Low moisture thixotropic agents, methods and uses

Thioxotropic Fuller's earth clay minerals which are structurally double silica chains linked together through oxygen to form double-ribbed sheets held by aluminum and/or magnesium in octahedral coordination in an amphibole chain are vacuum dried and admixed with a stabilizing fluid, e.g., silicone fluid, to result in new, low moisture content thixotropic agents. The mineral products thus produced are superior thixotropes when compounded in plastics such as plastisols, adhesive sealants, coatings and other organic binder systems which are heat set or heat cured or moisture cured, and compliance coatings. The methods involve reducing the moisture content of Fuller's earth clay, e.g., attapulgite, by (1) heating it under vacuum at an elevated temperature, preferably between 100.degree. C. and 300.degree. C., or (2) heating it at an elevated temperature, preferably between 100.degree. C. and 350.degree. C., and adding a stabilizing fluid, or (3) heating it under vacuum at an elevated temperature, preferably below 300.degree. C. and adding a stabilizing fluid, to preserve its low moisture properties.

TECHNICAL FIELD 
This invention relates to plastics and coatings comprising thixotropic 
agents and more particularly, but not by way of limitation, to methods of 
producing Fuller's earth clays without destroying the thixotropic 
properties of the clays by reducing the moisture content to a level which 
permits the clay to be used as a thixotrope in plastics, including 
plastisols and adhesive sealants, coatings and other organic binder 
systems which are heat set or heat cured or moisture cured, and compliance 
coatings. 
BACKGROUND ART 
The production of compounded plastics requires the use of low moisture 
content thixotropic agents to achieve satisfactory film integrity. For the 
purposes of the present invention the term "compounded plastic" is used to 
comprehend within its scope various forms and kinds of plastics which 
would include but is not limited to plastisols, adhesive sealants, 
coatings including compliance coatings and moisture cured coatings, and 
other organic binder systems which are heat set or heat cured or moisture 
cured. 
Thixotropic agents are used in the production of compounded plastics which 
are applied to metal or other materials, for example, the coatings found 
on the wire baskets in a dishwasher or refrigerator. The use of the 
thixotrope permits the uniform application of the plastisol film to the 
object which is to be coated and the retention of that relatively uniform 
film during curing. In heat set (i.e., plastics which cannot be reformed) 
and heat cured (i.e., plastics which may be reformed by reheating) 
applications, the moisture content of the plastisols must be low enough to 
prevent the excessive release of moisture upon heating. Excessive amounts 
of moisture released during heating can cause bubbles to form in the 
plastisol coating, which causes reduced film continuity (a coating which 
contains voids), localized areas where the film does not adhere to the 
surface coated, and a less desirable appearance. Also, small quantities of 
moisture released during curing, although producing no visable blemish, 
can affect film integrity thereby causing, for example, reduced corrosion 
protection. 
Changing requirements for coatings, including moisture cured (i.e., coating 
compositions that remain in the liquid state indefinitely when stored in a 
sealed container but are cured to the desired hardness when applied to the 
intended object, by moisture present in the atmosphere), heat set and heat 
cured primer and top-coat finishes, and higher solids compliance coatings 
to meet volatile organic compounds (VOC's) emissions standards present the 
coating formulations chemist with major constraints. The presence of free 
water in the pigments and other components limits the effectiveness of 
some recommended substitute compliance coatings. The problem of flow 
behavior of high solids coatings has not been completely solved. 
Additionally, poor humidity resistance of heat set or heat cured coatings 
or the premature activation of moisture cured coatings is the result of 
free water present in the pigments selected for the formulation. 
Previously, the mineral asbestos processed by Johns-Manville Corporation, 
Union Carbide Corporation and others served as an effective thixotrope for 
plastisols, adhesive sealants, coatings and other organic binder systems. 
Thixotropic asbestos is processed to result in low moisture, typically 
less than 2% free moisture content. Asbestos had been considered a 
preferred cost effective thixotrope in these applications. Environmental 
and health considerations, as well as governmental regulations, limit its 
use and create a need for a suitable substitute thixotrope for use in heat 
set plastisol formulations and thermoplastic formulations, and compliance 
coatings. 
Pyrogenic silica such as "CAB-0-SIL" by Cabot Corporation has been used as 
a substitute thixotrope for asbestos in plastisols, adhesive sealants, and 
other organic binder systems which are heat set or heat cured. The high 
cost of pyrogenic silica, however, creates an economic limitation on its 
use. Further, with time, pyrogenic silica is likely to absorb moisture, 
reducing its desirability as a thixotrope in, for example, plastisols. 
Many clays, notably kaolinite clays, are used extensively as fillers in 
plastics. In such applications, the clays are used not as a thixotrope, 
but to achieve reduced shrinkage during curing, to obscure the fiber 
pattern of glass reinforcement and to increase resistance to chemical 
action and weathering. 
Fuller's earth clays from the group consisting of sepiolite, palygorskite 
and attapulgite are effective thixotropes. Attapulgite, hydrated magnesium 
silicate clay processed by Engelhard Co., Floridin Co. and others is a 
particularly effective thixotrope. Thixotropic attapulgite and sepiolite 
are widely used as drilling mud in the drilling of oil wells. As 
commercially prepared, thixotropic attapulgite contains typically 10% to 
15% moisture at 100.degree. C. Undesirable quantities of the moisture 
contained in typically prepared thixotropic Fuller's earth is released 
when used as a thixotropic agent in plastics such as plastisols and 
adhesive sealants, and other organic binder systems which are heat set, or 
moisture or heat cured. When typically prepared attapulgite is used in 
plastisols, for example, which are heat cured at about 100.degree. C., the 
moisture in the attapulgite volatilizes and deforms the structure of the 
plastisol, reducing its film continuity. This moisture release limits or 
precludes the use of typical attapulgite as a thixotropic agent for most 
heat set or heat cured applications. 
Thixotropic grade attapulgite is processed commercially in carefully 
controlled drying ovens. The literature teaches that drying temperatures 
above approximately 400.degree. C. agglomerate the mineral particles and 
destroy the ability to disperse the clay in the form of colloidally active 
ultimate particles. The inventors do not know with certainty, but suspect 
that at this high temperature, refluxing of the water back into the clay 
structure is prevented, causing sintering of the attapulgite. 
Bentonite clays treated with amine surfactants can become suitable 
thixotropic agents when the treated bentonite is mixed with an alcohol, 
water or other hydroxyl contributing agent by the user. However, bentonite 
so treated is not a suitable thixotrope for heat set or heat cured 
plastisols, or compliance coatings, because of the excessive moisture 
content. Release of the moisture from the treated bentonite clays in heat 
set or heat cured plastisols results in an undesirable film having a 
deformed surface, reduced continuity, voids and localized areas of 
nonadhesion. 
Thus, the present invention produces an economical and environmentally safe 
alternate to the principal thixotropic agent previously used, asbestos. 
DISCLOSURE OF THE INVENTION 
The present invention may be briefly described as a thixotropic grade 
Fuller's earth clay and methods for producing such thixotrope, that is 
suitable for use in plastics, including plastisols and adhesive sealants, 
coatings and other organic binder systems which are heat set or heat cured 
or moisture cured, and compliance coatings, as well as compounded plastics 
comprising such thixotropes. As disclosed in above cited U.S. Pat. No. 
4,966,871, one such method comprises drawing a vacuum on attapulgite and 
heating it at a temperature sufficient to drive the free moisture from the 
attapulgite without destroying its thixotropic properties. The thixotropic 
agent is dried to a desired moisture content and then removed from the 
vacuum. 
Another method disclosed in above cited application Ser. No. 489,065 
comprises drying the attapulgite below about 350.degree. C. for a time 
sufficient to reduce the water content to the desired level, followed by 
intimately admixing the intermediate dried product with a silicone fluid. 
We have discovered yet another method to further reduce the free moisture 
from Fuller's earth without destroying its thixotropic properties, for use 
where thixotropes with a moisture content below about 2% are required. 
Such method comprises drying Fuller's earth in a vacuum at a temperature 
sufficient to drive the free water from the Fuller's earth without 
destroying its thixotropic properties, and intimately admixing with a 
fluid capable of preserving the low moisture condition, e.g., silicone 
fluid. 
The art of compounding plastics is well developed and covers a myriad of 
possible formulations. In general a plastic resin, e.g., polyvinyl 
chloride, is compounded with plasticizers, filler and stabilizers. The 
plastic resin may be one which is heat set or heat cured. The selection of 
a plasticizer is governed by the properties desired in the final product. 
Properties commonly affecting plasticizer selection are thermal 
conductivity, electric conductivity, light stability, color stability, 
corrosion resistance, flame retardance and flexibility. Suitable 
plasticizers include dioctyl phthalate, diisooctyl phthalate, diisodecyl 
phthalate, epoxidized oils, esters of carboxylic acids or phosphoric acid, 
polyglycols, ethers and sulfonamides. Appropriate stabilizers are used to 
inhibit degradation of the plastic by oxygen and ultra-violet radiation, 
and include salicylic acid, 2-hydroxy-benzophenone, lead salts, barium, 
cadmium, zinc and stearic acid. Bonding agents that are useful for the 
present invention are those that promote adhesion to the substrate and 
include triethylene glycol dimethacrylate. 
The strength, durability and color of plastics are varied by the 
incorporation of fillers such as pigments, clays and glass fibers. 
Thixotropic agents are added to plastics or coatings in order to achieve 
the efficient and uniform application of plastic films during manufacture, 
for example, in the production of plastic coated wire baskets and shelves 
in home appliances. 
The art of formulating compliance coatings, i.e., to meet national and 
state regulations on emissions of VOC's, is very recent and not well 
developed. For many applications, suitable substitutes have simply not 
been developed. Approaches to the problem of reducing emissions include: 
() applications techniques including powder coatings, hot-melt coatings 
and radiation cured coatings, (2) re-design of polymer binders and coating 
reformulation and (3) use of compliance solvents. Recent research focuses 
on formulating with low molecular weight oligomers and telechelic resins 
which are converted in, for example, a bake cycle. 
In contrast, typical medium to high molecular weight epoxy resin contains 
many backbone hydroxyls and is cured through these hydroxyls by curing 
agents and/or high temperature. These high molecular weight resins require 
non-compliant solvent for coatings applications, but can tolerate free 
water in the associated pigments. 
The new low molecular weight oligomer approach is, for example, to react 
epichlorohydrin with bisphenol A. This low molecular weight liquid epoxy 
resin contains few hydroxyl groups and is cured through the epoxide 
groups. This system is much less tolerant of free water in the pigments 
used. 
Typical curing agents for low molecular weight epoxy resins of this type 
include polyamides, polysulfides, aromatic amines, aliphatic amines and 
amidoamines. Low molecular weight oligomers of epoxy, phenolic and 
combinations thereof have application for compliance coatings. 
Thixotropic agents are added to these low molecular weight oligomer systems 
where the resin melt viscosity is typically below about 4000 cps, in order 
to achieve the efficient and uniform application of the coating during 
manufacture, for example, on conveyor line finishing of aerospace/military 
components. 
The field of organic coatings where this invention has application includes 
non-hydroxyl coating systems such as acrylic, epoxy, vinyl acetate, vinyl 
chloride, vinylidene chloride, vinyl butyral, styrene, alkyd, melamine, 
isocyanate, polyester, phenolic, cellulose, and by specific example, 
moisture cured urethane resin systems. In general, a resin from the group 
above may be solubilized in an aliphatic and/or aromatic and/or 
chlorocarbon solvent and then pigments, fillers, coloring agents and 
thixotropic agents are incorporated in the coating composition. 
The present invention has particular value in plastisols of the following 
general formula: 
______________________________________ 
Material Parts by Weight 
______________________________________ 
Polyvinyl chloride resin 
100 
Dioctyl phthalate 45-100 
Epoxidized oil 0-5 
Octyl epoxy stearate 
0-40 
Stabilizer 1-5 
Filler 0-100 
Stearic acid 0-2 
Thixotrope 2-15 
______________________________________ 
Another application of the invention is in adhesive sealants of the 
following general formula: 
______________________________________ 
Material Parts by Weight 
______________________________________ 
Polyvinyl chloride 
100 
Dioctyl phthalate 
5-100 
Tricresyl phosphate 
0-100 
Filler 35-200 
Stabilizer 1-5 
Bonding agent 0-20 
Thixotrope 2-15 
______________________________________ 
Still another application of the invention is in coatings of the following 
general formula: 
______________________________________ 
Material Parts by Weight 
______________________________________ 
Acrylic, epoxy, vinyl, melamine, 
100 
alkyd, urethane, isocyanate, 
phenolic or cellulose resin 
Amine, amide or sulfide 
0-125 
curing agent 
Aliphatic solvent 2-200 
Aromatic solvent 0-100 
Chlorocarbon solvent 
0-100 
Pigment 2-100 
Filler 0-150 
Thixotrope 2-15 
______________________________________ 
Preferred thixotropes produced by the present invention are Fuller's earth 
clays which have been vacuum dried to a moisture content below 5% and 
intimately admixed with a stabilizing fluid to preserve the low moisture 
state thus created. The inventors previously disclosed in U.S. Pat. No. 
4,966,871 a method for vacuum drying thixotropic attapulgite to from about 
2% to about 5% moisture, and in application Ser. No. 489,065 a method for 
drying by conventional methods and intimately admixing with silicone to 
result in a thixotropic attapulgite having a moisture content of from 
about 2% to about 5%. 
The structure of Fuller's earth clays as explained in the literature is 
thought to be represented by double silica chains running parallel to one 
another, with the chains linked together through oxygen atoms at their 
longitudinal edges to form a kind of double-ribbed sheet. The ribbed 
sheets are arranged so that the sheets point together and are held 
together by aluminum and/or magnesium in octahedral coordination between 
apex oxygens of successive sheets, forming an amphibole chain. Chains of 
water molecules run parallel to the amphibole chains and fill the 
interstices between the chains. 
The cavities of attapulgite will accommodate 4 molecules of water per unit 
cell, and this zeolitic water (i.e., loosely held in the lattice) would 
account for the dehydration loss at low temperatures. Attapulgite exhibits 
a characteristic diffraction spacing of 10.48A which does not change with 
variations in relative humidity or moderate heating up to about 
300.degree. C. Differential thermal curves for attapulgite show an initial 
endothermic reaction below about 200.degree. C. and additional endothermic 
reactions at about 225.degree. C. to 350.degree. C., which correspond 
approximately to the intervals of abrupt water losses shown by the 
dehydration curves. At 300.degree. C. to 350.degree. C., the ribbons of 
attapulgite take a tilted position. The original structure may be regained 
if heating is discontinued because attapulgite rehydrates readily. At 
above 400.degree. C., the fiber length contracts rapidly. This is 
explained by a closing of the cavities which leads to the disappearance of 
the water-absorbing property. Fuller's earth clays dried above 400.degree. 
C. exhibit no thixotropic properties. 
Without wishing to be bound by any particular theory, it is believed that 
the invention functions by removing water from the Fuller's earth clay 
minerals without disrupting the amphibole chain structure, without losing 
absorption capacity and without altering thixotropic properties. It is 
known that when temperature alone is applied to drive off the water under 
normal atmospheric pressure, the results obtained are: (1) when heated 
below about 350.degree. C., the water refluxes to the original site upon 
lowering the temperature or (2) when heated above about 350.degree. C., 
the moisture content remains lowered and reflux is prevented. It is 
believed that this results from the collapse of the double-ribbed 
structure of attapulgite which occurs in the temperature range of 
300.degree. C. to 400.degree. C. as described above. 
As a result, Fuller's earth clays, including attapulgite and sepiolite, 
cannot be dried under normal atmosphere to a moisture content which is 
compatible for use in plastics or coatings without destruction of the 
structure which provides the thixotropic properties. 
The inventors have found that the thixotropic properties of Fuller's earth 
clays can be preserved and reflux of moisture can be prevented by (1) 
drying Fuller's earth under a vacuum at temperatures in the range of about 
100.degree. C. to 300.degree. C. or (2) drying Fuller's earth by 
conventional (non-vacuum) methods at temperatures in the range of about 
100.degree. C. to 350.degree. C. and then intimately admixing silicone in 
a mixer or (3) drying Fuller's earth under a vacuum at temperatures 
ranging up to about 300.degree. C. and then intimately admixing a 
stabilizing fluid, e.g., silicone, in a mixer. As will be appreciated, 
vacuum processes should remove water from the clay at temperatures far 
below ambient, but for practical purposes we prefer to work at least above 
80.degree. C. 
The inventors would postulate that (I) the removal of all the zeolitic 
water from the Fuller's earth clay mineral without destruction of the 
double-ribbed structure or (2) the removal of a substantial amount of the 
zeolitic water and replacing this zeolitic water with a stabilizing fluid, 
e.g., silicone fluid, to fill the interstices between the chains of the 
above mentioned ribbed sheets prevents the destruction of the 
double-ribbed structure and that reflux is prevented by removal of the 
zeolitic water and blocking the cavities with the stabilizing fluid.

DETAILED DESCRIPTION 
The present invention is directed to the use of thixotropes in the 
application of plastics, including plastisols, adhesive sealants and 
coatings which are cured by heat or moisture, and compliance coatings. 
Fuller's earth clays are effective and attapulgite clay is a preferred 
thixotrope for these applications because it is readily available 
commercially and produces a viscosity ratio approximating previously used 
thixotropic asbestos. The inventors have found very desirable thixotropic 
Fuller's earth clays and a plurality of methods for their production. 
One method is to heat a commercially available thixotropic attapulgite 
having a moisture content between 10% and 15% in a vacuum at a temperature 
between approximately 100.degree. C. and 300.degree. C. for a period 
sufficient to reduce the moisture content of the attapulgite to a desired 
level, typically below 5% moisture, measured by ASTM D-280-A. Another 
method is to heat a commercially available thixotropic attapulgite with a 
moisture content between 10% and 15% in a conventional (non-vacuum) oven 
at a temperature between approximately 100.degree. C. and 350.degree. C. 
for a period sufficient to reduce the moisture content of the attapulgite 
to a desired level, typically below 5% moisture, followed by intimately 
admixing with a silicone fluid in a mixer. 
The inventors have found that a very low moisture content thixotropic 
attapulgite may be produced by heating a commercially available 
thixotropic attapulgite having a moisture content typically between 10% 
and 15% in a vacuum between about 1 Torr and 10.sup.-4 Torr at a 
temperature ranging up to about 300.degree. C. for a period sufficient to 
reduce the free water content of the attapulgite to a level between about 
0.1% and about 5.0%, measured by ASTM D-280-A, and retaining the 
attapulgite in this low moisture state until admixed with a stabilizing 
fluid in a mixer. The surface treatment of the thixotropic agent in 
accordance with this improved method consists of the admixture of 0.1% to 
10% by weight of a stabilizing fluid to the low moisture thixotropic 
attapulgite. Suitable stabilizing fluids for use according to the present 
invention are those that, as indicated above, fill the interstices in the 
structure of the Fuller's earth clays, prevent the reflux of significant 
quantities of free moisture, and preserve the thixotropic properties so 
that the thixotrope may be shipped and stored in a conventional manner. As 
examples of such stabilizing fluids, mention may be made of flurochemicals 
of the group consisting of polymeric and nonpolymeric types comprising 
perflurocarbon chains, CF.sub.3 CF.sub.2 CF.sub.2. . . , long chain 
carboxylic acids and silicone fluids. 
The particularly preferred silicone fluids useful in the present invention 
are either organopolysiloxanes or organosilanes, are well known and 
readily available on the open market and therefore will not be discussed 
in detail here. These compounds have a carbon to silicon linkage and 
include such as disclosed in Hyde U.S. Pat. No. 2,490,357 and Warrick U.S. 
Pat. No. 2,541,137. Particularly preferred silicone fluids include (1) the 
group of linear alkylsilanes or alkenylsilanes in liquid form, preferably 
of less than 250 molecular weight and having a viscosity at 25.degree. C. 
of between 0.25 and 100 centistokes or (2) completely condensed linear or 
cyclic organosiloxane derivatives, preferably of less than 12 silicon 
atoms per molecule for cyclic siloxanes, and having a viscosity at 
25.degree. C. of between 0.25 and 100 centistokes. While silicone fluids 
generally are usable in this invention, a preferred silane fluid is vinyl 
trimethoxy silane. A specific preferred siloxane fluid is vinyl modified 
polydimethyl siloxane, i.e., a polydimethyl siloxane in which, typically, 
1% to 25% of the methyl side group have been replaced with vinyl groups. 
Another useful silicone fluid is octamethylcyclotetrasiloxane. We prefer 
to use from about 0.1 to about 10%, preferably about 0.2% to 2% of the 
silicone fluid. 
EXAMPLES 
Plastisols having the following compositions were prepared: 
Example 1 
______________________________________ 
Parts Parts 
Plastisol A by Wt. Plastisol B by Wt. 
______________________________________ 
Geon 121 100 Geon 121 100 
Dioctyl phthalate 
100 Dioctyl phthalate 
75 
Sympron 1489 
4 Paraplex G-62 5 
Gamasperse 80 
100 Nuostabe V-1788 
3 
Thixotrope 7 Thixotrope 10 
(attapulgite (attapulgite 
vacuum dried & vacuum dried and 
admixed with admixed with 1% 
1% vinyl octamethyl- 
modified cyclotetra- 
polydimethyl siloxane)** 
siloxane)* 
______________________________________ 
*Union Carbide Fluid A1751, Union Carbide Corp. 
**Dow Corning 244 Fluid, Dow Corning Corp. 
Geon is a trademark of the B. F. Goodrich Co. for polyvinyl chloride resin. 
Paraplex is a trademark of Rohm and Haas Co. for an epoxidized soy bean 
oil plasticizer. Nuostabe is a trademark of Tenneco Chemical Co. for a 
metal soap stabilizer of barium, cadmium and zinc. Sympron is a trademark 
of Synthetic Products Co. for a barium, cadmium, zinc and phosphate 
stabilizer. Gamasperse is a trademark of Georgia Marble for a calcium 
carbonate filler. 
First, the thixotrope was prepared by placing typical thixotropic 
attapulgite clay in a vacuum chamber (at approximately 10.sup.-2 Torr and 
heating the attapulgite at temperatures ranging up to 300.degree. C. for a 
period sufficient to reduce the moisture content to approximately 0.2%. 
The time required will vary depending upon amount of the attapulgite, the 
size of the vacuum chamber, the amount of vacuum, etc., but in a typical 
chamber of 1 ft.sup.3, with about 2 pounds of attapulgite held at about 
150.degree. C., will be about 3.5 hours. The vacuum chamber was re-filled 
with dry nitrogen gas, the dried thixotropic attapulgite was removed from 
the chamber and immediately divided approximately into two aliquots and 
silicone added to each. For the preparation of plastisol A, 1% of Union 
Carbide Silicone Fluid A-1751 was added to one aliquot of the dried 
attapulgite identified immediately above and the mixture tumbled until the 
siloxane was uniformly dispersed, resulting in a dry powder without 
evidence of an oily character. 
For the preparation of plastisol B, I% of Dow Corning 244 Fluid was added 
to the other aliquot of dried attapulgite and tumbled until uniformly 
dispersed. A similar dry powder resulted. The surface treated attapulgite 
samples were removed from the mixer and viscosity measurements were made 
at ambient temperature. A viscosity ratio of approximately 5 was obtained 
in each instance when the viscosity measured with a Brookfield 
Viscosimeter at 2 rpm was divided by the viscosity measured by the same 
instrument at 20 rpm. This ratio compared favorably to that of 
approximately 4 for thixotropic asbestos measured in the same manner. All 
samples of attapulgite prepared as described above retained their 
thixotropic character, and moisture did not reflux into the processed 
attapulgite after silicone treatment. 
In another method of producing a thixotrope with a moderately low moisture 
content, a typical thixotropic attapulgite was placed in a standard drying 
oven and heated at a temperature between 100.degree. C. and 350.degree. C. 
for a time sufficient to reduce the moisture content to approximately 5% 
and intimately admixing this intermediate product with a silicone fluid by 
tumbling in a mixer, as described in detail in application 489,065. 
The thixotropic attapulgite prepared according to either of the above 
described methods was then mixed with the other components of plastisols A 
and B. All compositions adhered well when applied to metal and produced 
satisfactory films when heat cured. None of the films exhibited 
discontinuities or bubbles. 
Conventional thixotropic attapulgite, prepared by placing the clay in a 
drying oven at temperatures between 100.degree. C. and 350.degree. C. for 
a period sufficient to reduce the moisture content to approximately 5%, 
but without silicone treatment, rehydrates to about 10% to 15% moisture 
content within a few hours, depending upon ambient humidity conditions. 
Samples of plastisols A and B were prepared using normal thixotropic 
attapulgite with a moisture content of about 12%. These samples resulted 
in undesirable films having visibly observable bubbles in the films. 
This invention also has application for an adhesive sealant of the 
following composition: 
Example 2 
______________________________________ 
Adhesive Sealant 
Parts by Wt. 
______________________________________ 
Pliovic K-80 resin 100 
Dioctyl phthalate 50 
Mark LL stabilizer 2 
Tricresyl phosphate 
40 
Triethylene glycol dimethac- 
20 
rylate bonding agent 
Duramite 120 
Nytal 200 20 
Sparmite 60 
Thixotrope 4 
______________________________________ 
Pliovic is a trademark of The Goodyear Co. for polyvinyl chloride resin. 
Mark LL is a trademark of Witco Chemical Co. for a barium cadmium 
stabilizer. Duramite is a trademark of Cyprus Mines Co. for calcium 
carbonate. Nytal is a trademark of R. T. Vanderbilt Co. for talc. Sparmite 
is a baryte of Pfizer Inc. The thixotrope is sepiolite which has been 
vacuum dried to 0.2% moisture and admixed with 1% Union Carbide A-171, a 
vinyl trimethoxy silane fluid. 
This invention also has application for a compliance coating to meet 
emissions standards for volatile organic compounds (VOC's) as represented 
by the following composition: 
Example 3 
______________________________________ 
VOC Compliance Coating 
Parts by Wt. 
______________________________________ 
D.E.R. 337 epoxy resin 
100 
Resimene 746 curing agent 
50 
Methyl ethyl ketone 
15 
Ti-Pure 900 40 
Thixotrope 8 
______________________________________ 
D.E.R. is a trademark of Dow Chemical Co. for epoxy resins. D.E.R. 337 is a 
low molecular weight oligomer. Resimene is a trademark of Monsanto Co. 
Ti-Pure 900 is a trademark of the DuPont Co. for titanium dioxide pigment. 
The thixotrope is attapulgite which has been vacuum dried to 0.2% moisture 
and admixed with 1% Union Carbide A-1751 silicone fluid. 
The invention may also be practiced by combining the attapulgite clay or 
other thixotropic agents with the compounded plastic prior to vacuum 
drying. This method is less desirable, however. 
Attapulgite is a member of a group of clays called Fuller's earth. Other 
clays in this family are sepiolite and palygorskite, which also have 
application interchangeably as low moisture thixotropic agents in plastics 
and coatings when processed according to the teachings of this invention, 
as indicated above. 
While rather specific terms have been used to describe various embodiments 
of the present invention, they are not intended nor should they be 
construed as a limitation upon the invention as defined by the following 
claims: