U.S. patent application number 10/734680 was filed with the patent office on 2008-06-05 for lead-free mixture as a radiation protection additive.
Invention is credited to Peter-Alexander Gottschalk, Detlev Joachimi, Hardy Jungermann, Konstantin Awtonomowitsch Kapitanow, Jurgen Kirsch, Richard Kopp, Alexander Iwanovitsch Korschunow, Edgar Leitz, Klaus Mader, Jelena Saweljewna Nasarowa, Wladimir Michajlowitsch Nikitin, Heinz Pudleiner, Igor Leonidowitsch Ryshakow, Gennadij Grigorjewitsch Sawkin, Burkhard Werden, Klaus Zander.
Application Number | 20080128658 10/734680 |
Document ID | / |
Family ID | 32598074 |
Filed Date | 2008-06-05 |
United States Patent
Application |
20080128658 |
Kind Code |
A1 |
Jungermann; Hardy ; et
al. |
June 5, 2008 |
LEAD-FREE MIXTURE AS A RADIATION PROTECTION ADDITIVE
Abstract
The present invention provides a mixture containing a) at least
26 wt. % of gadolinium and b) one or more elements, alloys and/or
compounds from the group consisting of barium, indium, tin,
lanthanum, molybdenum, niobium, tantalum, zirconium and tungsten, a
process for the preparation of this mixture, use of the mixture as
radiation protection, use of the mixture to prepare polymeric
radiation protection substances, a process for preparing radiation
screening rubbers, thermoplastic materials and polyurethanes, a
process for preparing products from the polymeric radiation
protection substances and products made from these polymeric
radiation protection substances.
Inventors: |
Jungermann; Hardy; (Werl,
DE) ; Kirsch; Jurgen; (Leverkusen, DE) ;
Pudleiner; Heinz; (Krefeld, DE) ; Werden;
Burkhard; (Leverkusen, DE) ; Leitz; Edgar;
(Dormagen, DE) ; Joachimi; Detlev; (Krefeld,
DE) ; Gottschalk; Peter-Alexander; (Koln, DE)
; Zander; Klaus; (Muhlheim, DE) ; Mader;
Klaus; (Marienheide, DE) ; Kopp; Richard;
(Koln, DE) ; Korschunow; Alexander Iwanovitsch;
(Sarov, RU) ; Kapitanow; Konstantin Awtonomowitsch;
(Sarov, RU) ; Sawkin; Gennadij Grigorjewitsch;
(Sarov, RU) ; Nikitin; Wladimir Michajlowitsch;
(Sarov, RU) ; Nasarowa; Jelena Saweljewna; (Sarov,
RU) ; Ryshakow; Igor Leonidowitsch; (Sarov,
RU) |
Correspondence
Address: |
LANXESS CORPORATION
111 RIDC PARK WEST DRIVE
PITTSBURGH
PA
15275-1112
US
|
Family ID: |
32598074 |
Appl. No.: |
10/734680 |
Filed: |
December 12, 2003 |
Current U.S.
Class: |
252/478 ;
523/137 |
Current CPC
Class: |
G21F 1/10 20130101; C08K
3/08 20130101; C08K 2201/014 20130101 |
Class at
Publication: |
252/478 ;
523/137 |
International
Class: |
G21C 7/24 20060101
G21C007/24 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 2002 |
DE |
10258878.3 |
Aug 30, 2003 |
DE |
10340124.5 |
Claims
1. A mixture for screening radiation, comprising: a) at least 26
wt. % of gadolinium, said gadolinium being in elemental form, as a
compound, and/or as an alloy, wherein if the gadolinium is in the
form of a compound, then said compound is gadolinium (III) oxide
(Gd.sub.2O.sub.3); b) at least 10 wt. % of one or more elements
chosen, independently of each other, from the group consisting of
indium, tin, molybdenum, niobium, tantalum, zirconium and tungsten,
wherein the one or more elements are in elemental form, as a
compound, and/or as an alloy and wherein the concentration of
tungsten, it tungsten is present, is at least 10 wt. % with respect
to the total amount of the mixture.
2. The mixture according to claim 1, further comprising: c) 0 to 64
wt. % of one or more further elements chosen, independently of each
other, from the group consisting of bismuth, lanthanum, cerium,
praseodymium, neodymium, promethium, samarium, europium, terbium,
dysprosium, holmium, erbium, thulium, ytterbium and lutetium,
wherein the one or more further elements are in elemental form, as
a compound, and/or as an alloy.
3. The mixture according to claim 1, wherein a maximum of 50 wt. %
of tin, with respect to the total amount of the mixture is
present.
4. The mixture according to claim 1, wherein the one or more
elements of component b) have a complementary radiation attenuating
characteristic in the range 10 to 600 keV.
5. The mixture according to claim 1 comprising at least 35 wt. % of
gadolinium and at least 20 wt. % of tungsten.
6. The mixture according to claim 1 having a specific density in
the range of 4.0 to 13.0 g/cm.sup.3.
7. The mixture according to claim 1, wherein the mixture comprises
particles having an average particle diameter in the range 0.1 to
200 .mu.m.
8. The mixture according to claim 2, wherein the one or more
elements of b) and c) are in the form of alloys and/or compounds
chosen, independently of each other, from the group consisting of
oxides, carbonates, sulfates, halides, hydroxide, tungstates,
carbides and sulfides.
9. A process for preparing the mixture according claim 1,
comprising the steps of: drying components a), b) and c) in a
temperature range of 20 to 500.degree. C.; and screening and mixing
components a), b) and c) for 5 minutes to 24 hours.
10. (canceled)
11. A substance for screening radiation comprising: a) the mixture
according to claim 1; and b) at least one polymer.
12. The substance according to claim 11, further comprising one or
more additive.
13. The substance according to claim 11, wherein the polymer is
chosen from the group consisting of rubbers, thermoplastic
materials, polyurethanes, and mixtures thereof.
14. The substance according to claim 11, wherein the degree of
filling is less than 80 wt. %.
15. A substance for screening radiation comprising: a) 5 to 85 wt.
% of rubber, thermoplastic material or polyurethane, b) 10 to 80
wt. % of the mixture according to claim 1, and c) 5 to 20 wt. % of
other additives.
16. A process for preparing the substance according to claim 11,
comprising reacting the polymer with the mixture.
17. The process according to claim 16, wherein the polymer is a
rubber and wherein the reacting step comprises compounded the
rubber with the mixture.
18. The process according to claim 16, wherein the polymer is a
thermoplastic material and wherein the polymer is mixed with the
mixture.
19. The process according to claim 16, wherein the polymer is
polyurethane and the starting materials for the polyurethane are
mixed directly with the mixture and then polymerized.
20. A product comprising the substance according to claim 11.
Description
FIELD OF THE INVENTION
[0001] The present invention provides a mixture containing a) at
least 26 wt. % of gadolinium and b) one or more elements, alloys
and/or compounds of the group consisting of barium, indium, tin,
lanthanum, molybdenum, niobium, tantalum, zirconium, tungsten or
mixture thereof, a process for the preparation of this mixture, use
of the mixture as radiation protection, use of the mixture to
prepare polymeric radiation protection substances, a process for
preparing radiation-shielding rubbers, thermoplastic materials and
polyurethanes, a process for preparing products from the polymeric
radiation protection substances and products made from these
polymeric radiation protection substances.
BACKGROUND OF THE INVENTION
[0002] Humans are increasingly subjected to ionizing radiation from
a number of sources. The radiation occurs in the form of
high-energy electromagnetic radiation, such as X-ray or
gamma-radiation. It cannot be detected directly by humans.
Depending on the type and duration of exposure to radiation,
however, one's health can be damaged.
[0003] The effects of such energy-rich radiation can occur
intentionally, e.g. in the medical application of ionizing rays
during diagnostic or therapeutic X-ray treatment or in nuclear
medicine, in non-destructive materials testing, in radiometry or in
special measuring techniques using devices which contain
radioactive substances, or unintentionally, e.g. when operating
defective radiation emitters such as acceleration units, electron
microscopes, electronic welding plant, electron tubes or monitors.
When operating X-ray devices or other radiation emitting
instruments, the unintended effects of radiation on the operator or
third parties may occur. Therefore many precautions are applied to
protect the operator or third parties from this radiation. In many
cases it is then not possible to operate the devices mentioned
above, or only when third parties are not present. In many cases
also, complete separation of the operating staff from the source of
radiation is not possible, and also not practicable, because the
operator can only operate the equipment in the immediate vicinity
of the equipment and the source of radiation. This applies in
particular for the medical use of X-rays in X-ray diagnostics and
X-ray therapy when structural radiation protective measures have to
be used on the apparatus and personal protection equipment has to
be used in order to screen the operating staff and/or the patients
from the radiation, with the exception of areas where the radiation
is actually required.
[0004] Typical radiation protection materials contain flat
materials, in particular metallic lead or lead compounds or lead
blends. Lead and its compounds are frequently used to protect
against X-radiation and gamma-radiation. Lead has the advantage
that it is available at low cost, has a high density and also has a
high atomic number. It is, therefore, a good absorber of ionizing
radiation, e.g. X-radiation which is produced with accelerating
potentials of 40 to 300 kV. The disadvantage of lead is that, due
to the photoelectric effect, the degree of attenuation of lead is
relatively small at low energies of the ionizing radiation. Also,
lead has questionable toxicological properties. On top of that,
there is the great weight of lead-containing protective
equipment.
[0005] Thus, there is a great need for materials which exhibit
similarly effective screening properties with regard to ionizing
radiation as those of lead but which are substantially lighter,
more environmentally friendly and more toxicologically acceptable
than lead.
[0006] JP 58-053828 (K. Yamamoto) describes an elastic rubber-like
foam material based on polychloroprene rubber which contains large
amounts (80-87.3 wt. %) of metal compounds, e.g. lead oxide.
[0007] JP-57-141430 discloses a lead-containing foamed material
which consists of natural rubber or synthetic rubber and contains
lead compounds at the rate of 300 or more parts by weight per 100
parts by weight of the base material.
[0008] CA-A 815 609 describes a flexible material which consists of
a braided base layer and a lead-containing elastomer layer, at
least one surface of which is glued to the base layer. The base
layer contains lead particles with a size of <200 mesh. The lead
makes up at least 65 wt. % of the total weight of the material. The
preferred elastomer material is neoprene (polychloroprene).
[0009] JP 61-228051 discloses compositions of ethylene/vinyl
acetate and/or ethylene/ethyl acrylate copolymers which contain 5
to 50 parts of antimony oxide and 5 to 100 parts of barium sulfate
per 100 parts of polymer as cable casing. The disadvantage of this
composition is the high proportion of antimony oxide which is
classified as a carcinogenic compound.
[0010] Compositions of metallic lead in polyvinylchloride for the
absorption of X-radiation are described in GB-A 1 603 654 and GB-A
1 603 655.
[0011] JP 59-126296 describes a coated composition for screening
against radiation, which contains lead or lead compounds in a
copolymer and is applied to plasticized polyvinylchloride.
[0012] A flexible material for screening against radiation,
consisting of an elastomer matrix which contains a homogeneous
distribution of filler particles, is described in GB-A 1 122 786.
The filler is formed from a mixture of ionizing radiation absorbing
metal and at least one other metal. Lead and lead/antimony alloys
are used in this case.
[0013] GB-A 954 593 describes screenings against ionizing radiation
which are presented in the form of lead coated fabrics which have
been immersed in mercury and thereby form lead amalgams, and thus
improve the flexibility of the coated fabric.
[0014] Radiation screening materials which also contain a
lead-containing methacrylate plastics material are disclosed in
JP-2360/1960, JP-9994/1978, JP-9995/1978, JP-9996/1978 and
JP-63310/1978.
[0015] EP-A 371 699 discloses radiation screening materials which,
in a preferred embodiment, are an inorganic mixture of lead,
actinium, bismuth, gold, mercury, polonium, thallium, thorium,
uranium, iridium, osmium, platinum, rhenium, tantalum, tungsten,
bromine, molybdenum, rhodium, strontium or zirconium and inter alia
cerium or lanthanum. 70 to 93 wt. %, or preferably in fact 70 to 90
wt. % of the mixture is used in copolymers of ethylene and alkyl
acrylate, alkyl methacrylate, glycidyl methacrylate, acrylic acid,
methacrylic acid. In the preferred embodiment, 5 to 10 wt. % of
plasticizer is also added.
[0016] U.S. Pat. No. 4,563,494 describes lanthanoid compounds which
can be used in polyacrylates, polymethacrylates, polystyrene and
copolymers thereof in amounts of 0.001 to 10 wt. %. In that
document it is expressly pointed out that complete screening
against X-ray or gamma radiation is possible only in combination
with lead compounds (column 5; lines 57 to 61).
[0017] In both DE-A 199 55 192 and EP-A 0 371 699 powdered metals
with high atomic numbers are referred to as X-radiation absorbing
fillers in elastomers, wherein high proportions of metallic tin of
50-100 wt. % are cited in particular. The use of at least 26 wt. %
of gadolinium from gadolinium oxide is not disclosed.
[0018] GB-A 943 714 describes compositions for preparing a material
which screens against X-radiation and which consists of a silicone
elastomer with powdered tungsten as an additive.
[0019] In particular in the region of high-energy X-radiation of 90
kV to 150 kV accelerating potential, the materials provided in DE-A
199 55 192 and GB-A 943 714 do not offer any weight advantage, for
the same screening properties, over lead.
[0020] Thus, in all the known processes, either lead or antimony or
their compounds in high concentration, or ecologically unacceptable
substances such as mercury, polonium or uranium and/or substance
mixtures with high basic proportions of metal such as e.g.
antimony, are used. Often, the radiation protection substances used
in the known processes do not adequately screen against high-energy
X-radiation in the region of 90 to 150 kV accelerating
potential.
[0021] The object of the present invention is to provide, as
compared with the prior art and the still preferably used
lead-containing materials, lighter, more toxicologically
acceptable, completely lead-free mixtures which screen against
ionizing radiation, such as e.g. X-radiation or gamma radiation,
better than lead.
SUMMARY OF THE INVENTION
[0022] The present invention relates to a mixture containing [0023]
a) at least 26 wt. % of gadolinium as the element and/or gadolinium
compounds and/or gadolinium alloys, [0024] b) at least 10 wt. % of
one or more elements and/or alloys and/or compounds of these
elements chosen from the group consisting of barium, indium, tin,
molybdenum, niobium, tantalum, zirconium and tungsten, wherein the
concentration of tungsten, if tungsten is present, is at least 10
wt. % with respect to the total amount of mixture.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The mixture can also contain 0 to 64 wt. % of a component c)
which contains one or more elements and/or alloys and/or compounds
of these elements chosen, from the group consisting of bismuth,
lanthanum, cerium, praseodymium, neodymium, promethium, samarium,
europium, terbium, dysprosium, holmium, erbium, thulium, ytterbium
and lutetium.
[0026] The mixture according to the present invention can contain
at most 50 wt. % of tin.
[0027] The elements and/or alloys and/or compounds of component b)
in the mixture according to the present invention can exhibit a
complementary radiation attenuating characteristic in the region of
10 to 600 keV.
[0028] The mixture according to the present invention can contain
at least 35 wt. % of gadolinium and at least 20 wt. % of
tungsten.
[0029] The specific density of the mixture according to the present
invention can be 4.0 to 13.0 g/cm.sup.3.
[0030] The particles in the mixture according to the present
invention can have an average particle diameter in the range 0.1 to
200 .mu.m.
[0031] Components b) and c) in the mixture according to the present
invention can be chosen, from the group consisting of oxides,
carbonates, sulfates, halides, hydroxides, tungstates, carbides and
sulfides.
[0032] The present invention also provides a process for preparing
the mixture according to the present invention, wherein the
components of the mixture are dried in the temperature range 20 to
500.degree. C., then screened and then mixed for in the region of 5
minutes to 24 hours.
[0033] The present invention also provides use of the mixture
according to the present invention as radiation protection.
[0034] The mixture according to the present invention can be used
to prepare polymeric radiation protection substances.
[0035] The present invention also provides a polymeric radiation
protection substance which contains the mixture according to the
present invention.
[0036] The polymeric radiation protection substance which contains
the mixture according to the present invention can also contain
other additives.
[0037] The polymer in the polymeric radiation protection which
contains the mixture according to the present invention can be
chosen from the group consisting of rubbers, thermoplastic
materials and polyurethanes.
[0038] The degree of filling of the polymeric radiation protection
substance which contains the mixture according to the present
invention can be less than 80 wt. %.
[0039] The polymeric radiation protection substance which contains
the mixture according to the present invention contains [0040] a) 5
to 85 wt. % of rubber, thermoplastic material or polyurethane and
[0041] b) 10 to 80 wt. % of the mixture described above and [0042]
c) 5 to 20 wt. % of other additives.
[0043] The present invention also provides a process for preparing
a polymeric radiation protection substance which contains the
mixture according to the present invention, wherein the polymer is
reacted with the mixture according to the present invention.
[0044] The process for preparing a polymeric radiation protection
substance which contains the mixture according to the present
invention includes, for example, compounding together a polymer,
such as rubber, with the mixture according to the present
invention.
[0045] The process for preparing a polymeric radiation protection
substance which contains the mixture according to the invention,
also includes, for example, mixing a polymer, such as a
thermoplastic material, with the mixture according to the present
invention.
[0046] The process for preparing a polymeric radiation protection
substance which contains the mixture according to the invention
also includes a process in which the polymer is polyurethane and
the starting materials for the polyurethane are mixed directly with
the mixture according to the invention and then polymerized.
[0047] The present invention also provides a process for producing
a product, wherein the polymeric radiation protection substance
which contains the mixture according to the present invention is
used.
[0048] The present invention also provides a product obtainable by
using the process to produce a product in which the polymeric
radiation protection substance which contains the mixture according
to the present invention is used.
[0049] The mixture according to the present invention contains at
least 26 wt. % of gadolinium as the element and/or derived from
compounds and/or alloys. The mixture according to the present
invention can contain a proportion of gadolinium in the range 35 to
55 wt. %.
[0050] Component b) in the mixture according to the present
invention contains at least 10 wt. % of one or more elements,
alloys and/or compounds of these elements chosen, independently of
each other, from the group consisting of barium, indium, tin,
molybdenum, niobium, tantalum, zirconium and tungsten, wherein the
concentration of tungsten, if tungsten is present, is at least 10
wt. % with respect to the total amount of mixture. Elements, alloys
and/or compounds which have a radiation attenuating characteristic
in the range 10 to 300 keV are useful. For example, barium, tin,
tungsten and molybdenum. The proportion of component b) in the
mixture according to the present invention is in the range 10 to 74
wt. %, or for example in the range 20 to 60 wt. %, or further for
example, in the range 25 to 50 wt. %. The proportion of tin can be
less than 50 wt. %, with respect to the weight of the entire
mixture.
[0051] Component c) in the mixture according to the present
invention contains one or more elements, alloys and/or compounds of
these elements chosen, independently of each other, from the group
consisting of bismuth, lanthanum, cerium, praseodymium, neodymium,
promethium, samarium, europium, terbium, dysprosium, holmium,
erbium, thulium, ytterbium and lutetium. Or for example, the
elements, alloys and/or compounds of bismuth, lanthanum, cerium,
praseodymium, neodymium, samarium and europium are used. The
proportion of component c) in the mixture according to the present
invention is in the range 0 to 64 wt. %, or, for example, in the
range 20 to 50 wt. %, or further for example, in the range 25 to 40
wt. %.
[0052] Component a) can be used in the form of its compounds, such
as oxides.
[0053] Component c) can be used in the form of its compounds.
Useful compounds for components b) and c) include oxides,
carbonates, sulfates, hydroxides, tungstates, carbides, sulfides or
halides of the elements mentioned. Or for example compounds for
components b) and c) include oxides, sulfates and tungstates. Or,
for example, compounds barium sulfate, indium oxide and tin oxide
or the metals tin, molybdenum, niobium, tantalum, zirconium and
tungsten are used for component b) and the compounds bismuth oxide,
lanthanum oxide, cerium oxide, praseodymium oxide, promethium
oxide, samarium oxide, europium oxide, terbium oxide, dysprosium
oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide
and lutetium oxide are used for component c).
[0054] To prepare the mixture according to the present invention,
the individual constituents of component a) and of component b) are
dried at temperatures in the range 30 to 500.degree. C. Then the
individual constituents of the two components a) and b) are
screened with a sieve in the range 3 to 125 .mu.m mesh size. The
constituents of components a) and b) obtained are then mixed for 5
minutes to 24 hours in mixers which are well-known to a person
skilled in the art, such as propeller, turbo, blade, trough,
planetary, attrition, screw, roller, centrifugal, countercurrent,
jet, drum, conical, tumble, rotary, cooling, vacuum, continuous
flow, gravity, fluid-bed and pneumatic mixers. Tumble mixers can be
used. The specific density of the mixture according to the present
invention is in the range 4.0 to 13.0 g/cm.sup.3, or in the range
6.0 to 10 g/cm.sup.3. A corresponding procedure is used for a
mixture which also contains component c).
[0055] In addition, other additives may also be present in the
mixture according to the present invention. Other additives are
understood to be those well-known to a person skilled in the art
such as UV absorbers, plasticizers, waxes, mould release agents,
antioxidants, heat stabilizers, pigments, inorganic extenders, dyes
as well as other compounds which screen against radiation. For
example, additives include plasticizers such as ethers,
ether-thioethers, esters with thioether groups, sulfonates,
adipates, (poly)phthalates, citrates, phosphates. These additives
can be present in the mixture according to the invention in
proportions of 0 to 30 wt. %, or, for example, 10 to 20 wt. %, or
further, for example, 5 to 15 wt. %.
[0056] The mixture according to the present invention is used as a
screening material (radiation protection) against X-ray and gamma
radiation. The mixture according to the present invention is
preferably used for absorptions in the range 10 to 600 keV, or, 80
to 400 keV. For example, the types of constituents in the mixture
according to the present invention and their ratio to each other
provides a weight reduction of 50% of the absorption material being
used as compared with a single absorption element such as lead; or
else, for the same weight as of lead of absorption elements, alloys
or compounds within the mixture according to the present invention,
a certain composition of the mixture according to the present
invention can produce about a 150% higher absorption than the lead
equivalent. The lead equivalent is understood to be the screening
capacity possessed by lead with the same weight as the mixture
being assessed. For component b), 15 to 60 wt. %, or, for example,
25 to 50 wt. % of tungsten, tin or tin oxide or mixtures thereof
and for component c), 20 to 50 wt. %, or, for example, 25 to 40 wt.
% of bismuth oxide, lanthanum oxide, cerium oxide, praseodymium
oxide, neodymium oxide, samarium oxide, europium oxide and
gadolinium oxide or mixtures thereof, are used. The tin content can
be less than 50 wt. % and the tungsten content can be greater than
10 wt. %.
[0057] The mixture according to the present invention can also be
introduced as radiation protection into all polymers known to a
person skilled in the art. Useful polymers include all the rubbers,
thermoplastic materials and polyurethanes known to a person skilled
in the art.
[0058] The mixture according to the present invention should be
compatible with the plastics component because physical
interactions between the plastics component and the mixture
according to the present invention may be produced which can have
an effect on the properties of the polymeric radiation protection
substance being produced. Thus, for example, oxides can be
dispersed better than the corresponding metals in the polymeric
radiation protection substance so the mixture according to the
present invention can be distributed more uniformly in the
polymeric radiation protection substance matrix. Better mechanical
properties such as breaking strength or tear propagation resistance
arise there from. The constituents of the mixture according to the
present invention are used in powder form and are distributed
homogeneously in the polymer.
[0059] When blending the mixture according to the present invention
with the polymer or when dispersing in the polymer-forming raw
materials, average particle diameters of 0.1 to 200 Fun, or, for
example, 0.5 to 100 .mu.m, are used.
[0060] The proportion of the mixture according to the present
invention in the polymeric radiation protection substance depends
on the energy of the radiation being screened and also on the
compatibility of the mixture with the polymer. The polymeric
radiation protection substance contains 10 to 90 wt. %, or, for
example, 10 to 80 wt. %, or, further, for example, 15 to 70 wt. %
of the mixture according to the present invention.
[0061] The mixture according to the present invention can either be
added to the starting materials for the polymers before
polymerization or else be incorporated later into the polymer. The
mixture according to the present invention can be incorporated into
rubbers and thermoplastic materials after polymerization, whereas
when preparing the polymeric radiation protection substance which
uses polyurethane as the polymer, the mixture according to the
invention can be added to the starting materials just before
polymerization. Incorporation of the mixture according to the
present invention into the polymer after polymerization is
performed by processing possibilities which are well-known to a
person skilled in the art such as compounding, melting, cold
pressing, hot pressing, calandering, injection molding, extruding,
sintering or transfer molding. The polymeric radiation protection
substances containing the mixture according to the present
invention can be prepared by adding the components to the
melt-compounding or comparable process, wherein the process used
depends to some extent on the polymeric radiation protection
substance being prepared and/or on the melt characteristics of the
polymer. Examples of compounding equipment which can be used are
twin roller mills, Banbury mixers, Farrell mixers, Buss
compounders, Gelimat intensive mixers and comparable mixers. The
mixture according to the present invention can also be prepared in
a Banbury twin rotor mixer, when all the components are placed in
the mixer together. However, it may also be useful first to prepare
a concentrate or master batch of the mixture according to the
present invention in the polymer in order to prepare the
combination in the concentrates in a high viscosity mixer. The
polymeric radiation protection substance obtained in this way can
then be processed further and be shaped to give sheets by means of
extrusion, calandering, compression forming or other processing
possibilities known to a person skilled in the art.
[0062] Therefore, the processes for preparing polymeric radiation
protection substances which contain the mixture according to the
present invention are not restricted, so a variety of processes can
be used. Therefore, a process in which the mixture according to the
present invention is blended with the polymer or a process in which
the mixture according to the present invention is dispersed in the
polymer-forming raw material and this polymer-forming raw material
is polymerized can be used or a process is performed in which the
mixture according to the present invention is mixed with or
suspended in a solvent in order to have an effect on the
polymerization procedure.
[0063] The mixture according to the present invention is especially
useful as a screening material against X-ray and gamma radiation.
This mixture according to the present invention can be used to
produce polymeric radiation protection substances from which
aprons, housings, surgical gloves, partitions and other items
suitable for screening against ionizing radiation are used. Such
properties are especially important for structural radiation
protective modifications to apparatus or personal radiation
equipment against ionizing radiation in which better protection is
required or the same protection is required, but at the same time
involving less weight for the protective devices, as compared with
traditional materials, and offering important advantages to the
user, for example, with regard to the radiation protection and/or
wearer comfort of protective clothing. The mixture according to the
present invention has a higher radiation protection (attenuation
factors) than lead against X-ray or gamma radiation with energies
greater than 10 keV, with respect to the weight of lead or lead
compound used. Thus, in comparison to lead, the same protection is
produced with less weight or greater protection is produced with
the same weight, because more of the radiation is absorbed. The
improved attenuation factor refers to a specific X-ray or gamma
energy (wavelength) and can be optimized for each individual energy
spectrum by a choice of mixture components. The mixture according
to the present invention attenuates more strongly and therefore
provides protection over a wider range of the (ionizing)
electromagnetic spectrum than metallic lead, lead compounds or
other absorbent materials made from a single element.
[0064] The mixture according to the present invention can be
incorporated into rubbers by processes known to a person skilled in
the art. The expression rubber is understood to include all
elastomers known to a person skilled in the art. Natural rubber,
polychloroprene, acrylonitrile rubber, ethylene/vinylacetate
copolymers, hydrogenated acrylonitrile rubber, styrene/butadiene
rubber, ethylene/propylene rubber or ethylene/propylene terpolymers
(EPDM), isobutylene/isoprene rubber or halogenated
isopropylene/isoprene rubber, silicone rubber or their blends with
each other or with thermoplastic polymers such as polyethylene,
polypropylene, polyvinylchloride can be used used. For example,
Ethylene/vinylacetate copolymers (Levapren.RTM.), polychloroprene
(Baypren.RTM.), ethylene/propylene terpolymers, natural rubber can
be used. The rubber may contain additives which are conventionally
used by a person skilled in the art. Conventional additives are
understood to include cross-linking systems such as 2 to 5 parts by
wt. of zinc oxide, 2 to 4 parts by wt. of
3-methyl-thiazolidine-thione-2 and 0.5 to 1.5 parts by wt. of zinc
dibenzyldithiocarbanate for polychloroprene rubbers or 4 to 7 parts
by wt. of .alpha.,.alpha.'-bis-(t-butylperoxy)-diisopropylbenzene
in combination with 0 to 4 parts by wt., preferably 2 to 4 parts by
wt. of activators such as triallyl cyanurate, triallyl isocyanurate
or N,N'-m-phenylene dimaleic imide for ethylene/vinylacetate
copolymers or 0.5 to 2.5 parts by wt. of benzothiazyl-2-cyclohexyl
sulfenamide, 0 to 1.5 parts by wt. of tetramethylthiuram disulfide
or 0 to 1.5 parts by wt. of dimethyldiphenylthiuram disulfide and 1
to 1.3 parts by wt. of sulfur for natural rubber. Anti-ageing
agents are understood to be materials such as
N-isopropyl-N'-phenyl-p-phenylenediamine,
N-(1,3-dimethylbutyl)-1-N'-phenyl-p-phenylene-diamine,
N,N'-bis-(1,4-dimethylpentyl)-p-phenylenediamine,
2,2'-methylene-bis-(4-methyl-6-tert-butylphenol),
N,N'-diphenyl-p-phenylenediamine, styrenated diphenylamine,
polymerized 2,2,4-trimethyl-1,2-dihydroquinoline or styrenated
phenol in concentrations of 1 to 3 parts by wt. Inactive and active
fillers are understood to be additives such as carbon blacks,
silicas with various activities and with various surface areas or
chalk, kaolin or clay at 0 to 60 parts by wt., inorganic dyes such
as titanium dioxide or iron oxide at 1 to 5 parts by wt.,
processing aids such as fatty acids, fatty esters, fatty alcohols
in concentrations of 0 to 5 parts by wt., stabilizers such as
2,2'-methylene-bis-(4-methyl-6-tert-butylphenol) at 0.5 to 3 parts
by wt. In general, accelerators from the class of sulfenamides such
as N-cyclohexylbenzothiazyl sulfenamide (CBS),
N-tert.-butyl-2-benzothiazyl sulfenamide (TBBS),
benzothiazyl-2-sulfenomorpholides (MBS),
N,N-dicylcohexylbenzothiazol-2-sulfenamide (DCBS), mercapto
accelerators such as 2-mercaptobenzothiazole (MBT), zinc
2-mercaptobenzothiazole (ZMBT), benzothiazyl disulfide (MBTS),
thiurams such as tetramethylthiuram disulfide (TMTD),
dithiocarbamates such as zinc diethyldithiocarbamate (ZDEC), zinc
ethylphenyldithiocarbamate (ZEPC), zinc dibenzyldithiocarbamate
(ZBEC) or guanidines such as diphenylguanidine (DPG) can be used in
combination with sulfur. Peroxide cross-linking agents which can be
used are substances such as
2,5-dimethyl-2,5-di-(tert-butylperoxy)-hexene-3,2,5-dimethyl-2,5-di-(tert-
-butylperoxy)-hexane, di-(tertbutylperoxyisopropyl)-benzene,
tert-butylcumyl peroxide, dicumyl peroxide,
butyl-4,4-di-(tert-butylperoxy)-valerate,
1,1-di-(tert-butylperoxy)-3,3,5-trimethylcyclohexane, in
concentrations of 2 to 7 parts by wt., are use alone or in
combination with 2 to 4 parts by wt. of activators such as triallyl
cyanurate, triallyl isocyanurate, N,N'-m-phenylenedimaleic imide or
trimethylolpropane trimethacrylate.
[0065] The mixture according to the present invention, in an amount
up to 6 times the weight of the polymer material, can be added to
the pre-masticated rubber on/in a mixer (compounder/rollers) within
10 to 15 minutes, followed by other conventional fillers,
plasticizers, processing aids, the cross-linking system and the
stabilizers, these being added within 3 to 5 minutes.
[0066] The further processing of the mixture according to the
present invention can be performed using processing methods, such
as calandering, known to a person skilled in the art. The
cross-linking of the polymer matrix which is required is also
performed using methods known to a person skilled in the art, such
as vulcanization after the shaping procedure.
[0067] Suitable thermoplastic materials include all thermoplastic
materials known to a person skilled in the art. Polyalkylene
terephthalates, aromatic polyesters, polyamides, polycarbonate,
thermoplastic polyurethanes (TPU), polyacrylate, polymethacrylate,
acrylonitrile/butadiene/styrene (ABS) graft copolymers, polyolefins
such as polyethylene or polypropylene, polystyrene,
polyvinylchloride, polyoxymethylene, polyimide, polyethers and
polyetherketones, which may be used individually or as a blend of
different polymers, can be used. Polyamide-6s such as Durethen.RTM.
B315, ABS plastics such as Lustran.RTM. ABS M 203 FC,
polycarbonates such as Makrolon.RTM. Rx 1805 or Makrolon.RTM. 2808,
polybutylene terephthalates such as Pocan.RTM. B 1300 or
thermoplastic polyurethanes such as Desmopan.RTM. 385 or
Desmopan.RTM. 786 can be used.
[0068] Polyamides can be synthesized by a variety of processes and
from very different building blocks and in special cases of
application can be incorporated alone or in combination with
processing aids, stabilizers, polymeric alloying partners such as
elastomers or also reinforcing materials such as mineral fillers or
glass fibers to give materials with specific adjusted combinations
of properties. Blends with a proportion of other polymers such as
polyethylene, polypropylene or ABS are also suitable. The
properties of polyamides, such as with regard to the impact
resistance of reinforced polyamides, can be improved by the
addition of elastomers. The number of combinations possible enables
a very large number of products with very different properties,
such as low temperature impact resistance or ease of flow.
[0069] A number of procedures are known for preparing polyamides,
wherein, depending on the end product required, different monomeric
building blocks, different chain transfer agents to adjust the
molecular weight striven for, or else monomers with reactive groups
such as amino, hydroxy, carboxy, carboxylate, carboxylic chloride
and/or carboxylic anhydride groups for subsequent planned post
treatments, are used.
[0070] The technically relevant processes for preparing polyamides
are based on polycondensation in the melt. In this context, the
hydrolytic polymerization of lactams is also understood to be a
polycondensation process.
[0071] Preferred polyamides are partly crystalline polyamides which
can be prepared starting from diamines and dicarboxylic acids
and/or lactams with at least 5 ring-members or the corresponding
amino acids.
[0072] Suitable starting products include aliphatic and/or aromatic
dicarboxylic acids such as adipic acid, 2,2,4- and
2,4,4-trimethyladipic acid, azelaic acid, sebacic acid, isophthalic
acid, terephthalic acid, aliphatic and/or aromatic diamines such as
hexamethylenediamine, 1,9-nonanediamine, 2,2,4- and
2,4,4-trimethyl-hexamethylenediamine, the isomeric
diaminodicyclohexylmethanes, diaminodicyclohexylpropane,
bis-aminomethylcyclohexane, phenylenediamine, xylylenediamine,
aminocarboxylic acids such as aminocaproic acid or the
corresponding lactams. Copolyamides made from several of the
monomers mentioned are included.
[0073] Caprolactams are useful, as is, .epsilon.-caprolactam.
[0074] Furthermore, compounds which are based mostly on polyamide-6
(PA6), polyamide 6,6 (PA66) and other aliphatic and/or aromatic
polyamides and/or copolyamides in which 3 to 11 methylene groups
are present on a polyamide group in the polymer chain are
especially suitable.
[0075] The polyamides used may also be used as a mixture with other
polyamides and/or further polymers.
[0076] In addition, the polyamide molding compositions can also
contain fire retardants such as phosphorus compounds, organic
halogen compounds, nitrogen compounds and/or magnesium hydroxide,
stabilizers, processing aids such as lubricants, nucleating agents,
stabilizers, impact resistance modifiers such as rubbers or
polyolefins, provided that these do not have too strong an
absorption in the region of the wavelengths of the laser used.
[0077] Suitable fibrous reinforcing agents, apart from glass
fibers, are aramide fibers, mineral fibers and whiskers. Suitable
mineral fillers which may be mentioned are, for example, calcium
carbonate, dolomite, calcium sulfate, mica, fluorinated mica,
wollastonite, talcum and kaolin. To improve the mechanical
properties, the fibrous reinforcing agents and mineral fillers can
be surface-treated.
[0078] Addition of the energy-absorbing inorganic additives and
fillers can be performed before, during or after polymerization of
the monomers to give a polyamide. If addition of the fillers takes
place after polymerization, this can be performed by addition to
the polyamide melt in an extruder. If addition of the fillers takes
place before or during polymerization, then polymerization can
include phases in which processing takes place in the presence of 1
to 50 wt. % of water.
[0079] The fillers may be present during addition as particles with
the particle sizes which are ultimately present in the molding
composition. Alternatively, the fillers can be added in the form of
precursors from which the particles which are ultimately present in
the molding composition are produced only during the course of
addition or incorporation.
[0080] Suitable fire-proofing or fire-retardant agents include, for
example, red phosphorus, described in DE-A-3 713 746, page 5, line
40 to page 6, line 1, and EP-A-299 444, page 14, lines 11 to 12,
brominated diphenyls or diphenyl ethers in combination with
antimony trioxide and chlorinated cycloaliphatic hydrocarbons
(Dechlorane.RTM. plus from Occidental Chemical Co., with a density
of 1.8 g/cm.sup.3 and a melting point (with decomposition) of
350.degree. C.), brominated styrene oligomers described in DE-A-2
703 419, column 4, line 8 to column 3, line 68 and o-, m- and/or
p-brominated polystyrenes (e.g. Pyro-Chek 68.RTM. from Albemarle
Corp., with a specific density of 2.1 g/cm.sup.3, a bromine content
of at least 66 wt. %, a T.sub.g of 195.degree. C., and a melting
point of 265.degree. C.).
[0081] Zinc compounds or iron oxides, for example, are used as
synergists to the halogen compounds mentioned above.
[0082] As other alternatives, melamine salts have proven especially
appropriate as flame retardants, such as for non-reinforced
polyamides.
[0083] In addition, magnesium hydroxide has long been recognized as
a flame retardant for polyamide.
[0084] The polyamide molding compositions may contain, apart from
glass fibers, additional rubber-elastic polymers, which are often
also called impact resistance modifiers, elastomers or rubbers.
[0085] Partially aromatic polyesters can be used as thermoplastic
materials. Partially aromatic polyesters are understood to be
polyesters which contain, in addition to aromatic repeating units,
also aliphatic repeating units. The polyesters can be chosen from
the group consisting of derivatives of polyalkylidene
terephthalates, polyethylene terephthalates, polytrimethylene
terephthalates and polybutylene terephthalates. The polyesters can
also be chosen from the group consisting of derivatives of
polybutylene terephthalates.
[0086] Useful polyalkylene terephthalates are described in more
detail in the next few paragraphs.
[0087] The polyalkylene terephthalates used are reaction products
of aromatic dicarboxylic acids or their reactive derivatives such
as dimethyl esters or anhydrides and aliphatic, cycloaliphatic or
araliphatic diols and mixtures of these reaction products.
[0088] Preferred polyalkylene terephthalates can be prepared by
known methods from terephthalic acid or its reactive derivatives
and aliphatic or cycloaliphatic diols with 2 to 10 carbon atoms
(Kunststoff-Handbuch, vol. VIII, page 695 et seq.,
Karl-Hanser-Verlag, Munich, 1973).
[0089] Preferred polyalkylene terephthalates contain at least 80,
or, for example, 90 mol. %, with respect to the molar amounts of
dicarboxylic acid, of terephthalates and at least 80, or, for
example, at least 90 mol. %, with respect to the molar amount of
diol components, of ethylene glycol and/or propanediol-1,3 and/or
butanediol-1,4 groups.
[0090] Polyalkylene terephthalates useful in the present invention
can contain, in addition to terephthalates, up to 20 mol. % of
groups from other aromatic dicarboxylic acids with 8 to 14 carbon
atoms or aliphatic dicarboxylic acids with 4 to 12 carbon atoms,
such as groups from phthalic acid, isophthalic acid,
naphthaline-2,6-dicarboxylic acid, 4,4'-diphenyl-dicarboxylic acid,
succinic, adipic, sebacic or azelaic acid or cyclohexanediacetic
acid.
[0091] Polyalkylene terephthalates can contain, in addition to
ethylene glycol or propanediol-1,3 or butanediol-1,4 groups, up to
20 mol. % of other aliphatic diols with 3 to 12 carbon atoms or
cycloaliphatic diols with 6 to 21 carbon atoms, such as groups from
propanediol-1,3; 2-ethylpropanediol-1,3; neopentyl glycol,
pentane-diol-1,5; hexanediol-1,6; cyclohexanedimethanol-1,4;
3-methylpentanediol-2,4; 2-methylpentanediol-2,4;
2,2,4-trimethylpentanediol-1,3 and -1,6; 2-ethylhexanediol-1,3;
2,2-diethyl-propanediol-1,3; hexanediol-2,5;
1,4-di-(.beta.-hydroxyethoxy)-benzene,
2,2-bis-(4-hydroxycyclohexy,)-propane,
2,4-dihydroxy-1,1,3,3-tetramethyl-cyclobutane,
2,2-bis-(3-.beta.-hydroxyethoxyphenyl)-propane and
2,2-bis-(4-hydroxypropoxy-phenyl)-propane as described in DE-A 25
07 674, page 4, line 11 to page 4, line 16, DE-A 25 07 776, page 4,
line 11 to page 4, line 16, DE-A 27 15 932, page 6, line 25 to page
9, line 12.
[0092] The polyalkylene terephthalates can be branched by
incorporating relatively small amounts of 3-hydric or 4-hydric
alcohols or 3-basic or 4-basic carboxylic acids, as described in
DE-A 19 00 270, page 4, line 16 to page 5, line 4 and in US-B 3 692
744, column 2, line 31 to column 2, line 49. Examples of preferred
branching agents include trimesic acid, trimellitic acid,
trimethylolethane and-propane and pentaerythritol.
[0093] It is advisable to use not more than 1 mol. % of branching
agent, with respect to the acid component.
[0094] Polyalkylene terephthalates which have been prepared only
from terephthalic acid and its reactive derivatives such as its
dialkyl esters and ethylene glycol and/or propanediol-1,3 and/or
butanediol-1,4 (polyethylene and polybutylene terephthalate) and
mixtures of these polyalkylene terephthalates are useful.
[0095] Polyalkylene terephthalates also include copolyesters which
are prepared from at least two of the acid components mentioned
above and/or from at least two of the alcohol components mentioned
above; such, copolyesters include poly-(ethylene
glycol/butanediol-1,4)-terephthalates.
[0096] The polyalkylene terephthalates generally have an intrinsic
viscosity of about 0.4 to 1.5, or, for example, 0.5 to 1.3, each
measured in phenol/o-dichlorobenzene (1:1 parts by wt.) at
25.degree. C.
[0097] Furthermore, the partially aromatic polyesters can contain
additives such as fillers and reinforcing agents such as glass
fibers or mineral fillers, flame retardants, processing aids,
stabilizers, flow promoters, antistatic agents and other
conventional additives.
[0098] Fibrous or particulate fillers and reinforcing substances
which can be added to molding compositions according to the present
invention include glass fibers, glass beads, glass fabric, glass
mats, aramide fibers, potassium titanate fibers, natural fibers,
amorphous silica, magnesium carbonate, barium sulfate, feldspar,
mica, silicates, quartz, talcum, kaolin, wollastonite etc, which
may also be surface-treated. Useful reinforcing substances are
commercially available glass fibers. The glass fibers, which
generally have a fiber diameter between 8 and 18 .mu.m, may be
added as infinite fibers or as cut or milled glass fibers, wherein
the fibers can be provided with a suitable size system and a
bonding agent or bonding agent system based on silane.
[0099] Needle-shaped mineral fillers are also suitable. A
needle-shaped mineral filler is understood, in the context of the
present invention, to be a mineral filler with a very pronounced
needle-shaped structure. Needle-shaped wollastonite may be
mentioned as an example. The mineral can have a length/diameter
(L/D) ratio of 8:1 to 35:1, or, for example, 8:1 to 11:1. The
mineral filler may optionally be surface-treated.
[0100] The polyester molding compositions can contain 0 to 50 parts
by wt., or, for example, 0 to 40, or, further for example, 10 to 30
parts by wt. of filler and/or reinforcing substance. Polyester
molding compositions without any filler or reinforcing substance
can also be used.
[0101] Suitable flame retardants are commercially available organic
compounds or halogen compounds with synergists or commercially
available nitrogen compounds or organic/inorganic phosphorus
compounds. Mineral flame retardant additives such as magnesium
hydroxide or Ca--Mg carbonate hydrates, as described in DE-A 4 236
122, page 2, lines 46 to 50, can also be used. The following may be
mentioned by way of example as halogen-containing, for example,
brominated and chlorinated, compounds:
ethylene-1,2-bis-tetrabromophthalimide, epoxidized
tetrabromo-bisphenol-A resin, tetrabromobisphenol-A oligocarbonate,
tetrachlorobisphenol-A oligocarbonate, pentabromopolyacrylate,
brominated polystyrene. Suitable organic phosphorus compounds
include the phosphorus compounds described in WO 98/17720, page 7,
line 26 to page 11, line 11, such as triphenyl phosphate (TPP),
resorcinol-bis-(diphenyl phosphate), (RDP), including oligomers and
bisphenol-A-bis-diphenyl phosphate (BDP) including oligomers,
melamine phosphate, melamine pyrophosphate, melamine polyphosphate
and mixtures of these. Suitable nitrogen compounds include melamine
and melamine cyanurate. Suitable synergists are antimony compounds,
such as, antimony trioxide and antimony pentoxide, zinc compounds,
tin compounds such as tin stannate and borates. Carbon-producers
and tetrafluoroethylene polymers may also be added.
[0102] The partially aromatic polyesters may also contain
conventional additives such as agents to prevent thermal
decomposition, agents to prevent thermal cross-linking, agents to
prevent damage due to ultraviolet light, plasticizers, lubricants
and mould release agents, nucleating agents, and optionally other
stabilizers.
[0103] The partially aromatic molding compositions can be prepared
by blending the particular constituents in a known manner and
melt-compounding or melt-extruding at temperatures of 200.degree.
C. to 330.degree. C. in conventional units such as internal
compounders, extruders, twin-shaft screws. During the
melt-compounding or melt-extruding step, other additives such as
reinforcing substances, stabilizers, lubricants and mould release
agents, nucleating agents and other additives can be added.
[0104] Examples of oxidation inhibitors and heat stabilizers which
may be mentioned include sterically hindered phenols and/or
phosphites, hydroquinones, aromatic secondary amines such as
diphenylamine, various substituted representatives of these groups
and mixtures of these in concentrations up to 1 wt. %, with respect
to the weight of the thermoplastic molding composition.
[0105] UV stabilizers which may be mentioned, which are generally
used in amounts of up to 2 wt. % with respect to the molding
composition, are various substituted resorcinols, salicylates,
cinnamates, benzotriazoles, hydroxyphenyltriazines and
benzophenones.
[0106] Other inorganic pigments such as titanium dioxide,
ultramarine blue, iron oxide and carbon black, furthermore organic
pigments such as phthalocyanines, quinacridones, perylenes and dyes
such as nigrosin and anthraquinone can be added as coloring agents,
as well as other coloring agents as long as these do not absorb in
the region of the laser used. Otherwise they should be used only in
amounts small enough still to enable at least partial transmission
of the laser light.
[0107] Sodium phenylphospinate, aluminum oxide, silicon dioxide,
for example, and preferably talcum, can be used as nucleation
agents.
[0108] Lubricants and mould release agents, which are generally
used in amounts of up to 1 wt. %, are preferably ester waxes,
pentaerthrityl tetrastearate (PETS), long-chain fatty acids (e.g.
stearic acid or behenic acid), their salts such as Ca and/or Zn
stearate and amide derivatives such as ethylene-bis-stearylamide or
montana wax and low molecular weight polyethylene or polypropylene
waxes.
[0109] Examples of plasticizers which may be mentioned include
dioctyl phthalate, dibenzyl phthalate, butylbenzyl phthalate,
high-boiling hydrocarbons (boiling point>250.degree. C.),
N-(n-butyl)benzenesulfonamide.
[0110] The additional use of rubber-elastic polymers, which are
also known as impact resistance modifiers, elastomers or rubbers,
is useful according to the present invention.
[0111] Rubber-elastic polymers include copolymers produced from two
or more monomers such as ethylene, propylene, butadiene, isobutene,
isoprene, chloroprene, vinyl acetate, styrene, acrylonitrile and
acrylates or methacrylates with 1 to 18 carbon atoms in the alcohol
component. Useful graft copolymers include polybutadiene,
butadiene/styrene copolymers and acrylate rubbers grafted with
styrene and/or acrylonitrile and/or alkyl acrylates or alkyl
methacrylates.
[0112] These types of polymers are described in Houben-Weyl,
Methoden der organischen Chemie, vol. 14/1 (Georg-Thieme-Verlag),
Stuttgart, 1961, pages 392 to 406 and in the monograph by C. B.
Bucknall, "Toughened Plastics" (Applied Science Publishers),
London, 1977, pages 66 to 106.
[0113] Mixtures of the types of rubbers may also be used.
[0114] Suitable coloring agents include either organic or inorganic
pigments and/or dyes. Carbon black is also an optional constituent
of the pigment mixture. The pigments/dyes and/or carbon black may
optionally also be used as a batch.
[0115] Inorganic pigments which may be mentioned include:
lithopone, titanium dioxide (anatase, rutile), zinc oxide, zinc
sulfide, metal oxides such as berlin blue, chromium oxides, iron
oxides, cobalt blue, cobalt-chromium blue, cobalt-nickel grey,
manganese blue, manganese violet, molybdate orange, molybdate red,
nickel-antimony titanate, ultramarine blue as well as zirconium
silicate, zirconium-vanadium blue, zirconium-praseodymium
yellow.
[0116] Organic pigments which may be mentioned include:
anthraquinone, azo, azomethine, benzanthrone, quinacridone,
quinophthalone, dioxazine, flavanthrone, indanthrone, isoindoline,
isoindolinone, methine, perinone, perylene, phthalocyanine,
pyranthrone, pyrrolopyrrole, thioindigo pigments and metal
complexes of e.g. azo, azomethine, methine dyes or metal salts of
azo compounds.
[0117] Suitable polymer-soluble dyes include, for example,
dispersion dyes such as those of the anthraquinone series, for
example alkylamino, amino, arylamino, cyclohexylamino, hydroxy,
hydroxyamino or phenylmercapto anthraquinones as well as metal
complexes of azo dyes, such as, 1:2 chromium or cobalt complexes of
monoazo dyes as well as fluorescent dyes, for example those made
from the benzthiazole, coumarin, oxarine or thiazone series.
[0118] Polymer-soluble dyes can also be used in combination with
fillers and/or pigments, for example, with inorganic pigments such
as titanium dioxide.
[0119] According to the present invention, pigments and/or
polymer-soluble dyes can be used.
[0120] Suitable pigment additives include, for example, fatty acids
with at least 12 carbon atoms such as behenic acid or stearic acid,
their amides, salts or esters such as aluminum stearate, magnesium
stearate, zinc stearate or magnesium behenate, as well as
quaternary ammonium compounds such as
tri-(C.sub.1-C.sub.4)-alkylbenzylammonium salts, waxes such as
polyethylene wax, resin acids such as abietic acid, colophonium
soaps, hydrogenated or dimerised colophonium,
C.sub.12-C.sub.18-paraffindisulfonic acids or alkylphenols.
[0121] Also suitable are metal-containing pigments such as
inorganic pigments and metal complexes of azo, azomethine or
methine dyes, azomethine, quinacridone, dioxazine, isoindoline,
isoindolinone, perylene, phthalocyanine, pyrrolopyrrole, and
thioindigo coloring agents and bismuth vanadate.
[0122] Thermoplastic materials can be homopolymers or copolymers of
ethylenically unsaturated monomers and polycondensates of
bifunctional reactive compounds. Mixtures of different polymers are
also suitable.
[0123] Polymers which do not contain any crystalline regions in the
processed state, and thus are completely amorphous, are also
suitable.
[0124] In this case, "amorphous" is understood to be the polymer
state described in L. H. Sperling: Introduction to Physical Polymer
Science, J. Wiley & Sons, 1986, page 123.
[0125] Examples of homopolymers and copolymers of one or more
ethylenically unsaturated monomers ("vinyl polymers") are those of
the monomers ethylene, propylene, vinyl acetate, styrene,
.alpha.-methylstyrene, o- and/or m- and/or p-substituted styrenes,
acrylonitrile, methacrylonitrile, methyl methacrylate, maleic
anhydride, N-substituted maleic imides, chloroprene, butadiene-1,3,
isoprene, C.sub.1-18-alkyl acrylates and methacrylates.
[0126] For example, the following are suitable: [0127] rubber-free
vinyl polymers (A.1) [0128] rubber-containing vinyl polymers, e.g.
graft polymers of vinyl monomers on a rubber (A.2) [0129] mixtures
of rubber-free (A.1) and rubber-containing (A.2) vinyl
polymers.
[0130] Useful vinyl polymers A.1 include copolymers of on the one
hand styrene, .alpha.-methyl styrene, ortho- and/or meta- and/or
para-substituted styrene or mixtures of these monomers (A.1.1) and
on the other hand acrylonitrile, methacrylonitrile, methyl
methacrylate, maleic anhydride, N-substituted maleic imide or
mixtures of these monomers (A.1.2).
[0131] These copolymers can contain 50 to 98 wt. % of A.1.1 and 50
to 2 wt. % of A.1.2.
[0132] Useful copolymers A.1 include styrene, acrylonitrile and
optionally methyl methacrylate, of .alpha.-methylstyrene,
acrylonitrile and optionally methyl methacrylate or of styrene,
.alpha.-methylstyrene, acrylonitrile and optionally methyl
methacrylate.
[0133] For example, styrene/acrylonitrile copolymers, which can be
prepared by radical polymerization, for example, by emulsion,
suspension, solution or bulk polymerization are useful as A.1.
Copolymers A.1 can have molecular weights Mw (weight average,
determined by light scattering or sedimentation) of 15 000 to 200
000.
[0134] Further pcopolymers A.1 include randomly structured
copolymers of styrene and maleic anhydride, which can be prepared
from the corresponding monomers e.g. by continuous bulk or solution
polymerization with incomplete conversions. The composition can
vary between wide limits. They can contain 5 to 25 wt. % of
repeating units derived from maleic anhydride.
[0135] These polymers may also contain o- and/or m- and/or
p-substituted styrenes, such as p-methylstyrene, vinyl toluene,
2,4-dimethylstyrene and other substituted styrenes, such as
.alpha.-methylstyrene, instead of styrene.
[0136] Rubber-containing vinyl polymers A.2 include e.g. graft
copolymers with rubber-elastic properties which are obtainable
substantially from at least two of the following monomers:
chloroprene, butadiene-1,3, isoprene, styrene, acrylonitrile,
ethylene, propylene, vinyl acetate, C.sub.1-C.sub.18-alkyl
acrylates and C.sub.1-C.sub.18-alkyl methacrylates. Such polymers
are described in "Methoden der Organischen Chemie" (Houben-Weyl),
vol. 14/1, Georg Thieme-Verlag, Stuttgart, 1961, pages 393-406 and
in C.B. Bucknall, "Toughened Plastics", Appl. Science Publishers,
London, 1977, pages 66 to 106. Preferred polymers A.2 are partially
cross-linked and have gel contents of more than 20 wt. %, or, for
example, more than 40 wt. %, or further, for example, more than 60
wt. %.
[0137] Rubber-like vinyl polymers A.2 include graft copolymers of:
[0138] A.2.1 5 to 95, preferably 30 to 80 parts by wt. of a mixture
of [0139] A.2.1.1 50 to 95 parts by wt. of styrene,
.alpha.-methylstyrene, ortho-, meta- and/or para- or
halogenostyrene, or ortho-, meta- and/or para-methylstyrenes,
methyl methacrylate or mixtures of these compounds and [0140]
A.2.1.2 5 to 50 parts by wt. of acrylonitrile, methacrylonitrile,
methyl methacrylate, maleic anhydride, C.sub.1-C.sub.4-alkyl or
phenyl-N-substituted maleic imides or mixtures of these compounds
on [0141] A.2.2 5 to 95, preferably 20 to 70 parts by wt. of rubber
polymer with a glass transition temperature below -10.degree.
C.
[0142] Graft copolymers A.2 include, eg. polybutadiene,
butadiene/styrene copolymers and acrylate rubbers grafted with
styrene and/or acrylonitrile and/or alkyl acrylates or alkyl
methacrylates; and also copolymers of the type described in DE-A 1
694 173, page 2, line 32 to page 4, line 10; polybutadienes,
butadiene/styrene or butadiene/acrylonitrile copolymers,
polyisobutenes or polyisoprenes grafted with alkyl acrylates or
methacrylates, vinyl acetate, acrylonitrile, styrene and/or
alkylstyrenes, as described in DE-A 2 348 377, page 4, line 14 to
page 5, line 2.
[0143] Polymers A.2 include ABS polymers as described in DE-A 2 035
390, page 2, line 15 to page 3, line 6 and in DE-A 2 248 242, page
11, line 3 to page 13, line 17.
[0144] Graft copolymers A.2 can be obtained by the graft
polymerization of [0145] .alpha.. 10 to 70, or, 15 to 50, of, for
example, 20 to 40 wt. % (with respect to graft copolymer A.2) of
acrylates or methacrylates or of 10 to 70, or, 15 to 50, of, for
example, 20 to 40 wt. % of a mixture of 10 to 50, or, 20 to 35 wt.
% (with respect to the mixture of acrylonitrile, acrylate, or
methacrylate and styrene) of acrylonitrile, acrylates or
methacrylates and 50 to 90, or, for example, 65 to 80 wt. % (with
respect to the mixture of acrylonitrile, acrylate, or methacrylate
and styrene) of styrene (as graft covering A.2.1) on [0146] .beta..
30 to 90, or, 50 to 85, or, for example, 60 to 80 wt. %, with
respect to graft polymer A.2, of a butadiene polymer containing at
least 50 wt. %, with respect to 0, of butadiene groups (as graft
substrate A.2.2), wherein the gel content of graft substrate .beta.
is at least 40 wt. % (measured in toluene), the degree of grafting
G is 0.15 to 0.55 and the average particle diameter d.sub.50 of
graft polymer A.2 is 0.05 to 2 .mu.m, or, for example, 0.1 to 0.6
.mu.m.
[0147] Acrylates and methacrylates .alpha. are esters of acrylic
acid or methacrylic acid and monohydric alcohols with 1 to 18
carbon atoms. Methyl methacrylate, ethyl methacrylate, propyl
methacrylate, n-butyl acrylate, t-butyl acrylate and t-butyl
methacrylate are particularly preferred.
[0148] The butadiene polymer .beta. can contain, apart from
butadiene groups, up to 50 wt. %, with respect to .beta., of groups
from other ethylenically unsaturated monomers such as styrene,
acrylonitrile, C.sub.1-C.sub.4-alkyl esters of acrylic or
methacrylic acid (such as methyl acrylate, ethyl acrylate, methyl
methacrylate, ethyl methacrylate) vinyl esters and/or vinyl ethers.
For example, .beta. can contain polybutadiene.
[0149] During graft polymerization the graft monomers, as is known,
do not polymerize fully on the graft substrate; however, graft
polymer A.2 includes products which have been obtained by graft
polymerization in the presence of the graft substrate.
[0150] The degree of grafting G is the ratio by weight of
grafted-on graft monomers to graft substrate (a dimensionless
number).
[0151] The average particle diameter d.sub.50 is the diameter above
and below which lie 50% each of the particles. It can be determined
by means of ultracentrifuge measurement (W. Scholtan, H. Lange,
Kolloid, Z. und Z. Polymere 250 (1972), pages 782 to 796).
[0152] Further particularly preferred polymers A.2 are graft
copolymers made from [0153] .tau.. 20 to 90 wt. %, with respect to
A.2, of acrylate rubber with a glass transition temperature below
-20.degree. C., as graft substrate A.2.2, and [0154] .epsilon.. 10
to 80 wt. %, with respect to A.2, of at least one polymerizable
ethylenically unsaturated monomer, the homopolymer or copolymer(s)
of which, produced in the absence of .tau.., have a glass
transition temperature above 25.degree. C., as graft monomer
A.2.1.
[0155] The acrylate rubbers .tau. in polymer A.2 include polymers
of alkyl acrylates, optionally with up to 40 wt. %, with respect to
.tau., of other polymerizable, ethylenically unsaturated monomers.
Included among the polymerizable esters of acrylic acid are
C.sub.1-C.sub.8-alkyl esters, for example methyl, ethyl, butyl,
n-octyl and 2-ethylhexyl esters; halogenoalkyl esters, preferably
halogeno-C.sub.1-C.sub.8-alkyl esters such as chloroethyl acrylate,
and mixtures of these monomers.
[0156] For cross-linking purposes, monomers with more than one
polymerizable double bond can be copolymerized. Examples of
cross-linking monomers include esters of unsaturated monocarboxylic
acids with 3 to 8 carbon atoms and unsaturated monohydric alcohols
with 3 to 12 carbon atoms or saturated polyols with 2 to 4 OH
groups and 2 to 20 carbon atoms, such as ethylene glycol
dimethacrylate, allyl methacrylate; polyunsaturated heterocyclic
compounds such as trivinyl and triallyl cyanurate; polyfunctional
vinyl compounds such as di- and trivinylbenzenes; but also trially
phosphate and diallyl phthalate.
[0157] Cross-linking monomers include allyl methacrylate, ethylene
glycol dimethacrylate, diallyl phthalate and heterocyclic compounds
which contain at least 3 ethylenically unsaturated groups.
[0158] Cross-linking monomers include the cyclic monomers triallyl
cyanurate, triallyl isocyanurate, trivinyl cyanurate,
triacryloylhexahydrotriazine, triallylbenzene.
[0159] The amount of cross-linking monomers can be 0.02 to 5, or,
for example, 0.05 to 2 wt. %, with respect to graft substrate
.tau..
[0160] In the case of cyclic cross-linking monomers with at least 3
ethylenically unsaturated groups, it is possible to restrict the
amount to less than 1 wt. % of graft substrate .tau..
[0161] "Other" polymerizable ethylenically unsaturated monomers
which optionally can be used to prepare the graft substrate, apart
from esters of acrylic acid, are acrylonitrile, styrene,
.alpha.-methylstyrene, acrylamide, vinyl-C.sub.1-C.sub.6-alkyl
ethers, methyl methacrylate, butadiene. Acrylate rubbers for use as
graft substrate .tau. are emulsion polymers which have a gel
content of at least 60 wt. %.
[0162] Other suitable graft substrates in accordance with A.2.2 are
silicone rubbers with graft-active sites like those described in
DE-A 37 04 657, column 5, line 21 to column 6, line 52; DE-A 37 04
655, column 5, line 24 to column 6, line 65; DE-A 36 31 540, page
6, line 65 to page 7, line 45; and DE-A 36 31 539, page 6, line 54
to page 7, line 35.
[0163] The gel content of the graft substrate A.2.2 is determined
at 25.degree. C. in dimethylformamide (M. Hoffmann, H. Kromer, R.
Kuhn, Polymeranalytik I and II, Georg Thieme-Verlag, Stuttgart,
1977).
[0164] Graft polymers A.2 can be prepared by known processes such
as bulk, suspension, emulsion or bulk-suspension processes.
[0165] The mixture according to the present invention can also be
incorporated into polyurethanes using methods known to a person
skilled in the art. Polyurethanes are understood to be polymers
which are obtained by the addition reaction of polyisocyanates with
compounds which can react with isocyanates. Compounds which can
react with isocyanates are understood to be compounds which contain
at least 2 hydroxyl and/or amino groups bonded to an organic
group.
[0166] Suitable organic diisocyanates are, for example, aliphatic,
cycloaliphatic, araliphatic, heterocyclic and aromatic
diisocyanates, such as are described in Justus Liebigs Annalen der
Chemie, 562, p. 75-136. Aromatic and cycloaliphatic diisocyanates
are useful.
[0167] The following may be mentioned, by way of example: aliphatic
diisocyanates such as hexamethylene diisocyanate, cycloaliphatic
diisocyanates such as isophorone diisocyanate, 1,4-cyclohexane
diisocyanate, 1-methyl-2,4-cyclohexane diisocyanate, and
1-methyl-2,6-cyclohexane diisocyanate as well as the corresponding
isomer mixtures, 4,4'-dicyclohexylmethane diisocyanate,
2,4'-dicyclohexylmethane diisocyanate and 2,2'-dicyclohexylmethane
diisocyanate and the corresponding isomer mixtures, aromatic
diisocyanates such as 2,4-toluoylene diisocyanate, mixtures of
2,4-toluoylene diisocyanate and 2,6-toluoylene diisocyanate,
4,4'-diphenylmethane diisocyanate 2,4'-diphenylmethane diisocyanate
and 2,2'-diphenylmethane diisocyanate, mixtures of
2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane
diisocyanate, urethane-modified liquid 4,4'-diphenylmethane
diisocyanates and 2,4'-diphenylmethane diisocyanates,
4,4'-diisocyanato-diphenylethane-1,2 and 1,5-naphthylene
diisocyanate. 1,6-hexamethylene diisocyanate, isophorone
diisocyanate, dicyclohexylmethane diisocyanate, diphenylmethane
diisocyanate isomer mixtures with a 4,4'-diphenylmethane
diisocyanate content of >96 wt. % are preferably used and in
particular 4,4'-diphenylmethane diisocyanate and 1,5-naphthylene
diisocyanate. The diisocyanates mentioned may be used individually
or in the form of mixtures with each other. They may be used with
up to 15 wt. % (calculated with respect to the total amount of
diisocyanate) of a polyisocyanate such as
triphenylmethane-4,4',4''-triisocyanate or
polyphenyl-polymethylene-polyisocyanates.
[0168] Useful, isocyanates include 1,6-hexamethylene diisocyanate,
isophorone diisocyanate, dicyclohexylmethane diisocyanate,
diphenylmethane diisocyanate isomer mixtures with a
4,4'-diphenylmethane diisocyanate content of >96 wt. % and in
particular 4,4'-diphenylmethane diisocyanate and 1,5-naphthylene
diisocyanate. Compounds which react with isocyanates include linear
hydroxyl-terminated polyols with an average molecular weight Mn of
500 to 10000, or, 500 to 5000, or, for example, 600 to 2000. These
frequently contain up to 1 wt. % of non-linear compounds as a
result of the method of production. Therefore reference is often
made to "substantially linear polyols". Polyetherdiols,
polycarbonatediols, sterically hindered polyester diols,
hydroxyl-terminated polybutadienes or mixtures of these are useful
in the present invention.
[0169] Suitable polyetherdiols can be prepared by reacting one or
more alkylene oxides with 2 to 4 carbon atoms in the alkylene group
with a starter molecule which contains two bonded active hydrogen
atoms. The following may be mentioned as alkylene oxides: ethylene
oxide, 1,2-propylene oxide, epichlorohydrin and 1,2-butylene oxide
and 2,3-butylene oxide. Ethylene oxide and 1,2-propylene oxide and
mixtures of 1,2-propylene oxide and ethylene oxide can, for
example, be used.
[0170] The alkylene oxides can be used individually, alternately or
as mixtures. Suitable starter molecules are, for example: water,
aminoalcohols such as N-alkyldiethanolamines, for example
N-methyldiethanolamine, and diols such as ethylene glycol,
1,3-propylene glycol, 1,4-butanediol and 1,6-hexanediol.
Optionally, mixtures of starter molecules may also be used.
[0171] Suitable polyetherdiols include the hydroxyl
group-containing polymerization products of tetrahydrofuran.
Trifunctional polyethers can also be used in proportions of 0 to 30
wt. %, with respect to the bifunctional polyethers, but at most in
such an amount that a thermoplastically processable product is
produced. The substantially linear polyetherdiols may be used
either individually or in the form of mixtures with each other.
[0172] Suitable polyester diols can be prepared, for example, from
dicarboxylic acids with 2 to 12 carbon atoms, preferably 4 to 6
carbon atoms and polyhydric alcohols. Suitable dicarboxylic acids
are, for example: aliphatic dicarboxylic acids such as succinic
acid, glutaric acid, adipic acid, suberic acid, azelaic acid and
sebacic acid and aromatic dicarboxylic acids such as phthalic acid,
isophthalic acid and terephthalic acid. The dicarboxylic acids can
be used individually or in the form of mixtures, such as in the
form of a succinic, glutaric and adipic acid mixture. To prepare
the polyesterdiols, it may optionally be advantageous to use,
instead of dicarboxylic acids, the corresponding dicarboxylic acid
derivatives such as dicarboxylates with 1 to 4 carbon atoms in the
alcohol group, carboxylic anhydrides or carboxylic chlorides.
Examples of polyhydric alcohols are glycols with 2 to 10, or, for
example, 2 to 6 carbon atoms, such as ethylene glycol, diethylene
glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,
1,10-decanediol, 2,2,-dimethyl-1,3-propanediol, 1,3-propanediol and
dipropylene glycol. Depending on the properties desired, the
polyhydric alcohols may be used on their own or optionally as a
mixture with each other. Furthermore, esters of carbonic acid with
the diols mentioned, in particular those with 4 to 6 carbon atoms,
such as 1,4-butanediol or 1,6-hexanediol, condensation products of
hydroxycarboxylic acids such as hydroxycaproic acid and
polymerization products of lactones, optionally substituted
caprolactones are also suitable. The following are useful as
polyesterdiols: ethanediol-polyadipate, 1,4-butanediol-polyadipate,
ethanediol-1,4-butanediol-polyadipate,
1,6-hexanediol-neopentylglycol-polyadipate,
1,6-hexanediol-1,4-butanediol-polyadipate and polycaprolactones.
The polyesterdiols may be used individually or in the form of
mixtures with each other.
[0173] A summary of the principle of preparation, the starting
materials, the catalysis of urethane formation, the additives used,
the various types and forms of application, the various methods of
preparation and the areas of use is given in Ullmann's Encyclopedia
of Industrial Chemistry, Wiley-VCH Verlagsgesellschaft mbH, D-69451
Weinheim, 1992, vol. A21, p. 665-716. The polyurethanes which can
be prepared by this process may contain the fillers and additives
known to a person skilled in the art such as antioxidants, UV
stabilizers, auxiliary substances and additives, as described in
DE-A 29 01 774, page 14, line 16 to page 15, line 2, such as Ionol,
Irganox.RTM. 1076, Irganox.RTM. 1098, Tinuvin.RTM. 144,
Irgafos.RTM. 38, Hochstwachs.RTM. C, Acrawax.RTM. or Loxamid.RTM..
The following may also be mentioned: lubricants such as esters of
fatty acids, their metal soaps, fatty acid amides and silicone
compounds, antiblocking agents, inhibitors, stabilizers against
hydrolysis, heat and discoloration, flame retardants, colorants,
pigments, inorganic and organic fillers and reinforcing agents.
[0174] Further advantages of the mixture according to the present
invention, the method of preparation of same and the polymeric
radiation protection substances which are prepared from the mixture
according to the present invention and the polymers are: less
weight, toxicological acceptability, freedom from heavy metals in
the radiation protection additive, environmentally friendly waste
disposal after use, long service life, lower wear and tear due to
high mechanical properties, sterilizability by hot steam.
[0175] The polymeric radiation protection substances according to
the invention described here, in which either polyurethanes,
thermoplastic materials or rubbers can be used as the polymer, can
be used to screen electromagnetic radiation from television or
monitor housings. They can be used as the starting material for
radiation-protected items of clothing such as aprons, jackets,
waistcoats, trousers, gloves, or for the protection of thyroid
glands, ovaries and gonads. Furthermore they can be used on the
walls of rooms in the form of rubber or plastic mats or on
floorings in the form of rubber floor coverings (combining damping
the sound of footsteps with a screening effect). The mixtures
according to the present invention can be admixed as a powder to
cement or concrete mixtures to prepare building bricks, concrete or
tiles. They can also be used in polyurethane foams for heat
insulation. Films, foils and containers, which can be used as
casings or packaging for photographic films to protect the contents
from exposure to X-radiation, can be prepared from polymeric
radiation protection substances filled with the mixture according
to the present invention.
EXAMPLES
General
[0176] Unless stated otherwise, all amounts of components and
compounds are to be understood as given with reference to weight,
calculated to the amount of all elements.
[0177] To determine the screening effect, the mixtures according to
the present invention were used in a thickness which provides
protection from electromagnetic radiation with energies greater
than 10 keV, with attenuation factors which correspond to a layer
of metallic lead with a thickness of at least 0.1 mm to 1.0 mm.
This equivalent is measured in the same way that lead equivalents
were determined, in accordance with the prior art according to DIN
6845, by using X-radiation at different tube potentials (X-ray tube
with a tungsten anticathode), typically at 75 kV, 100 kV, 150 kV or
300 kV with defined beam geometries and defined beam qualities.
[0178] In a second process, step wedges were made by gluing plates
on top of each other. Areas of different thickness are produced,
thus each providing different bulk coverings by the mixture
according to the present invention. The step wedges were exposed to
X-radiation with different tube potentials and the exposed X-ray
films are evaluated densitometrically. The same degree of
blackening indicates the same degree of absorption of the
radiation. Less blackening indicates a better screening effect.
[0179] In the examples, the particular process used to determine
the screening characteristics is described.
[0180] In order to relate the results of the irradiation tests to a
quantity which is independent of the sample density and the degree
of filling by the radiation protection additive, the bulk covering
is defined as follows:
[0181] Bulk covering=density of the sample
[g/cm.sup.3].times.degree of filling by the polymeric radiation
protection substance [%].times.thickness of the sample [cm]/100
Example 1
a) Raw Materials Used and their Composition
[0182] A mixture according to the invention was prepared from the
following components:
TABLE-US-00001 Proportion in the mixture according to the present
Name Manufacturer invention Optipol polishing powder Tschepetsk
Mechanisches 29.5 wt. % Werk AG, Glasow Gadolinium concentrate
"Moscow Polymetal 39.0% Works", government business enterprise,
Moscow Tungsten powder 6.1 "Kirov Works for Hard 31.5% Alloys",
Swerdlower District
b) Composition According to Manufacturer's Data
TABLE-US-00002 [0183] Conc. of rare Name earths La.sub.2O.sub.3
CeO.sub.2 Pr.sub.6O.sub.11 Nd.sub.2O.sub.3 Sm.sub.2O.sub.3
Eu.sub.2O.sub.3 Gd.sub.2O.sub.3 Tb.sub.2O.sub.3 Dy.sub.2O.sub.3
Gadolinium 97.1 -- -- -- -- 0.9 0.8 93.8 <0.3 0.5 conc. Optipol
96.0 24.1 54.5 4.0 14.5 0.8 0.2 <0.1 <0.3 --
c) Preparation of the Mixture According to the Present
Invention
[0184] Before use, the Optipol polishing powder, gadolinium
concentrate and tungsten powder were dried at a temperature of
120.degree. C. for two hours and classified through sieve 063
(tungsten through sieve 016). Then the three components were mixed
in a tumble mixer for 24 hours.
[0185] An orange-brown, free flowing, lump-free powder with a
density of 8.55 g/cm.sup.3 was obtained as the mixture according to
the present invention. The density was measured by a pycnometric
method with isopropanol, ethanol and acetone as the measuring
liquid.
Example 2
[0186] Commercially available aromatic thermoplastic polyurethane
(TPU), softening point about 160.degree. C., processing temperature
about 200.degree. C., density 1.2 g/cm.sup.3.
[0187] Samples 1 to 5 were prepared from the polyurethane and the
mixture according to the present invention from example 1 by
calandering: the rollers on a calander were preheated to slightly
above the melting point, i.e. to about 170.degree. C. The TPU was
applied to the preheated rollers and homogenized on the revolving
rollers after melting. Then the mixture according to the invention
from example 1 was added in portions. The material was compounded
until it was externally homogeneous. It was established, from X-ray
tests on the homogeneity of the TPU/additive mixtures, that about 1
hour compounding time on the rollers was required.
[0188] Then the compounds were introduced into a mould coated with
silicone spray as a separating agent. The filled mould was heated
to 170.degree. C. to 180.degree. C. processing temperature in a
hydraulic press with electric heating. The temperature was held
constant for 15 minutes and then a pressure of 150 bar was applied.
On cooling to room temperature the pressure was increased to 350
bar. The disc-like molded items had a diameter of 50 mm and a depth
of 0.85 to 0.9 mm; they were removed after reducing the pressure to
atmospheric and their density was determined.
[0189] Samples of the mixture according to the present invention
and the TPU were prepared using the process described above:
TABLE-US-00003 Additive conc. Density Thickness Bulk covering Name
[k.sub.A] [.rho..sub.p] [d.sub.p] [m.sub.A] Sample 1 14.7 wt. %
1.38 g/cm.sup.3 3.29 mm 0.067 g/cm.sup.2 Sample 2 17.7 wt. % 1.42
g/cm.sup.3 6.23 mm 0.157 g/cm.sup.2 Sample 3 57.2 wt. % 2.36
g/cm.sup.3 1.78 mm 0.240 g/cm.sup.2 Sample 4 75.7 wt. % 3.4
g/cm.sup.3 0.99 mm 0.255 g/cm.sup.2 Sample 5 84.0 wt. % 4.26
g/cm.sup.3 1.12 mm 0.401 g/cm.sup.2 m.sub.A = k.sub.A .rho..sub.p
d.sub.p Bulk covering = proportion by weight of mixture according
to the invention .times. density of the sample .times. thickness of
the sample
Example 3
Testing the X-Ray Protection Characteristics
[0190] The screening characteristics of sample 1 to sample 5 were
measured in the geometry of the narrow beam cluster in accordance
with DIN 6845 using tungsten X-ray tubes with defined beam quality.
The beam quality of the ISO spectrum H-100 was achieved by total
flittering with Al and Cu filters. The degree of attenuation and
the lead equivalents of the samples were determined.
[0191] Beam quality ISO-H-100 was achieved by: accelerating voltage
U=100 kV and filter: 4 mm Al+0.11 mm Cu.
TABLE-US-00004 U = 100 kV, 4 mm Al + 0.11 mm Cu Bulk covering Lead
equivalent Name [m.sub.A] Degree of attenuation mm Pb Sample 1
0.067 g/cm.sup.2 1.94 0.06 mm Sample 2 0.157 g/cm.sup.2 3.92 0.17
mm Sample 3 0.240 g/cm.sup.2 6.97 0.28 mm Sample 4 0.255 g/cm.sup.2
7.05 0.28 mm Sample 5 0.401 g/cm.sup.2 17.8 0.5 mm
[0192] The lead samples used for calibration and comparison
measurements had a diameter of 50 mm. They were cut from lead foils
of grade S1 with a thickness of 0.065 mm and 0.085 mm. The test
region covered lead equivalents from 0.1 to 0.5 mm. The thickness
of the lead samples introduced was determined by a weighing
procedure, using the total weight, sample area and the specific
density of lead of 11.3 g/cm.sup.3.
TABLE-US-00005 Bulk covering Degree of Lead equivalent Name
[m.sub.A] attenuation mm Pb Sample 6 (lead 0.135 g/cm.sup.2 2.5
0.11 mm comparison) Sample 7 (lead 0.28 g/cm.sup.2 5.8 0.24 mm
comparison) Sample 8 (lead 0.4 g/cm.sup.2 9.5 0.34 mm comparison
Sample 9 (lead 0.465 g/cm.sup.2 12.5 0.43 mm comparison) Sample 10
(lead 0.59 g/cm.sup.2 19 0.52 mm comparison)
[0193] For the same bulk covering of 0.4 g/cm.sup.2, the degree of
attenuation of sample 5, was 17.8, whereas the lead comparison
(sample 8) had a degree of attenuation of only 9.5. That means
that, for the same radiation protection effect as lead, a lower
bulk covering is required, which can be achieved by a smaller
thickness or a lower degree of filling of the sample. This leads to
a weight saving and thus to increased wearer comfort for the items
produced therefrom, such as e.g. X-ray aprons.
Comparison Example 4
a) Raw Materials Used and their Composition
[0194] The mixture was prepared from the following components:
TABLE-US-00006 Bismuth oxide Batch 161 57.0 wt. % Tungsten powder
6.1 Batch 68 43 wt. %
b) Composition According to the Manufacturer's Data
TABLE-US-00007 [0195] Name Concentration of Bismuth oxide 97.1 wt.
% Tungsten powder 6.1 99.9 wt. %
c) Preparation of this Mixture According to Example 4
[0196] Before use, the bismuth oxide and tungsten powder were dried
for 2 hours at a temperature of 120.degree. C. and classified
through sieve 063 (tungsten through sieve 016). Then the components
were mixed for 24 hours in a tumble mixer.
[0197] An orange-brown, free-flowing, lump-free powder with a
density of 11.8 g/cm.sup.3 was obtained, measured using a
pycnometric method with isopropanol, ethanol and acetone as the
measuring liquid.
Example 5
[0198] Commercially available acrylonitrile-butadiene-styrene block
copolymer (ABS), softening point about 200.degree. C., processing
temperature about 220.degree. C., density 1.05 g/cm.sup.3.
[0199] The mixture from example 4 was incorporated into the ABS
plastics material by calandering: the rollers on a calander were
preheated to about 180.degree. C. The ABS was applied to the
preheated rollers and homogenized on the revolving rollers after
melting. Then the mixture (example 4) was added in portions. The
material was compounded until it was externally homogeneous. It was
established, from X-ray tests on the homogeneity of the ABS/example
4 mixture, that about 1 hour compounding time on the rollers was
required.
[0200] Then the compounds were introduced into a mould coated with
silicone spray as a separating agent. The filled mould was heated
to 190.degree. C. to 200.degree. C. processing temperature in a
hydraulic press with electric heating. The temperature was held
constant for 15 minutes and then a pressure of 150 bar was applied.
On cooling to room temperature the pressure was increased to 350
bar. The disc-like molded items had a diameter of 50 mm and a depth
of 0.85 to 6.5 mm; they were removed after reducing the pressure to
atmospheric and their density was determined.
[0201] Samples of the mixture according to example 4 and the ABS
were prepared using the process described above:
TABLE-US-00008 Additive conc. Density Thickness Bulk covering Name
[k.sub.A] [.rho..sub.p] [d.sub.p] [m.sub.A] Sample 11 16.1 wt. %
1.215 g/cm.sup.3 6.45 mm 0.126 g/cm.sup.2 Sample 12 30.7 wt. %
1.441 g/cm.sup.3 6.46 mm 0.286 g/cm.sup.2 Sample 13 40.3 wt. % 1.64
g/cm.sup.3 6.55 mm 0.433 g/cm.sup.2 Sample 114 65.4 wt. % 2.572
g/cm.sup.3 2.05 mm 0.345 g/cm.sup.2 Sample 15 84.3 wt. % 4.488
g/cm.sup.3 1.46 mm 0.552 g/cm.sup.2 m.sub.A = k.sub.A .rho..sub.p
d.sub.P Bulk covering = proportion by weight of mixture according
to example 4 in the sample .times. density of the sample .times.
thickness of the sample
Example 6
Testing the X-Ray Protection Characteristics
[0202] The screening characteristics of samples 11 to sample 15
were measured in the geometry of the narrow beam cluster in
accordance with DIN 6845 using tungsten X-ray tubes with defined
beam quality. The beam quality of the ISO spectrum H-300 was
achieved by total filtering with a Cu filter. The degree of
attenuation and the lead equivalents of the samples were
determined.
[0203] Beam quality ISO-H-300 was achieved by: accelerating voltage
U=300 kV and filter: 2.5 mm Cu.
TABLE-US-00009 U = 300 kV, 2.5 mm Cu Bulk covering Degree of Lead
equivalent Name [m.sub.A] attenuation mm Pb Sample 11 0.126
g/cm.sup.2 1.38 0.152 mm Sample 12 0.286 g/cm.sup.2 1.76 0.285 mm
Sample 13 0.433 g/cm.sup.2 2.15 0.407 mm Sample 14 0.345 g/cm.sup.2
1.81 0.299 mm Sample 15 0.552 g/cm.sup.2 2.3 0.449 mm
[0204] The lead samples used for calibration and comparison
measurements had a diameter of 50 mm. They were cut from lead foils
of grade S1 with a thickness of 0.065 mm and 0.085 mm. The test
region covered lead equivalents from 0.1 to 0.5 mm. The thickness
of the lead samples introduced was determined by a weighing
procedure, using the total weight, sample area and the specific
density of lead of 11.3 g/cm.sup.3.
TABLE-US-00010 Bulk covering Degree of Lead equivalent Name
[m.sub.A] attenuation mm Pb Sample 16 (lead 0.12 g/cm.sup.2 1.24
0.10 mm comparison) Sample 17 (lead 0.2 g/cm.sup.2 1.43 0.17 mm
comparison) Sample 18 (lead 0.25 g/cm.sup.2 1.57 0.22 mm comparison
Sample 19 (lead 0.36 g/cm.sup.2 1.87 0.32 mm comparison)
[0205] For the same bulk covering, the degree of attenuation in the
region between 0.1 and 0.5 mm lead equivalents in the narrow beam
cluster for sample 11 to sample 15 according to the invention is
higher than lead. The samples according to the invention screen the
radiation better, so for the same screening effect a lighter or
thinner component can be produced.
[0206] Although this mixture not according to the invention is
better than lead at the accelerating voltage of 100 kV relevant for
X-ray diagnostics, they are much poorer than mixtures according to
the invention.
Example 7
[0207] A mixture according to the present invention was prepared
from rare earth and tungsten powder in accordance with example 1,
the composition being as follows:
TABLE-US-00011 Rare earths Proportion in the mixture
La.sub.2O.sub.3 7.0% CeO.sub.2 14.7% Nd.sub.2O.sub.3 3.8%
Gd.sub.2O.sub.3 44.4% Pr.sub.6O.sub.11 1.4% Eu.sub.2O.sub.3 0.3%
Sm.sub.2O.sub.3 0.6% Y.sub.2O.sub.3 0.05% W 27.3%
[0208] Before use, the rare earths and tungsten powder were dried
for 2 hours at a temperature of 120.degree. C. and classified
through sieve 063 (tungsten through sieve 016). Then the three
components were mixed for 2 hours in a tumble mixer.
[0209] An orange-brown, free-flowing, lump-free powder with a
density of 8.55 g/cm.sup.3 was obtained as a mixture according to
the invention. The density was measured using a pycnometric method
with isopropanol, ethanol and acetone as the measuring liquid.
Example 8
[0210] 66.1 wt. % of the previously prepared mixture according to
the present invention (from example 7) are added in 2-3 portions to
27.5 wt. % of a synthetic elastomer (EVM ethylene/vinylacetate
copolymer with about 40 wt. % of ethylene and about 60 wt. % of
vinyl acetate) (Levapren.RTM. 600 HV) and homogenized on a roller
system or internal mixer. Then the following were added: 2.8 wt. %
of Regale SRF carbon black from Cabot, 0.8 wt. % of Rhenogran.RTM.
P-50 anti-hydrolysis agent from Rhein-Chemie, polycarbodiimide, 0.4
wt. % of Rhenofit.RTM. DDA styrenated diphenylamine from
Rhein-Chemie, 0.3 wt. % of stearic acid, 1.0 wt. % of Rhenofit.RTM.
TAC triallyl cyanurate from Rhein-Chemie and 1.1 wt. % of
Polydispersion.RTM. T
.alpha.,.alpha.'-bis-(tert-butylperoxy)-diisopropylbenzene,
peroxide cross-linker from Rhein-Chemie. After renewed
homogenization, the mixture could be drawn out as a sheet on a
roller or calandered. Production of the radiation-absorbing
articles was achieved after pressure forming or calandering by
vulcanizing at temperatures between 150.degree. C. and 170.degree.
C. and was completed in 30 minutes.
[0211] Samples of the mixture according to the present invention
from example 7 and the rubber were prepared by the process
described above:
TABLE-US-00012 Name Additive content [k.sub.A] Density
[.rho..sub.p] Sample 20 66.1 wt. % 2.554 g/cm.sup.3
TABLE-US-00013 Name Thickness [d.sub.p] Bulk covering [m.sub.A]
Sample 20 2 mm 0.34 g/cm.sup.2 Sample 21 4 mm 0.68 g/cm.sup.2
Sample 22 6 mm 1.01 g/cm.sup.2 Sample 23 8 mm 1.35 g/cm.sup.2
Sample 24 10 mm 1.69 g/cm.sup.2 m.sub.A = k.sub.A .rho..sub.p
d.sub.p Bulk covering = proportion by weight of mixture in the
sample .times. density of the sample .times. thickness of the
sample
Example 9
Testing the Radiation Protection Properties
[0212] Step wedges were produced from the 20 cm.times.20 cm.times.2
mm rubber sheets by gluing them together. Areas with 2, 4, 6, 8 and
10 mm thickness were produced. The step wedges were exposed to
X-radiation of beam quality U=100 kV, eff. filtering 2.5 mm Al,
tungsten direct current X-ray tube for 960 s and the X-ray film was
evaluated densitometrically. In the following, the results of this
exposure of step wedges made from the radiation-absorbing materials
in this invention are given, and in fact compared with step wedges
made of lead. The same degree of blackening means the same degree
of absorption of radiation. Less blackening indicates a better
screening effect.
TABLE-US-00014 Blackening Name Thickness [d.sub.p] Bulk covering
[m.sub.A] (relative units) Sample 20 2 mm 0.34 g/cm.sup.2 6.48
Sample 21 4 mm 0.68 g/cm.sup.2 1.98 Sample 22 6 mm 1.01 g/cm.sup.2
0.47 Sample 23 8 mm 1.35 g/cm.sup.2 0.24 Sample 24 10 mm 1.69
g/cm.sup.2 0.21
[0213] The lead samples used for calibration and comparison samples
were prepared from lead foils of grade S1 with a thickness of 0.1
mm. Step wedges like those for the samples were prepared from the
lead foils. The test region covered the lead equivalents from 0.1
to 1.0 mm.
TABLE-US-00015 Bulk covering Blackening Name Thickness [d.sub.p]
[m.sub.A] (relative units) Sample 25 (lead 0.1 mm 0.11 g/cm.sup.2
6.50 comparison) Sample 26 (lead 0.2 mm 0.23 g/cm.sup.2 6.50
comparison) Sample 27 (lead 0.3 mm 0.34 g/cm.sup.2 6.50 comparison)
Sample 28 (lead 0.4 mm 0.45 g/cm.sup.2 6.50 comparison) Sample 29
(lead 0.5 mm 0.56 g/cm.sup.2 5.18 comparison) Sample 30 (lead 0.6
mm 0.68 g/cm.sup.2 3.75 comparison) Sample 31 (lead 0.7 mm 0.80
g/cm.sup.2 2.82 comparison) Sample 32 (lead 0.8 mm 0.91 g/cm.sup.2
2.11 comparison) Sample 33 (lead 0.9 mm 1.03 g/cm.sup.2 1.61
comparison) Sample 34 (lead 1.0 mm 1.14 g/cm.sup.2 1.29
comparison)
[0214] For the same bulk covering of 0.5 g/cm.sup.2, the degree of
blackening for sample 21 was 1.98, whereas the comparison sample
(sample 29 (lead comparison)) allowed much more radiation to pass
through and had a degree of blackening of 5.1. Less blackening
indicates a better screening effect. That means that, for the same
radiation protection effect as lead, a smaller bulk covering is
required, which can be achieved by a smaller thickness or a lower
degree of filling by the samples. This leads to a weight saving and
thus to increased wearer comfort for the items produced therefrom
such as e.g. X-ray aprons.
Example 10
Mechanical Data
[0215] The mechanical strength of the rubber sheets produced in
example 8 was tested.
[0216] The following mechanical test data were determined:
TABLE-US-00016 Tear strength (DIN 53504/ISO 37-1977): >10 MPa
Elongation at break (DIN 53504/ISO 37-1977): >250% Modulus 200%
(DIN 53504/ISO 37-1977): 7 MPa Hardness (DIN 53505/ISO 868-1985):
63 Shore A
Example 11
[0217] A mixture according to the present invention was prepared
from rare earths and tungsten powder. It had the following
composition:
TABLE-US-00017 Rare earths Proportion in the mixture
La.sub.2O.sub.3 6.88% CeO.sub.2 13.37% Nd.sub.2O.sub.3 3.66%
Gd.sub.2O.sub.3 47.34% Pr.sub.6O.sub.11 1.24% Eu.sub.2O.sub.3 0.07%
Sm.sub.2O.sub.3 0.40% Y.sub.2O.sub.3 0.04% W 27.00%
[0218] Before use, the rare earths and tungsten powder were dried
for 2 hours at a temperature of 120.degree. C. and classified
through sieve 063 (tungsten through sieve 016). Then the three
components were mixed for 2 hours in a tumble mixer.
Example 12
[0219] 66.1 wt. % of the previously prepared mixture according to
the invention from example 11 are added in 2-3 portions to 27.5 wt.
% of a synthetic elastomer (EVM ethylene/vinylacetate copolymer
with about 40 wt. % of ethylene and about 60 wt. % of vinyl
acetate) (Levapren.RTM. 600 HV) and homogenized on a roller system
or internal mixer. Then the following were added: 2.8 wt. % of
Regal.RTM. SRF carbon black from Cabot, 0.8 wt. % of Rhenogran.RTM.
P-50 anti-hydrolysis agent from Rhein-Chemie, polycarbodiimide, 0.4
wt. % of Rhenofit.RTM. DDA styrenated diphenylamine from
Rhein-Chemie, 0.3 wt. % of stearic acid, 1.0 wt. % of Rhenofit.RTM.
TAC triallyl cyanurate from Rhein-Chemie and 1.1 wt. % of
Polydispersion.RTM. T
.alpha.,.alpha.'-bis-(tert-butylperoxy)-diisopropylbenzene,
peroxide cross-linker from Rhein-Chemie. After renewed
homogenization, the mixture could be drawn out as a sheet on a
roller or calandered. Production of the radiation-absorbing
articles was achieved after pressure forming or calandering by
vulcanizing at temperatures between 150.degree. C. and 170.degree.
C. and was completed in 30 minutes.
[0220] Samples of the mixture according to the present invention
from example 11 and the rubber were prepared by the process
described above:
TABLE-US-00018 Name Additive content [k.sub.A] Density
[.rho..sub.p] Sample 35 66.1 wt. % 2.553 g/cm.sup.3
TABLE-US-00019 Name Thickness [d.sub.p] Bulk covering [m.sub.A]
Sample 35 2 mm 0.34 g/cm.sup.2 Sample 36 4 mm 0.68 g/cm.sup.2
Sample 37 6 mm 1.01 g/cm.sup.2 Sample 38 8 mm 1.35 g/cm.sup.2
Sample 39 10 mm 1.69 g/cm.sup.2 m.sub.A = k.sub.A .rho..sub.p
d.sub.p Bulk covering = proportion by weight of mixture in the
sample .times. density of the sample .times. thickness of the
sample
Example 13
Testing the Radiation Protection Properties at U=75 kV, 100 kV and
150 kV
[0221] Step wedges were produced from the 20 cm.times.20 cm.times.2
mm rubber sheets by gluing them together. Areas with 2, 4, 6, 8 and
10 mm thickness were produced. The step wedges were exposed to
X-radiation of beam quality U=75 kV, 100 kV or 150 kV, eff.
filtering 2.5 mm Al, tungsten direct current X-ray tube for 480 s,
960 s or 240 s and the X-ray films were evaluated
densitometrically. In the following, the results of this exposure
of step wedges made from the radiation-absorbing materials in this
invention are given and in fact compared with step wedges made of
lead. The same degree of blackening means the same degree of
absorption of radiation. Less blackening indicates a better
screening effect.
TABLE-US-00020 Bulk Blackening (relative units) Thickness covering
75 kV 100 kV 150 kV Name [d.sub.p] [m.sub.A] 480 sec 960 sec 240
sec Sample 35 2 mm 0.34 g/cm.sup.2 2.02 6.45 6.50 Sample 36 4 mm
0.68 g/cm.sup.2 0.39 1.83 2.50 Sample 37 6 mm 1.01 g/cm.sup.2 0.20
0.42 1.04 Sample 38 8 mm 1.35 g/cm.sup.2 0.18 0.25 0.58 Sample 39
10 mm 1.69 g/cm.sup.2 0.18 0.22 0.38
[0222] The lead samples used for calibration and comparison samples
were prepared from lead foils of grade S1 with a thickness of 0.1
mm. Step wedges like those for the samples were prepared from the
lead foils. The test region covered the lead equivalents from 0.1
to 1.0 mm.
TABLE-US-00021 Bulk Blackening (relative units) Thickness covering
75 kV 100 kV 150 kV Name [d.sub.p] [m.sub.A] 480 sec 960 sec 240
sec Sample 40 (Pb 0.1 mm 0.11 g/cm.sup.2 6.50 6.50 6.50 comparison)
Sample 41 (Pb 0.2 mm 0.23 g/cm.sup.2 3.55 6.50 6.50 comparison)
Sample 42 (Pb 0.3 mm 0.34 g/cm.sup.2 2.03 6.50 6.50 comparison)
Sample 43 (Pb 0.4 mm 0.45 g/cm.sup.2 1.22 6.50 6.15 comparison)
Sample 44 (Pb 0.5 mm 0.56 g/cm.sup.2 0.80 5.18 4.30 comparison)
Sample 45 (Pb 0.6 mm 0.68 g/cm.sup.2 0.55 3.75 3.25 comparison)
Sample 46 (Pb 0.7 mm 0.80 g/cm.sup.2 0.42 2.82 2.44 comparison)
Sample 47 (Pb 0.8 mm 0.91 g/cm.sup.2 0.33 2.11 1.83 comparison)
Sample 48 (Pb 0.9 mm 1.03 g/cm.sup.2 0.30 1.61 1.41 comparison)
Sample 49 (Pb 1.0 mm 1.14 g/cm.sup.2 0.27 1.29 1.19 comparison)
[0223] For the same bulk covering of e.g. 0.68 g/cm.sup.2,the
degree of blackening for sample 36 at 75 kV was 0.39, at 100 kV was
1.83 and at 150 kV was 2.50, whereas the corresponding comparison
sample (sample 45 (lead comparison)) allowed much more radiation to
pass through and had a degree of blackening of 0.55, 3.75 and 3.25
respectively. Less blackening indicates a better screening effect.
In the accelerating voltage region tested, the rubber mixture
according to the invention with the mixture according to the
invention had a better screening effect than lead. That means in
practice: in order to produce the same radiation protection effect
as lead, a smaller bulk covering is required, which can be achieved
by a smaller thickness or a lower degree of filling by the samples.
This leads to a weight saving and thus to increased wearer comfort
for the items produced therefrom such as e.g. X-ray aprons.
Example 14
Sample 50
[0224] 32.8 wt. % of the mixture according to the present invention
from example 11 are added in 2-3 portions to 54.6 wt. % of a
synthetic elastomer (EVM ethylene/vinylacetate copolymer with about
40 wt. % of ethylene and about 60 wt. % of vinyl acetate)
(Levapren.RTM. 600 HV) and homogenized on a roller system or
internal mixer. Then the following were added: 5.5 wt. % of
Regal.RTM. SRF carbon black from Cabot, 1.6 wt. % of Rhenogran.RTM.
P-50 anti-hydrolysis agent from Rhein-Chemie, polycarbodiimide, 0.8
wt. % of Rhenofit.RTM. DDA styrenated diphenylamine from
Rhein-Chemie, 0.5 wt. % of stearic acid, 1.9 wt. % of Rhenofit.RTM.
TAC triallyl cyanurate from Rhein-Chemie and 2.2 wt. % of
Polydispersion.RTM. T
.alpha.,.alpha.'-bis-(tert-butylperoxy)-diisopropylbenzene,
peroxide cross-linker from Rhein-Chemie.
Sample 51
[0225] 49.4 wt. % of the previously mixed mixture according to the
present invention from example 11 are added in 2-3 portions to 41.2
wt. % of a synthetic elastomer (EVM ethylene/vinylacetate copolymer
with about 40 wt. % of ethylene and about 60 wt. % of vinyl
acetate) (Levapren.RTM. 600 HV) and homogenized on a roller system
or internal mixer. Then the following were added: 4.1 wt. % of
Regal.RTM. SRF carbon black from Cabot, 1.2 wt. % of Rhenogran.RTM.
P-50 anti-hydrolysis agent from Rhein-Chemie, polycarbodiimide, 0.6
wt. % of Rhenofit.RTM. DDA styrenated diphenylamine from
Rhein-Chemie, 0.4 wt. % of stearic acid, 1.4 wt. % of Rhenofit.RTM.
TAC triallyl cyanurate from Rhein-Chemie and 1.5 wt. % of
Polydispersion.RTM. T
.alpha.,.alpha.'-bis-(tert-butylperoxy)-diisopropylbenzene,
peroxide cross-linker from Rhein-Chemie.
Sample 52
[0226] 66.1 wt. % of the mixture according to the present invention
from example 11 are added in 2-3 portions to 27.5 wt. % of a
synthetic elastomer (EVM ethylene/vinylacetate copolymer with about
40 wt. % of ethylene and about 60 wt. % of vinyl acetate)
(Levapren.RTM. 600 HV) and homogenized on a roller system or
internal mixer. Then the following were added: 2.8 wt. % of
Regal.RTM. SRF carbon black from Cabot, 0.8 wt. % of Rhenogran.RTM.
P-50 anti-hydrolysis agent from Rhein-Chemie, polycarbodiimide, 0.4
wt. % of Rhenofit.RTM. DDA styrenated diphenylamine from
Rhein-Chemie, 0.3 wt. % of stearic acid, 1.0 wt. % of Rhenofit.RTM.
TAC triallyl cyanurate from Rhein-Chemie and 1.1 wt. % of
Polydispersion.RTM. T
.alpha.,.alpha.'-bis-(tert-butylperoxy)-diisopropylbenzene,
peroxide cross-linker from Rhein-Chemie.
Processing Samples 50 to 52
[0227] After renewed homogenization, the mixture can drawn out as a
sheet on a roller or calandered. Production of the
radiation-absorbing articles was achieved after pressure forming or
calandering by vulcanizing at temperatures between 150.degree. C.
and 170.degree. C. and is complete in 30 minutes.
Example 15
[0228] The rubber sheets prepared with the mixture exhibited the
following mechanical properties:
TABLE-US-00022 Method Sample 50 Sample 51 Sample 52 Tear strength,
MPa: DIN 53504 10 10 10 Elongation at DIN 53504 250 250 250 break,
%: Modulus 200%, MPa: DIN 53504 6.5 6.5 6.5 Hardness, Shore A: DIN
53505 54 59 68
[0229] The rubber sheets produced with the mixture according to the
invention had very good mechanical strengths with the degrees of
filling tested. That leads to the conclusion that the cross-linking
reaction proceeds largely unaffected by the mixture according to
the invention. Sample 52 with the highest degree of filling does
not exhibit the drop in tear strength that would be expected
because the mixture according to the invention probably couples
very well into the rubber matrix via hydrogen bridging bonds.
Example 16
[0230] 79.6 wt. % of the mixture according to the present invention
from example 7 was added in 2-3 portions to 15.9 wt. % of a
synthetic elastomer (polychloroprene (Baypren.RTM. 210)) and
homogenized on a roller system or an internal mixer. Then the
following were added: 3.2 wt. % of naphthenic mineral oil (Circosol
4240), 0.2 wt. % of stabilizer (Rhenofit.RTM. DDA; styrenated
diphenylamine), 0.3 wt. % of an acid trap (Maglite DE; magnesium
oxide) and 0.7 wt. % of cross-linking chemicals (Zinkweiss
Rotsiegel; (zinc oxide) Rhenogran.RTM. MTT
(3-methyl-thiazolidinethione-2), Vulkacit.RTM. ZBEC/C (zinc
dibenzyldithiocarbamate). After renewed homogenization, the mixture
can drawn out as a sheet on a roller or calandered. Production of
the radiation-absorbing articles was achieved by vulcanizing at
temperatures between 150.degree. C. and 170.degree. C. and is
complete in 30 minutes. The following properties are achieved:
[0231] Samples of the mixture according to the present invention
from example 7 and the rubber were prepared by the process
described above:
TABLE-US-00023 Name Additive content [k.sub.A] Density
[.rho..sub.p] Sample 53 79.6 wt. % 3.734 g/cm.sup.3
TABLE-US-00024 Name Thickness [d.sub.p] Bulk covering [m.sub.A]
Sample 53 2 mm 0.59 g/cm.sup.2 Sample 54 4 mm 1.19 g/cm.sup.2
Sample 55 6 mm 1.78 g/cm.sup.2 Sample 56 8 mm 2.38 g/cm.sup.2
Sample 57 10 mm 2.97 g/cm.sup.2 m.sub.A = k.sub.A .rho..sub.p
d.sub.p Bulk covering = proportion by weight of mixture in the
sample .times. density of the sample .times. thickness of the
sample
Example 17
Testing the Radiation Protection Properties
[0232] Step wedges were produced from the 20 cm.times.20 cm.times.2
mm rubber sheets by gluing them together. Areas with 2, 4, 6, 8 and
10 mm thickness were produced. The step wedges were exposed to
X-radiation of beam quality U=100 kV, eff. filtering 2.5 mm Al,
tungsten direct current X-ray tube for 960 s and the X-ray films
were evaluated densitometrically. In the following, the results of
this exposure of step wedges made from the radiation-absorbing
materials in this invention are given and in fact compared with
step wedges made of lead. The same degree of blackening means the
same degree of absorption of radiation. Less blackening indicates a
better screening effect.
TABLE-US-00025 Bulk covering Blackening Name Thickness [d.sub.p]
[m.sub.A] (relative units) Sample 53 2 mm 0.59 g/cm.sup.2 2.60
Sample 54 4 mm 1.19 g/cm.sup.2 0.32 Sample 55 6 mm 1.78 g/cm.sup.2
0.24 Sample 56 8 mm 2.38 g/cm.sup.2 0.24 Sample 57 10 mm 2.79
g/cm.sup.2 0.24
[0233] The lead samples used for calibration and comparison samples
were prepared from lead foils of grade S1 with a thickness of 0.1
mm. Step wedges like those for the samples were prepared from the
lead foils. The test region covered the lead equivalents from 0.1
to 1.0 mm.
TABLE-US-00026 Bulk covering Blackening Name Thickness [d.sub.p]
[m.sub.A] (relative units) Sample 58 (lead 0.1 mm 0.11 g/cm.sup.2
6.15 comparison) Sample 59 (lead 0.2 mm 0.23 g/cm.sup.2 6.15
comparison) Sample 60 (lead 0.3 mm 0.34 g/cm.sup.2 6.15 comparison)
Sample 61 (lead 0.4 mm 0.45 g/cm.sup.2 6.15 comparison) Sample 62
(lead 0.5 mm 0.56 g/cm.sup.2 4.49 comparison) Sample 63 (lead 0.6
mm 0.68 g/cm.sup.2 3.03 comparison) Sample 64 (lead 0.7 mm 0.80
g/cm.sup.2 2.13 comparison) Sample 65 (lead 0.8 mm 0.91 g/cm.sup.2
1.49 comparison) Sample 66 (lead 0.9 mm 1.03 g/cm.sup.2 1.10
comparison) Sample 67 (lead 1.0 mm 1.14 g/cm.sup.2 0.93
comparison)
[0234] For the same bulk covering of 0.59 g/cm.sup.2, the degree of
blackening for sample 53 was 2.60, whereas the comparison sample
(sample 62 (lead comparison)) allowed much more radiation to pass
through and had a degree of blackening of 4.49. Less blackening
indicates a better screening effect. That means in practice: in
order to produce the same radiation protection effect as lead, a
smaller bulk covering is required, which can be achieved by a
smaller thickness or a lower degree of filling by the samples. This
leads to a weight saving and thus to increased wearer comfort for
the items produced therefrom such as e.g. X-ray aprons.
Example 18
[0235] The rubber sheets according to the present invention
prepared with the mixture according to the invention, in accordance
with example 17, exhibited the following mechanical properties:
TABLE-US-00027 Method Sample 53 Tear strength, MPa: DIN 53504 6.3
Elongation at break, %: DIN 53504 625 Modulus 100%, MPa: DIN 53504
1.8 Modulus 200%, MPa: DIN 53504 2.6 Modulus 300%, MPa: DIN 53504
3.2 Hardness, Shore A: DIN 53505 61
Example 19
[0236] 59.8 wt. % of the mixture according to the invention from
example 7 and 19.8 wt. % of BaSO.sub.4 were added in 2-3 portions
to 15.9 wt. % of a synthetic elastomer (polychloroprene
(Baypren.RTM. 210)) and homogenized on a roller system or an
internal mixer. Then the following were added: 3.2 wt. % of
naphthenic mineral oil (Circosol 4240; a mixture of alicyclic
compounds, a fraction of petroleum), 0.2 wt. % of stabilizer
(Rhenofit.RTM. DDA; styrenated diphenylamine), 0.3 wt. % of an acid
trap (Maglite DE (magnesium oxide)) and 0.8 wt. % of cross-linking
chemicals (0.3 wt. % of Zinkweiss Rotsiegel; (zinc oxide), 0.3 wt.
% of Rhenogran.RTM. MTT (3-methyl-thiazolidinethione-2, 0.2 wt. %
of Vulkacit.RTM. ZBEC/C (zinc dibenzyldithiocarbamate)). After
renewed homogenization, the mixture can be drawn out as a sheet on
a roller or calandered. Production of the radiation-absorbing
articles was achieved by vulcanizing at temperatures between
150.degree. C. and 170.degree. C. and is complete in 30
minutes.
TABLE-US-00028 Name Additive content [k.sub.A] Density
[.rho..sub.p] Sample 68 80 wt. % 3.50 g/cm.sup.3
TABLE-US-00029 Name Thickness [d.sub.p] Bulk covering [m.sub.A]
Sample 68 2 mm 0.56 g/cm.sup.2 Sample 69 4 mm 1.12 g/cm.sup.2
Sample 70 6 mm 1.68 g/cm.sup.2 Sample 71 8 mm 2.24 g/cm.sup.2
Sample 72 10 mm 2.80 g/cm.sup.2 m.sub.A = k.sub.A .rho..sub.p
d.sub.p Bulk covering = proportion by weight of mixture in the
sample .times. density of the sample .times. thickness of the
sample
Example 20
Testing the Radiation Protection Properties
[0237] Step wedges were produced from the 20 cm.times.20 cm.times.2
mm rubber sheets by gluing them together. Areas with 2, 4, 6, 8 and
10 mm thickness were produced. The step wedges were exposed to
X-radiation of beam quality U=100 kV, eff. filtering 2.5 mm Al,
tungsten direct current X-ray tube for 480 s and the X-ray films
were evaluated densitometrically. In the following, the results of
this exposure of step wedges made from the radiation-absorbing
materials in this invention are given and in fact compared with
step wedges made of lead. The same degree of blackening means the
same degree of absorption of radiation. Less blackening indicates a
better screening effect.
TABLE-US-00030 Thickness Bulk covering Blackening Name [d.sub.p]
[m.sub.A] (relative units) Sample 68 2 mm 0.56 g/cm.sup.2 2.22
Sample 69 4 mm 1.12 g/cm.sup.2 0.43 Sample 70 6 mm 1.68 g/cm.sup.2
0.32 Sample 71 8 mm 2.24 g/cm.sup.2 0.32 Sample 72 10 mm 2.80
g/cm.sup.2 0.32
[0238] The lead samples used for calibration and comparison samples
were prepared from lead foils of grade S1 with a thickness of 0.1
mm. Step wedges like those for the samples were prepared from the
lead foils. The test region covered the lead equivalents from 0.1
to 1.0 mm.
TABLE-US-00031 Bulk covering Blackening Name Thickness [d.sub.p]
[m.sub.A] (relative units) Sample 73 (lead 0.1 mm 0.11 g/cm.sup.2
6.50 comparison) Sample 74 (lead 0.2 mm 0.23 g/cm.sup.2 6.50
comparison) Sample 75 (lead 0.3 mm 0.34 g/cm.sup.2 6.50 comparison)
Sample 76 (lead 0.4 mm 0.45 g/cm.sup.2 4.67 comparison) Sample 77
(lead 0.5 mm 0.56 g/cm.sup.2 3.38 comparison) Sample 78 (lead 0.6
mm 0.68 g/cm.sup.2 2.50 comparison) Sample 79 (lead 0.7 mm 0.80
g/cm.sup.2 1.88 comparison) Sample 80 (lead 0.8 mm 0.91 g/cm.sup.2
1.43 comparison) Sample 81 (lead 0.9 mm 1.03 g/cm.sup.2 1.15
comparison) Sample 82 (lead 1.0 mm 1.14 g/cm.sup.2 0.97
comparison)
[0239] For a comparable bulk covering of 1.12 g/cm.sup.2 and 1.04
g/cm.sup.2 the degree of blackening for sample 69 was 0.43, whereas
the comparison sample (sample 81 (lead comparison)) allowed much
more radiation to pass through and had a degree of blackening of
1.15. Less blackening indicates a better screening effect. That
means in practice: in order to produce the same radiation
protection effect as lead, a smaller bulk covering is required,
which can be achieved by a smaller thickness or a lower degree of
filling by the samples. This leads to a weight saving and thus to
increased wearer comfort for the items produced therefrom such as
e.g. X-ray aprons.
[0240] Even after replacing half of the mixture according to the
invention with the less effective screening substance barium
sulfate, the screening effect still remains high enough for this
mixture according to the invention to be better than lead.
Example 21
[0241] The rubber sheets prepared with the mixture according to the
present invention from example 20 exhibited the following
mechanical properties:
TABLE-US-00032 Method Sample 68 Tear strength, MPa: DIN 53504 6.2
Elongation at break, %: DIN 53504 674 Modulus 100%, MPa: DIN 53504
2.9 Modulus 200%, MPa: DIN 53504 3.6 Modulus 300%, MPa: DIN 53504
3.8 Hardness, Shore A: DIN 53505 66
Example 22
a) Raw Materials Used and their Composition
[0242] A mixture according to the invention was prepared as
radiation protection from the following components:
TABLE-US-00033 Proportion in the Name mixture Gadolinium oxide 45
wt. % Tungsten powder 55 wt. %
b) Preparation of the Mixture According to the Invention
[0243] Before use, the gadolinium concentrate and tungsten powder
were dried for 2 hours at a temperature of 120.degree. C. and
classified through sieve 063 (tungsten through sieve 016). Then the
three components were mixed for 1.5 hours in a tumble mixer.
[0244] A white, free-flowing, lump-free powder was obtained as a
mixture according to the invention.
Example 23
[0245] 66.1 wt. % of the previously prepared mixture according to
the present invention from example 22 is added in 2-3 portions to
27.5 wt. % of a synthetic elastomer (EVM ethylene/vinylacetate
copolymer with about 40 wt. % of ethylene and about 60 wt. % of
vinyl acetate) (Levapren.RTM. 600 HV) and homogenized on a roller
system or internal mixer. Then the following were added: 2.8 wt. %
of Regal.RTM. SRF carbon black from Rhein Chemie, 0.8 wt. % of
Rhenogran.RTM. P-50 anti-hydrolysis agent from Rhein-Chemie,
polycarbodiimide, 0.4 wt. % of Rhenofit.RTM. DDA styrenated
diphenylamine from Rhein-Chemie, 0.3 wt. % of stearic acid, 1.0 wt.
% of Rhenofit.RTM. TAC triallyl cyanurate from Rhein-Chemie and 1.1
wt. % of Polydispersion.RTM. T
.alpha.,.alpha.'-bis-(tert-butylperoxy)-diisopropylbenzene,
peroxide cross-linker from Rhein-Chemie. After renewed
homogenization, the mixture can be drawn out as a sheet on a roller
or calandered. Production of the radiation-absorbing articles was
achieved after pressure forming or calandering by vulcanizing at
temperatures between 150.degree. C. and 170.degree. C. and was
completed in 30 minutes.
[0246] Samples of the mixture according to the invention from
example 22 and the rubber were prepared by the process described
above:
TABLE-US-00034 Name Additive content Sample 83 66.1 wt. %
Example 24
[0247] 79.6 wt. % of the previously prepared mixture according to
the invention from example 22 are added in 2-3 portions to 16.6 wt.
% of a synthetic elastomer (EVM ethylene/vinylacetate copolymer
with about 40 wt. % of ethylene and about 60 wt. % of vinyl
acetate) (Levapren.RTM. 600 HV) and homogenized on a roller system
or internal mixer. Then the following were added: 1.6 wt. % of
Regal.RTM. SRF carbon black from Rhein Chemie, 0.5 wt. % of
Rhenogran.RTM. P-50 anti-hydrolysis agent from Rhein-Chemie,
polycarbodiimide, 0.2 wt. % of stabilizer, Rhenofit.RTM. DDA
styrenated diphenylamine from Rhein-Chemie, 0.2 wt. % of stearic
acid, 0.6 wt. % of Rhenofit.RTM. TAC triallyl cyanurate from
Rhein-Chemie and 0.7 wt. % of Polydispersion.RTM. T
.alpha.,.alpha.'-bis-(tert-butylperoxy)-diisopropylbenzene,
peroxide cross-linker from Rhein-Chemie. After renewed
homogenization, the mixture could be drawn out as a sheet on a
roller or calandered. Production of the radiation-absorbing
articles was achieved after pressure forming or calandering by
vulcanizing at temperatures between 150.degree. C. and 170.degree.
C. and was completed in 30 minutes.
[0248] Samples of the mixture according to the invention from
example 22 and the rubber were prepared by the process described
above:
TABLE-US-00035 Name Additive content Sample 84 79.6 wt. %
Example 25
[0249] The rubber sheets prepared with the mixture according to the
invention exhibited the following mechanical properties:
TABLE-US-00036 Method Sample 83 Sample 84 Tear strength, MPa: DIN
53504 8.9 6.6 Elongation at break, %: DIN 53504 243 222 Modulus
200%, MPa: DIN 53504 2.7 3.4 Hardness, Shore A: DIN 53505 63 75
[0250] The rubber sheets prepared with the mixture according to the
invention exhibited very good mechanical strengths with the degrees
of filling tested. That leads to the conclusion that the
cross-linking reaction proceeds largely unaffected by the mixture
according to the present invention.
Example 26
[0251] Non-reinforced PA 6 (Durethen.RTM. B31F, a commercial
product from Bayer AG) was processed to give a homogeneous compound
with the mixture according to the invention from example 7 with the
addition of 0.2 wt. % of mould release agent (Licowax.RTM. E
flakes; a commercial product from Clariant AG, an ester of montanic
acid with an acid value of 15-20, a saponification value of 145-165
and a density of 1.01-1.03 g/cm.sup.3) by compounding on a
twin-shaft extruder (ZSK 25 from Werner & Pfleiderer) at a bulk
temperature of about 245.degree. C. and with a throughput of 7
kg/h. The melt was then spun off via a belt pull-off and
granulated.
[0252] The granules obtained were processed on an injection molding
machine of the Arburg 320-210-500 type under conventional molding
composition conditions (bulk temperature of about 270.degree. C.,
mould temperature 80.degree. C.) to give standard test specimens
for mechanical testing and to give 1 mm thick sheets (105
mm.times.150 mm).
[0253] The following molding compositions and samples were prepared
from the mixture according to the invention and the thermoplastic
material using the process described above:
TABLE-US-00037 Name Additive content [k.sub.A] Density
[.rho..sub.p] Sample 85 50 wt. % 1.903 g/cm.sup.3
TABLE-US-00038 Name Thickness [d.sub.p] Bulk covering [m.sub.A]
Sample 85 2 mm 0.19 g/cm.sup.2 Sample 86 4 mm 0.38 g/cm.sup.2
Sample 87 6 mm 0.57 g/cm.sup.2 Sample 88 8 mm 0.76 g/cm.sup.2
Sample 89 10 mm 0.95 g/cm.sup.2 m.sub.A = k.sub.A .rho..sub.p
d.sub.p Bulk covering = proportion by weight of mixture in the
sample .times. density of the sample .times. thickness of the
sample
Example 27
Testing the Radiation Protection Properties
[0254] Step wedges were produced from the 105 mm.times.150
cm.times.1 mm polyamide sheets by gluing them together. Areas with
2, 4, 6, 8 and 10 mm thickness were produced. The step wedges were
exposed to X-radiation of beam quality U=100 kV, eff. filtering 2.5
mm Al, tungsten direct current X-ray tube for 960 s and the X-ray
films were evaluated densitometrically. In the following, the
results of this exposure of step wedges made from the
radiation-absorbing materials in this invention are given and in
fact compared with step wedges made of lead. The same degree of
blackening means the same degree of absorption of radiation. Less
blackening indicates a better screening effect
TABLE-US-00039 Thickness Bulk covering Blackening Name [d.sub.p]
[m.sub.A] (relative units) Sample 85 2 mm 0.19 g/cm.sup.2 6.5
Sample 86 4 mm 0.38 g/cm.sup.2 6.5 Sample 87 6 mm 0.57 g/cm.sup.2
3.18 Sample 88 8 mm 0.76 g/cm.sup.2 1.74 Sample 89 10 mm 0.95
g/cm.sup.2 0.88
[0255] The lead samples used for calibration and comparison samples
were prepared from lead foils of grade S1 with a thickness of 0.1
mm. Step wedges like those for the samples were prepared. The test
region covered the lead equivalents from 0.1 to 1.0 mm.
TABLE-US-00040 Bulk covering Blackening Name Thickness [d.sub.p]
[m.sub.A] (relative units) Sample 90 (lead 0.1 mm 0.11 g/cm.sup.2
6.5 comparison) Sample 91 (lead 0.2 mm 0.23 g/cm.sup.2 6.5
comparison) Sample 92 (lead 0.3 mm 0.34 g/cm.sup.2 6.5 comparison)
Sample 93 (lead 0.4 mm 0.45 g/cm.sup.2 6.5 comparison) Sample 94
(lead 0.5 mm 0.56 g/cm.sup.2 5.18 comparison) Sample 95 (lead 0.6
mm 0.68 g/cm.sup.2 3.75 comparison) Sample 96 (lead 0.7 mm 0.80
g/cm.sup.2 2.82 comparison) Sample 97 (lead 0.8 mm 0.91 g/cm.sup.2
2.11 comparison) Sample 98 (lead 0.9 mm 1.03 g/cm.sup.2 1.61
comparison) Sample 99 (lead 1.0 mm 1.14 g/cm.sup.2 1.29
comparison)
[0256] For the same bulk covering of 0.56 g/cm.sup.2, the degree of
blackening for sample 85 was 3.18, whereas the comparison sample
(sample 94 (lead comparison)) allowed much more radiation to pass
through and had a degree of blackening of 5.18. Less blackening
indicates a better screening effect. That means that for the same
radiation protection effect as lead, a smaller bulk covering is
required, which can be achieved by a smaller thickness or a lower
degree of filling by the samples. This leads to a weight
saving.
Example 28
[0257] Mechanical data for sample 83.
TABLE-US-00041 Standard Units Sample 85 Bending stress 3.5% ISO 178
[MPa] 113 Outer fiber strain ISO 178 [%] 5.1 Bending strength ISO
178 [MPa] 122 Bending modulus ISO 178 [MPa] 3930 Breaking stress
ISO 527 [MPa] 69 Elongation at break ISO 527 [%] 6 Tensile modulus
ISO 527 [MPa] 4150 Izod impact strength ISO 180 1U [kJ/m.sup.2]
49
[0258] The mechanical properties for sample 85 are of the order of
magnitude which could be expected for e.g. conventional
mineral-filled polyamide 6 compounds. The solution viscosity of the
PA6 was not altered by the compounding process, i.e. the
thermoplastic molding composition filled with the mixture according
to the invention did not lead to degradation or building up of the
polymer.
Example 29
Components Used
[0259] A.1) Graft rubber of 50 wt. % polybutadiene with an average
particle diameter (d.sub.50) of 0.35 .mu.m onto which were graft
polymerized 36.5 wt. % of styrene and 13.5 wt. % of acrylonitrile
in emulsion. [0260] A.2) Graft rubber of 50 wt. % polybutadiene
with an average particle diameter (d.sub.50) of 0.1 .mu.m onto
which were graft polymerized 36.5 wt. % of styrene and 13.5 wt. %
of acrylonitrile in emulsion. [0261] A.3) Styrene/acrylonitrile
(SAN)=72:28-copolymer with an average molecular weight of about
85,000, prepared by solution polymerisation. [0262] B) 60 parts by
wt. of the mixture according to the invention from example 7.
Preparing and Testing the Molding Compositions
[0263] The individual components A.1) to A.3) and B) are mixed in
an internal compounder, together with 2 parts by wt. of ethylene
bisstearylamide and 0.2 parts by wt. of silicone oil, at
200.degree. C. to 230.degree. C. for 3 to 5 minutes and then
granulated.
[0264] The granules are compressed at 190.degree. C. (compression
time with no pressure 2 min; compression time at 200 bar 8 min) to
give 1 mm thick sheets. The sample specimens required are prepared
by sawing out or punching out.
TABLE-US-00042 Name Additive content [k.sub.A] Density
[.rho..sub.p] Sample 100 60 wt. % 2.141 g/cm.sup.3
TABLE-US-00043 Name Thickness [d.sub.p] Bulk covering [m.sub.A]
Sample 100 2 mm 0.26 g/cm.sup.2 Sample 101 4 mm 0.51 g/cm.sup.2
Sample 102 6 mm 0.77 g/cm.sup.2 Sample 103 8 mm 1.03 g/cm.sup.2
Sample 104 10 mm 1.28 g/cm.sup.2 m.sub.A = k.sub.A .rho..sub.p
d.sub.p Bulk covering = proportion by weight of mixture in the
sample .times. density of the sample .times. thickness of the
sample
Example 30
Testing the Radiation Protection Properties
[0265] Step wedges were produced from the 100 mm.times.100
cm.times.1 mm ABS sheets by glueing them together. Areas with 2, 4,
6, 8 and 10 mm thickness were produced. The step wedges were
exposed to X-radiation of beam quality U=150 kV, eff. filtering 2.5
mm Al, tungsten direct current X-ray tube for 240 s and the X-ray
films were evaluated densitometrically. In the following, the
results of this exposure of step wedges made from the
radiation-absorbing materials in this invention are given and in
fact compared with step wedges made of lead. The same degree of
blackening means the same degree of absorption of radiation. Less
blackening indicates a better screening effect.
TABLE-US-00044 Blackening Name Thickness [d.sub.p] Bulk covering
[m.sub.A] (relative units) Sample 100 2 mm 0.26 g/cm.sup.2 6.50
Sample 101 4 mm 0.51 g/cm.sup.2 2.46 Sample 102 6 mm 0.77
g/cm.sup.2 1.12 Sample 103 8 mm 1.03 g/cm.sup.2 0.69 Sample 104 10
mm 1.28 g/cm.sup.2 0.52
[0266] The lead samples used for calibration and comparison samples
were prepared from lead foils of grade S1 with a thickness of 0.1
mm. Step wedges like those for the samples were prepared. The test
region covered the lead equivalents from 0.1 to 1.0 mm.
TABLE-US-00045 Bulk covering Blackening Name Thickness [d.sub.p]
[m.sub.A] (relative units) Sample 105 (lead 0.1 mm 0.11 g/cm.sup.2
6.50 comparison) Sample 106 (lead 0.2 mm 0.23 g/cm.sup.2 6.50
comparison) Sample 107 (lead 0.3 mm 0.34 g/cm.sup.2 6.50
comparison) Sample 108 (lead 0.4 mm 0.45 g/cm.sup.2 4.60
comparison) Sample 109 (lead 0.5 mm 0.56 g/cm.sup.2 3.18
comparison) Sample 110 (lead 0.6 mm 0.68 g/cm.sup.2 2.20
comparison) Sample 111 (lead 0.7 mm 0.80 g/cm.sup.2 1.55
comparison) Sample 112 (lead 0.8 mm 0.91 g/cm.sup.2 1.17
comparison) Sample 113 (lead 0.9 mm 1.03 g/cm.sup.2 0.76
comparison) Sample 114 (lead 1.0 mm 1.14 g/cm.sup.2 0.72
comparison)
[0267] For the same bulk covering of 0.51 g/cm.sup.2, the degree of
blackening for sample 99 was 2.46, whereas the comparison sample
(sample 109 (lead comparison)) allowed much more radiation to pass
through and had a degree of blackening of 3.18. Less blackening
indicates a better screening effect. That means that for the same
radiation protection effect as lead, a smaller bulk covering is
required, which can be achieved by a smaller thickness or a lower
degree of filling by the samples. This leads to a weight
saving.
Example 31
[0268] Mechanical data for sample 100 from example 29.
[0269] Tensile tests at room temperature using 2 mm thick rods with
shoulders, with a crosshead speed of 5 mm/min.
[0270] Sheet penetration test at room temperature, based on DIN 53
443 (differently from the DIN, the mandrel with a 20 mm diameter
was combined with a guide tube with a 40 mm diameter), using 2 mm
round discs with a diameter of 60 mm. Rate of fall 3 m/sec; energy
delivered 13.3 J.
TABLE-US-00046 Standard Units Sample 85 Tensile test ISO 527
Tensile E modulus ISO 527 MPa 2650 Yield stress ISO 527 MPa 27
Elongation ISO 527 % 1.7 Elongation at break ISO 527 % 2 Sheet
penetration test Analogous to DIN 53 443 Energy absorbed Nm 0.01
Deformation mm 0.38 Maximum force N 63
[0271] The mechanical properties for sample 100 are of the order of
magnitude which could be expected for e.g. conventional
mineral-filled ABS compounds. The viscosity of the ABS was not
altered by the compounding process, i.e. the thermoplastic moulding
composition filled with the mixture according to the invention did
not lead to degradation or building up of the polymer.
Example 32
Starting Components/Specimens
[0272] A so-called one-component system is used as a polyurethane
system for example 32. This is a formulation which contains all the
starting components required to prepare a polyurethane
(polyisocyanate, polyol mixture, additives). These systems are
described in DE-A 3 230 757; page 16, line 60 to page 19, line 51
and DE-A 3 727 128; column 13, line 28 to, column 16, line 45.
[0273] A high-melting, finely divided (average particle size 5-25
.mu.m) solid diisocyanate is used as the polyisocyanate, which is
deactivated by a thin polyurea envelope. This deactivation makes
the formulation storage-stable up to about 50.degree. C. By heating
to temperatures of at least 100.degree. C., the deactivation is
broken down and the polyisocyanate released can react with the
polyol components present.
N,N'-di-(4-methyl-3-isocyanatophenyl)urea is preferably used as the
solid diisocyanate, the preparation of which is described in DE-A 3
826 447.
[0274] A storage-stable polyurethane one-component system of the
type mentioned above is offered by Bayer AG as a trial product
under the product name VP.PU 50EL08, this being composed of a
polyol mixture and the solid diisocyanate mentioned above. This
system has a viscosity of about 13 Pa*s at room temperature and is
cured by heating to about 100-150.degree. C.
[0275] The following components were admixed with this final
mixture (example 32a) in the amounts given in Table 1: [0276] 1.
the mixture according to the present invention [0277] 2. an
aliphatic polyamine (Jeffamine.RTM. T 403, a liquid which is
colourless at room temperature, from the Huntsman Co., a
polyethertriamine started on a trimethylolpropane (TMP) base with
5-6 moles of propylene oxide per mole of TMP, amine content 6
milliequivalents/g) to compensate for the elevated mechanical
stress during incorporation of the additives by mixing into the
one-component VP.PU 50EL08 system, [0278] 3. catalyst
Octa-Soligen.RTM. Pb 30-31 (lead(II)-2-ethylhexanoate from
Borchers, 40789 Monheim) to adapt the rate of curing to the filler
content.
[0279] The additives mentioned were added to the VP.PU 50EL08 and
carefully blended with a slow-running toothed ring stirrer at up to
35.degree. C. Then this mixture was carefully stirred for about 15
minutes at up to 40.degree. C. in an evacuated flask (20 mbar) in
order to remove stirred-in air and to homogenise the mixture
(example 32b).
[0280] The evacuated mixtures, each slightly warmed (to about
40.degree. C.), were applied to a flat metal 20*20 cm mould with a
layer thickness of about 3 mm and, after levelling, cured for 3
hours in a heating cupboard at 140.degree. C.
[0281] The mechanical characteristics of the sample sheets prepared
were determined and the blackening curves were recorded and
evaluated.
Example 33
Mechanical Values of the Specimens
[0282] Table 1 shows the composition of the samples from examples
32a and 32b and the mechanical characteristics of the cured
elastomer samples.
TABLE-US-00047 TABLE 1 Tensile Elong. at Amount of Conc. of
strength break Tear prop. Jeffamin inorg. inorg. Hardness [MPa] [%]
resist. Elasticity VPPU (pts. T403 additives additives Pb 30-31
Viscosity [Shore A] DIN DIN [kN/m] [%] Ex. 50EL08 by wt.) (pts.
wt.) (pts. wt.) (pts. wt.) added [Pa * s] DIN 53505 53504 53504 DIN
53515 DIN 53512 32a Pt. 126 100 0 0.0 13 73 6.9 220 15.3 44 32b Pt.
126 100 0.15 60 37.4 0.40 30 84 9.3 280 18.5 36
[0283] The table shows that the mixture according to the invention,
as is conventional and known for standard fillers, increases the
mechanical values for hardness, tensile strength, elongation at
break and tear propagation resistance and reduces the elasticity
and thus does not have any unacceptable or unexpected negative
effects on the elastomer properties.
Bulk Covering of the Specimens
[0284] The elastomer from example 32b had a density of 1.537
g/cm.sup.3.
[0285] Specimens with different thicknesses were prepared by gluing
several films together. The following bulk coverings were produced,
depending on the thickness of the sample:
TABLE-US-00048 Name Thickness [d.sub.p] Bulk covering [m.sub.A]
Sample 115 3.1 mm 0.18 g/cm.sup.2 Sample 116 6.8 mm 0.39 g/cm.sup.2
Sample 117 10.3 mm 0.59 g/cm.sup.2 Sample 118 13.8 mm 0.79
g/cm.sup.2 Sample 119 17.6 mm 1.01 g/cm.sup.2 (Bulk covering =
proportion by weight of mixture in the sample .times. density of
the sample .times. thickness of the sample: m.sub.A = k.sub.A
.rho..sub.p d.sub.p)
Example 34
Testing the Radiation Protection Properties
[0286] Step wedges were produced from the 200 mm.times.200
cm.times.ca. 3 mm PU sheets by glueing them together. Areas with
the thicknesses given in the table were produced. The step wedges
were exposed to X-radiation of beam quality U=150 kV, eff.
filtering 2.5 mm Al, tungsten direct current X-ray tube for 240 s
and the X-ray films were evaluated densitometrically. In the
following, the results of this exposure of step wedges made from
the radiation-absorbing materials in this invention are given and
in fact compared with step wedges made of lead. The same degree of
blackening means the same degree of absorption of radiation. Less
blackening indicates a better screening effect.
TABLE-US-00049 Bulk covering Blackening Name Thickness [d.sub.p]
[m.sub.A] (relative units) Sample 115 3.1 mm 0.18 g/cm.sup.2 6.50
Sample 116 6.8 mm 0.39 g/cm.sup.2 4.67 Sample 117 10.3 mm 0.59
g/cm.sup.2 2.33 Sample 118 13.8 mm 0.79 g/cm.sup.2 1.28 Sample 119
17.6 mm 1.01 g/cm.sup.2 0.84
[0287] The lead samples used for calibration and comparison samples
were prepared from lead foils of grade S1 with a thickness of 0.1
mm. Step wedges like those for the samples were prepared. The test
region covered the lead equivalents from 0.1 to 1.0 mm.
TABLE-US-00050 Bulk covering Blackening Name Thickness [d.sub.p]
[m.sub.A] (relative units) Sample 120 (lead 0.1 mm 0.11 g/cm.sup.2
6.50 comparison) Sample 121 (lead 0.2 mm 0.23 g/cm.sup.2 6.50
comparison) Sample 122 (lead 0.3 mm 0.34 g/cm.sup.2 6.50
comparison) Sample 123 (lead 0.4 mm 0.45 g/cm.sup.2 4.60
comparison) Sample 124 (lead 0.5 mm 0.56 g/cm.sup.2 3.18
comparison) Sample 125 (lead 0.6 mm 0.68 g/cm.sup.2 2.20
comparison) Sample 126 (lead 0.7 mm 0.80 g/cm.sup.2 1.55
comparison) Sample 127 (lead 0.8 mm 0.91 g/cm.sup.2 1.17
comparison) Sample 128 (lead 0.9 mm 1.03 g/cm.sup.2 0.76
comparison) Sample 129 (lead 1.0 mm 1.14 g/cm.sup.2 0.72
comparison)
[0288] For the same bulk covering of 0.59 g/cm.sup.2, the degree of
blackening for sample 115 was 2.33, whereas the comparison sample
(sample 124 (lead comparison)) allowed much more radiation to pass
through and had a degree of blackening of 3.18. Less blackening
indicates a better screening effect. That means in practice: in
order to produce the same radiation protection effect as lead, a
smaller bulk covering is required, which can be achieved by a
smaller thickness or a lower degree of filling by the samples. This
leads to a weight saving.
[0289] In the table given below, the bulk covering required for a
desired blackening effect (=reciprocal of screening effect) for
lead and for the filler used in example 32b are shown. In the
right-hand column it can be seen that the bulk covering required
for the filler from example 32b, depending on the degree of
screening required, is 5-25% less than when using lead.
TABLE-US-00051 Bulk covering required for a defined blackening
effect Bulk covering Blackening lead example 32b difference* 4.0
0.497 0.366 26.4 3.0 0.581 0.493 15.1 2.0 0.717 0.641 10.6 1.0
0.954 0.912 4.4 *with respect to lead in [%]
Example 35
Comparative
[0290] The mixture with the following composition is prepared from
rare earths and tungsten powder using the process described in
example 1:
TABLE-US-00052 Rare earths Proportion in the mixture
La.sub.2O.sub.3 13.5% CeO.sub.2 27% Nd.sub.2O.sub.3 7.5%
Gd.sub.2O.sub.3 25% W 27.3%
[0291] Before use, the rare earths and the tungsten powder are
dried for 2 hours at a temperature of 120.degree. C. and screened
through sieve 063 (tungsten through sieve 016). Then the two
components are mixed in a tumble mixer for 2 hours.
Example 36
Comparative
[0292] 66.1 wt. % of the previously prepared mixture (according to
example 35) were added in 2-3 portions to 27.5 wt. % of Natural
Rubber.RTM. TSR 5 and homogenised on a roller or in an internal
mixer. Then the following were added: 2.8 wt. % of Enerthene.RTM.
1849-1, a naphthenic process oil from BP, 0.4 wt. % of
Vulkanox.RTM. BKF, as antioxidant from Bayer AG, 0.4 wt. % of
Vulkanox.RTM. MB, an antioxidant from Bayer AG, 0.8 wt. % of zinc
oxide RS, 0.6 wt. % of stearic acid, 0.4 wt. % of Vulkacit.RTM. CZ,
a vulcanisation accelerator from Bayer AG, 0.1 wt. % of
Vulkacit.RTM. D, a vulcanisation accelerator from Bayer AG and 0.8
wt. % of sulfinur Rhenocure.RTM. IS 60/G 75. After renewed
homogenisation, the mixture could be drawn out into a sheet on a
roller or calandered. Production of the radiation-absorbing
articles was achieved after pressure forming or calandering by
vulcanising at temperatures between 150.degree. C. and 170.degree.
C. and was completed in 30 minutes.
[0293] Samples of the mixture from example 35 and the rubber were
prepared by the process described above:
TABLE-US-00053 Name Additive content [k.sub.A] Density
[.rho..sub.p] Sample 130 66.1 wt. % 2.281 g/cm.sup.3
TABLE-US-00054 Name Thickness [d.sub.p] Bulk covering [m.sub.A]
Sample 130 2 mm 0.30 g/cm.sup.2 Sample 131 4 mm 0.60 g/cm.sup.2
Sample 132 6 mm 0.90 g/cm.sup.2 Sample 133 8 mm 1.21 g/cm.sup.2
Sample 134 10 mm 1.51 g/cm.sup.2 m.sub.A = k.sub.A .rho..sub.p
d.sub.p Bulk covering = proportion by weight of mixture in the
sample .times. density of the sample .times. thickness of the
sample
Example 37
Testing the Radiation Protection Properties
[0294] Step wedges were produced from the 20 mm.times.20 cm.times.2
mm rubber sheets by glueing them together. Areas with 2, 4, 6, 8
and 10 mm thickness were produced. The step wedges were exposed to
X-radiation of beam quality U=100 kV, eff. filtering 2.5 mm Al,
tungsten direct current X-ray tube for 960 s and the X-ray films
were evaluated densitometrically. In the following, the results of
this exposure of step wedges made from the radiation-absorbing
materials in this invention are given and in fact compared with
step wedges made of lead. The same degree of blackening means the
same degree of absorption of radiation. Less blackening indicates a
better screening effect.
TABLE-US-00055 Bulk covering Blackening Name Thickness [d.sub.p]
[m.sub.A] (relative units) Sample 130 2 mm 0.30 g/cm.sup.2 6.50
Sample 131 4 mm 0.60 g/cm.sup.2 2.98 Sample 132 6 mm 0.90
g/cm.sup.2 0.85 Sample 133 8 mm 1.21 g/cm.sup.2 0.38 Sample 134 10
mm 1.51 g/cm.sup.2 0.29
[0295] The lead samples used for calibration and comparison samples
were prepared from lead foils of grade S1 with a thickness of 0.1
mm. Step wedges like those for the samples were prepared from the
lead foils. The test region covered the lead equivalents from 0.1
to 1.0 mm.
TABLE-US-00056 Bulk covering Blackening Name Thickness [d.sub.p]
[m.sub.A] (relative units) Sample 135 (lead 0.1 mm 0.11 g/cm.sup.2
6.50 comparison) Sample 136 (lead 0.2 mm 0.23 g/cm.sup.2 6.50
comparison) Sample 137 (lead 0.3 mm 0.34 g/cm.sup.2 6.50
comparison) Sample 138 (lead 0.4 mm 0.45 g/cm.sup.2 6.50
comparison) Sample 139 (lead 0.5 mm 0.56 g/cm.sup.2 6.11
comparison) Sample 140 (lead 0.6 mm 0.68 g/cm.sup.2 4.23
comparison) Sample 141 (lead 0.7 mm 0.80 g/cm.sup.2 3.07
comparison) Sample 142 (lead 0.8 mm 0.91 g/cm.sup.2 2.27
comparison) Sample 143 (lead 0.9 mm 1.03 g/cm.sup.2 1.76
comparison) Sample 144 (lead 1.0 mm 1.14 g/cm.sup.2 1.43
comparison)
[0296] In the bulk covering range tested, from 0.5 g/cm.sup.2 to
1.4 g/cm.sup.2, although the degree of blackening for samples 130
to 134 is lower than for lead, it is considerably higher than for
samples 20 to 24 according to the invention (example 9). Less
blackening indicates a better screening effect. Samples 20 to 24
according to the invention screen better than lead and better than
samples 130 to 134 not according to the invention.
Example 38
[0297] A mixture with the following composition is prepared from
rare earths and tungsten powder using the process described in
example 1:
TABLE-US-00057 Proportion in the mixture Rare earths according to
the invention Gd.sub.2O.sub.3 55% Sn 30% W 15%
[0298] Before use, the rare earths and the tungsten and tin powders
are dried for 2 hours at a temperature of 120.degree. C. and
screened through sieve 063 (tungsten through sieve 016). Then the
three components are mixed in a tumble mixer for 2 hours.
Example 39
[0299] 66.2 wt. % of the previously prepared mixture according to
the invention (according to example 38) were added in 2-3 portions
to 27.5 wt. % of Natural Rubber.RTM. TSR 5 and homogenised on a
roller or in an internal mixer. Then the following were added: 2.8
wt. % of Enerthene.RTM. 1849-1, a naphthenic process oil from BP,
0.4 wt. % of Vulkanox.RTM. BKF, as antioxidant from Bayer AG, 0.4
wt. % of Vulkanox.RTM. MB, an antioxidant from Bayer AG, 0.8 wt. %
of zinc oxide RS, 0.6 wt. % of stearic acid, 0.4 wt. % of
Vulkacit.RTM. CZ, a vulcanisation accelerator from Bayer AG, 0.1
wt. % of Vulkacit.RTM. D, a vulcanisation accelerator from Bayer AG
and 0.8 wt. % of sulfur Rhenocure.RTM. IS 60/G 75. After renewed
homogenisation, the mixture could be drawn out into a sheet on a
roller or calandered. Production of the radiation-absorbing
articles was achieved after pressure forming or calandering by
vulcanising at temperatures between 150.degree. C. and 170.degree.
C. and was completed in 30 minutes.
[0300] Samples of the mixture according to the invention from
example 38 and the rubber were prepared by the process described
above:
TABLE-US-00058 Name Additive content [k.sub.A] Density
[.rho..sub.p] Sample 145 66.1 wt. % 2.300 g/cm.sup.3
TABLE-US-00059 Name Thickness [d.sub.p] Bulk covering [m.sub.A]
Sample 145 2 mm 0.30 g/cm.sup.2 Sample 146 4 mm 0.61 g/cm.sup.2
Sample 147 6 mm 0.91 g/cm.sup.2 Sample 148 8 mm 1.22 g/cm.sup.2
Sample 149 10 mm 1.52 g/cm.sup.2 m.sub.A = k.sub.A .rho..sub.p
d.sub.p Bulk covering = proportion by weight of mixture in the
sample .times. density of the sample .times. thickness of the
sample
Example 40
Testing the Radiation Protection Properties
[0301] Step wedges were produced from the 20 mm.times.20 cm.times.2
mm rubber sheets by glueing them together. Areas with 2, 4, 6, 8
and 10 mm thickness were produced. The step wedges were exposed to
X-radiation of beam quality U=150 kV, eff. filtering 2.5 mm Al,
tungsten direct current X-ray tube for 120 s and the X-ray films
were evaluated densitometrically. In the following, the results of
this exposure of step wedges made from the radiation-absorbing
materials in this invention are given and in fact compared with
step wedges made of lead. The same degree of blackening means the
same degree of absorption of radiation. Less blackening indicates a
better screening effect.
TABLE-US-00060 Thickness Bulk covering Blackening Name [d.sub.p]
[m.sub.A] (relative units) Sample 145 2 mm 0.30 g/cm.sup.2 4.30
Sample 146 4 mm 0.61 g/cm.sup.2 1.58 Sample 147 6 mm 0.91
g/cm.sup.2 0.81 Sample 148 8 mm 1.22 g/cm.sup.2 0.51 Sample 149 10
mm 1.52 g/cm.sup.2 0.37
[0302] The lead samples used for calibration and comparison samples
were prepared from lead foils of grade S1 with a thickness of 0.1
mm. Step wedges like those for the samples were prepared from the
lead foils. The test region covered the lead equivalents from 0.1
to 1.0 mm.
TABLE-US-00061 Bulk covering Blackening Name Thickness [d.sub.p]
[m.sub.A] (relative units) Sample 150 (lead 0.1 mm 0.11 g/cm.sup.2
6.50 comparison) Sample 151 (lead 0.2 mm 0.23 g/cm.sup.2 6.50
comparison) Sample 152 (lead 0.3 mm 0.34 g/cm.sup.2 5.40
comparison) Sample 153 (lead 0.4 mm 0.45 g/cm.sup.2 3.68
comparison) Sample 154 (lead 0.5 mm 0.56 g/cm.sup.2 2.65
comparison) Sample 155 (lead 0.6 mm 0.68 g/cm.sup.2 1.98
comparison) Sample 156 (lead 0.7 mm 0.80 g/cm.sup.2 1.39
comparison) Sample 157 (lead 0.8 mm 0.91 g/cm.sup.2 1.04
comparison) Sample 158 (lead 0.9 mm 1.03 g/cm.sup.2 0.83
comparison) Sample 159 (lead 1.0 mm 1.14 g/cm.sup.2 0.71
comparison)
Example 41
Comparative
a) Raw Materials Used and their Composition
[0303] A mixture not according to the invention was prepared from
the following components:
TABLE-US-00062 Proportion in the mixture not Name according to the
invention Gadolinium oxide 75 wt. % Tungsten powder 5 wt. % Tin
powder 20 wt. %
b) Preparation of the Inorganic Radiation Protection Mixture
[0304] Before use, the gadolinium oxide and the tungsten powder
were dried for 2 hours at a temperature of 120.degree. C. and
screened through sieve 063 (tungsten through sieve 016). Then the
three components are mixed in a tumble mixer for 1.5 hours.
[0305] A white, free-flowing, lump-free powder was obtained as the
mixture not according to the invention.
Example 42
Comparative
[0306] 66.1 wt. % of the previously prepared mixture not according
to the invention from example 41 are added in 2-3 portions to 27.5
wt. % of a synthetic elastomer (EVM ethylene/vinylacetate copolymer
with about 40 wt. % of ethylene and about 60 wt. % of vinyl
acetate) (Levapren.RTM. 600 HV) and homogenised on a roller system
or internal mixer. Then the following were added: 2.8 wt. % of
Regal.RTM. SRF carbon black from Rhein-Chemie, 0.8 wt. % of
Rhenogran.RTM. P-50 anti-hydrolysis agent from Rhein-Chemie,
polycarbodiimide, 0.4 wt. % of Rhenofits DDA styrenated
diphenylamine from Rhein-Chemie, 0.3 wt. % of stearic acid, 1.0 wt.
% of Rhenofit.RTM. TAC triallyl cyanurate from Rhein-Chemie and 1.1
wt. % of Polydispersion.RTM. T
.alpha.,.alpha.'-bis-(tert-butylperoxy)-diisopropylbenzene,
peroxide cross-linker from Rhein-Chemie. After renewed
homogenisation, the mixture could be drawn out as a sheet on a
roller or calandered. Production of the radiation-absorbing
articles was achieved after pressure forming or calandering by
vulcanizing at temperatures between 150.degree. C. and 170.degree.
C. and was completed in 30 minutes.
[0307] Samples of the mixture not according to the invention from
example 41 and the rubber were prepared by the process described
above:
TABLE-US-00063 Name Additive content [k.sub.A] Density
[.rho..sub.p] Sample 160 66.1 wt. % 2.42 g/cm.sup.3
Example 43
Testing the Radiation Protection Properties
[0308] Step wedges were produced from the 20 cm.times.20 cm.times.2
mm rubber sheets by glueing them together. Areas with 2, 4, 6, 8
and 10 mm thickness were produced. The step wedges were exposed to
X-radiation of beam quality U=150 kV, eff. filtering 2.5 mm Al,
tungsten direct current X-ray tube for 120 s and the X-ray film was
evaluated densitometrically. In the following, the results of this
exposure of step wedges made from the radiation-absorbing materials
in this invention are given and in fact compared with step wedges
made of lead. The same degree of blackening means the same degree
of absorption of radiation. Less blackening indicates a better
screening effect.
TABLE-US-00064 Thickness Bulk covering Blackening Name [d.sub.p]
[m.sub.A] (relative units) Sample 160 2 mm 0.39 g/cm.sup.2 4.38
Sample 161 4 mm 0.77 g/cm.sup.2 2.01 Sample 162 6 mm 1.16
g/cm.sup.2 1.11 Sample 163 8 mm 1.54 g/cm.sup.2 0.70 Sample 164 10
mm 1.93 g/cm.sup.2 0.47
[0309] The lead samples used for calibration and comparison samples
were prepared from lead foils of grade S1 with a thickness of 0.1
mm. Step wedges like those for the samples were prepared from the
lead foils. The test region covered the lead equivalents from 0.1
to 1.0 mm.
TABLE-US-00065 Bulk covering Blackening Name Thickness [d.sub.p]
[m.sub.A] (relative units) Sample 165 (lead 0.1 mm 0.11 g/cm.sup.2
6.50 comparison) Sample 166 (lead 0.2 mm 0.23 g/cm.sup.2 6.50
comparison) Sample 167 (lead 0.3 mm 0.34 g/cm.sup.2 4.55
comparison) Sample 168 (lead 0.4 mm 0.45 g/cm.sup.2 3.27
comparison) Sample 169 (lead 0.5 mm 0.56 g/cm.sup.2 2.42
comparison) Sample 170 (lead 0.6 mm 0.68 g/cm.sup.2 1.83
comparison) Sample 171 (lead 0.7 mm 0.80 g/cm.sup.2 1.28
comparison) Sample 172 (lead 0.8 mm 0.91 g/cm.sup.2 1.02
comparison) Sample 173 (lead 0.9 mm 1.03 g/cm.sup.2 0.81
comparison) Sample 174 (lead 1.0 mm 1.14 g/cm.sup.2 0.70
comparison)
[0310] In the bulk covering range tested, from 0.5 g/cm.sup.2 to
1.4 g/cm.sup.2, the degree of blackening for samples 160 to 164 not
according to the invention is higher than for lead and is also
considerably higher than for samples 145 to 149 according to the
invention (example 39) or 20 to 24 (example 9). Less blackening
indicates a better screening effect. Samples 145 to 149 and samples
20 to 24 according to the invention screen better than lead and
much better than samples 160 to 164 not according to the
invention.
Example 44
Comparative
[0311] The mixture not according to the invention with the
following composition is prepared from rare earths and tungsten
powder and tin using the process described in example 1:
TABLE-US-00066 Rare Proportion in the mixture not earths according
to the invention Gd.sub.2O.sub.3 35% Sn 60% W 5%
[0312] Before use, the rare earths and the tungsten and tin powders
are dried for 2 hours at a temperature of 120.degree. C. and
screened through sieve 063 (tungsten through sieve 016). Then the
three components are mixed in a tumble mixer for 2 hours.
Example 45
Comparative
[0313] 66.1 wt. % of the previously prepared mixture not according
to the invention (according to example 44) were added in 2-3
portions to 27.5 wt. % of Natural Rubber.RTM. TSR 5 and homogenised
on a roller or in an internal mixer. Then the following were added:
2.8 wt. % of Enerthene.RTM. 1849-1, a naphthenic process oil from
BP, 0.4 wt. % of Vulkanox.RTM. BKF, as antioxidant from Bayer AG,
0.4 wt. % of Vulkanox.RTM. MB, an antioxidant from Bayer AG, 0.8
wt. % of zinc oxide RS, 0.6 wt. % of stearic acid, 0.4 wt. % of
Vulkacit.RTM. CZ, a vulcanisation accelerator from Bayer AG, 0.1
wt. % of Vulkacit.RTM. D, a vulcanisation accelerator from Bayer AG
and 0.8 wt. % of sulfinur Rhenocure.RTM. IS 60/G 75. After renewed
homogenisation, the mixture could be drawn out into a sheet on a
roller or calandered. Production of the radiation-absorbing
articles was achieved after pressure forming or calandering by
vulcanising at temperatures between 150.degree. C. and 170.degree.
C. and was completed in 30 minutes.
[0314] The following samples of the inorganic radiation protection
mixture according to the invention from example 44 and the rubber
were prepared by the process described above:
TABLE-US-00067 Name Additive content [k.sub.A] Density
[.rho..sub.p] Sample 175 66.1 wt. % 2.272 g/cm.sup.3
TABLE-US-00068 Name Thickness [d.sub.p] Bulk covering [m.sub.A]
Sample 175 2 mm 0.30 g/cm.sup.2 Sample 176 4 mm 0.60 g/cm.sup.2
Sample 177 6 mm 0.90 g/cm.sup.2 Sample 178 8 mm 1.20 g/cm.sup.2
Sample 179 10 mm 1.50 g/cm.sup.2 m.sub.A = k.sub.A .rho..sub.p
d.sub.p Bulk covering = proportion by weight of mixture in the
sample .times. density of the sample .times. thickness of the
sample
Example 46
Testing the Radiation Protection Properties
[0315] Step wedges were produced from the 20 cm.times.20 cm.times.2
mm rubber sheets by glueing them together. Areas with 2, 4, 6, 8
and 10 mm thickness were produced. The step wedges were exposed to
X-radiation of beam quality U=150 kV, eff. filtering 2.5 mm Al,
tungsten direct current X-ray tube for 120 s and the X-ray films
were evaluated densitometrically. In the following, the results of
this exposure of step wedges made from the radiation-absorbing
materials in this invention are given and in fact compared with
step wedges made of lead. The same degree of blackening means the
same degree of absorption of radiation. Less blackening indicates a
better screening effect.
TABLE-US-00069 Thickness Bulk covering Blackening Name [d.sub.p]
[m.sub.A] (relative units) Sample 175 2 mm 0.30 g/cm.sup.2 4.52
Sample 176 4 mm 0.60 g/cm.sup.2 1.88 Sample 177 6 mm 0.90
g/cm.sup.2 1.08 Sample 178 8 mm 1.20 g/cm.sup.2 0.72 Sample 179 10
mm 1.50 g/cm.sup.2 0.51
[0316] The lead samples used for calibration and comparison samples
were prepared from lead foils of grade S1 with a thickness of 0.1
mm. Step wedges like those for the samples were prepared from the
lead foils. The test region covered the lead equivalents from 0.1
to 1.0 mm.
TABLE-US-00070 Bulk covering Blackening Name Thickness [d.sub.p]
[m.sub.A] (relative units) Sample 180 (lead 0.1 mm 0.11 g/cm.sup.2
6.50 comparison) Sample 181 (lead 0.2 mm 0.23 g/cm.sup.2 6.50
comparison) Sample 182 (lead 0.3 mm 0.34 g/cm.sup.2 5.40
comparison) Sample 183 (lead 0.4 mm 0.45 g/cm.sup.2 3.68
comparison) Sample 184 (lead 0.5 mm 0.56 g/cm.sup.2 2.65
comparison) Sample 185 (lead 0.6 mm 0.68 g/cm.sup.2 1.98
comparison) Sample 186 (lead 0.7 mm 0.80 g/cm.sup.2 1.39
comparison) Sample 187 (lead 0.8 mm 0.91 g/cm.sup.2 1.04
comparison) Sample 188 (lead 0.9 mm 1.03 g/cm.sup.2 0.83
comparison) Sample 189 (lead 1.0 mm 1.14 g/cm.sup.2 0.71
comparison)
[0317] In the bulk covering range from 0.5 g/cm.sup.2 to 1.4
g/cm.sup.2, although the degree of blackening for samples 175 to 79
is lower than for lead, it is higher than for samples 20 to 24
according to the invention (example 9). Less blackening indicates a
better screening effect. Samples 20 to 24 according to the
invention screen better than lead and much better than samples 175
to 179 not according to the invention.
Example 47
[0318] 66.1 wt. % of the previously prepared mixture according to
the present invention (from example 7) were added in 2-3 portions
to 27.5 wt. % of Natural Rubber.RTM. TSR 5 and homogenised on a
roller or in an internal mixer. Then the following were added: 2.8
wt. % of Enerthene.RTM. 1849-1, a naphthenic process oil from BP,
0.4 wt. % of Vulkanox.RTM. BKF, as antioxidant from Bayer AG, 0.4
wt. % of Vulkanox.RTM. MB, an antioxidant from Bayer AG, 0.8 wt. %
of zinc oxide RS, 0.6 wt. % of stearic acid, 0.4 wt. % of
Vulkacit.RTM. CZ, a vulcanisation accelerator from Bayer AG, 0.1
wt. % of Vulkacit.RTM. D, a vulcanisation accelerator from Bayer AG
and 0.8 wt. % of sulfur Rhenocure.RTM. IS 60/G 75. After renewed
homogenisation, the mixture could be drawn out into a sheet on a
roller or calandered; Production of the radiation-absorbing
articles was achieved after pressure forming or calandering by
vulcanising at temperatures between 150.degree. C. and 170.degree.
C. and was completed in 30 minutes.
[0319] The following samples were prepared from the mixture
according to the invention from example 7 and the rubber using the
process described above:
TABLE-US-00071 Name Additive content [k.sub.A] Sample 190 66.1 wt.
%
Example 48
[0320] 79.6 wt. % of the previously prepared mixture according to
the present invention (from example 7) were added in 2-3 portions
to 16.6 wt. % of Natural Rubber.RTM. TSR 5 and homogenised on a
roller or in an internal mixer. Then the following were added: 1.7
wt. % of Enerthene.RTM. 1849-1, a naphthenic process oil from BP,
0.25 wt. % of Vulkanox.RTM. BKF, as antioxidant from Bayer AG, 0.25
wt. % of Vulkanox.RTM. MB, an antioxidant from Bayer AG, 0.5 wt. %
of zinc oxide RS, 0.3 wt. % of stearic acid, 0.23 wt. % of
Vulkacit.RTM. CZ, a vulcanisation accelerator from Bayer AG, 0.1
wt. % of Vulkacit.RTM. D, a vulcanisation accelerator from Bayer AG
and 0.5 wt. % of sulfur Rhenocure.RTM. IS 60/G 75. After renewed
homogenisation, the mixture could be drawn out into a sheet on a
roller or calandered. Production of the radiation-absorbing
articles was achieved after pressure forming or calandering by
vulcanising at temperatures between 150.degree. C. and 170.degree.
C. and was completed in 30 minutes.
[0321] The following samples were prepared from the mixture
according to the invention from example 7 and the rubber using the
process described above:
TABLE-US-00072 Name Additive content [k.sub.A] Sample 191 79.6 wt.
%
Example 49
[0322] The rubber sheets prepared with the mixture according to the
example (example 7) exhibited the following mechanical
properties:
TABLE-US-00073 Method Sample 190 Sample 191 Tear strength, MPa: DIN
53504 12.3 9.3 Elongation at break, %: DIN 53504 703 497 Hardness,
Shore A: DIN 53505 41 62
[0323] The rubber sheets produced with the mixture according to the
invention had very good mechanical strengths with the degrees of
filling tested. That leads to the conclusion that the cross-linking
reaction proceeds largely unaffected by the mixture according to
the invention.
[0324] Although the invention has been described in detail in the
foregoing for the purpose of illustration, it is to be understood
that such detail is solely for that purpose and that variations can
be made therein by those skilled in the art without departing from
the spirit and scope of the invention except as it may be limited
by the claims.
* * * * *