional dipping devices, the one-time dipping device of the present application adopts a glue roller 2 and a breathing roller 4 with a specific structure. The glue roller 2 is composed of a thick rod and two thin rollers. The thick rod is fixed in position and installed on the dipping tank 3. Its diameter is slightly smaller than 2 times the maximum glue liquid height in the dipping tank. The lower half is inside the glue tank, and the upper half is above the glue tank plane. The two thin rollers are symmetrically distributed on both sides of the thick roller. The center line of the three rollers forms a "V" shape. The "V" angle can be adjusted by symmetrically adjusting the positions of the two thin rollers. The adjustable range of the "V" angle is 90°-145°. The gap between the two thin rollers and the thick roller should not be too large. It should be ensured that the fabric can form a certain coating on the upper surface of the thick roller to ensure that the wrapping angle is ≥10°. The lower surfaces of the two thin rollers are higher than the glue liquid level. In this way, it is ensured that the fabric will not directly immerse in the glue liquid when passing through the glue roller, and the exhaust will not fail.

[0064] When the prepreg is prepared, the fiber fabric is waved in the shape of "Ω" and sequentially passes through the lower side of one thin roller, the upper side of the thick roller and the lower side of the other thin roller, so that the fabric is wrapped around the thick roller and the thin roller on the upper side of the thick roller, and the wrapping area and pressure of the fabric on the thick roller are adjusted by adjusting the angle of the "V" shape, so that the glue amount and the glue liquid penetration pressure are adjusted.

[0065] The breathing roller 4 is a liftable and adjustable roller, which is installed on a movable support frame above the glue dipping tank 3, and is driven by a motor to move freely up and down, so as to adjust the vertical distance between the lifting roller and the glue liquid, so that after dipping, there is sufficient time to realize the sufficient penetration of the glue liquid to the fabric. The relative position of the axis of the breathing roller 4 is located between the glue coating roller 2 and the glue dipping roller 5. The metering roller 6 is located above the rear part of the glue dipping tank, and the surface is smooth. The gap width between the two rollers of the metering roller can be adjusted. When the fabric with glue liquid passes through the gap between the two rollers, the excess glue liquid is squeezed out under the extrusion of the two rollers. Behind the metering roller is the smoothing roller 7, which is composed of upper and lower rollers, and the surface is smooth. When the prepreg passes through the upper and lower rollers of the smoothing roller, the glue liquid is uniformly flattened and coated on the surface of the fiber fabric under the pressure of the roller.

[0066] The drying device of the present application is composed of a drying box body 13, an explosion-proof fan 8, a heating unit 9 and a waste gas treatment device 10, as shown in the figure. Figure 3 The minimum temperature of the drying box is not higher than 40℃, and the drying box body 13 is composed of three layers. The inner cavity of the box body is a cavity passage a. The cavity passage b is arranged between the inner layer and the middle layer, and the cavity passage c is arranged between the middle layer and the outer layer. The detachable hot air outlet device 12 is installed on the box body on both sides of the cavity passage a. The two ends of the drying box body 13 are open, the box body is closed at the cross section of the opening, and the opening is as small as possible to avoid excessive heat loss, but the fiber fabric should be able to smoothly pass through the two openings without friction with the box body.

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

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

[0069] The heating unit 9 is fixedly installed at the top end of the drying box. The explosion-proof fan 8, the heating unit 9, the drying box 13 and the waste gas treatment device 10 are sequentially connected by pipelines. When the equipment is running, the explosion-proof fan 8 starts to suck air into the heating unit 9 for heating to form a certain high-temperature gas, which flows into the cavity passage b in the drying box 13, is blown out by the detachable hot air outlet device 12, and uniformly contacts the pre-impregnated fabric with the hot air flow, and carries away the solvent therein. Under the action of the hot air, the pre-impregnated fabric is suspended in the drying box cavity passage a in a "wavy shape", the hot air with solvent flows into the cavity passage c through the one-way valve 16, and is discharged under the action of the explosion-proof fan 8. When the hot air passes through the pipeline connected with the waste gas treatment device 10, the solvent is condensed and coagulated into liquid, which is recycled by the solvent recovery device 11. The uncoagulated solvent is discharged after being treated by the waste gas treatment device 10. The gas flow direction 14 is shown in Figure 3

[0070] According to production needs, a plurality of drying devices can be combined for use, and each drying device can independently control the temperature.

[0071] Method embodiment 1

[0072] Main parameters for preparing the glass fiber reinforced thermoplastic polyimide fabric prepreg:

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

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

[0075] S1: unwinding, fabric storage and desizing:

[0076] ​The fiberglass 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 fiberglass fabric to maintain a constant tension. The fiberglass fabric is passed through the storage mechanism, and the total length of the storage fabric is 5 to 20m. Then, desizing is performed. The desizing furnace is heated to 380℃ to 400℃ and the length of the desizing furnace is 10m. The epoxy sizing agent on the surface of the fiberglass is removed by high temperature.

[0077] S2 single impregnation:

[0078] The fiber fabric treated in step 1) is then introduced into a primary impregnation device (such as...). Figure 2 (As shown); Weigh out a polyimide adhesive solution with a solid content of 5% to 10% and pour it into the impregnation tank 3. Guide the fiber fabric treated in step 1) onto the coating roller 2 via the guide roller 1. Coat the fiber fabric with adhesive, forming a certain wrap angle on the coating roller 2 (10° to 145°). Under the squeezing action of the coating roller, the adhesive adhering to the roller will penetrate from one side of the roller to the other side of the fabric, smoothly expelling air between the fabric layers. Then, guide it into the impregnation tank 3 via the breathing roller 4. After impregnation by the impregnation roller 5, remove excess adhesive via the metering roller 6 and smooth it via the smoothing roller 7, completing one impregnation cycle. The running speed of the fiber fabric in the impregnation tank 3 is 2 m / min (consistent with the production speed).

[0079] S3 Secondary Impregnation:

[0080] Using a conventional impregnation device, the difference between the secondary impregnation tank and the primary impregnation tank is that the secondary impregnation tank does not have the coating roller 2 and breathing roller 4 of the primary impregnation tank. A polyimide adhesive solution with a solid content of 20% is weighed and poured into the secondary impregnation tank. The fiber fabric that has been impregnated once is introduced into the secondary impregnation tank. The secondary impregnation is completed by the action of the impregnation roller, metering roller and smoothing roller in the secondary impregnation tank. The running speed of the fiber fabric in the secondary impregnation tank is the same as in step 2).

[0081] S4 Pre-baking:

[0082] The temperature of the pre-drying section is set to 120-130℃, and the length of the pre-drying tunnel is 4m. It mainly removes some of the solvent introduced in steps 2) and 3), leaving a certain amount of solvent residue to ensure that the prepreg has a certain degree of spreadability and to prevent warping and wrinkling. At the same time, the amount of solvent should not be too much. Firstly, if there is too much solvent, it will be difficult to ensure the continued increase of adhesive application in the three impregnation processes. Secondly, if there is too much solvent, it will also be easy for the roller to stick.

[0083] S5 triple impregnation:

[0084] The fiber fabric obtained in the previous step is subjected to third impregnation by using a conventional impregnation device, and the impregnation device and the impregnation process are the same as those in the second impregnation. The solid content of the polyimide glue solution 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 obtained in step 5) is placed in a drying device for drying, and the drying temperature is 155-200°C. The drying oven is divided into four temperature zones and connected in series, that is, four drying devices are connected in series, and the length of each temperature zone is about 4 m. The temperature zones from low to high are 155°C, 160°C, 170°C and 180°C. If the temperature is too low, the solvent volatilizes too slowly, which is low in efficiency and requires a longer oven. If the temperature is too high, the solvent volatilizes too quickly, which easily causes the formation of spots on the surface of the prepreg.

[0087] S7 rectification and winding:

[0088] The thermoplastic polyimide fabric prepreg obtained in step 6) is subjected to rectification and winding, and the winding tension is 10 N.

[0089] The properties of the thermoplastic polyimide fabric prepreg prepared 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 (the weighted average boiling point of the mixed solvent = 165*1 / 2 + 153*1 / 2). The specific steps are as follows:

[0092] S1 unwinding, storage and desizing, which is the same as S1 in Method Example 1.

[0093] S2 first impregnation, which is the same as S2 in Method Example 1.

[0094] S3 second impregnation, which is the same as S3 in Method Example 1.

[0095] S4 pre-drying:

[0096] The pre-drying section is set to 109-129°C, and the pre-drying section has a length of 4 m. The pre-drying section is mainly used to dry part of the solvent introduced in steps 2) and 3), and a certain amount of solvent is retained to make the prepreg have a certain lay-up property and ensure that no wrinkles are generated. At the same time, the solvent should not be too much. On the one hand, if the solvent is too much, it is difficult to ensure the increase of the glue amount in the process of the third impregnation. On the other hand, if the solvent is too much, it is also easy to cause the sticking of the rollers.

[0097] S5 drying, same as S6 in method example 1.

[0098] S6 drying:

[0099] The prepreg fabric obtained in step 5) is placed in a drying device for drying, the drying temperature is 149-194℃, the drying oven is divided into four temperature zones and connected in series, that is, four drying devices are connected in series, and each temperature zone is about 4m long, from low temperature to high temperature, they are 150℃, 155℃, 165℃ and 180℃ in turn. If the temperature is too low, the solvent volatilizes too slowly, which is low in efficiency and requires a longer oven. If the temperature is too high, the solvent volatilizes too quickly, which is easy to cause the surface of the prepreg to have pockmarks.

[0100] S7 rectification and winding, same as S7 in method example 1.

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

[0102] Comparative example 1

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

[0104] S1 unwinding, fabric storage and desizing, same as S1 in method example 1.

[0105] S2 first impregnation, same as S2 in method example 1.

[0106] S3 second impregnation, same as S3 in method example 1.

[0107] S4 third impregnation, same as S5 in method example 1.

[0108] S5 drying, same as S6 in method example 1.

[0109] S6 rectification and winding, same as S7 in method example 1.

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

[0111] Comparative example 2

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

[0113] S1 unwinding, fabric storage and desizing, same as S1 in method example 1;

[0114] S2 first dip, the fiber fabric treated in step 1) is introduced into a conventional dip device, compared with example 1, without glue roller and breathing roller, the fiber fabric is directly and completely immersed in the glue solution, the first dip is completed, the solid content of the polyimide glue solution (solvent: DMAC) is 5% to 10%, and the running speed of the fiber fabric in the dip tank I is 2 m / min.

[0115] S3 second dip, same as S3 in method example 1;

[0116] S4 pre-drying, same as S4 in method example 1;

[0117] S5 third dip, same as S5 in method example 1;

[0118] S6 drying, same as S6 in method example 1;

[0119] S7 deviation correction and winding, same as S7 in method example 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 example 1 is that a conventional drying device is used. The specific steps are as follows:

[0123] S1 unwinding, fabric storage and desizing, same as S1 in method example 1;

[0124] S2 first dip, same as S2 in method example 1.

[0125] S3 second dip, same as S3 in method example 1;

[0126] S4 pre-drying, same as S4 in method example 1, but the example uses a conventional drying device, the drying oven has no separate heating zone, and has no three-layer box design;

[0127] S5 third dip, same as S5 in method example 1;

[0128] S6 drying, same as S6 in method example 1, but the example uses a conventional drying device, the drying oven has no separate heating zone, and has no three-layer box design;

[0129] S7 deviation correction and winding, same as S7 in method example 1.

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

[0131] Comparative example 4

[0132] The difference between the method embodiment 1 is that the first dipping uses a higher concentration of glue solution, with a solid content of 20%. The specific steps are as follows:

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

[0134] S2 first dipping, in this embodiment, the first dipping uses a glue solution with a solid content of 20%, and other steps are the same as S2 in method embodiment 1.

[0135] S3 second dipping, which is the same as S3 in method embodiment 1;

[0136] S4 pre-drying, which is the same as S4 in method embodiment 1;

[0137] S5 third dipping, which is the same as S5 in method embodiment 1;

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

[0139] S7 rectification and winding, which is 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 between the method embodiment 1 is that the second dipping and the third dipping use a lower concentration of glue solution, with a solid content of 8%. The specific steps are as follows:

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

[0144] S2 first dipping, which is the same as S2 in method embodiment 1.

[0145] S3 second dipping, in this embodiment, the second dipping uses a glue solution with a solid content of 8%, and other steps are the same as S3 in method embodiment 1;

[0146] S4 pre-drying, which is the same as S4 in method embodiment 1;

[0147] S5 third dipping, in this embodiment, the third dipping uses a glue solution with a solid content of 8%, and other steps are the same as S5 in method embodiment 1;

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

[0149] S7 rectification and winding, which is 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 between the method embodiment 1 is that the secondary impregnation, three times of impregnation uses the glue liquid solid content of 32%. The specific steps are as follows:

[0153] S1, the same as S1 in method embodiment 1, the fiber fabric is unwound, stored and desized.

[0154] S2, the first impregnation, the first impregnation in this embodiment uses the glue liquid solid content of 20%, and the other is the same as S2 in method embodiment 1.

[0155] S3, the second impregnation, the second impregnation in this embodiment uses the glue liquid solid content of 32%, and the other is the same as S3 in method embodiment 1.

[0156] S4, the same as S4 in method embodiment 1.

[0157] S5, the third impregnation, the third impregnation in this embodiment uses the glue liquid solid content of 32%, and the other is the same as S5 in method embodiment 1.

[0158] S6, the same as S6 in method embodiment 1.

[0159] S7, the same as S7 in method embodiment 1.

[0160] The performance of the prepared thermoplastic polyimide fabric prepreg is shown in table 1.

[0161] Table 1 thermoplastic polyimide fabric prepreg performance

[0162]

[0163] As can be seen from table 1, the mechanical properties of the prepreg prepared by example 1 and example 2 of the present application are excellent.

[0164] Compared with the comparative example 1, the resin content is low, which is due to the fact that the comparative example 1 has no pre-drying process, but continuous twice impregnation (the third impregnation directly after the second impregnation), because the glue liquid on the fiber fabric is still in a flowing state after the second impregnation, part of the glue liquid will also be pushed out of the prepreg under the gravity and the extrusion of the metering roller, resulting in the difficulty in improving the glue content of the prepreg.

[0165] Although the resin content of the comparative example 2 is close to that of example 1, the tensile, bending and impact strength is lower than that of example 1. This is because the first impregnation of the comparative example 2 uses a conventional impregnation device, which has no glue coating roller and breathing roller compared with example 1, and the fiber fabric directly and completely immerses in the glue liquid, and the first impregnation is completed, and there is no exhaust process, which is easy to lead to air bubble inclusion, which is easy to lead to the fact that the glue liquid does not fully impregnate the fabric fiber, and the mechanical properties of the prepreg are affected.

[0166] Comparative Example 3 has a resin content close to that of Example 1, but the tensile, bending, impact and other strengths are lower than those of Example 1. This is because the conventional drying device used in Comparative Example 3 has no temperature zoning, and when the drying temperature is set to be high, the solvent volatilizes in large quantities at the same time, which easily causes bubbling on the surface of the prepreg and results in pinholes, and the fibers are not sufficiently impregnated. When the drying temperature is set to be low, although the bubbling or pinhole phenomenon is controlled, the solvent volatilization is not sufficient, the volatile content is high, and the mechanical properties of the prepreg are reduced. In addition, the conventional drying device has no multilayer design of the drying box body and no solvent recovery device, and the heat and solvent utilization rate is obviously lower than that of the drying device designed in the present application. At the same time, the conventional drying device has no multilayer design of the drying box body, and the hot air containing solvent and the waste gas containing solvent cannot be fully separated, which hinders the volatilization of the solvent in the prepreg, the volatile content is high, and the mechanical properties of the prepreg are affected.

[0167] Comparative Example 4 has lower tensile, bending, impact and other strengths than Example 1. This is because the glue solution concentration used in the first impregnation is too high, and the increase in the glue solution concentration will inevitably lead to the increase in the viscosity of the glue solution, the decrease in the impregnation and penetration ability of the glue solution to the fiber fabric, and the insufficient impregnation of the glue solution to the fiber. Therefore, the performance of the prepreg will be reduced.

[0168] Comparative Example 5 has lower tensile, bending, impact and other strengths than Example 1. This is because the glue solution concentration used in the second and third impregnations is too low, and although multiple impregnations are used, the resin content of the prepreg is still low, and the mechanical properties of the prepreg are low.

[0169] Comparative Example 6 has lower tensile, bending, impact and other strengths than Example 1. This is because the glue solution concentration used in the second and third impregnations is too high, and the resin glue solution tends to be paste-like, with poor flowability and impregnation. Although multiple impregnations are used, the viscosity of the resin glue solution is poor, the fibers cannot be sufficiently impregnated, and the amount of resin adhered to the surface of the prepreg is also small, resulting in a low resin content of the prepreg and low mechanical properties of the prepreg.

Claims

1. A method for manufacturing a thermoplastic polyimide fabric prepreg, comprising unwinding, storing and debulking, characterized in that, It also includes once impregnation, twice impregnation, pre-baking, three times impregnation and drying, the specific steps are as follows: 1) unwinding, storage and desizing The fiber fabric is unwound, stored and desized according to the conventional process; 2) once impregnation The fiber fabric treated in step 1) is introduced into the once impregnation device, which is composed of an impregnation tank (3), a coating roller (2), a breathing roller (4) and an impregnation roller (5). The breathing roller (4) is installed on the movable support frame above the impregnation tank (3). Weigh the polyimide glue solution with a solid content of 1%~10% and pour it into the impregnation tank (3). The fiber fabric treated in step 1) is introduced into the coating roller (2) through the guide roller (1), and the fiber fabric is coated to ensure that the fabric does not directly immerse in the glue solution when passing through the coating roller. Then the coated fiber fabric is introduced into the impregnation tank (3) through the breathing roller (4) and the impregnation roller (5) to complete the once impregnation. The running speed of the fiber fabric in the impregnation tank (3) is 1~4m / min. The polyimide glue solution is a mixture of thermoplastic polyimide resin and solvent; 3) twice impregnation The fiber fabric obtained in step 2) is impregnated twice by using a conventional impregnation device, and the solid content of the polyimide glue solution is 10%~30%. The running speed of the twice impregnated fiber fabric is the same as that in step 1); 4) pre-baking The fiber fabric obtained in step 3) is placed in a drying device for pre-baking, and the pre-baking temperature is lower than the boiling point of the solvent by 30~50℃; 5) three times impregnation The fiber fabric obtained in step 4) is impregnated three times by using a conventional impregnation device, and the solid content of the polyimide glue solution is 10%~30%. The impregnation process is the same as that in step 3); 6) drying The pre-impregnated fabric (15) obtained in step 5) is placed in a drying device to obtain a thermoplastic polyimide fabric pre-impregnated material. The drying temperature is the boiling point of the solvent minus 10~+35℃, and the drying time is not less than 5min.

2. The method of making a thermoplastic polyimide fabric prepreg according to claim 1, wherein: The once impregnation in step 2) is carried out at room temperature, and the impregnation time is 15~60s.

3. The method of making a thermoplastic polyimide fabric prepreg according to claim 1, wherein: The solid content of the polyimide glue solution in step 2) is 5%~8%.

4. The method of making a thermoplastic polyimide fabric prepreg according to claim 1, wherein: The solvent is one or both of N,N-dimethylacetamide and N,N-dimethylformamide. For mixed solvents, the boiling point of the solvent in steps 4) and 6) is the weighted average of the boiling points of the mixed solvents, which is the sum of the product of the boiling point of each solvent and its mass percentage in the mixed solvent.

5. The method of making a thermoplastic polyimide fabric prepreg according to claim 1, wherein: The length of the drying channel of the drying device in step 4) is less than that in step 6).

6. The method of making a thermoplastic polyimide fabric prepreg according to claim 5, wherein: The length of the drying channel of the drying device in step 6) is 5~20m, and the running speed of the pre-impregnated material is 1~4m / min.

7. The apparatus according to any one of claims 1 to 6, wherein the apparatus is used for the production method of the thermoplastic polyimide fabric prepreg according to any one of claims 1 to 6. The utility model relates to a one-time impregnation device and drying device, the one-time impregnation device is composed of a glue coating roller (2), an impregnation groove (3), a breathing roller (4) and an impregnation roller (5), the glue coating roller (2) is composed of a thick stick, two thin rollers, the two thin rollers are symmetrically distributed on the two sides of the thick stick, the center line of the three rollers is in the shape of V, and the angle of V is 90~145 degrees, the breathing roller (4) is a liftable and adjustable roller, is installed above the impregnation groove (3) and can move up and down, and the axis of the breathing roller (4) is located between the glue coating roller (2) and the impregnation roller (5).

8. The apparatus for the preparation of 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 a waste gas treatment device (10), the drying box body (13), the explosion-proof fan (8), the heating unit (9) and the waste gas treatment device (10) are connected through pipelines, the heating unit (9) is fixedly installed at the top end of the drying box body (13), the drying box body (13) is composed of three layers, the inner cavity of the box body is a cavity passage a (17), cavity passage b (18) is arranged between the inner layer and the middle layer, cavity passage c (19) is arranged between the middle layer and the outer layer, the inner layer of the box body is provided with a detachable hot air outlet device (12), the cavity passage a is communicated with the cavity passage b through the detachable hot air outlet device (12), a plurality of uniformly arranged holes are arranged at the 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 arranged between the cavity passage a and the cavity passage c.

9. The apparatus for the preparation of thermoplastic polyimide fabric prepreg according to claim 8, characterized in that: The detachable hot air outlet device (12) is a hollow trapezoidal body structure, and the upper and lower detachable hot air outlet devices are staggered, and the detachable hot air outlet devices on the same side are uniformly arranged.

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

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