AU595453B2

AU595453B2 - An x-ray opaque building material

Info

Publication number: AU595453B2
Application number: AU17377/88A
Authority: AU
Inventors: Ronald Desmond Carter; Donald Coltman
Original assignee: PLASTER SUPPLIES Ltd
Current assignee: PLASTER SUPPLIES Ltd
Priority date: 1987-06-04
Filing date: 1988-06-02
Publication date: 1990-03-29
Anticipated expiration: 2008-06-02
Also published as: AU1737788A

Description

N

(I

/1: Lg IIj~ 0 MONO -on 59545 This document contains the amendments made under Section 49 and is correct for printing. COMMONWEALTH OF AUSTRALIA Patents Act 1952 It I 1 t t 4 4 o 14 I I 4*4 I Name of Applicant Address of Applicant Actual Inventors Address for Service PLASTER SUPPLIES LIMITED Ellis Street South, Frankton, Hamilton, New Zealand DONALD COLTMAN and RONALD DESMOND CARTER GRANT ADAMS COMPANY, Patent Trade Mark Attorneys, 333 Adelaide Street, BRISBANE. QUEENSLAND. 4000

AUSTRALIA.

ON FOR THE INVENTION ENTITLED: COMPLETE SPECIFICATI "AN X-RAY OPAQUE BUILDING MATERIAL" The following statement is a full description of the invention including the best method of performing it known to the applicant.

J- 0 2 The present invention relates to an x-ray opaque building lining material and a method of forming same.

Where x-rays are generated and used, for example for diagnostic purposes in the x-ray unit of a hospital, it is necessary to ensure that the x-rays, which at significant strengths or power levels can be harmful, are suitably contained. While x-ray machines in hospitals for example 1o not generally generate x-rays at dangerous levels it is nonetheless generally Go 0 8d desirable to minimise unnecessary exposure of people to a 0 o, x-rays and undesirable therefore for the x-rays to o o0 escape. Accordingly, x-ray units are generally lined with a material that is opaque to x-rays so that they may not escape. The material commonly used is lead, in P. the form of lead sheeting. Typically the floor, walls and ceiling of a hospital x-ray unit are lined with lead sheeting. However, an x-ray resistant material lead is relatively expensive. The present invention provides a material that is more economic cost-wise or which at r l least provides a useful alternative.

In broad terms the invention may be stated to comprise in a first aspect an x-ray opaque building lining solid sheet panel product suitable for lining tbe walls, ceilings or floors of a building, formed from a 3 casting material and with which barytes as a powder has been mixed-in measured quantities together with water and any fillers, sealers, hardeners or other components and cast to form a solid board or sheet.

In a second aspect the invention may be stated in broad terms to comprise a method of forming such a building lining material which optionally includes mixing chopped fibreglass roving with the mixture before casting to provide reinforcing in the completed panel too product.

r t Barytes is barium sulphate. It is a white powder which is naturally occurring although it may also be produced synthetically. It is non-toxic and insoluble in water. As it is dense it is relatively heavy. Most significantly, it is opaque to x-rays.

A casting material from which the building lining material of the invention may suitably be formed is Plaster-of-Paris or some other equivalent material.

Barytes powder is either dry mixed with Plaster-of-Paris 1 in measured quantities before the plaster is mixed with water and with any other component such as sealers, fillers, hardeners or the like or is added to the wet plaster mixture. The mixture is subsequently cast or set in the usual manner to form the panel product of the 4 #9 0 t t invention as a solid board or sheet. It is preferred that the completed board or sheet include some form of reinforcing such as chopped fibreglass roving or the like.

It is important that the barytes be thoroughly mixed so that in the completed board the barytes is distributed as evenly or uniformly as possible over the area of the completed board. If the barytes is not evenly distributed through the board, areas of low barytes concentration occur and these may possess less than the minimum acceptance level of x-ray opacity.

As stated, in the case of Plaster-of-Paris building lining materials the barytes may be dry mixed with the dry Plaster-of-Paris in measured quantities prior to wet mixing of the barytes/plaster mixture with the other components that go to make up the board, such as reinforcing, sealing, filling and hardening components. The barytes to Plaster-of-Paris ratio may suitably be of the order of 1.2 to 1.8:1 by weight although preferably in the order of 1.5:1 by weight. In a manufactured (dry) board the barytes comprises about to 75% by weight of the board, the Plaster-of-Paris to 50%, and sealers, fillers and hardeners about However best results are achieved when the barytes comprises about 60% by weight of the board and the L r p~j i iii

*T

C: i' k Plaster-of-Paris about 35%. Barium sulphate particle size is 100% finer than 60 microns. The finished boards resemble gypsum plaster board.

In use of x-ray opaque board of the 'invention, to line a hospital x-ray room for example, sheets of the board are applied and fixed to the walls and ceiling (and floor if necessary). The boards are suitably glued in position, with BOSTIK wall board adhesive for example, and it is recommended that angles and joints be fixed tight with no gaps. Joints between adjacent boards have lead strip, typically 10mm wide and imm thick applied to the rear. Stopping of joints and the like is carried out in the usual way and the completed lining may be sealed and decorated in the usual way.

The following example further illustrates the invention.

EXAMPLE

'A building lining board in accordance with the invention was produced as follows: Barytes A Grade Fines powder was dry mixed by machine with dry Plaster-of-Paris in desired proportions (see below). This dry mixture was then weigh batched into clear water to which had previously been added 6 Sisaseal and E.P. hardener, and the suspended components were thoroughly mixed. The wet mixture was then poured on to a casting table and chopped fibreglass rovings were rolled in, to provide reinforcing in the finished board.

The mixture was allowed to set and harden and was then removed to a dryer for overnight drying. Boards of dimensions 2400 x 1200 mm and thicknesses of 12.5 mm nominal and 16 mm nominal were produced. The 12.5 mm panel has a dry weight of 65 kg (and a wet weight of 92.16 kg).

The measured quantities per square metre of the board of components were by weight as follows: Barytes Kobar 40A 15.75 kg Victor Casting Plaster 8.55 kg Water 6.25 kg Fibreglass Rovings .04 kg Sisaseal 9 ml D.E.P. Wetting Agent 100 ml Gum Acacia 200 ml The lead equivalence of 12-5 mm thick board produced in accordance with the invention has been tested as follows: A-i-' 1 NARROW BEAM GEOMETRY The exit exposure for narrow beam geometry was

I

1.

7 measured using a 0.6 cc 'Farmer' ionisation chamber and a Therados RDM2A electrometer. Attenuations behind different areas of the board sample under test were measured and compared with those measured for known thicknesses of lead. The results are shown in Table 1.

TABLE 1 X-Ray Equipment Beam Parameters Lead Filtration kVp H.V.T. keV Equivalence (mm) (mmAl) (mm) Philips RT-100 1.7 Al 100 2.26 30* 1.05 Stanford 140-10 0.25 Cu 140 7.75 55* 0.75 Al Technetium 99m 140 0.3 effective keV BROAD BEAM GEOMETRY Radiographs of the board samples were made on sheets of Kodak XTL-2 X-ray film with the samples placed beside a lead step wedge. Using a Therados RFA3 densitometer the lead equivalence of the sample was obtained by scanning the barytes and lead wedge areas of the films for comparable areas of optical density. Five scans across different areas of the board were carried out. Each scan length was approximately 100mm long and 8 samples were taken at 2mm intervals, using a 2mm optical window. Table 2 shows the standard deviation and minimum value of the measured lead equivalence.

TABLE 2 Mean Lead Worst Case Number of Standard Equivalence Lead Equivalence Sample Points Deviation (mm) (mm) x n o 1.05 1.00 250 3% s~ .1 The results evidence the effectiveness of barytes board in accordance with the invention as an alternative to conventional lead sheeting.

The foregoing describes our invention including a preferred form thereof. Alterations and modifications as will be obvious to those skilled in the art are intended to be incorporated within the scope hereof, as defined in the following claims.

A1

Claims

6. 1. An x-ray opaque building lining solid sheet panel to an product suitable for lining the walls, ceilings or floors of Plast a building, formed from a casting material and with which 1.5:1 barytes as a powder has been mixed in measured quantities
7. together with water and any fillers, sealers, hardeners or to other components and cast to form a solid board or sheet. subst and t 2. An x-ray opaque building lining panel product 0 according to claim 1 wherein the casting material from which I 0 0 oo oo 8. o. oo said lining material is formed comprises Plaster-of-Paris. 9 o 0 S° to an S :,QV subst 3. An x-ray opaque building lining panel product Plast according to any one of the preceding claims wherein the completed board or sheet additionally includes reinforcing.
9. S- to ar 4. An x-ray opaque building lining panel product 100% according to claim 3 wherein the reinforcing comprises I micrc chopped fibreglass roving. An x-ray opaque building lining panel product i. linii according to any one of claims 2 to 4 wherein the barytes to mate Plaster-of-Paris ratio prior to wet mixing is substantially quan in the range of 1.2:1 to 1.8:1 by weight. shee floo *.dist effe 6. An x-ray opaque building lining material according to any one-of claims 2 to 5 wherein the barytes to Plaster-of-Paris ratio prior to wet mixing is substantially 1.5:1 by weight. 7. An x-ray opaque building lining material according to any one of claims 2 to 6 wherein the barytes comprises substantially 45% to 75% by weight of the completed product .and the Plaster-of-Paris substantially 20% to 50% by weight. cog 8. An x-ray opaque building lining material according o to any one of claims 2 to 7 wherein the barytes comprises O: t substantially 60% by weight of the completed product and the Plaster-of-Paris substantially 35% by weight. 9. An x-ray opaque building lining material according to any one of the preceding claims wherein substantially 100% of the barytes powder has a particle size finer than microns.
10. A method of forming an x-ray opaque building t Ilining material including the steps of mixing a casting material, water, and barytes as a powder, in measured quantities, casting the mix-ure to form a solid board or sheet in a form suitable for lining the walls, ceilings, or floors of a building and incorporating therein and distributing therethrough to provide x-ray opacity an effective amount of barytes. U 11 i1. A method of forming an x-ray opaque building lining material according to claim 10 wherein the barytes powder is dry mixed with the casting material in measured quantities before said casting material is mixed with water and with any fillers, sealers, hardeners or other components or is added to the wet plaster mixture.
12. A method of forming an x-ray opaque building lining material according to claim 11 wherein the casting material comprises Plaster-of-Paris.
13. A method of forming an x-ray opaque building lining material according to any one of the preceding o 0O 15 claims including adding reinforcing for the completed 00 panel product. 9 Q 4 99 o0 V, 14. A method of forming an x-ray opaque building lining material according to claim 13 including mixing chopped fibreglass roving with the mixture before casting to provide reinforcing in the completed panel product. ori t4
15. A method of forming an x-ray opaque building lining material according to any one of claims 12 to 14 wherein the barytes to Plaster-of-Paris ratio prior to 'U wet mixing is substantially in the range of 1.2:1 to 1.8:1 by weight. 4 z :1 rri4 i 1 12
16. A method of forming an x-ray opaque building lining material according to any one of claims 12 to wherein the barytes to Plaster-of-Paris ratio prior to wet mixing is substantially 1.5:1 by weight.
17. A method of forming an x-ray opaque building lining material according to any one of claims 12 to 16 wherein the barytes comprises substantially 45% to 75% by weight of the completed product and the Plaster-of-Paris substantially 20% to 50% by weight. o
18. A method of forming an x-ray opaque building lining material according to any one of claims 12 to 17 :0I0°: wherein the barytes comprises substantially 60% by weight of the completed product, the Plaster-of-Paris substantially by weight.
19. A method of forming an x-ray opaque building Slining material according to any one of claims 10 to 18 7, wherein substantially 100% of the barytes powder has a particle size finer than 60 microns. An x-ray opaque building lining material substantially as herein described. 6 1 .1 11
21. A method of forming an x-ray opaque building lining material substantially as herein described. DATED this fifteenth day of December 1989 PLASTER SUPPLIES LIMITED by its Patent Attorneys GRANT ADAMS COMPANY I I .1 'S S Sd aP a V S. *4 4 a A _YL:_