Radiant energy – Radiation controlling means – Shields
Patent
1989-11-21
1991-10-22
Anderson, Bruce C.
Radiant energy
Radiation controlling means
Shields
2505161, G21F 302
Patent
active
050598074
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a protecting barrier against ionizing rays of the .gamma. type and/or X-rays, comprising a flexible sheet in which particles of an agent absorbing said rays are dispersed.
Clothes and accessories protecting against X-rays are known from U.S. Pat. No. 3,883,749.
These clothes and accessories are made of a polymeric material having a thickness comprised between 125 and 625 microns and containing from 10 to 45% by weight of a X-ray absorbing agent selected among uranium dioxide, lead oxide and the mixtures thereof. This polymeric material is coated on both sides with a thin layer of polymeric material, these layers being not loaded with an absorbing agent.
These clothes and accessories according to U.S. Pat. No. 3,883,749 have several disadvantages, such as the following: material on both sides of the layer loaded with lead; manufacturer of such clothes and accessories in order to comply with the regulations relating to work safety or to the environmental protection, and
An object of the present invention is to avoid these drawbacks.
The barrier of the type described in the first paragraph of the present specification is essentially characterized in that the absorbing agent is selected among the bismuth and the oxides, hydroxide and salts of bismuth. This agent is, preferably,. the bismuth oxide and has a particle size lower than 40 microns, preferably lower than 10 microns and particularly lower than 5 microns.
According to a feature of the protection barrier according to the invention, the flexible sheet contains from 30 to 80% by weight of absorbing agent and is made of a polymeric material and, preferably, of a polyethylene having a density near to about 0.91.
Other features and details of the invention will appear from the following detailed description in which reference is made to the single figure of attached drawing which is a cross section of a part of a protection barrier according to the invention.
In this single FIGURE, a protection barrier designated generally by the reference 1, comprises a single flexible sheet 2 wherein particles 3 of an agent absorbing the ionizing rays of the .sctn. and/or X type are dispersed, this agent being selected among the bismuth and the oxides, hydroxide and salts of bismuth.
Due to the use of bismuth or of one of its oxides, hydroxide or salts, it is no more necessary to cover the protection barrier 1 with a layer intended to avoid the contact of a user with the absorbing agent, since the bismuth, its oxides, hydroxide and salts do not have the toxic character of the lead compounds.
The flexible sheet 2 is made of a polymeric material such as rubber, silicone, polyurethane, polyethylene, polypropylene or polyvinyl chloride. This sheet is preferably made of polyethylene and particularly of very low density linear polyethylene, so that this sheet has also an excellent absorption with respect to the neutrons.
This sheet 2 may contain from 30 to 80% by weight of particles of bismuth, bismuth oxides, bismuth hydroxide or bismuth salts. Proportions of absorbing agent particles of more than 60% by weight are possible, due to the use of particles having a particle size lower than 10 microns and preferably lower than 5 microns. Such a particle size may be obtained by micronizing or disintegration.
The particles of bismuth-containing absorbing agent may advantageously be coated with a silicone, such as polymethylsiloxane, this coating causing a better mechanical binding between these particles and the polymeric material.
Moreover, the use of particles having a particle size lower than 10 microns and, preferably, lower than 5 microns allows to obtain a flexible sheet 2, for example a sheet of polyethylene having a density equal to 0.906, loaded with 70% by weight which is homogeneous and which does not have surface irregularities.
Due to this homogeneous distribution of absorbing agent particles, the user has the benefit of an identical protection against the .gamma. rays and/or the X-rays along the entire surface of the flexible sheet 2.
The
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Carlier Christian
Kersten Jean
Lombard Etienne
Anderson Bruce C.
Baxter International Inc.
Flattery Paul C.
Pierce Kay H.
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