X-ray protective shields

July 17, 1962

3,045,121

C. W. LEGUILLON

X-RAY PROTECTIVE SHIELDS

Filed April 7, 1959

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FIG. 8

ATTORNEY

United States Patent Office

3,045,121

Patented July 17, 1962

3,045,121

X-RAY PROTECTIVE SHIELDS

Charles W. LeguiUon, 211 Overwood Road, Akron, Ohio Filed Apr. 7, 1959, Ser. No. 804,839

Claims. (CI. 250—108)

This invention relates to X-ray protective shields for articles of wearing apparel which protect the wearer against the harmful action of X-rays, particularly to a flexible X-ray shield for apparel such as is needed by operators of X-ray equipment whose hands and/or other parts of the body are within the active X-ray field during the time the equipment is in operation.

It has long been recognized that X-ray protective apparel worn by operators of X-ray equipment, and particularly X-ray gloves, need be not only flexible to permit the operator to handle objects, such as surgical instruments, with facility, but also need have a capacity to stop X-rays and prevent them from passing through and impinging on the flesh of the operator. X-ray shields meeting some of these requirements have been made of rubber having dispersed therethrough a relatively high percentage of a finely divided material opaque to X-rays, such as finely divided metallic lead.

In such X-ray shields, as heretofore produced, a finely divided metallic lead highly impregnated rubber shield of a thickness of from about 0.06 to 0.075. of an inch has been employed, the thickness of the shield and the amount and effectiveness of the lead opaquing material being coordinated so as to provide a shield which stops, with a reasonable factor of safety, the X-rays impinging upon the shield. In practice, it is customary to provide the leadimpregnated opaquing shield of a glove, apron, etc., with a leather or fabric outer cover and a fabric inner liner, tiie cover to protect the rubber shield from damage by objects coming into contact therewith, as the instruments being handled by the operator, and the fabric lining to facilitate the slipping on of the rubber shield.

A dangerous defect in the opaqued X-ray shields, as heretofore and presently made, is that the X-ray shield in service develops cracks which render extremely dangerous the use of the X-ray protective apparel. The highly leadimpregnated rubber shield of present X-ray protective clothing has very low skin strength due to the high leadimpregnation of the surface portions, and hence in use the impingement of X-rays on, and the flexing of, the highly impregnated surface soon causes surface cracks to develop in the shield—cracks always start at the surface. The cracking of the X-ray shield is, however, initiated in the surface of the X-ray shield by the impingement of the X-ray beams on the surface causing ionization of the atmospheric gases, which results in what is known as “ozone-cracking,” the ozone cracks being focal points for failure due to flex fatigue.

Experience, as well as extensive tests, have amply demonstrated that the cracks always start on the surface of the lead-impregnated shield on which the X-rays impinge, the more readily because the high percentage of the finely divided opaquing material dispersed in the surface portions of the rubber shield imparts to the skin surface of the shield very low skin strength, in which low skin strength surface cracks start and gradually grow deeper and deeper until the thickness of the impregnated shield from the bottom of the crack to the inner surface of the shield is no longer adequate to check the passage of the X-rays through the shield. This is particularly hazardous because of the fact that the depth of these cracks cannot be detected from the surface of the shield, and the presence of these cracks is masked where a leather or outer fabric covering is employed, as is usually the case. Further, one or more of such cracks in the X-ray shield, as now pro2 duced, soon become so deep as to give little or no protection to the wearer, and, in certain instances, not infrequently in hospitals, the cracks extend completely through the X-ray shield without detection, so as to render the X-ray shield practically useless as a shield against the passage of X-rays therethrough, and extremely dangerous because these latent defects in the shield are not known to the wearer.

Experience and extensive testing have also amply dem⁰ onstrated that, as long as ozone-cracks and flex-cracks can be prevented from starting at the surface of the shield exposed to the impingement of X-rays, no inimical cracks will develop in the shield.

An object of the present invention is to provide an X-ray shield for wearing apparel that overcomes the above described defects of the shields of present X-ray protective clothing, and to provide an X-ray shield having the outer exposed surface of the shield of such a character that no ₉θ inimical cracks develop over an extended period of time.

A further object is to provide an X-ray shield that has a high skin strength surface that is highly resistant to ozone-cracking and flex-cracking and that will minimize the hazards now experienced with currently available _2g X-ray protective shields.

A still further object is to provide an X-ray shield having a relatively thick highly lead-impregnated barrier portion and a relatively thin high skin strength surface portion on the sides of the shield exposed to the impingement of ₃₀ X-ray beams.

Other objects of the invention will be evidenced from the following specification and the accompanying drawings, in which:

FIG. 1 is a frontal view in elevation of an X-ray shield 35 for a glove made in accord with one embodiment of this invention;

FIG. 2 is a side view in elevation of the X-ray shield shown in FIG. 1;

FIG. 3 is a view showing the shape of the hand ad40 mitting opening of the X-ray shield of FIG. 1;

FIG. 4 is an enlarged sectional view taken on line 4—4 of FIG. 1;

FIG. 5 is an enlarged fragmentary sectional view taken on line 5—5 of FIG. 1;

FIG. 6 is an enlarged fragmentary sectional view, similar to FIG. 5, of an embodiment of this invention showing the high skin strength portion on both the outer and inner surfaces of the barrier;

FIG. 7 is an enlarged fragmentary sectional view, 50 similar to FIG. 5, of a further embodiment of this invention;

•FIG. 8 is a view in elevation of an X-ray shield for an apron;

FIG. 9 is an enlarged fragmentary sectional view taken 55 on line 9—9 of FIG. 8;

FIG. 10 is an enlarged fragmentary sectional view, similar to FIG. 9, of another embodiment of this invention; and

FIG. 11 is an enlarged fragmentary sectional view, 60 similar to FIG. 9, of still another modification of this invention.

Referring to FIGS. 1 to 5, the numeral 10 represents the X-ray shield of this invention, having a relatively thick plastic barrier portion 11, highly impregnated with 65 X-ray opaquing material, and a relatively thin high skin strength portion 12 which forms a highly effective ozonecrack resisting and flex-crack resisting skin on the barrier portion 11, the two portions 11 and 12 being heat blended into an integral shield.

The barrier portion 11 consists of a flexible relatively thick plastic portion through which is dispersed a relatively high proportion of a material which is opaque to

3,045,121 ³

X-rays, such as lead powder, that is, finely divided metallic lead of a fineness to pass through a 200 mesh to 400 mesh screen, lead powder passing a 300 mesh screen having been found to be highly satisfactory. The proportion of lead to plastic may vary widely and is directly proportional to the thickness of the barrier portion 11 and to the voltage of the X-ray beams, against which protection is to be provided, the usual lead-impregnated barrier for X-ray shields being satisfactory, as set out more fully at pages 350 to 356 of “Physical Foundations of Radiology” by Otto Glasser et al., published by Paul B. Hoeber, Inc., of New York and London. Thus, where 100 parts of plastic by weight and 100 or more parts by weight of lead powder, passing a 300 mesh screen, are thoroughly intermixed, so that the lead powder is substantially uniformly dispersed through the plastic, a barrier 0.07 of an inch thick formed therefrom has an adequate opacity for an X-ray shield for a dentist’s X-ray protective glove. However, barrier portions 11 having up to 300 parts of lead powder to 100 parts of plastic by weight have been found to be practical for X-ray shields for protection against X-rays used for medical purposes.

The relatively thin high skin strength portion 12 is formed of a plastic which has a high tensile skin strength and in which an antiozonant may be dispersed, although this is not critical. Antiozonants constitute a well recognized class of chemicals which have the unique property of preventing the ozone-cracking and flex-cracking of plastics. See Rubber World for August 1954, at pages 636-642. Normally, from 2 to 8 parts of the antiozonant to 100 parts by weight of the plastic are employed to give high tensile skin strength and to give highly effective antiozone-cracking and anti-flex-cracking properties to the portion 12.

The barrier portion 11 and the high skin strength portion 12 are preferably surface-blended together in any well known manner, as by heat-setting or, vulcanizing the two portions 11 and 12 simultaneously to form an integral shield 10.

In the production of an X-ray shield, the barrier portion 11 may be made by extruding under pressure a flowable plastic mass having the opaquing material dispersed therethrough into a glove-shaped high pressure extrusion mold, the plastic mass and the mold both being preferably preliminarily heated to facilitate the flow of the plastic and the uniform distribution of the plastic throughout the mold. The mold is cooled and the molded barrier portion 11 of the shield 10 removed from the mold.

Alternatively, a liquid dispersion of the lead-impregnated plastic, either an aqueous or an organic solvent dispersion, is made and a ceramic or other form is dipped into the liquid dispersion to form a layer of the dispersion on the form, the dipping beipg repeated, one or more times, if necessary, to secure a desired thickness of the lead-impregnated plastic barrier portion 11 on the form. The liquid of the dispersion is evaporated leaving a barrier portion 11 of desired thickness on the form.

When the barrier portion 11 has been formed in either of the ways above described, the outer high skin strength portion 12 is preferably formed directly on the barrier portion 11, as by dipping the formed barrier portion 11 into a liquid dispersion of a plastic compound of high skin strength. The liquid dispersion of plastic from which the high skin strength portion 12 is made may be either an aqueous dispersion or an organic solvent dispersion, as is more fully hereinafter described, and the dipping may be repeated one or more times, if necessary, to secure the desired thickness of the outer high skin strength plastic portion 12. The two portions, viz., the relatively thick barrier portion 11 and the relatively thin high skin strength portion 12, are now vulcanized or cured in contact one with the other by placing the two assembled portions in a heated fluid medium, either steam heated air or hot water, for a time adequate to cause the two portions and 12 to blend one into the other into a unitary structure or shield 10.

In FIG. 6 is shown a modification in which shield 15 with a barrier portion 16 has a high skin strength portion 17 on the inner side of the barrier portion 16 as well as a high skin strength portion 18 on the outer side of the barrier portion 16. Such a construction is desirable where the shield 15 is used in a glove that is subjected to unusually high flexing stresses since such a shield structure 15 inhibits cracks from starting on the inner surface of the barrier portion 16, as well as the outer surface of the barrier portion 16.

Such a shield 15 may be produced by dipping a glove form in a liquid dispersion of a high tensile skin strength compound to form a thin inner high skin strength portion 17, then dipping the coated dipping form in a liquid dispersion of a lead-impregnated compound, the dipping being repeated one or more times to secure a desired thickness of the lead-impregnated barrier portion 16 on the form, and finally dipping in a liquid dispersion of high tensile skin strength compound to form a thin outer high skin strength portion 18. Normally, the liquid in the skin portions 17 and 18 and in the barrier portion 16 is allowed to evaporate after each dipping operation, and the high skin strength portions 17 and 18 and the barrier portion 16 blended into an integral structure by heat-setting or vulcanization.

In FIG. 7 is shown still another modification of the invention, in which the shield 20 is made up of a barrier portion 21, built up of pieces cut to shape from sheet stock containing high proportions of X-ray opaquing material, and is provided with an inner high skin strength portion 22 and an outer high skin strength portion 23. To illustrate, a glove dipping form is dipped in a liquid dispersion of a high skin strength plastic to place on the dipping form an inner high skin strength portion 22, from which the liquid of the dispersion is evaporated. Then the barrier portion 21 is built up on the high skin strength portion 22 from pieces cut from sheeted stock, highly impregnated with X-ray opaquing material, more fully hereinafter described, to suitable shapes to form the barrier portion 21. Thereafter, the dipping form with high skin strength portion 22 and barrier portion 21 thereon is dipped in a liquid dispersion of high skin strength plastic to add an outer high skin strength portion 23 on the outer side of the shield 20.

In FIG. 8 is shown a shield 25 for aprons, such as are commonly worn by operators of X-ray equipment, in which the apron shield 25 is provided with eyes 26, for attachment. The apron shield 25 may be made either by dipping, as presently to be described, or by forming the barrier portion 27 by calendering a plastic stock containing a sufficiently high percentage of X-ray opaquing material into a sheet of appropriate thickness, then surface coating the barrier portion 27 with a high skin strength plastic portion 28 on one side, as shown in FIG. 9, but preferably on both sides, as shown in FIG. 10, to make the apron shield reversible, that is, usable either side out, and then blending the barrier portion 27 and the high skin strength portion 28, by heat-setting or vulcanization, into an integral composite sheet, and finally cutting the apron shield 25 from the composite sheet.

Alternatively, the relatively thick calendered barrier portion 27 may be plied up, as between heated rolls, with a relatively thin calendered high skin strength portion 28, one or both sides of barrier 27, and the laminated sheets blended into a unitary structural shield 25, as disclosed in FIG. 11.

Certain advantages inure from the making of the apron shield 25 by a dipping process. Thus, a board-like dipping form, of a size and shape of the apron shield 25 to be made, is dipped in a liquid dispersion of a high skin strength plastic to form a relatively thin high skin strength portion 28 on each side of the dipping board; then the

3,045,121 . . - 5 . . . .

dipping board with the high skin strength portion 28 thereon is dipped into a liquid dispersion of a lead-impregnated compound, one or more times, to secure a desired thickness of the barrier portion 27, and finally the dipping board with the high skin strength portion 28 and the barrier portion 27 thereon is dipped into a liquid dispersion of a high skin strength plastic to form a relatively thin high skin strength portion on the outer side of the barrier portion 27. There is thus built up two apron shields 25, one on each side of the board, which may be separated by cutting away the plastic of the shields along the edges of the dipping board.

While it is possible to use lead powder, or other X-ray opaquing material in the barrier portion 11 of the shield 10 of this invention, applicant has discovered that it is in many cases preferable to employ lead in finely divided thin flaked form, since the thin lead flakes in the barrier portion 11 overlap each other in plate-like armor formation to provide a more effective shielding against the penetration of X-ray beams.

The flaked lead may be. made by placing minute atomized lead particles in a steel ball mill, with a solid coating material and enough solvent to make a flowable coating compound, and then by rotating the steel ball mill until the lead particles are converted into fine thin lead flakes. The solid coating material may be any of the solid fatty acids, such as stearic, lauric, palmitic, and the like, or solid hydrocarbon waxes, such as paraffin, ceresin, montan, carnauba, candelilla, beeswax, and the like. The solvent may be any of the well known hydrocarbon solvents, such as naphtha, gasoline, benzene, toluene, xylene, and the like. The coated fine thin lead flakes so made normally contain about 90% to 97% by weight , of metallic lead, the individual lead flakes being coated with a thin film which prevents the surfaces of the lead flakes from being oxidized during storage and use, a very important factor in lead X-ray opaquing material. A most satisfactory coating material has been found to be 5 to 10 parts by weight of stearic acid on 100 parts of lead in enough naphtha to make a flowable paste, the stearic acid coated fine thin lead flakes being 90% to 95% metallic lead and having a specific gravity of about 4.25 to 4.35. These coated fine thin lead flakes pass 90% through a No. 325 sieve.

Applicant has found that the stearic acid film-coated fine thin lead flakes readily mix into, and uniformly disperse through, solid plastic compounds, and also readily and uniformly disperse into latex or water dispersions of plastics, as well as in solvent dispersions of plastics. Because of its easier and more uniform dispersions into plastics in their various conditions and because of its higher opaquing capacity, film-coated fine thin lead flakes may advantageously be used as the X-ray opaquing material in the barrier portion of the X-ray shield of this application.

It is also possible to use finely divided lead, as pulverized lead powder, as the opaquing material, but because of the facts that finely divided lead is readily oxidized on contact with the air and that lead oxide is far less effective as an X-ray opaquing material, its use is recommended only when the lead powder can be handled in such a way as to minimize oxidation of the lead before and during its incorporation into the. plastic.

As has been hereinabove indicated, it is a prime objective of this invention to associate with an effective lead-impregnated barrier portion a relatively thin high skin strength portion, the two portions constituting an integral structure and thus to produce a superior X-ray shield.

The high skin strength portion may be made of a high carbon black rubber stock which normally has high ozonecrack and flex-crack resistance. Thus, a rubber stock composed of 50 parts by weight of carbon black to 100 parts of rubber with 2 to 3 parts each of zinc oxide, sulfur and stearic acid, and also a conventional age-resister, is effective and may be satisfactorily employed.

.-- -.6.. . .

Applicant has found that a preferred high skin strength plastic for the high skin strength portion of the shield is a high carbon black rubber stock containing 4 to 8 parts of any of a class of chemicals known as antiozonants, more 5 fully described hereinbelow.

A number of specific plastic compounds are outlined hereinbelow to illustrate the compounds from which the novel X-ray shield of this application can be made, it being understood that the invention of this application does not 10 reside in any specific plastic composition but resides in an integral X-ray shield having an X-ray barrier portion of a plastic highly impregnated with an X-ray opaquing material and a high skin strength portion, which high strength skin is highly resistant to cracking, the high skin strength 15 portion being made integrally a part of the surface of the barrier portion, which is exposed to X-ray beams, to produce an X-ray shield highly resistant to cracking under the impingement of X-ray beams thereagainst.

As illustrative of the lead-impregnated plastic of the 20 barrier portion, the following recipe has proved to be highly satisfactory.

A. Barrier Compound

Ingredients: Parts by weight

Rubber (smoked sheet) _________________·loo

Zinc oxide 5

Sulfur____. 3

Finely divided stearic acid coated lead flakes (90% lead)___175

Accelerator (benzothiozyl disulfide) 1

Age-resister (phenyl b-naphthylamine)______ 1

The above barrier compound A is mixed so as to disperse the coated lead flakes uniformly throughout the plastic mix. This barrier compound A is readily cal35 endered into a sheet of required thickness, or may be high pressure extruded into a high pressure mold to form barriers of suitable shape, such as a glove barrier. Alternatively, this barrier compound A may be dispersed in an aqueous or in a solvent liquid dispersion medium to form 40 a liquid dipping dispersion, from which the barrier portion of the shield may be made by the well known dipping processes.

The high skin strength portion of the shield may be made by utilizing a plastic rubber compound containing a flex-crack resisting and ozone-crack resisting antiozonant, of which compound the following is an example..

If. High Skin Strength Compound

Ingredients: Parts by weight

Rubber, GRS___;_____:100

Carbon black______2 50

Zinc oxide _ 3

Sulfur____;____________________________~~2

Stearic acid______________________. 2

Accelerator (benzothiozyl disulfide)____ 1

Age-resister (phenyl b-naphthylamine)_______1

Antiozonant (N,N' - di-sec-butyl-p-phenylenediamine) 4

As has been hereinabove stated, antiozonants are a well 60 known class of chemicals, any of which may be substituted in the above compound and include N,N'-di-sec-butyl benzidine, Ν,Ν'-diaminodiphenylmethane, N,N'-diphenylp-phenylenediamine, N,N'-di-sec-butyl 1,4-naphthylamine, N,N -bis(p-sec-butyl aminobiphenyl)-2,3-butane diamine, 65 N,N' - di - sec-butyl-p-terphenylenediamine, N,N'-di-secbutyl-2-methyl-p-phenylaminediamine, N,N'-di-sec-butyl1,2,3,4 - tetra-hydro-5,8-naphthylenediamine, p-phenyldiamine, benzidine, and numerous others.

The effectiveness of the above high skin strength portion 70 made from the above compound B has been demonstrated by actual service and also by tests made in accord with recognized standard testing practices.

Test specimens of standard size, viz: 6 x 1 x 0.075, where made from the above high skin strength compound 75 by compounding, milling, vulcanizing and cutting the

3,045,121 test pieces in accordance with the standard procedure specified in ASTM D15-527 of the American Society for Testing Material, 1916 Race Street, Philadelphia, Pa., and were tested for cracking in accordance with ASTM D518-44 specifications. After an exposure of 24 months, the test specimens were crack-free.

The above compound B may be calendered into relatively thin sheets, as from 0.005 to 0.02 inch thick, and the thin sheets of compound B laminated with the relatively thick calendered sheets of compound A, as sheets from 0.06 to 0.10 inch thick, to form the X-ray shield of this invention, having a relatively thick barrier portion and a relatively thin high skin strength portion. The two portions are preferably heat-cured after the two portions have been plied together to secure a heat-welded or surface-blended attachment between the two portions. Alternatively, the two portions may be made up in a cured state, and later plied up and attached to each other by a suitable sealing means, as by heat sealing, to produce an integral X-ray shield.

In the production of an X-ray shield of irregular shape, such as an X-ray shield for a glove, it has been found satisfactory to produce the shield by dipping a glove form in organic solvent dispersions of the compounds A and B. For example, a solvent dispersion is made of each of the compounds A and B, such as 10% solution of each of the compounds in an organic solvent, as benzene, gasoline, toluene, xylene or naphtha, to produce a liquid dispersion of each. Then, a suitable form, such as the usual glove dipping form, is first dipped into the liquid dispersion of compound A, with repeated dippings if necessary, until a requisite thickness of the lead-impregnated plastic of the compound A has been produced to form the barrier portion of requisite thickness to serve as an effective barrier against the X-ray beams of the X-ray instrument with the use of which the gloves are to be worn. The organic solvent in the formed-barrier portion is preferably evaporated from the plastic of the barrier portion. The glove form with the formed barrier portion thereon is now dipped into the solvent dispersion of compound B to build up on the formed barrier portion an outer high skin strength portion. The organic solvent is evaporated from the barrier portion and from the high skin strength portion, and the resulting X-ray shield is cured on the glove form, the curing operation serving to blend the barrier portion and the high skin strength portion at their contacting surfaces into a unitary X-ray shield. Thereafter, the X-ray shield is removed from the glove form and is ready for assembly with a leather or fabric cover and/or a fabric fining, where the latter are employed.

In an alternative method of the production of an X-ray Shield of in-egular shape, an aqueous dispersion of each of the compounds A and B is produced, in any of the well known ways of making artificial dispersions of rubber compounds in aqueous emulsions. A form of suitable shape, as a glove form, is dipped first in the aqueous dispersion of compound A, to form a barrier portion of requisite thickness. Where the form is first coated with a coagulant for the dispersion, any required thickness of the barrier portion may be made in a single dip. Thereafter, the coated form is dipped in an aqueous dispersion of compound B to apply the high skin strength portion thereto. The aqueous dispersing medium is evaporated from the formed portions and the two portions are then vulcanized preferably on the form, to produce a blending of the contacting surfaces of the barrier portion and the high skin strength portion, and thus to produce a unitary X-ray shield.

In place of the artificial dispersions of compounds A and B, as above described, the aqueous dispersions of compounds A and B may be made by starting with rubber latex, as a latex having 60% solids, and compounding therewith the remaining ingredients, recited in the recipes of compound A and compound B. Such disper8 sions of compounds A and B are employed in the manner above described for the artificial dispersions.

Similarly, any of the conventional molding and/or dipping plastics may be employed in the manufacture of the barrier portion and high skin strength portion of the X-ray shield of this invention, such plastics as the polyacrylics, the polyamides, the polyalkyds, the polyethylenes, the polypropylenes, the polystyrenes, the polyurethanes, the polyterpenes, the polyvinyls, copolymers of vinyl chloride and vinyl acetate, and like plastic polymers and copolymers, are all useful for the purposes of this invention.

By way of illustration, a flowable, heat-hardening plastisol comprising polyvinyl chloride has been found to be satisfactory for the production of both the barrier portion and high skin strength portion of the X-ray shields of this invention.

C. Barrier Compound

Ingredients: Parts by weight

Polyvinyl chloride powder (0.1 to 10.0 micron particles) 100

Dibutyl phthalate100

Triethanolamine borate 10

Finely divided stearic acid coated lead flakes (90% lead) 200

The above ingredients are thoroughly intermixed and form a flowable liquid plastisol, which may be employed as described above to form a glove by dipping in the liquid and building up the required thickness for the barrier portion. Upon heating to about 300° C., the above flowable plastic becomes a solid, as is the case with such plastisols. Alternatively, the liquid plastisol may be made into a sheet of requisite thickness by means of any plastic sheeting machine, as by extruding a ribbon of plastisol onto a moving belt Which is heated to solidify the plastisol sheet.

The high skin strength portion may be made of a similar plastisol, but substituting for the lead flakes carbon black and anti-flex-cracking chemicals. Thus,

D. High Skin Strength Compound

Ingredients: Parts by weight

Polyvinyl chloride powder (0.1 to 10.0 micron particles) 100

Dibutyl phthalate100

Triethanolamine borate 10

Carbon black__;__________________ 50

Antiozonant (N,N'-di-sec-butyl - p - phenylenediamine) 4

Where the barrier portion is made by dipping in the plastisol of compound C, and then heating to solidify the barrier portion, the form with the barrier portion thereon is dipped into the plastisol of compound D and heated, the heating solidifying the plastisol of the high skin strength portion and heat-welding it to barrier portion to form the integral X-ray shield. Alternatively, the plastisol of compound D may be made into a sheet of the desired thickness to serve as the high skin strength portion, then a sheet of barrier portion and a sheet of high skin strength portion plied up and heat-welded together to make the integral X-ray shield of this invention.

While a number of preferred embodiments of this invention have been disclosed, and several compounds and ways of producing the X-ray shields of this invention given by way of illustration, this invention is not intended to be limited to the specific embodiments, or to the specific compounds, or to the specific ways herein disclosed to produce the X-ray shields of this invention, and the many modifications and variations, which will be apparent to those skilled in the art, are intended to be included within the scope of the appended claims.