Radiation protecting material composition, screen for radiation protection and method of making the same

FIELD OF THE INVENTION

The present invention relates to radiological protection and is intended for the production of a transparent screen that protects, for example, medical personnel from scattered X-rays and includes a digital holographic diffractive optical element projecting a radiological alert in the direction of maximum radiological hazard. Such screens are a mandatory safeguard in X-ray diagnostics, and especially in interventional radiology departments [NCRP Report 147. Structural Shielding Design for Medical X-Ray Imaging Facilities (2004); Cousins ​​C, Miller DL, Bernardi G, et al. ICRP publication 120: Radiological protection in cardiology.Ann ICRP 2013 Feb; 42 (1): 1-125]

State of the art

Known X-ray protection products are usually manufactured using lead-containing materials. Protective radiological devices can be used both when placed or placed on a person at risk of radiation [US5844246, WO2006015695, etc.], including the protection of his visual organs [US6309065, etc.], and as transparent screens of glass or plastic containing lead or lead compounds, or polymeric compositions with, for example, barium sulfate (BaSO) 4 filler [WO2008076469 et al.].

It is known that lead acrylic glass, for example. Premac®, which are used in the manufacture of commercial radiation shields and contain 30% w / w lead, the salts of which are chemically incorporated into the acrylic copolymer resin, has a refractive index of 1.54. Lead acrylic glass has 80-88% optical transparency for visible light, and an equivalent thickness of 0.5 mm corresponds to a 12 mm thick acrylic sheet that can block up to 90% of scattered X-rays. [Mobile X-ray Screen, AMS - 076995, httD: //www.amravradiationDrotection.com or Upper body shield, MavigPT6290 / 6272, httD: //www.wtec.Dt/demo/maviQ/Dorteara2svstems.Ddf1. whose X-ray absorption properties are analyzed by KA Fetterly, DJ Magnuson, GM Tannahill, et al. Effective Use of Radiation Shields to Minimize Operator Dose During Invasive Cardiology Procedures. JACC: Cardiovascular Interventions, 2011.4 (10) p. 133-1139].

Lead and its compounds, as well as substances containing lead and its compounds, are difficult to dispose of and, in long-term contact, cause toxic effects on many human organs, especially the nervous system. Due to its high toxicity, it is proposed to ban or restrict the use of lead and its compounds in medical devices [EC Directive 2011/65 / EU, RoHS II (7)].

Lead-free polymeric compositions capable of inhibiting X-rays are also known.

The above-mentioned invention WO2008076469 describes in detail an optically clear, X-ray suppressing, lead-free polymeric composition containing from 5 to 10% (by weight) of fine-grained barium sulfate BaSO4 and a process for their preparation. The optical transparency of such a composition is determined by the uniform refractive indices (from 1.6 to about 1.66) of organic polymers containing sulfur fragments (copolymers of polysulfones, polyethersulfones and polycarbonates) and annealed barium sulfate. To do this, the barium sulphate is first annealed at different temperatures, when the corresponding temperature is reached by raising it uniformly at a rate of 10 ° C / min. The annealed barium sulphate, cooled naturally to room temperature, is ground. The ground barium sulfate is sieved and the collected particles of 60 and less micrometers of barium sulfate powder are fed to an extruder with molten polysulfone resin. The granules formed from the extruder-mixed (homogenized) composition are fed to an injection-molding machine, where they are melted at 320-355 ° C to form 1, 2 and 3 mm thick sheets of different transparency and maturity, which differentiate Rengen radiation. For example, polymer compositions prepared in this way with 10% (w / w) fine-grained barium sulfate BaSO4 filler have a 3 mm thick sheet that most reduces (up to 25%) the intensity of X-rays incident perpendicular to it, but is completely optically opaque. Meanwhile, the compositions prepared in this way, containing up to 5% (by weight) of annealed fine-grained barium sulphate filler, have a 2 mm thick sheet which is sufficiently optically clear (optical transparency for visible light is about 80%, haze is about 40%), but only reduces the intensity of X-rays that fall on it very little (up to 5%). A major disadvantage of the production of such compositions is that relatively high energy consumption is required for both the annealing of the filler (barium sulfate) and the mixing of the composition in the extruder and its high temperature casting processes.

Completely opaque but quite effective X-ray absorbing lead-free polymer composites are obtained by incorporating metallic tungsten micrometric particles (powder) into a thermoplastic polyamide resin. In the publication

WO0244277 describes a radiation shielding polymer composite and a process for its production, in which from 94 to 97% (by weight) of powdered metallic tungsten or its alloy W6Ni-4Cu is added to polyamide resins (nylon-6, nylon-66 or nylon-12) in an extruder, with an average particle size of about 13 micrometers. In order to make the microparticles of tungsten or its alloy W-6Ni-4Cu powder easier to disperse and better adhere to polyamide resins, the tungsten or its alloy W6Ni-4Cu powder is first treated with Y- (2-aminoethyl) aminopropyltriethoxysilane and heated to 120 ° C. The X-ray absorption efficiency of the square (85x85 mm) plates cast from the obtained composites was found to depend on the thickness of the composite layer and was 28-30% (6 mm thick), 48-49% (12 mm thick) and 62-64 % (when the thickness is 18 mm).

Japanese Patent JPH10153687 (US5908884 (A)) discloses rubber-based compositions for radiation protection. They are obtained by mixing, in an open ball mill, fluorinated rubber dispersions containing from 60 to 95% (w / w) of metallic tungsten microparticles ranging in size from 4 to 100 micrometers and from 5 to 40% (w / w) of tungsten microparticles of less than 4 micrometers . The radiation (γ-ray) absorption coefficient of cast and vulcanized 1 mm thick rubber sheets cast from the above dispersions (compositions) of different compositions varies from 0.7 to 1.2 cm^-1, when the energy of γ-rays is 1.5MeV. In addition, the vulcanized composite of fluorinated rubber and tungsten powder has good thermal and chemical resistance, but is completely optically opaque.

International application WO2010145081 describes an X-ray absorbing lead-free polymer composite material containing 5-10% (w / w) plastic as a binder, 2-30% (w / w) organic complexes of rare earth metals (unsaturated carboxylic acid salts of these metals), 2 -50% (w / w) of inorganic rare earth metal compounds, 2-50% (w / w) of tin or its inorganic compounds (oxide, chloride, sulphide, fluoride), 2-55% (w / w) bismuth or its inorganic compounds (oxide, sulphide), 2-23% (w / w) organic complex of bismuth (unsaturated carboxylic acid salts of bismuth), 2-26% (w / w) tungsten or its inorganic compounds (carbide , halide, tungstate), 0.2-3% (w / w) plasticizer, 0.1-0.3% (w / w) antioxidant, 0.05-0.3% (w / w) sialan as binder, and 0.02 -0.1% (w / w) in-situ initiator of the polymerization reaction. As many as 16 rare earth metal compounds (excluding radioactive promethium and actinoids) are mentioned here. Inorganic compounds of these rare earth metals are used, such as oxides, halides, sulfides, carbonates, hydrides, hydroxides.

International application WO20060906299 discloses X-ray shielding lead-free composites and a process for the production of sheets therefrom by uniformly mixing a powder filler with a shielding properties of 90% by weight into an organic polymer (polyurethane resin with a plasticizer). Fillers of different materials, depending on the size of the material and its powder particles, represent from 40 to 80% by volume of the respective polymeric compositions. Such fillers for X-ray shielding materials in the polymeric compositions described in the patent comprise powders of individual Ce, La, W, Sn, CeO2, La2O3, Pr2O3, Nd2Ū3, Sm2O3, EU2O3 and Gd2Ū3 or mixtures of some of these materials with a particle size varying from 1 up to 20 micrometers. Compositions made from the above materials and polyurethane resin with the addition of 1% (w / w) plasticizer were intensively mixed for 0.5 to 2 hours and 1 mm thick opaque sheets were cast from them. X-ray suppression of 1 mm thick sheets of polymeric compositions with fillers of different materials and different particle sizes corresponds to an equivalent lead layer thickness (mmPb) of 0.25 to 0.85 mm.

The closest to the present invention according to the composition of the radiation shielding composition may be the above-mentioned WO0244277, wherein a lead-free composite of a shielding material is obtained by mixing and dispersing up to 97% by weight of tungsten or its alloy microparticles in a polyamide resin. However, the plates cast from it are not transparent.

Because no known (including the proposed) transparent protective radiological screen completely (100%) blocks X-rays, they often contain radiation warning signs. Due to the inherent properties of X-rays, such a danger is greatest when viewed through a transparent protective screen in a direction parallel to the X-rays from which the said screen must protect. It is obvious that the said security marks block the view of objects behind the security screen by looking at it in directions not parallel to the X-rays.

Thus, all known radiological protection devices are either opaque (insufficiently transparent) or contain toxic substances, and signs warning of a radiological hazard block the view through the protective screen and in those directions of vision in which the radiological hazard is negligible.

On the other hand, there is a known way to display a warning sign only in a certain direction, as described in the invention US5963345. According to the present invention, a warning sign consisting of a concealed lamp attached to a vehicle (e.g. a school bus) and a transmission hologram mounted on the front or rear of the car. The lamp illuminates a transmission hologram, the image of which is visible only at a certain, predetermined viewing angle. The hologram illuminates a certain inscription, such as "Stop", at a predetermined viewing angle to warn drivers of other cars that a car displaying the hologram, such as a school bus, is about to stop. Said hologram is manufactured in such a way that it has an asymmetrical field of view. The invention also describes a method of recording such a hologram. The hologram is recorded in an analogous manner, passing an objective beam through a diffuser and blocking the light transmitting it through the mask at the desired inscription.

A method and a device for recording large format (A5 to 1 x1.5m) digital image holograms according to. WO0142861 (LT4842), which significantly accelerates the production process of digital holograms. According to this method, the light modulator is an illuminated image formed from pixels taken from the corresponding several hundred 3D spatial images, the light modulator is illuminated by a coherent pulsed laser light beam, the modulated radiation is focused by a special lens with an optical constriction outside it, immediately sensitive substance. The photosensitive material is illuminated by a modulated pulse of light together with a non-modulated support pulse of laser radiation and is recorded by a holographic diffractive element (HDE) in a small area of ​​the photosensitive material known as a holopixel or hogel. After chemically or otherwise treating the photosensitive material and illuminating the HDE light so recorded with a direction identical to that of the unmodulated laser light during recording, the HDE "projects" the same spatial light modulator image from several hundred pixels taken from the respective paths. hundreds of 3D spatial images so that only one pixel image is projected in each direction. When the entire surface of a light-sensitive material is covered with such HDEs, their totality behaves like a normal hologram - ie different images are visible from different angles of view. Typically, digital image holograms recorded in this way are reflective holograms (ie, illuminated by the observer), but LT4842 mentions the possibility of writing bandwidth holograms in this way as well.

However, transmittance holograms produced in this way are made on light-sensitive material and could be used as warning signs only with the use of additional adhesives that degrade the transmittance properties of the hologram and require several additional technological operations to integrate them into the radiation shield.

The object of the present invention is to improve the known radiological screens by providing sufficient radiation protection and at the same time high optical transparency by using new transparent materials which do not contain lead as a filler. It would be desirable to incorporate into such a screen a diffractive optical element which warns of the danger and is visible only in the direction of the greatest danger.

The essence of the invention

This object is achieved by a group of inventions, namely a composition for radiation protection material, an optically transparent screen for radiation protection containing a filler of said composition, and a method for producing this optically transparent screen for radiation protection. All the inventions named by the group are united by the general inventive idea mentioned above.

The most important object of the group of inventions is a composition of radiation protection material having lead-free components with shielding properties in an organic polymer. What is new is that the unleaded component is ammonium metatungstate and the composition by weight is:

polyacrylamide 0.5-1 ammonium metatungstate 15-70, optimally 60 water remaining, where the density of the composition is about 1.2 to 2.5 g / cm³, The X-ray attenuation coefficient is 0.52 - 3.63 cm^-1, and the equivalent lead thickness of the 10 mm thick composition layer corresponds to 0.15 - 0.72 mm.

One of the most optimal examples of the implementation of said composition is a composition comprising 1% by weight of polyacrylamide and 60% by weight of ammonium metatungstate, characterized by about 2.05 g / cm³ density, about 2.47 cm^-1 X-ray attenuation coefficient, and the equivalent lead thickness of a 10 mm thick layer of this composition corresponds to 0.61 mm.

An optically transparent screen for radiation protection according to the present invention has a filler of the above-mentioned composition. This composition is filled through a filling opening with a transparent plastic container with parallel sides, on which the surface of one of the two parallel walls is embossed with a relief of a diffractive hoggel matrix, which contains information about the radiation danger sign and its direction of vision. Such a screen has an optical transparency of the filler, which is from 86% to 90%, optimally 89%.

The method of manufacturing an optically transparent screen for radiation protection includes the following steps:

- on the transparent parallel-side plastic container, one of the parallel walls bears the superficial relief of the diffractive hoggel matrix, which contains information about the radiation hazard sign and its direction of vision,

- preparing a composition of said radiation protection material in the form of a gel,

- the prepared gel fills the inside of said clear plastic container through the opening of the container,

- the filler of the prepared composition is sonicated and sealed in a container.

The radiation protection composition is prepared as follows:

(a) swells high molecular weight polyacrylamide in water, heating to 65-80 ° C, optimally to 70 ° C,

(b) adding ammonium metatungstate to a continuous stirring; and

c) continue stirring at a temperature of about 80 ° C until a gel forms, which is then sonicated at 50-60 ° C.

Before said gel of the radiation shielding composition cools down to room temperature, the filled container is further sonicated at 50-60 ° C before sealing.

At least one relief of a diffractive hoggel matrix containing information on the radiation hazard symbol and its direction of vision shall be embossed on the surface of the wall of one of the largest areas of the transparent container before filling.

In order to obtain the relief of the diffractive hoggel matrix on the light-conducting material containing the hoggel matrix of the digital hologram, apply an electrically conductive layer, electrolytically nickel-plate it, separate the nickel layer with a mirror image of the digital hologram surface relief and press way.

The combination of all these features makes it possible to produce an optically transparent polymeric shield for the radiation protection of personnel, free of substances dangerous to health and with a radiation warning sign visible in the direction of the greatest radiation hazard. The optical transparency of the screen filler is from 86% to 90%, optimally 89%, the X-ray attenuation coefficient is 0.52 - 3.63 cm^-1.

Brief description of the box

The invention is explained by the drawings where shown

FIG. 1 - radiological display with several directional warning signs.

FIG. 2 - radiological display with one directional warning sign.

Detailed description of the invention

Highly water-soluble tungsten compound ammonium metatungstate (NH4) 6H2Wi204o (AMV, solubility s ~ 160g / 100g H2O at 20 ° C) and water-soluble organic polymer - polyacrylamide are used for the production of radiation protection composition. Ammonium metatungstate solution, as well as a polyacrylamide-thickened composition (gel) of said tungsten compound, has a high X-ray absorption capacity. The mass fraction of tungsten in ammonium metatungstate (NH4) 6H2Wi204o is 75%. The composition is thickened with polyacrylamide to increase the safety of the X-ray suppression screens to prevent unexpected leakage of the composition from the screen, e.g. leaking the container due to mechanical damage or the like. The density of said composition (depending on the weight fraction of ammonium metatungstate in the composition) is almost twice and several times lower (<2.5 g / cm³) than the density of optically clear lead glasses used for X-ray suppression (approximately 4,6 g / cm³) (http://www.radiansa.com/radiation-shielding/lead-glass.htm)

An optically transparent screen for radiation protection according to the present invention consists of a transparent parallel-sided plastic container 1 on which the surface of one of the two parallel walls is embossed with a diffractive hoggel matrix 2. At the top, the container 1 has an opening or openings 3 for filling the composition according to the invention. Said diffraction hoggel matrix relief 2 contains information about the radiation danger sign and its direction of vision 4. A point light source 5, preferably a light emitting diode, is attached to the container 1 with the radiation absorbing gel for illuminating the diffraction hoggel matrix relief 2.

Sheets of clear plastic (polycarbonate, polymethyl methacrylate, polystyrene, styrene - acrylonitrile copolymer (SAN)) are made into a hollow hermetic container with a rectangular parallelepiped or other shape, but necessarily with two opposite parallel walls 1.

On the outer surface of the clear plastic container 1, before filling it with the composition described above, a transparent diffractive hogrel matrix relief 2 produced by digital holography is formed by embossing, projecting a radiological warning sign in the direction of maximum radiation hazard 4, i.e. the surface of the container is embossed with a diffraction grating containing information about the radiation hazard label, the matrix of which is produced by coating a digital hologram printed on a photosensitive material as a hoggel matrix by vacuum-thermal evaporation with a layer of electrically conductive silver 200 nm or thicker. Thereafter, the material with the digital hologram hoggel matrix coated with a silver layer is placed in a nickel-plating electrolyte, and an electrochemical deposition of nickel on the silver layer is performed. The formed nickel layer is mechanically separated from the photosensitive material by a matrix of digital hologram hogels. This nickel layer with a hologram on the surface is used for thermal embossing of the diffractive hoggel matrix 2 on the wall of a transparent container.

A gel of a composition of soluble tungsten compounds and organic polymers is produced to fill a clear plastic container 1 of the required composition. In a heat-resistant glass vessel (eg flask), add the calculated volume (mass) of distilled water at room temperature and place the calculated mass in a high molecular weight (M_r>10⁴) polyacrylamide (PAA). The unstirred and unheated mixture is maintained for about 0.5 h until the PAA swells in water. The mixture is then slowly stirred in a flask with a mechanical stirrer and heated to 70 ° C in a hot water bath. After reaching this temperature, the mixture is stirred for another 0.5 h. The resulting mass (within the solubility limit at room temperature) of ammonium metatungstate (NH4) eH2Wi2O40 is then added in small portions to the resulting clear, viscous and continuously stirred and heated to 80 ° C PAH gel. The resulting mixture was stirred at 80 ° C for an additional 0.5 h until the ammonium metatungstate was completely dissolved to give a homogeneous and clear composition (gel). After switching off the stirring, remove the flask containing the gel from the heated water bath and place it in a thermostated ultrasonic bath filled with water heated to 50 to 60 ° C. The gel is sonicated in the flask for at least 15 minutes to remove air bubbles dispersed from the gel during its preparation. The PAA and ammonium metatungstate compositions thus prepared have a pH of ~3.5.

Such a composition (gel) is filled with a clear plastic hollow container 1 as described above through the opening 3 before it has cooled to room (ambient) temperature.

In order for the relief of the diffractive Hogel matrix to form a spatial radiation hazard image in space, it must be illuminated by a point light source by attaching a point light source 5, preferably a light emitting diode, to the container with the radiation absorbing gel.

The individual stages of screen production are illustrated by the following examples, which do not limit the scope of the invention.

example - Composition (gel) production

In the production of a composition with high X-ray intensity suppression capacity from ammonium metatungstate (NH4) 6H2Wi204o and polyacrylamide, first, 2.5 g of nonionic polyacrylamide PAA is swollen and dissolved in 100 ml of distilled water. 150 g of ammonium metatungstate (NH4) 6H2Wi204o (AMV) are added to the resulting gel, heated to 80 [deg.] C. with vigorous stirring in small portions. The resulting composition comprises about 1% (w / w) nonionic polyacrylamide and about 60% ammonium metatungstate. Such a composition is abbreviated as 1PAA-60AMV.

The composition, density, optical transparency, and X-ray attenuation parameters of this composition and other analogously prepared compositions of different compositions are shown in Table 1.

table

Characteristics of the proposed composition for X-ray protective screens

<td>No.</td><td>Composition</td><td>Composition composition,% (m / m)</td><td>Tungsten 0 concentration in the composition,% (m / m)</td><td>Density, g / cm³</td><td colspan="2">Longitudinal attenuation coefficient, cm^-1</td><td>Poured 0 optical transparencies,%</td><td>Equivalent lead thickness of the 10 mm thick composition, mmPb</td>

<td> 1</td><td>1PAA15AMV</td><td>1% PAA 15% (NH4) 6H2Wl2O40 84% H₂O</td><td> -11%</td><td> 1,189</td><td> 0,52</td><td colspan="2"> 90</td><td> 0,15</td>

<td> 2</td><td>1PAA30AMV</td><td>1% PAA 30% (NH4) 6H2Wl2O40 69% H₂O</td><td> -22%</td><td> 1,390</td><td> 1,00</td><td colspan="2"> 90</td><td> 0,28</td>

<td> 3</td><td>1PAA50AMV</td><td>1% PAA 50% (NH4) 6H₂Wl2O40 49% H2O</td><td> -11%</td><td> 1,849</td><td> 2,19</td><td colspan="2"> 89</td><td> 0,57</td>

<td> 4</td><td>1PAA- 60AMV</td><td>1% PAA 60% (NH4)₆H₂Wi204o 39% H2O</td><td> -37,5%</td><td> 2,046</td><td> 2,47</td><td colspan="2"> 89</td><td> 0,61</td>

<td> 5</td><td>1PAA70AMV</td><td>1% PAA 70% (NH4) 6H₂Wl2O40 29% H2O</td><td> -52,5%</td><td> 2,475</td><td> 3,63</td><td colspan="2"> 86</td><td> 0,72</td>

From the following table, it can be concluded that the most suitable concentration of the mixture as a percentage for an optically transparent screen for radiation protection is: polyacrylamide 1, ammonium metatungstate. 60, water 29. The lead equivalent is then 0.61. At lower concentrations of ammonium metatungstate, the required equivalent lead thickness is not obtained, and at higher concentrations, the optical transparency of the screen begins to decrease. At 60% am.volfr. the transparency is 89%, at 70% am.volf. the optical transparency is 86%.

Example - Formation of a layer of nickel used to emboss a diffractive optical element on the wall of a container

A thin (about 200 nm) electrically conductive silver layer is coated on a photosensitive material already having a digital hologram hoggel matrix by vacuum-thermal evaporation. A material with a digital hologram hoggel matrix and a coated silver layer is placed in a nickel-plating electrolyte consisting of the materials listed in Table 2.

table

Composition of sulfamate nickel plating electrolyte

<td>Material</td><td>Concentration</td>

<td>Ni (II) sulfamate (Ni (NH₂SO₃) -4H₂O)</td><td>390-510 g / l</td>

<td>Ni (II) chloride (NiCl₂)</td><td>5-30 g / l</td>

<td>Boric acid (H3BO3)</td><td>35-40 g / l (saturated electrolyte)</td>

<td>Sodium dodecyl sulphate CH3 (CH₂) nOSO3Na</td><td>0.05-0.25 g / l</td>

<td>Glossy (composition not published)</td><td>1.5-2.3 ml / l</td>

Distilled deionized water with a specific resistance R> 10 ΜΩ is used as the solvent.

Electrochemical deposition of nickel on a silver layer is performed. Deposition process parameters: electrolyte pH value - from 3.8 to 4.2 (optimal - 4.0), Electrolyte temperature during nickel deposition process - from 40 ° C to 60 ° C (optimal - 50 ° C). The cathodic current density varies from 1 mA / cm² (at the beginning of the nickel deposition process) up to 3.5 mA / cm². Anode - titanium bag filled with Ni-0.1% NiS granules (INCO S-Nickel) and wrapped in a polypropylene fabric cover.

The formed nickel layer is mechanically separated from the photosensitive material by a matrix of digital hologram hogels. This layer of nickel with a hologram on the surface is used for thermal printing on a clear sheet of styrene-acrylonitrile copolymer (SAN). Thermal (pressure parameters: pressure - 0.3 MPa, temperature - 120 ° C, pressure duration - 5 s.

Advantages and application of the invention

Optically transparent polymeric shield for radiation protection, free of hazardous substances and with a radiation warning sign visible in the direction of the highest radiation hazard, features optical transparency (86% to 90%, optimally 89%) and an X-ray attenuation coefficient (0.52 - 3.63 cm^-1), and the equivalent lead thickness of a 10 mm thick composition layer corresponds to 0.15 - 0.72 mm. It is clear to the person skilled in the art that In this way, the invention is not limited to the specific embodiments of the invention mentioned above, but may have equivalent implementations and modifications within the scope of the claims of the invention.