Note: Descriptions are shown in the official language in which they were submitted.
23919 KSK~jlb Al 12/2/80
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BACKGROUND OF THE INVENTION
The present invention relates generally to roofing
and siding construction materials. Gore particularly, the
present invention concerns a method of producing such construe-
lion materials from a mixture of plant fibers and port land
cement.
There is an ever-increasing demand for construction
materials having some or all of the following characteristics:
relatively light weight, fireproof, waterproof, mailable,
odorless, insulative and relatively inexpensive. In spite of
the attractive properties of a dense building material consisting
of plant fibers such as wood fibers bonded with port land cement,
no such product has effectively been marketed. Only porous
products consisting of excelsior bonded with port land cement
or a magnesium oxychloride cement have seen limited use. It
is difficult to bond port land cement to plant fibers because
water-soluble compounds in the fibers inhibit the setting of
the cement. Among these compounds are hemicelluloses, tannins,
sugars and others. Heretofore, an effective agent for negate
in the adverse effects of these water-soluble compounds in the
fibers has not been discovered.
Another problem is the effect of the motion of the
fibers during the setting of the port land cement. Any spring-
back of the fibers after being compressed or swelling and/or
shrinking with absorption or resorption of water during the
setting of the port land cement will fracture the tiny crystal-
files of cement as they slowly form. Since the strength of the
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23919 KSK/jlb Al 12/2/80
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cement depends on the inter meshing of these crystallizes, their
disruption will greatly weaken the cured product.
Heretofore efforts to control the adverse effects of
these water-soluble inhibitors in a wood or other similar fiber
composite material utilizing port land cement as a binder, have
resulted in five different approaches:
1) extracting the inhibitors;
2) accelerating the rate of set of the port land
cement;
3) increasing the strength of the composite mater-
tat by the addition of resins;
4) coating the surfaces of the fiber particles with
materials compatible with cement (mineralization);
and
5) changing the composition of the port land cement
to obtain a material less sensitive to the in-
habiting action of the water-soluble compounds.
To date, none of these approaches has been economically successful.
SUMMERY OF TIRE INVENTION
Among the objects and advantages of the present in-
mention are to provide:
Ion cost composite building materials particularly
adapted for exterior use;
composite building materials made from plant fibers
bonded with port land cement having the following properties:
1) a weight which is substantially less than that of comparable
composite building materials made from a sand/cement mixture;
2) a resistance to fire; 3) an anility to be nailed into
place; 4) an ability to be molded into attractive shapes or
sheets, and sawed with readily available tools; 5) sufficient
strength to withstand blows from hammers during construction
without cracking; and 6) resistance to the deleterious effects
of sunlight, rain, freeze thaw conditions and insects;
issue
a process for manufacturing building materials of
the aforementioned type which does not produce ecologically
harmful effluents;
building materials made from a plant fiber/portland
cement mixture in which the adverse cement set inhibiting effects
of the water-soluble compounds in the fiber are effectively
negated;
a process of manufacturing Baldwin materials from
the aforementioned mixture in which the time that portions of
the mixture must be held under compression is reduced to a
minimum; and
a method of producing composite building materials
from a mixture of plant fibers bonded with port land cement in
which a wide variety of plant fibers may be utilized.
In accordance with the present invention, composite
articles of port land cement and fibrous material obtained
from various plants are formed by mixing the fibers with port land
cement and a water soluble silicate, the latter being present in
amount by weight greater than about your percent of the weight of
the port land cement and up to about twenty-four percent, and
thereafter maintaining the mixture under pressure while heating
the same to a temperature sufficient substantially to accelerate
the setting of the mixture. This causes the mixture to set
sufficiently hard to prevent spring back or swelling of the
fibers thus permitting the application of pressure to be
terminated in a short time and the formed article or coup-
site to be cured to final strength without further applique-
lion of pressure or heat. When fibers containing large
amounts of cement set inhibiting chemicals are being used
the fibers preferably are treated with an aqueous solution
2391~ KSlC:jlb At 1
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of a dichromate or permangenate salt prior to mixing
them with the port land cement and water soluble silicate.
Various process modifications may be made as described in
more detail hereinafter. We have discovered that dichromate
or permanganate treatment of the fibrous material somehow
inhibits the usual adverse effect on the setting of port land
cement which has been observed with some fibrous plant material.
Other objects and advantages of the present invention
will be apparent from the following detailed description of a
preferred embodiment thereof and from the attached drawings.
BRIEF DESCRIPTION OF TOE DRAWINGS
Fig. 1 is a general schematic illustration of the
overall operation of the manufacturing process; and
Fig. 2 is a graph showing the relationship between
compressive strength and curing time for concrete.
Fig. 3 is a graph illustrating the effect of the
addition of sodium silicate upon the strength of a port land
cement-fiber mixture.
DWELLED DESCRIPTION OF THE I~VENTIQN
In accordance with a preferred embodiment of the in-
mention, plant fibers are mixed with a soluble silicate such as
an alkali metal silicate solution (water glass) and port land
cement. This mixture is placed in molds and compressed. It is
then subjected to heat so as to raise the temperature of the
mixture to greater than 140F such as by placing it in an
atmosphere of live steam. This causes the mixture to set up
sufficiently within a short period of time, i.e., within fifteen
to sixty minutes, as to resist any tendency of the fibers to
swell or spring back Thus, the pressure applied to the molded
articles can be relieved and the articles permitted further to
cure at ambient temperatures to final strength. The articles
Y ASK jib Al 12/2/~0
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will have enough strength after fifteen or twenty minutes in
the mold to permit trimming and sawing to be performed. Within
about twenty four hours, the articles will have about eighty
percent of their ultimate strength and could be shipped at
that time. Longer periods in the molds will increase the out-
of-mold strength.
It has been found that the alkali metal silicate
should be present in concentration greater than about four
percent dry weight in proportion to the amount of port land
cement. Such amount, by some mechanism not understood, causes
the mixture rapidly to set up when heated, thus eliminating
the need to maintain a molded article under pressure a lengthy
period
When fibers containing amounts of set inhibiting
compounds sufficient to interfere with the set of the cement
are utilized, it has been found the deleterious effect of
such compounds can be negated or diminished in large part
by pretreating the plant fixers with an aqueous solution of
an alkali metal or other water soluble salt of dichromate or
permanganate ion. The wetted fibers are allowed to stand for
a period of time sufficient to permit the dichromate or penman-
Gannett ion to react with substantially all of the cement set
inhibiting compounds in or near the surface of the fibers.
Thereafter, the silicate material and port land cement are
added to the now treated wood fibers, with or without other
useful chemicals, and the mixture is molded under pressure
as described above. the residual products of the pretreatment
do not harm the strength of the cement, nor does the treatment
when properly controlled appear to degrade the strength of
the fibers.
`
~2(?445~i
In the case of dichromate ion, the reaction with the
fibers can be accelerated by acidifying the dichromate solution.
In such a case it is necessary after fiber treatment to neutral-
ire the remaining solution at the conclusion of the dichromate
treatment period with a suitable alkaline solution or solid.
It may be desirable in some instances to add a cement set axle-
orator along with the port land cement in order to reduce the
molding time.
Prior to treating the fiber with the dichromate soul-
lion, the fiber may first be treated with a sulfite solution This treatment enhances the strength of the composite product
by a mechanism discussed subsequently.
In the case of treatment with permanganate ion, the
permanganate solution is preferably on the alkaline side.
Plant Fibers
Different plant fibers have varying types and anoints
of water-soluble compounds therein which can inhibit the setting
of the port land cement. Some, such as hemlock, have little or
none. On the other hand, western red cedar has a high percentage
of such compounds, but because of the resistance of the fiber
thereof to decay and insect attack, it is a useful source of
fiber for the composites of the invention. Other woods such
as Douglas fir are less difficult to bond with port land cement
but dichromate treatment does lessen the setting time of cement
mixed with Douglas fir fibers. The present invention may also
be extended to fibers of hard woods such as oak and walnut and
of other plant materials, such as, for example, strewn buggies,
sisal, and the like, which have relatively high tensile strength
since it is contribution of this property of the fibrous mater-
tat which is sought.
23919 KSK:jlb Al 12/2/80
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The fiber mixed with the cement can be in any of variety of forms depending upon the nature of the fiber source,
the geometry of the finished articles and the characteristics
or qualities desired in such articles. The fiber can be in
the form of strands or string material when made from grasses,
buggies, cedar bark, and like sources and a product of maximum
tensile strength is desired, rood flakes or planer shavings as
used in composite resin bonded products heretofore can also be
used. If a product with a smoother surface is desired, wood
can be used in the form of the product produced by hammer milling
wood flakes or planer shavings and passing them through screens
having openings of selected maximum size which may be from 1/16
inch to 3/4 inch depending upon the qualities desired in the
finished product.
Soluble Silicate
We have found that the incorporation of a sub Stan-
trial quantity of a soluble silicate in the fiber-cement mix
enables the mix to be set up rapidly, i.e. within one hour
or less, by the application of heat, to the point where the
set mass it dimensionally table and has sufficient strength
that it can he removed from a pressure mold and allowed to
cure further under ambient atmospheric conditions. Thus the
pressure mold used for the initial set is quickly available
for reuse.
The soluble silicate is preferably added as water
glass or potash water glass. It can be mixed with the fibers
before mixing with the port land cement or it can be added
after the cement and fibers have been mixed if added as a
freshly prepared gel. The silicate can also be added in the
dry form if sufficient water is also added to dissolve the same.
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We have found that with Douglas fir fiber, if the
silicate is present as byway' water glass in amount greater than
about eight percent based on the dry weight of port land cement,
the fiber-portland cement mix can be set by the application of
heat and pressure within fifteen to twenty minutes to a rota-
lively dimensionally stable condition. Preferably the water
glass is present in amount between eight and sixteen percent
of the cement. Increase in the percentage of water glass up
to about twelve percent will further increase the dimensional
stability of the product. However, still further increase in
the amount of water glass does not improve the dimensional sty-
ability of the product. Moreover, the ultimate strength of the
product reaches a maximum when water glass is present between
about twelve and sixteen percent. On the other hand the
out-of-the mold strength increases substantially proportion-
lately to the amount of water glass present. See Fig. 3.
Treating Agent
Dichromate ion is the base agent which we have found
to have the capability significantly to negate the adverse
effects of the cement set inhibitors in plant fibers. Louvre,
we have found that permanganate ion also shows a capability in
this respect, although to a lesser extent than dichromate ion.
Because dichromate ion treatment is much to be preferred, the
following detailed description will focus primarily on the use
of such ion.
The dichromate ion or permanganate may be supplied
in the form of alkali metal or other soluble salt. Two readily
available sources of dichromate ion are potassium dichromate
and sodium dichromate dehydrate. Other water-soluble metal
dichromates, e.g. calcium dichromate, may also be utilized.
G 1 Y It K
.
Dichromates are considered to be a potentially
hazardous chemical. Therefore, it is desirable that water-
soluble dichromate essentially be absent from the finished
product. Enough dichromate ion must be present during the
pretreatment of the fibrous material to ensure essentially
complete reaction of the cement set inhibitors on the surface
of the material with dichromate.
The manner in which the dichromate ion reacts with
the water-soluble plant compounds to negate their cement set
inhibiting effects is not completely understood by us. In the
finished product it is possible that the chromium ends up as
insolvable chronic oxide (Cry) which may be chemically bound
up with the hardened cement or with the original soluble come
pounds in the plant fibers, or both.
It has been determined that dichromate ion must be
present in the aqueous pretreating mixture in an amount ranging
from approximately 0.5~ to approximately I of the oven dry
weight of the fibrous material. The precise amount of Decker
mate necessary will depend upon the fibrous material since they
vary widely in the types and amounts of water soluble compounds
which inhibit the setting of port land cement. The amount of
dichromate ion added is that amount which is just sufficient
to react with the inhibitors present at or near the surface of
the fibrous material being treated, as determined by export-
mentation.
If the fiber particles, particularly of wood, absorb water during the initial stages of the set of the concrete,
the subsequent swelling or other shifting or curling of the
particles will disturb the growth of the cement crystallizes
and seriously weaken the final strength of the composite prod-
vat. Therefore, it is important that this water absorption be
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completed by saturating the fibers before the onset of the cure
of the cement. This saturation is preferably accomplished
during the treatment of the fibers with the dichromate by mix-
in the fibers with an aqueous solution of the dichromate salt
S having more water present than is required to saturate the
fibers.
The water required for the hydration of the cement
can be computed as being about 25% of the cement present.
Sources of water to meet this requirements in the case of
the saturation of the fiber scan be water available from the
solutions of the chemicals and from free water if necessary.
Rome many experiments with various wood fibers, we have deter-
mined that the total water necessary is the amount required to
saturate the wood fiber plus 25% of the weight of the port land
cement present. Wood will absorb moisture to about 30% of its
wet weight. Thus, the a unto to saturate wood fibers is equal
to oven dry weight of fibers - oven dry weight of fibers. For
composites of acceptable strengths, the weights of the ohm-
posits after air drying were plus or minus about 10-15% of
the empirical values calculated as described.
In practice, additional water in the amount of an
excess of 20-40% of the theoretical water were added to facile-
late the chemical treatments of the fibers and to improve the
mixing and molding characteristics of the composite.
The length of time necessary for the appropriate
action of the dichromate on the fibers depends on a number of
factors such as the concentration of the solution of the dip
chromates being used, the reaction temperature, the structure
of the fibers, the various chemical substances naturally pros-
en in the fibers and their amounts, the acidity ox the aqueous
phase and the possible presence of a surface active (surfactant)
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material. However, the actual time of treatment can only be
determined experimentally.
It will be recalled that it is an object of the in-
mention that the time required for the composite to be held
5 under pressure in the mold be as short as possible, to increase
the production rate of composite products and lower the menu-
lecturing costs by efficient use of press and molds. Only
enough press time should be allowed that the composite product,
when released from the mold, will retain its structural stabile
fly during the final set of the port land cement.
It has been found that acceptable production rates
can be realized with mold retention times from 30 to 90 minutes,
although using water glass in the quantities herein before mint-
toned enables the mold retention time Jo be reduced to as short
as fifteen minutes. In order to accomplish this production rate,
the quantity of the cement set inhibitors, if present in the
fiber in staunchly amount, must be reduced so that they will
not escape from the fibers and act on the cement even at the
elevated temperatures used during the molding cycle.
The necessary period for the dichromate ion to react
with the cement-set inhibitors so as to attain such production
rate will vary as indicated above. With some fibers such as
hemlock, little or no reaction time is required. With Douglas
fir which is recently cut, a few minutes at room -temperature
may suffice. With more difficult fibers such as western red
cedar, 10 or 15 minutes at the temperature of boiling water may
be required. It is desirable that in carrying out these rear
lions the concentration of dichromate be limited to provide the
a unto needed, the acidity level be adjusted to provide suffix
client speed of the reaction, and the lowest effective tempera-
lure used. The levels of these operating parameters must be
23919 KSK:jlb Al 12/2/80
I
determined experimentally with the fiber species to be used.
Departure from the preferred conditions may cause loss of
strength in the cured composite product because of degradation
of the fibers as well as poor cure of the cement.
Depending on the fiber, sodium dichromate dehydrate
in the amount of 0.5-8~ of the fiber (dry weight) being
treated is adequate to react with the cement set inhibitors.
During the dichromate treatment, surfactants should
be avoided. They act to accelerate the release of the cement
set inhibitors, thus disturbing the desired chemical condition
at the interface between the fibers and the port land cement.
In fact, if a surfactant is present at this point, the final
product strength can be seriously impaired.
It should be understood that separate treatment of
the wood with dichromate prior to the addition of the port land
cement is not absolutely necessary. The dichromate could be
added to an already prepared-moist wood fibers/portland cement
mixture. However, the strength of the final product is better
if the fibers are pretreated with dichromate before the add-
lion of the cement. The last mentioned technique ensures that
the set inhibitors are substantially negated before the cement
contacts the fiber.
The Acidifying Agent
A wide variety of acidifiers may be utilized. It
has been found that aluminum sulfate provides a good level of
acidity, somewhat buffered by the hydrolytic capacity of the
aluminum ion. On the other hand, unbuffered sulfuric acid is
harmful. Aluminum chloride may also be used but it is desire
able not to have the corrosive chloride ion present. Other
acidic salts may also be useful but have not yet been tried.
Usually, aluminum sulfate to the extent of I to
I of the fiber weight is adequate.
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20~S6
The Reducing Agent
The use of sulfurous acid has been shown to be bone-
filial in our process for bonding wood fibers to port land
cement, although the mechanism is not understood. if the wood
such as fir is first treated with a dilute, weakly acid solution
of sodium sulfite followed by the addition of dichromate and then
water glass and cement, a substantially increased strength of the
composite is obtained. Moreover, any excess of dichromate over
that normally required for the reaction with the fibers is reduced
and thus removed. The Wylie acid system can be achieved by mixing
a solution of sodium sulfite with a solution of alum, using a
solution of sodium bisulfite, or using a solution of sodium
thiosulfate (hyposulfite). Strongly acidic solutions must be
avoided to prevent damage to the cellulose fibers.
The Alkaline Agent
After the completion of the dichromate treatment,
the solution remaining on the fibers is a weakly acidic soul-
lion of chromium sulfate and al~linum sulfate, or chromium
chloride and aluminum chloride, etc., depending on the acidic
system used. In order to provide a neutral condition more
favorable to the setting of the port land cement, this acidity
of the fibers should be neutralized by the controlled addition
of an alkaline substance to bring the pi to 7.0 or above.
Aqueous solutions of sodium hydroxide, potassium hydroxide,
sodium carbonate and the like may be used. Solids such as
lime (calcium oxide) may also be used but their performances
will be less satisfactory because of the necessity of their
first dissolving in the moisture present. For example, slaked
lime is only sparingly soluble and thus the neutralization
reaction progresses slowly.
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The substance preferred is sodium silicate. Even in
small amounts it has the advantage of precipitating calcium,
aluminum and chromium silicates which might act as cements,
mineralize the fiber surfaces, and impart a degree of waterproof-
news to the composite product. The mineralization technique is
discussed in US. Patent No. 2,623,828 issued to Dove. of water-
glass solution is utilized instead of a solid alkaline substance,
the water in the solution must be taken into account when stab-
fishing the appropriate portions to yield the desired water/cement
ratio.
The solution of sodium silicate preferably used is
a 2:1 dilution of 41 Be sodium silicate in water. For neutral-
ization of a 20% aluminum sulfate acidifying solution, a ratio
of at least twice the volume of sodium silicate solution for
each volume of aluminum sulfate solution is preferred. gain,
the proper water balance must be observed and higher or lower
concentrations of the sodium silicate may be used as the case
may require. In particular, higher concentrations may be
utilized to obtain a rapid set at elevated temperatures as
herein before described
The Port land Cement
Type III port land cement is preferred because of its
high early strength characteristic. Type I-II port land cement
may also be used, however. The cement is mixed with the moist
fibers after the completion of the dichromate reaction, if such
is carried out, and preferably after addition of the alcoholizing
agent and adjustment of the pi level thereof to a more or less
neutral state. Other more rapidly setting cements such as
P~GULATED SET (trademark) may also be utilized in order to
minimize the deleterious effects ox the cement set inhibitors
in the fibers. Ever, they are much more expensive than
port land cement and may have other detracting properties.
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The ratio of port land cement to fibers has a strong
relationship to the ultimate strength characteristics of the
finished product. The cement/fiber ratios may be varied con-
siderably, producing products having somewhat differing char-
acteristics. In general, the more dense the finished composite material (achieved by greater compression), the better is its
weather profanes and strength when the fixer to cement ratio
is constant. On the other hand, for strength only, there is
an optimum ratio of fiber to cement depending upon the type of
fiber used. In the case of wood fiber ratios ranging from
approximately 0.5:1 to approximately 4:1, of port land cement to
oven dry wood fiber, according to weight, will produce compost
tie materials of acceptable strength and weathering properties.
Strength appears to peak at cement/wood fibers ratio of approxi-
mutely 1.3:1 to approximately 1.7:1. Size and shape of the
particles are also important. Generally, acicular particles
or flat blades are superior to short, stubby particles.
At the higher end of the preferred range mentioned
above, e.g. port land cement to fiber ratios of approximately
2.75 or so, higher densities above 75 pounds per cubic foot
will be obtained, especially at pressures in the press over
150 psi. At ratios of 1.3 to 1.5:1 and pressures of 500 psi,
products having densities of 65-75 pounds per cubic foot are
readily prepared.
The Cement Set Accelerating Agent
Depending on the fibers being used and cement setting
rates desired, it may be desired to add a set accelerating
agent to the mixture. One well known suitable accelerating
agent is calcium chloride. It increases the speed of the in-
trial set of the port land cement but does not materially affect
the final strength thereof. Thus in a few hours, concrete
-16
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,
56
containing a small amount of calcium chloride will show higher
compressive strength than concrete containing no calcium color-
ides but the two samples will have the same strength after
twenty-eight days of curing. Other salts such as sodium sulfate
or sodium chloride may also be employed.
A number of important advantages are obtained through
the addition of a suitable accelerating agent. Such a substance
will speed the curing of cement at the interface between the
wood fibers and the cement so as to partially offset the no-
larding effects of the inhibitors in the wood fibers. However,
depending on the fiber compositions being used, the mere add-
lion of calcium chloride to the aqueous wood fibers/portland
cement mixture, without pretreatment with dichromate, can
result in composite materials of markedly less strength than
if dichromate is used.
It is important that the calcium chloride, if used,
be added immediately prior to the addition of the cement. This
promotes the concentration of the accelerator at the interface
between the fiber and the cement.
Triethanolamine (hereinafter referred to as TEA)
has been reported to be useful as an accelerator for the cure
of port land cement when used in small quantities. We found it
to be effective for our system but care must be taken to keep
the amount small and to add it after the addition of the cement.
The substance acts at least to some extent as a surfactant and
if added before the cement, it apparently causes the release
of additional and harmful quantities of the compounds which
retard the set of the port land cement.
The advantage of using TEA rather than calcium color-
ire as an accelerator is that TEA is far less corrosive than
-17_
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the calcium chloride and therefore much more useful when metals--
such as nails, reinforcing rods, etc.--are to be in contact
with the product.
Advantage may also be taken of the process by which
the port land cement sets. Fig. 2 depicts a graph showing the
relationship between compressive strength and curing time for
a typical concrete mixture. Point A on the curve of Fig. 2 is
arbitrarily selected for illustrative purposes as the point at
which the concrete mixture must be placed in the mold. Place-
mint before this point would waste mold time, and placement
after this point would reduce final strength of the product
as crystal formations would have advanced beyond the point
where they could be disturbed without serious damage. Point B
in Fig. 2 is arbitrarily selected for illustrative purposes as
the point at which the curing of the concrete has advanced
sufficiently to ensure dimensional stability upon removal of
the product from the molds. Thus, the curing cycle of the
concrete is divided into three phases
Phase I: The induction or procuring phase between
mixing and point A;
Phase II: The molding phase between point A and
point s when the product is in the mold;
Phase III: The curing phase after the product has
been removed from the mold.
In the actual manufacturing operation, it may be
desirable to permit the final mixture to procure a predator-
mined time before placing it in the molds. This will reduce
the amount of time that the mixture must remain under compress
soon in molds. This is important from an economic viewpoint
because stack press machines (hereafter described which are
-18-
` ~2~44~6
effective to form products from the present mixture are expend
size. By minimizing the molding time a given stack press can
be utilized more efficiently to produce a maximum amount of
product.
It should be emphasized that points A and B on the
curve of Fig 2 are arbitrarily selected for illustrative pun-
poses and must be accurately determined by experimentation for
a given fibers/portland cement system depending upon its come
position. When higher concentrations of silicates, i.e., greater
than four percent of the cement, are used, the mixed products
can be put in molds immediately after mixing and placed in the
press. The accelerated curing rate permits the procure step
to be bypassed. The method of the present invention is keyed or
coordinated with the curing cycle of the particular concrete
mixture (the fibers/portland cement mixture) in order to reduce
molding time and thereby achieve a continuous production of a
large quantity of product with a minimum amount of capital
investment for equipment.
The lolling Parameters
A composite product with superior strength and sun-
face texture can be formed from a fibers/portland cement mix-
lure by molding the same under compression at an elevated them-
portray. A molding pressure of between approximately 150 psi
and approximately 600 psi at a molding temperature of between
approximately 120F. and approximately 220F. will produce
useful products. If soluble silicate is present in amounts
less than equivalent to about eight percent byway' water glass,
a molding time of one hour or more will be required. However,
if the silicate is increased to the equivalent of twelve to
sixteen percent water glass, the molding time can be reduced
to as short as fifteen minutes for a five-eights inch
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23919 KSK:jlb Al 12/2/80
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thick product. Satisfactory products canoe obtained by
molding at ambient temperatures, but the molding time must be
extended substantially. The optimum molding pressure and them-
portray must be determined experimentally and will depend upon
primarily the composition of the fibers, the type of port land
cement used, and the presence of an accelerator. A molding
pressure of approximately 400 psi to approximately 500 psi and
a molding temperature of approximately 150-170F. have been
found to produce good results for the wood fibers/cement mix-
lures experimentally tested by us. It is preferable that such mixture be maintained at a temperature of approximately 150-
190F. throughout the molding operation. In order to accomplish
this, a live steam atmosphere may be utilized as later explained.
A humidified atmosphere during molding is helpful depending on
the design of the molds since it prevents undue loss of moisture
which might otherwise occur at the elevated molding temperatures.
Excessive moisture loss weakens the finished product.
Examples
A number of experiments were performed in order to
confirm the advantageous effects of soluble silicates and
dichromate ion or permanganate ion in a wool fibers/portland
cement composite. Standardized procedures were used so that
comparisons between many different samples prepared from a
variety of woods and cement would be meaningful. Mixing was
done by hand to the extent that a reasonably homogeneous mix
was obtained. Usually a mixing time of not less than two
minutes was required. All samples were molded in wooden or
steel molds having internal dimensions of 6" by 4" by 5/8".
The time that the mixture was allowed to stand in the molds
was varied depending upon the type of cement, temperature,
accelerator concentration and the like. With RF.GU~ATED SET
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~204~
cement, the molding time was approximately 30 minutes at a
temperature of approximately 180 to 212F. With Type III
port land cement, the molding time was one hour unless stated
otherwise.
After the samples were removed prom the molds, some
were tested immediately and some were allowed to stand for 14
days from the time of initial mixing before being tested for
modulus of rupture (O'ER. During this I day period, the samples
were kept at 60 to 80F. The samples were kept in a humid
atmosphere after molding for a few days to prevent water loss.
MAR measurements were made using a Dillon tester. The samples
measured approximately 4 inches wide by 5/8 inch thick and the
span used for the test was 4 inches.
Example I
The desirable effects of pretreating western red
cedar fibers with dichromate ion are shown in Table I. A
sample of crushed shavings of western red cedar, generally
about 3/4" by 1/4" by .02-04", together with water, alum and
sodium dichromate, was heated for half an hour in boiling water
in a closed glass container. A duplicate sample of western red
cedar without dichromate was similarly heated. Calcium chloride
was added to both samples to accelerate setting of the port land
cement. The dichromate solution used was 10% weight/weight and
the calcium chloride solution was 33% weight/weight. After the
heat treatment, the material was treated with water glass and
cooled and the Type III port land cement was added in the amount
indicated. After thoroughly mixing the cement with the treated
fibers, the mixture was placed in molds and pressed to produce
test specimens approximately 4" by 6" by 5/8" thick. The final
pressure was between about 270 psi and 300 psi. After a period
of one hour, the molds were opened and the samples allowed to
-21-
ivy Cook L 1",
Jo /-- ,,
GIL 20 pa
stand open to air at ambient conditions for 14 days for further
curing of the cement. They were tested for their module of
rupture using a Dillon tester as described above. The sample
made with sodium dichromate had far superior strength.
Example II
Although Douglas fir is far less difficult than cedar,
to bond with Type III port land cement, such a composite can
be improved substantially in strength with the dichromate treat-
mint especially if the fir is freshly cut. Such treatment is
very important for fast, high temperature molding. Fir planer
shavings less than a month old hammer milled with a 3/16" screen
were used to make test samples with results shown in Table II.
In all cases the samples were pressed for one hour at about 400
psi at 200-212F., and then tested two woks later.
Example III
Similar improvements can be obtained with the fast
setting REGULATED SET cement. The strength of these composites,
however, were not suite as high in the case of cedar fiber as
with Type III cement, but were very good in the case of Homer
milled clouglas fir fibers. These results are shown in Table
III. Hammer milled planer shavings of wood, either cedar tow
or Douglas fir; about 1" or less in length and about 1/8" or
less in width were used. The shavings were added to 10% w/w
potassium dichromate solution, along with water, 20 grams of
slaked lime, and 120 grams of REGULATED SET cement. The mixed
portions were compressed in steel molds at approximately 500
psi. The compressed composites were then removed from the molds
and allowed to cure in ambient conditions for 14 days prior to
testing.
-22-
~919 KSl~:jlb Al i2/2/~
" :` ^
Lucy;
Since REGULATED SET has a very rapid rate of set, it
is necessary to add a controlling chemical. Slaked lime appears
to be slightly better than plaster penis for this purpose in
these samples. Samples 8-10-4 and 8-10-5 were cured for 30
minutes in a steel mold in steam at atmospheric pressure. The
others were cured at room temperature overnight.
Example IV
In Table IV, the effect of varying the ratio of cedar
tow (hammer milled with 1/4" screen) to Type III port land cement
is shown. The cedar fibers, which had a moisture content of
10.8%, were first treated with I of their weight of sodium
dichromate dehydrate in water. Calcium chloride in proportion
of I of the cement present was also added. Sample 10-8-1 was
held under 300 psi for 12 hours, the other pressed at 600 psi
for the same period. All were cured for 14 days prior to
strength testing. As shown in the table, effective strengths
can be obtained over a relatively wide range of cement/fiber
ratios but they appear to peak around 1.6:1 in these cases.
Example V
A further example of the method of the present invent
lion is set out hereafter:
Sample Composition (Sample 2-159-4)
Cedar tow, hammer milled with 1/4"
screen moisture content 30.5~ 141 g.
Alum solution (20% w/w) 18 ml.
Sodium dichromate dehydrate
solution (10% w/w) 39 ml.
I~aterglass solution (1 part
byway parts water) 33 ml.
Calcium chloride solution (33% w/w) 6.5 ml.
Type III port land cement 108 g.
-23-
J J Lo L
I
Procedure
l. The dichromate and alum solutions were mixed,
then added to the cedar fiber, mixed thoroughly
therewith and let stand for 30 minutes at 100F.
2. Next the water glass solution was added.
3. text the calcium chloride solution was added.
4. Finally the port land cement was added.
5. The mixture was pressed in steel molds of in-
vernal dimensions of 6" by 4" by 5/8" (pressure
to close the mold was 460 psi).
6. The mold was maintained in a closed container
over toiling water vented to atmospheric pressure
for 60 minutes.
7. The sample was then removed from the mold and
allowed to cure at ambient room conditions for
14 days.
The final product had a density of 68 pounds per
cubic foot and MOW of 1448 psi.`
Example VI
In Table V the effects of addincJ sulfite to various
samples of hammer milled fir planer shavings are shown. In one
case (7-l99-l) sodium sulfate, which is the oxidation product
of sodium sulfite, was added to see if this compound was the
cause of the significant increase in strength resulting from
sulfite addition. The tests showed the product with sodium
sulfate had less strength than the same product using sodium
sulfite, but either additive caused an increase in strength
over the control, Sample Noah, see Table V.
Example VII
The effect of quantity of the triethanolamine (TEA)
on the strength of the composite is shown in Table VI. The
-24-
~391~ ~K:JL~ A ù
I ,~.
Lyle
need for carefully maintaining a low concentration of the TEA
is evident.
Example VIII
Still another example of the present invention is
set out hereafter.
Sample Composition (Sample 8-289-1)
Fir hammer milled planer shavings,
1/4" screen, moisture continuity% 90 g. (OX)
Sodium thiosulfate trihydrate 5 g.
Alum solution 20% w/w aluminum sulfate 20 ml.
Water 10 ml.
Sodium dichromate dehydrate solution 15 ml.
Water glass solution, 2:1 water:41Be'
sodium silicate 30 ml.
Type III port land cement g.
Triethanolamine solution 1% w/w 14 ml.
Procedure
1. The alum and sodium theosulfate solution were
mixed and immediately thereafter mixed with the fir.
2. Allowed to stand 5 minutes at room temperature
with frequent stirring.
3. The dichromate solution added and the mixture
heated 15 minutes in steam bath.
4. Thereafter cooled water glass mixed in, then the
Type III cement.
5. The solution of triethanolamine quickly added
and mixed.
6. Pressed into a steel mold having a cavity of
approximately 4" by 6" by 5/8", using a pressure
of 500 psi to bring the thickness just to 5/8".
25-
` 12~5~;
7. Placed in a humid atmosphere at a temperature of
150 to 170F. and held there under pressure for
one hour.
8. The sample was removed from the mold and lightly
sprayed with about 3 ml. of water to assure a
moist condition, then stored in a water vapor
tight container for 2 days at 90-100F.
9. Thereafter it was removed from the container
and allowed to stand under ambient room condo-
lions for 14 days to complete the cement cure.
The final product had a density of 72 pounds per
cubic foot and a OR of 1536 psi 4
Example IX
The beneficial effect of potassium permanganate treat-
mint was shown in other tests set forth in Table VII. In these
tests oven dried cedar shavings hammer milled with a 3/16" screen
were used in the tests, all weights are in grams.
Example X
A series of tests were carried out to test the
relative effect of using higher concentrations of water glass
with Douglas fir fiber treated with sodium dichromate where
the initial press was carried out at high temperatures. The
results are shown in Table VIII. In these samples the fiber
was prepared by hammer milling with an 1/8 inch screen Douglas
fir planer shavings. The water glass where added was added
after treatment of the fibers with sodium dichromate and before
the addition of cement. In all instances 3 parts of cement
were used for each part of fiber. Sodium dichromate and
water glass (as ~1 Be') and hydrochloric acid are expressed
as parts by weight. The samples were pressed at 500 pi
and held in a steam atmosphere for twenty-four minutes. They
were tested fifteen minutes after removal from the mold.
-26-
I 3 91 I K: J l D u
~L~04~L~
Example XI
The effect of the order of addition of cement and water-
glass was tested. As shown in Table IX no significant difference
in result occurs. In one procedure (Tests 12-lû-1) hydrochloric
acid and water glass were mixed. The resulting gel was mixed with
Douglas fir derived fiber. Finally Port land cement was mixed in.
- In other samples (Tests 11-6û-6 and AYE) Douglas
fir fiber was wetted with water, Port land cement then mixed with
the fiber, and finally a mix of water glass and hydrochloric acid
lo added.
In still other samples (Tests 11-6û-5 and Sue)
Douglas fir fiber was wetted with hydrochloric acid. ~aterglass
was then mixed with the fiber and finally Port land cement added.
In all instances 3 parts of Type III Port land cement,
û.36 parts of byway' water glass, û.36 parts 2.5N hydrochloric
acid, and approximately 1.32 parts water were used for each part
of fiber.
After mixing the samples were placed under an initial
50û pi pressure and heated in steam for 24 minutes. Samples
2û retained for a two week test were placed in plastic bags and
held at room temperature.
Example XII
Another series of tests were inducted with Douglas
fir fiber to determine the effect of different amounts of
water glass. The fiber was prepared by hammer milling planer
shavings using an 1/8 inch screen. Parts will be given by
weight. One part of fiber (oven dry basis) previously washed
with boiling water was mixed with 2.5N hydrochloric acid and
then a dilute solution of byway' water glass. Thereafter 3 parts
3û of Type III cement was mixed in, samples were placed in molds
and pressed -to an initial 5ûû pi and placed for twenty
" ~20~4~i6
minutes in an atmosphere of live s-team. Fifteen minutes
after removal from the steam some samples were tested. Others
were placed in plastic bags and tested after two weeks at room
temperature. These tests, as shown in Table X, demonstrated
increasing amounts of sodium silicate gave increasing out-of-
the-mol d strength, but that the two week strength peaked at
about sixteen percent water glass.
Example XIII
-
Tests were carried out to determine if calcium
chloride, a known set accelerator, could give the same bone-
filial effects as does the addition of water glass. In one
sample (10-30-2), one part of water washed fir was mixed with
three parts of Type III cement, 0.06 parts calcium chloride,
and one and only f parts of water. In another sample
(10-30-3), the calcium chloride was omitted and 0.36 parts
of hydrochloric acid, then 0.36 parts of sodium silicate
were substituted. Both samples were pressed to an initial
pressure of 500 pi and subjected to an atmosphere
of steam for twenty minutes, and then removed from the mold.
When tested one hour later, sample 10-30-2 with the calcium
chloride had an rDR of 21~ Sample 10-30-2 had an OR of 334.
Example XIV
As shown in Table XI, sodium silicate when used in
combination with sodium dichromate treatment of western red
cedar fibers, enhances the out-of-mold strength substantially.
In these tests, western red cedar hammer milled planer shavings,
1/8 inch screen, were treated with sodium dichromate. Acidified
sodium dichromate solutions (by addition varying amounts of sodium
dichromate to 2.5N hydrochloric acid) were added to the cedar.
Then, after reaction was essentially complete, an aqueous
solution of byway' water glass was added. Finally, Type III
cement was added. The samples were pressed at 500 pi
initial pressure and held for 24 minutes in atmospheric steam.
--28--
J 11~ G / G /
.`
` ~04~56i
solution of byway' water glass was added. Finally, Type III
cement was added. The samples were pressed at 500 pi
initial pressure and held for 24 minutes in atmospheric steam.
In summary, in accordance with our rapid set process
the cement/fiber/high ratio silicate mixture is set under high
temperature (preferably 175-1~0F) and high pressure. This
temperature should be reached within twenty minutes or less.
This enables the product to gain sufficient strength to be
removed from the mold and processed. Riviera, the product will
continue a rapid rate of cure and will attain within twenty four
hours eighty percent of its ultimate strength. High strength
of product can only be obtained, however, when substantial
amounts of silicate are utilized. For example, twelve percent
water glass is necessary with Type III port land cement to obtain
maximum fourteen day strength with untreated Douglas fir fiber.
The Manufacturing Process
The following discussion taken in conjunction with
Fig. l will provide an understanding of the overall operation
of a suitable manufacturing process of the present invention.
This example describes the procedure for making roofing shingles
approximately sixteen inches long, of various widths, and have
in a shape and thickness similar to shingles typically sawn
from cedar wood. Modifications in the various equipment and
other details described which may be necessary to produce other
composite building materials such as siding will occur to persons
skilled in the art.
The wood fibers Douglas fir, western red cedar, or
pine, etc.) are mechanically prepared in a conventional manner.
Plane shavings or flaked shavings may be utilized. These
shavings can be reduced in size by funning them through a
-29-
3L20~S6
hammer mill or through a disk refiner. For shingles, wood par-
tides produced by hammer milling and passing a 1/8" screen are
preferably used. However, a wide variation in particle sizes
may be used according to the present invention depending upon
the desired characteristics of the end product.
After a procuring period, if such is utilized, the
mixture is agitated in a suitable mixer and delivered to a disk
penning hopper 10 (Fig. 1). Wood fiber/portland cement mixture
delivered from the dispensing hopper is formed into a product
mat 12 of proper size and weight on a horizontal conveyor 14.
Generally the mat is wide enough to form several shingles
there across. The mat is relatively thick, and uncompressed
at this point. The conveyor I transports the uncompressed mat
12 onto a second conveyor 16 which carries the mat under a come
press ion roll 18. The blanket is compressed to a predetermined
thickness by the roll 18 to provide mat integrity for subsequent
operations. For example the compression at this point may
reduce the mat 12 to approximately fifty percent of its
original thickness.
The conveyor 16 then moves the compressed mat 12
under a reciprocating knife 20 which cuts the mat into disk Crete
portions 12' which are long enough so that the finished shingles
will be approximately 16 inches in length when completely cured.
The portions 12' of the mat are carried by the second conveyor
16 to a caulk plate applicator 22 where a bottom caulk plate 24
is placed underneath each portion 12' of the mat, and a top
caulk plate 26 is placed on top of each portion The caulk plates
24 and 26 may be of aluminum or other metal, such as iron
or steel, and are large enough to enclose the portion 12'. The
caulk plates are embossed to give the product its desired shape
and prevent the mat portions 12' from sticking to the platens
--30--
~261 ~4.S1~
of the later described staclc press. In addition, the caulk
plates serve as carriers by which the portions of the mat are
carried through the multiple stations of the equipment to be
formed into shingles.
Preferably a suitable caulk plate release agent,
such as zinc Stewart or Teflon coating, is used to prevent
the mat portions 12' from s-ticking to the caulk plates. The
caulk plates present a smooth base to the mat portions 12' and
this insures a flat, smooth surface on the cured shingles.
The caulk plates are configured to form several shingles across
a mat portion which is later sawed apart.
The now sandwiched mat portions 12' are deposited
upon a conventional stack press loader 28. It may comprise a
platform portion 30 upon which each of the sandwiched mat port
lions 12' is sequentially positioned. A hydraulically operated
plunger 32 raises or lowers the sandwiched mat portions to the
bottom of a multiple opening vertical stack press 34. The con-
struction of the stack press will not be described since it does
not comprise part of the present invention. Typical stack press
designs are disclosed in US. Patent Nos. 3,126,578; 3,478,137;
3,542,629; and 4,148,857.
The pairs of caulk plates 24 and 26, each loaded with
a mat portion 12' sandwiched there between are conveyed sequent
tidally into the entrance position at the bottom of the stack
press. The stack press 34 in general comprises a series of
vertically spaced pairs of heated platens. The loaded pairs
of caulk plates are received in the openings defined button
the pairs of platens. After each of the openings has received
a loaded pair of caulk plates, the press is then operated so as
to apply heat and pressure uniformly to the just inserted mat
portion 12'. Preferably the press is heated internally so
--31--
J l, Ire J L
I
1204~56
that the heat from the platens will insure that the mat portions
will be heated to and maintained at a temperature of approximately
200F while they are in position throughout the stack press. The
product is preferably enveloped in an atmosphere of live steam
at a temperature of approximately 200F. while in the press.
As each mat portion 12' sandwiched between upper and
lower caulk plates 26 and 24 is received in the entrance opening
a-t the bottom of the stack press I it is pressed to suitable
stops, preferably at a pressure of about 150 to 500 psi. Prey-
fireball the volume of the mat portions is reduced during the initial compression to below that required for the final product.
Thereafter the portions are allowed to expand slightly to
establish their final product volume. This permits the final
product volume to be maintained with considerably less pressure
than required to effect the initial product volume in the first
place. The pressure required after the initial compression
can be supplied by the weight of the loaded caulk plates stacked
above a given mat portion. The portions are maintained under
pressure for a predetermined time interval which is sufficient
to insure that their dimensional integrity will be preserved
upon release from the stack press. Again, -this time interval
is determined experimentally depending upon the composition
of the wood fiber/portland cement/dichromate/waterglass mixture.
As previously indicated, however, by coordinating the steps Of
the mechanical process precisely with the curing curve, the
total molding time can be reduced to two hours or less.
The stack press 34 is preferably one constructed so
that the loaded caulk plates are released at the top of the
stack press and are removed one at a time as a unit without
releasing pressure on the entire stack. When removed from the
top of the stack press the loaded caulk plates are received by
~32-
I
So
a conventional stack press unloader 36 which may have a con-
struction similar to the stack press loader 28. The loaded
caulk plates are lowered by the unloader 36 to the work floor
level where the compressed shingles are removed from the caulk
plates by suitable means such as a vacuum lift.
The shingles are then passed through suitable saws
to trim their edges. Normally since the mat portions 12' are
each compressed into a plurality of shingles the now compressed
mat portions must be cut into individual pieces. The individual
shingles may now undergo further fabrication which may include
waterproofing through use of struts and other similar mater-
tats. The caulk plates pass by annular conveyor (not shown)
through a cleaning station and to a station where caulk plate
release agent is again applied. Thereafter the caulk plates
are recycled to form additional shingles. The singles may be
secured together in bundles so that after sufficient curing at
ambient conditions (60 to FOE they may be shipped.
A modification of the above arrangement is preferably
utilized. In this arrangement a series of molds may be
carried beneath a dispensing hopper and filled with the
material to be pressed similarly to the procedure described
above. After compression and trimming of the excess material
from the molds, they can be passed over a scale to ascertain
that each is loaded with a sufficient amount of material.
Thereafter, the plurality of the molds are stacked in a group
of a desired number which may be, for example, twenty-four
molds. These are pressed together in a conventional hydraulic
press and stress rods applied to maintain the stack in its
compressed condition. This stack is then passed through a
I heating tunnel in which a steam atmosphere is maintained so as
to heat the molds and, more particularly, the port land
-33-
~919 KSK:jlb
I
~%04
cement-fiber mixture to the desired setting temperature. After
a proper time within the oven, the stacks are discharged and
disassembled and the molded products removed from the molds
which can then be recycled for further processing. The
molded products are trimmed and subjected to such further
fabrication as may be desired.
Having described preferred embodiments of the combo-
session of matter, improved building materials, and method of
producing the same, it will be apparent to those skilled in the
art that the invention permits of modification in both arrange-
mint and detail. however, the present invention should be
limited only in accordance with the scope of the following
claims.
-34-
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TABLE VI
Sample TriethanolamineMOR
(a) (% of cement present)
8-309-1 0.10 1582
8-309-2 0.25 1287
8-309-3 0.40 1087
8-309-4 -- 1271
.
(a) ~11 samples consisted of 90 g. fir hammer-
milled planer shavings 1/4" screen, mixture
content = 26.4%, 20 ml. of 20~ w/w alum,
15 ml. of 20~ w/w sodium dichromate, 10 ml.
water, 20 ml. of 2:1 din. of byway', water-
glass, an 135 g. Type III cement. Pleasured
amounts of triethanolamine were added in a
total of 14 ml. of water in each case.
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