A turquoise is impregnated with a monomeric diester having two spaced apart polymerizable monoolefinic groups, said diester having a plurality of supplemental hydrophillic groups and a volatility corresponding to a boiling point within a range from about 150.degree. C to about 300.degree. C. Whatever moisture may be sorbed on the turquoise is encapsulated within the plastic during the in-situ polymerization, inasmuch as such sorbed moisture can associate with such supplemental hydrophillic groups having an affinity for water. The dimethacrylate ester of triethylene glycol has two supplemental ether groups which tend to have affinity for water. Thus the monomer is sorbed on surfaces displacing any sorbed moisture in the internal pores or fissures in the turquoise, whereby the impregnation of the turquoise is feasible without critical control of vacuum drying and/or related preparatory steps. Thus one overcomes prior difficulties connected with drying the turquoise, evacuating the turquoise, preconditioning the turquoise in a warm water bath and the multi-stage treatment for polymerization. The diester thus impregnated into the turquoise can be adequately polymerized to a weather resistant composite by catalytic, thermal, or radiation initiation of the polymerization. The heat of polymerization is so small that gems are not impaired thereby.

FIELD OF INVENTION 
This invention relates to the upgrading of gems such as turquoise by 
formation of plastic in the fissures and pores of a composite. 
PRIOR ART 
A turquoise is a gem having a shade which can vary from robin's egg blue to 
a dark blue and may have a significant greenish tint. The composition of 
turquoise is variable and can be thought of as a complex hydrated 
silicate. Compositions lacking the desirable characteristics of gem grade 
but having a somewhat similar composition are sometimes called chalk 
turquoise. Heretofore, there have been methods whereby a 
turquoise-plastic-composite has been prepared by polymerizing after 
appropriate impregnation of the chalk turquoise with monomeric styrene. 
Such prior art process included the steps of drying the chalk turquoise, 
subjecting the thoroughly dried chalk turquoise to a very low vacuum to 
further dry and degas the porous chalk turquoise, allowing liquid styrene 
to flow into the evacuated chamber containing the evacuated degassed chalk 
turquoise, thereby vacuum impregnating the chalk turquoise with the 
monomeric styrene, removing the stone from the liquid styrene and 
preconditioning it in a warm water bath to partially polymerize the 
styrene further polymerizing the styrene in a hot water bath, separating 
each of the stones to prevent any adhesion of stones, wrapping each stone 
in aluminum foil, and heating the aluminum foil covered precursor in an 
oven to complete polymerization. 
In the oven there is often a significant amount of volatilization of the 
organic component so that the turquoise-plastic-composite does not contain 
as much solidified plastic as desired. The process is also disadvantageous 
because of the spotty appearance of the composite attributable to the 
uneven wetting of the stones by the monomer during the impregnation step. 
Such prior art process has been of interest because the color and 
appearance of the turquoise-plastic-composite is sufficiently close to 
that of top grade gem turquoise to permit the use of the composites in 
jewelry. 
Such prior art process has required a significant amount of specialized 
apparatus even for small scale operation. There has been a continuing 
demand for a process of making attractive weatherable 
turquoise-plastic-composite by a simpler process. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, a turquoise-plastic-composite is 
prepared by impregnating a turquoise with a liquid monomer having a 
plurality of hydrophillic groups so that the monomer tends to be sorbed 
along the same interstices of the turquoise in which any water is sorbed. 
Because of this propensity of the monomer to be sorbed into the same zones 
wherein water is sorbed, the impregnation can proceed more readily than 
the impregnation of the hydrophobic type of monomer such as styrene. The 
monomer must have a volatility corresponding to that of a liquid having a 
boiling point within a range from about 150.degree. C to about 300.degree. 
C. Its vapor pressure at room temperature must be low enough to avoid 
significant loss of the monomer by volatilization and the polymerization 
should not volatilize monomer. The monomer is a diester having two 
monofunctional unsaturated groups esterified to a difunctional molecule. 
If the unsaturated compound is an alcohol such as allyl alcohol or 
crotanyl alcohol, then the difunctional component is a difunctional 
carboxylic acid having a plurality of hydrophillic groups in the molecule. 
Gluconoc acid, a tetrahydroxy dicarboxylic adipic acid, and tartaric acid 
are examples of difunctional acids having water affinity groups, sometimes 
called hydrophillic groups. The diether formed by symmetrical addition of 
2 mols of gylcolic acid to acetylene to form the ethylene glycol diether 
of gylcolic acid also has a plurality of water affinity groups as a 
difunctional acid.

DESCRIPTION OF EMBODIMENTS 
The nature of the invention if further clarified by reference to a 
plurality of examples. 
EXAMPLE 1 
An assortment of about 500 pounds of chalk turquoise stones varying in size 
from about the size of rice grains to the size of goose eggs are deposited 
as an approximately single layer partially covering the bottom of a porous 
woven wire basket. The stones are subjected to a series of cleaning steps 
to remove the dirt therefrom. The cleaned stones are dried. The dried 
stone in such porous basket is transferred to an impregnation chamber and 
there immersed in a liquid monomer consisting essentially of the 
dimethracrylate diester of triethylene ether glycol. Such impregnation is 
continued for an interval of about 50 minutes during most of which a 
nitrogen pressure of about 7 atmospheres is maintained for urging the 
monomer into the pores. 
The thus impregnated stones contain from about 10% to about 30% diester. 
Such impregnated stones are transferred to a tumbling drum type of sealed 
canister in a polymerization apparatus featuring the use of a cobalt-60 
source of gamma radiation. The canister is directed from the loading zone 
above the water surface through a predetermined path which includes a 
lowering of the canister into a submerged radiation zone. Each canister is 
advanced along a path in which the series of canisters are successively in 
close proximity to a plurality of tubes containing cobalt-60 isotope, 
thereby being subjected to gamma radiation. 
Factory personnel are protected from the gamma radiation by reason of the 
pool of water and the positioning of the tubes of cobalt-60 at a safe 
depth beneath the water. A depth of from about 20 to about 40 feet, such 
as 26 feet, is suitable for a radiation panel. 
The advancing conveyor system moves at a speed such that the radiation 
dosage for the canister passing through the polymerization zone is about 
250,000 rads per hour, which is deemed appropriate for achieving the 
desired degree of polymerization in the stones tumbling in the rotating 
canister. Thus the canister is subjected to such cobalt-60 radiation 
during an interval which desirably is 1.5 hours but which can be within 
the range from about 0.25 to 4 hours. 
The in-situ polymerization of the dimethracrylate of triethylene ether 
glycol generates heat, thereby raising the temperature of the turquoise 
rocks in which the solid polymethacrylate is formed. The moisture content 
of the turquoise is encapsulated within such solid polymethacrylate so 
that the turquoise-plastic-composite is stabilized throughout all of the 
variations in humidity which weather can provide. 
The water in the pool has a propensity toward promoting generally 
isothermal conditions in the polymerization zone. Some of the heat 
generated by polymerization is eventually transferred from the rocks to 
the canister to the water in the pool. The heat transfer rates to the 
water are slow enough that the turquoise rocks are noticeably warmed by 
the polymerization step. The increase in temperature of the turquoise in 
the polymerization is not sufficient to be harmful to the turquoise. 
The rotating sealed tumbling drum type of canister advances along the 
conveyor system and eventually advances to the top of the pool and to 
above the surface of the pool to a discharge zone so that the canister can 
be removed from the conveyor system. The warm turquoise rocks are removed 
from the canister and are inspected for quality control. 
The dimethracrylate of triethylene ether glycol undergoes shrinkage during 
polymerization. The solid tends to shrink into the pores of the turquoise 
with minimized propensity toward laking or exuding from the surface of the 
composite. The polymerization process generates heat which tends to 
stimulate molecules to migrate. Accordingly, when the polymerization is 
induced by reason of heat, the front zone of polymerization tends to 
advance as the heat transfer advances. An important advantage of the use 
of radiation for inducing polymerization for in-situ polymerized 
composites is the greater uniformity of the penetration of the radiation 
toward the center of the composite. However, the in-situ polymerization of 
impregnated turquoise stones in a sealed tumbling drum having a nitrogen 
atmosphere can yield useful products when the diesters of the present 
invention are thermally and/or catalytically polymerized. Radiation 
polymerization is preferred because the quality of the product gems is 
superior when radiation polymerization is utilized. 
EXAMPLE 2 
A series of stainless steel tubes each about 1 meter long are filled with 
granular cobalt having an enriched concentration of cobalt-60. The tubes 
were sealed and were assembled as a panel having dimensions of about 1 by 
2 meters. The panel was positioned at the bottom of a pool of water, the 
pool having a depth of about 8 meters and dimensions of about 15 by 7 
meters. 
A reversible conveyor system was adapted to shift containers scheduled for 
radiation from a loading/unloading zone down to the submerged zone 
immediately above the radiation panel for a controlled interval and 
thereafter returned to the loading/unloading zone. The conveyor system 
permits remote control of the container while in the radiation zone while 
still protecting personnel from the effects of the radiation from the 
cobalt-60 panel. 
A tumbling drum having a diameter of about 36 centimeters is provided with 
means for maintaining a sealed nitrogen atmosphere and for slowly rotating 
a charge of about 20 kg of granular material for the preparation of 
composites of a generally granular size, whereby the propensities toward 
adhesion between particles is decreased during the polymerization step. 
Granular size is deemed to extend from about the size of a grain of rice 
to the size of an orange, but in the processing of the turquoise 
composites the upper size limit is generally not more than about the size 
of a goose egg. 
A batch of about 20 kg. of chalk turquoise stones having a size from about 
the size of a pea to the size of a silver dollar and averaging about the 
size of a 25.cent. coin is washed to remove dirt and contaminants and 
thereafter rinsed and dried. The dried stones are transferred to a 
pressurized impregnating chamber in which nitrogen pressure at about 7 
atmospheres helps to force the dimethracrylate of tetrapropylene ether 
glycol into the pores of the chalk turquoise stones. 
The thus impregnated stones are transferred to the tumbling drum, which is 
rotated to prevent the stones from adhering to each other during the 
polymerization in the radiation zone. By reason of the rotation, each 
stone receives approximately the same amount of radiation from the 
submerged panel. The diester is polymerized to a weather resistant solid 
more readily than a monomer such as methyl methracrylate. Moreover, the 
heat of polymerization is somewhat less by reason of the fact that 
tetrapropylene ether glycol has a molecular weight more than twice that of 
methyl alcohol. 
The precursor particles contained diester amounting to from about 10% to 
about 30% of the initial weight of the turquoise stones. Thus the amount 
of impregnate is significantly less than is customary in connection with 
the preparation of wood composites following the procedures prescribed in 
Bell U.S. Pat. No. 3,808,030 employing a similar radiation panel and 
similar pool of water. 
The duration of the radiation treatment can be from about 0.5 to about 4 
hours and is desirably about 2 hours. Thus the amount of radiation 
necessary for preparing a turquoise-plastic-composite is less and the 
duration is shorter than described for the preparation of high quality 
wood-plastic composites. 
After the tumbling turquoise stones have been radiated with about 250,000 
rads per hour for about 2 hours, they are withdrawn from the radiation 
zone and lifted above the surface of the pool to the transfer zone and 
unloaded from the tumbling drum. Although the chalk turquoise stones are 
nearly white, the plastic composites have an attractive blue green 
appearance making them suitable for use as turquoise gems. Moreover, the 
turquoise impregnated with plastic is weatherproof and can withstand all 
types of conditions to which a turquoise might ordinarily be encountered 
without damage to the advantageous gem properties of the composite. 
EXAMPLE 3 
A batch of turquoise-plastic-composites is prepared following the general 
procedure of Example 2 and using as the impregnating solution a commercial 
grade of the dimethracrylate ester of triethylene ether glycol containing 
about 35 parts per million of BHT inhibitor. The BHT inhibitor is 
sometimes called butylate hydroxide toluene. The presence of the inhibitor 
in the monomer permits the liquid to have a greater shelf life than would 
otherwise be feasible. However, the conditions involving the chain 
reaction of free radicals for the polymerization in the zone influenced by 
the cobalt-60 panel promotes the polymerization of the diester at a rate 
which does not scorch the plastic product. The radiation rate of 250,000 
rads per hour is maintained for about 2 hours. The heat dissipation rates 
are adequate so that the final temperature of the tumbled product having 
the solidified polymethracrylate is low enough that the impregnated 
polymerized composites can be handled without discomfort. 
EXAMPLES 4- 9 
Attractively colored turquoise gems are prepared following the general 
procedure of Example 3 but employing liquid diesters containing inhibitors 
in amounts of the general magnitude from about 20 to about 60 parts per 
million and polymerizing the composites during a radiation of from about 
0.5 to about 4 hours using cobalt-60 radiation providing from about 50,000 
to about 500,000 rads per hour. Data relating to the diester and 
polymerization conditions are shown in the accompanying Table 1. 
Table 1 
__________________________________________________________________________ 
Example 
diester formula 
__________________________________________________________________________ 
1 triethylene glycol dimethacrylate 
##STR1## 
2 tetrapropylene glycol dimethacrylate 
##STR2## 
3 triethylene glycol dimethacrylate 
##STR3## 
4 diallyl gluconate H.sub.2 CCHCH.sub.2 O.sub.2 C(CHOH).sub.4 
CO.sub.2 CH.sub.2 CHCH.sub.2 
5 tetraethylene glycol dimethacrylate 
##STR4## 
6 tripropylene glycol diacrylate 
##STR5## 
7 diallyl tartrate H.sub.2 CCHCH.sub.2 O.sub.2 C (CHOH).sub.2 
CO.sub.2 CH.sub.2 CHCH.sub.2 
8 dicrotonyl trihydroxy glutarate 
H.sub.2 CCHCH.sub.2 CH.sub.2 O.sub.2 C 
(CHOH).sub.3 CO.sub.2 CH.sub.2 CH.sub.2 CHCH.sub. 
2 
9 diallyl diglycolate of ethylene ether 
H.sub.2 CCHCH.sub.2 O.sub.2 CCH.sub.2 OCH.sub.2 
CH.sub.2 OCH.sub.2 CO.sub.2 CH.sub.2 CHCH.sub.2 
concn. 
inh. 
Example ppm rad/hour hours 
__________________________________________________________________________ 
1 250,000 1.5 
2 250,000 2 
3 35 250,000 2 
4 20 300,000 2 
5 60 500,000 0.25 
6 40 50,000 4 
7 20 350,000 1.5 
8 50 400,000 3 
9 45 200,000 0.5 
__________________________________________________________________________ 
EXAMPLE 10 
A batch of chalk turquoise stones are cleaned, washed, dried, and 
impregnated at 7 atmospheres with the liquid dimethracylate of triethylene 
ether glycol. In addition to the 35 ppm of BHT, the diester contained 0.5% 
of 70% tertiary butyl hydroperoxide which is mixed with the diester just 
prior to impregnation. At room temperature such tertiary butyl 
hydroperoxide in such concentration is substantially inert. When 
impregnated turquoise stones are heated in the tumbling drum to a 
temperature of about 100.degree. C, the tertiary butyl hydroperoxide is a 
very effective catalyst promoting rapid polymerization of the composite. 
The tumbling drum is desirably rotated in a hot water bath for about 2 
hours to achieve the desired degree of polymerization when the thermal 
catalytic approach is employed instead of the radiation polymerization. 
Gems are customarily subjected to visual inspection on an individual gem 
basis. Some of the turquoise-plastic-composites resulting from the 
catalytic thermal polymerization reaction are of substandard quality and 
cannot be marketed in competition with the superior quality gems. The 
diester does polymerize far more satisfactorily than a methyl methracylate 
or a styrene so that the attractiveness of the thermal catalytic 
polymerization might be dependent upon establishing any market for the 
substandard gems instead of dealing with them as a waste product involving 
waste disposal costs. 
It can be noted that the diesters of Examples 1, 2, 3, 5 and 6 correspond 
to the formula: 
##STR6## 
in which each R is independently selected from hydrogen or a methyl group 
except that each alkoxy group has not more than one methyl group and in 
which n has a value of 3 or 4. It can also be noted that the diesters of 
Examples 4, 7 and 8 correspond to the formula 
##STR7## 
in which m is 1 or 2 and in which q is 2, 3 or 4. The diester of Example 
9, corresponding to the formula: 
##STR8## 
as well as the two previously discussed generic formulas are all monomeric 
diesters formed by the esterification of two moles of a monoolefinic 
monomer and one mole of a difunctional reactant having a plurality of 
supplemental hydrophillic groups of the class consisting of hydroxy groups 
and ether groups, said diester having a volatility corresponding to a 
boiling point within the range from 150.degree. C. to 300.degree. C. 
Various modifications are possible without departing from the scope of the 
appended claims.