U.S. patent application number 11/873419 was filed with the patent office on 2008-05-15 for method of stabilizing resorcinol resins and gel compositions made therefrom.
This patent application is currently assigned to INDSPEC CHEMICAL CORPORATION. Invention is credited to Theodore Harvey Dailey.
Application Number | 20080112876 11/873419 |
Document ID | / |
Family ID | 39712562 |
Filed Date | 2008-05-15 |
United States Patent
Application |
20080112876 |
Kind Code |
A1 |
Dailey; Theodore Harvey |
May 15, 2008 |
Method of Stabilizing Resorcinol Resins and Gel Compositions Made
Therefrom
Abstract
A method of stabilizing a resorcinol-aldehyde resin comprises
heating a resorcinol-aldehyde resin in the substantial absence of
an acid or base catalyst at a temperature from about 130.degree. C.
to about 180.degree. C. for a sufficient amount of time to render
the resin stable in an aqueous solution, wherein the
resorcinol-aldehyde resin prior to heating is a novolak resin. The
stabilized resins have many useful applications. For example, they
can be used to make aerogels and xerogels. They also can be used to
make dipping solutions to improve the adhesion between rubber and
tire cords in a tire, belt, or hose.
Inventors: |
Dailey; Theodore Harvey;
(Kittanning, PA) |
Correspondence
Address: |
BENJAMIN BAI;JONES DAY/INDSPEC CHEMICAL COMPANY
717 TEXAS AVENUE, SUITE 3300
HOUSTON
TX
77002-2712
US
|
Assignee: |
INDSPEC CHEMICAL
CORPORATION
PITTSBURGH
US
|
Family ID: |
39712562 |
Appl. No.: |
11/873419 |
Filed: |
October 17, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60865106 |
Nov 9, 2006 |
|
|
|
Current U.S.
Class: |
423/445R ;
528/153; 528/155; 528/165; 528/503 |
Current CPC
Class: |
B01J 20/28047 20130101;
B01J 20/291 20130101; C04B 2235/48 20130101; C08G 8/22 20130101;
C08L 21/00 20130101; C08L 61/12 20130101; C08L 21/00 20130101; C08L
2666/16 20130101; C04B 35/524 20130101; C08J 2205/026 20130101;
B01J 20/3242 20130101 |
Class at
Publication: |
423/445.R ;
528/153; 528/155; 528/165; 528/503 |
International
Class: |
C08G 8/10 20060101
C08G008/10; C01B 31/02 20060101 C01B031/02; C08F 6/06 20060101
C08F006/06 |
Claims
1. A method of stabilizing a resorcinol-aldehyde resin, comprising:
heating a resorcinol-aldehyde resin in the substantial absence of
an acid or base catalyst at a temperature from about 130.degree. C.
to about 180.degree. C. for a sufficient amount of time to render
the resorcinol-aldehyde resin stable in an aqueous solution,
wherein the resorcinol-aldehyde resin prior to the heating is a
novolak resin.
2. The method of claim 1, wherein the resorcinol-aldehyde resin is
at least partially soluble in water.
3. The method of claim 1, wherein the resorcinol-aldehyde resin is
obtainable by reacting a resorcinol compound with an aldehyde
compound.
4. The method of claim 3, wherein the resorcinol compound is
represented by formula (I): ##STR00007## where each of R.sup.1 and
R.sup.2 is independently H, OH, C.sub.1-5 alkyl, or OR.sup.3 where
R.sup.3 is a C.sub.1-5 alkyl or C.sub.1-5 aryl, and that at least
one of R.sup.1 and R.sup.2 is OH.
5. The method of claim 3, wherein the aldehyde compound is
formaldehyde, methyl formcel, acetaldehyde, propionaldehyde,
butyraldehyde, crotanaldehyde, cinnamaldehyde, benzaldehyde,
furfural, acetone, methyl ethyl ketone, or a mixture thereof.
6. The method of claim 3, wherein the aldehyde compound is
formaldehyde.
7. The method of claim 3, wherein the resorcinol compound is
unsubstituted resorcinol and the aldehyde compound is
formaldehyde.
8. The method of claim 3, wherein the molar ratio of the resorcinol
compound to the aldehyde compound is about 1:0.3 to about
1:0.7.
9. The method of claim 3, wherein the molar ratio of the resorcinol
compound to the aldehyde compound is about 1:0.45 to about
1:0.65.
10. The method of claim 1, wherein the resorcinol-aldehyde resin is
obtainable by reacting a resorcinol compound with an aldehyde
compound in the presence of an acid or base catalyst, and the acid
or base catalyst is substantially removed or neutralized before
heating the resorcinol-aldehyde resin.
11. The method of claim 3, wherein volatiles present in the
reaction mixture are substantially removed before heating the
resorcinol-aldehyde resin.
12. The method of claim 11, wherein an aqueous solvent is added to
the resorcinol-aldehyde resin after heating to make a stabilized
solution of the resorcinol-aldehyde resin.
13. The method of claim 3, wherein an aqueous solvent in the
reaction mixture is not removed before heating the
resorcinol-aldehyde resin.
14. A stabilized resorcinol-aldehyde aqueous solution obtainable by
a method comprising heating a resorcinol-aldehyde resin in the
substantial absence of an acid or base catalyst at a temperature
from about 130.degree. C. to about 180.degree. C. for a sufficient
amount of time to render the resorcinol-aldehyde resin stable in an
aqueous solution, wherein the resorcinol-aldehyde resin prior to
the heating is a novolak resin.
15. The stabilized resorcinol-aldehyde aqueous solution of claim
14, wherein the resorcinol-aldehyde resin is obtainable by reacting
a resorcinol compound with an aldehyde compound, and the resorcinol
compound is represented by formula (I): ##STR00008## where each of
R.sup.1 and R.sup.2 is independently H, OH, C.sub.1-5 alkyl, or
OR.sup.3 where R.sup.3 is a C.sub.1-5 alkyl or C.sub.1-5 aryl, and
that at least one of R.sup.1 and R.sup.2 is OH.
16. A dip solution for enhancing the adhesion between fabric or
glass cords and rubber in a tire, hose, or belt comprising the
stabilized resorcinol-aldehyde aqueous solution of claim 14.
17. A gel obtainable from a stabilized resorcinol-aldehyde aqueous
solution, wherein the stabilized resorcinol-aldehyde aqueous
solution is obtainable by a method comprising heating a
resorcinol-aldehyde resin in the substantial absence of an acid or
base catalyst at a temperature from about 130.degree. C. to about
180.degree. C. for a sufficient amount of time to render the
resorcinol-aldehyde resin stable in an aqueous solution, wherein
the resorcinol-aldehyde resin prior to the heating is a novolak
resin.
18. The gel of claim 17, wherein the resorcinol-aldehyde resin is
obtainable by reacting a resorcinol compound with an aldehyde
compound, and the resorcinol compound is represented by formula
(I): ##STR00009## where each of R.sup.1 and R.sup.2 is
independently H, OH, C.sub.1-5 alkyl, or OR.sup.3 where R.sup.3 is
a C.sub.1-5 alkyl or C.sub.1-5 aryl, and that at least one of
R.sup.1 and R.sup.2 is OH.
19. The gel of claim 17, wherein the gel is a
resorcinol-formaldehyde resin gel.
20. The gel of claim 17, wherein the gel is an aerogel or
xerogel.
21. The gel of claim 17, wherein the method further comprises
subsequently adding additional aldehyde and drying the stabilized
resorcinol-aldehyde resin to obtain the gel.
22. A carbon foam obtainable by carbonizing the gel of claim
17.
23. The carbon foam of claim 22, wherein the foam has an average
pore size from about 50 nm to about 200 nm.
24. The carbon foam of claim 22, wherein the foam has a density in
the range of about 35 mg/cc to 100 mg/cc.
25. The carbon foam of claim 22, wherein the foam has an average
pore size from about 2 nm to about 100 nm.
Description
PRIOR RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application Ser. No. 60/865,106, filed Nov. 9, 2006. For purposes
of United States patent practice, the contents of the provisional
application are herein incorporated by reference in their
entirety.
FEDERALLY SPONSORED RESEARCH STATEMENT
[0002] Not applicable.
REFERENCE TO MICROFICHE APPENDIX
[0003] Not applicable.
FIELD OF THE INVENTION
[0004] The invention relates to methods of stabilizing resorcinol
novolak resins. The stabilized resorcinol novolak resins have many
useful applications. For example, they can be used to make dipping
formulations, aerogels, xerogels, etc.
BACKGROUND OF THE INVENTION
[0005] Resorcinol is a known material commonly used in resins,
dyes, adhesives, pharmaceuticals, and other applications. It can be
obtained in a variety of grades and forms, such as crystals,
flakes, pellets, and the like. Resorcinol, in its various forms, is
soluble in water, alcohol, ether, benzene, glycerol and
formaldehyde.
[0006] Resorcinol can be used to synthesize carbon aerogels or
xerogels. Specifically, carbon aerogel can be produced by the
polycondensation of resorcinol and formaldehyde in a slightly basic
medium, followed by supercritical drying and pyrolysis in an inert
atmosphere. Thin electrodes formed from such carbon aerogels may be
used in capacitive deionization applications. Similarly, xerogels
can be made by simple evaporation of solvent from the pore system
of the gel.
[0007] Resorcinol-formaldehyde novolak resin solutions form a paste
unless stabilized. Several methods involving acidic or alkaline
catalysts for stabilization of resorcinol-formaldehyde resins are
known. An acid catalyst combined with heating may be used but may
render the resin corrosive. Pastes do not flow and cannot be
readily used in automatic mixers. Alternatively, high levels of an
alkaline catalyst may be used to keep the materials liquid, but
these catalysts thicken the resin and can result in undesirable
reactions. The presence of high levels of either acidic or alkaline
catalysts in the resins is often undesirable as they can contribute
to faster, sometimes uncontrollable reactions when the resins are
used.
[0008] Therefore, there is a need for a method of stabilizing
resorcinol novolak resins in an aqueous solution substantially free
of an acid or a base catalyst. In some embodiments, such stabilized
resorcinol novolak resins are stable over a relatively long period
of time.
SUMMARY OF THE INVENTION
[0009] In one aspect, the invention provides a method of
stabilizing a resorcinol-aldehyde resin, comprising: heating a
resorcinol-aldehyde resin in the substantial absence of an acid or
base catalyst at a temperature from about 130.degree. C. to about
180.degree. C. for a sufficient amount of time to render the
resorcinol-aldehyde resin stable in an aqueous solution, wherein
the resorcinol-aldehyde resin prior to the heating is a novolak
resin.
[0010] In some embodiments, the resorcinol-aldehyde resin is at
least partially soluble in water. In other embodiments, the
resorcinol-aldehyde resin is obtainable by reacting a resorcinol
compound with an aldehyde compound. In further embodiments, the
resorcinol compound is represented by formula (I):
##STR00001##
where each of R.sup.1 and R.sup.2 is independently H, OH, C.sub.1-5
alkyl, or OR.sup.3 where R.sup.3 is a C.sub.1-5 alkyl or C.sub.1-5
aryl, and that at least one of R.sup.1 and R.sup.2 is OH.
[0011] In some embodiments, the aldehyde compound is formaldehyde,
methyl formcel, acetaldehyde, propionaldehyde, butyraldehyde,
crotanaldehyde, cinnamaldehyde, benzaldehyde, furfural, acetone,
methyl ethyl ketone, or a mixture thereof. In other embodiments,
the aldehyde compound is a mixture of formaldehyde and
butyraldehyde. In other embodiments, the aldehyde compound is
formaldehyde. In some embodiments, the resorcinol compound is
unsubstituted resorcinol and the aldehyde compound is formaldehyde.
In further embodiments, the formaldehyde is a mixture of
formaldehyde and water or an aqueous solvent. In some embodiments,
the solvent is methanol. In other embodiments, the amount of
formaldehyde in the mixture is about 37 wt. %, based on the total
weight of the mixture. In further embodiments, the amount of
formaldehyde in the mixture is about 50 wt. %, based on the total
weight of the mixture.
[0012] In some embodiments, the molar ratio of the resorcinol
compound to the aldehyde compound is about 1:0.3 to about 1:0.7. In
other embodiments, wherein the molar ratio of the resorcinol
compound to the aldehyde compound is about 1:0.45 to about
1:0.65.
[0013] In some embodiments, the resorcinol-aldehyde resin is
obtainable by reacting a resorcinol compound with an aldehyde
compound in the substantial absence an acid or base catalyst. In
other embodiments, the resorcinol-aldehyde resin is obtainable by
reacting a resorcinol compound with an aldehyde compound in the
presence of an acid or base catalyst, and the acid or base catalyst
is substantially removed or neutralized before heating the
resorcinol-aldehyde resin.
[0014] In some embodiments, the volatiles present in the reaction
mixture are substantially removed before heating the
resorcinol-aldehyde resin. In other embodiments, an aqueous solvent
is added to the resorcinol-aldehyde resin after heating to make a
stabilized solution of the resorcinol-aldehyde resin. In some
embodiments the aqueous solvent can be water or a mixture of
water/methanol or water/ethanol or water/isopropanol. In further
embodiments, water or other aqueous solvent in the reaction mixture
is not removed before heating the resorcinol-aldehyde resin. In
further embodiments, the heating is carried out under pressure in a
device such as an autoclave or other reaction vessels capable of
carrying out reactions under pressure.
[0015] In another aspect, the invention provides a stabilized
resorcinol-aldehyde aqueous solution obtainable by a method
comprising heating a resorcinol-aldehyde resin in the substantial
absence of an acid or base catalyst at a temperature from about
130.degree. C. to about 180.degree. C. for a sufficient amount of
time to render the resorcinol-aldehyde resin stable in an aqueous
solution, wherein the resorcinol-aldehyde resin prior to the
heating is a novolak resin.
[0016] In some embodiments, the resorcinol-aldehyde resin is
obtainable by reacting a resorcinol compound with an aldehyde
compound, and the resorcinol compound is represented by formula
(I):
##STR00002##
where each of R.sup.1 and R.sup.2 is independently H, OH, C.sub.1-5
alkyl, or OR.sup.3 where R.sup.3 is a C.sub.1-5 alkyl or C.sub.1-5
aryl, and that at least one of R.sup.1 and R.sup.2 is OH.
[0017] In another aspect, the invention provides a dip solution for
enhancing the adhesion between fabric or glass cords and rubber in
a tire, hose, or belt comprising the stabilized resorcinol-aldehyde
aqueous solution.
[0018] In another aspect, the invention provides a gel obtainable
from a stabilized resorcinol-aldehyde aqueous solution, wherein the
stabilized resorcinol-aldehyde aqueous solution is obtainable by a
method comprising heating a resorcinol-aldehyde resin in the
substantial absence of an acid or base catalyst at a temperature
from about 130.degree. C. to about 180.degree. C. for a sufficient
amount of time to render the resorcinol-aldehyde resin stable in an
aqueous solution, wherein the resorcinol-aldehyde resin prior to
the heating is a novolak resin.
[0019] In some embodiments, the resorcinol-aldehyde resin is
obtainable by reacting a resorcinol compound with an aldehyde
compound, and the resorcinol compound is represented by formula
(I):
##STR00003##
where each of R.sup.1 and R.sup.2 is independently H, OH, C.sub.1-5
alkyl, or OR.sup.3 where R.sup.3 is a C.sub.1-5 alkyl or C.sub.1-5
aryl, and that at least one of R.sup.1 and R.sup.2 is OH.
[0020] In some embodiments, the gel is a resorcinol-formaldehyde
resin gel. In other embodiments, the gel is an aerogel or a
xerogel. In further embodiments, the method further comprises
drying the stabilized resorcinol-aldehyde resin to obtain the gel.
In still further embodiments, the method comprises adding
additional aldehyde and drying the stabilized resorcinol-aldehyde
resin to obtain the gel.
[0021] In another aspect, the invention provides a carbon foam
obtainable by carbonizing the gel. In some embodiments, carbonizing
occurs at a temperature from about 600.degree. C. to about
1200.degree. C. In other embodiments, the foam has an average pore
size from about 50 nm to about 200 nm. In further embodiments, the
foam has a density in the range of about 35 mg/cc to 100 mg/cc. In
other embodiments, the foam has an average pore size from about 2
nm to about 100 nm.
DEFINITIONS
[0022] To facilitate the understanding of the subject matter
disclosed herein, a number of terms, abbreviations or other
shorthand as used herein are defined below. Any term, abbreviation
or shorthand not defined is understood to have the ordinary meaning
used by a skilled artisan contemporaneous with the submission of
this application.
[0023] A composition that is "substantially free" of a compound
refers to a composition which contains less than about 5 wt. %,
less than about 4 wt. %, less than about 3 wt. %, less than about 2
wt. %, less than about 1 wt. %, less than about 0.5 wt. %, less
than about 0.1 wt. %, or less than about 0.01 wt. % of the
compound, based on the total weight of the composition.
[0024] A novolak resin or novolak reaction that is "substantially
free" of a catalyst refers respectively to a novolak resin or
novolak reaction which contains less than about 0.1 moles, less
than about 0.07 moles, less than about 0.05 moles, less than about
0.04 moles, less than about 0.03 moles, or less than about 0.02
moles of the catalyst per mole of phenolic monomer starting
material.
[0025] An acid or a base catalyst is "substantially removed" from
in a novolak resin refers to the amount of the catalyst in the
novolak resin, after the removal, is reduced to less than about 0.1
moles, less than about 0.07 moles, less than about 0.05 moles, less
than about 0.04 moles, less than about 0.03 moles, or less than
about 0.02 moles of the catalyst per mole of phenolic monomer
starting material.
[0026] An acid or a base catalyst is "substantially absent" or its
"substantial absence" in a novolak resin refers to the amount of
the catalyst in the novolak resin is less than about 0.1 moles,
less than about 0.07 moles, less than about 0.05 moles, less than
about 0.04 moles, less than about 0.03 moles, or less than about
0.02 moles of the catalyst per mole of phenolic monomer starting
material.
[0027] "Novolak resin" or "resin" refers to a neat novolak resin or
a solution of the neat novolak resin. In some embodiments, the
novolak resin disclosed herein is a neat novolak resin. In other
embodiments, the novolak resin disclosed herein is a novolak resin
solution comprising the neat novolak resin and a solvent, such as
water, alcohol, or a mixture thereof.
[0028] In the following description, all numbers disclosed herein
are approximate values, regardless whether the word "about" or
"approximate" is used in connection therewith. They may vary by 1
percent, 2 percent, 5 percent, or, sometimes, 10 to 20 percent.
Whenever a numerical range with a lower limit, R.sup.L and an upper
limit, R.sup.U, is disclosed, any number falling within the range
is specifically disclosed. In particular, the following numbers
within the range are specifically disclosed:
R=R.sup.L+k*(R.sup.U-R.sup.L), wherein k is a variable ranging from
1 percent to 100 percent with a 1 percent increment, i.e., k is 1
percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . , 50
percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97
percent, 98 percent, 99 percent, or 100 percent. Moreover, any
numerical range defined by two R numbers as defined in the above is
also specifically disclosed.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0029] Embodiments disclosed herein provide resorcinol-aldehyde
resins stabilized in an aqueous solution, such as water or a
mixture of water with other water-miscible solvent(s). The
stabilized resins have many useful applications. For example, they
can be used to make aerogels and xerogels. They also can be used to
make dipping solutions to improve the adhesion between rubber and
tire cords in a tire. Various coatings and films can be made from
such resins.
[0030] The method for making a stabilized resorcinol-aldehyde resin
comprises heating a resorcinol-aldehyde resin in the substantial
absence of an acid or base catalyst at a temperature from about
130.degree. C. to about 180.degree. C. for a sufficient amount of
time to render the resin stable in an aqueous solution. In some
embodiments, the resorcinol-aldehyde resin used is a novolak resin
which is limited in the amount of crosslinking and the aldehyde
used to make the novolak resin has almost, if not all, completely
reacted. A novolak resin differs from a resole resin in that a
novolak resin has insufficient aldehyde present to react to form an
infusible solid. A resole resin has sufficient aldehyde crosslinker
present to react to form an infusible or fully-cured state by
application of heat, catalyst or time.
[0031] Synthesis of Resorcinol-Aldehyde Resins
[0032] The resorcinol-aldehyde resins disclosed herein can be
prepared or obtainable by reacting or contacting a resorcinol
compound (as defined below) with at least an aldehyde compound (as
defined below). Many different starting materials can be used to
prepare the resorcinol-aldehyde resins, so long as the resulting
resins are at least partially soluble in water. By "at least
partially soluble in water", it is meant that the resins should
dissolve in water by at least 0.5% by weight. In some embodiments,
the resins should dissolve in water by at least 1 wt. %, at least 2
wt. %, at least 3 wt. %, at least 4 wt. %, or at least 5 wt. %,
based on the total weight of water solution.
[0033] Suitable resorcinol compounds can be represented by, but are
not limited to, formula (I)
##STR00004##
wherein each of R.sup.1 and R.sup.2 is independently H, OH,
NH.sub.2, alkyl, or OR.sup.3 where R.sup.3 is alkyl or aryl; and at
least one of R.sup.1 and R.sup.2 is OH. In some embodiments, the
alkyl or aryl group contains one to five carbon atoms per group.
The above formula (I) encompasses various polyhydroxybenzenes, such
as di- and tri-hydroxybenzenes. Examples of suitable resorcinol
compounds include, but are not limited to, resorcinol
(1,3-dihydroxybenzene), catechol (1,2-dihydroxybenzene),
hydroquinone (1,4-dihydroxybenzene), and phloroglucinol
(1,3,5-trihydroxybenzene). Other suitable resorcinol compounds
include, but are not limited to, pyrogallol, 5-methylresorcinol,
5-ethylresorcinol, 5-propylresorcinol, 2-methylresorcinol,
4-methylresorcinol, 4-ethylresorcinol, and 4-propylresorcinol.
Suitable substituted resorcinol compounds include, but are not
limited to, alkyl substituted resorcinol, aralkyl substituted
resorcinol, or a combination of both. Examples of suitable
resorcinol derivatives are disclosed in U.S. Pat. Nos. 4,892,908;
4,605,696; 4,889,891; and 5,021,522, which are incorporated by
reference herein in their entirety.
[0034] Any aldehyde that reacts with the resorcinol compounds can
be used to prepare the resorcinol-aldehyde resins disclosed herein,
so long as the resulting resins are at least partially water
soluble. In some embodiments, the aldehyde may be represented by
formula (II):
R.sup.4--CH.dbd.O (II)
wherein R.sup.4 is H, alkyl, alkenyl, substituted alkyl such as
aralkyl, aryl, or substituted aryl such as alkaryl. The alkyl can
be C.sub.1-5 alkyl such as methyl, ethyl, propyl, isopropyl, butyl,
isobutyl, pentyl, and the like. In some embodiments, the aldehyde
is formaldehyde. Often times, a 37% formaldehyde solution in water
and methanol is used. The term "formaldehyde" as used herein also
encompasses any substance that can split off or release
formaldehyde, such as paraformaldehyde and trioxane. Aldehydes can
be used alone or a mixture with an aqueous solvent, such as water
or alcohols.
[0035] In some embodiments, the aldehyde can be an alkyl aldehyde
such as n-butyraldehyde, isobutyraldehyde, valeraldehyde, and
combinations thereof. In further embodiments, the aldehyde can be a
formaldehyde, an alkyl aldehyde or a combination thereof. When a
mixture of aldehydes is used, they can be added to the reaction
mixture individually, simultaneously or sequentially.
[0036] In addition to formula (II), suitable aldehydes can also
include certain unsaturated aliphatic aldehyde compounds and
dialdehyde compounds.
[0037] Suitable unsaturated aliphatic aldehyde compounds are
generally represented by formula (III):
##STR00005##
wherein R', R'', and R''' are individually a hydrogen or
hydrocarbyl group. The hydrocarbyl group can be straight or
branched. For example, each of R', R'', and R''' individually can
be --H, --CH.sub.3, --C.sub.2H.sub.5, --C.sub.3H.sub.7,
--C.sub.4H.sub.9, --C.sub.5H.sub.11, or --C.sub.6H.sub.13. In some
embodiments, R''' is hydrogen or a straight or branched
C.sub.1-C.sub.5 alkyl. Some non-limiting examples of unsaturated
aliphatic aldehyde compounds include, but are not limited to,
crotonaldehyde, acrolein, and methacrolein.
[0038] Suitable aliphatic dialdehyde compounds are generally
represented by formula (IV):
##STR00006##
wherein n is equal to 1 or greater. In some embodiments, n is 1, 2,
3, 4, 5, 6, 7, 8, 9, or 10. In other embodiments, n is 1, 2, 3, 4,
or 5. Some non-limiting examples of aliphatic dialdehyde compounds
include, but are not limited to, malonaldehyde, succinaldehyde,
glutaraldehyde, and adipaldehyde.
[0039] The condensation reaction between the aldehyde compound and
the resorcinol compound can be carried out in the substantial
absence of a catalyst at a temperature from about 40.degree. C. to
about 140.degree. C. and under atmospheric pressure. Reaction
conditions for such condensation reactions have been disclosed in
U.S. Pat. Nos. 4,132,693, 2,128,635, and 3,437,122, which are
incorporated by reference herein in their entirety. Conditions
disclosed therein can be used with or without modifications in
various embodiments disclosed herein.
[0040] Although the condensation reaction generally can proceed
readily substantially free of a catalyst when using formaldehyde
and other lower molecular weight aldehydes, a catalyst may be
desirable when some of the higher molecular weight aldehydes are
used. Any acidic or basic catalyst known in the art suitable for
the condensation reaction of phenolic compounds with aldehydes can
be used. Some non-limiting examples of suitable catalysts are
disclosed in A. Gardziella, L. A. Pilato, and A. Knop, "Phenolic
Resins: Chemistry, Applications, Standardization, Safety and
Ecology," 2.sup.nd Edition, Springer-Verlag, New York, Chapter 2,
pp. 24-79 (1999), which is incorporated herein by reference. If a
catalyst is used, it is substantially removed or neutralized before
heating the resulting resins.
[0041] Generally, the molar ratio of the resorcinol compound to the
aldehyde compound can be from about 1:0.2 to about 1:0.8. In some
embodiments, the molar ratio is from about 1:0.3 to about 1:0.65,
from about 1:0.35 to about 1:0.55, from about 1:0.3 to about 1:0.6,
from about 1:0.3 to about 1:0.7, or from 1:0.45 to about 1:0.65. In
some embodiments, the at least an aldehyde comprises formaldehyde
and a second aldehyde. The molar ratio of the second aldehyde to
formaldehyde can vary from about 0.25:1 to about 3:1. In some
embodiments, the molar ratio is from about 0.35:1 to about 2.5:1;
from about 0.5:1 to about 2:1; from about 0.6:1 to about 1.8:1;
from about 0.7:1 to about 1.7:1, from about 0.8:1 to about 1.6:1;
from about 0.9:1 to about 1.5:1; or from about 1:1 to about
1.2:1.
[0042] In other embodiments, resorcinol and formaldehyde undergo a
condensation reaction at a molar ratio of 1 mole of resorcinol to
0.3 to 0.6 mole of the total aldehyde (i.e. formaldehyde and alkyl
aldehyde) at about 100.degree. C. The condensation reaction product
can then be dehydrated at atmospheric pressure or under vacuum at
about 140.degree. C. or a lower temperature. The neat resin
obtained from this process can be used in the subsequent heat
treatment (to be described below). Alternatively, commercial
resorcinol-aldehyde resins also can be used instead as a starting
material for heat treatment. In still other embodiments, the resin
is not dehydrated, and the resin solution is used in the subsequent
heat treatment.
[0043] As mentioned above, resorcinol-aldehyde novolak resins are
used. Generally, the novolak resins are not fully cross-linked.
Therefore, it is desirable that the molar ratio of aldehyde to
phenolic compound is less than about 1 to prevent cross-linking
and/or gelation during manufacture. The novolak resins typically
comprise no methylol functionality, have number average molecular
weights (M.sub.n) in the range of from about 125 to about 5000, and
display glass transition temperatures in the range of from about
45.degree. C. to about 100.degree. C. In some embodiments, the
M.sub.n is between about 125 and about 800 or between about 800 and
about 1500.
[0044] Heat Treatment
[0045] Once a resorcinol-aldehyde resin is made, the resin can be
subject to heat treatment at an elevated temperature for a
sufficient period of time to render the resin stable in an aqueous
solution. By "stable in an aqueous solution", it is meant that the
solution with the resin dissolved therein does not substantially
thicken or form a paste as it would had it not been stabilized with
an acid catalyst. One way to quantify the stability in an aqueous
solution is by the increase in its viscosity over the first ten day
period, with the day zero being the day when the resin is
stabilized. Typically, the viscosity increase over the first ten
day period is no more than about 50%. In some embodiments, the
viscosity increase is no more than about 40%, no more than about
30%, no more than about 20%, or no more than about 15%. In some
embodiments, the viscosity increase is no more than about 10% or no
more than about 5%. In other embodiments, there is no substantially
viscosity increase over the first ten day period.
[0046] The heat treatment can last from a few hours to several
days. In some embodiments, it lasts from about 3 hours to about 20
hours. In other embodiments, it lasts from about 4 hours to about 6
hours, from about 4 hours to about 8 hours, from about 5 hours to
about 7 hours, or from about 4 hours to about 7 hours. In some
embodiments, the temperature ranges from about 130.degree. C. to
about 180.degree. C. In other embodiments, the temperature ranges
from about 140.degree. C. to about 170.degree. C., from about
145.degree. C. to about 165.degree. C., from about 150.degree. C.
to about 160.degree. C., from about 145.degree. C. to about
160.degree. C., from about 140.degree. C. to about 160.degree. C.,
or from about 145.degree. C. to about 160.degree. C. In some
embodiments, the heat treatment is carried out around 145.degree.
C., around 147.degree. C., around 150.degree. C., around
153.degree. C., around 155.degree. C., around 158.degree. C.,
around 160.degree. C., or around 170.degree. C.
[0047] The resin under the heat treatment can either be in molten
form or in solution form. In some embodiments, it is in an aqueous
solution. If the resin is in molten form, the heat treatment can be
conducted in an open reactor or an enclosed reactor with or without
the presence of an inert atmosphere. If the resin is in solution
form, a reaction vessel capable of operating under pressure such as
an autoclave or a similar reactor is used for heat treatment at an
elevated temperature.
[0048] The heat treatment can be carried out in the substantial
absence of an acid or base catalyst. However, depending on the
end-use, a small amount of catalyst may be tolerated. Generally, a
catalyst should be present in the neat resin or resin solution in
an amount of less than 1 wt. % or less than 0.5 wt. %, based on the
total weight of the neat resin or of the resin solution
respectively. In some embodiments, a catalyst is present in an
amount of less than 0.2 wt. %, less than 0.1 wt. %, less than 0.05
wt. %, or less than 0.01 wt. %, based on the total weight of the
neat resin or of the resin solution respectively. In other
embodiments, a catalyst is present in an amount of less than 300
ppm, 200 ppm, 150 ppm, 70 ppm, 50 ppm, 30 ppm, or 15 ppm, based on
the total weight of the neat resin or of the resin solution
respectively. It should be noted that while, in some embodiments,
an acid or base catalyst is substantially absent in making a
novolak resin, it does not mean the resulting neat resin or resin
solution is neutral with a pH around 7. In fact, the resulting neat
resin or an aqueous solution thereof is generally acidic, with a pH
in the range from about 3 to about 5.
[0049] If a resin is made with an acid or base catalyst, the
catalyst can be substantially removed or neutralized prior to heat
treatment. As described above, a resorcinol-aldehyde resin can be
made subtantially free of an acid or base catalyst. In such a case,
no catalyst removal or neutralization is necessary. After the heat
treatment, an aqueous solution, such as water, is added to the
resin (if it is in molten form) to a desired concentration. If the
resin is heat-treated in aqueous form, there may not be a need for
adding additional aqueous solvent. However, aqueous solvent
addition or distillation may be performed to adjust to a target
concentration.
[0050] Applications
[0051] As mentioned above, the stabilized resorcinol formaldehyde
resins have many useful applications. In some embodiments, they can
be used to make aerogels, xerogels, etc. In other embodiments, they
can be used to make dipping solutions to enhance the adhesion
between rubber and tire cords in tires. In further embodiments,
they can be used to make various coatings and films.
[0052] Aerogels and Xerogels
[0053] Xerogels are made by simple evaporation (usually with
heating) of solvent from the pore system of the gel. These gels
usually are denser and have lower porosity than aerogels. Aerogels
can be prepared in a manner similar to that for preparing xerogels.
However, in the preparation of aerogels, the solvent can be driven
off by using supercritical extraction/drying, freeze drying, or
similar methods.
[0054] Aerogels have a variety of useful properties. In particular,
aerogels are known for their superior insulation properties. These
materials have minimal environmental impact since they are
air-filled. Furthermore, they are not easily degraded with the
passage of time. Aerogels are a singular category of ultra fine
(pore sizes in the nanometer range) cell size, low density,
open-celled foams. Aerogels have continuous porosity and their
microstructure with pore sizes below the mean free path of air is
believed to be responsible for their remarkable thermal
properties.
[0055] Organic aerogels have been made from resorcinol-formaldehyde
resins. For example, U.S. Pat. Nos. 4,997,804 and 4,873,218, which
are incorporated by reference herein in their entirety, disclose
polyhydroxybenzene-formaldehyde aerogels. The methods disclosed
therein can be used to prepare aerogels in various embodiments
disclosed herein, except a base catalyst is not used in the initial
synthesis of the resorcinol-formaldehyde novolak or if used, it is
substantially removed or neutralized before heat treatment,
although a small amount of base catalyst should be added along with
additional formaldehyde during the following formation of the gel.
The gel formed in various embodiments can be placed in dilute acid
to increase the crosslinking density of the gel. The gel can then
be exchanged into an organic solvent that is appropriate for
supercritical drying, after which it is supercritically dried. That
is, the pore liquid is removed by supercritical drying (i.e., the
solvent is removed in its supercritical state) at pressures from
about 4 MPa to about 22 MPa, depending on the solvent used.
Freeze-drying has also been used; but the resulting aerogels have
only been obtained as powders. These aerogels may be further
carbonized to yield carbon foams of low densities and ultra-fine
cell sizes.
[0056] Aerogels can also be prepared without using supercritical
drying or freeze drying techniques. Such a method is disclosed in
U.S. Pat. No. 6,288,132, which is incorporated by reference in its
entirety. Silylated organic resorcinol-aldehyde gels can be
prepared by a method comprising: (a) preparing gel comprising a
resorcinol-aldehyde resin; (b) removing substantially all water
from the gel; (c) extracting the gel with a solvent in which a
silylating agent is soluble; (d) treating the gel with the
silylation agent; and (e) drying the treated gel.
[0057] In the above method, substantially all of the water is
removed from the gel by extraction with a first solvent, which can
be either a protic solvent (e.g., an alcohol) or an aprotic solvent
(e.g., hexane, acetone or tetrahydrofuran). If the silylating agent
of choice is not soluble in the first solvent, then a second
solvent in which the silylating agent is soluble (for example,
acetone, toluene or tetrahydrofuran) can be used to further extract
the gel to remove the first solvent. The extracted gel can then be
silylated by stirring the gel in a solution of the first, second,
or a third solvent, for example, hexane and a silylating agent. The
molar ratio of silylating agent:recorcinol-aldehyde gel can be
between from about 0.1:1 to about 2:1, or from about 0.1:1 to about
1.5:1.
[0058] Suitable silylating agents include, but are not limited to,
organosilanes, organosilylamines, and organosilazanes. Examples of
suitable silanes include, but are not limited to,
chlorotrimethylsilane (CH.sub.3).sub.3SiCl), dichlorodimethylsilane
((CH.sub.3).sub.2SiCl.sub.2), bromochlorodimethylsilane
((CH.sub.3).sub.2SiBrCl), chlorotriethylsilane
((C.sub.2H.sub.5).sub.3SiCl) and chlorodimethylphenylsilane
((CH.sub.3).sub.2Si(C.sub.6H.sub.5)Cl). Examples of suitable
silazanes include 1,2-diethyldisilazane
(C.sub.2H.sub.5SiH.sub.2NHSiH.sub.2C.sub.2H.sub.5),
1,1,2,2-tetramethyldisilazane
((CH.sub.3).sub.2SiHNHSiH(CH.sub.3).sub.2),
1,1,1,2,2,2-hexamethyldisilazane
((CH.sub.3).sub.3SiNHSi(CH.sub.3).sub.3),
1,1,2,2-tetraethyldisilazane
(C.sub.2H.sub.5).sub.2SiHNHSiH(C.sub.2H.sub.5).sub.2 and
1,2-diisopropyldisilazane
((CH.sub.3).sub.2CHSiH.sub.2NHSiH.sub.2CH(CH.sub.3).sub.2).
[0059] Some non-limiting examples of silylating agents include, but
are not limited to, silazanes, N,O-bis(trimethylsilyl)-acetamide
(CH.sub.3C(OSi(CH.sub.3).sub.3).dbd.NSi(CH.sub.3).sub.3 and
N,O-bis(trimethylsilyl)-trifluoroacetamide
(CF.sub.3C(OSi(CH.sub.3).sub.3).dbd.NSi(CH.sub.3).sub.3).
[0060] The process can be performed at ambient pressure conditions.
Treating the gel with the silylating agent can be performed at from
ambient temperature to solvent reflux temperature. The gel can be
separated from the solvent, washed with a solvent, and then dried
at a temperature of from ambient temperature to about 130.degree.
C. The silylated organic gel made by this process comprises from
about 0.01% to about 25% by weight silicon.
[0061] The xerogels can be produced by drying the gel at ambient or
elevated temperature conditions, without addition of a solvent. In
some embodiments, xerogels can substitute directly for aerogels. In
other embodiments, xerogels can be manufactured from the same
stabilized resorcinol formaldehyde novolak resin disclosed
herein.
[0062] The aerogels produced in various embodiments disclosed
herein may be carbonized by heating them at temperatures in the
range of about 600.degree. C. to about 1200.degree. C., in a
nitrogen atmosphere, to yield carbon foams of very low densities
and ultra-fine cell size or microcellular structure. Such
resorcinol-aldehyde carbon foams exhibit a variety of densities
from about 35 mg/cc to about 100 mg/cc. The carbon foams were
transparent, red in color and showed an openly porous structure
with cell sizes of less than 0.1 microns.
[0063] In some embodiments, the carbon foams disclosed herein have
an average pore size from about 50 nm to about 200 nm, from about
25 nm to about 175 nm, from about 10 nm to about 150 nm or from
about 2 nm to about 100 nm.
[0064] Some alkaline metal salts, such as lithium, sodium,
potassium, ammonium salts, of various dihydroxy benzoic acids, for
example, 2,4-dihydroxybenzoic acid, may also be incorporated into
the foam matrix during synthesis. After the polymerization, other
metal ions and metal salts, such as lead acetate, rubidium
carbonate, thallium acetate and the like, may also be incorporated
into the crosslinked network. These modified gels may be acidified
with a suitable acid, such as chloracetic acid to expose the
original carboxyl groups, for the incorporation of metal ions or
other cations. Other functional groups or moieties may also be
attached to the gel, as desired, for use in ion exchange reactions,
such as the removal of contaminant metal species from waste water
and the like or as chromatographic separation media. Carbon foams
formed by the carbonization of the aerogels may be further used as
structural parts where X-ray opacity may be a requirement and as
electrode materials as taught in U.S. Pat. Nos. 5,977,015 and
6,737,455, which are incorporated by reference in their
entirety.
[0065] Dipping Formulations
[0066] The stabilized resorcinol-aldehyde resins disclosed herein
can also be used to prepare various dipping formulations, such as
those for treating rubber reinforcing materials. In some
embodiments, the dipping formulation comprises the stabilized
resorcinol-aldehyde resin without a latex. In other embodiments,
the dipping formulation is a single dipping (i.e., single step) or
double dipping (i.e., double step) formulation further comprising a
resorcinol-formaldehyde-latex (RFL) for various industrial
applications. For example, either the single- or double-dipping RFL
formulation can be used to treat rubber reinforcing materials used
in rubber compositions. Any rubber reinforcing material known in
the art can be used, including, but not limited to, polyesters,
polyamides (e.g., nylons and aramid), polyvinyl alcohol, carbon,
glass, polybenzoxazole, rayon, and other organic or inorganic
compositions. These rubber reinforcing materials may be in the form
of filaments, fibers, cords, or fabrics.
[0067] Polyester fibers, yarns, filaments, cords or fabric coated
with the dipping formulations comprising the stabilized
resorcinol-aldehyde resin disclosed herein can be used in the
manufacture of radial, bias, or belted-bias passenger tires, truck
tires, motorcycle or bicycle tires, off-the-road tires, airplane
tires, transmission belts, V-belts, conveyer belts, hose, and
gaskets.
[0068] Other Uses
[0069] In addition to their use as ingredients in fabric dipping
formulations, the stabilized resorcinol-aldehyde resins disclosed
herein can used to make coatings, films, etc. The resins can be
functionalized for various purposes. The functionalized stabilized
resorcinol-aldehyde resin may contain useful functional groups,
such as hydroxyl, carboxyl, amine, epoxy, that may be used for
other applications, such as coatings and composites.
[0070] The following examples are presented to exemplify
embodiments disclosed herein. All numerical values are approximate,
even though the word "about" or "approximate" is not used. When
numerical ranges are given, it should be understood that
embodiments outside the stated ranges may still fall within the
scope disclosed herein. Specific details described in each example
should not be construed as necessary features of the invention.
EXAMPLES
[0071] In the following examples, various resorcinol formaldehyde
resins were prepared and stabilized according to the following
procedures. The reaction and stabilization conditions are set forth
in Table 1 below.
[0072] Step 1. To a reaction flask fitted with a stirrer, a
condenser and a heating mantle, resorcinol was added according to
Table 1 for each example, heated until molten, and stirred.
[0073] Step 2. The piping was set for reflux and cooling water was
applied to the condenser. At 110.degree. C. to 140.degree. C.,
formaldehyde was added from a dropping funnel slowly, at a rate so
as not to overload the condenser during reflux. Typical addition
time was from 1/2 hour to 21/2 hours.
[0074] Step 3. After all formaldehyde had been added, the reaction
flask piping was switched to allow atmospheric distillation. The
reaction mixture was heated to 130.degree. C. while water was
distilled.
[0075] Step 4. At 130.degree. C., the setup was prepared for vacuum
distillation and a vacuum was applied slowly so as not to cause the
resorcinol-formaldehyde resin to surge into overheads or the
condenser. The remaining water was distilled off at a temperature
of 155.degree. C. and 27 to 28 inches of vacuum. The reaction
mixture was held for 15 minutes at those conditions.
[0076] Step 5. The vacuum was released and the reaction mass was
held at 155.degree. C. for the time periods specified in the
table.
[0077] Step 6. When full heat treating time had been achieved, the
mantle set point was lowered to 130.degree. C. The reaction piping
was returned to reflux setup and water was added as per Table 1.
Water was added slowly so resin did not solidify. After about 10%
of the water was added, the set point was lowered gradually while
the water addition continued.
[0078] Step 7. After water had been added, while mixing, the
reaction mass was cooled to 60.degree. C. or lower and methanol was
added slowly. The reaction mixture was mixed thoroughly and
decanted. After the stabilized resin solution was obtained, various
viscosity measurements were made at certain time interval according
to Table 1.
[0079] Viscosity Determination for Resin Solutions Using a
Brookfield Viscometer, Models RV and LV: about 400 g of a resin
solution or liquid resin was placed in a 600 ml beaker and the
temperature was adjusted to 23.0.degree. C.+/-0.1.degree. C. The
viscosity was measured at 10 rpm or 20 rpm with a spindle selected
to place the reading in the 10% to 90% range of the scale. The
machine was allowed to spin for 1 minute then the reading was
recorded. The calculation is as follows:
[0080] Viscosity in centipoises equals the reading on 0-100 scale
times a factor. Viscosity in poises equals the reading on the scale
times the factor, divided by 100. The factor is obtained from the
viscometer tables supplied by Brookfield. It is determined by the
rpm and spindle used.
TABLE-US-00001 TABLE 1 Example No. 1 2 3 4 5 6 7 8 9 10 11
Formaldehyde:Resorcinol 0.50:1 0.50:1 0.50:1 0.50:1 0.50:1 0.35:1
0.65:1 0.65:1 0.35:1 0.65:1 0.35:1 Ratio Hours Held at 4 6 8 18 6 4
4 0 0 9 9 150-160.degree. C. Charge, in g Resorcinol 220.2 220.2
220.2 220.2 220.2 220.2 220.2 220.2 220.2 220.2 220.2 Formaldehyde,
80.7 80.7 80.7 80.7 807.3 56.5 104.9 104.9 56.5 104.9 56.5 37.2 wt.
% Water 59.8 59.8 59.8 59.8 598.5 41.9 77.8 77.8 41.9 77.8 41.9
Methanol 8.9 8.9 8.9 8.9 88.8 6.2 11.5 11.5 6.2 11.5 6.2 Viscosity
(poise) Day 0 9.8 10.5 11.5 12 Day 1 10.8 25.3 paste 4 9.8 Day 2 45
Day 3 4.2 Day 4 12.4 174 Day 5 4 Day 6 12 176.8 Day 7 Precipitate
58.4 14.5 Day 8 12.5 236 Day 9 10 12 Day 10 15.7 Day 11 13.9 Day 13
13.5 13.3 Paste Day 19 10 15.7 Day 20 10 13.6 Day 22 13.6 Day 26
15.9 Day 27 14.2 Day 28 13.6 16.5 Day 29 13.6 13.5 14 Day 31 13.1
Day 33 16.4 Day 34 14 Day 35 14 Day 36 14 13.6 Day 37 16.8 Day 38
16.8 Day 40 16.3 Day 41 14 Day 43 20 13.9 Day 50 24.4 Day 54 16 Day
55 17.3
[0081] In the above examples, the viscosities of some aqueous
solutions of the resorcinol-formaldehyde resins heat-treated
according to embodiments disclosed herein are relatively low and
remain low after a relatively long period of time, such as 30 days.
This suggests that such resorcinol-formaldehyde resins are
stabilized in the aqueous solution. Gel compositions can be made
from such solutions.
[0082] As demonstrated above, embodiments disclosed herein provide
a method of stabilizing resorcinol-aldehyde resins in an aqueous
solution. The stabilized resin solutions can be used to make
dipping formations. The stabilization does not require the use of
an acid or base catalyst, thus making various applications possible
where the presence of an acid or base catalyst cannot be tolerated.
Gel compositions can be made from the stabilized
resorcinol-aldehyde resins. Such gel compositions, in turn, can be
used to make aerogels, xerogels, etc. As a result, new synthetic
routes for such products are provided. The use of stabilized
resorcinol-aldehyde resin solutions in aerogel and xerogel
applications eliminates an early synthesis step which is often
plagued by hard-to-control exothermic or runaway reactions.
[0083] While the invention has been described with respect to a
limited number of embodiments, the specific features of one
embodiment should not be attributed to other embodiments. No single
embodiment is representative of all aspects of the inventions. In
some embodiments, the compositions may include numerous compounds
not mentioned herein. In other embodiments, the compositions do not
include, or are substantially free of, any compounds not enumerated
herein. Variations and modifications from the described embodiments
exist. The method of making and stabilizing the resins is described
as comprising a number of acts or steps. These steps or acts may be
practiced in any sequence or order unless otherwise indicated.
Finally, any number disclosed herein should be construed to mean
approximate, regardless of whether the word "about" or
"approximately" is used in describing the number. The appended
claims intend to cover all those modifications and variations as
falling within the scope of the invention.
* * * * *