RU2565709C1 - Production of prepreg with process acs - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: proposed method comprises the steps that follow. Weight M_nib of non-impregnated blank is measured to place the latte in sealed chamber. Sealed chamber with said blank is evacuated to determine the quantity of impregnations n_imp and vacuum drying n_dr. Impregnation time is determined for one cycle τ_imp as well as pressure of impregnation in vacuum P_imp. Resin weight M_r in impregnated blank is defined to define the lacquer weight M_l required for blank impregnation and that of lacquer portion M_lp required for every impregnation. Pressure is determined is defined at vacuum P_lb corresponding to lacquer boiling point. Weight of solvent M_bim removed at every drying is defined. This process comprises multiple blank vacuum impregnation and drying and removal of finished prepreg from sealed chamber.

EFFECT: lower costs of materials, lower labour input.

1 dwg

Description

The invention relates to a method for producing a prepreg used in the manufacture of multilayer polymer composite materials for aerospace, automotive, shipbuilding and other fields of technology, which require heat-protective materials with high heat-resistant properties.

Prepregs are semi-finished composite materials, which are obtained by impregnating a reinforcing fibrous base with uniformly distributed polymer binders.

A known method of manufacturing a prepreg (RU 2484956 C1, IPC: B29B 15/10 (2006.01), B29B 15/12 (2006.01), C08J 5/24 (2006.01), publ. 06/20/2013), adopted for the prototype, including the measurement mass M _{sign of the} workpiece, placing the workpiece in an airtight chamber, evacuating the airtight chamber with the workpiece placed in it, determining the number of vacuum impregnations n _pr and vacuum dryers n _s , determining the impregnation time per cycle τ _pr , determining the pressure during impregnation under vacuum R _pr , determination of mass M _with the resin impregnated into the preform, mass determination varnish M _l desired d I impregnation of the preform and the weight portions varnish M _nn required for each impregnation, the determination of pressure during drying in vacuo P _cells corresponding to the temperature varnish boiling determination of the mass being removed at each drying solvent M _nsp, reusable vacuum impregnation and drying the preform, extracting the finished prepreg from a sealed chamber. The flow of bakelite varnish in the process of vacuum impregnation of the workpiece is controlled by the operator according to the testimony of the piezometer. The control of the solvent content in the impregnated preform during the vacuum drying process is also carried out visually by the amount of solvent condensate in the collector with a piezometer.

This method does not provide operational control of technological parameters at all stages of preparing a prepreg due to manual control of the technological process of obtaining a prepreg, errors in determining the polymer content in the preform during the impregnation, and the volume of solvent condensate removed from the preform formed during vacuum drying. Another disadvantage is the increased consumption of bakelite varnish, the need for additional operations associated with dosing varnish poured into the lacquer supply tank and cleaning its internal surfaces after each impregnation.

The objective of the invention is the ability to obtain a multilayer prepreg with predetermined parameters of the polymer, solvent and achieve uniformity of impregnation throughout the volume of the prepreg.

The technical result is to reduce the cost of materials, reduce the complexity of the process, automate the control of the technological process of obtaining a multilayer prepreg, improve the quality of the prepreg due to the high accuracy of determining the polymer and solvent content in the workpiece at all stages of manufacturing.

The specified technical result is achieved by the fact that in the proposed method, which includes measuring the weight of the non-impregnated preform M _sign , placing the preform in a sealed chamber, evacuating the sealed chamber with the preform placed in it, determining the number of vacuum impregnations n _pr and vacuum dryers n _s , determining the impregnation time for one cycle τ, _etc., determine the pressure in the impregnation under vacuum, P, _etc., determination of the mass M _{from the} resin in the impregnated preform definition varnish mass M _n required for impregnation of the preform, and the weight portions lacquer M _nn required for each impregnation, the determination of pressure during drying in vacuo P _cells corresponding to the temperature varnish boiling determination of the mass being removed at each drying solvent M _nsp, reusable vacuum impregnation and drying the preform, extracting the finished prepreg of the sealed chamber, wherein the workpiece placed in a cassette, which is installed on the force sensor, measure the mass of the workpiece, measure the temperature t in the sealed chamber and the temperature readings are compared with the set temperature in the sealed chamber t _to , ec if the temperature is less than the set value, then a command is made to turn on the heater, and when the set temperature t is _reached , the first impregnation cycle is carried out in the sealed chamber, the current pressure P in the sealed chamber is measured and compared with the preset pressure value when impregnated under vacuum R _pr , if P> P, _etc., the formed command to close the atmospheric pressure tap and the opening of the vacuum tap, if during the next measurement the current pressure value P <P, _etc., the formed command for closing and opening the vacuum tap al osfernogo crane control of temperature and pressure in the sealed chamber is maintained for the entire production of the prepreg manufacturing process with a predetermined period of time Δτ ₁ during impregnation measured preform mass and generates a command for opening of the feeding nail of the crane to its feeding into a sealed chamber, and when the mass blanks M _np values:

$$M_{nP}=M_{sn}+M_{lP},\left(\mathrm{one}\right)$$

where M _np - the mass of the impregnated workpiece, kg;

M _{sign the} mass of the impregnated workpiece, kg;

M _LP - the mass of a portion of varnish required for each impregnation, kg;

form a command to close the lacquer supply tap to stop its supply to the sealed chamber, then determine the increase in the mass of varnish ΔM _np in the workpiece after a predetermined period of time Δτ of measuring the gain in weight of the workpiece upon impregnation:

$$\Delta M_{nP}=M_{te\mathrm{to}}-M_{PRed},\left(2\right)$$

where ΔM _np is the increase in the mass of varnish in the workpiece after a predetermined period of time Δτ is the measurement of the gain in mass of the workpiece upon impregnation, kg;

M _tech - the current mass of the workpiece, kg;

M _prev - weight of the workpiece at the previous measurement, kg;

then determine the change in the mass of the workpiece ΔM _1const for a given period of time Δτ measuring the gain in mass of the workpiece during impregnation from the equation:

$$\Delta M_{\mathrm{one}Pconst}=M_{lP}\times \Delta \tau /{\tau }_{PR},\left(3\right)$$

where ΔМ _1пconst is the change in the mass of the workpiece for a given period of time Δτ measuring the increase in mass of the workpiece during impregnation, kg;

Δτ is the specified period of time for measuring the gain in mass of the workpiece during impregnation, hour;

τ _CR - the specified time of impregnation of the workpiece for one impregnation cycle, hour;

and compare the current value ΔM _np with ΔM _1pconst , if ΔM _np > ΔM _1pconst , then form a command to open the lacquer supply tap to feed it into the sealed chamber, if ΔM _np <ΔM _1pconst , then form a command to close the varnish supply tap to stop it feeding into the sealed chamber, the first vacuum drying cycle is carried out, the current pressure P in the sealed chamber is measured and compared with a predetermined pressure value when drying under vacuum _Pcl , corresponding to the boiling temperature of the varnish, if P> _Pcl , then form a command to close the atmospheric tap pressure and opening the vacuum valve, the pressure measurement in the sealed chamber is repeated after a predetermined period of time Δτ ₁ , if during the next measurement the current pressure value is P <P _cells , then a command is formed to close the vacuum valve and open the atmospheric valve, during the current vacuum drying, measure the mass the workpiece M _np , and the pressure P = P _CL support until the mass of the workpiece during drying M _nс reaches a value:

$$M_{n\mathrm{from}}=M_{nP}-M_{n\mathrm{from}P},\left(\mathrm{four}\right)$$

where M _ns is the mass of the workpiece during drying, kg;

M _np - the mass of the impregnated workpiece, kg;

M _nsp is the mass of the solvent removed during each drying, kg;

after the completion of the first technological cycle of vacuum impregnation and vacuum drying, the process is repeated (n-1) times.

The invention is illustrated in the drawing, which shows a schematic diagram of an installation for the manufacture of a prepreg with automatic control of the process.

The method is as follows.

They impregnate a multilayer preform 1 from a web of the required brand, for example, PVP KT-11 or PVP-KTK. To do this, in an airtight chamber 2, an impregnation cassette 4 is installed on the force sensor 3 without a blank 1. The force sensor 3 measures the mass of the impregnation cartridge 4, and the signal from the force sensor 3 is fed to the information collection unit 5, and then to the control unit 6. Control unit 6 zeroes the readings of the force sensor 3 and takes the weight of the impregnating cartridge 4 equal to zero. Then, the blank 1 is placed in the impregnation cassette 4 and the hermetic chamber 2 is closed. The force sensor 3 measures the mass of the workpiece 1 M _sign , and the signal from the force sensor 3 is transmitted to the information collection unit 5, and then to the control unit 6.

The following data is entered into the control unit 6:

- mass fraction of resin in the prepreg g _s ,% (OST 92-0903-78);

- mass fraction of resin in bakelite varnish, for example LBS-4, m _s ,%, mass fraction of water in bakelite varnish m _in ,%, mass fraction of solvent removed during drying, for example ethanol, g _su ,% (GOST 901-78 “Varnishes Bakelite ");

- the optimum temperature in the sealed chamber t _to , ° C;

- the time period Δτ (hour) is the frequency of measuring the mass gain of the workpiece 1 during impregnation;

- the time period Δτ ₁ (hour) is the frequency of measuring temperature t (° C) and pressure P (MPa) in a sealed chamber.

It is also determined based on the technological process and introduced into the control unit 6:

- impregnation time for one impregnation cycle τ _pr , hour;

- the value of the pressure when impregnated under vacuum R _CR , MPa;

- pressure value during drying under vacuum R _c (MPa), corresponding to the boiling temperature of bakelite varnish, i.e. saturated vapor pressure of a solvent, for example ethanol (Vargaftik NB, “Handbook of the thermophysical properties of gases and liquids”, M .: Nauka, 1972, p. 407);

- the number of technological cycles n (one technological cycle consists of one vacuum impregnation and one vacuum drying);

- the number of vacuum impregnations n _CR;

- the number of vacuum driers _with n.

The control unit 6 determines:

- the resin content M _s (kg) in the impregnated preform 1 based on the equation: M _s / (M _s + M _char ) × 100 = g _s , whence M _s = M _char × g _c / (100-g _s ),

where M _zn - the mass of the impregnated workpiece, kg;

- mass M _l (kg) of bakelite varnish (for example, LBS-4), which is required for the impregnation of the workpiece: M _l = M _s × 100 / m _s ,

- the mass of a portion of varnish M _lp (kg) required for each impregnation of the workpiece, according to the formula: M _lp = M _l / n _CR ,

- portion mass M _nsp (kg) removed during each drying of the solvent (for example, ethanol), according to the formula:

_Nsp M = M × g _{CY nn} × (100-m _{in a} -m) / 100.

After determining the parameters, the temperature t (° C) in the sealed chamber 2 is measured and the temperature readings from the temperature sensor 7 in the sealed chamber 2 are compared with the set temperature t _to , i.e. control the process. If the temperature reading I is less than the set t _k , then a command is generated on the information collection unit 5 from the sensor 7 to the control unit 6 through the temperature control relay 9 to turn on the heater 8. Heating is performed, and when the set temperature t _{k is reached} in the sealed chamber 2, the first impregnation cycle. Why measure the pressure P (MPa) in the sealed chamber 2 according to the testimony of the pressure sensor 10 and compare it with a predetermined pressure value when impregnated under vacuum P _pr (MPa), thereby controlling the pressure in the sealed chamber. If P> P _CR , then form a command on the information collection unit 5 from the pressure sensor 10 to the control unit 6 through the control unit of the electromagnetic valve 11 to close the atmospheric pressure valve (KP1) 12 and open the vacuum valve (KP2) 13, while reducing pressure P in a sealed chamber to a predetermined pressure value when impregnated under vacuum P _ol through a gas ballast tank 14.

If during the next measurement the current pressure value is P <P _CR , then a command is generated on the information collection unit 5 from the pressure sensor 10 to the control unit 6 through the control unit of the electromagnetic valve 11 to open the atmospheric pressure valve (KP1) 12 and close the vacuum valve (KP2) 13, wherein there is an increase in pressure P in the sealed chamber to a predetermined P _ol through a gas ballast tank 14.

The temperature and pressure in the sealed chamber are controlled during the entire technological process of manufacturing the prepreg with a predetermined period of time Δτ ₁ , maintaining the temperature t equal to the given t _to and the pressure P equal to the given P _pr

In the process of impregnation, a command is generated on the information collection unit 5 from the force sensor 3 to the control unit 6 through the control unit for the servo drive 15 of the servo drive 16 to open the varnish supply valve (KRZ) 17 to supply the first portion of bakelite varnish, for example, LBS-4, from a container with varnish 18, and when the mass of the workpiece 1 is reached, the value of M _np obtained from formula (1), form a command on the information collection unit 5 from the force sensor 3 to the control unit 6 through the control unit of the servo drive 15 of the servo drive 16 to close the varnish supply valve (KRZ) 17 to cease and bakelite lacquer in the hermetic chamber 2.

Monitoring the duration of the impregnation is as follows. Determine the increase in the mass of varnish ΔM _np in the workpiece 1 after a predetermined period of time Δτ by the formula (2). Then determine the change in the mass of the workpiece ΔM _1const for a period of time Δτ from equation (3) and compare the current value ΔM _np with ΔM _1const . If ΔM _np > ΔM _1pconst , then a command is generated on the information collection unit 5 from the force sensor 3 to the control unit 6 through the control unit of the servo drive 15 of the servo drive 16 to open the varnish supply valve (KRZ) 17 for supplying varnish. If ΔМ _nп <ΔМ _1пconst , then a command is generated on the information collection unit 5 from the force sensor 3 to the control unit 6 through the control unit for the servo drive 15 of the servo drive 16 to close the varnish supply valve (KRZ) 17 to stop the varnish supply to the sealed chamber 2.

Then produce the first cycle of vacuum drying. Measure the pressure P (MPa) in the sealed chamber 2 according to the testimony of the pressure sensor 10 and compare it with a predetermined pressure value when dried under vacuum _Rcl , corresponding to the boiling temperature of the bakelite varnish, thereby controlling the pressure in the sealed chamber. If P> P _kl , then a command is formed on the information collection unit 5 from the pressure sensor 10 to the control unit 6 through the control unit of the electromagnetic valve 11 to close the atmospheric pressure valve (KP1) 12 and open the vacuum valve (KP2) 13, while through the gas ballast capacity 14 is a decrease in pressure P in the sealed chamber 2 to a pressure value of R _CL . The pressure measurement P in the sealed chamber 2 is repeated after a predetermined period of time Δτ ₁ .

If during the next measurement the current pressure value is P <P _cells , then a command is generated on the information collection unit 5 from the pressure sensor 10 to the control unit 6 through the control unit of the electromagnetic valve 11 to close the vacuum valve (КР2) 13 and open the atmospheric pressure valve (КР1) 12. This increases the pressure P in the sealed chamber 2 to a predetermined pressure P _CL through the gas ballast container 14. In the process of vacuum drying, the mass M _{np of the} workpiece 1 is measured, and the pressure P = P _{cl is} maintained until the mass of the workpiece 1 during drying M _ns will not reach the value determined by the formula (4).

The volatile products pumped out during the vacuum drying process pass through the resin separator 19. After passing through the vacuum pump 20, the volatile products enter the condenser 21, where they are condensed and collected in a condensate collecting tank 22.

After completion of the first production cycle, the process is repeated (n-1) times.

During the first technological cycle:

the mass of the workpiece during vacuum impregnation - M _1p = M _zn + M _lp ;

the mass of the workpiece during vacuum drying is M _1c = M _1p -M _1sp .

When conducting the nth technological cycle:

the mass of the workpiece during vacuum impregnation - M _np = M _{(n-1) s} + M _lp ;

the mass of the workpiece during vacuum drying - M _ns = M _np -M _nsp .

Then the sealed chamber 2 is opened and the impregnating cassette 4 with the obtained prepreg is removed from it.

An example implementation of the method

To implement the method, a multilayer billet of knitting-stitched webs of the required thickness is used, which is obtained by stitching silica fabrics KT-11-11 (PVP-KT-11 fabric, 11 addition thick) or silica-kapron - CPC (PVP-CTK fabric up to 16 additions) according to GOST 13863-89. A distinctive feature of the paintings is high porosity and low density. As a polymer binder, LBS-4 bakelite varnish with a dynamic viscosity in the range from 145 to 465 MPa · s using a VPZh-4 viscometer according to GOST 901-78 is used. Impregnation and drying is carried out in three technological cycles.

The following data is entered into the control unit 6:

- mass fraction of resin (polymer) in the impregnated workpiece g _with = 35 ... 45%;

- mass fraction of resin in the LBS-4 bakelite varnish - m _s = 50-60%;

- mass fraction of water in the LBS-4 bakelite varnish - m _in = 0.09%;

- the number of technological cycles n = 3;

- the number of vacuum impregnations n _CR = 3;

- the number of vacuum dryers n _s = 3;

- mass fraction of the solvent (for example, ethanol) removed during each drying, g _su = 45 ... 55%;

- the temperature in the sealed chamber t _to = 25 ... 50 ° C;

- the time of impregnation of the workpiece in one cycle τ _CR = 0.83 ... 1 hour;

- pressure during impregnation under vacuum P _ol = 0.05 MPa;

- pressure during drying under vacuum R _c (MPa), corresponding to the boiling temperature of LBS-4 bakelite varnish (Vargaftik NB, “Handbook of Thermophysical Properties of Gases and Liquids”, M. Nauka, 1972, p. 407);

- the period of time Δτ = 0.00278 ... 0.0056 hours is the frequency of measuring the gain in mass of the workpiece during impregnation;

- the time period Δτ ₁ = 0.00278 ... 0.0056 hours is the frequency of measuring the temperature t ° C and pressure P (MPa) in the sealed chamber.

Then put the workpiece 1 in the impregnation cassette 4, which is placed in a sealed chamber 2. The process of impregnation and drying proceeds in accordance with the above method.

Claims (1)

A method of manufacturing a prepreg with automatic control of the technological process, including measuring the mass of the impregnated preform M _sign , placing the preform in a sealed chamber, evacuating the sealed chamber with a preform placed in it, determining the amount of impregnation n _pr and vacuum dryers n _s , determining the impregnation time per cycle τ _pr , determining the pressure when impregnated under vacuum R _pr , determining the mass of the resin M _s in the impregnated preform and determining the mass of varnish M _l required for the impregnation of the preform, and the portion mass lacquer M _lp required for each impregnation, determining the pressure during drying under vacuum _Pcl , corresponding to the boiling point of the lacquer, determining the mass of solvent _{N nsp} removed during each drying, reusable vacuum impregnation and drying of the workpiece, removing the finished prepreg from the sealed chamber, characterized in that the workpiece is placed in a cassette, which is installed on the force sensor, measure the mass of the workpiece, measure the temperature t in the sealed chamber and the temperature readings are compared with the set temperature in the sealed Amer t _k if the temperature reading is less than the predetermined, then form a command to turn the heater, when it reaches a predetermined temperature t _to a sealed chamber produce first impregnation cycle measured current pressure P in a sealed chamber and comparing it with a predetermined pressure value during impregnation under vacuum P _etc., if P> P, _etc., the formed command to close the atmospheric pressure tap and the opening of the vacuum tap, if during the next measurement the current pressure value P <P, _etc., the formed command to close a vacuum cock and from rytie outside tap control of the temperature and pressure in a sealed chamber produced during the technological process of manufacturing the prepreg with a predetermined period of time Δτ ₁ during impregnation measured preform mass and generates a command for opening of the feeding nail of the crane to its feeding into a sealed chamber, and when the the mass of the workpiece M _np values:
M _np = M _char + M _lp ,
where M _nп - the mass of the impregnated workpiece;
M _LP - the mass of a portion of varnish;
form a command to close the lacquer supply tap, then produce a vacuum drying cycle, determine the increase in lacquer mass ΔM _np in the workpiece after a predetermined period of time Δτ of measuring the gain in weight of the workpiece upon impregnation:
ΔM _np = M _tech- M _before ,
where ΔM _nп is the increase in the mass of varnish in the workpiece after a predetermined period of time Δτ of measuring the increase in the mass of the workpiece upon impregnation;
M _tech - the current mass of the workpiece;
M _pre - the mass of the workpiece in the previous measurement;
then determine the change in the mass of the workpiece ΔM _1const for a given period of time Δτ measuring the gain in mass of the workpiece during impregnation from the equation:
ΔM = M _{1pconst nn} × Δτ / τ _pr
where ΔM _1пconst is the change in the mass of the workpiece for a given period of time Δτ measuring the increase in mass of the workpiece during impregnation;
M _LP - the mass of a portion of varnish;
Δτ is the specified period of time for measuring the gain in mass of the workpiece during impregnation;
τ _CR - the specified time of impregnation of the workpiece in one cycle;
and compare the current value ΔM _nп with ΔM _1пconst , if ΔM _nп > ΔM _1пconst , then form a command to open the varnish supply valve for feeding it into the sealed chamber, if ΔM _nп <ΔM _1пconst , then form a command to close the varnish supply valve to stop it feed into the sealed chamber, measure the current pressure P in the sealed chamber and compare it with a predetermined pressure during drying under vacuum _Pcl , corresponding to the boiling point of the varnish, if the pressure in the sealed chamber P> _Pcl then form a command to close the atmospheric pressure valve and open the vacuum smart valve, the pressure measurement in the sealed chamber is repeated after a predetermined period of time Δτ ₁ , if during the next measurement the current pressure value is P <P _cells , then a team is formed to close the vacuum valve and open the atmospheric pressure valve, during the current vacuum drying measure the mass of the workpiece M _nп and pressure P = Р _cl support until the mass of the workpiece during drying M _nс reaches a value:
M _ns = M _np -M _nsp ,
where M _ns is the mass of the workpiece during drying;
after completion of the first technological cycle of impregnation and drying, the process is repeated (n-1) times.