U.S. patent number RE33,773 [Application Number 07/570,193] was granted by the patent office on 1991-12-17 for method of manufacturing a sag-resistant bonded particulate matter.
This patent grant is currently assigned to American Cyanamid Company. Invention is credited to Gregory G. Borsinger, Gerald J. Guerro.
United States Patent |
RE33,773 |
Guerro , et al. |
December 17, 1991 |
Method of manufacturing a sag-resistant bonded particulate
matter
Abstract
A method for the production of improved bonded particulate
articles, and the articles so produced, are disclosed.
Specifically, the manufacture of particulate articles having a
reduced tendency to undergo humidity-induced sag is disclosed.
These articles have utility in such application as ceiling
tiles.
Inventors: |
Guerro; Gerald J. (Trumbell,
CT), Borsinger; Gregory G. (Boonton, NJ) |
Assignee: |
American Cyanamid Company
(Stamford, CT)
|
Family
ID: |
26971140 |
Appl.
No.: |
07/570,193 |
Filed: |
August 20, 1990 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
299284 |
Jan 23, 1989 |
|
|
|
Reissue of: |
433984 |
Nov 15, 1989 |
04942085 |
Jul 17, 1990 |
|
|
Current U.S.
Class: |
442/85;
427/393.6; 427/385.5 |
Current CPC
Class: |
C04B
41/63 (20130101); D21H 19/26 (20130101); C09D
161/24 (20130101); C04B 41/009 (20130101); C04B
41/488 (20130101); C04B 41/4811 (20130101); D21J
1/08 (20130101); C04B 41/488 (20130101); C04B
41/4803 (20130101); C04B 41/50 (20130101); C04B
41/009 (20130101); C04B 30/02 (20130101); C09D
161/24 (20130101); C08L 2666/26 (20130101); Y10T
442/2213 (20150401) |
Current International
Class: |
C04B
41/45 (20060101); C04B 41/63 (20060101); C09D
161/24 (20060101); C09D 161/20 (20060101); C04B
41/48 (20060101); D21H 19/00 (20060101); D21J
1/08 (20060101); D21J 1/00 (20060101); D21H
19/26 (20060101); C04B 41/60 (20060101); D04H
001/58 () |
Field of
Search: |
;427/385.5,393.6
;428/288,290 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lusignan; Michael
Attorney, Agent or Firm: Flynn; Steven H.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application .Iadd.is a reissue application of our original
U.S. Pat. No. 4,942,085 dated July 17, 1990, Ser. No. 07/433,984,
filed Nov. 15, 1989, which .Iaddend.is a continuation-in-part
application of U.S. Ser. No. 07/299,284 filed Jan. 23, 1989, now
abandoned.
Claims
We claim:
1. A method of preventing or minimizing humidity-induced sag in
bonded particulate substrates comprising applying to at least one
side of said particulate substrate a coating composition comprising
an aqueous dispersion of a mixture of an effective amount of a
glyoxal resin or derivative thereof and an effective amount of a
starch compound .Iadd.which contains less than about 50% by weight
of insolubles.Iaddend., and an effective amount of a filler
material, and curing said coating composition.
2. The method of claim 1 wherein said glyoxal resin of said coating
composition is selected from the group consisting of dimethylol
dihydroxy ethylene urea, partially akylated dimethylol dihydroxy
ethylene urea alkylated dimethylol dihydroxy ethylene urea and
tetramethylol glycoluril.
3. The method of claim 2 wherein the glyoxal resin is dimethylol
dihydroxy ethylene urea.
4. The method of claim 1 wherein said substrate comprises processed
fiberous material.
5. The method of claim 1 wherein said starch component is selected
from the group consisting of starches derived from corn, potatoes,
waxy maize, sorgum and wheat.
6. The method of claim 1 wherein said starch component comprises a
high amylopectin starch. .[.7. The method of claim 1 wherein said
starch components contains less than about 50% weight percent of
insolubles..].
The method of claim 1 wherein the filler comprises an alumina
silicate.
. The method of claim 1 wherein the filler is selected from the
group consisting of alkali metal carbonates, kaolin, bentonite,
clays, silica,
mineral wool and mixtures thereof. 10. The method of claim 1
wherein the
filler is silica. 11. The method of claim 1 wherein the glyoxal
resin and said starch component are present in amounts ranging from
about 1:3 to
about 2:1 by weight. 12. The method of claim 11 wherein the glyoxal
resin and said starch component are present in amounts ranging from
about 2:3 to
about 3:2 by weight. 13. The method of claim 1 wherein the coating
composition further comprises an acid catalyst which is present in
amounts ranging from about 1 to about 50 weight percent based upon
the weight of
the glyoxal resin and said starch compound. 14. The method of claim
13 wherein the catalyst is selected from the group consisting of
zinc nitrate, zirconium ammonium carbonate, ammonium sulfate and
mixtures
thereof. 15. The method of claim 1 wherein the coating composition
is applied to said substrate in quantities such that subsequent to
its curing it will form a layer upon said substrate having a weight
of about 1 to
about 100 grams/ft.sup.2. 16. The method of claim 15 wherein the
coating composition is applied to said substrate in quantities such
that subsequent to its curing it will form a layer upon said
substrate having a
weight of about 5 to about 40 grams/ft.sup.2. 17. The method of
claim 1 wherein curing of said coating composition is conducted at
temperature ranging from about 300.degree. F. to about 700.degree.
F. for a period of
between about 0.5 to about 4 minutes. 18. A method of preventing or
minimizing humidity-induced sag in bonded particulate substrates a
coating composition comprising an aqueous dispersion of an
effective amount of mixture of a resin selected from the group of
dimethylol dihydroxy ethylene urea, tetramethylol glycoluril and
mixtures thereof, an effective amount of a starch .Iadd.which
contains less than about 50% by weight of insolubles, .Iaddend.and
an effective amount a filler selected from the group consisting of
kaolin, bentenite, clays, alkali metal carbonates and mixtures
thereof, said dimethylol dihydroxy ethylene urea and starch being
present in about a 1:1 weight % ratio and said composition being
applied in quantities sufficient to result, upon curing, in a layer
upon said substrate having a weight of about 5 to about 40
grams/ft.sup.2 of substrate, and curing said composition at a
temperature of between about 250.degree. F. to about 375.degree. F.
for a time sufficient to result in
curing of said composition. 19. A bonded particulate article
resistant to humidity-induced sag produced in accordance with the
method of claim 1.
A bonded particulate article resistant to humidity-induced sag
produced in accordance with the method of claim 18.
Description
FIELD OF INVENTION
This invention relates to a method of manufacturing improved bonded
particulate articles and to the articles so produced. More
particularly, the present invention relates to a method of
manufacturing improved particulate tiles which possess a reduced
tendency to exhibit humidity-induced sag and to the particulate
tiles so produced.
BACKGROUND OF THE INVENTION
Maintaining stiffness or rigidity of bonded particulate tile
articles under high humidity conditions has long been a problem in
the particulate tile industry. This problem is of particular
concern since the articles are typically used in ceilings and
supported only around their perimeters. Humidity weakens the tile
and due to the perimeter-only support often induces an unacceptable
sag of the tile.
The resistance of particulate tiles to moisture has previously been
improved by applying a coating comprised of a melamine-formaldehyde
resin. However, use of this resin, due to its formaldehyde content,
is of concern due to the existence of regulations involving worker
exposure during production of the resin and its application to the
particulate tiles. Moreover, the environmental hazards associated
with the use of this resin does not end with the manufacturing
process since tiles bearing this coating release noxious and
undesirable vapors under conditions such as those encountered in
fires. Less noxious materials which exhibit satisfactory
performance with regard to preventing humidity-induced sag of the
particulate tiles to which they are applied have not heretofore
been found.
U.S. Pat. No. 4,611,445 discloses a ceiling tile resistant to sag
when exposed to a fire comprising mineral wool fibers having
distributed therein from about 11% to about 6% by weight, based on
the weight of the fibers, of lithium carbonate or the fused
decomposition product thereof. This coating, however, is not useful
in preventing humidity-induced sag.
Various methods have been utilized in the corrugated paper art to
reduce the degradation of paper strength due to moisture contact.
Impregnating paper with certain resins, e.g. ureas, melamines, and
phenolics, is known, but the use of such resins has only limited
utility in the manufacturing of particulate tiles because these
resins cure at normal paper machine temperatures and tiles coated
therewith become excessively brittle during their processing.
Moreover, many of these processes use coatings as noxious as those
of which we seek to avoid to use.
U.S. Pat. No. 4,400,480 relates to a method of preparing water
resistant paperboard through use of a crosslinking additive for
starch-based adhesive compositions. These compositions are prepared
by reacting acetone and formaldehyde under aqueous alkaline
conditions at 20.degree.-380.degree. C. in a molar ratio of 1 mole
acetone: 2-5.5 moles of formaldehyde. An effective amount of free
formaldehyde is reduced to about 0.1-2% by weight. The resulting
reaction product can then be added to a starch-based adhesive or
first mixed with dimethylol dihydroxy ethylene urea. Due to its
formaldehyde content, this resin has the same environmental and
exposure concerns discussed earlier and therefore does not
represent an improvement over the currently practiced art.
U.S. Pat. No. 4,600,439 discloses a coating composition for paper
or cardboard, comprising a fluidizing agent and an undepolymerized
starch, optionally modified, a synthetic product, such as
polyvinylalcohol, or a protein, such as casein or soya
proteins.
U.S. Pat. No. 3,858,273 discloses a method of improving the wet
rigidity of corrugated paperboard through its impregnation with a
slow-curing glyoxal-based resin in the presence of a catalyst and,
optionally, an extender, such as a starch.
U.S. Pat. No. 3,288,631 discloses a method for the production of
non-woven fiber webs that are stable in the presence of water
comprising a water-soluble bonding agent having both hydroxyl- and
carbonyl-groups and a water-soluble resin and metal salt capable of
reacting with the aforementioned groups.
The above-mentioned paper coating methods are inadequate for use in
the production of sag resistant tiles due to their failure to
impart adequate moisture resistance and/or rigidity to a tile,
thereby allowing the tile to exhibit an unacceptable degree of
humidity-induced sag.
Unexpectedly, it has now been discovered that a class of materials
previously used in the manufacture of paper products is useful in
the prevention of humidity-induced sag in bonded particulate
articles, such as ceiling tiles.
SUMMARY OF THE INVENTION
The present invention relates to a method of preventing or
minimizing humidity-induced sag in bonded particulate articles
comprising applying to at least one side of a particulate substrate
a coating composition comprising water, a binder resin comprising
the reaction product of glyoxal resin or derivative thereof and a
starch, and a filler material and then curing the coating
composition on said particulate substrate.
The present invention further relates to bonded particulate
articles which are resistant to humidity-induced sag which are
produced in accordance with the method claimed herein.
DETAILED DESCRIPTION
The substrates useful in the practice of the claimed are those such
as those present in commercially available particulate tiles. These
substrates are generally comprised of processed fiberous materials
such as mineral wool as disclosed in U.S. Pat. No. 4,611,445. These
substrates can be found in commercially available dropped ceiling
tiles currently used in residential construction.
The binder resin useful in the production of the coating
composition and the practice of the present invention comprises
resin component and a starch component. The resin component of this
invention may be any suitable slow-curing glyoxal resin or
derivative thereof. Examples include the reaction product of
glyoxal, urea, and formaldehyde. This component may be prepared,
for example, by first heating the glyoxal resin and the urea to
form a monourein which is then treated with formaldehyde or by
reacting glyoxal and formaldehyde and then adding the urea. Typical
compounds useful as the resin component include, but are not
limited to, dimethylol dihydroxy ethylene urea, partially alkylated
dimethylol dihydroxy ethylene urea wherein said alkyl group contain
from 1 to about 8 carbon atoms, alkylated dimethylol dihydroxy
ethylene urea wherein said alkyl group contain from 1 to about 8
carbon atoms, and tetramethylol glycoluril. Preferred are
dimethylol dihydroxy ethylene urea and tetramethylol
glycoluril.
The starch component of the binder resin may be selected from any
of the several starches, heretofore employed in starch adhesive
compositions. Suitable starches include, for example, those
starches derived from corn, potato, waxy maize, sorgum, wheat, as
well as high amylopectin starches and the various derivatives of
those starches. Hence, among the applicable starches are included
the various starch derivatives such as ethers, esters, thin-boiling
types prepared by known processes such as phosphorylation, mild
acid treatments and oxidation. The starch component of the binder
resin should further resist retrogradation. High solids, low
viscosity starches containing less than about 50% by weight of
insolubles are preferred. Particularly preferred is potato
starch.
The fillers useful in the practice of the instant invention are not
critical and may comprise organic fillers, inorganic fillers or
mixtures thereof. They may generally be selected from such
materials as alumina silicates, alkali metal carbonates, clays,
silica, mineral wools and and mixtures thereof, many of which are
commercially available. Preferred are fillers with low acid demand.
Most preferred are fillers such as silica, kaolin, bentonite,
mineral wools and clays.
The resin and starch components of the binder resin are present in
amounts ranging from about 1:3 to about 2:1 parts by weight. More
preferably, they are present in amounts ranging from about 2:3 to
about 3:2 on the same basis. Most preferably, they are present in
equivalent amounts.
The coating composition may further comprise any one or a
combination of a wide variety of acid or latent acid catalysts,
such as for example metal salts, amine hydrochlorides, carboxylic
acids, hydroxy-substituted carboxylic acids, alkoxy-substituted
carboxylic acids, and the like, and mixtures thereof. Examples
include, but are not limited to, magnesium chloride, magnesium
nitrate hexahydrate, magnesium acetate tetrahydrate, zinc chloride,
zinc nitrate, zinc borofluoride, zinc silicofluoride, zinc nitrate
hexahydrate, zinc acetate dihydrate, ammonium chloride, ammonium
nitrate, ammonium sulfate, ammonium phosphates, sodium hydrogen
sulfate, potassium persulfate, strontium nitrate, zirconium
acetate, zirconium ammonium carbonate, zirconium oxychloride,
aluminum acetate, chromium acetate, tartaric acid, citric acid,
oxalic acid, lactic acid, succinic acid, valeric acid, maleic acid,
phosphoric acid, boric acid, sulfonic acid, perchloric acid,
persulfuric acid, p-toluenesulfonic acid, methoxyacetic acid,
hydroxybutyric acid, glycolic acid, the hydrochloride of
2-amino-2-methyl-1-propanol, and the like, and their mixtures. The
catalyst is used in an amount ranging from about 1 to about 50, and
preferably about 12 to about 15, percent based on the total weight
of the binder resin.
The coating compositions of this invention are aqueous dispersions
prepared by mixing water, the binder resin components, and the
catalyst if employed. The order of addition of these materials is
not critical. The coating composition should contain 20-75 percent
by weight of solids (i.e. binder resin and filler) and preferably
30-60 percent on the same basis.
The coating composition is applied to at least one side of the
particulate substrate in the practice of the present invention. The
coating composition should be applied such that subsequent to its
curing, it forms a layer having a dry coating weight of at least
about 1 to about 100 grams/ft.sup.2 on said substrate. More
preferably, the coating composition is present in a dry coating
weight of at least about 5 to about 40 grams/ft.sup.2.
Application of the coating composition to said substrate may be
accomplished in a number of ways all well known is the art. For
example, it may be sprayed on the substrate or applied to said
substrate by way of roller(s) contacting both said coating
composition and said substrate. The use of a combinstion of spray
and roller application is further within the scope of the present
invention.
The coated substrate is then heated to a temperature of about
200.degree. to 700.degree. F., preferably from about 250.degree. to
375.degree. F., for a time suitable to result in its cure. A time
period of about 30 seconds to 4 minutes is suitable while a period
of about 30 seconds to 2 minutes is preferred. As used herein,
curing denotes the promotion of the formation of a reaction product
of said starch and the glyoxal resin or derivative thereof.
The following Examples illustrate several embodiments of the
present invention and are not to be construed as a limitation of
its scope. All parts and percentages are by weight unless otherwise
indicated. All temperature values are given in degrees Celsius
unless otherwise noted.
EXAMPLES
Definitions
Resin A is a melamine/formaldehyde resin marketed by American
Cyanamid Company under the tradename Aerotru, 23.
Resin B is a mixture of dimethyol dihydroxy ethylene urea marketed
by American Cyanamid Company under the designation of Aerotex 900
and a potato starch which had previously been boiled at a
temperature exceeding its gelatinazation temperature in a 50:50
weight ratio.
Resin C is a resin previously employed in the paper coating art
consisting of a 70:30 mixture of polyacrylamide and glyoxal.
Resin D is a mixture of a 1:9 weight ration of a urea glyoxial
derivative marketed by American Cyanamid Company under the
designation Parez 802 and an acid hydrolyzed starch containing
70-85% insolubles.
Resin E is the reaction of a 1:1 weight ratio of dimethylol
dihydroxy ethylene urea marketed by American Cyanamid Company under
the designation of Aerotex 900 and an acid hydrolyzed starch
containing 70-85% insolubles.
Composition A is an aqueous dispersion containing a mixture of a
Resin A and alumina silicate in a 1:3 ratio. A catalytic amount of
ZnNO.sub.3 was used in its preparation.
Composition B is an aqueous dispersion containing a mixture of a
Resin B and alumina silicate in a 1:3 ratio. A catalytic amount of
ZnNO.sub.3 was used in its preparation.
Composition C is an aqueous dispersion containing a mixture of a
Resin C and alumina silicate in a 1:2 ratio. A catalytic amount of
ZnNO.sub.3 was used in its preparation.
Composition D is an aqueous dispersion containing a mixture of a
Resin D and alumina silicate in a 1:1 ratio. A catalytic amount of
ZnNO.sub.3 was used in its preparation.
Composition E is an aqueous dispersion containing a mixture of a
Resin E and alumina silicate in a 1:3 ratio. A catalytic amount of
ZnNO.sub.3 was used in its preparation.
Composition F is identical to Composition B except that the ratio
of Resin B to filler is 1:2.
COMPARATIVE EXAMPLE 1
A 4.times.2 foot particulate ceiling tile was coated with
Composition A on one side thereof through the use of a pilot roll
coater. The Composition was then cured at a temperature of about
400.degree.-600.degree. F. for about 1-2 minutes. The coating was
present in a dry coating weight of about 8-12 g/ft.sup.2.
The coated tile was then installed in the ceiling of a
humidity-controlled chamber such that the uncoated side of the tile
was exposed to the interior of the chamber. The tile was secured in
place through the use of a supporting flange around its entire
perimeter. The relative humidity of the chamber's interior was then
varied between about 85% and about 35% several times over a period
of several hours. The relative humidity of the chamber was then
adjusted to and maintained at a value of about 35% for a period
sufficient to allow the tile to stabilize. The deflection of the
tile was then measured. Deflection as used herein denotes the
vertical distance from the center of the tile surface normal to the
plane of the supporting flanges. As it represents the degree of
humidity-induced sag of the tile, less tile deflection denotes
improved performance of a coating composition. Tile deflection with
the use of Composition A was found to be 81 mils.
EXAMPLE 1
The procedure of Comparative Example 1 was repeated except that
Composition B was used in place of Composition A.
Tile deflection was determined to be about 125 mils.
COMPARATIVE EXAMPLE 2
The procedure of Comparative Example 1 was repeated except that
Composition C was used in place of Composition A.
Tile deflection was determined to be about 420 mils.
COMPARATIVE EXAMPLE 3
The procedure of Comparative Example 1 was repeated except that
Composition D was used in place of Composition A.
Tile deflection was determined to be about 398.
COMPARATIVE EXAMPLE 4
The procedure of Comparative Example 1 was repeated except that
Composition E was used in place of Composition A.
Tile deflection was determined to be about 410.
EXAMPLE 2
The procedure of Comparative Example 1 was repeated except that
Composition F was used in place of Composition A.
Tile deflection was determined to be about 44.5 mils.
The following observations may be made upon reviews of the above
Examples and Comparative Examples.
First, the coating composition of the present invention
(Composition B) gives satisfactory results. However, at a given
binder resin to filler ratio, it does not minimize tile deflection
to the degree accomplished by the currently-employed
melamine/formaldehyde-containing coating composition (Composition
A). However, results superior to those exhibited the use of
Composition A can be achieved through the use of materials within
the scope of the present invention by employing decreased binder to
filler ratios, (e.g. Composition F).
Secondly, Composition C, which is material typically used in the
paper coating industry, was shown to be wholly inadequate for the
production of sag-resistant coated particulate materials.
Finally, coating compositions containing starch components having a
high content of insoluble components (Composition D) are further
shown to exhibit unsatisfatory performance.
* * * * *