U.S. patent application number 09/735624 was filed with the patent office on 2001-04-12 for cyclic urea-formaldehyde prepolymer for use in phenol-formaldehyde and melamine-formaldehyde resin-based binders.
This patent application is currently assigned to Georgia-Pacific Resins, Inc.. Invention is credited to Dupre, F. C., Foucht, Millard E., Freese, William P., Gabrielson, Kurt D., Gapud, Benjamin D., Ingram, W. Hayes, McVay, Ted M., Rediger, Richard A., Shoemake, Kelly A., Tutin, Kim K., Wright, James T..
Application Number | 20010000237 09/735624 |
Document ID | / |
Family ID | 27371309 |
Filed Date | 2001-04-12 |
United States Patent
Application |
20010000237 |
Kind Code |
A1 |
Dupre, F. C. ; et
al. |
April 12, 2001 |
Cyclic urea-formaldehyde prepolymer for use in phenol-formaldehyde
and melamine-formaldehyde resin-based binders
Abstract
The preparation of phenol-formaldehyde and melamine-formaldehyde
resin-based binders extended with a cyclic urea-formaldehyde
prepolymer and to products prepared using the binders. More
particularly, the invention relates to a cyclic urea prepolymer
comprising urea, formaldehyde, and ammonia or a primary amine
which, when added to a phenol-formaldehyde or melamine-formaldehyde
based resin, results in a useful binder for the manufacturer
numerous articles.
Inventors: |
Dupre, F. C.; (Atlanta,
GA) ; Foucht, Millard E.; (Stone Mountain, GA)
; Freese, William P.; (Conyers, GA) ; Gabrielson,
Kurt D.; (Liburn, GA) ; Gapud, Benjamin D.;
(Lawrenceville, GA) ; Ingram, W. Hayes; (Conyers,
GA) ; McVay, Ted M.; (Lawrenceville, GA) ;
Rediger, Richard A.; (Conyers, GA) ; Shoemake, Kelly
A.; (Conyers, GA) ; Tutin, Kim K.; (Stone
Mountain, GA) ; Wright, James T.; (Decatur,
GA) |
Correspondence
Address: |
BANNER & WITCOFF
1001 G STREET N W
SUITE 1100
WASHINGTON
DC
20001
US
|
Assignee: |
Georgia-Pacific Resins,
Inc.
|
Family ID: |
27371309 |
Appl. No.: |
09/735624 |
Filed: |
December 14, 2000 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09735624 |
Dec 14, 2000 |
|
|
|
09598894 |
Jun 22, 2000 |
|
|
|
09598894 |
Jun 22, 2000 |
|
|
|
09215742 |
Dec 17, 1998 |
|
|
|
6114491 |
|
|
|
|
60095249 |
Aug 4, 1998 |
|
|
|
60068286 |
Dec 19, 1997 |
|
|
|
Current U.S.
Class: |
428/528 |
Current CPC
Class: |
C08L 61/06 20130101;
Y10T 428/31877 20150401; C08L 2666/20 20130101; C08L 61/20
20130101; C08L 2666/20 20130101; C08L 61/28 20130101; C08L 61/20
20130101; C08L 61/28 20130101; Y10T 428/31873 20150401; Y10T
428/12146 20150115; Y10T 428/31862 20150401; C08G 14/12 20130101;
C08L 61/28 20130101; Y10T 428/31957 20150401; C08G 12/422 20130101;
C08L 61/06 20130101; Y10T 428/31895 20150401; Y10T 428/12153
20150115; C08L 61/06 20130101; C08L 75/02 20130101 |
Class at
Publication: |
428/528 |
International
Class: |
B32B 027/42 |
Claims
What is claimed is:
1. A binder comprising a phenol-formaldehyde or
melamine-formaldehyde resin modified with 1 to 95 wt % based on
resin solids of a cyclic urea prepolymer either during manufacture
of the resin or post added to the resin wherein the cyclic urea
prepolymer has a mole ratio of urea:formaldehyde:ammonia or a
primary amine of about 0.1 to 1.0:0.1 to 3.0:0.1 to 1.0.
2. The binder of claim 1 wherein the mole ratios of
urea:formaldehyde:ammonia or a primary amine are about 2.0:2.0:1.0
to 1.0:4.0:1.0.
3. The binder of claim 2 wherein the mole ratios of
urea:formaldehyde:ammonia or a primary amine are about
2.0:4.0:1.0.
4. The binder of claim 1 wherein the cyclic urea prepolymer is
prepared from urea, formaldehyde and ammonia.
5. The binder of claim 1 wherein the resin is a thermosetting
resin.
6. The binder of claim 1 wherein the cyclic urea prepolymer is
prepared by: mixing urea, formaldehyde, and ammonia or a primary
amine, and heating the mixture at an alkaline pH to about 60 to
105.degree. C. for a time sufficient to complete the reaction.
7. The binder of claim 6 wherein the pH is between about 5 and
11.
8. The binder of claim 1 wherein the binder comprises 10 to 70 wt %
of the cyclic urea prepolymer based on resin solids.
9. The binder of claim 8 wherein the binder comprises 20 to 60 wt %
of the cyclic urea prepolymer based on resin solids.
10. The binder of claim 1 wherein the resin is a
phenol-formaldehyde resin.
11. The binder of claim 10 wherein the cyclic urea prepolymer is
added to the phenol-formaldehyde resin during manufacture of the
resin.
12. The binder of claim 10 wherein the cyclic urea prepolymer is
added to the phenol-formaldehyde resin after manufacture of the
resin.
13. The binder of claim 1 wherein the binder further comprises a
latent catalyst.
14. Insulation comprising fibers and the binder of claim 10.
15. The insulation of claim 14 wherein the binder comprises 10 to
70 wt % of the cyclic urea prepolymer based on resin solids.
16. The insulation of claim 15 wherein the binder comprises 20 to
60 wt % of the cyclic urea prepolymer based on resin solids.
17. The insulation of claim 16 wherein the mole ratios of
urea:formaldehyde:ammonia or a primary amine are about 1.0:1.0:0.5
to 1.0:4.0:1.0.
18. The insulation of claim 16 wherein the phenol-formaldehyde
resin is prereacted with urea prior to combination with the cyclic
urea prepolymer.
19. The insulation of claim 16 wherein the binder further comprises
a latent catalyst.
20. The insulation of claim 16 wherein the fibers are glass fibers
or mineral wool fibers.
21. A consolidated wood product comprising a substrate and an
adhesive comprising a phenol-formaldehyde resin modified with 1 to
95 wt % based on resin solids of a cyclic urea prepolymer either
during manufacture of the resin or post added to the resin wherein
the cyclic urea prepolymer has a mole ratio of
urea:formaldehyde:ammonia or a primary amine of about 0.1 to
1.0:0.1 to 3.0:0.1 to 1.0, wherein said consolidated wood product
is selected from the group consisting of plywood, oriented strand
board, wafer board, engineered lumber, particle board, hardboard
and medium density fiber boards.
22. The consolidated wood product of claim 21 wherein the
consolidated wood product is plywood comprising at least three
plies.
23. The consolidated wood product of claim 21 wherein the
consolidated wood product is laminated veneer lumber.
24. The consolidated wood product of claim 21 wherein the
consolidated wood product is oriented strand board or wafer
board.
25. The consolidated wood product of claim 21 wherein the binder is
spray dried onto the substrate.
26. The binder of claim 12 wherein the phenol-formaldehyde resin is
a paper saturating resin.
27. The binder of claim 10 wherein the resin is a high pressure
laminating resin.
28. The binder of claim 11 wherein the resin is a high pressure
laminating resin.
29. The binder of claim 12 wherein the resin is a high pressure
laminating resin.
30. A laminate comprising a paper substrate and the binder of claim
27.
31. The binder of claim 10 wherein the binder is a coated abrasive
binder or a friction material binder.
32. A binder comprising a novolac resin and a cyclic urea
prepolymer wherein the cyclic urea prepolymer has a mole ratio of
urea:formaldehyde:ammonia or a primary amine of about 0.1 to
1.0:0.1 to 3.0:0.1 to 1.0.
33. The binder of claim 1 wherein the resin is a
melamine-formaldehyde resin.
34. Ceiling tiles comprising cellulose or mineral fiber materials
and a coating comprising the binder according to claim 33.
35. The ceiling tiles of claim 34 wherein the coating further
comprises clay.
36. The binder of claim 33 wherein the resin comprises 1 to 25 wt %
of the cyclic urea prepolymer based on resin solids.
37. Overlay paper laminates comprising a paper substrate and a
coating comprising the binder according to claim 33.
38. A molded article comprising pulp and a binder according to
claim 33.
39. A molded article comprising glass fiber or filler and a binder
according to claim 33.
40. The binder of claim 32 wherein the binder is a coated foundry
sand binder.
41. The binder of claim 1 wherein the binder is a coated foundry
sand binder.
42. The binder of claim 1 wherein the binder is a phenolic foam
resin.
Description
1. This application is a continuation-in-part application of prior
U.S. Provisional Patent Application Serial Nos. 60/095,249, filed
Aug. 4, 1998 and 60/068,286, filed Dec. 19, 1997.
BACKGROUND OF THE INVENTION
2. 1. Field of the Invention
3. This invention relates to the preparation of phenol-formaldehyde
and melamine-formaldehyde resin-based binders modified with a
urea-formaldehyde polymer containing at least 20% triazone and
substituted triazone compounds (cyclic urea prepolymer) and to
products prepared using the binders. More particularly, the
invention relates to a prepolymer comprising urea, formaldehyde,
and ammonia or a primary amine which, when added to a base resin,
results in a useful binder or adhesive for the manufacture of
numerous articles.
4. 2. Description of Related Art
5. Phenol-formaldehyde resins and melamine-formaldehyde resins are
standard resins used for many products. The choice of resin depends
on the desired properties. Phenol-formaldehyde resins are strong
and durable and relatively inexpensive, but are generally colored
resins. Melamine resins are water clear but are more expensive.
Hence they are generally used only for products whereby the color
or pattern of the substrate is maintained with a transparent
melamine protective coating or binder.
Phenol-formaldehyde Resins
6. Phenol-formaldehyde resins are used to make a variety of
products including consolidated wood products such as plywood,
engineered lumber, hard board, fiber board, oriented strand board,
and other products such as fiberglass insulation, laminates,
abrasive coatings, friction binders, foams, foundry binders, and
petroleum recovery binders. They are also used as paper saturating
resins for oil filters, overlay, paint roller tubes and the
like.
Insulation
7. Insulation is generally prepared by coating glass fibers or
mineral wool fibers with an aqueous binder solution, usually by
spraying, and passing the coated fibers through an oven where they
are compressed to the desired thickness and density, and then
permanently fixed by heat setting or curing the resin binder. The
traditional binders used in manufacturing insulation are low
molecular weight, alkaline catalyzed phenol-formaldehyde resins
fortified with formaldehyde scavengers, acid catalysts, and
coupling agents. Acid cure has been favored in the art because it
produces a glass fiber insulation having good strength and moisture
resistance characteristics.
8. It is often desirable to scavenge the free formaldehyde prior to
application. This is done for several reasons: 1) to reduce the
free formaldehyde emissions during the forming and curing of the
insulation product, 2) to reduce the free formaldehyde prior to the
addition of an acid catalyst, 3) to reduce the cost of the binder,
and 4) to improve the anti-punk properties of the resin.
9. The most common scavengers are chemical species containing a
primary or secondary amine functionality. Urea, ammonia, melamine,
and dicyandiamide are a few of the more commonly used amines. The
most common, and the most economical, amine species is urea. When
urea is used as the formaldehyde scavenger, the amount of urea
added to the resin is referred to as the extension level which is
reported as a percent of the binder solids. Binder solids consist
of phenol-formaldehyde resin solids and extender solids.
10. The addition of formaldehyde scavengers to a
phenol-formaldehyde resin requires a finite period of time to
achieve equilibrium with the free formaldehyde in the resin. The
process of reaching this equilibrium is referred to as
pre-reaction, and the time to reach the equilibrium is referred to
as the pre-react time. Pre-react times vary with temperature and
amine species. When urea is used, the pre-react times range from 4
to 16 hours depending on temperature.
11. The mole ratio of formaldehyde to formaldehyde scavenger is
also important and conditions are optimized to achieve the best
performance of the binder. When urea is used, the mole ratio of
formaldehyde to urea, the F/U, is optimally maintained between 0.8
and 1.2. If the extension level results in an F/U of less than 0.8,
the opacity increases significantly along with the ammonia
emissions. If the extension level results in an F/U of greater than
1.2, formaldehyde emissions increase and the risk of precipitation
of dimethylolurea is greatly increased. For this reason, in
traditional binders using urea as the formaldehyde scavenger (or a
combination of urea and ammonia), the extension level is dictated
by the amount of free formaldehyde in the base resin.
12. There are however disadvantages of pre-reacting resins with
urea prior to forming the binder. Because free formaldehyde
stabilizes the tetradimer in the resin, pre-reacting with urea will
reduce the % free formaldehyde in the resin, hence reducing resin
stability over time. Further, long pre-react times, as observed
when urea is used as the formaldehyde scavenger, shorten the shelf
life of the binder. In addition, pre-reacting with urea takes time,
requires pre-react tanks and binder tanks, and urea needs to be
stored in heated storage tanks. There is a need for an extender
system for phenol-formaldehyde resins that does not have the above
disadvantages.
Plywood and Engineered Lumber
13. It is also well known to use phenol-formaldehyde resins and
phenol-formaldehyde resin-extenders and fillers as plywood and
engineered lumber adhesives in the industry. Many raw materials may
be added to phenol-formaldehyde resins to improve the bond
qualities of the adhesive in plywood panels and engineered lumber
such as laminated veneer lumber, including borax, potassium
carbonate, poly-vinyl alcohol, etc. Urea has also been added to
plywood and engineered lumber resins and adhesives to improve
pre-press tack, bond quality, cost, assembly time tolerance, and
reduce formaldehyde emissions without detrimental effects to the
bonding strength of the adhesive. Urea can be added to the
phenol-formaldehyde resins up to a 5% level based upon the solid
weight of urea to the total resin weight at a 41% solids which
includes the urea. However, when urea is used at high levels of 4
to 5 wt %, the phenol-formaldehyde resin selected must have a long
assembly time (time between application of the adhesive and when
the panels are hot pressed or pre-pressed), to eliminate dryout of
the adhesive. Therefore, the use of urea in plywood resins is
generally limited to levels lower than 5%, generally equal to or
below 3%.
Oriented Strand Board
14. Spray dried oriented strand boards (OSB) and wafer board resins
are very sensitive to any extender or filler that is used in the
resin. Many attempts have been made to use small amounts of urea or
urea-formaldehyde resins as extenders in various
phenol-formaldehyde and phenol-melamine-formaldehyde resins.
Unfortunately, most of these attempts to extend the resin are not
commercially successful because the urea interferes with the
ability of the resin to be spray dried. Urea contained in the
phenol-formaldehyde resins for OSB or wafer board applications are
typically limited to 1% urea for scavenging free formaldehyde.
Otherwise the urea will affect the properties of the OSB wafer
board such as its durability.
High Pressure Laminating Resins
15. Phenol-formaldehyde resins used to manufacture high pressure
laminates are typically produced by reacting phenol and
formaldehyde using an alkaline catalyst such as sodium hydroxide.
Typical mole ratios of formaldehyde to phenol range from 1.0 to 2.5
moles of formaldehyde per mole of phenol with the preferred range
from 1.2 to 1.9 moles of formaldehyde per mole of phenol. Catalyst
levels range from 0.2% to about 6%, preferably from 0.5 to 3%.
These materials are reacted to a suitable endpoint, cooled with
vacuum, and usually distilled to remove the water present from the
formaldehyde solution as well as the water of condensation from the
polymerization reaction. They may be used in this state or an
organic solvent such as methanol can be added to reduce the %
solids and viscosity and aid in penetration of the kraft paper
substrate. Modifiers such as urea can be added to reduce residual
free formaldehyde levels. Other modifiers may also be added to
achieve specific purposes.
16. High Pressure Laminates are made from several layers of paper
that have been impregnated with thermosetting resins, dried
(B-staged), and finally cured under pressure in a heated press. The
surface of the laminate is made from a decorative paper (a solid
color or printed with a pattern) that is impregnated with a
melamine-formaldehyde resin. Underneath this surface are several
layers of kraft paper that have been impregnated with a
phenol-formaldehyde resin and function as a core for the laminate.
Both the resin impregnated decorative paper and the resin
impregnated kraft core paper are passed through ovens to increase
the molecular weight of the resin component, and reduce the
volatile level in the sheet (B-staging). After B-staging, a
decorative sheet is laid up with several layers of the kraft core
paper and loaded into a press. The press is brought up to pressure,
typically 1000 psi, and then heated up to temperatures typically
ranging from about 120.degree. C. to 160.degree. C. for 20 to 60
minutes. This is done to consolidate the multiple paper layers and
cure the resin components. At the end of that time period the press
is cooled and finally the pressure is released.
17. Some laminates are produced whose primary use is for flat
surfaces. Other laminates are produced that are post-formed
(thermoformed) into more complex shapes after the above pressing
process is complete. These laminates are used for counter tops
where the front edge is formed into a lip and the back edge is
formed up into a back-splash area. The postforming laminates are
usually under cured in the original pressing cycle or use a very
formable (soft) resin. If the laminates are fully cured or utilize
a stiffer more brittle resin, when they are postformed the
laminates will crack and break. This makes an unacceptable product
for consumers. Brittle laminates also tend to chip and break when
they are cut to size or machined prior to use or can be more
breakage prone during installation and use. This is also
unacceptable to the consumer.
18. Another problem in the laminating industry is the release of
volatile organic components into the atmosphere during the
B-staging process. One of these volatile organic components is
phenol. Typical levels of free phenol in the phenol-formaldehyde
resin used to impregnate the kraft core paper are in the 5-15%
range. One method to reduce the free phenol level in the base
phenol-formaldehyde resin is to increase the amount of formaldehyde
(relative to the phenol) in the resin as manufactured.
Unfortunately this usually results in a more brittle resin that
when cured is unacceptable for manufacturing postforming
laminates.
Paper Saturating Resins
19. Saturating resins, without modifiers, for oil filter, overlay,
and for paint roller tube applications are typically low mole ratio
resins in the range of 0.8-1.7 F/P. The low mole ratio resins give
the treated paper more flexibility for pleating before curing. They
are base catalyzed resins and are usually high molecular weight
resins which are water insoluble. A distillation step is required
and then the distilled resin is solvated in an alcohol--such as
methanol, isopropanol, or ethyl alcohol. The resin is usually
neutralized to a pH of 6.5-7.5 with acid to give lighter color
cure. The resin is then applied to base paper, usually in dip
roller pans, and then the treated paper goes into an oven to drive
off the solvent, resulting in "B" staged paper. This paper is then
rolled and shipped to the oil filter manufacturers. They then pleat
and cut the paper and then it is cured in an oven. The cured paper
will then have oil, temperature, water, and chemical resistant
properties. Saturating resins for plywood overlays work in a
similar way, except the treated paper is not pleated but is bonded
onto plywood or other substrate with heat and pressure, which cures
the resin.
20. There are some high mole ratio saturating resins, typically in
the range 1.8-2.5 F/P which are water soluble. These, however, must
be modified with a plasticizer such as a thermoplastic latex to
give the treated paper pleatability. The high mole ratio resins
alone will be too high in cross link density and therefore brittle
when cured. The advantage in waterborne resins are no emissions
from solvent and due to higher F/P mole ratios there will be less
emissions of free phenol.
Other Uses
21. Phenol-formaldehyde foam resins are used to make open or closed
cell foams when cured. Such foams are primarily used to make floral
foam supports for supporting flower stems in water. The foam is
able to soak up water many times it's weight to provide water for
the flowers. Such foams are primarily open cell foams with
perforations in cell walls. Other uses for phenol-formaldehyde
foams are dense foams used for models similar to balsa wood, foam
to hold jewelry, foam used to make molds for foot prosthetics and
closed cell foam for barrier and insulation type properties.
22. Other uses of phenol-formaldehyde resins include abrasive
binders, friction binders, and phenol-formaldehyde coated foundry
sand binders.
Melamine-Formaldehyde Resins
23. Melamine-formaldehyde resins provide binders that are clear.
Hence such resins are suitable for products such as ceiling tiles,
paper laminates (e.g., veneer for countertops), and molded
articles. However, currently there is a shortage of melamine
crystal used in manufacturing the melamine-formaldehyde resins. In
addition, melamine crystals are expensive.
24. Acoustic ceiling tiles are presently back-coated with melamine
resins in order to make them more rigid and humidity-resistant when
installed in suspended ceilings. Melamine resins are also used for
the preparation of decorative or overlay paper laminates due to
their excellent color, hardness, and solvent, water, chemical
resistance, heat resistance and humidity-resistance.
25. Molded articles, such as dinnerware, are presently prepared
with a combination of melamine-formaldehyde resins and
urea-formaldehyde resins. The resins are combined because the
melamine-formaldehyde resin is too expensive to use by itself.
However, such articles are generally not very water-resistant or
dimensionally stable.
26. It would be beneficial to provide an extender for both
phenol-formaldehyde resins and melamine-formaldehyde resins in
order to reduce formaldehyde emissions, phenolic emissions, improve
properties of the products obtained with the resins, and to reduce
overall cost of the resins.
SUMMARY OF THE INVENTION
27. The present invention is directed to the discovery that cyclic
urea prepolymers may be used as modifiers of thermosetting
phenol-formaldehyde and melamine-formaldehyde based resins for a
variety of end uses. The cyclic urea prepolymers are
urea-formaldehyde polymers containing at least 20% triazone and
substituted triazone compounds. The use of cyclic urea prepolymer
in such resin binders provides properties superior to the
properties of using the resin alone in many applications. The
resins are modified with the cyclic urea prepolymer, either by
reacting into the base resin system, blending with the completed
base resin system, or blending into a binder preparation.
28. The amount of cyclic urea prepolymer added to the resin is
dependent on the application. When blending the cyclic urea
prepolymer into a binder system, several modifier levels are
possible. The present invention, when used as described, results
in, for example, significantly lower phenol and phenolic emissions
over phenol-formaldehyde resin systems. The present invention when
used to modify melamine-formaldehyde resins was found to impart
superior stability over the non-modified resins. The present
invention, when used as described, results in, for example,
significantly lower stack opacity and better thermal stability over
traditional binders using urea or urea/ammonia as resin
extenders.
29. The present invention is particularly directed to the use of a
binder or adhesive comprising a phenol-formaldehyde or
melamine-formaldehyde resin modified with 1 to 95 wt % based on
resin solids of a cyclic urea prepolymer either during manufacture
of the resin or post added to the resin wherein the cyclic urea
prepolymer has a mole ratio of urea:formaldehyde:ammonia or a
primary amine of about 0.1 to 1.0:0.1 to 3.0:0.1 to 1.0.
30. The present invention is particularly directed to the use of
the binder in a variety of products including consolidated wood
products such as plywood, engineered lumber such as laminated
veneer lumber, hard board, fiber board, oriented strand board, and
other products such as insulation, laminates, abrasive coatings,
friction binders, foams, foundry binders, and petroleum recovery
binders. The present invention is further directed paper saturating
resins for oil filters, overlay, paint roller tubes and the like.
The binders of the present invention are further used to prepare
products such as ceiling tiles, paper laminates (e.g., veneer for
countertops), and molded articles.
DETAILED DESCRIPTION OF THE INVENTION
The Cyclic Urea Prepolymer
31. The present invention is based on the discovery that a cyclic
urea prepolymer, formed by a reaction of urea, formaldehyde, and
ammonia or a primary amine, is useful as a modifier in
phenol-formaldehyde resins and melamine-formaldehyde resins. The
present invention can be used to further modify a resin system
either by reacting into the base resin system, blending with the
completed base resin system, or blending into a binder
preparation.
32. The resins may then be used in binder compositions which
comprise a variety of liquid forms, including solutions, miscible
liquids, or dispersions and the like and combinations of such
liquid forms depending upon the optional ingredients blended into
the binder composition. Where the term solution or any of the
variations thereof is used herein it is intended to include any
relatively stable liquid phase.
Preparation of the Cyclic Urea Prepolymer
33. The cyclic urea prepolymer may be prepared by any suitable
method. For example, urea, formaldehyde, and ammonia or primary
amine are mixed and heated to the desired temperature for a set
period of time to form a cyclic urea prepolymer. Preferably the
mole ratio of reactants for the cyclic urea prepolymer are as
follows:
1 Formaldehyde: About 0.1 to 3.0 Ammonia or Primary Amine: About
0.1 to 1.0 Urea: About 0.1 to 1.0
34. Any combination of the above mole ratios is contemplated;
however, preferably the mole ratio of Urea:Formaldehyde:Ammonia or
Primary Amine is about 2.0:2.0:1.0 to 1.0:4.0:1.0 and more
preferably about 2.0:4.0:1.0 depending on the application. It is
contemplated that "ammonia or primary amine" also encompasses the
use of both ammonia and a primary amine or more than one primary
amine.
35. Processes of making cyclic urea prepolymers are recognized in
the art. In a preferred embodiment, the cyclic urea prepolymer may
be prepared by charging a reaction vessel with formaldehyde,
ammonia, and urea while maintaining the temperature below about
70.degree. C., preferably about 60.degree. C. The order of addition
is not critical, but it is important to take care during the
addition of ammonia to formaldehyde (or formaldehyde to ammonia),
due to the exothermic reaction. In fact, due to the strong
exotherm, it may be preferred to charge the formaldehyde and the
urea first, followed by the ammonia. This sequence of addition
allows one to take advantage of the endotherm caused by the
addition of urea to water to increase the rate of ammonia addition.
A base may be required to maintain an a~line condition throughout
the cook.
36. Once all the reactants are in the reaction vessel, the
resulting solution is heated at an alkaline pH to between about 60
and 105.degree. C., preferably about 85 to 95.degree. C., for 30
minutes to 3 hours, depending on mole ratio and temperature, or
until the reaction is complete. Once the reaction is complete, the
solution is cooled to room temperature for storage. The resulting
solution is storage stable for several months at ambient
conditions. The pH is between 5 and 11.
37. The yield is usually about 100%. The cyclic urea prepolymers
contain at least 20% triazone and substituted triazone compounds.
The ratio of cyclic ureas to di- and tri- substituted ureas and
mono-substituted ureas varies with the mole ratio of the reactants.
For example, a cyclic urea prepolymer having the mole ratio of
1.0:2.0:0.5 U:F:A resulted in a solution characterized by
C.sup.13-NMR and containing approximately 42.1% cyclic ureas, 28.5%
di/tri-substituted ureas, 24.5% mono-substituted ureas, and 4.9%
free urea. A cyclic urea prepolymer having the mole ratio of
1.0:1.2:0.5 U:F:A resulted in a solution characterized by
C.sup.13-NMR and containing approximately 25.7% cyclic ureas, 7.2%
di/tri-substituted ureas, 31.9% mono-substituted ureas, and 35.2
free urea.
38. In addition, the cyclic urea prepolymer may be prepared by a
method such as disclosed in U.S. Pat. No. 5,674,971, which is
hereby incorporated by reference in its entirety. The cyclic urea
prepolymer is prepared by reacting urea and formaldehyde in at
least a two step and optionally a three-step process. In the first
step, conducted under alkaline reaction conditions, urea and
formaldehyde are reacted in the presence of ammonia, at an F/U mole
ratio of between about 1.2:1 and 1.8:1. The ammonia is supplied in
an amount sufficient to yield an ammonia/urea mole ratio of between
about 0.05:1 and 1.2:1. The mixture is reacted to form a cyclic
triazone/triazine or cyclic urea prepolymer which forms the
building block for the ultimate resin.
39. Water soluble triazone compounds may also be prepared by
reacting urea, formaldehyde and a primary amine as described in
U.S. Pat. Nos. 2,641,584 and 4,778,510, each of which is
incorporated by reference in its entirety. These patents also
describe suitable primary amines such as, but are not limited to,
alkyl amines such as methyl amine, ethyl amine, and propyl amine,
lower hydroxyamines such as ethanolamine cycloalkylmonoamines such
as cyclopentylamine, ethylenediamine, hexamethylenediamine, and
linear polyamines. The primary amine may be substituted or
unsubstituted.
40. Skilled practitioners recognize that the reactants are
commercially available in many forms. Any form which can react with
the other reactants and which does not introduce extraneous
moieties deleterious to the desired reaction and reaction product
can be used in the preparation of the urea-formaldehyde resin of
the invention.
41. Formaldehyde is available in many forms. Paraform (solid,
polymerized formaldehyde) and formalin solutions (aqueous solutions
of formaldehyde, sometimes with methanol, in 37%, 44%, or 50%
formaldehyde concentrations) are commonly used forms. Formaldehyde
also is available as a gas. Any of these forms is suitable for use
in the practice of the invention. Typically, formalin solutions are
preferred as the formaldehyde source.
42. Similarly, urea is available in many forms. Solid urea, such as
prill, and urea solutions, typically aqueous solutions, are
commonly available. Further, urea may be combined with another
moiety, most typically formaldehyde and urea-formaldehyde, often in
aqueous solution. Any form of urea or urea in combination with
formaldehyde is suitable for use in the practice of the invention.
Both urea prill and combined urea-formaldehyde products are
preferred, such as Urea Formaldehyde Concentrate or UFC 85. These
types of products are disclosed in, for example, U.S. Pat. Nos.
5,362,842 and 5,389,716.
43. Skilled practitioners also recognize that ammonia is available
in various gaseous and liquid forms, particularly including aqueous
solutions at various concentrations. Any of these forms is suitable
for use. However, commercially-available aqueous ammonia-containing
solutions are preferred herein. Such solutions typically contain
between about 10 and 35% ammonia. A solution having 35% ammonia can
be used providing stability and control problems can be overcome.
An aqueous solution containing about 28% ammonia is particularly
preferred. Anhydrous ammonia may also be used.
44. Ammonia and/or late additions of urea are commonly used prior
art techniques to reduce free formaldehyde levels in
urea-formaldehyde polymer systems. The former technique suffers
from reducing the cured polymers resistance to hydrolysis. The
latter technique suffers from a tendency to produce a polymer
system that releases smoke during the cure cycle. This invention
reduces or eliminates both of these problems, yet still
significantly reduces free formaldehyde levels during cure and in
the cured product.
45. The reactants may also include a small amount of a resin
modifier such as ethylenediamine (EDA). Additional modifiers, such
as melamine, ethylene ureas, and primary, secondary and tertiary
amines, for example, dicyanodiamide can also be incorporated into
the resin of the invention. Concentrations of these modifiers in
the reaction mixture may vary from 0.05 to 5.00%. These types of
modifiers promote hydrolysis resistance, polymer flexibility and
lower formaldehyde emissions.
46. The cyclic urea prepolymer is then used as a modifier of the
resin. The modifier level using the cyclic urea prepolymer,
reported as a percent of binder solids, is preferably from 1% to
95%, but greater amounts are also contemplated. Binder solids refer
to the percent phenol-formaldehyde resin solids plus the percent
modifier solids. Thus, typically the resin and cyclic urea
prepolymer are combined to obtain 5 to 99 wt % resin solids and 1
to 95 wt % cyclic urea prepolymer solids. Preferred ranges are
dependent on the application.
Phenol-Formaldehyde Resins
47. The phenol-formaldehyde resole may be prepared by any suitable
manner. For example, the phenol-formaldehyde resin may be prepared
by reacting a molar excess of formaldehyde with phenol under
alkaline reaction conditions. Formaldehyde is used in an amount of
between about 0.5 and 4.5 moles per mole of phenol, with preferred
ranges dependent on the application. The % free formaldehyde is
typically between 0.1% and 15%. And the % free phenol is typically
between 0.1% and 20%. Preferred ranges depend on the
application.
48. Alkaline reaction conditions are established by adding an
alkaline catalyst to an aqueous solution of the phenol and
formaldehyde reactants. During the initial reaction of the phenol
and formaldehyde, only that amount of alkaline catalyst necessary
to produce a resin need be added to the reaction mixture. Suitable
amounts of alkaline catalyst are known to those skilled in the art.
Typically, at least about 0.005 mol of alkaline catalyst per mol of
phenol is used, with an amount between about 0.01 and 1 mol per mol
depending on the application. All the catalyst can be added
initially to the reactants or the catalyst can be added
incrementally in two or more additions or continuously over a
defined time period.
49. Alkaline catalysts normally used for preparing
phenol-formaldehyde resins also can be used in accordance with the
present invention. Typical alkaline catalysts include alkali metal
and alkali earth hydroxides such as lime, lithium hydroxide, sodium
hydroxide and potassium hydroxide; alkali metal carbonates such as
sodium carbonate and potassium carbonate; and amines. Based on
considerations of cost and availability, sodium hydroxide is used
most often.
50. The cyclic prepolymer may be reacted into the
phenol-formaldehyde resin or added as a post blend depending upon
the needs of the resin. The preferred method is dependent on the
application. For example, the cyclic urea prepolymer is blended
with the prepared phenol-formaldehyde resin to produce a binder
suitable for insulation.
51. It may be preferable to react the cyclic urea prepolymer with
formaldehyde before attempting to react the material with phenol to
tie it into the overall polymer structure. Typically cyclic urea
prepolymer is reacted with formaldehyde (50%) at a ratio of about 4
to 1, preferably about 2:1 by adding the two together in a suitable
container, adjusting the pH to about 8.5 to 10.0, preferably about
9.0 to 9.5 and heating to 80 to 100.degree. C., preferably about 90
to 95.degree. C. The mire is reacted under these conditions for
about two hours. This product is then added to the front of the
phenol-formaldehyde resin with half of the formaldehyde that was
added taken out from the resins formaldehyde charge. The resin is
normalized and used for its application.
52. The reaction with phenol is achieved by adding the
pre-methylolated cyclic urea prepolymer to all the phenol normally
used to make the base resin and adding NaOH (50%) to bring the pH
to about 9.5 to 11.5, preferably about 10.5. The mixture is heated
to about 80 to 100.degree. C., preferably about 90-95.degree. C.
for about one hour or longer depending upon the pH. The product of
this step is a phenol-cyclic urea prepolymer reaction product that
can be used to make the base resin.
53. Concentration of raw materials is not critical. Water can be
added, or removed by distillation, to adjust the % non-volatiles to
the desired level.
54. The resin and cyclic urea prepolymer are combined to obtain 1
to 95 wt % cyclic urea prepolymer solids, preferably 10 to 70 wt %.
Preferred ranges are dependent on the application.
Insulation
55. A phenol-formaldehyde resin can be used as described above
preferably with an amount of formaldehyde between about 2.0 and
4.5, more preferably between about 2.5 and 4.5, moles per mole of
phenol. The % free formaldehyde is typically between about 4% and
15%. And the % free phenol-formaldehyde typically between about
0.1% and 2%. Typically, at least about 0.05 mol of alkaline
catalyst per mol of phenol is used, more typically, between about
0.1 and 0.3 mol per mol of phenol.
56. The cyclic urea prepolymer is combined with the
phenol-formaldehyde resin composition and optionally, a suitable
latent catalyst. When an acid cure is desirable, a latent catalyst
is added to the phenol-formaldehyde resin composition in an amount
effective to neutralize the alkalinity of the base resin and lower
the pH to give an acid cure. Typical amounts are at least about 2
wt %, preferably about 4 to 10 wt %, based on the weight of binder
solids. Suitable latent catalysts include ammonium sulfate and
similar latent acid catalysts as known in the art. In addition, the
binder may contain suitable coupling agents.
57. The phenol-formaldehyde resin based binder for use in
insulation, such as fiberglass or mineral wool insulation, may be
prepared by combining and mixing the phenol-formaldehyde resin with
the desired formaldehyde scavenger and premixing until free
formaldehyde approaches 0%. The premix time will be dependent on
the scavenger used. For example, if ammonia is used, the premix
time will be on the order of minutes whereas if urea is used, the
premix time will be from 8 to 16 hours, depending on temperature.
The remaining binder ingredients including, cyclic urea prepolymer,
latent acid catalyst, coupling agents, dedusting oils, and desired
dilution water, can then be added to the premixed resin.
58. The resin and cyclic urea prepolymer are combined to obtain 1
to 95 wt % cyclic urea prepolymer solids, preferably 10 to 70 wt %,
more preferably 20 to 60 wt %.
59. The binder can be used immediately and may be diluted with
water to a concentration suitable for the desired method of
application, such as by spraying onto the glass fibers. Binders
used for preparing insulation are generally very dilute, requiring
water dilutability greater than 50:1. Both the present invention
and the binders made from the present invention have the necessary
water dilutability characteristics. Other conventional binder
additives compatible with the resin composition and silane coupling
agent may be added to the binder.
60. Any suitable method may be used to form the fibers for use in
preparing insulation. For example, for glass fibers, use can be
made of discontinuous or staple glass fibers such as are formed by
the rapid attenuation of multiple streams of molten glass by high
pressure streams of air or steam directed angular downwardly onto
the streams of molten glass flowing there between. Use can be made
of continuous or textile fibers such as are formed by the rapid
attenuation of molten streams of glass. Continuous glass fibers may
be employed in the form of mats fabricated by swirling the endless
filaments or strands of continuous fibers, or they may be chopped
or cut to shorter lengths for mat or batt formation. Use can also
be made of ultra-fine fibers formed by the attenuation of glass
rods. Also, such fibers may be treated with a size, anchoring agent
or other modifying agent before use.
61. The binder can be applied to the fibers by flooding the
collected mat of fibers and draining off the excess, by applying
the binder composition onto the fibers during mat formation, by
spraying the glass fiber mat or the like. The layer of fiber with
binder is then compressed and shaped into the form and dimensions
of the desired insulating product such as pipe, batt or board and
passed through a curing oven where the binder is cured, thus fixing
the size and shape of the finished insulation product by bonding
the mass of fibers one to another and forming an integral composite
structure. For cure, the mass is heated to a temperature in excess
of 175.degree. C. and preferably within the range of 205 to
345.degree. C. for a time sufficient to cure the components. The
fiber component will represent the principal material of the
insulation product. Usually 99-60% by weight of the product will be
composed of fibers while the amount of binder will be in reverse
proportion ranging from 1-40%, depending upon the density and
character of the product.
62. Glass insulations having a density less than one pound per
cubic foot may be formed with binders present in the lower range of
concentrations while molded or compressed products having a density
as high as 30-40 pounds per cubic foot can be fabricated of systems
embodying the binder composition in the higher proportion of the
described range.
63. Fiber insulation can be formed as a relatively thin product of
about 0.25 to 1.5 inch or it can be a thick mat of 12 to 14 inches
or more. The time and temperature for cure will depend in part on
the amount of binder in the final structure and the thickness and
density of the structure that is formed. For a structure having a
thickness ranging from 0.25 to 1.5 inch, a cure time ranging from
1-5 minutes will be sufficient at a cure temperature within the
range of 400-600 F.
64. The desired product properties obtained from traditional
extenders and formaldehyde scavengers are maintained (i.e., color,
tensile strength, moisture resistance, moisture absorption,
recovery, etc.). In addition, these desired properties are
maintained at lower phenolic solids levels than could be achieved
with prior art. Further, the ability to go to lower phenolic solids
levels results in reduced phenolic emissions and lower forming hood
emissions. The present invention also lends improved anti-punk
properties to the finished insulation product, and when used with
ammonia or another rapid formaldehyde scavenger, eliminates
pre-react time. Elimination of pre-react time results in increased
binder stability. Improved anti-punk is desirable in products
requiring greater thermal stability, for example pipe
insulation.
Consolidated Wood Products
65. The binders of the present invention can be used in
consolidated wood products such as plywood, engineered lumber,
oriented strand board, particle board, and the like. In this field,
typically the term adhesive is used instead of binder. Thus, when
referring to consolidated wood products, the term adhesive shall be
used.
Plywood and Engineered Lumber
66. Typically the cyclic urea prepolymer is either cooked into the
plywood resin or added to a plywood resin to provide good bonding
performance of the adhesive (binder). The phenol-formaldehyde resin
is prepared having a mole ratio of about 1.8 to 2.4 moles
formaldehyde per mole phenol and an alkaline catalyst level of
about 0.5 to 1.0 moles catalyst per mole phenol. Typically the
amount of cyclic urea prepolymer solids by weight in the adhesive
based upon the total resin solids by weight is between about 1 and
40, preferably between 1 and 20%.
67. Methylolated cyclic urea pre-polymer is typically prepared by
reacting urea, ammonia and formaldehyde and then reacting with two
moles of formaldehyde to produce the methylolated cyclic urea
pre-polymer having a 50% solids. This cyclic urea prepolymer is
then reacted into a standard phenol-formaldehyde resin during the
cook cycle of the phenol-formaldehyde resin. Phenol is combined
with formaldehyde, water, cyclic urea prepolymer, and caustic. The
mixture is heated and allowed to exotherm. Then additional caustic
and then additional formaldehyde is added. The mixture is heated,
allowed to exotherm, and held to a desired endpoint.
68. Adhesive mixtures typically contain water, extenders, fillers,
caustic, performance additives, and phenol-formaldehyde resin.
Typical fillers and extenders include: corn, wheat, soya, and other
cereal flours and derivatives, finely ground nut shells, barks, and
agricultural furfural waste residues. The adhesive mixtures are
then applied to plywood veneers and the veneers are then combined
in plies of three or more using a hot press to acre and bond the
adhesive. Methods of applying adhesive to plywood and pressing are
well known in the art.
Oriented Strand Board
69. Is known that dimethylol urea is not a stable compound in that
in the presence of another formaldehyde reactive compound the
dimethylol urea will donate its two formaldehyde groups to the more
stable phenol, ammonia, melamine etc. This leaves raw urea in the
resin which reduces the durability of the OSB or waferboard very
significantly. It was discovered that cyclic urea prepolymer is
much more stable and the use of the cyclic prepolymer provides
improved durability over resins extended with urea.
70. The cyclic urea prepolymer can be used at levels as high as 10%
without significant impact on the performance of the product when
cooked into the resin and/or used as a formaldehyde scavenger to
prevent formaldehyde emissions. Spray dried resins cannot be
properly spray dried if the free urea content is higher than 1 to
2% while the copolymer of cyclic urea, formaldehyde and phenol can
be spray dried up to and including 50%.
Paper Saturating Resin
71. Cyclic urea prepolymer can also be added to saturating type
phenol-formaldehyde resins. Saturating resins are used to saturate
paper for oil filters, overlay paper, and paint roller tube
applications. The cyclic urea prepolymer acts as a plasticizer
"softening" the cure of the phenol-formaldehyde resin. Benefits of
using the cyclic urea prepolymer include improving the flexibility
of oil filters allowing easier "pleatability," i.e., formation of
the paper pleats in the oil filter. Also the paper in the filter
cartridge could withstand greater stresses allowing longer life. In
the overlay paper and paint roller the applications a "softer" cure
allows easier machinability, i.e., less chipping and breaking
during handling, cutting and sawing. In air filter paper the high
level of nitrogen from the cyclic urea prepolymer will reduce the
flammability of the filter paper. In all of these saturating
applications, lower free phenol resins result.
72. By diluting the phenol-formaldehyde resin with cyclic urea
prepolymer, free phenol and other volatile phenolic moiety levels
are reduced which reduces air pollution. Because of the
plasticizing effect achieved with the cyclic urea prepolymer,
higher F:P mole ratio phenol-formaldehyde resins (traditionally
more brittle) can be used which further reduces the free phenol and
volatile phenolic moiety levels.
73. Water soluble saturating resins are typically in the range of
1.8 to 2.5 moles formaldehyde per mole phenol. Due to the high mole
ratio and increased cross-link density, these resins typically are
modified with a plasticizer such as latex to give treated paper
pleatability. Water borne resins have the advantage of reduced
emissions due to lower % free phenol and reduced volatile organics.
The plasticizing effect achieved with the cyclic urea prepolymer
provides greater flexibility in the above phenolic resins. The
cyclic urea prepolymer can be cooked into the base resin or post
added.
High Pressure Laminating Resins
74. Cyclic urea prepolymer in laminating type phenol-formaldehyde
resins acts as a plasticizer "softening" the cure of the resin.
This makes the laminate more post-formable and tougher. Products
produced with such resins resist chipping and breakage during
machining steps. Diluting the phenol-formaldehyde resin with cyclic
urea prepolymer reduces the free phenol and other volatile phenolic
moiety levels of the phenol-formaldehyde resin which reduces air
pollution. Because of the plasticizing effect achieved with the
cyclic urea prepolymer, higher F:P mole ratio PF resins
(traditionally more brittle) can be used which further reduces the
free phenol and volatile phenolic moiety levels.
75. Phenol-formaldehyde resins of the present invention used for
the manufacture of high pressure laminates generally contain F:P
mole ratios of 1.2 to 3.5, preferably 1.4 to 2.5. Generally, 1 to
50 parts, preferably 5 to 40, of cyclic urea prepolymer are added
per 99 to 50 parts of phenol-formaldehyde resin (total adds up to
100 parts). Lower levels of cyclic urea prepolymer generally
perform better with lower F:P phenol-formaldehyde resins whereas
higher levels perform better with higher F:P phenol-formaldehyde
resins.
76. Any phenol-formaldehyde catalyst may be used such as, but not
limited to sodium hydroxide. Generally catalysts are added in
amounts from about 0.2 wt % to about 6, preferably, about 0.5 to
3.
77. The pH of the phenol-formaldehyde resin is typically from about
3.5 to about 8.9, preferably from about 6.5 to 8.5. Lower pHs can
help reduce the degree of resin cure and reduce laminate
brittleness but too low pHs can increase the degree of cure of the
melamine resin impregnated surface sheet at the interface.
78. Methanol may be added, as necessary, to maintain solubility of
the phenol-formaldehyde resin. Alternatively, water borne
phenol-formaldehyde resins may also be used. Generally water borne
laminating resins are similar to the solvent borne resin except for
the lack of an organic solvent and that they are usually lower in
molecular weight than their solvent borne counterparts. This is
primarily to achieve an acceptable degree of penetration into the
kraft paper core sheet. Because they are lower in molecular weight;
they typically have a higher level of free phenol. The practice of
this invention with water borne phenol-formaldehyde resins can
significantly reduce their free phenol levels. For the solvent
borne resins, the percentage of methanol or other organic solvent
can range up to about 25% but could go higher without interfering
with the utility of this invention. The water content may be up to
30+%. Solids (non-volatile) contents should range from about 50% up
to 75+%. Viscosities can range from less than 100 cps to over 1000
cps.
Other Phenol-Formaldehyde Resin Applications
79. Other uses for the cyclic urea prepolymer include addition to
abrasives coating resins as a formaldehyde scavenger and/or
modifier. Any phenol-formaldehyde resin used as an abrasive or
friction binder may be modified. The phenol-formaldehyde resin is
heated to about 40 to 70.degree. C., preferably about 55.degree. C.
Cyclic urea prepolymer is added to the resin in an amount of 1 to
20 parts per 100 parts of resin.
80. The cyclic urea prepolymer may be used in phenol-formaldehyde
foams prepared in any manner known in the art. The
phenol-formaldehyde foams typically range from about 1.7 to 3.0
moles formaldehyde per mole phenol. Urea is typically added to
scavenge formaldehyde in these resins. The cyclic urea prepolymer
can be prepared to scavenge formaldehyde or it can be added to
further modify the base phenol-formaldehyde resin.
81. Generally phenol and formaldehyde are reacted with a base
catalyst to form the base resin. The resin is then neutralized to a
pH between about 4 and 8 with an acid. Water is then distilled from
the resin to a low water content, approximately 5 to 10%. The resin
typically has a high viscosity of about 2,000 to 20,000 cps. The
cyclic urea prepolymer may be reacted into the phenol-formaldehyde
resin or post added to replace 5% to 70% of the phenolic
solids.
82. In order to foam the resin, surfactants and/or wetting agents
are mixed into the resin to create bubbles within the resin. Then a
low boiling liquid such as CFC, HCFC, pentane or hexane is added to
the mixture. A strong acid is added to the resin to initiate curing
of the phenol-formaldehyde resin. This reaction generates heat
causing the low boiling liquid to vaporize within the bubbles in
the resin. As a result a foam is created from this mixture. Within
about 10 minutes the foam rises to its maximum height and hardens
when fully cured.
83. The cyclic urea prepolymer may also be used as a crosslinker in
novolac resins. The cyclic urea prepolymer may be used as a partial
or complete replacement of the hexamine cross linker typically used
in the coating of these novolac resins. The cost of the prepolymer
is less than the cost of commercially available hexamine and its
use will allow for a potential cost reduction to the user.
84. In the manufacturing of low nitrogen containing foundry sands,
the hexamine cross linker is replaced in part with another cross
linking agent that does not contain nitrogen. Nitrogen when present
in coated foundry sand can give rise to nitrogen defects during
steel casing. It is advantageous to have as low nitrogen content as
possible. Usually this other cross linking agent is a thermosetting
resole phenol-formaldehyde resin. During the manufacturing of these
low nitrogen containing sands, the novolac resin is added, followed
by the resole resin and then the hexamine. The reaction product
between the cyclic urea prepolymer and a phenol-formaldehyde resole
produces a resin that may be utilized as a cross linking agent.
This hybrid when used in place of the hexamine in the coating on
sand with the novolac produces a thermally curable sand that has a
lower nitrogen content than if the sand was produced with hexamine
alone. Furthermore, the sand coater does not have to handle two
separate components, which are the resole resin and the
hexamine.
85. When reacted with resole components, a hybrid crosslinking
compound is prepared that may also be used to thermally cure
novolac coated foundry sand. This hybrid has the advantage of
having a lower nitrogen percentage than using hexamine for the same
given percentage added.
Sand Coating
86. Phenol-formaldehyde resins for use as binders for foundry sand
including both resoles and novolacs. The resoles, mentioned
previously have molar ratios of formaldehyde to phenol of greater
than 1.0 and are reacted under alkaline conditions. Such resins are
thermosetting in nature and may be used alone or in conjunction
with phenol-formaldehyde novolacs and additional cross linkers.
87. Novolac resins have molar ratios of formaldehyde to phenol of
less than 1 with preferred values between about 0.5 to 0.9. The
reaction between phenol and formaldehyde is carried out below a 6
pH with less than about 3 pH being preferred. The add catalyst
level may range from about 0.1 to 3 wt % with 1 to 2 wt %
preferred. Acids include, but are not limited to: sulfuric acid,
hydrochloric acid, oxalic acid, sulfamic acid.
88. Following the reaction between the formaldehyde and phenol, the
mixture may be neutralized if so required prior to dehydration. The
pH may be raised to 7 pH with about 3 to 5 being preferred. Bases
that may be used include, but are not limited to: alkali hydroxides
and basic amines. After the reaction and neutralization, the excess
water and residual free phenol monomer may be removed either by
atmospheric or vacuum distillation.
89. Following the dehydration and while the resin solution is
molten, additives such as wax or thermoplastic modifiers may be
added. The resin solution may be cooled and chipped or flaked into
pieces or may be dissolved into a suitable solvent.
90. The novolac resin so produced is thermoplastic in nature. To
produce a thermosetting coating on sand, during the coating of the
novolac by the sand coater, an additional cross liking agent is
added. Generally the agent used is hexamine
(hexamethylenetetramine). The hexamine is added between about 5 wt
% and 20 wt % (based on the resin solids on the sand) with about 8
wt % to 12 wt % being preferred.
Melamine-Formaldehyde Resins
91. The melamine-formaldehyde resin is prepared as known in the art
with the exception that part of the melamine crystal is replaced
with the urea prepolymer. The melamine-formaldehyde resin is
generally produced with a formaldehyde to melamine molar ratio in
the range of about0.5:1 to 6:1, preferably in the range of about
1.5:1 to 3.0:1. For example, melamine is reacted with formaldehyde
under alkaline conditions in the presence of an effective amount of
a catalyst and cyclic urea prepolymer. The resin and cyclic urea
prepolymer are generally combined to obtain about 40 to 70 wt %,
typically 60 wt %, melamine resin solids and 1 to 25 wt % cyclic
urea prepolymer solids.
92. As used herein, the phrase "under alkaline conditions" with
reference to the reaction mixture means a pH of between about 7 and
11, preferably between about 8.5 and 10.5 and, more preferably,
between about 9.0 and 9.5. The alkaline condition for synthesizing
the modified melamine-formaldehyde resin may be achieved simply by
adding a base to an aqueous mixture to obtain the desired pH.
Suitable bases include, but are not limited to, alkali metal
hydroxides, such as sodium, lithium, or potassium hydroxide. Other
bases include alkali metal carbonates, such as sodium carbonate and
potassium carbonate, alkaline earth hydroxides, such as magnesium
hydroxide, calcium hydroxide and barium hydroxide, aqueous ammonia,
and amines, such as triethanolamine. Preferably caustic soda
(sodium hydroxide) is used.
93. Although melamine is specifically mentioned for use in the
practice of this invention, and is generally preferred, the
melamine may be partially or totally replaced with other suitable
amine-containing compounds. Other suitable compounds include urea,
thiourea, dicyandiamide, melem, melam, melon, ammeline, ammelide,
substituted melamines, guanamines, or mixtures thereof. Substituted
melamines include the alkyl melamines and aryl melamines which can
be mono-, di- or tri-substituted. In the alkyl-substituted
melamines, each alkyl group can contain from 1 to 6 carbons,
preferably from 1 to 4 carbons. Representative examples of some
alkyl-substituted melamines are monomethylmelamine, dimethyl
melamine, trimethyl melamine, monoethyl melamine, and
1-methyl-3-propyl-5-butyl melamine. In the aryl-substituted
melamines, each aryl group can contain 1-2 phenyl moieties and,
preferably, 1 phenyl moiety. Typical examples of an
aryl-substituted melamine are monophenyl melamine or diphenyl
melamine. Based on considerations of cost and availability,
standard melamine is generally preferred.
Ceiling Tiles
94. Acoustical ceiling tiles of the lay-in type are large regular
interfelted cellulose or mineral fiber materials with a starch
binder. They are typically 48.times.24.times.1/2 inches and are
perforated on the face side for absorption of sound. They are laid
in hangers suspended from ceilings and are only supported by their
edges. An anti-sag coating of heat-cured thermosetting resin such
as melamine-formaldehyde resin is applied on the back side to
prevent sag which tends to occur under conditions of high
temperature and humidity. The coating acts as a skin to hold the
center of the tile in tension and provides the necessary support to
keep the suspended tile flat.
95. The melamine-formaldehyde extended resin may be combined with
clay to form a coating which is applied to the ceiling tiles.
Typical, but not limiting, resin-clay coating mixes are prepared
with 4 parts clay and 1 part resin in a 55% solids aqueous mixture.
The mixes are then catalyzed with the appropriate amount of a
suitable catalyst such as ammonium sulfate to yield catalyzed
resin-clay slurries.
96. The cyclic urea prepolymer provides a partial replacement for
melamine crystal in the manufacture of melamine-formaldehyde resins
which are used as coatings for sag resistant ceiling tiles. Cyclic
urea prepolymers are more readily available than the melamine
crystal. It can be post-added or reacted into the melamine resin
while maintaining the sag resistance as measured by tensile modulus
of the cured resin. Also retained is the heat and moisture
resistance of the melamine-formaldehyde resin.
Overlay Paper Laminates
97. A melamine formaldehyde resin is modified with 1-25% cyclic
urea prepolymer solids by cold addition or by reaction. The resin
contains resin solids of 50-60% and is storage stable for 4-6
weeks. Cured overlay paper treated with the cyclic urea modified
melamine-formaldehyde resins retain water and heat resistance.
Preferably, the melamine-formaldehyde resin has a F:M molar ratio
of 1-6.
98. Methods, techniques and equipment for preparation of decorative
laminates are well known to those skilled in the art, and need not
be described in detail In general, a generally porous substrate,
such as paper or a fabric web, is impregnated with a solution of
the modified melamine resin and dried (B-staged). The dried resin
impregnated substrate, along with other layers, is pressed usually
with heat to form a laminate. At this point, the laminate may be
only partially cured. Thereafter, the laminate may be post-formed
and cured completely.
99. A typical decorative laminate is prepared from (1) a rigid
substrate, (2) a melamine resin impregnated decorative substrate,
and, in some cases (3) a melamine resin impregnated overlay sheet.
In such decorative laminates, the rigid substrate may consist of
any suitable material, such as particle board, a resin-binded wood
fiberboard, a plurality of phenol-formaldehyde resin-impregnated
sheets, etc. These composites are heated under pressure to form a
single component which can be incorporated into furniture, used on
countertops or flooring, etc.
100. The amount of resin solids incorporated into these laminates
varies from 30% to 80% based on the weight of the total laminate,
and typically depends as understood by those skilled in the art on
the type of application and the type of materials used to make the
laminate. The lower percentages are generally used for decorative
substrates such as decorative print sheets and the higher amounts
are used in overlay sheets. After the substrate is impregnated with
the aqueous resin, it is dried to a suitable volatile content
(B-staged) and the substrates and sheets then are assembled into a
laminate between two pressing plates. A laminate is then formed in
this fashion under a specific pressure (generally 200-2000 psi
depending on process and/or product) and temperature (generally
120-175.degree. C.) for periods of 0.5 to 30 mutes. A laminate made
in this manner must then pass several physical tests, including
impact resistance, abrasion resistance, and resistance to boiling
water.
Molded Articles
101. Molded articles, such as dinnerware, may be prepared using
melamine resins modified with the cyclic urea prepolymer. The
cyclic urea allows replacement of the less readily available
melamine solids while maintaining water and heat resistance as well
as the dimensional stability of the molded articles. Molded
articles can be prepared from pulp, glass fibers, or fillers as
well known in the art.
102. A molding composition can be prepared by mixing alpha
cellulose pulp and the resin and then drying to an intermediate.
The intermediate is ground and then sent to storage. Prior to hot
molding the final article, the intermediate is ball milled together
with catalysts, colorants, UV stabilizer, and a mold lubricant. The
ground mixture is then assembled between printed sheets of paper
that are impregnated with the cyclic urea prepolymer modified
melamine-formaldehyde resin.
103. The following examples are for purposes of illustration and
are not intended to limit the scope of the claimed invention.
EXAMPLES
Example 1
104. Preparation of Cyclic Urea Prepolymer
105. a) A cyclic urea prepolymer having a mole ratio of
1.0:2.0:0.5, urea:formaldehyde:ammonia (U:F:A), was prepared by
charging a reaction vessel with formaldehyde, ammonia, and urea
while maintaining the temperature below about 65.degree. C. Once
all the reactants were in the reaction vessel, the resulting
solution was heated to about 90.degree. C., for about 1 hour until
the reaction is complete. Once the reaction was complete, the
solution was cooled to room temperature. C.sup.13-NMR indicated
approximately 42.1% of the urea was contained in the triazone ring
structure, 28.5% of the urea was di/ti-substituted, 24.5% of the
urea was mono-substituted, and 4.9% of the urea was free.
106. b) A second cyclic urea prepolymer was prepared in the same
manner as a) except for the mole ratio of 1.0:1.2:0.5. C.sup.13-NMR
indicated approximately 25.7% of the urea was contained in the
triazone ring structure, 7.2% of the urea was di/tri-substituted,
31.9% of the urea was mono-substituted, and 35.2% of the urea was
free.
107. c) A third cyclic urea prepolymer was prepared in the same
manner as a) except for the mole ratio of 1:3:1 and it was heated
to about 90.degree. C. for 1 hour and then 100.degree. C. for 2
hours. C.sup.13-NMR indicated approximately 76.0% of the urea was
contained in the triazone ring structure, 15.3% of the urea was
di/tri-substituted, 8.1% of the urea was mono-substituted, and 0.6%
of the urea was free.
108. d) A fourth cyclic urea prepolymer was prepared in the same
manner as a) except for the mole ratio of 1:4:1 and it was heated
to about 90.degree. C. for 3 hours and the pH was controlled around
7.5. C.sup.13-NMR indicated approximately 79.2% of the urea was
contained in the triazone ring structure, 17.7% of the urea was
di/tri-substituted, 1.6% of the urea was mono-substituted, and 1.5%
of the urea was free.
Example 2
109. Preparation of Phenol-Formaldehyde Binders Modified with
Cyclic Urea Prepolymer and Evaluation of the Binders for Fiberglass
Insulation Applications
110. The following phenol-formaldehyde binders were prepared.
111. 1) a pre-reacted system with a 26% urea extension and a
formaldehyde to ammonia mole ratio (F/A) of 1.14,
112. 2) non-pre-reacted system with a 26% urea extension and a
formaldehyde to ammonia mole ratio (F/A) of 1.14,
113. 3) a non-prereacted system using the 1.0:1.2:0.5 U:F:A system
of example 1b at a 26% fortification level and an F/A of 1.14,
114. 4) a non-prereacted system using the 1.0:2.0:0.5 U:F:A system
of example 1a at a 26% fortification level and an F/A of 1.14,
115. 5) a non-prereacted system using the 1.0:1.2:0.5 U:F:A system
of example 1a at a 50% fortification level and ammonia to result in
an F/A=1.14, and
116. 6) a non-prereacted system using the 1.0:2.0:0.5 U:F:A system
of example 1a at a 50% fortification level and ammonia to result in
an F/A 1.14.
117. The composition of the binders are summarized in Table 1.
2TABLE 1 Grams Grams Grams Grams Grams Grams Grams Binder Resin
Premix 40% urea Water 28% NH.sub.4OH 20% (NH.sub.4).sub.2SO.sub.4
UFA Resin 1 0 42.0 0 49.7 3.8 4.5 0 2 29.0 0 13.0 49.7 3.8 4.5 0 3
29.0 0 0 51.8 3.8 4.5 10.9 4 29.0 0 0 52.5 3.8 4.5 10.2 5 19.6 0 0
53.7 2.6 3.3 20.9 6 19.6 0 0 55.0 2.6 3.3 19.6
118. The resin had 7.4% free formaldehyde, 1.0% free phenol, a pH
of 8.4 and 51% solids.
119. The formaldehyde emissions of each binder was tested using the
tube furnace method. A premix was prepared by combining 145 g of
resin with 65 g of 40% urea. The premix solution was allowed to
prereact overnight (16 hours) at room temperature. The binders were
prepared as outlined in Table 1. The binder was weighed onto a
glass filter paper in a glass sample boat to the nearest 0.1 mg.
The sample boat was transferred to the tube furnace and cured at
200.degree. C. for 10 minutes. The air from the tube furnace was
sparged through a 1:1 solution of acetonitrile to water. The
solution was derivatized using dinitrophenylhydrazine and analyzed
on the HPLC using a diode array detector to quantify the
formaldehyde hydrazone as percent of binder solids.
120. Handsheets were prepared by sprinkling the binder onto a glass
mat, vacuuming the excess binder off the glass, and curing the
sheet in a forced air oven at 205.degree. C. for 1.5 minutes. Dry
tensiles were measured by breaking the handsheets in a tensile
tester. Hot/wet tensiles were measured by soaking the handsheets in
water at 85.degree. C. for 10 minutes and then breaking them in a
tensile tester while they were still hot and wet. The vent for the
oven was fitted with a pipe having a light meter attached. Opacity
or visible emissions were determined from either the %
transmittance or the % absorbance of light. The opacity and the
formaldehyde emissions results for all of the binders are displayed
in Table 2.
3TABLE 2 Opacity % For- Dry Tensile Hot/Wet (% Absorbance)
maldehyde Strength Tensile Binder Area/gram Emissions (psi)
Strength (psi) 1 0.356 1.55 94.6 62.7 2 0.998 1.08 81.3 52.9 3
0.453 0.95 93.1 60.9 4 0.394 0.96 94.9 61.5 5 0.471 0.73 85.5 62.2
6 0.147 0.74 95.5 52.2
Example 3
121. Preparation of Phenol-Formaldehyde Adhesives Modified with
Cyclic Urea Prepolymer and Use of the Adhesives in Plywood
122. Methylolated cyclic urea pre-polymer was prepared by reacting
urea, ammonia and formaldehyde as described earlier, and then
reacting further with two moles of formaldehyde per mole of the
urea, to produce the methylolated cyclic urea pre-polymer having a
50% solids level.
123. A) Resin A: The cyclic urea prepolymer was reacted with a
standard phenol-formaldehyde resin during the cook cycle of the
phenol-formaldehyde resin. Phenol (1311 g) was combined with 583 g
of formaldehyde (50%), 1217 g of water, 500 g of cyclic urea
prepolymer, 16 g of pearl starch, 1.5 g defoamer, and 158 g of
caustic (50%). The initial loading of phenol and formaldehyde was
adjusted to maintain a mole ratio of 0.8 F/P during the first cook
stage. The mixture was allowed to exotherm to 79-80.degree. C. with
heat. Additional caustic (142 g, 50%) was added and then 1033 g of
formaldehyde (50%) was added over 30 minutes. The mixture was
allowed to exotherm to 97-98.degree. C. with heat. The mixture was
held for 22 minutes before cooling to room temperature. The cyclic
urea prepolymer comprised 9.5 wt % of the final resin.
124. The viscosity of the final resin was 944 cps at 25.degree. C.,
solids content was 43.6 wt %, percent caustic was 5.9 wt %, gel
time was 25.7 minutes, refractive index of 1.4643 and molecular
weight was Mn=279 Mw=693 and Mz=1407. The polydispersity was
2.482.
125. A standard plywood resin was used as the control resin and had
a viscosity of 1146 cps, solids content of 44 wt %, percent caustic
of 5.9 wt %, gel time of 24 minutes, refractive index of 1.4646 and
molecular weight by GPC of Mu=318, Mw=948, and Mz=2322.
126. B) Six adhesive mixes were made. The control adhesive mix
contained 1) fresh water at 17.5 wt %, 2) Q-bond corn flour
extender at 6.6 wt %, 3) Co-Cob filler (furfural residue made from
waste agricultural sources) at 7.6 wt %, 4) soda ash at 0.3 wt %,
5) 50% caustic at 3.0 wt % and 6) phenol-formaldehyde resin at 65
wt %. Only the standard plywood resin formed part of the control
adhesive mix. The remaining mixes replaced all or part of the
standard plywood control resin with Resin A.
127. Mix #1 The standard plywood control resin.
128. Mix #2 50/50 wt ratio of the standard plywood control resin
and Resin A.
129. Mix #3 100% of Resin A.
130. Mix #4 Mixture of 38 g of Resin A and 743 g of the standard
plywood control resin.
131. Mix #5 Mixture of 75 g of Resin A and 706 g of the standard
plywood control resin.
132. Mix #6 Mixture of 154 g of Resin A and 635 g of the standard
plywood control resin.
133. After the adhesive mixes were made, the cyclic urea prepolymer
content in mixes 4, 5 and 6 was increased. Methylolated cyclic urea
pre-polymer (35 g) was added to mix 4, 67 g to mix 5 and 137 g to
nix 6. Modifications to the formulation were made for the addition
of cyclic urea prepolymer which was not cooked into the resin by
adjusting the solids contributed by the PF resin, filler and
extenders. Those changes are presented in the Table 3 in terms of
total dry solids, total resin solids and PF resin solids.
4TABLE 3 Mix # 1 2 3 4 5 6 Total Dry Solids, % 42.5 42.6 42.9 42.7
42.9 43.4 Total Resin Solids, % 28 28.2 28.4 28.7 29.2 30.5 Total
PF Resin Solids, % 28 26.7 25.3 27.1 26.3 24.9 Total Cyclic Urea
Solids, % 0 1.5 3.1 1.6 2.9 5.6 % Cyclic Urea Solids, 0 1.5 3.1 0.2
0.3 0.5 Cooked % Cyclic Urea Solids, Added 0 0 0 1.4 2.6 5.1 %
Cyclic Urea, 0 5.5 10.8 5.4 9.9 18.3 100% Resin Basis % Wood
Failure 64.5 78.8 70.1 83.3 83.5 53.5
134. The adhesive mixes were applied to southern pine veneers of
1/8 inch thickness and evaluated in three ply panels made on a hot
press. The veneers were stabilized to a 8% moisture content and
used as all the plies in a three ply plywood panel lay-up. The
adhesives were applied by a laboratory spreader at a spread rate of
31 to 33 grams per sq. ft. per double glue line. The assemblies
were set aside in a closed configuration for 15 minutes before
pre-pressing at 150 psi for 4 minutes. After pre-pressing the
panels were hot pressed at 157.degree. C., 175 psi for 3 minutes
and stacked in a hot box overnight before cutting test specimens.
Four panels were pressed for each adhesive mix. APA type test
specimens were cut. After subjecting the test specimens to the APA
vacuum-pressure soak cycle, the specimens were tested while wet by
tension loading to failure in a shear testing machine. The percent
wood failure for each test specimen was determined and recorded
after the test specimens were dried. The average percent wood
failure is presented in the above table.
135. The cyclic urea prepolymer either cooked into the resin or
added to a plywood resin was found to yield acceptable bonding
performance when formulated into an adhesive and applied to veneers
in typical plywood construction. The amount of cyclic urea solids
by weight in the adhesive based upon the total resin solids by
weight was varied between 0 and 18.3% in the constructions
evaluated. Percent wood failures in many were better than the
average wood failure percent of the standard control resin and
adhesive.
Example 4
136. Phenol-formaldehyde Resins Modified with Cyclic Urea
Prepolymer and Use in Laminates
137. The following Table 4 provides four phenol-formaldehyde resins
prepared for evaluation with the cyclic urea prepolymer
(extender).
5 TABLE 4 A B C D Phenol 2000 2110 1944 1724 50% Formaldehyde
Solution 1793 2317 2384 2769 50% Sodium Hydroxide Solution 25 73 67
60 Urea 50 42 39 35 Distillate -786 -890 -1031 -1225 Methanol 466
420 450 450 18% Hydrochloric Acid 20 0 0 0 Yield 3568 4073 3853
3811 Cook Temperature (.degree. C.) 92 82 82 82 Cook Time (min) 105
175 155 152 % Solids 66.0 68.8 69.7 69.5 Viscosity (cps) 220 405
540 730 % Water Content 10.5 10.1 10.5 9.8 pH 7.5 8.6 8.6 8.5 %
Free Phenol 8.0 3.9 2.5 1.0
138. Phenol and 50% formaldehyde were loaded into a 5 liter lab
reactor equipped with a reflux condenser and a vacuum system. 50%
sodium hydroxide catalyst was loaded. The mixture was heated to the
cook temperature at approx. 1.degree. C./min rate. The mixture was
cooked at that cook temperature for the specified time. Vacuum was
applied and the mixture was cooled to 50.degree. C. Urea was
loaded. The mixture was distilled at 50.degree. C. to an end point
that allowed the water content of the final resin to be achieved.
Methanol was loaded. The pH was adjusted with 18% hydrochloric acid
as necessary.
139. Resin A was a typical resin (control) used in the laminating
industry. Resins B-D are higher formaldehyde to phenol (F:P) mole
ratio resins that typically can not be used to produce good quality
laminates because they cure too fast to a higher degree of cure.
One test to measure cure rate (and degree of cure) is called the
"Stroke Cure Test." A small sample (1/2 cc) of resin is applied to
a hot plate held at a constant temperature. It is stoked with a
small laboratory type spatula to a specified end point. In the
samples, the hot plate was maintained at a temperature of
155.degree. C. and the end point was the "disappearance of strings"
when the sample was stroked with the spatula.
140. The following samples (Table 5) show the effect of the
addition of the cyclic urea prepolymer extender on stroke cure:
6 TABLE 5 Stroke Cure Sample Resin % UF (sec) a A 0 53 b A 5 58 c A
10 79 d A 20 83 e A 40 103 f B 0 45 g B 10 45 h B 40 55 i C 0 36 j
C 10 39 k C 40 49 l D 0 33 m D 10 37 n D 40 43
141. The pH of the neat phenol-formaldehyde resin also has an
effect the stroke cure results. In the following samples (Table 6),
the resin pH was adjusted with 18% hydrochloric acid. The effects
on Stroke Cure are shown:
7TABLE 6 Stroke Cure Sample Resin pH % UF (sec) o B 100% 7.5 0 51 p
B 90% 7.5 10 55 q B 60% 7.5 40 70 r B 100% 6.5 0 65 s B 90% 6.5 10
61 t B 60% 6.5 40 85 u C 100% 7.0 0 53 v C 90% 7.0 10 53 w C 60%
7.0 40 64
142. In some cases the Stroke Cure did not change much at the low,
10% level of cyclic urea prepolymer while at the higher levels the
effects are significant, especially when used in combination with
pH.
143. The major benefit is the allowance of higher F:P mole ratio
phenol-formaldehyde resins to be utilized to manufacture laminates
without the drawback of fast Stroke Cures leading to increased
degree of cure and brittleness of the laminates. Additional
benefits are reduced free phenol levels in the base resin as well
as still lower levels in the combined PF/cyclic urea prepolymer
system (due to dilution).
Example 5
144. Preparation of Phenol-Formaldehyde Abrasive Binders
145. A standard phenol-formaldehyde abrasive binder (2515 g) was
heated to 55.degree. C. Cyclic urea prepolymer (252 g-10% of total
mixture) was added. The temperature was held at 55.degree. C. for
30 minutes and then cooled to room temperature. The process was
repeated with 1475 g standard phenol-formaldehyde abrasive binder
and 118 g (20% of total mixture) cyclic urea prepolymer.
8TABLE 7 Resin with 10% Resin with 20% Initial cyclic urea cyclic
urea Properties Resin prepolymer prepolymer % Non Volatile 55.3
54.1 54.4 Brookfield Viscosity, cps 140 144 170 % Free HCHO 0.48
0.37 0.40 % Free Phenol 0.84 0.70 0.79 121.degree. C. Gel Time
(min.) 11.9 12.2 13.4 150.degree. C. Hot Plate Cure 34 36 35 Time
(sec.) Water Durability 1800 700 485
Example 6
146. Preparation of Novolac Coated Foundry Sand Binder
147. Two sand preparations were prepared. In each, 3000 g of sand
was heated to 175.degree. C. Then 105 g of standard foundry
phenol-formaldehyde resin flake was added and mixed for one minute.
Then 15.8 g of hexamine and 75 ml H.sub.2O or 22 g of cyclic urea
prepolymer and 75 ml H.sub.2O, was added and the mixture was mixed
until doughy. Cooling air was added until a free flowing sand
mixture was obtained.
9 TABLE 8 Properties Hexamine Cyclic Urea Prepolymer Melting Point
90.degree. C. 93.degree. C. 3' Hot Tensile 200-210 psi 30-40 psi 3'
Cold Tensile 400-410 psi 360-370 psi
148. The cyclic urea prepolymer sand is free flowing without
sticking together which is similar to hexamine. The hot tensile is
low, but can be raised with a suitable cure accelerator.
Example 7
149. Preparation of Phenol-formaldehyde Resin and Use in Oriented
Strand Board (OSB)
150. A modified cyclic urea prepolymer (Mod-CUP) was prepared with
73.5% cyclic urea prepolymer and 23% formaldehyde (50% solution).
The pH was adjusted to 9.5 with 0.5% NaOH (50%). The mixture was
heated to 90.degree. C., held for 30 minutes and then cooled to
25.degree. C. Phenol-formaldehyde resins were then prepared as
follows (Table 9):
10 TABLE 9 10% 20% Cyclic Urea: (percent) (percent) 1. Phenol 23.0
21.3 2. Water 21.6 16.6 3. NaOH (50%) 2.9 2.9 4. H2CO (50% 34.4
31.1 5. NaOH (50%) 8.1 8.1 6. Mod-CUP 10.0 20.0
151. Phenol and Mod-CUP were combined. Water and first addition of
caustic were added and the mixture was heated to 49.degree. C.
Formaldehyde was added over a 30 minute period maintaining the
temperature below 85.degree. C. The mixture was allowed to
exotherm. After exotherm was complete, the mixture was heated to
90.degree. C. and reacted to a Gardner Holt viscosity of B to C.
The mixture was then cooled to 75.degree. C. and the reaction was
continued to a Gardner Holt viscosity of R. A second addition of
caustic was added while the temperature was maintained at
76.degree. C. The mixture was cooled to 63.degree. C. and the
reaction was continued to a Gardner Holt viscosity of J to K. The
mixture was then cooled 25.degree. C.
152. Panels were prepared using sweet gum furnish at a mat moisture
content of 6.3-6.5%. The panel manufacturing conditions were as
follows (Table 10):
11 TABLE 10 Furnish Sweet gum Dimensions 16 .times. 16 .times.
{fraction (7/16)} inches Wax 1% on OD wood Resin 2% on OD wood
Press Temperature 400.degree. F. Press Time Fifteen second series
Mat Moisture 6.3-6.5% Target Density 43 pcf
153. Panels were tested for internal bond strength (IB) and boiled
internal bond strength (BIB). Results are shown below. Powder
properties are in Table II.
154. The board surfaces of the set made with 10% cyclic urea were
the tightest after the 2-hour boil/dry cycle, followed by the
control and the 20% level. Addition of cyclic urea at the 10% level
did not appear to have a significant impact on IB/BIB, with the
exception of IB at the longest press time. The boards made with 20%
cyclic urea were not durable and exhibited lower IB values.
12TABLE 11 Average Panel Density 3.25 3.50 3.75 Resin (pcf) (mins.)
(mins.) (mins.) Control 41.9 40.3 (2.7) 42.6 (3.7) 55.2 (7.0) 10%
cyclic urea 42.6 41.3 (1.6) 36.5 (2.2) 43.5 (5.0) 20% cyclic urea
42.9 35.4 (0.6) 26.8 (0.1) 46.1 (0.1)
155.
13TABLE 12 Stroke Cure Fusion Diameter Moisture Bulk Density Powder
(secs.) (mm) (%) (pcf) Control 13 41.7 2.58 31.7 10% cyclic urea 13
39.8 2.42 28.3 20% cyclic urea 17 40.3 2.77 30.5
Example 8
156. Preparation of Melamine-Formaldehyde Resins and Combination
with Clay
157. Melamine (26 parts) was reacted with formaldehyde (28 parts,
50% solution) in the presence of caustic soda catalyst (0.1 part,
50% solution) and 5.9 parts water. The mixture had a pH 9.2 and was
heated at 90.degree. C. until it turned water-clear. Then, 40 parts
of cyclic urea (50% solution) was added and heated further until
the resin was insoluble in an ice-water sure. The mire was cooled
to 80.degree. C. and reacted further until the water tolerance was
1.8 parts water to 1.0 part resin at 25.degree. C. (the resin turns
cloudy when the indicated ratio of water is mixed at 25.degree. C).
Then, the resin was cooled and the final pH was adjusted to 10.
158. Resin-clay coating mixes were prepared with 4 parts clay and 1
part resin in a 55% solids aqueous mixture. These mixes were then
catalyzed with the appropriate amount of ammonium sulfate to yield
the catalyzed resin-clay slurries. Dynamic mechanical analysis
(DMA) cure data for the resin ay mixes and corresponding cured
moduli are listed in Table 13.
14TABLE 13 DMA Results for a Series of UFP-Extended % UP Cure Time
@ 140.degree. C., min Cured Modulus @ 140.degree. C., Kpsi 0 4.3
1267 10 4.9 1210 10* 3.2 1290 All resins were 60% solid and had an
F:M = 1.7. *F:M = 2.0
159. Thermal analysis results are listed in Table 14 for each
resin-clay coating mix. The thermogravameteric analysis (TGA)
samples were catalyzed with the appropriate amount of a lactic acid
solution to produce a fully cured material and heated to
200.degree. C. at a 10.degree. C. per minute heating rate.
15TABLE 14 % Prepolymer Resin Type F/M Solids % Wt loss from
25-200.degree. C. MF 2.2 20 2.64 MF 2.2 0 3.73 UF -- 0 5.94 UP
Solution -- 50 6.08 All resins were 60% solid and had an F:M =
2.2.
Example 9
160. Preparation of Melamine-Formaldehyde Resins
161. A melamine-formaldehyde resin was prepared by reacting 24
parts melamine crystal with 25 parts formaldehyde (50% solution) in
the presence of 0.1 part caustic soda catalyst (50% solution) 3.7
parts sugar, and 7.1 parts water. The mixture had a pH 9.2 and was
heated at 90.degree. C. until it turned water-clear. Then, 40 parts
of the cyclic urea prepolymer (50% solution) was added and heated
further until the resin was insoluble in an ice-water mixture. The
mixture was cooled to 80.degree. C. and reacted further until the
water tolerance was 1.8 parts water to 1 part resin at 25.degree.
C. (the resin turns cloudy when the indicated ratio of water is
mixed at 25.degree. C). The resin was cooled, the final pH was
adjusted to 10. Then, 4.5 parts of diethylene glycol and 3 parts
water were cold blended into the resin.
Example 10
162. Use of Melamine-Formaldehyde Resins in Overlay Paper
Laminates
163. 1) Preparation of Laminates: Decorative sheets (blueberry
pattern, basis weight 90 g/m.sup.2) were treated with the various
resins to 52% resin and 7% volatile contents. The sheets were
pressed onto 4".times.4" particle board substrates 163.degree.
C./300 psi for varying press times.
164. 2) HCl Test for Degree of Cure of the Melamine Laminate
Surface: The cure rate of a series of low pressure laminates was
determined by exposing the surface of the laminate to 2-3 drops of
4 N HCl covered with a micro cover glass for 20 minutes. Exactly
after 20 minutes of contact, the cover was removed and the surface
wiped with a wet tissue followed by a dry tissue. The area was
allowed to dry for 5 minutes, and then, the surface conditions were
evaluated based on the following scale:
HCl Test Scale
165. 1--No effect to very slight effect (over-cured)
166. 2--Very slight loss of surface gloss (slightly over-cured)
167. 3--Moderate loss of gloss without obvious exposure of paper
fibers (properly cured)
168. 3.5--Further loss of gloss without obvious exposure of paper
fibers
169. 4--Apparent loss of gloss with moderate exposure of paper
fibers (under-cured)
170. 5--Badly attached surface with excessive swelling of paper
fibers (very under-cured)
171. 3) Steam Test for Degree of Cure of Melamine Laminate Surface:
The surface of the LP Laminate series was exposed to direct steam
for a controlled time to determine the degree of cure. The
appearance of a white area after exposure to steam was evidence of
an under-cured surface.
172. 4) Crack Resistance Test of Melamine Panel Surface (LPL): The
crack resistance of the series of low pressure laminates was
determined by placing the laminates in a chamber at 20% RH and
25.degree. C. for 3 weeks. The number of days the Laminate resists
cracking is recorded with a description of the cracked surface,
i.e., number, type, and size of cracks.
173. The ability to incorporate cyclic urea prepolymer into
melamine-formaldehyde resins was investigated by cold blending 4.2%
diethylene glycol (DEG) into MF resins prepared in accordance with
Example 6 to form Resins A and B. Both resins had a FM of 2.2;
however, Resin A contained 5% cyclic urea prepolymer while Resin B
contained 20% of the final 60% solid resin. The physical properties
of the two blends were compared to that of a control resin. (Table
14)
174. The control resin was prepared in the same manner as Resins A
and B but without the addition of cyclic urea prepolymer. Melamine
(37.4 parts melamine crystal) was reacted with formaldehyde (30.3
parts, 50% solution) in the presence of caustic soda catalyst (0.01
part, 50% solution), 4.2 parts DEG, 3.2 parts sugar, and 24.9 parts
water. The mixture had a pH of 9.2 and was heated at 95.degree. C.
until it turned water-clear and was insoluble in an ice-water
mixture. Then, it was cooled to 85.degree. C. and reacted further
until the water tolerance was 1.8 parts water to 1.0 part resin at
25.degree. C. (The resin turns cloudy when the indicated ratio of
water is mixed at 25.degree. C.) Then, the resin was cooled and the
final pH adjusted to 10.
175. The properties of the two blends were very similar to the
control resin except for gel times. The catalyzed gel time
increased with increasing % cyclic urea prepolymer extension.
Comparable cure speeds were established by increasing the catalyst
level to 3% and 4.5% for Resins A and B, respectively. In addition,
the water tolerances for the various resins were different due to
the age of the samples.
16TABLE 15 Final Properties Control Resin A Resin B Appearance
clear clear clear RI 1.4866 1.4767 1.4706 pH @ 25.degree. C. 10.0
9.7 9.7 viscosity, cP 39.4 67.5 57.9 % Solids; 105.degree. C. for 3
h 60.8 58.7 57.5 1.6% Cycat 4045 4.5 min 8.03 min 12.55 min 3.0%
Cycat 4045 -- 4.88 min -- 4.5% Cycat 4045 -- -- 4.89 min H.sub.2O
Tolerance @ 25.degree. C. 180% 86% 104%
176. The laminates were exposed to 1 drop of 4N HCl for 20 min in
order to determine the minimum cure conditions. The results are
reported in Table 16. Based on the 4N HCl cure test, both Resins A
and B have a comparable cure behavior to the control. The cure
conditions were also probed by exposing the LP laminates to steam
for a controlled time. Under these conditions, samples pressed for
0.5 min failed the 4 and 8 min exposure tests. However, all other
samples (press times.gtoreq.2 minutes) passed the steam test for at
least 8 min regardless of resin composition.
17TABLE 16 % Steam Sample Press Time Prepolymer Exposure Resin F/M
Solids Time 0.5 min 2 min 5 min Control 1.7 0 2 min P P P 4 min F P
P 8 min F P P (HCl Test) 3.5 3 2 Resin A 2.2 5 2 min P P P 4 min F
P P 8 min F P P (HCl Test) 3.5 3 2 Resin B 2.2 10 2 min P P P 4 min
F P P 8 min F P P (HCl Test) 3.5 3 2 P = pass F = fail
177. An additional test for surface crack resistance of each panel
was also performed by exposing the laminates to 20% RH at room
temperature. After 21 days of exposure, all LP Laminate panels
remained crack free.
178. It will be understood that while the invention has been
described in conjunction with specific embodiments thereof, the
foregoing description and examples are intended to illustrate, but
not limit the scope of the invention. Other aspects, advantages and
modifications will be apparent to those skilled in the art to which
the invention pertains, and these aspects and modifications are
within the scope of the invention, which is limited only by the
appended claims.
* * * * *