CA2645531C

CA2645531C - Radiation protective non-woven

Info

Publication number: CA2645531C
Application number: CA2645531A
Authority: CA
Inventors: Christopher John Brooke Dobbin; Ghislaine C. Bailey; Peter Andrew Sipos; Jamie A. Neilsen; Tracy Leanne Li; Marek Jon Crawford
Original assignee: Nova Chemicals Corp
Current assignee: Nova Chemicals Corp
Priority date: 2008-11-28
Filing date: 2008-11-28
Publication date: 2016-04-12
Anticipated expiration: 2028-11-28
Also published as: CA2645531A1

Abstract

Exposure to low level diagnostic radiation may be reduced by a polymeric non woven fabric in which at least one of the polymeric components contains from 15 to 50 weight% based on the weight of the component of one or more oxides or salts of an element having an atomic number greater than 49, in the absence of a coupling agent, said oxides and salts having a particle size of less than 1 micron.

Description

RADIATION PROTECTIVE NON-WOVEN
FIELD OF THE INVENTION
The present invention relates to polymeric filaments containing an elemental metal, an oxide or a salt of an element having an atomic number greater than 49 and single or multilayer non wovens fabrics and fabric structures made from such. Furthermore, the individual filaments of the present invention may be formed with a uniform monolayer cross-section or may be formed with more complex multi-layered structures including sheath/core, side-by- side or "islands-in-the-sea" cross-sections. The filaments have a radiation attenuation property designed to reduce exposure to low to medium level x-ray radiation with energies from about 60 to 120 kVp (e.g. for energies used for medical diagnostic as opposed to treatment purposes). The composition of the layers within individual filaments can be adjusted to facilitate improved processability, improved spinning consistency, and fabric strength and to tune the radiation attenuation properties for specific exposure energies.
BACKGROUND OF THE INVENTION
There is a concern about exposure to low level radiation for example radiation used for diagnostic purposes such as x-rays for dental and skeletal diagnostics and for example mammograms and various fluoroscopic procedures. While the patient may be partially protected typically with a heavy lead apron the attending physicians and technicians generally leave the room when the x-rays are taken. However, in some circumstances, for example in the operating theater, this may not be HATrevor\TTResponse\2008024Can Revised Nov25, 2015.doc possible or advisable. As a result over the longer term this may lead to concerns about illness due to radiation exposure.
Radiation attenuation might be considered as the flip side of radio-opacity. There is a significant amount of art on incorporating a single or several radio opaque threads into sponges, dressings, and the like used in operating theaters. There is also art on coating or printing sponges, dressings and the like with radio opaque compositions.
U.S. 4,935,019 issued June 19, 1990 to Papp Jr. assigned to Johnson & Johnson Medical Inc. teaches printing or extrusion of a radio opaque marker onto the surface of a sponge or fabric. The radio opaque material may be barium sulphate but it has a particle size of 5 microns or greater. The reference does not teach a monolayered or multi-layered cross-sectioned filaments nor a spunbond or melt blown non woven fabric made there from.
U.S. 5,725,517 issued March 10,1998 to DeBusk et al. assigned to DeRoyal Industries Inc. teaches a radio opaque thread which is incorporated for the full length of a woven material. It is not a non woven material. The thread may incorporate barium sulphate. The thread is an elastomeric material or cotton (Col 3 lines 40 -43 and 53 -60) but not a polyolefin.
U.S. patent 6,674,087 issued Jan 6, 2004 to Cadwalader et al.
assigned to Worldwide Innovations & Technologies, Inc. generally teaches impregnating a fabric with a radiation attenuation material (e.g. barium sulphate) the particles have a size from 840 -10 micron meters (micro meters - or microns) but a preferred size seems to be from 1.9 to 2,1

2 MATrevor\TTSpec\2008024Can.doc microns (Col. 7 lines 5 to 20). The reference teaches at Column 7 lines 20 to 35 that it is possible to form fiber spun threads. The reference fails to teach the threads of the present invention having a smaller particle size for the radiation attenuation material. The reference teaches away from the subject matter of the present invention.
U.S. 4,517,793 issued May 21, 1985 to Carus et al assigned to Vernon-Carus Limited discloses a single polypropylene fiber (filament) comprising barium sulphate and a coupling agent such as silanes and titanates. The present invention has eliminated the use of coupling agents.
There are a number of patents and application in the name of Radiation Shield Technologies such as U.S. Patent 6,281,515 issued August 28, 2001 in the name of Demeo et al. Generally these patents and applications teach impregnating a web with a composition containing a radio opaque material or extruding a sheet of radio opaque material and adhering it to web which may be non woven. This approach teaches against the present invention that requires incorporating the radiation attenuation materials directly into the non-woven fibers themselves.
The present invention consists of single or multi-component (layered) thermoplastic filament each layer or component of which may contain high loadings of fine particulate materials that are selected for their radiation attenuating capacity. Furthermore, these filaments may be formed into a single or multilayer non woven breathable fabric to provide protection against incidental x-ray and gamma radiation exposure. These materials may be combined with other fabrics and protective layers to

3 MATrevor\TTSpec\2008024Can.doc provide protection from several different hazards such as radiation, pathogens (e.g. blood borne pathogens), chemical hazards and the like.
SUMMARY OF THE INVENTION
The present invention provides a spun bond or melt blown mono-layered of multilayered (bi ¨ or multi-component) filament having a diameter from 10 to 20 microns comprising at least one layer consisting of a polymeric component selected from the group consisting of (but not limited to) polyethylene, polyethylene copolymers and elastomers (e.g.
polyethylenes having a density less than about 0.910 g/cc), polypropylene, polypropylene copolymers and elastomers (e.g. EP or EPDM or low density propylene ethylene copolymers), poly(ethyleneterphthalate), and copolymers consisting of one or more glycols selected from the group consisting of ethylene glycol, 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol and mixtures thereof and one or more terephthalic acids and C1_4 alkyl esters thereof, and mixtures of such acids and esters, to provide a molar ratio of total glycols to acids and or esters from 1.7:1 to 6:1 containing from 15 to 50 weight% based on the weight of the component of one or more elemental metals having an atomic number greater than 49, oxides or salts thereof and mixtures thereof of an element, in the absence of a coupling agent, said oxides and salts having a particle size of less than 1 micron.
DETAILED DESCRIPTION
The monolayer or multilayer filament of the present invention is formed into fabric using conventional spunbond or melt blown fiber spinning techniques. Individual filaments may consist of one or more

4 m:\Trevor\TTSpec\2008024Can.doc different thermoplastic compositions, one having a relatively higher melting temperature and the other having a lower melting temperature. When incorporated as the outer layer, the composition having the relatively lower melting temperature provides a mechanism to permit consolidation of the filaments using heat. Relatively mild heating conditions allow the individual filaments to partially fuse, while still maintaining their individual structure and producing for example a breathable non woven sheet or fabric. In a further embodiment of the invention, non-woven filament nnatts can be combined and consolidated into a much thicker cohesive, breathable fabric by thermally bonding the combined layers. Alternately, the spunbond or meltblown continuous matt or collections of stacked matts may be bonded using other methods such as, but not limited to hydroentanglement.
In accordance with the present invention the component having a relatively higher melting temperature (e.g. the core component) is selected from the group consisting of (higher density) polyethylenes, polyethylene copolymers, polypropylene and polypropylene copolymers, polyethylene terphthalate and copolymers of terephthalic acid or lower (C14) alkyl esters there of with a comonomer selected from a glycol such as ethylene glycol, (or a diol such as )1,3 cyclohexanedimethanol and 1,4 cyclohexanedimethanol.
The polypropylene useful in the present invention typically has a melting point from about 168 C to about 171 C. The polypropylene may be a homo polymer or may comprise small amounts of ethylene not more than about 5 weight % (e.g. from 100 to 95 weight % of propylene and M:\Trevor\TTSpec\2008024Can.doc from 0 to 5 weight % of ethylene). The polypropylene is typically isotactic and has a molecular weight (Mw) of at least about 60,000, typically from 75,000 to 300,000, preferably from 150,000 to 250,000 and a polydispersity (Mw/Mn) from about 5 to 10.
The poly (ethylene terphthalate) useful in the present invention generally has a melting point of about from 255 C to 280 C, typically from 255 C to 265 C preferably from 260 C to 265 C. The polymer may have a polydispersity (Mw/Mn) from about 1.90 to 2.10, typically from 1.95 to 2.05. The polymer may have molecular weight (Mw) from about 40,000 to about 60,000, typically from about 45,000 to about 50,000.
The copolymers consisting of one or more glycols selected from the group consisting of ethylene glycol, 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol and mixtures thereof and one or more terephthalic acids and C1-4 alkyl esters thereof, and mixtures of such acids and esters, to provide a molar ratio of total glycols to acids and or esters from 1.7:1 to 6:1, preferably less than 3:1, typically from 2.3:1 to 2.6:1.
Typically the glycol component comprises 1,3- or 1,4-cyclohexanedimethanol in an amount ranging from about 5 to about 50 mole % and ethylene glycol in an amount ranging from about 50 to about 95 mole % of the glycol component. Preferably the 1,3- or 1,4-cyclohexanedimethanol is present in an amount ranging from about 5 to about 50 mole /(:), more preferably about 8 to about 30 mole %. The 1,3- or preferably the 1,4-cyclohexanedimethanol may be a cis-, trans-, or cis/trans mixture of isomers. The ethylene glycol is preferably present in MATrevor\TTSpec\2008024Can doc an amount ranging from about 50 to about 95 mole % and more preferably about 70 to about 92 mole % of the glycol component.
In addition to the 1,3- or 1,4-cyclohexanedimethanol and ethylene glycol, the glycol component may include up to about 10 mole % of conventional glycols including, but not limited to, glycols containing about 3 to about 12 carbon atoms such as propylene glycol, diethylene glycol, 1,3- propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethy1-1,3-propaned101, 1,6-hexanediol, 2,2,4-trimethy1-1,3-propanediol, 2-ethy1-2-buty1-1,3-propanediol, 2,2,4,4-tetramethyl 1,3 cyclobutanediol, 2,4-dimethy1-2-ethylhexane-1,3-diol, 2-ethy1-2-isobuty1-1,3-propanediol, 1,3-butanediol, 1,8-octanediol, 2,2,4-trimethy1-1,6-hexanediol, thiodiethanol, and 1,2-cyclohexanedimethanol.
The dicarboxylic acid component contains isophthalic acid or esters thereof in an amount ranging from at least 10 mole % to about 50 mole %
and at least about 50 mole % of a dicarboxylic acid component selected from the group consisting of acids or esters of terephthalic acid, naphthalenedicarboxylic acid, 1,3- or 1,4-cyclohexanedicarboxylic acid and mixtures thereof. It should be noted that any of the naphthalenedicarboxylic acid isomers or mixtures of isomers may be used with the 1,4-, 1,5-, 2,6- and 2,7- isomers being preferred. Additionally, the 1,3- or 1,4-cyclohexanedicarboxylic acid moieties may be as the cis-, trans- or cis/trans mixtures of isomers. Depending upon the equipment used, the preferred dicarboxylic acid component contains either isophthalic acid and terephthalic acid or isophthalic acid and dimethyl terephthalate or dimethyl isophthalate and dimethyl terephthalate.

MATrevor\TTSpecµ2008024Can.doc Additional dicarboxylic acid components, (other than acids or esters of isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, and 1,3- or 1,4-cyclohexanedicarboxylic acid), may be added in amounts of up to about 10 mole /0. Suitable additional dicarboxylic acid components contain about 4 to about 40 carbon atoms and are described in U.S. Pat.
Nos. 5,608,031 and 5,668,243, herein incorporated by reference in their entirety. Preferably the additional dicarboxylic acid component is an acid or ester of an aromatic dicarboxylic acid, preferably having 8 to 14 carbon atoms, an aliphatic dicarboxylic acid, preferably having 4 to 12 carbon atoms, or a cycloaliphatic dicarboxylic acid, preferably having 8 to 12 carbon atoms.
The copolyesters may have an inherent viscosity, I.V., ranging from about 0.40 to 0.70,.preferably from about 0.40 to about 0.66, more preferably 0.42 to about 0.65, desirably from about 0.45 to about 0.58.
The I.V. of the copolyesters of the invention is determined by measuring the I.V. at 25 degree C. using 0.5 g polymer per 100 mL of a solvent consisting of 60% by weight phenol and 40% by weight tetrachloroethane.
The basic method of determining the I.V. of a copolyester is set forth in ASTM D-2857-70. The copolyesters produced with the lower I.V. values possess excellent colour and may accept dyes more easily than higher I.V.
copolyesters. Furthermore, low I.V. copolyesters are more easily dyed at lower temperatures and possibly more easily printed than similar higher I.V. copolyesters.
Other polymers which may be used in this invention include polyvinyl chloride, thermoplastic polyurethanes, polystyrene, polyvinyl MATrevor\TTSpec\20080240an.doc alcohol, and elastomers (styrene-butadiene-styrene, styrene-ethylene-butadiene-styrene, ethylene-propylene, ethylene-vinyl acetate copolymer, ethylene-methylacrylate copolymer, ethylene butylacrylate copolymer), rayon, acrylics and various nylons and polyamides.
One component of the filament should have a lower melting point than the other component(s). Preferably the lower melting component is a polyethylene homopolymer or copolymer, typically having a density greater than about 0.910 g/cc, preferably greater than 0.915 g/cc up to about 0.960g/cc, typically less than about 0.955 g/cc, preferably less than 0.945 g/cc desirably less than 0.935 g/cc..
In accordance with the present invention at least one of the components in the bicomponent filament is compounded with a radio opaque or radiation attenuating component. The radio opaque or radiation attenuating component typically is an elemental metal, salt or oxide of a metal having an atomic number greater than 49, preferably greater than 55. Typically the salts are sulphates although other salts such as halides sulphides and carbonates may be useful. Preferably, the metal of the radio opaque component is selected from the group consisting of barium, bismuth tin, antimony and tungsten. Typically the salts and oxides may be selected from the group consisting of barium oxide, barium sulphate, barium chloride, bismuth oxide, bismuth sulphate bismuth oxychloride, bismuth subcarbonate, tin oxide, antimony oxide, tungsten carbide, tungsten oxide and tungsten sulphate and mixtures thereof.
The radio opaque material must be of a size sufficiently small to pass through a spinerette of a spun bond or meltblow process. Typically m.\Trevor\TTSpec\2008024Can.doc the particles will have a size of less than 1 micron, preferably from 0.1 to 0.8 microns, desirably from 0.3 to 0.5 microns.
The radio opaque or radiation attenuating material may be added to one or more filament components in an amount up to 50 weight %, typically from 15 to 50 weight %, generally from 20 to 40 weight % of the polymer forming the component. The radio opaque or radiation attenuating materials are added to the polymer without the use of a coupling agent (0 weight % of coupling agent).
The radio opaque or radiation attenuating material may be added to the polymer using any conventional technique such as tumble blending, extrusion melt blending, and preferentially twin screw extrusion compounding or by the addition of a masterbatch. The components are then melt extruded through spinnerets having very fine openings, on the order of 0.2-0.6 mm. The filaments may be a core sheath type extrusion or two different strands could be extruded together to produce a fiber having two longitudinal parallel and joined segments (e.g. hemispheres or rectangular). Additional bicomponent and multi-component layer structures are known in the art such as a tri- or polly- lobal core with a sheath. The spinnerets may be in arrays of 500 or more or a spinning beam containing up to 30,000 holes. The extruded monolayer or multilayer filaments are then contacted with a cooling gas, typically quenched air, travelling at high velocity (from 3,000 to 8,000 m /min) to cool and partially or completely stretch (orient) the filaments. The filaments may then be laid on a travelling conveyor belt to form a matt which then passed through a consolidation device such as a heated roller.
M:\Trevor\TTSpec\2008024Can.doc The matt is then heated above the softening temperature of one of the components to partially fuse the filaments together to form a cohesive, breathable fabric. Alternately, the non-woven filament matts can be combined and subsequently consolidated into a much thicker cohesive, breathable fabric by thermally bonding the combined layers into a single fabric.
The resulting nonwoven fabrics may have a weight that ranges from about 8 up to about 800 g/m2; typically from about 13 to 180 g/m2.
In some instances where it is desired to improve the properties of the non woven and prior to or alternate to thermal bonding the web may be subjected to other consolidation methods including but not limited to treatment with a high pressure water jet to entangle the filaments of the web. This method is often referred to as hydroentanglement. Alternately, the non-woven filament nnatts can be combined and consolidated into a much thicker fabric by hydroentangling the combined layers.
Radio opaque materials are compounded uniformly into the various polymeric matrices used for individual filament components (cross sectional layers). The radiation attenuating compounded material can be incorporated into the individual filaments or fibers in a large multitude of architectures such as, but not limited to: core/sheath arrangements, "islands-in-the-sea", side-by-side (e.g. two hemispheres joined across a planar diameter), trilobal, trilobal surrounded by a sheath (sometimes referred to as bicomponent or multi component fibers) etc. The radio opaque compound can be incorporated into any portion of the fiber structure. Different radio opaque materials can be distributed in different M:\Trevor\TTSpec\2008024Can.doc components or layers of the filament structure. As an example, barium sulphate can be incorporated in a polypropylene matrix as the filament core, while bismuth trioxide is dispersed in a medium density polyethylene (MDPE) as the outer sheath. Certain radio opaque materials such as elemental tungsten, which is useful for attenuating high energy radiation may be used in the core in conjunction with a low energy attenuator such as barium sulphate in the sheath to tune the overall attenuation properties of the fabric.
Filament cross sectional design may be used to further tune the attenuation of the fabric. In one embodiment of this invention the high energy attenuation layer at the core of the filament may be extruded in a trilobal configuration to optimize energy capture and minimize scattering characteristics.
Depending on the inherent radiation shielding nature (i.e. mass absorption coefficient) and loading of the radio opaque material in the various filament layers, the resulting non woven may reduce the transmission of low to medium level diagnostic radiation (e.g. x-ray radiation from about 60 to 120 kVp) from about 10 to 30 A or more. For example a non woven having a loading of about 24 weight % of both barium sulphate and bismuth oxide in the fibers and a weight of about 100 g/m2 may reduce radiation transmission by about 7-8% when exposed to a direct x-ray beam at 60 kVp . The web could be doubled over a number of times (for example to an equivalent of about 800 gsm) to reduce the radiation transmission (increase the radiation attenuation) by about 44% at 60 kVp. The same 800 gsm material attenuates a120 kVp direct energy M:\Trevor\TTSpec\2008024Can.doc beam by about 27%. As the non woven is breathable at this effective gauge, even the folded over material would still be suitable for a disposable surgical mask, cap or "scrubs" and even medical drapes.
The non woven may be dyed using conventional colors and techniques known in the polyolefin arts.
The resulting non woven may be treated with an agent that tends to be more hydrophobic to reduce the potential for cross or through fabric transmission of bio hazards such as bodily fluids (e.g. blood, saliva, mucous and the like). Such agents are known to those skilled in the art.
Typically surfactants having a hydrophilic-lipophilic balance (HLB) less than about 5, preferably less than about 3 tend to be water repellant and would tend to repel bodily fluids. The non woven could be treated with such surfactants to reduce the adsorption and transmission of bodily fluids.
In accordance with a further aspect of the present invention the radiation attenuation non woven of the present invention may be combined with one or more other layers such as fireproof layers, biological hazard layers and explosion/projectile hazard. The biological hazard layer may be an impervious layer to prevent transmission of airborne biological hazards and nerve gases. Some impervious materials include layers (e.g.
extruded sheets) of elastomeric materials (e.g. butyl rubber, nitrile rubber, styrene butadiene rubber and the like) polyesters (e.g. MYLAR , PET, PEBT and the like), polyimide films, polyamide films, halogenated polyolefins (e.g. poly (tetrafluoro ethylene - TEFLON and fluorinated copolymers of ethylene and propylene). The fireproof layer(s) may contain heat reflective materials such as copper, silver, aluminum gold, beryllium MATrevor\TTSpec\2008024Can.doc and/or zinc. The explosion / projectile protective layer(s) may be woven layers of high tensile materials such as aramid fibers, high or ultra high molecular weight polyolefins such as polyethylene or polypropylene.
Other potential applications for the radiation attenuation fabric of the present invention either alone or in combination with other layers include clothing such as jumpsuits or fatigues, temporary shelters such as tents, construction material such as sheet material for drywall and wall paper and insulation wrap.
The present invention will now be illustrated by the following non limiting examples.
EXAMPLES
Example 1 Samples of sub-micron particle size barium trioxide (Bi203) were compounded into a suitable high flow rate polyethylene such as SCLAIRTM
2712 using a Coperion 25mm twin screw extruder. Highly dispersed compounds were prepared containing 20% and 30% by weight of sub micron particle sized Bi203; these were designated as 20Bi and 30Bi respectively. A similar sample containing 30% by weight sub-micron particle size barium sulphate was prepared in a similar manner and designated as 30Ba.
Non woven fabrics were produced on a pilot scale "bico" spunbond extrusion equipment manufactured by Hills Inc. (Melbourne FL). The line was equipped with two independently controlled 1 1/2" single screw extruders feeding a set of synchronized gear pumps that in turn fed a spinbeam assembly fitted with a 504 or 1008 hole sheath/core die plate.

MATrevor\TTSpec\2008024Can.doc Both 0.35 and 0.60 mm hole diameters were used. The throughput rate of molten material from each of the two extrusion systems was controlled to create filaments with specific ratios of sheath and core composition. In some instances, the same compounded material was presented to each extruder to create monolayer filaments.
Typical output rates were in the range of 0.5-0.7 grams per hole per minute. The molten filaments were extruded and accelerated in a venturi air stream to draw, orient and cool the filament stream. The filaments were deposited on a moving belt with the aid of a vacuum box and thermally bonded with an embossed, heated roller.
Three fabric samples were produced in this manner:
Sample A was a 100 g/cm3 material manufactured with compound 30Ba fed to each extruder (i.e. containing monolayer filament structures).
Subsequent ashing analysis confirmed that the fabric material contained 30% BaSO4 by weight.
Fabric samples were exposed to a direct beam of x-ray radiation of varying energy levels at a distance of 100 cm. The reduction in transmission (i.e. the degree of attenuation) was measured using standard X-ray calibration instruments.
Spun bond fabric Sample A was folded several times to increase the relative attenuation. Table la shows the effect of the number of layers on the measured radiation intensity at four ex-ray energy levels typically encountered in diagnostic medical facilities. Table lb illustrates the effective transmission reduction affected by the fabric, while Table lc shows the values converted to percent attenuation.
MATrevonTTSpec\2008024Can.doc Tables la, lb and 1 care presented below sequentially from a to c kV mAs Baseline Number of layers mR 1 2 4 8 16 60 100 489.7 477.8 465 438.6 393.7 317.3 80 50 444.4 369.2 100 50 643.6 541 120 50 917 787.1 kV mAs Percent Transmission 60 100 99.33 96.92 94.32 88.97 79.86 64.36 80 50 98.10 81.50 100 50 92.34 77.62 120 50 96.93 83.20 kV mAs Percent Attenuation 60 100 0 2.43 5.04 10.43 19.60 35.21 80 50 0 16.92 100 50 0 15.94 120 50 0 14.17 Example 2 Using the same technique, a 100 g/cm2 non woven spunbond fabric was manufactured with a bi-layer sheath/core structure, such that the weight based ratio of sheath material to core material was 80:20. The sheath material was composed of 20Bi, while the core material was composed of 30Ba. This was Sample B
Sample B was placed 1 m away from a steel target, which exposed to various levels of x-ray radiation in order to evaluate the effectiveness of the attenuating characteristic in the presence of scattered radiation.
Again, the fabric was folded in order to gain more data on the attenuation properties. Table 2 illustrates the scattered attenuation capabilities of Sample B.

MATrevor\TTSpec\2008024Can.doc Percent Attenuation kV mAs Baseline Number of layers 60 100 0 5.0 45.0 81 50 0 4.0 39.0 Example 3 Using the same technique, described in Examples 1 and 2, a 100 g/cm2 non woven spunbond fabric was manufactured with a bi-layer sheath/core structure, such that the weight based ratio of sheath material to core material was 80:20. The sheath material was composed of 30Bi, while the core material was composed of a standard 35 MFR
homopolymer polypropylene. This fabric was designated as Sample C
Sample C was exposed to a direct beam of x-ray radiation of varying energy levels at a distance of 100 cm. The reduction in transmission (i.e. the degree of attenuation) was measured using standard X-ray calibration instruments. Sample C was folded several times to increase the relative attenuation. Table 3a shows the effect of the number of layers on the measured radiation intensity at four x-ray energy levels typically encountered in diagnostic medical facilities. Table 3b illustrates the effective transmission reduction affected by the fabric, while Table 3c shows the values converted to percent attenuation.

MATrevor\TTSpec\2008024Can.doc Tables 3a, 3b and 3 c are presented below sequentially from a to c kV mAs Baseline Number of layers mR 1 2 4 8 16 kV mAs Percent Transmission 60 100 100 92.49 86.00 74.44 56.59 32.86 81 50 100 64.02 102 50 100 1 69.44 121 50 100 72.94 Percent Attenuation 60 100 0 7.51 14.00 25.56 43.41 67.14 81 50 0 35.98 .
102 50 0 30.56 121 50 0 27.06 .
Sample C was also placed 1 m away from a steel target, which exposed to various levels of x-ray radiation in order to evaluate the effectiveness of the attenuating characteristic in the presence of scattered radiation. Again, the fabric was folded in order to gain more data on the attenuation properties. Table 4 illustrates the scattered attenuation capabilities of Sample C.

Percent Attenuation kV mAs Baseline Number of layers 60 100 0 1.0 6.0 18.0 36.0 57.0 , 81 50 0 0.0 5.0 14.0 30.0 48.0 MATrevor\TTSpec\2008024Can.doc Example 4 Using the same technique employed in Examples 1-3, a 100 g/cm2 non woven spunbond fabric was manufactured with a bi-layer sheath/core structure, such that the weight based ratio of sheath material to core material was 10:90. The sheath material was composed of polypropylene homopolymer (35 MFR) while the core material was composed of 20Bi.
This was Sample D.
Sample D was placed 1 m away from a steel target, which exposed to various levels of x-ray radiation in order to evaluate the effectiveness of the attenuating characteristic in the presence of scattered radiation.
Again, the fabric was folded in order to gain more data on the attenuation properties. Table 5 illustrates the scattered attenuation capabilities of Sample D.

Percent Attenuation kV mAs Baseline Number of layers 60 100 0 7.7 17.1 31.8 50.7 81 50 0 5.8 12.2 25.2 41.7 M:\Trevor\TTSpec\2008024Can.doc

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A spun bond or melt blown mono-layered or multilayered filament having a diameter from 10 to 20 microns comprising at least one layer consisting of a polymeric component selected from the group consisting of polyethylene, polyethylene copolymers and elastomers, polypropylene, polypropylene copolymers and elastomers, poly(ethyleneterphthalate), and copolymers consisting of one or more glycols selected from the group consisting of ethylene glycol, 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol and mixtures thereof and one or more terephthalic acids and C 1-4 alkyl esters thereof, and mixtures of such acids and esters, to provide a molar ratio of total glycols to acids and or esters from 1.7:1 to 6:1 containing from 15 to 50 weight%, based on the weight of the polymeric component, of one or more elemental metals having an atomic number greater than 49, oxides or salts thereof and mixtures thereof of an element, in the absence of a coupling agent, said oxides and salts having a particle size of less than 1 micron.

2. The filament according to claim 1, wherein the particle size of said one or more oxides or salts of an element having an atomic number greater than 49, is from 0.1 to 0.8 microns.

3. The filament according to claim 2, wherein said element having an atomic number greater than 49 is selected from the group consisting of barium, bismuth, tin, antimony and tungsten.

4. The filament according to claim 2, wherein said element having an atomic number greater than 49 has an atomic number greater than 55.

5. The filament according to claim 4, wherein said salts of elements having an atomic number greater than 55 are selected from the group consisting of sulphates, halides, sulphides, and carbonates.

6. The filament according to claim 5, wherein said salts and oxides of elements having an atomic number greater than 55 are selected from the group consisting of barium oxide, barium sulphate, barium chloride, bismuth oxide, bismuth sulphate bismuth oxychloride, bismuth subcarbonate, tin oxide, antimony oxide, tungsten carbide, tungsten oxide and tungsten sulphate and mixtures thereof.

7. The filament according to claim 6 wherein said salts and oxides of elements having an atomic number greater than 55 and mixtures thereof are present in said at least one layer in an amount from 20 to 40 weight %
based on the weight of the component.

8. The filament according to claim 7, comprising components in a core shell formation with the polyethylene being the shell.

9. The filament according to claim 8 wherein the core is polypropylene.

10. The filament according to claim 8, wherein the core is a polymer selected from the group consisting of poly(ethylene terphthalate), and copolymers consisting of one or more glycols selected from the group consisting of ethylene glycol, 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol and mixtures thereof and one or more terephthalic acids and C1 -4 alkyl esters thereof, and mixtures of such acids and esters, to provide a molar ratio of total glycols to acids and or esters from 1.7:1 to 6:1.

11. The filament according to claim 7, wherein each component is hemispherical in cross section and the diameters of the hemispheres are joined.

12. The filament according to claim 11, wherein one hemisphere is polypropylene and the other is polyethylene.

13. The filament according to claim 11, wherein the one hemisphere is a polymer selected from the group consisting of poly(ethylene terphthalate), and copolymers consisting of one or more glycols selected from the group consisting of ethylene glycol, 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol and mixtures thereof and one or more terephthalic acids and C1-4 alkyl esters thereof, and mixtures of such acids and esters, to provide a molar ratio of total glycols to acids and or esters from 1.7:1 to 6:1 and the other hemisphere is polyethylene.

14. The filament according to claim 8, which is further consolidated with similar filaments to form a breathable flexible nonwoven sheet.

15. The filament according to claim 11, which is further consolidated with similar filaments to form a breathable flexible nonwoven sheet.

16. A multilayer fabric comprising as at least one layer the nonwoven sheet according to claim 14.

17. A multilayer fabric comprising as at least one layer the nonwoven sheet according to claim 15