Note: Descriptions are shown in the official language in which they were submitted.
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WATER REPELLENT FIBER BOARDS
Field of Invention
The field relates to an acoustic building material or
fiber board as well as a method for its manufacture, and more
particularly, to fiber board having increased water repellency
and improved physical properties. The fiber board includes a
reactive silicone homogeneously dispersed within the board
construction.
Background of Invention
The acoustic building material or fiber board may be in
the form of a ceiling tile, a ceiling panel, a wall panel or
wall tile as are well known in the building trades. The
boards are prepared from a slurry of fibers, fillers, binders
and other ingredients.
The boards are typically prepared using the slurry in a
water felting process as is known in the art. A dispersion of
fiber, filler, binder and other ingredients flow onto a
moving, porous support such as a Fourdrinier forming machine
for dewatering. The dispersion is dewatered first by gravity
and then by vacuum suction. The wet base mat is dried in
heated convection drying ovens and the dried material is cut
to the desired dimensions and optionally coated to produce the
acoustic panels and tiles.
For convenience, the invention is described below with
particular reference to a wall panel of the type frequently
employed as a division wall in a cubical wall or other room
divider. A wall covering is typically applied to the division
wall using a water-based adhesive.
It is known to provide wall panels as a fibrous panel
structure including a base mat or core manufactured from base
fibers, fillers, and binders. The base fibers are usually
mineral fibers such as mineral wool or glass fibers. Also,
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c fiber may be used. Frequently, the organic fiber is
cellulosic fiber in the form of recycled newsprint. The
fillers are commonly perlite, clay, calcium carbonate, or
stucco (gypsum). The binder is typically starch, latex, or
similar materials. These materials or ingredients are
combined in aqueous slurry, and processed in a water felting
process as described above. Upon drying, the binder forms
bonds with the other materials to provide a fibrous network
that provides strength and rigidity to the core.
To be used as a typical division wall, the core should
have sufficient strength and rigidity to remain planar in its
panel configuration during use. Preferably, the panel density
is sufficient to provide the perception of solidarity
associated with an interior structural wall. For example, the
wall density should be greater than about 16 pounds per ft3
(pcf).
In addition to these physical characteristics, the
division wall should display water repellency sufficient to
withstand liquid contact imposed in subsequent wall finishing
and/or wall use applications. However, the described
constructions tend to be porous and hydrophilic, susceptible
to moisture absorption and to the ingress of liquid applied to
the wall surface. It is customary to adhesively apply a wall
covering, such as fabric, to division wall surfaces to provide
a desired aesthetic appearance.
Frequently, the fabric or other wall covering is applied
using a water-based adhesive. The water absorbency or natural
take-up of water by the panel has been found to hinder the
achievement of the desired strong adhesive bond between the
wall covering and the panel. In many instances of
insufficient adhesion, it is believed that the water-based
adhesive is prematurely removed from the adhesion interface by
absorption or uptake into the panel without forming a strong
adhesive bond.
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n order to retard the ingress of water-based adhesive
and provide a better bond, sizing agents are used with the
panel to act as water repellants. Typical sizing materials
include paper sizing materials such as imidazolidone reactive
sizing agents.
The above sizing agents improve the bond between the wall
covering and division wall, but they are not entirely
satisfactory because relatively large amounts of product are
required for effectiveness. Further, the prior agents are
characterized by an undesirable level of volatile organic
component or VOC during drying or curing. In addition, the
MSDS indications of these products respectively include a
formaldehyde content of 0.3% and 0.113%.
Although current products are within applicable
standards, it is desirable to reduce VOC and formaldehyde in
both processing and final product. For example, the
imidazolidone based sizing agents contribute to the VOC and
are believed to be responsible for a "blue haze" observed at
the production plant exhaust system. It is desirable to
reduce or eliminate the haze. In any case, imidazolidone
agents may contribute to both process VOC and product
formaldehyde.
US Patent 5,964,934 teaches that the water retention of
expanded perlite contained in the composition of acoustic
tiles may be reduced by initially spray coating the perlite
with a silicone and drying the treated perlite at an elevated
temperature to cure the silicone. The composition containing
the treated perlite may be formed into an acoustic tile using
a water felting process. The water retention of the base mat
containing the silicone treated perlite is reduced without
affecting the physical properties of the resulting tile. The
reduction in water retention is indicated to enable increased
manufacturing line speeds.
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S Patent 5,539,028 discloses the incorporation of
silicone fluid comprising polymethylhydorgensiloxane (PMHS)
into the slurry used to form fiberboard for improving the
water resistance without affecting the physical properties of
the board. The fiberboard may contain mineral fiber, non-
fibrous inorganic filler, organic fiber and a binder such as
starch.
Brief Description of the Invention
It has been discovered that reactive additives may be
incorporated in acoustic building materials or fiber boards to
improve water repellency. The reactive additives also improve
the physical properties of the material or board.
The reactive additives may be included in division wall
ingredients at relatively low levels to provide water
repellency. Further, the level of water repellency achieved
is sufficient to provide improved adhesion for subsequently
applied wall coverings using water based adhesive. The
additive is homogenously dispersed in the aqueous slurry used
to form the core or base mat to provide the desired water
repellency.
The reactive additives comprise reactive silicones or
silicone fluids, and particularly those having a
polydimethylsiloxane backbone with substituted reactive side
chains and/or ends. For example, hydrophilic side chains such
as polyether side chains. One preferred silicone includes
alpha-iso-tridecly-omega-hydroxy polyglycolether side chains.
Another preferred silicone has a similar polyether side chain
and further includes an amino-functional polydimethylsiloxane.
It has also been discovered that the homogenous
dispersion of the reactive silicone in the slurry composition
provides a desired water repellency that is superior to that
of the imidazolidone agents. Further, the reactive silicone
has been found to reduce the cost of the water repellant
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ent in wall panel applications due to lower usage and
increased effectiveness.
The reactive silicone also improves the mechanical
properties of the panel. Particularly, improved strength
characterized by increased modulus of rupture (MOR) and ball
hardness is achieved. This is most unexpected since the prior
art use of polymethylhydorgensiloxane (PMHS) silicone does not
result in improved panel physical properties. In addition, no
deleterious effect on other physical properties has been
observed at the required silicone levels for water repellency.
It has been found that the reactive silicones provide the
desired water repellency for the above adhesion purposes at
concentrations also providing improved physical properties.
Accordingly, the resulting division wall has increased water
repellency and improved strength as indicated by increased
modulus of rupture.
Further, the reactive silicones tend to reduce, if not
eliminate, the objectionable VOC emissions associated with
processing. In fact, preferred silicones are characterized by
a water by-product upon curing so as to substantially
eliminate all organic emissions.
In typical compositions, the fiber and filler components
comprise the primary ingredients. However, a wide variation
of ingredients may be employed. For example, the following
chart summarizes typical ceiling and wall compositions. It
should be appreciated that the compositions may contain one or
more of the illustrative types of fiber, filler, binder or
reactive silicone as listed in the following table. The
percentages herein are weight percent based on solids unless
otherwise indicated by comment or context.
Ingredient Range % Preferred %
Fiber
Mineral wool 5 - 80% 30-40%
fiber 5 - 80% 30-40%
Cellulose (recycle paper) 0 - 25% 15-20%
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tiller
Perlite 15 - 70% 25-35%
Clay 0 - 25% 0-10%
Calcium carbonate 0 - 20% 5-15%
Binder
Corn starch 3 - 18% 5-15%
Latex 0 - 8% 0-5%
Reactive silicone
PDMS (polyether) 0.02 - 0.5% 0.1 - 0.15%
PDMS (polyether/amino) 0.02 - 0.5% 0.1 - 0.15%
The fiber, filler and binder components are combined in
aqueous slurry at a level of about 3% to 6% solids in a known
manner. The reactive silicone is added and homogenously
blended into the slurry. Hydrophilic groups present in the
silicone enhance the uniform distribution of the silicone and
the thorough penetration and wetting of the fiber and filler
slurry ingredients.
Detailed Description of the Invention
The division walls or wall panels of interest herein
include base fibers that are usually mineral fibers such as
mineral wool or glass fibers. Also, organic fiber such as
cellulosic fiber derived from recycled newsprint may be used.
The fillers are commonly perlite, clay, calcium carbonate, or
stucco. The binder is typically starch, latex, or similar
materials. These materials or ingredients are typically
combined in aqueous slurry, and processed in a water felting
process as described above.
A number of water repellents or sizing agents were
evaluated in order to resolve the adhesion problems
encountered during the subsequent application of a wall
covering using a water-based adhesive. Also, the contribution
of the water repellants or sizing agents to the processing and
final use levels of VOC and formaldehyde was determined. The
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ted agents include the following commercially available
products.
.Imidazolidone A - an imidazolidone reactive sizing. The
sizing is supplied as an emulsion that contains 45% solids and
it was evaluated at an addition rate of about 0.75% based on
the dry stock weight.
.Imidazolidone B - An imidazolidone reactive sizing.
This sizing is supplied as an emulsion that contains 30%
solids and it was evaluated at an addition rate of about
1.125% based on the dry stock weight.
.SILRES BS 1042 is a reactive PDMS supplied by Wacker
Chemie AG as an emulsion containing 60% solids. The silicone
has an alpha-iso-tridecly-omega-hydroxy polyglycolether side
chain and the curing by-product is water.
.SILRES BS 1306 is a reactive PDMS also supplied by
Wacker Chemie AG as an emulsion containing 55% solids. The
silicone has an alpha-iso-tridecly-omega-hydroxy
polyglycolether side chain and amino-functional side chains.
The curing by-product is methanol.
.PARAFFIN WAX A - a non-curing paraffin wax emulsion.
.PARAFFIN WAX B - a non-curing paraffin wax emulsion.
Tappi Board Making Procedure
Three wall panel Tappi boards were prepared using the
following formulation: 35% mineral wool; 30% perlite; 18%
recycled newsprint; 13% corn starch and 4% clay. The stock
consistency was 4.5% solids, and 0.08% flocculent was added to
the slurry. The boards were formed with a 0.5" thickness and
a target density of 17 pounds/ft.3 (pcf). Different grades of
wall panel may be simulated in accordance with product
densities ranging from 16 pcf to 24 pcf and thicknesses
ranging from about 3/8" to about 3/4".
After forming the Tappi boards, the wet boards were dried
in an air-circulating oven for 45 minutes at 600 F.
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fter, the drying was completed at 300 F for 3 hours.
The Tappi boards were cut into 3" x 10" and 4"x 4" samples and
tested.
Test Procedures
The MOR and ball hardness measurements were carried out
on an APL Instron (Model 1130). The 3" x 10" samples were
used for the MOR measurement. In the hardness test, a 2"
diameter steel ball is pressed at a constant rate into the
board to a depth of 1/8" and the maximum force is reported.
The 4" x 4" square samples were used for the water
absorption test. The samples were first weighed individually,
and then immersed in 70 F tap water and held at a depth of
approximately 6-8 inches below the water surface for 1 hour.
After 1 hour, the samples were taken from the water and re-
weighed after excess surface water had been removed by tapping
with a dry paper towel.
Absolute water absorption is expressed as the weight
difference before and after immersion for each sample. The
percent water absorption is the percent of water of absorbed
compared to the original dry weight of the test sample.
The test results are reported in the following Table 1.
TABLE 1:
Amount iiii % Water
:
:
: iAdditive ii (wet : Density 'Abs. water
Uptake i:i1MOR:i Hardness
(solid%) wt%) 1 (1b/ft^3) uptake (g) (
/0) DO (psi) 1111 (Ibf) hl
1 none 0.00% 16.79 69.38 184%
248.9 189.1
2 Imidazolidone A 0.75% 17.06 5.90 16% 248.9
209.0
3 BS 1306 0.40% 16.93 3.78 10% 248.4
187.8
4 BS 1306 0.30% 16.50 4.34 11% 270.2
197.8
5 BS 1306 0.20% 16.93 4.32 12% 262.0
227.2
6 BS 1306 0.10% 16.42 5.91 16% 268.4
226.3
7 BS 1042 0.40% 16.44 4.31 11% 259.5
220.4
8 BS 1042 0.30% 16.61 4.59 12% 240.0
215.1
9 BS 1042 0.20% 16.70 4.30 12% 254.6
216.1
10 BS 1042 0.10% 16.79 5.35 14% 258.0
221.3
11 Paraffin Wax A 3.00% 16.79 7.93 21% 244.8
215.1
12 Paraffin Wax A 2.00% 16.55 13.41 35%
215.7 203.3
13 Paraffin Wax A 1.50% 16.58 15.20 39%
255.3 199.5
14 Paraffin Wax A 1.00% 16.46 14.47 51%
218.2 212.3
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'araffin Wax B 3.00% 17.23 7.73 21% 221.7
206.3
i'amffinWax13 2.00% 16.82 9.97 27% 227.1
192.3
17 PamffinWax13 1.50% 16.87 21.54 57% 230.4
202.4
18 PamffinWax13 1.00% 16.82 9.97 100% 227.1
192.3
19 ImidazolidoneA 0.50% 16.87 21.54 20% 230.4
202.4
20 mxie 0.00% 16.83 30.80 84%0 254.5
216.90
Based on the solids in the slurry
Referring to Table 1, the overall test results show the
effectiveness of the silicones as water repellants even at the
low concentrations employed. Also, there is an increase in
the MOR values as compared with the controls and the wax based
products. The silicones did not adversely affect the physical
properties of the boards.
Three Tappi boards were prepared as described above to
evaluate the VOC processing and final product levels
characteristics. The board composition included the following
ingredients: 35% mineral wool; 30% perlite; 18% recycled
newsprint; 13% corn starch and 4% clay. The stock consistency
was 4.5% solids, and approximately 0.08% a flocculent was
added. The boards were formed with a thickness of 0.5" and a
target density of 23 pounds/ft.3 (pcf). This formulation was
varied to provide Tappi board Sample 1 containing no water
repellant, Tappi board Sample 2 containing 0.45% Imidazolidone
A and Tappi board Sample 3 containing 0.12% SILRES BS 1042.
After forming the wet Tappi board, a 3.625" x 5.5" sample
was cut from each board, placed in a sealed plastic container
and stored in a refrigerator at about 40 F. prior to the VOC
emission measurement.
For purposes of measuring the VOC contribution of the
various agents, an ARCADIS brand oven system was used. The
oven system consists of an electrically heated cabinet for
receiving and drying small (e.g.4" x 6") panel samples with
the capture of the oven air for analysis. To that end, the
oven system also includes an air transport system for
delivering the oven air together with sample emissions to an
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er/detector for measuring total hydrocarbon content
(THC). Water is not included in the THC total.
Each Tappi board sample is placed in the oven at the same
location to avoid effects of uneven heating in the comparison.
The total hydrocarbon content (THC) concentration is measured
throughout the drying process for a total test duration of
about 2 hours and 5 minutes for each sample. The THC
concentration in ppm was plotted against the drying time in
seconds. The overall VOC emission is deemed equal to the area
under the THC curve verses the drying time in seconds. In
Table 2 below, the overall VOC emission is reported below in
ppm-s.
Table 2:
Wet Dry Total
Weight Weight Percent
THC Total Changed
Sample Water Repellent ........ (g) (g) dry (`)/0)
(ppm-s) (%)
type .. amount'
1 none 0.00% 145.37 54.40 37.4%
1159104 0.0%
2 Imidazolidone A 0.75% 142.87 56.44
39.5% 1609186 38.8%
SILRES BS
3 1042 0.20% 143.96 55.68 38.7%
1267064 9.3%
Wet weight % based on the solids in the slurry.
Compared to the control Sample 1, Sample 2 (containing
0.34% Imidazolidone A) and Sample 3 (containing 0.12% SILRES
BS 1042) showed increased VOC. However, the degree of VOC
increase was much less for Sample 3 than for Sample 2.
Accordingly, although the addition of a silicone water
repellent is found to increase the VOC during the drying
process, SILRES BS 1042 is preferred since it has only a
slight increase. Although not tested, it is expected that
Imidazolidone B would have an increase in VOC similar to
Imidazolidone A since they are chemically similar and require
like addition rates. As shown, the BS 1042 provides a reduced
amount of VOC as compared with the Imidazolidone A.
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trial production plant run confirmed the superior
performance of reactive silicone over the production use of
imidazolidone reactive Imidazolidone B. In the trial run,
slurry was processed on a production water felting line to
compare BS 1042 and Imidazolidone B. A slurry composition
including typical percentages of mineral wool, perlite,
recycled newsprint, corn starch and clay within the above
preferred ranges was prepared. The stock consistency was 4.5%
solids and identical flocculent was added to the compared
slurries.
A slurry flow rate of 1300 gallons per minute (gpm) was
used. In the trial run, the BS 1042 (60% % solids) was added
at a rate of 0.15 gpm and the reactive silicone is deemed to
be added at a concentration of 1.5 wt% based on the total
solids present in the slurry. In the comparative control run,
Imidazolidone B (30% solids) was added a rate of 0.40 gpm in
place of the BS 1042. In each case, about 75000 ft2 of wall
board was produced with target specifications of a thickness
equal to 0.5" and a density of 23 pcf.
(These specifications
correspond with one form of commercial product and, as noted
above, other commercial products may have different
thicknesses and densities.)
The plant exhaust system was monitored during production
for identification of the blue haze heretofore associated with
the use of water repellent agents. The blue haze was not
detected in the plant exhaust consistent with the low THC
observed above in connection with BS 1042.
A further advantage observed during the plant trial is
the reduced foam generation in the slurry during the
production of the wall board incorporating the silicone
additive. Typically, the slurry processing results in foam
accumulation even with the addition of defoamers. The
silicone agent aids the defoamers allowing elimination and/or
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ion of the amount of defoamer additive required with the
use of other water repellant agents such as Imidazolidone B.
Standard quality control tests were performed in
connection with the trial run material and the control
material. The test results are reported below in Table 3.
Table 3:
Caliper ":" Density MOR "i' ."r:"Water
(inches) (pcf) (psi) (Y000Mi. Absorpi3
Trial Sample 1 0.501 24.5 472.9 27.4 13.9g
Trial Sample 2 0.505 24.2 476.2 27.5 13.4g
Control Sample 1 0.500 252 418.9 262 10.0g
Control Sample 2 0.502 253 406.0 262 10.5g
1%Combustibles equal to amount burned-off.
2Absolute amount of water absorbed by the 4"x4" sample.
As indicated, the BS 1042 yields a much higher MOR result
as compared with Imidazolidone B. The reactive side chains of
the silicones are believed to be associated with the improved
strength. The hydrophilic side chains of the silicone may
cause improved penetration and wetting of the base mat
structure by the aqueous slurry and thereby enhance the
connection between the base mat ingredients with each other
and the cured silicone.
It should be evident that this disclosure is by way of
example and that various changes may be made by adding,
modifying or eliminating details without departing from the
fair scope of the teaching contained in this disclosure. The
invention is therefore not limited to particular details of
this disclosure except to the extent that the following claims
are necessarily so limited.
