RU2743422C1 - Method for impregnation of layered blinks based on woven fillers and epoxy, organosilicon and polyimide binders and device for implementing this method - Google Patents

Abstract

FIELD: chemical industry.

SUBSTANCE: invention relates to the technology for the manufacture of prepregs - semi-finished products, which are woven filler impregnated with a binder. A device for impregnating layered workpieces based on woven fillers and epoxy, organosilicon and polyimide binders is proposed, containing a heating cabinet in which a frame for infusion impregnation is installed; a layered workpiece is preliminarily installed in the frame. The device also has a vacuum pump, a vacuum trap, a binder preparation unit, which includes a reactor with a stirrer, a temperature sensor, a binder level sensor, and a frequency drive. The binder preparation unit also has a unit for adjusting and controlling the temperature of the reactor and compressor with an indicator of the number of revolutions and direction of rotation of the mixer, and a binder level indicator. The vacuum trap is equipped with a vacuum gauge and a viewing window. The oven is additionally equipped with a sight glass. The frame for infusion impregnation is equipped with receiving pads and a vacuum tube on both sides of the frame. The frame for infusion impregnation is equipped with a vacuum film and has a sealing line with a vacuum film, a line for sealing the impregnation zone along the perimeter of the frame using paranite clamping frames, as well as layers of drainage mesh. Also proposed is a method of impregnation of layered workpieces based on woven fillers and epoxy, organosilicon and polyimide binders using the specified device.

EFFECT: creation of a device for impregnation of layered workpieces based on woven fillers and epoxy, organosilicon and polyimide binders, which allows impregnation with high-viscosity melts and highly concentrated solutions with subsequent removal of solvent residues and low-molecular-weight products, as well as imidization of polyimide binders with the removal of low-molecular-weight products of the applied polymer and obtaining a prepreg while maintaining its shape.

9 cl, 9 dwg

Description

The invention relates to the chemical industry and technology for the manufacture of prepregs - semi-finished products, which are a woven filler impregnated with a binder, namely: epoxy, organosilicon or polyimide binders in a certain weight ratio, and can be used in many industries for further production by pressing hermetically sealed structures from reinforced composite materials that retain their integrity when heated on one side.

Prior art

Known impregnation and varnishing of fillers (GB Shalun, "Production of products from laminated plastics", "CHEMISTRY", Leningrad branch, 1975, from 30-49).

The binder is applied to the filler by impregnation or varnishing. When impregnating, they strive for a deeper penetration of the binder into the filler. In one method, the filler is immersed in a binder solution containing water or an organic solvent, followed by removal of the water or solvent in drying chambers. Another method is to impregnate the filler with liquid or molten binders.

Impregnation of fillers with binders solutions. The fillers are impregnated with binders solutions in special continuous installations, which carry out impregnation and drying. A roll material is used as a filler, which is fed into a bath with an impregnating solution from an unwinding device. The device also contains a guide roller and squeezing rollers, a drying chamber, a winding device, a device for cutting and placing the cut fabric. The degree of penetration of the impregnating solution into the pores of the filler and the amount of the binder applied to the filler depend on a number of factors, the main of which is the viscosity of the impregnating solution, the type and property of the filler (paper absorbency, the density of the weaving of the fabric, the duration of the filler's residence in the impregnating solution, the design of the impregnating device. dilute and less viscous solutions will more easily penetrate into the pores of the filler, however, the use of too dilute solutions leads to a low content of binder in the filler, and also requires an increased energy consumption for evaporation of the solvent during drying.When impregnating, it is necessary to ensure the most complete displacement of air from the filler and its replacement The presence of air inclusions prevents the high-quality impregnation of the filler with a binder.During drying in drying chambers, the solvent is removed and the condensation of the resin deepens - deeper curing of the resin, because during the curing of the resin volatile substances are released, it is necessary to achieve maximum removal of these volatile substances, because being further pressed into the product, they impair the physicochemical, dielectric and decorative properties of the product.

When cutting with special squeezing knives, the impregnated fabric is pressed against the blade of the knife by the force of tension, which removes the excess applied resin from the filler surface.

The disadvantage of the device and method is that it is impossible with this technology to completely impregnate the woven filler without air inclusions, i.e. it will only be possible to varnish the surface layers. Moreover, it is impossible to carry out further removal of the products of polycondensation and imidization.

Known patent for invention of the Russian Federation No. 2243093 "A method of making a prepreg and a device for its implementation."

The method includes winding the filler onto a mandrel into bobbins, evacuating and filling with a binder. The filler is wound onto the mandrel with a volume of free space equal to the required binder content and not less than 0.2 of the total volume of the formed bobbin. Vacuuming is carried out in the chamber for at least 4 hours at a residual pressure of not more than 10 mm Hg. Filling the interfiber and interstitial space of the bobbins with a binder is performed by placing the bobbins with a filler under the same vacuum conditions into the binder. Upon reaching the volume of the binder above the bobbin more than the volume of the interfiber and interstitial space in the bobbin, the pressure in the chamber is raised to a value not lower than atmospheric and the bobbin is kept in the volume of the binder for at least 4 hours. Then allow the excess binder to drain. The device for implementing the method contains a vacuum chamber with a vacuum pump, a vacuum valve and a pressure gauge, a container with a binder and bobbins with filler. The container with the binder contains a perforated cargo platform with a central rod perpendicular to the plane of the platform and connected with the mechanism for dropping the latter. On the cargo perforated platform, reels with filler are installed, alternating with intermediate perforated removable platforms. Load discs are located between the bobbin mandrels and the central rod. The invention improves the quality of fiber wettability and filler impregnation in prepreg, to reduce interfiber and interfiber porosity before impregnation, which makes it possible to increase the tightness of products made from prepregs.

The disadvantage of this invention is that the device is not suitable for impregnating woven fillers, but only for fibers. In addition, the method does not allow controlling the content of the binder. The impregnation is carried out mechanically.

Known RF patent for invention No. 2484956, where the improvement in the quality of impregnation of multilayer workpieces before evacuation is achieved due to preliminary impregnation by immersing the multilayer workpiece in a binder with a high solvent content of up to 50-60% in phenol-formaldehyde resin. Thus, after complete curing, the resulting heat-shielding material with increased heat-resistant properties. The technical result is the saturation of the multilayer workpiece with resin 40-50% by weight, with the content of volatile fractions 3-13% by weight, ensuring the mechanical strength and temperature stability of the monolithic polymer composite material, operating under extreme thermal and mechanical loads. A material with such a quantity of volatile products cannot be hermetically sealed, and the equipment used does not provide impregnation in one go, requires multiple impregnations, and each impregnation takes 14-15.5 hours in time.

The closest to the claimed solution is the RF patent for invention No. 2565709 "Method for making prepreg with automatic control of the technological process" in which a layered workpiece made of multilayer fabric is impregnated with bakelite varnish. The device includes a heated sealed chamber with an impregnating cassette located in it with a blank package, with a tank for bakelite varnish, a vacuum pump, a condenser and a condensate collection tank with adjustable valves and data collection and control units for automating multiple impregnation of the blank.

The disadvantage of this prepreg preparation method is a large number of impregnations to obtain the required amount of binder in the prepreg, which is due to the low content of the basic substance in the bakelite varnish and the periodic washing out of the binder already applied to the filler with a new portion of impregnation. At the same time, many indicators are monitored (the mass of the initial and impregnated workpiece, the weight of the varnish, the drying temperature and the vacuum level), but the change in the viscosity of the binder during the impregnation process and after the drying of the impregnated material is not measured.

According to patents for inventions of the Russian Federation No. 2565709 and RF No. 2484956, they do not provide for the use of frames for infusion impregnation, as a result, the layered blank is in the impregnated cassette of the sealed chamber without sealing the impregnation zone due to the use of a vacuum film, pressure plates and paranite, sacrificial tissue, film with microperforation and a layer of drainage fabric, which results in the appearance of a foamed binder on the surface of the preform.

Disclosure of invention

The technical objective of this invention is to create a device for impregnating layered workpieces based on woven fillers and epoxy, organosilicon and polyimide binders, which allows impregnation with high-viscosity melts and highly concentrated solutions with subsequent removal of solvent residues and low-molecular-weight products, as well as imidization of low-molecular-weight polyimide binders with removal with preservation of the applied polymer and preparation of prepreg with preservation of its shape.

The technical problem posed is solved due to the fact that a device for impregnating layered workpieces based on woven fillers and epoxy, organosilicon and polyimide binders, containing a heating cabinet, in which a frame for infusion impregnation is installed. a laminated blank is pre-installed in the frame. The device also has a vacuum pump, a vacuum trap, a binder preparation unit, which includes a reactor, with a stirrer, a temperature sensor, with a binder level sensor and provided with a frequency drive. The binder preparation unit also has a unit for adjusting and monitoring the temperature of the reactor and compressor with an indicator of the number of revolutions and the direction of rotation of the mixer, and a binder level indicator. The vacuum trap is equipped with a vacuum gauge and a viewing window. The oven is additionally equipped with a sight glass. The frame for infusion impregnation is equipped with receiving pads and a vacuum tube on both sides of the frame. The frame for infusion impregnation is equipped with a vacuum film and has a sealing line with a vacuum film, a line for sealing the impregnation zone along the perimeter of the frame using paranite clamping frames, as well as layers of drainage mesh. The method of impregnation of layered workpieces based on woven fillers and epoxy, organosilicon and polyimide binders, which consists in the fact that the required amount of woven material is layered into the frame for impregnation, then the frame with the layered workpiece inside is placed in a heating cabinet. Next, it is evacuated at a vacuum of -0.96 bar and a temperature of 80-90 ° C, for 10-30 minutes, to remove moisture and air, followed by vacuum impregnation, which is carried out in one stage for solution binders at room temperature, and for melt binders at 60-70 ° C with removal of solvent and low molecular weight products. In this case, the value of the vacuum should not exceed -0.4 bar, which ensures a uniform distribution of the binder in the layered workpiece and a subsequent stepwise increase in temperature from 80-210 ° C for organosilicon binders, and from 20-165 ° C for polyimide binders with a vacuum of -0.6 to -0.8 bar to ensure the removal of the products of polycondensation and imidization reactions. Distillation of the solvent and low-molecular-weight polycondensation and imidization products is observed visually in drainage pads and collected in a vacuum trap. After the end of the distillation, the process stops and the layered workpiece is cooled to 25-30 ° C temperature.

Brief description of figures

Fig. 1. A diagram of a device for impregnating layered workpieces based on woven fillers and epoxy, organosilicon and polyimide binders is presented.

Fig. 2. Introduced infusion impregnation frame,

Figure 3 (A, B, C). A diagram of the assembly of a package of laminated material for packing in a frame is presented.

FIG. 4. An assembly diagram for the vacuum impregnation stage is presented.

Figure 5 (A, B, C). An assembly diagram for the solvent removal and imidization stage is presented.

Fig. 6. Temperature-time regime for the manufacture of prepregs from a polyimide binder. (Pris 2)

Fig. 7. Temperature-time regime for preparing prepregs from mortar epoxy binders. (T-71)

FIG. 8. Temperature-time regime for the manufacture of prepregs from melt epoxy binders. (EDT-10)

FIG. 9. Temperature-time regime for the preparation of prepregs from organosilicon binders. (k-9-70)

Implementation of the invention

Device 1 is a heating cabinet 2, in which a frame for infusion impregnation 3 is installed. A laminated blank is pre-installed in the frame, 4 on which a penny or penny 21 is located, depending on the type of binder. The device 1 also has a vacuum pump 5, a vacuum trap 6, a binder preparation unit 7, a reactor 9, with a stirrer 12, a temperature sensor 10, with a binder level sensor 11 and provided with a frequency drive 8. The binder preparation unit 7 also has an adjustment and control unit 15 (temperature of the reactor and pump with an indicator of the number of revolutions and direction of rotation of the stirrer, indicator of the level of the binder). Vacuum trap 6 is equipped with a vacuum gauge with a tap 18 and a viewing window 19. The oven 2 is provided with an inspection window for the oven 20. The frame for infusion impregnation 3 is equipped with a built-in vacuum line (internal 22 and external 23) also along the perimeter of the frame 3 using clamping frames 27 and paranitic gaskets. The binder preparation unit 7 also contains a compressor 13, a pressure gauge 14, a W1-30 valve, and a W2-31 valve.

The impregnation of the layered workpiece 4 is carried out as follows.

Technological equipment is prepared for assembling a layered workpiece, for this:

- clean the surface of the frame for infusion impregnation, if necessary, treat it with an emery disk with a grain size not larger than P400;

- collect a layered blank from a given number of layers of glass fabric, for example, T-10-14 or silica fabric KT-11 TO, with orientation along the base of the woven filler with a width of 200 to 400 mm and a length of 250 to 450 mm;

- cut out two sheets of drainage mesh

- a layered workpiece is placed between two layers of a drainage mesh and a vacuum film, the latter of which is sealed around the perimeter using silicone sealant;

- install a penny of binder supply to the surface of the drainage mesh;

- assemble the bag for impregnation according to FIG. 3 or FIG. 5 depending on the number of layers and the type of binder;

- external lines in figures 3 and 5, made of silicone tubes, can be used for impregnation and for removal of solvent, low molecular weight polycondensation and imidization products;

- connect the vacuum trap 6 to the vacuum pump 5;

- install the assembled frame 3 in the oven 2;

- connect an internal vacuum line with a vacuum gauge valve 18;

- the external line 23 is connected to the tap W1 30

- by vacuum gauge 18, the vacuum level in the impregnation zone is recorded - not less than -0.98bar.

- the tooling is heated to 80 ... 90 ° C and the layered workpiece is vacuum dried for 30-40 minutes;

- prepare a binder solution - epoxy, or organosilicon, or polyimide binders in a heated reactor 9;

- open the valve W1 30; the impregnation is controlled by the appearance of the binder in the area of the penny 21 of the binder supply;

- then reduce the vacuum to -0.1 bar so that the fabric fully "breathes" (by first increasing the thickness and then decreasing the thickness of the layered workpiece), adjusting the valve on the vacuum trap, repeat this procedure until the fabric is completely saturated ;

- after the end of the impregnation, first shut off the valve W2 31, then the valve W1 30;

- raise the temperature of the tooling to T1 at a rate of 2 ° C per minute;

- maintain the temperature area for the required time, depending on the type of binder (see Fig. 6, 7, 8);

- raise / or lower the temperature of the tooling to T2, depending on the type of binder (see Fig. 6, 7, 8, 9);

- For a polyimide binder, the imidization process is carried out for 1.5-2.0 hours. The vacuum level in the bag from the layered workpiece must be at least -0.98bar during the entire process, control is carried out using a vacuum gauge 14 on a trap;

- after that, the package of the laminated blank 3 is cooled to room temperature and the vacuum is released;

- after the end of the technological process, the layered workpiece 3 is removed in the reverse order.

The degree of removal of the solvent and low-molecular substances depends on the magnitude of the vacuum, the temperature, the distillation is observed visually both on the surface of the layered workpiece and in the external vacuum lines in front of the vacuum trap 6. After the completion of the distillation of the solvent, the process is stopped.

All parameters of technological processes depend on the type of binder and are presented in Fig. 6, 7, 8, 9.

To obtain the final product, for example, monolithic CFRP EUP-201U, the processed laminated material (prepreg) is placed in the press plates and the final pressing is performed at a given pressure and temperature, depending on the type of binder.

The number of prepreg layers in a stack of a layered workpiece is determined from the following ratio obtained empirically - five UT-900 fabric workpieces are required per 1 mm of finished CFRP sheet thickness.

The main advantage of the proposed solution is the possibility of using it for both epoxy and polyimide and organosilicon binders, as well as impregnation of high-viscosity melts and highly concentrated solutions, followed by removal of solvent residues and low-molecular products, and imidization of polyimide binders without loss of the applied polymer and the absence of warping of the layered workpiece.

The claimed device operates as follows.

In the frame for impregnation, the required amount of woven material is laid - a layered workpiece 4. Next, the frame 3 shown in figure 2 with a layered workpiece 4 inside is placed in a heating cabinet 2, where it is evacuated at a certain temperature. The impregnation process begins with the supply of the binder to the penny, at a vacuum of -0.98bar, then the supply of the binder is stopped and the vacuum is reduced to -0.1bar in order to decompact the layers of the fabric and uniform distribution of the binder. Such an operation, depending on the thickness of the workpiece 4, is carried out at the rate of one cycle per 1mm of the product (the length of the cycle is 1.5-2.0 minutes). After uniform distribution of the binder inside the layered preform 4, that is, the end of the impregnation, which is determined visually, the binder is blocked and the external vacuum line 23 shown in figure 5 is connected and the temperature is increased. The vacuum is dosed with a value of -0.2 to -0.4 bar, the degree of removal of the solvent and low-molecular substances depends on the temperature, while the distillation is observed visually both on the surface of the layered material and in the external vacuum lines 23 in front of the vacuum trap 6. After the completion of the distillation process stop.

All the above descriptions of the functioning of the device confirm the fulfillment of the technical problem of this invention, namely, the creation of a device for impregnating layered workpieces based on woven fillers and epoxy, organosilicon and polyimide binders, which allows impregnation with high-viscosity melts and highly concentrated solutions with subsequent removal of solvent residues and low-molecular-weight products, and also carry out the imidization of polyimide binders with the removal of low-molecular-weight products while preserving the applied polymer and obtaining a prepreg product with the preservation of its shape and no warpage.

Industrial applicability

All of the above indicates the industrial applicability of the method for impregnating layered workpieces based on woven fillers and epoxy, organosilicon and polyimide binders and a device for implementing this method

List of positions.

1.device

2.heater cabinet

3.frame for impregnation

4.Laminated workpiece

5.vacuum pump

6.vacuum trap

7.vacuum binder preparation unit,

8.pump with frequency drive

9.reactor

10.temperature sensor

11.binder level sensor

12.stirrer

13.compressor

14. pressure gauge

15.Reactor and compressor temperature control unit

16.indicator of speed and direction of rotation of the mixer

17.binder level indicator

18.vacuum gauge

19. observation window

20. sight glass of the oven,

21. foster penny

22.internal vacuum line

23. external vacuum line

24.vacuum film

25. sealing line

26. impregnation zone

27. clamping frames made of paranite

28.Drainage mesh layers

29.working area

30.wentel W1

31.wentel W2

Claims (5)

1. A device for impregnating layered workpieces based on woven fillers and epoxy, organosilicon and polyimide binders, containing a heating cabinet with an impregnation frame installed in it, while the frame is made with the possibility of pre-loading layered workpieces into it, a vacuum pump, a vacuum trap, which is different in that the frame is configured to perform infusion impregnation, while the device additionally has a vacuum binder preparation unit, which consists of a frequency-driven pump, a reactor with a temperature sensor and a binder level sensor, a stirrer, a compressor, a pressure gauge and a reactor temperature control unit, and compressor, while the control unit is additionally equipped with an indicator of the speed and direction of rotation of the stirrer, as well as a binder level indicator, and the vacuum trap is equipped with a vacuum gauge and a viewing window, while the oven is additionally equipped with a viewing glass, and the frame for infusion ion impregnation is equipped with receiving pads, an internal vacuum line, an external vacuum line, a vacuum film, and the line for sealing the impregnation zone has clamping frames made of paranite and layers of drainage mesh. 2. A method of impregnating layered workpieces based on woven fillers and epoxy, organosilicon and polyimide binders, which consists in pre-laying the layered workpieces, placing the device according to claim 1 in the oven, impregnation and subsequent elimination of the solvent, characterized in that the technological equipment for assembly is preliminarily prepared a layered workpiece, namely, the surface of the frame is cleaned for infusion impregnation, then a packet of a layered workpiece is assembled, orienting with a shared thread along the long side of the frame, after which the packet is cut to the required size, then the resulting packet of a layered workpiece is placed on the working area of the frame, then the packet for vacuum impregnation according to the scheme, depending on the number of layers and the type of binder, after that one of the prepared drainage mesh cloths is placed on the surface of the layered workpiece, and the second prepared drainage mesh cloth is placed under the laminated workpiece, then a penny for binder supply is installed it is placed on the surface of the mesh, after which a vacuum film is installed and rolled along the perimeter of the sealing, followed by cutting off the allowance, after which, along the perimeter of the vacuum film, it is covered with a paranite frame and placed in an oven with subsequent heating, while before heating, the internal vacuum lines are connected to the vacuum trap, after this, the layered workpiece is evacuated at a vacuum of -0.96 bar and a temperature of 80-90 ° C for 10-30 minutes, then a binder for vacuum impregnation is fed from the binder preparation unit to the zone of the layered workpiece through external vacuum lines, after which the binder preparation unit is turned off and the solvent is removed, then the layered workpiece is cooled to 25-30 ° C inside the oven without oxygen access. 3. A method of impregnating layered workpieces based on woven fillers and polyimide binders according to claim 2, characterized in that imidization is performed using external and internal vacuum lines before the solvent removal step. 4. The method of impregnating layered workpieces based on woven fillers and epoxy, organosilicon and polyimide binders according to claim 2, characterized in that for organosilicon binders the vacuum value during vacuum impregnation should not exceed -0.4 bar, which ensures uniform distribution of the binder in layered workpiece and a subsequent stepwise increase in temperature from 80-210 ° C with simultaneous removal of low molecular weight products. 5. The method of impregnating layered workpieces based on woven fillers and epoxy, organosilicon and polyimide binders according to claim 2, characterized in that for polyimide binders, the vacuum value during vacuum impregnation should not exceed from -0.6 to -0.8 bar, and the subsequent stepwise increase in temperature from 20-165 ° C ensures the removal of the products of the polycondensation and imidization reaction.

Images