U.S. patent application number 15/062825 was filed with the patent office on 2016-07-07 for processes for the manufacture of light-weight inorganic foam materials and articles produced thereby.
The applicant listed for this patent is Robin Crawford, John Douglas. Invention is credited to Robin Crawford, John Douglas.
Application Number | 20160194253 15/062825 |
Document ID | / |
Family ID | 52019711 |
Filed Date | 2016-07-07 |
United States Patent
Application |
20160194253 |
Kind Code |
A1 |
Crawford; Robin ; et
al. |
July 7, 2016 |
Processes for the manufacture of light-weight inorganic foam
materials and articles produced thereby
Abstract
In a process for manufacturing foamed material, particles of a
plant material as an organic expansion agent, particles of an
inorganic base material and water are blended together. The blend
is heated and pressurized to homogenize and liquefy or plasticize
it. The blend is then extruded through a die where, in the course
of the extrusion, superheated water in the blend vaporizes to foam
the blend, the extrudate then being cooled and fired.
Inventors: |
Crawford; Robin; (Carlisle,
CA) ; Douglas; John; (Brantford, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Crawford; Robin
Douglas; John |
Carlisle
Brantford |
|
CA
CA |
|
|
Family ID: |
52019711 |
Appl. No.: |
15/062825 |
Filed: |
March 7, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14308647 |
Jun 18, 2014 |
|
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15062825 |
|
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61836421 |
Jun 18, 2013 |
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Current U.S.
Class: |
106/677 ;
106/122; 264/44 |
Current CPC
Class: |
B28B 1/24 20130101; C04B
2235/612 20130101; B28B 3/20 20130101; C04B 38/064 20130101; C04B
38/10 20130101; C04B 2235/6021 20130101; C04B 2111/00129 20130101;
B28B 1/50 20130101; C04B 38/02 20130101; C04B 35/62213 20130101;
C04B 38/064 20130101; C04B 38/02 20130101; C04B 35/64 20130101;
C04B 35/00 20130101; C04B 35/00 20130101; C04B 2235/6022
20130101 |
International
Class: |
C04B 38/10 20060101
C04B038/10; B28B 1/50 20060101 B28B001/50; B28B 1/24 20060101
B28B001/24 |
Claims
1. A process for manufacturing foamed material comprising blending
particles of a plant material as an organic expansion agent,
particles of an inorganic base material and water to produce a
blend, heating and pressurizing the blend to homogenize and liquefy
it, extruding the blend through a die where, in the course of the
extrusion, superheated water in the blend vaporizes to foam the
blend, and cooling the extrudate.
2. The process of claim 1, the organic plant material including at
least one of corn, wheat, rice, potato, apple, and carrot.
3. The process of claim 2, the expansion agent including chopped
corn.
4. The process of claim 1, further comprising firing the extrudate
to drive off remaining water and organic content in the
extrudate.
5. The process of claim 4, further comprising the firing being such
as to sinter the inorganic material content of the cooled
extrudate.
6. The process of claim 4, further comprising the firing being such
as to reaction cure the inorganic material content of the cooled
extrudate.
7. The process of claim 4, further comprising cutting the fired
extruded, foamed material into lengths for use in producing an
article of manufacture.
8. The process of claim 4, wherein the extrudate is injection
moulded before firing.
9. The process of claim 1, wherein the plant material is chopped to
produce particles up to an eighth of an inch across.
10. The process of claim 1, wherein the expansion agent is present
in a weight proportion of between 25% and 50% of the blend weight
and the water is present in a weight proportion of between 5% and
10% of the blend weight.
11. The process of claim 1, the base material comprising
non-polymeric particles of at least one of mineral, clay, ceramic,
cement, concrete and metal.
12. A foam material manufactured by a process of blending particles
of an organic plant material as an expansion agent, particles of an
inorganic base material and water to produce a blend, heating and
pressurizing the blend to homogenize and liquefy it, extruding the
blend through a die where, in the course of the extrusion,
superheated water in the blend vaporizes to foam the blend, and
cooling the extrudate.
13. The foam material of claim 12, the organic plant material
including at least one of corn, wheat, rice, potato, apple, and
carrot.
14. The foam material of claim 12, the expansion agent including
chopped corn.
15. The foam material of claim 12, the foam material manufactured
by a process which further includes firing the extrudate to drive
off remaining water and organic content from the extrudate.
16. The foam material of claim 15, the inorganic material content
of the cooled extrudate sintered by the firing.
17. The foam material of claim 15, the inorganic material content
of the cooled extrudate reaction cured by the firing.
18. The foam material of claim 15, the extrudate being injection
moulded before firing.
Description
CROSS REFERENCE TO RELATED PATENTS
[0001] The present application claims priority pursuant to 35
U.S.C. 119(e) to U.S. Provisional Patent Application Ser. No.
61/692,732 filed Jun. 18, 2013, and U.S. patent application Ser.
No. 14/308,647 filed June 18, 2014, both applications entitled
"PROCESSES FOR THE MANUFACTURE OF LIGHT-WEIGHT CERAMIC MATERIALS
AND ARTICLES PRODUCED THEREBY", the disclosures of which
applications are hereby incorporated herein by reference in their
entirety and made part of the present application for all
purposes.
FIELD OF THE INVENTION
[0002] This invention relates to processes for the manufacture of
light-weight ceramic materials.
BACKGROUND
[0003] Ceramic materials and light-weight materials are typically
not synonymous with one another. Light-weight implies a low density
and high porosity. Lighter weight ceramics are made from a few
different techniques that include: the use of burnout materials,
reticulated foam, vacuum casting, and expanding clay.
[0004] Burnout materials are typically organic-based materials
added to clay batch recipes that burn out upon firing to form
porous ceramic. The burnout material is a solid particle that
occupies space in the clay material. During the firing process, the
burnout material converts to carbon and then disappears during
off-gassing, which leaves a void the size of the original particle.
There is a limit to the amount of porosity produced which is
dictated by the proximity of clay particles to one another for
integrity.
[0005] Reticulated foam materials typically involve taking an
open-cell polymer-based reticulated foam and impregnating it with a
clay slurry. The foam is wrung-out leaving only a coating of
ceramic slurry within the foam. Upon firing, the polymer foam burns
away leaving the ceramic exo-skeleton. The exo-skeleton is dense,
but the bulk porosity is dictated by the reticulated-foam. There
are limits on how small the pore size can be and foam ceramics are
typically simple shapes such as plaques. Vacuum casting involves
mixing a watered down clay slurry with fibres and using a vacuum to
remove the liquid content. This leaves the slurry and fibres in a
felt-like mass that needs to be dried before firing. Firing locks
in the structure and produces a lighter weight ceramic block.
Shapes typically include large blocks or complex geometries.
[0006] Expanding clay materials are produced by firing certain
types of naturally occurring clay in a rotating kiln. This process
uses the natural organics in the mined clay as an expanding agent
to expand to form porosity. The result is a spherical particle with
porous core and dense shell. Spherical particles are the only shape
that can be produced and the composition and therefore properties,
of the fired article are governed by the composition of the mined
clay.
[0007] Lightweight concrete uses aeration processes or aggregates
like porous slag to lower the concrete density. Aeration involves
pumping air into the concrete which traps the air as pores that
retain their shape during curing thus making a lighter weight
product. Porous slag is a bi-product of the steel making industry.
Porous, smaller particles are separated from the slag and these are
blended into the concrete mix. Slag particles are somewhat less
dense than concrete, 25% weight reduction being common for the
lightweight concrete industry.
[0008] Improvements are possible in processes for manufacturing
lightweight ceramic materials and in articles of manufacture made
using such materials.
SUMMARY OF THE INVENTION
[0009] According to one aspect of the invention, there is provided
a process for manufacturing foamed material comprising blending an
expansion agent and a ceramic base material and water to produce a
blend, heating and pressurizing the blend to homogenize and liquefy
it, extruding the blend through a die where, in the course of the
extrusion, superheated water in the blend vaporizes to foam the
blend, and cooling the extrudate. In this specification, the term
liquefy will be understood to encompass plasticizing as well as
liquefying.
[0010] Preferably the extrudate is fired substantially to drive off
remaining water and organic content in the extrudate and to sinter
or reaction cure the ceramic material. The expansion agent
preferably comprises plant material, such as corn, wheat, rice,
potato, apple, and/or carrot with a preferred expansion agent being
chopped corn, preferably of the order of eighth inch particle size
or less.
[0011] The extruded, foamed material can be cut to a length before
or after firing for preparation for use in producing an article of
manufacture. Such a length of material can be machined to desired
shape provided it is fired or dry enough that it has a measure of
rigidity. Alternatively, the extrudate is subject to injection
moulded while still malleable and formable, and before firing.
[0012] The expansion agent is preferably present in a weight
proportion of between 25% and 50% of the blend weight. Water is
present in a weight proportion of between 5% and 10% of the blend
weight. Base materials may include any non-polymeric material which
is at least one of mineral, grain, clay, ceramic, cement, concrete,
and metal.
[0013] According to another aspect of the invention, there is
provided a component produced by any of the processes as previously
described. The component can be integrated with base materials that
have not been foamed so as to produce a composite article having a
lighter weight than if the article were formed solely from the base
material.
BRIEF DESCRIPTION OF THE DRAWING
[0014] For simplicity and clarity of illustration, elements
illustrated in the accompanying figure are not drawn to common
scale. For example, the dimensions of some of the elements are
exaggerated relative to other elements for clarity. Advantages,
features and characteristics of the present invention, as well as
methods, operation and functions of related elements of structure,
and the combinations of parts and economies of manufacture, will
become apparent upon consideration of the following description and
claims with reference to the accompanying FIGURE, which forms a
part of the specification, the FIGURE being a part schematic, part
sectional view showing apparatus for use in a process according to
one embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION INCLUDING THE PRESENTLY
PREFERRED EMBODIMENTS
[0015] There is described a cost effective direct expanded foam
process for producing foam materials with customizable properties,
varying shapes and sizes using any base or raw material that can be
sintered or reaction cured, especially ceramic materials.
[0016] As shown in the accompanying figure, an expansion agent 12
is blended with the base raw material(s) 14 and water 16 in a
hopper 10. The blend is passed through a compression style extruder
18 which heats 20 and pressurizes the material blend as it is
conveyed. After passing through a shaping die 22 at the exit of the
extruder, the moisture vaporizes in an explosive manner carrying
with it the base material. The moisture converts to steam (water
vapour) which has an expanded volume that is many times the liquid
water in the compressed blend. Moisture is retained by the
expansion agent throughout the extrusion process and only allowed
to escape during expansion. The expansion agent goes from a solid
during mixing, to liquid in the extruder, and then to solid again
upon expansion. Solidification of the expansion agent allows it to
retain the shape of the pores created as the steam vaporizes. The
base material(s) do not inherently expand, but are carried within
the expansion agent like a suspension. This finely disperses the
base materials throughout the mix from start to finish. The result
is a rigid foam within seconds of expanding that retains its shape
through cooling and subsequent finish drying/curing.
[0017] Actual constituents such as the nature of the expansion
agent(s) and base material(s), the constituent amounts of the
expansion agent(s) and base material(s) and water in the blend, and
the applied temperature, pressure and other extrusion process
properties are selected to produce a customizable end product. The
end product material can itself be post-processed such as by
injection moulding while the extrudate is still malleable or by
machining once the extrudate has cooled and dried and, if desired,
fired. Customizable properties can be achieved through the ratio of
blending between expansion agent, base raw material(s) and water.
More expansion agent typically produces more porosity in the final
product. More base material typically produces a denser, less
porous final product. Water is necessary for expanded foam
production, with less water making a denser foam.
[0018] Shaping is dependent on the operation of the foaming
process. Foam is produced continuously or intermittently. The foam
can be readily machined in the expanded state or after
post-processing. The foaming process makes materials easy to
machine where machining would normally be extremely difficult if
the materials were in their normal state. Continuous operation
produces consistent cross sections of unlimited lengths. Insertion
of a cutting mechanism at the exit of the die allows the foamed
extrudate to be readily cut into intermediate lengths from particle
size on through long lengths.
[0019] Of particular interest, pellet sized pieces of the extrudate
are aggregated and fired to form bricks. Also of interest are
radiant heating tiles for which pieces that are up from a few
inches to a foot long and a few inches wide are made. These are
subjected to a finish machining process to true up dimensions. Such
tiles are used in combustion applications where a good seal is
important for avoiding gas leaks. Also of interest, continuous tube
or profiled shapes are cut to lengths on the order a several
feet.
[0020] Intermittent operation allows the foam to be used in batch
operations such as injection molding. Injection molding is
typically used with complex geometries, large or small. The foaming
process is started, injected, and stopped all within a single cycle
lasting several seconds. The quick solidifying nature of the direct
foaming process allows for parts to be ejected quickly producing
fast cycle times. The injection moulding dies are subjected to
rapid heating and cooling. Heating is important for keeping the
expanded extrudate material flowing. Then, rapidly cooling the die
quenches the material and ultimately the shape before the mould is
opened and part ejected. The difference between injection moulding
and continuous extrusion is that injection moulding is a batch
process that requires a shot (i.e. metered dosage) of material with
a defined start and stop to the process cycle. The cycle repeats
very frequently, but is not continuous. Another difference is that
the extrudate material expands into the die and solidifies in
comparison with convention injection moulding where the material to
be cast flows into the die as a liquid and then solidifies. The
extrudate material flowed through the die in an expanded form
without densifying the material as might otherwise happen owning to
pores collapsing in response to high pressure build-up at the end
of the injection cycle.
[0021] Various base raw materials can be directly foamed,
essentially to produce a porous foam version of the starter
material. Base materials may include non-polymeric materials such
as minerals, grains, clays, ceramics, shales, cements, concrete,
metals, etc. The process is not limited to these materials and may
also include plastics and other traditionally foamed materials.
[0022] Various expansion agents can be used including corn, wheat,
rice, potato, apple, carrot, etc., and where appropriate, mixtures
of expansion agents.
[0023] The expansion process uses moisture in combination with the
starch and, in some cases, gluten base of the expansion agent to
produce an expanded product that retains its shape. The starch and
gluten content become molten under the extreme pressure and
temperature to homogenize the blended mixture. Thus, the expanded
extrudate has very uniform properties and distribution of the
expansion agent and the base material. Corn is a very robust
expansion additive, providing good properties across a variety of
material blends and at a low cost relative to existing foaming
processes. Corn flour, cornmeal, corn grit, milled corn, chopped
corn, cracked corn and whole corn can all be used. The food
industry uses cornmeal as the staple material for expansion.
Because of the "food grade" designation and extensive processing,
cornmeal is not the most cost effective for industrial
manufacturing of non-food expanded products. "Yellow" cornmeal has
the skin and germ removed as a part of the processing. It results
in the highest expansion ratio across the corn materials of 20:1
(ratio of expanded size to initial die size). Chopped corn is the
most cost effective expansion material, providing the best
combination of expansion properties versus cost with an expansion
ratio of 10:1. Chopped corn takes the whole kernel and chops/cuts
it into small particles ranging from flour to 1/8 inch in size. At
current pricing, chopped corn represents a 3+fold cost saving over
cornmeal at about half of the expansion for a net positive benefit
for industrial purposes.
[0024] For expanded ceramic purposes, the proportion of expansion
agent in the blend typically varies from 95% down to 5%, with the
most stable fired ceramic foam product being between 50% and 25%
expansion agent. At 100% proportion of expansion agent, there is no
ceramic in the blend, so no material survives the firing process,
as the organic agent turns to ash and disappears as a gas. At 0%
expansion agent, there is no expansion and the ceramic base
material either clogs the extruder, extrude with no expansion, or
tears to pieces as the steam vaporizes because there is no starch
or gluten to solidify and hold the mass together. The result of
100% clay-ceramic extrusion depends completely on the rheology of
the base mix. Gritty mixes clog, dough-like mixes extrude, and
non-plastic mixes steam to pieces. The 50% to 25% corn range is
thought to have much to do with the volume of expansion agent added
versus the clay-ceramic base. Expansion agent density ranges from
about 2 to 4 times lighter than the base clay-ceramic material,
which correlates well with the mixed volumes being similar.
[0025] If there is too much corn, in excess of 50%, then the
shrinkage rate on subsequent firing rises exponentially and
survivability rate drops. The reason is that the clay-ceramic
particles are spread so far apart upon expansion that it takes that
much shrinkage before clay-ceramic particles come in contact with
one another and start to bond/sinter and resist additional high
rate shrinkage. Fired/sintered shrinkage rates for 50+% corn by
weight in the blend can be of the order of 25% to 90% which for
most applications, negate the benefit of adding more corn because
the fired product shrinks to close to its starting size. The result
is a lightweight ceramic foam material but with very little net
expansion after firing. Survivability of the high shrink materials
is also a problem. Clay-ceramic particles need to be in contact
with each other for the body to survive. This bonding/sintering of
particles is what gives ceramic materials their strength. With
insufficient sintering, the body is a mechanically locked group of
particles that may look solid but is in fact extremely fragile if
handled. Industrial applications generally require more robust
materials for handling, mixing, etc. in high throughput
environments.
[0026] Moisture is also important to direct expansion to produce
the foamed ceramic material because, in the form of steam, it is
what produces voids or pores in the expanded product. Most if not
all the raw materials, both expansion agent and raw material base,
have some amount of as-shipped moisture. Typically, the expansion
agents have around 10% retained moisture for storage
purposes--shelf life. A greater amount of moisture increases the
risk of mold or decay. However, too little moisture means there is
a risk of dust and the added cost to fully dry the raw product
which can have up to 90% moisture when harvested. In the case of
ceramics, the moisture content can vary from less than 0.5% on up
to 10.degree. A for premixed materials. Typically, the best
expanded results are for blends of expansion agent and base
material having moisture content between 10.degree. A and 15%. The
difference between the raw material moistures and blended target
moistures is added as water during the mixing cycle. Too little
moisture can result in clogging of the extrudate due to poor flow
or a dry extrudate that has less expansion than desired, as the
dryness restricts the expanded material mobility thus quenching in
some intermediate structure. Too much moisture produces so much
steam that the extrudate blows itself apart. The steam expands
close to 2000 times its liquid volume and requires that the
expansion agent form a bubble around this expanded void. When
expansion is too high relating to too much steam, the bubble will
burst and the expanded extrudate will lose its integrity, literally
blowing to pieces. Too much water, for example 25+%, results is a
damp, un-expanded extrudate and so much mobility in the mixed blend
that it readily flows through the extruder and falls out of the
die, not developing the residence time required for heat and
pressure generation which are key to the foaming process.
[0027] Heat and pressure are important to direct foaming composite
materials (2-phase system--expansion agent and base material). At
start-up, the extruder and expansion die are externally heated to
accelerate the foaming action. The pressure takes a couple of
minutes to build to steady-state, as the extruder screw is normally
clean at start-up. Moisture is added to the first material entering
the extruder to make it easier to flow. This purge stage lasts only
until the extruder is full and material starts to exit the die. The
initial extrudate is wet and does not expand. This slowly
transitions to wet material with expanded bubbles. The final stage
is when the material stops transitioning and is fully expanded.
This is called steady-state. Steady-state is reached when the feed,
expansion and heating rates have all stabilized. In steady-state,
the friction from within the extruder produces almost enough heat
to maintain the temperature set points of 250.degree. F. for the
extruder barrel and 315.degree. F. for the expansion die. These
temperatures may vary based on the properties of the mix, where
higher friction materials may produce slightly higher temperature
set points and lower friction materials may require the
supplementary heating controls to assist in maintaining the set
points.
[0028] The screw is made up of 3 sections: feed, transition and
metering. The feed section has the same dimensions throughout and
is used to feed the loose mixed material from a hopper into the
extruder. The transition section is where the compression, or
pressurizing, takes place as the screw volume reduces from one unit
to less than one unit as a result of compression. This compression
forces the particles in the blend against one another creating
friction that generates heat. Here, the blend converts from a
loose, solid to a dense, molten flow. The pressure and heat is
enough to activate the starch/gluten in the expansion agent
producing a liquid phase that homogenizes and carries the base
material. The metering section is right before the die and
regulates the flow of material exiting the screw and entering the
die. As a whole, the extruder takes one volumetric unit entering
the feed section of the extruder, pressurizes it to produce less
than one volumetric unit of feed in the compression/transition
section of the extruder, this compressed feed being metered and
pushed through the heated die until it reaches the die exit where
it expands to produce from 1+ to 20 volumetric units of
expanded/foamed output.
* * * * *