RU2637230C1 - Method of forming polymeric track membrane with cavity of given curvature and device for its implementation - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of forming a polymeric track membrane with a cavity of a given curvature includes laying a polymer blank onto a die, placing the die in a sealed chamber, evacuating ambient air from the chamber, supplying an inert gas under pressure, heating the chamber. Herewith a polymer preform from polyethylene terephthalate is used, previously irradiated with heavy ions ⁴⁰Ar⁺⁸ and sensitized by ultraviolet radiation. After evacuating the atmospheric air from the chamber, the thermocouple-controlled heating of the chamber with a die and a preform installed therein is carried out up to 120°C, an inert gas is supplied under the pressure of, at least, 0.25 MPa and the temperature and pressure in the chamber are kept constant for 15 minutes. Then, pumping out the inert gas, the chamber is gradually cooled to room temperature, the preform is removed and etched with an aqueous solution of alkali NaOH.

EFFECT: expanding the arsenal of technical means for forming a polymeric track membrane with a cavity of a given curvature.

2 cl, 8 dwg

Description

The invention relates to the field of processing plastics, namely, the molding of plastics by heating using gases, and can be used for the manufacture of polymer track membranes with a cavity of a given curvature, for example, from polyethylene terephthalate, for the implementation of barrier keratoplasty in medicine.

A known method of manufacturing from film materials products with a cylindrical flanging of the type of membranes (SU 582100 A1, IPC 5 B29C 1/00, B29C 17/02, publ. 11/30/1977) by forming a blank on a punch passing through a matrix, including heating the blank with subsequent its chilled. For the manufacture of articles from oriented film material, the preform is formed before it is heated.

The disadvantage of this method is the inability to obtain the desired curvature of the product, since the molding is carried out using a cylindrical matrix in the process of plastic deformation, which leads to the formation of defects on the surface of the product and the thickness difference.

A device is known for molding products from thermoplastic materials (RU 2183159 C2, IPC 7 B29C 51/02, publ. 06/10/2002) containing a matrix with a cavity and a nozzle for venting air, a chamber above it with a movable punch and a nozzle for air inlet, air pressure regulation unit. The air pressure control unit contains a first pneumatic distributor, the input of which is designed to be connected to a source of compressed air, and the output is connected to a fitting for air supply. The drive of the punch is made in the form of a pneumatic cylinder with a supra-piston and sub-piston cavities, an adjusting pneumatic throttle and a second pneumatic distributor are introduced into the air pressure control unit, the input of which is designed to connect to a compressed air source, and the first output is connected to the supra-piston cavity of the pneumatic cylinder, with a fitting for supplying air and the output of the first pneumatic distributor, the exhaust opening of which is connected to the control pneumatic throttle, the second output of the second pneumatic distributor is connected to the sub Piston cavity of the pneumatic cylinder.

The disadvantage of this device is that in pneumatic distribution systems using atmospheric air containing various impurities, including oil particles added to prevent corrosion of the elements, the ingress of these particles on the product during molding leads to its contamination.

A known method of manufacturing hollow products from thin sheets of thermoplastic (RU 2111119 C1, IPC 6 B29C 51/10, B29C 51/06, B29C 51/42, publ. 05/20/1998), which consists in the fact that the upper plate of the molding unit is heated to the installation temperature, clamp the sheet between the plate and the matrix, forcibly press the sheet to the heating plate with air. After contact heating of the sheet, it is negatively molded by compressed air supplied through openings in the upper plate. Then, after cooling, the molded product is removed. The sheet is pressed against the heating plate by excess pressure from the side of the matrix.

The disadvantages of the method are the heating of only one element of the molding unit and the use of contact heating, as a result of which the temperature distribution in the molding zone will be uneven and distortion of the product shape is possible.

A device for pneumatic vacuum molding of hollow products from sheet thermoplastics (SU 1537561 A1, IPC 5 B29C 51/00, publ. 23.01.1990), containing placed on the base of the punch communicated by channels with a compressed air and vacuum system, and installed with the possibility of axial displaceable clamping device equipped with a punch with a sleeve and a cup, the outer diameter of which is equal to the inner diameter of the sleeve.

The disadvantage of this device is that as a result of the action of the punch, plastic deformation of the workpiece material occurs, which can lead to the formation of surface defects and the thickness of the product.

A known method of producing a polymer track membrane with a cavity of a given curvature (US 8506833 B2, publ. 08/13/2013), selected as a prototype, which includes laying a polymer blank on a matrix, installing the matrix in an airtight chamber, pumping out atmospheric air from the chamber, supplying inert gas at a pressure of 5 MPa, heating the chamber to a temperature of 164 ° C, irradiating the workpiece with heavy ions, sensitization with ultraviolet radiation and etching with an aqueous solution of alkali NaOH with a concentration of 5N.

The disadvantages of the method are the need for high pressure (5 MPa); the need for a special installation capable of not only supplying temperature and pressure, but also irradiating the material with ions, followed by sensitization with ultraviolet radiation and alkali etching, the possibility of using only unirradiated material, and the limited radius of curvature of the cavity formed up to 5 mm:

0.2b≤r≤5b,

where b is the wall thickness of the cavity, varying in the range of 0.02-1000 microns.

Closest to the proposed is a device for molding products from thermoplastic materials (including polymers) (RU 2031793 C1, IPC 6 B29C 51/10, publ. 03/27/1995), containing a matrix with a cavity and a nozzle for venting, mounted above it chamber with a punch and a fitting for air supply. The air inlet is equipped with a valve. The linear dimensions of the lower base of the punch and the upper base of the cavity of the matrix are related by ratios.

l = (0.5-0.3) L;

b = (0.5 -0.3) V,

where l is the length of the lower base of the punch;

L is the length of the upper base of the matrix cavity;

b is the width of the lower base of the punch;

B is the width of the upper base of the cavity of the matrix.

This device does not allow to control the heating and cooling of the molding area, as well as the air pressure for the implementation of the molding process.

The invention is aimed at expanding the arsenal of technical equipment for a similar purpose.

A single technical result achieved by the implementation of the claimed group of inventions is the formation of a polymer track membrane with a cavity of a given curvature.

The proposed method of molding a polymer track membrane with a cavity of a given curvature, including laying a polymer blank on a matrix, installing the matrix in an airtight chamber, pumping out atmospheric air from the chamber, supplying inert gas under pressure, heating the chamber, irradiating the workpiece with heavy ions, sensitization with ultraviolet radiation, etching with water alkali solution NaOH, characterized in that they use a polymer preform of polyethylene terephthalate, previously irradiated with heavy ions of ⁴⁰ Ar ⁺⁸ and sensitization caused by ultraviolet radiation. After pumping out atmospheric air from the chamber, a thermocouple-controlled heating of the chamber is carried out with the matrix installed in it and the billet to 120 ° C and an inert gas is supplied at a pressure of at least 0.25 MPa. Maintain constant temperature and pressure in the chamber for 15 minutes. Then, pumping out an inert gas, the chamber is gradually cooled to room temperature. The preform is removed and etched with an aqueous solution of alkali NaOH.

The proposed device for forming a polymer track membrane with a cavity of a given curvature, as in the prototype, contains a matrix with a cavity of a given curvature, a fitting for venting air, equipped with a valve.

According to the invention, a chamber is installed in the tube furnace, in the central opening of which a matrix base is mounted, on which a polymer preform is fixed with a lid and screws, the matrix base being made with a cavity of a given curvature. A thermocouple and a fitting for venting air are installed in the central opening of the chamber lid, to which an air and gas pressure control unit is connected, which is connected to an inert gas cylinder.

Thus, the proposed method and device for its implementation allow the formation of track membranes from polyethylene terephthalate with a thickness of 7 μm with a cavity of a given curvature necessary for implantation in the cornea of the eye.

In FIG. 1 shows a device for forming a polymer track membrane with a cavity of a given curvature in an assembled state and a local section.

In FIG. 2 shows a device for forming a polymer track membrane with a cavity of a given curvature in an assembled state, view A from FIG. one.

In FIG. 3 shows an element of a device for forming a polymer track membrane with a cavity of a given curvature, view B of FIG. 1, after the process of forming the curvature of the polymer preform.

In FIG. 4 shows an element of a device for molding a polymer track membrane with a cavity of a given curvature, sections BB and GG of FIG. 3, after the process of forming the curvature of the polymer preform.

In FIG. 5 shows a surface image of a polymer track membrane obtained by a laser scanning microscope, after the procedure for forming a cavity with a given curvature, the height distribution is shown.

In FIG. 6 shows a cross-sectional profile of a polymer track membrane obtained by a laser scanning microscope and corresponding to section BB shown in FIG. 3.

FIG. 7 shows a cross-sectional profile of a polymer track membrane obtained with a laser scanning microscope and corresponding to the G-D section shown in FIG. 3.

In FIG. Figure 8 shows a cross-sectional image of a polymer track membrane of polyethylene terephthalate made using a scanning electron microscope. At the bottom of the image is a scale scale of 10 microns in length with a division price of 1 micron.

A device for molding a polymer track membrane with a cavity of a given curvature (Fig. 1-4) contains a cylindrical chamber 1, in the central hole of which a matrix base 2 is mounted, on which a polymer blank 5 is fixed using a cover 3 and screws 4. The matrix 2 base is made with cavity of a given curvature. The Central hole in the chamber 1 is closed by a cover 6, which is fixed by bolts 7, washers 8 and nuts 9 (Fig. 2, 3). A fitting 10 and a thermocouple 11 are installed in the central hole of the lid 6. The chamber 1 is installed in a tubular furnace 12. The air and gas pressure control unit 13 (BRDViG) is connected to the fitting 10, which is equipped with a valve. An inert gas cylinder 14 is connected to the air and gas pressure control unit 13.

An air and gas pressure control unit was used - GAS Reaction Controller LP. Tube furnace - SUOL-0.25.1 / 12-I1.

A ⁴⁰ Ar ⁺⁸ ion beam irradiated at the C-100 cyclotron with a maximum energy of 41 MeV and sensitized with ultraviolet radiation on an LE 30 erythema lamp with a wavelength of λ = 310 nm, a polymer preform 5 made of polyethylene terephthalate 3.0 cm in diameter was placed on the base of the matrix 2 and fixed using the cover 3 and screws 4. The base of the matrix 2 had a cavity with the curvature necessary to form the curvature of the film that meets the requirements of the curvature of the cornea of the eye: width in horizontal D ₁ = 10 mm and vertical D ₂ = 11 mm planes, radius in horizontal R ₁ = 5.66 mm and vertical R ₂ = 6.5 mm planes, height h = 3 mm.

The matrix 2 in the assembled state was installed in the chamber 1. The chamber 1 was closed with a cover 6, which was fastened with bolts 7, washers 8 and nuts 9. A fitting 10 and a thermocouple 11 were installed in the central hole of the cover 6. The chamber 1 was placed in the tube furnace 12 in the assembled state. After that, atmospheric air was pumped out through the nozzle 10 using an air and gas pressure control unit 13 (BRDViG) and a pressure of 0.1 Pa was created in chamber 1. Then, using the tube furnace 12, the chamber 1 was linearly heated at a rate of 6 ° C / min to a temperature of 120 ° C. The temperature was controlled by thermocouple 11. Upon reaching a temperature of 120 ° C using an air and gas pressure control unit 13 (BRDViG), inert argon gas was supplied to chamber 1 under pressure from cylinder 14 until a pressure of 0.25 MPa was reached. The gas pressure pressed the polymer preform 5 to the surface of the base of the matrix 2 having a given curvature (Fig. 4). It was held for 15 minutes at a temperature of 120 ° C and a pressure of 0.25 MPa, then gas was evacuated and the chamber 1 was linearly cooled at a rate of 2 ° C / min to room temperature. The cooled chamber 1 was disassembled and the polymer preform 5 with the formed curvature was removed.

The extracted polymer preform 5 with the formed curvature (Fig. 5, 6, 7) was subjected to alkaline etching in an aqueous solution of NaOH with a concentration of 1.5 N at a temperature of 77 ° C. Alkaline etching of the material in the region of the tracks led to the formation of a system of through tracks with a diameter of 0.4 μm (Fig. 8).

The method was tested on 50 irradiated polymer blanks - films of polyethylene terephthalate.

On an Olympus LEXT OLS4100 laser scanning microscope, a three-dimensional surface profile of the track membrane was determined after the formation of a given curvature (Fig. 5, 6, 7).

In order to obtain a high-quality cleavage of the cross-section of the track membrane, the sample was fixed for 24 hours on an erythema lamp with λ = 310 mm. Electron microscopy was performed using a Hitachi TM-3000 electron microscope.

The results of a laboratory study showed that the measured profile of the irradiated film after forming a polymer film of a given curvature corresponds to the required curvature of the cornea of the eye.

Claims (2)

1. A method of forming a polymer track membrane with a cavity of a given curvature, including laying a polymer preform on a matrix, installing the matrix in an airtight chamber, pumping out atmospheric air from the chamber, supplying inert gas under pressure, heating the chamber, characterized in that the polymer preform is made of polyethylene terephthalate, previously irradiated with heavy ions ⁴⁰ Ar ⁺⁸ and sensitized with ultraviolet radiation, after evacuation of atmospheric air from the chamber, a thermocouple controlled by heating the chamber with the matrix installed in it and the workpiece to 120 ° C, supply inert gas under a pressure of at least 0.25 MPa, keep the temperature and pressure in the chamber constant for 15 minutes, then pumping out the inert gas, gradually cool the chamber to room temperature temperature, remove the workpiece and subjected to etching with an aqueous solution of alkali NaOH. 2. A device for forming a polymer track membrane with a cavity of a given curvature, comprising a matrix with a cavity, a nozzle provided with a valve, characterized in that the device comprises a chamber, in the central opening of which a matrix base is mounted, on which a polymer blank is fixed with a lid and screws, the matrix base is made with a cavity of a given curvature, a fitting and a thermocouple are installed in the central hole of the chamber cover, the camera is installed in a tube furnace, a pressure control unit is connected to the fitting air and gas, which is connected to an inert gas cylinder.

Images