Molded polymer composite

A composite for constructing an article which is composed of a nonmetallic substance as represented by igneous rock of different particle sizes which are compacted and then surrounded by a solidified plastic resin. In a preferred manner, the igneous rock material is a selected type of basalt with the basalt particles being of different mesh sizes to be compacted into a mold. After compaction, the plastic resin as represented by an epoxy resin is introduced into the mold so as to displace air from any voids surrounding the basalt particles and to surround them with a resin which later solidifies. A novel resin delivery system is also presented.

BACKGROUND OF THE INVENTION 
This invention relates to a composite for constructing a molded article 
wherein this composite includes an igneous rock. More particularly, the 
invention relates to a composite formed primarily of a basalt igneous rock 
of varying particle sizes surrounded by a solidified epoxy resin to result 
in a rigid structure having high strength and superior vibration damping 
properties than previously attained. The invention further relates to a 
method for forming a composite of such type. 
The prior art teaches the use of polymeric materials to adhere granite 
chips as fillers into a composite for machine tool beds. Examples of such 
are a brochure by Ciba-Geigy designated Technical Notes 2/1980, describing 
an Epoxy "Concrete" wherein a particular epoxy resin is combined with 
granite aggregates. 
In Swiss Patentschrift No. 612 610 a machine support is described which is 
composed of a mixture of sand and gravel which is bound by a synthetic 
adhesive agent. The prior art in an article entitled "Methacrylate Resin 
Concrete" by H. Schulz and G. Nicklau, Werkstatt und Betrieb 115 (1982) 
11. refers to the use of methacrylate resin and basalt in the manufacture 
of surface plates and measuring machine bases. In U.S. Pat. No. 4,382,820 
a structural member for a machine tool body is described of the 
nonmetallic type wherein cement, concrete cement or ceramic is utilized as 
the base material into which solid objects such as fibers, filaments and 
metals are placed as reinforcing elements. The grading of aggregates to 
obtain maximum density of solid material is known and is referred to in an 
article entitled "Grading Aggregates" in Industrial and Engineering 
Chemistry Vol. 23, No. 9, pages 1052 to 1058, as well as in the Journal of 
American Ceramics Society Vol. 44, No. 10, pages 513 to 522, entitled 
"Mechanical Packing of Spherical Particles". 
Nowhere in the prior art is there illustrated the use of igneous rock 
material in the form of a multiplicity of discrete solid particles of 
different particle sizes to be compacted in a manner such that a minimum 
amount and volume of voids are present between the solid particles with 
these voids being filled with a solidified plastic to result in a rigid 
article having high strength and high vibration damping properties. 
Neither does the prior art disclose the use of basalt in a compacted form 
of solid particles of different size in combination with a plastic resin 
to result in a molded article with unique features as described herein. 
It is an advantage of the present invention to provide a composite for 
constructing a molded article which employs a unique combination of 
igneous rock material and a solidified plastic resin. Other advantages are 
the utilization of an igneous rock material as represented by basalt in 
combination with a cycloaliphatic epoxy resin to result in a molded 
article with high strength and vibration damping properties as well as 
having a smooth and pleasing appearance as it is released from a mold; a 
unique composite to which additional filler materials can be added that 
can be formed into a variety of shapes; a method of making molded articles 
which is easily performed yet does not require special tooling or handling 
procedures and will result in a composite having a substantially reduced 
number of voids therein. 
SUMMARY OF THE INVENTION 
The foregoing advantages are accomplished and shortcomings of the prior art 
are overcome by the present composite for molding an article wherein an 
igneous rock material in the form of a multiplicity of discrete solid 
particles with different particle sizes is arranged and compacted in a 
manner to result in a high degree of rock-to-rock contact such that a 
minimum number and volume of voids is presented therebetween. A solidified 
plastic material fills the voids between the solid particles providing a 
bonding material therefor. In a preferred manner, the igneous rock 
material is a basalt which preferably is present in an amount greater than 
70% by volume of the composite and preferably with the resin present in an 
amount of less than 30% by volume of the composite. Also preferably, the 
bonding material is an epoxy resin of the cycloaliphatic type and 
particularly is a copolymer of bis(2,3-epoxycyclopentyl) ether and 
ethylene glycol. Also preferably, in order to obtain the maximum stiffness 
in the article the particle sizes of the preferred basalt material should 
be of at least three different sizes so as to be readily compacted with a 
high degree of rock contact and to result in the minimum amount of voids 
therebetween. 
A unique method of making an article is also presented wherein a 
multiplicity of discrete solid particles of an igneous rock material is 
placed in a mold with the discrete particles being of different sizes and 
compacted in a manner such that a minimum amount of voids are created 
between the particles. A plastic resin material is then flowed around the 
particles so as to fill the voids and to displace any air therebetween. To 
fill the voids and expell the air a definite resin-air interface is 
maintained by introducing the plastic resin at the bottom of the mold and 
in a direction toward the top. In order to optimize flowability of the 
resin, both the solid particles and the resin are heated prior to 
introduction of the resin into the mold. As is well known, resin viscosity 
is reduced by heating.

DESCRIPTION OF THE EMBODIMENTS 
While various igneous rocks can be employed in the composite, the preferred 
aggregate is a variety of basalt having high strength and high modulus. 
Typical values are: 
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Compressive Strength 
64,000 p.s.i. 
Tensile Strength 3,200 p.s.i. 
Compressive Modulus 
12,000 p.s.i. 
of Elasticity 
Tensile Modulus 17,000 p.s.i. 
of Elasticity 
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It should be noted that basalt differs substantially from granite in both 
mineral content and grain structure. Granite is acidic, whereas basalt is 
basic. When formed in early geologic times, basalt was extruded and cooled 
quickly creating very fine grains. Granite, on the other hand, was 
intrusive or slowly cooled forming very large grains and a non-homogeneous 
structure. The coarser grained granite has poorer physical properties than 
those possessed by the finer grained basalt. 
Basalt is composed largely of the mineral plagioclase feldspar 
(approximately 85%); lesser minerals include pyroxene and olivine. 
Conspicuously absent from basalt is quartz; granite, however, contains 
more than 25% quartz. Certain characteristics of basalt and granite are 
compared in FIG. 6, wherein the major differences in mineral composition 
and grain size are illustrated in a three-dimensional graph. 
The crushed basalt ultilized in this invention should be graded by particle 
size and thoroughly dried in order that the moisture will not be taken up 
by the polymeric resin thus preventing proper curing. To aid in this, 
storage bins for the crushed aggregate should be provided which will 
afford the introduction of warm air so as to be passed up through the 
aggregate in order to effect proper drying. Alternatively, vacuum drying 
of the aggregate could also be utilized with, or as an alternative to, 
heated air drying. This method would involve evacuating a chamber 
containing the aggregate to boil off surface moisture. Still a further 
procedure in drying an aggregate would be to combine it with a drying 
chemical such as portland cement. 
While various resinous materials could be utilized in the composition and 
method of this invention, certain cycloaliphatic epoxides are preferred. 
For example, the cycloaliphatic epoxide ERLA-4617 which is available from 
the Union Carbide Corporation and is the copolymer of bis 
(2,3-epoxycyclopentyl)ether and ethylene glycol, catalyzed with a tertiary 
amine. The following Table I indicates the high strength of the ERLA-4617 
resin versus a common resin ERLA-2772 which is a bisphenol 
A-epichlorohydrin epoxy resin also available from Union Carbide. 
TABLE I 
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Cast Cast 
ERLA-4617 
ERLA-2772 
cured cured 
with m-PDA* 
with m-PDA* 
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Modulus (psi) 
Compressive 
890,000 441,000 
Tensile 783,000 458,000 
Flexural 815,000 462,000 
Strength (psi) 
Compressive 
32,800 19,200 
Tensile 19,200 12,900 
Flexural 31,000 17,500 
Viscosity cps @ 80-100 7000-9000 
25.degree. C. 
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*Metaphenylenediamine 
The following Examples are set forth for the purpose of illustrating the 
present invention and should not be construed to limit the invention to 
the precise ingredients, proportions, temperatures or other conditions 
specified. 
EXAMPLE 1 
______________________________________ 
Identification 
Quantity Sizes 
Materials and Source (grams) (ASTM E-11) 
______________________________________ 
Basalt 1044 -3/4 + 3/8 
696 -8 + 16 
633 -50 + 100 
Resin: Bis D.E.R. 324 resin, 
125 
phenol A-epi- 
Dow Chemical 
chlorohydrin 
Company 
epoxy resin 
and an aliphatic 
reactive diluent 
(C.sub.12 -C.sub.14 alphatic 
glycidyl 
ether) 
Curing Agent: 
AC-220-JQ 100 
methyl tetra- 
Anhydrides and 
hydro phthalic 
Chemicals, Inc. 
anhydride 
Catalyst: BASF Wyandotte 
.625 
1-methylimi- 
dazole 
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The basalt is crushed, rinsed in clear water and dried. 
The interior of a suitable mold such as indicated at 10 in FIG. 4 is 
previously polished to attain a smooth surface finish. The mold in this 
instance is rectangular and measures 2 7/16 inches in length x 25/8 inches 
in width and 121/8 inches in height. The mold interior is coated with a 
suitable mold release compound such as MMS 5050 available from Ecolab, 
Inc. A mixture of resin, curing agent and catalyst is prepared by 
preheating it to 100.degree. C. 
The basalt aggregates are placed in the previously prepared mold and 
compacted using a suitable compaction means such as an air hammer. The 
mold and compacted aggregate are then heated to 100.degree. C. The 
prepared fluid resin mixture at 100.degree. C. is thereafter placed in a 
pressurized container and injected through a tube or conduit such as 
indicated at 16 in FIG. 4 using a pressure regulator to control the flow 
rate. The injection pressure is continuously adjusted upwards to a maximum 
of 10 psig. As the resin rises through the mold, a definite resin-air 
interface is maintained expelling the air and filling the voids between 
the solid basalt particles. 
As indicated in FIG. 4, the various sizes of the compacted basalt particles 
are indicated with the numbers 11, 12 and 13. The numeral 11 indicates the 
largest sized basalt particles in the -3/4+5/8 mesh size, 12 indicates the 
intermediate size in the -8+16 mesh size and 13 the smaller size in the 
-50+100 mesh size. The numeral 14 illustrates the resinous plastic 
material which surrounds the particles resulting in a molded article such 
as a machine tool component. 
When the molded article is released from the mold it has a smooth and 
shining surface with few air pockets or voids. The molded article would 
require no further preparation before use. 
Example I demonstrates a definite resin-air interface which is maintained 
by the force of gravity acting upon the resin. Alternatively, the definite 
resin-air interface would be maintained by applying other force fields to 
the mold, such as a centrifugal force field. For example, a centrifugal 
force field could be created by rotating or otherwise moving the mold. In 
the latter example, the resin would be injected at the outer periphery of 
the mold. 
EXAMPLE 2 
In this particular Example a cycloaliphatic epoxide compound previously 
referred to in Table II as ERLA-4617 is employed. This particular resin is 
utilized in the same manner and in the same proportions with the basalt 
aggregate as indicated in Example 1. A suitable curing agent such as the 
indicated m-phenylenediamine can be employed. All other conditions for 
introducing the resin and casting of the composite is as previously stated 
in Example 1. 
It should be pointed out that FIG. 4 illustrates one method of introducing 
the resin material 14 between the different sizes of compacted basalt 
particles 11-13, wherein the resin material is introduced under pressure 
from the bottom of the mold through conduit 16. If desired, a mold such as 
20 illustrated in FIG. 5 could be utilized. A stationary delivery tube 21 
with apertures 22 is positioned inside mold 20 and preferably in a central 
manner. Retractable delivery tube 23 for delivery of resin from the top to 
the bottom of the mold is coaxially placed within tube 21. The 
introduction of resin is initially from the bottom of the mold and offers 
the advantage of air elimination toward the top, the air eventually 
exiting therefrom as the resin material gradually fills the mold from the 
bottom. The added advantage of mold device 20 with retractable delivery 
tube 23 is the fact that the level of resin is adjustable through the 
retraction of tube 23 and its selective positioning over apertures 22 for 
the purpose of gradual resin introduction and air elimination. 
FIG. 1 represents a typical layout of a large scale injection station, with 
high production capacity to produce a molded machine tool member. Bulk 
resin is transferred from tank cars indicated by the numeral 31 through 
suitable conduits such as 32 and 33 communicating with primary storage 
tank 34 for resin and tank 30 for the hardener or curing agent. The resin 
and curing agent would be routed through respective lines 35 and 36 by 
means of pumps 37 to conditioning tanks 3B for conditioning. Subsequently, 
the product is transferred by booster pumps 39 to a proportioning, mixing 
and dispensing machine 40. A suitable coloring pigment is added to the 
molded product which is stored in tank 45 and delivered to machine 40 
through conduits such as 41 and 42 interconnected to conditioning tank 38 
and booster pump 39. From there the product is introduced into the 
aggregate filled mold 41. 
As indicated earlier, the finished molded composite is as illustrated in 
FIGS. 1 and 2 and indicated by the numeral 16 in FIG. 2 where a 
rectangular cross section of the composite is particularly shown after it 
is removed from mold 41. 
FIG. 3 depicts another geometric configuration as indicated by the numeral 
50. This particular embodiment simulates a typical I - beam support. It 
will be noted that the basalt particles 11, 12 and 13 in the embodiments 
of this invention are in a compacted state with a high degree of 
rock-to-rock contact as well as being surrounded with an adhesive layer of 
resinous plastic. 
The molded article 16 in FIG. 2 as it would be produced from the mold 41 in 
FIG. 1 is illustrated in the form of a machine tool member and 
particularly a column and bed. The composite of this invention is also 
capable of being molded into the following machine related components: 
uprights, saddles, pallets, magazines, spindle heads, belt guards, gear 
covers and boxes, tool changers, as well as structures for material 
handling systems. 
It is anticipated that in other important uses, the composite can be molded 
without limitation into bathtubs, manhole covers, door handles, furniture 
and construction materials. 
Certain epoxy resins have been illustrated herein with the cycloaliphatics 
being preferred. In addition to the bisphenol A-epichlorohydrin epoxy 
resins, other epoxy resins such as the novolac resins and the linear 
aliphatic epoxy resins could be employed while still attaining the 
described advantages. While epoxy resins have previously been described, 
other resinous materials with relatively low viscosities which can form 
the desired bonding between the varying sizes of compacted igneous rock 
are the polyesters or methacrylates. 
It is preferred to employ igneous rock in the form of at least three 
different particle size ranges. However, if desired, a plurality of 
different mesh size ranges as represented by more than three particle size 
ranges could be utilized with the smaller particle sizes being employed to 
fill the voids between the larger particles as previously explained. It 
should be pointed out that for consistent attainment of high strength 
during processing, the largest particle size should be less than one-third 
of the wall thickness in the region of the component member in which it is 
placed. 
While in the previous Examples epoxy resins are employed with basalt alone, 
if desired, other reinforcing or filler materials could be employed with 
the basalt particles such as flakes or fibers in the form of steel fibers. 
Flakes and steel fibers as composite reinforcements offer good strength 
and stiffness. Flake filled composites provide superior vibratory damping; 
the large number of the polymer layers between the individual flakes, all 
of which dissipate energy during deformation, is responsible for the high 
level of damping in flake filled composites. The high strength and 
rigidity of a flake and/or steel fiber filled composite is due to their 
strength and rigidity as well as their high load acceptance. The high load 
acceptance is due to their high aspect ratios. 
As indicated earlier, an important aspect of this invention is the fact 
that igneous rocks of varying particle sizes are tightly compressed or 
compacted in the mold device with a high degree of rock-to-rock contact 
and then surrounded with a solidifiable resinous plastic. To obtain 
maximum stiffness and vibration damping, it is essential that a maximum 
amount of igneous rock material be utilized with a minimum amount of the 
resinous plastic. Additional benefits are obtained if the particular 
igneous rock is basalt and is combined in conjunction with cycloaliphatic 
resinous material wherein one of the polymer units of the copolymer is bis 
(2,3-epoxycyclopentyl) ether. 
The present invention provides a unique composite for molding such articles 
as machine tool components utilizing readily available materials and 
offering high strength and vibration damping. The materials employed are 
relatively inexpensive thus lending themselves to a low cost composite and 
final product. Further, the product of this invention offers a pleasing 
appearance as it is removed from the mold having a smooth and shining 
surface of the desired color thus requiring no further preparation prior 
to use. 
Although the illustrative embodiments of the invention have been described 
in considerable detail for the purpose of fully disclosing a practical 
implementation of this invention, it is to be understood that the 
particular components and compositions shown are intended to be 
illustrative only and that various novel features of the invention may be 
incorporated in other structural forms without departing from the spirit 
and scope of the invention as defined in the subjoined claims.